1040-5488/13/9012-1424/0 VOL. 90, NO. 12, PP. 1424Y1429 OPTOMETRY AND VISION SCIENCE Copyright * 2013 American Academy of Optometry
ORIGINAL ARTICLE
Prevalence of Presbyopia and Spectacle Coverage in an African Population in Durban, South Africa Kovin Shunmugan Naidoo*, Jyotikumarie Jaggernath†, Carrin Martin‡, Pirindhavellie Govender§, Farai Showman Chinanayi||, Ving Fai Chan**, and Prasidh Ramson†† ABSTRACT Purpose. To assess the prevalence of near vision impairment caused by uncorrected presbyopia and to determine the spectacle coverage for presbyopia in Durban, KwaZulu Natal, South Africa. Methods. A cross-sectional community-based survey was conducted to determine the prevalence of presbyopia in Durban. Eighteen clusters were randomly selected from the suburbs of DurbanVInanda, Ntuzuma, and KwaMashu. Adults over 35 years of age were enumerated through a door-to-door method using aged-based sampling. Respondents were interviewed and then underwent standardized clinical eye examinations. Spectacle coverage was determined. Applying multivariate logistic regressions, the strengths of association of presbyopia and spectacle coverage with the participants’ demographic profile were determined. Results. A total of 2764 participants were enumerated while 1939 (70.2%) were examined with a median age of 52 years (interquartile range 45, 60). The prevalence of presbyopia was 77.0% (95% confidence interval [CI] 74.3%Y79.2%), significantly higher in those 50Y64 years old (OR 10.2, 95% CI 5.3Y19.6) and 65Y79 years old (OR 10.7, 95% CI 3.2Y35.6) and significantly lower in those who had secondary and higher education (p G 0.05). The spectacle coverage for presbyopia was 4.84% (95% CI 3.35%Y6.33%), significantly higher in those who were 65Y79 years old (OR 4.4, 95% CI 1.5Y12.9) and 50Y64 years old (OR 2.6, 95% CI 1.1Y6.1). Conclusions. This study indicated that there is a high prevalence of presbyopia in the study area, with low spectacle coverage, and therefore suggests that uncorrected presbyopia is a major public health concern. The findings of this study may help in making recommendations for strategic planning for eye health intervention efforts. (Optom Vis Sci 2013;90:1424Y1429) Key Words: Durban, presbyopia, South Africa, spectacle coverage, visual impairment
P
resbyopia is a physiological, age-related, irreversible reduction in the eye’s ability to change its focus to see objects that are near, resulting in the need for spectacle correction to assist in near vision-related task.1 The onset of presbyopia generally occurs between the ages of 38 and 48 years, but tends to first be reported between 40 and 45 years.2
*PhD, OD † MA ‡ MSocSci § MOptom, BOptom || MPhil **MSc, BOptom †† BOptom Public Health Division (KS, PG, FSC, VFC, PR), Brien Holden Vision Institute, Durban; and African Vision Research Institute (KS, JJ, CM, PG, FSC), University of KwaZulu-Natal, Durban, KwaZulu-Natal, South Africa.
Globally, it was estimated that in 2005, 517 million people had near vision impairment resulting from not having appropriate near vision correction for presbyopia.3 Uncorrected presbyopia can have a negative impact on a person’s quality of life, particularly affecting the ability to read and write, as well as work-related tasks such as sewing, sorting out stones from grains, and other factory activities or processes.4 This directly impacts on the employment prospects of individuals with potentially significant socioeconomic consequences. Despite the recognized importance of correcting presbyopia, there are only a few reliable studies on its prevalence and near vision spectacle usage in the relevant age groups. A number of presbyopia studies in Africa have been conducted using different methodologies.5Y7 They found that the prevalence of visual impairment due to uncorrected presbyopia in Africa ranges from 46.2% to 52.0%,3,5Y11 with Holden et al estimating it to be 58.9% in 2008.3 A few presbyopia studies have investigated access
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Presbyopia and Spectacle Coverage in DurbanVNaidoo et al.
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to spectacles in developing and developed countries, and have shown that access ranges from 6% to 39% in developing countries and 84% to 96% in developed countries.5Y15,19 The paucity of presbyopia prevalence and spectacle access data in South Africa has served as a barrier to accurately determining the impact of the condition on society, and hindered effective program planning. Despite the availability of eye care services at some public health facilities, the extent of their use with respect to the needs of the populations they serve is unknown. Appropriate data is therefore needed to understand the extent of the problem and to inform interventions aimed at addressing this problem. In light of this lack of data, this study aimed to assess the prevalence of near visual impairment due to uncorrected presbyopia in African adults 35 years and older and to determine the spectacle coverage. This study was part of an international collaboration utilizing a standardized protocol and was conducted in seven sites in India, China (two sites), South Africa, Nepal, Niger, and USA.
lighting, lights were provided by the research team to ensure standardized readings. Local youth were trained to undertake the enumeration and questionnaires, and to invite the relevant persons to participate. They were also trained to assist with components of the eye testing and dispense the spectacles. Reading glasses with the same power for both eyes were provided on site if deemed appropriate. The selection of powers of spectacles provided as ready-mades ranged from +1.00 DS to +5.00 DS. Spectacles were ordered for those needing high power lenses (9+5.00 DS) or with significant anisometropia (difference of sphere equivalent between two eyes 9+0.50 DS). Participants in whom ocular disease was identified (e.g., cataract) were referred to their local eye clinic with a referral letter. Support for the study was secured from the relevant councilors, and community structures were informed of the study. The findings were presented to the councilors and relevant health structures once the study had been completed.
METHODS
Clinical examinations were conducted by optometrists following a standardized protocol. Distance visual acuity (VA) (aided and/or unaided) was measured using a LogMAR ‘‘E’’ Chart (Precision Vision, Villa Park, IL, USA) at 4 m. VA was measured monocularly and then binocularly and recorded using Imperial notation as the smallest line, with at least four out of the five optotypes read correctly. Presenting and uncorrected (without spectacles if presenting with spectacles) near VA was measured using a LogMAR near vision ‘‘E’’ chart (Precision Vision). Near VA was measured binocularly at 40 cm and recorded as the smallest line with at least four out of the five optotypes read correctly. VA less than 20/400 (9LogMAR 1.3) was recorded as near vision blindness. A minimum of three autorefraction readings were taken with the average values for each eye obtained. The refractive error status of the participants with uncorrected VA of 20/40 or worse (QLogMAR 0.3) was determined by static retinoscopy and subjective refraction. Those with near VA worse than 20/40 (9LogMAR 0.3) were tested with ready-made spectacles to obtain the best corrected binocular vision and their vision recorded. The anterior segment and fundus was evaluated with direct ophthalmoscopy. A principal cause of visual impairment was assigned for all eyes with uncorrected visual acuity of 20/40 or worse (QLogMAR 0.3), and the principal cause of blindness was determined for all eyes with uncorrected visual acuity of 20/400 or worse (QLogMAR 1.3).
Study Design A community-based cross-sectional study was conducted in a residential area on the outskirts of Durban, KwaZulu-Natal Province, South Africa in 2010. The three suburbs of Inanda (I), Ntuzuma (N), and KwaMashu (K) were selected within which a corridor was selected that represented the demographic and socioeconomic circumstances of the area, ranging from high-density informal settlements to privately owned residences and scattered peri-urban homesteads. A Geographic Information System was used to select 18 clusters based on the 2001 Enumerator Area census data, using a cluster random sampling approach. For the purposes of sample size determinations, the age categories have been defined as 35Y49, 50Y64, and Q65. Ages 35 to 49 represent the period during which the presbyopic process begins. The increase in prevalence slows during the 50- to 64-year period before leveling off no later than age 65. Anticipated presbyopia prevalence rates for the three age-specific subgroups are on the order of 50, 70, and 80%, respectively. The sample size in each age group were then calculated as
N ¼ ðZÞ 2 ð1:0j PÞðPÞ= ½ðBÞ ðPÞ 2 whereby P is the anticipated prevalence, B is the desired error bound (precision), and Z = 1.96 for a 95% confidence interval. This initial sample size was then multiplied by a design effect factor of 1.5 to compensate for the loss of variation due to multistage cluster sampling and another 10% of the sample size was added to reduce bias due to non-respondents. The study used an age-based sampling approach to identify participants aged 35 years and above, with respondents aged 35Y49 being invited to participate in every household, from 50 to 64 years in every second household, and those 65 years and older in every fourth household. The interviews contained questions on demography, occupation, employment, and spectacle use. Eye testing areas were set up at community halls and schools in close proximity to the study areas, and the residents were identified and invited to participate the day before the clinic was conducted in their area. Where there was inadequate or no
Clinical Examination
Ethical Approval Ethics approval was obtained from the University of KwaZuluNatal’s Biomedical Research Ethics Committee. Informed consent was obtained from the participants. The research protocol adhered to the tenets of the Declaration of Helsinki governing research involving human subjects.
Study Definition and Data Analysis Presbyopia was defined as ‘‘uncorrected, corrected, or best corrected distance VA better than 20/40 (GLogMAR 0.3) with uncorrected near impairment (i.e., worse than 20/40 at 40 cm test
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1426 Presbyopia and Spectacle Coverage in DurbanVNaidoo et al. TABLE 1.
Individuals who were merely enumerated and individuals who were both enumerated and examined Enumerated Age, yr 35Y49 50Y64 65Y79 80 and above Sex Male Female Education None Primary school incomplete Primary school complete Secondary school complete High school and higher Not stated Occupation Housework Agriculture Unskilled Skilled Business Professional Unemployed Others Not stated Total
Enumerated and examined
N
%
N
%
p
541 206 70 8
65.5 25.0 8.5 1
835 777 293 34
43.1 40.1 15.1 1.7
0.000
302 523
36.6 63.4
483 1456
24.9 75.1
0.000
40 227 237 138 107 76
4.9 27.5 28.7 16.7 13.0 9.2
111 645 513 251 144 275
5.7 33.3 26.5 12.9 7.4 14.2
0.000
9 0 21 8 9 11 159 1 607 825
1.1 0 2.5 1.0 1.1 1.2 19.3 0.3 73.5 100
20 9 47 23 7 14 513 5 1301 1939
1.0 0.5 2.4 1.2 0.3 0.7 26.5 0.3 67.1 100
0.000
distance)’’. ‘‘Met need’’ was defined as the number of people who had presbyopia and were corrected while ‘‘unmet need’’ was defined as the number of people who had presbyopia but were uncorrected. Spectacle coverage was a function calculated using the formula {(met need)/[(met need) + (unmet need)]} 100%. Data were entered into database, cleaned and analyzed using STATA 10 (StataCorp LP, College Station, TX, USA). The significance level was fixed at 5%. For categorical data, chi-square and Fisher exact tests were used to determine the statistical significance of the differences in proportion. Multivariate logistic regressions on presbyopia and spectacle coverage (OR with 95% CI) for categories with a p value G0.25 were determined. Age group, gender, and education were used as explanatory variables for the initial model, and were followed by stepwise regression.
RESULTS A total of 2764 individuals were enumerated while 1939 were examined. The response rate was 70.2% (Table 1). The study found that the differences between the respondents and non-respondents were significant in all demographics (p G 0.01). From Table 1, it was observed that those from younger age groups, females, lower education levels, and unemployed showed higher participation rates. The median age of the respondents was 52 years old (interquartile range 45, 60). Three quarters (75%) of the respondents were females.
The prevalence of presbyopia was estimated at 77% (95% confidence interval [CI] 74.3%Y79.2%) with increasing likelihood of the condition with age. The findings indicate that the 35- to 49-year age group was less likely to have presbyopia than the 50- to 65-year-olds (odds ratio [OR] 3.2, 95% CI 2.3Y4.3, p = 0.000) (Table 2). The difference in proportion of presbyopic patients in males and females was not significant (p = 0.105) (Table 2). Those who have not completed primary school were 1.8 times (95% CI 1.2Y2.9) more likely to have presbyopia while those who have completed primary school were 1.6 times (95% CI 1.0Y2.4) more likely to have presbyopia (p G 0.05) as compared to those who have not have any formal education (Table 2). Of the 1939 examined, 72 presented wearing near reading glasses, all of whom were adequately corrected (aided binocular near visual acuity Q20/40). The spectacle coverage for presbyopia was therefore estimated at 4.84% (95% CI 3.35%Y6.33%). Respondents who were 65Y79 years old were most likely to be corrected for presbyopia (OR 5.8, 95% CI 2.3Y14.2) (p = 0.01) followed by those who were 50Y64 years old (OR 2.6, 95% CI 1.2Y5.6) (p = 0.03) (Table 2). There was no statistical significance found in the spectacle coverage between males and females (p = 0.577), and education and occupations (p 9 0.05) (Table 2). From Table 3, it was observed that that there was a positive trend in the addition of ready-made spectacles prescribed to increasing age (p = 0.000, Neyman-Pearson lemma test). More lower addition (+1.00 DS to +1.50 DS) of ready-made spectacles
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Presbyopia and Spectacle Coverage in DurbanVNaidoo et al.
1427
TABLE 2.
Prevalence of presbyopia, spectacle coverage, and history of spectacle wear among participants Presbyopia Age, yr 35Y49 50Y64 65Y79 80 and above Sex Male Female Education None Primary school incomplete Primary school complete Secondary school complete High school and higher Not stated Occupation Housework Agriculture Unskilled Skilled Business Professional Unemployed Others Not stated
Spectacle coverage
N (%)
OR (95% CI)
N (%)
OR (95% CI)
587 (70) 686 (88) 206 (70) 9 (26)
1 3.2 (2.3Y4.3) 1.0 (0.7Y1.4) 0.1 (0.1Y0.3)
14 (2.4) 36 (5.3) 19 (9.2) 3 (33.3)
1 2.6 (1.2Y5.6) 5.8 (2.3Y14.2) 39.9 (7.7Y208.0)
366 (76) 1122 (77)
1 1.2 (0.9Y1.6)
16 (4.4) 56 (5.0)
1 1.3 (0.6Y3.0)
77 (5) 519 (35) 402 (27) 185 (12) 102 (7) 203 (14)
1 1.8 (1.2Y2.9) 1.6 (1.0Y2.4) 1.3 (0.8Y2.1) 1.1 (0.7Y1.7) 1.3 (0.9Y1.9)
2 (2.6) 18 (3.5) 21 (5.2) 5 (2.7) 9 (8.8) 17 (8.4)
1 1.3 (0.3Y6.0) 2.3 (0.4Y11.8) 1.3 (0.2Y10.2) 4.7 (0.9Y25.5) 3.1 (0.5Y19.4)
18 (1) 7 (0.5) 36 (2.5) 19 (1.3) 6 (0.4) 12 (0.8) 384 (25.8) 4 (0.3) 1002 (67.3)
1 0.6 (0.1Y3.1) 0.3 (0.0Y2.0) 0.6 (0.1Y6.9) 0.5 (0.0Y10.7) 0.7 (0.0Y11.6) 0.3 (0.0Y2.5) 0.5 (0.0Y5.6) 0.4 (0.0Y2.7)
0 (0) 0 (0) 2 (5.6) 0 (0) 0 (0) 1 (8.3) 16 (4.2) 0 (0) 53 (5.3)
V V 1 V V 1.7 (0.1Y25.4) 0.5 (0.1Y2.5) V 0.9 (0.2Y4.0)
N indicates the number of people; OR, odds ratio; CI, confidence interval.
were prescribed in those 35 to 49 years old. The medium addition (+1.75 DS to +2.50 DS) was prescribed most to those who were 50 to 60 years old, and those who were 65 years and older were
mainly prescribed with high-addition (9+2.50 DS) ready-made spectacles.
TABLE 3.
Ready-made spectacles prescribed for participants Ready-made spectacles prescribed (DS) +1.00 +1.25 +1.50 +1.75 +2.00 +2.25 +2.50 +2.75 +3.00 +3.25 +3.50 +3.75 +4.00 +4.50 +5.00 Not stated Total
Age groups, yr 35Y49 N (%)
50Y64 N (%)
65Y79 N (%)
80+ N (%)
Total N (%)
145 (24.7) 44 (7.5) 185 (31.5) 40 (6.8) 108 (18.4) 12 (2.0) 18 (3.07) 1 (0.2) 3 (0.5) 0 (0) 1 (0.2) 0 (0) 0 (0) 0 (0) 0 (0) 30(5.11) 587 (100)
9 (1.31) 3 (0.4) 31 (4.5) 12 (1.8) 214 (31.2) 42 (6.1) 225 (32.8) 45 (6.6) 84 (12.2) 5 (0.7) 4 (0.6) 0 (0) 1 (0.2) 0 (0) 0 (0) 11 (1.6) 686 (100)
1 (0.5) 0 (0) 6 (2.9) 1 (0.5) 25 (12.1) 2 (1.0) 43 (20.9) 13 (6.3) 78 (37.9) 11 (5.3) 15 (7.3) 2 (2.0) 3 (1.5) 0 (0) 1 (0.5) 5 (2.4) 206 (100)
0 (0) 0 (0) 2 (22.2) 0 (0) 1 (11.1) 0 (0) 1 (11.1) 0 (0) 2 (22.2) 1 (11.1) 1 (11.1) 0 (0) 0 (0) 1 (11.1) 0 (0) 0 (0) 9 (100)
155 (10.4) 47 (3.2) 224 (15.1) 53 (3.6) 348 (23.4) 56 (3.8) 287 (19.3) 59 (4.0) 167 (11.2) 17 (1.1) 21 (1.4) 2 (0.1) 4 (0.3) 1 (0.1) 1 (0.1) 25 (1.7) 1488(100)
DS indicates diopter sphere; N, number of people. Optometry and Vision Science, Vol. 90, No. 12, December 2013
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1428 Presbyopia and Spectacle Coverage in DurbanVNaidoo et al.
DISCUSSION Presbyopia is generally believed to be a universal age-related condition which will affect all older individuals.16 However, this study demonstrated that prevalence of presbyopia increased from 70% in respondents from the 35- to 49-year age group to 88% in the 50- to 64-year age group, and decreased from 70% in those 65 to 79 years old to 26% in age group 80 years old, with an overall prevalence of 77% in INK. However, due to the small number of respondents in the age group 80 years and older, the reliability of the data in this group is limited. Respondents who were 80 years old and above in the sample were found to be significantly less likely to have presbyopia (OR 0.1, 95% CI 0.1Y0.3) as compared to those who were 35 to 49 years old. This might be due to most participants having developed some form of nuclear sclerosis, causing a myopic shift, which negated the need for near addition. Secondly, senile miosis might have also introduced a pinhole effect, increasing depth of field by up to 0.50 to 1.20 D, thus resulting in the ability to read the 20/40 line.17 Ergonomic factors, such as illumination, were impossible to be standardized in rural outdoor settings and can distort the estimates, a point alluded to by Seranno et al18 and Millodot and Millodot.17 In order to overcome this shortcoming, the clinical examinations were conducted in a community hall to ensure that sufficient illumination was provided for the testings. The questionnaire responses indicated that most of the participants’ daily tasks were outdoor-oriented and hence an outdoor assessment might have presented a more realistic assessment of the presbyopic needs. A presbyopia study conducted in Tanzania found a prevalence of 61.7%, with those over 44 years old ranging from 61.5 to 72.4% with a positive proportionate trend observed.5 That finding was lower than in this study which might be due to the difference in the definition of presbyopia, as Burke defined presbyopia as an improvement of at least one line on a near visual acuity chart with an addition of a plus lens. In Zanzibar, it was observed that 89.4% of the participants were presbyopic.6 A nonrandom sampling clinical case report study in Ghana in participants aged 40 to 85 years estimated the prevalence of presbyopia at 82.1%.19 Differences in participant selection and sampling methodologies could account for the higher prevalence found in Zanzibar and Ghana compared to the INK area. While studies have demonstrated that the prevalence of presbyopia was higher in those with a higher education level,1,5 an inverse relationship was found in this study, the reasons for which are unclear. One possible explanation, although not tested in the present study, is that participants with less education are more exposed to presbyopia-inducing factors such as UV light exposure. In a Kenyan study that investigated functional presbyopia, functional presbyopia was found to be associated in participants with low literacy in rural regions.6 While other studies found a higher prevalence in females5,20,21 this study did not find any statistically significant difference between males and females (p = 0.105). The prevalence of presbyopia indicates the estimated burden for near visual impairment, while spectacle coverage indicates the intervention that is required to treat the condition. The spectacle coverage in INK was relatively low, being estimated at 4.84%
which indicated a low uptake of refractive services. While this study did not explore the barriers to uptake of services, studies that have explored them found that they were mainly due to social stigma, and the cost of spectacles being too high and thus unaffordable.6,22 The participants aged 50 to 79 years had a significantly higher spectacle coverage than those 49 years and younger, as would be expected, being an age-related condition. Persons in this age group were more likely to be engaged in print-related near visual tasks such as reading and writing than those 80 and over, for whom near tasks are more likely involve domestic tasks such as cooking and sewing. In these circumstances, the near vision needs in the younger age groups might be more demanding and prominent than others, thus prompting them to seek treatment. Furthermore, the magnitude of their presbyopia is more difficult to overcome by holding material further out or increasing illumination, unlike in the younger age groups. Presbyopia and programs to address the condition have received little attention despite indications of a relatively high prevalence, the low spectacle usage, and the impact that this has on a significant percentage of working adults. The lack of accessible and affordable eye care facilities in the South African public health care system, as in many developing countries, highlights the need to develop effective infrastructure and systems to ensure that services are provided. The main challenge is training and deploying eye care personnel, developing the appropriate infrastructure, procuring affordable spectacles, overcoming stigma associated with wearing spectacles, and improving access to eye care services for those in need.
ACKNOWLEDGMENTS The authors thank the Fred Hollows Foundation and the World Health Organization for funding the project. Received February 12, 2013; accepted August 30, 2013.
REFERENCES 1. Patel I, West SK. Presbyopia: prevalence, impact, and interventions. Community Eye Health 2007;20:40Y1. 2. Ciuffreda K. Accommodation, the pupil, and presbyopia. In: Benjamin WJ, Borish IM, eds. Borish’s Clinical Refraction. Philadelphia: Saunders; 1998:77Y120. 3. Holden BA, Fricke TR, Ho SM, Wong R, Schlenther G, Cronje S, Burnett A, Papas E, Naidoo KS, Frick KD. Global vision impairment due to uncorrected presbyopia. Arch Ophthalmol 2008;126:1731Y9. 4. Vu HT, Keeffe JE, McCarty CA, Taylor HR. Impact of unilateral and bilateral vision loss on quality of life. Br J Ophthalmol 2005;89:360Y3. 5. Burke AG, Patel I, Munoz B, Kayongoya A, McHiwa W, Schwarzwalder AW, West SK. Population-based study of presbyopia in rural Tanzania. Ophthalmology 2006;113:723Y7. 6. Laviers HR, Omar F, Jecha H, Kassim G, Gilbert C. Presbyopic spectacle coverage, willingness to pay for near correction, and the impact of correcting uncorrected presbyopia in adults in Zanzibar, East Africa. Invest Ophthalmol Vis Sci 2010;51:1234Y41. 7. Sherwin JC, Keeffe JE, Kuper H, Islam FM, Muller A, Mathenge W. Functional presbyopia in a rural Kenyan population: the unmet presbyopic need. Clin Experiment Ophthalmol 2008;36:245Y51.
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Presbyopia and Spectacle Coverage in DurbanVNaidoo et al. 8. Kaimbo K, Maertens K, Missotten L. [Study of presbyopia in Zaire]. Bull Soc Belge Ophtalmol 1987;225(Pt. 2):149Y56. 9. Nwosu SN. Ocular problems of young adults in rural Nigeria. Int Ophthalmol 1998;22:259Y63. 10. Kamali A, Whitworth JA, Ruberantwari A, Mulwanyi F, Acakara M, Dolin P, Johnson G. Causes and prevalence of non-vision impairing ocular conditions among a rural adult population in sw Uganda. Ophthalmic Epidemiol 1999;6:41Y8. 11. Patel I, Munoz B, Burke AG, Kayongoya A, McHiwa W, Schwarzwalder AW, West SK. Impact of presbyopia on quality of life in a rural African setting. Ophthalmology 2006;113:728Y34. 12. Kempen JH, Mitchell P, Lee KE, Tielsch JM, Broman AT, Taylor HR, Ikram MK, Congdon NG, O’Colmain BJ. The prevalence of refractive errors among adults in the United States, Western Europe, and Australia. The Eye Disease Prevalence Research Group. Arch Ophthalmol 2004;122:495Y505. 13. Dandona R, Dandona L, Naduvilath TJ, Srinivas M, McCarty CA, Rao GN. Refractive errors in an urban population in Southern India: the Andhra Pradesh Eye Disease Study. Invest Ophthalmol Vis Sci 1999;40:2810Y8. 14. Taylor HR, Livingston PM, Stanislavsky YL, McCarty CA. Visual impairment in Australia: distance visual acuity, near vision, and visual field findings of the Melbourne Visual Impairment Project. Am J Ophthalmol 1997;123:328Y37. 15. Laitinen A, Koskinen S, Harkanen T, Reunanen A, Laatikainen L, Aromaa A. A nationwide population-based survey on visual acuity, near vision, and self-reported visual function in the adult population in Finland. Ophthalmology 2005;112:2227Y37.
1429
16. Weale RA. Epidemiology of refractive errors and presbyopia. Surv Ophthalmol 2003;48:515Y43. 17. Millodot M, Millodot S. Presbyopia correction and the accommodation in reserve. Ophthalmic Physiol Opt 1989;9:126Y32. 18. Garcia Serrano JL, Lopez Raya R, Mylonopoulos Caripidis T. [Variables related to the first presbyopia correction]. Arch Soc Esp Oftalmol 2002;77:597Y604. 19. Morny FK. Correlation between presbyopia, age and number of births of mothers in the Kumasi area of Ghana. Ophthalmic Physiol Opt 1995;15:463Y6. 20. Duarte WR, Barros AJ, Dias-da-Costa JS, Cattan JM. [Prevalence of near vision deficiency and related factors: a population-based study]. Cad Saude Publica 2003;19:551Y9. 21. Nirmalan PK, Krishnaiah S, Shamanna BR, Rao GN, Thomas R. A population-based assessment of presbyopia in the state of Andhra Pradesh, south India: the Andhra Pradesh Eye Disease Study. Invest Ophthalmol Vis Sci 2006;47:2324Y8. 22. Ramke J, du Toit R, Palagyi A, Brian G, Naduvilath T. Correction of refractive error and presbyopia in Timor-Leste. Br J Ophthalmol 2007;91:860Y6.
Ving Fai Chan 172, Umbilo Road Durban 4001 South Africa e-mail: [email protected]
Optometry and Vision Science, Vol. 90, No. 12, December 2013
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ORIGINAL ARTICLE
Prevalence of Presbyopia and Spectacle Coverage in an African Population in Durban, South Africa Kovin Shunmugan Naidoo*, Jyotikumarie Jaggernath†, Carrin Martin‡, Pirindhavellie Govender§, Farai Showman Chinanayi||, Ving Fai Chan**, and Prasidh Ramson†† ABSTRACT Purpose. To assess the prevalence of near vision impairment caused by uncorrected presbyopia and to determine the spectacle coverage for presbyopia in Durban, KwaZulu Natal, South Africa. Methods. A cross-sectional community-based survey was conducted to determine the prevalence of presbyopia in Durban. Eighteen clusters were randomly selected from the suburbs of DurbanVInanda, Ntuzuma, and KwaMashu. Adults over 35 years of age were enumerated through a door-to-door method using aged-based sampling. Respondents were interviewed and then underwent standardized clinical eye examinations. Spectacle coverage was determined. Applying multivariate logistic regressions, the strengths of association of presbyopia and spectacle coverage with the participants’ demographic profile were determined. Results. A total of 2764 participants were enumerated while 1939 (70.2%) were examined with a median age of 52 years (interquartile range 45, 60). The prevalence of presbyopia was 77.0% (95% confidence interval [CI] 74.3%Y79.2%), significantly higher in those 50Y64 years old (OR 10.2, 95% CI 5.3Y19.6) and 65Y79 years old (OR 10.7, 95% CI 3.2Y35.6) and significantly lower in those who had secondary and higher education (p G 0.05). The spectacle coverage for presbyopia was 4.84% (95% CI 3.35%Y6.33%), significantly higher in those who were 65Y79 years old (OR 4.4, 95% CI 1.5Y12.9) and 50Y64 years old (OR 2.6, 95% CI 1.1Y6.1). Conclusions. This study indicated that there is a high prevalence of presbyopia in the study area, with low spectacle coverage, and therefore suggests that uncorrected presbyopia is a major public health concern. The findings of this study may help in making recommendations for strategic planning for eye health intervention efforts. (Optom Vis Sci 2013;90:1424Y1429) Key Words: Durban, presbyopia, South Africa, spectacle coverage, visual impairment
P
resbyopia is a physiological, age-related, irreversible reduction in the eye’s ability to change its focus to see objects that are near, resulting in the need for spectacle correction to assist in near vision-related task.1 The onset of presbyopia generally occurs between the ages of 38 and 48 years, but tends to first be reported between 40 and 45 years.2
*PhD, OD † MA ‡ MSocSci § MOptom, BOptom || MPhil **MSc, BOptom †† BOptom Public Health Division (KS, PG, FSC, VFC, PR), Brien Holden Vision Institute, Durban; and African Vision Research Institute (KS, JJ, CM, PG, FSC), University of KwaZulu-Natal, Durban, KwaZulu-Natal, South Africa.
Globally, it was estimated that in 2005, 517 million people had near vision impairment resulting from not having appropriate near vision correction for presbyopia.3 Uncorrected presbyopia can have a negative impact on a person’s quality of life, particularly affecting the ability to read and write, as well as work-related tasks such as sewing, sorting out stones from grains, and other factory activities or processes.4 This directly impacts on the employment prospects of individuals with potentially significant socioeconomic consequences. Despite the recognized importance of correcting presbyopia, there are only a few reliable studies on its prevalence and near vision spectacle usage in the relevant age groups. A number of presbyopia studies in Africa have been conducted using different methodologies.5Y7 They found that the prevalence of visual impairment due to uncorrected presbyopia in Africa ranges from 46.2% to 52.0%,3,5Y11 with Holden et al estimating it to be 58.9% in 2008.3 A few presbyopia studies have investigated access
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Presbyopia and Spectacle Coverage in DurbanVNaidoo et al.
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to spectacles in developing and developed countries, and have shown that access ranges from 6% to 39% in developing countries and 84% to 96% in developed countries.5Y15,19 The paucity of presbyopia prevalence and spectacle access data in South Africa has served as a barrier to accurately determining the impact of the condition on society, and hindered effective program planning. Despite the availability of eye care services at some public health facilities, the extent of their use with respect to the needs of the populations they serve is unknown. Appropriate data is therefore needed to understand the extent of the problem and to inform interventions aimed at addressing this problem. In light of this lack of data, this study aimed to assess the prevalence of near visual impairment due to uncorrected presbyopia in African adults 35 years and older and to determine the spectacle coverage. This study was part of an international collaboration utilizing a standardized protocol and was conducted in seven sites in India, China (two sites), South Africa, Nepal, Niger, and USA.
lighting, lights were provided by the research team to ensure standardized readings. Local youth were trained to undertake the enumeration and questionnaires, and to invite the relevant persons to participate. They were also trained to assist with components of the eye testing and dispense the spectacles. Reading glasses with the same power for both eyes were provided on site if deemed appropriate. The selection of powers of spectacles provided as ready-mades ranged from +1.00 DS to +5.00 DS. Spectacles were ordered for those needing high power lenses (9+5.00 DS) or with significant anisometropia (difference of sphere equivalent between two eyes 9+0.50 DS). Participants in whom ocular disease was identified (e.g., cataract) were referred to their local eye clinic with a referral letter. Support for the study was secured from the relevant councilors, and community structures were informed of the study. The findings were presented to the councilors and relevant health structures once the study had been completed.
METHODS
Clinical examinations were conducted by optometrists following a standardized protocol. Distance visual acuity (VA) (aided and/or unaided) was measured using a LogMAR ‘‘E’’ Chart (Precision Vision, Villa Park, IL, USA) at 4 m. VA was measured monocularly and then binocularly and recorded using Imperial notation as the smallest line, with at least four out of the five optotypes read correctly. Presenting and uncorrected (without spectacles if presenting with spectacles) near VA was measured using a LogMAR near vision ‘‘E’’ chart (Precision Vision). Near VA was measured binocularly at 40 cm and recorded as the smallest line with at least four out of the five optotypes read correctly. VA less than 20/400 (9LogMAR 1.3) was recorded as near vision blindness. A minimum of three autorefraction readings were taken with the average values for each eye obtained. The refractive error status of the participants with uncorrected VA of 20/40 or worse (QLogMAR 0.3) was determined by static retinoscopy and subjective refraction. Those with near VA worse than 20/40 (9LogMAR 0.3) were tested with ready-made spectacles to obtain the best corrected binocular vision and their vision recorded. The anterior segment and fundus was evaluated with direct ophthalmoscopy. A principal cause of visual impairment was assigned for all eyes with uncorrected visual acuity of 20/40 or worse (QLogMAR 0.3), and the principal cause of blindness was determined for all eyes with uncorrected visual acuity of 20/400 or worse (QLogMAR 1.3).
Study Design A community-based cross-sectional study was conducted in a residential area on the outskirts of Durban, KwaZulu-Natal Province, South Africa in 2010. The three suburbs of Inanda (I), Ntuzuma (N), and KwaMashu (K) were selected within which a corridor was selected that represented the demographic and socioeconomic circumstances of the area, ranging from high-density informal settlements to privately owned residences and scattered peri-urban homesteads. A Geographic Information System was used to select 18 clusters based on the 2001 Enumerator Area census data, using a cluster random sampling approach. For the purposes of sample size determinations, the age categories have been defined as 35Y49, 50Y64, and Q65. Ages 35 to 49 represent the period during which the presbyopic process begins. The increase in prevalence slows during the 50- to 64-year period before leveling off no later than age 65. Anticipated presbyopia prevalence rates for the three age-specific subgroups are on the order of 50, 70, and 80%, respectively. The sample size in each age group were then calculated as
N ¼ ðZÞ 2 ð1:0j PÞðPÞ= ½ðBÞ ðPÞ 2 whereby P is the anticipated prevalence, B is the desired error bound (precision), and Z = 1.96 for a 95% confidence interval. This initial sample size was then multiplied by a design effect factor of 1.5 to compensate for the loss of variation due to multistage cluster sampling and another 10% of the sample size was added to reduce bias due to non-respondents. The study used an age-based sampling approach to identify participants aged 35 years and above, with respondents aged 35Y49 being invited to participate in every household, from 50 to 64 years in every second household, and those 65 years and older in every fourth household. The interviews contained questions on demography, occupation, employment, and spectacle use. Eye testing areas were set up at community halls and schools in close proximity to the study areas, and the residents were identified and invited to participate the day before the clinic was conducted in their area. Where there was inadequate or no
Clinical Examination
Ethical Approval Ethics approval was obtained from the University of KwaZuluNatal’s Biomedical Research Ethics Committee. Informed consent was obtained from the participants. The research protocol adhered to the tenets of the Declaration of Helsinki governing research involving human subjects.
Study Definition and Data Analysis Presbyopia was defined as ‘‘uncorrected, corrected, or best corrected distance VA better than 20/40 (GLogMAR 0.3) with uncorrected near impairment (i.e., worse than 20/40 at 40 cm test
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1426 Presbyopia and Spectacle Coverage in DurbanVNaidoo et al. TABLE 1.
Individuals who were merely enumerated and individuals who were both enumerated and examined Enumerated Age, yr 35Y49 50Y64 65Y79 80 and above Sex Male Female Education None Primary school incomplete Primary school complete Secondary school complete High school and higher Not stated Occupation Housework Agriculture Unskilled Skilled Business Professional Unemployed Others Not stated Total
Enumerated and examined
N
%
N
%
p
541 206 70 8
65.5 25.0 8.5 1
835 777 293 34
43.1 40.1 15.1 1.7
0.000
302 523
36.6 63.4
483 1456
24.9 75.1
0.000
40 227 237 138 107 76
4.9 27.5 28.7 16.7 13.0 9.2
111 645 513 251 144 275
5.7 33.3 26.5 12.9 7.4 14.2
0.000
9 0 21 8 9 11 159 1 607 825
1.1 0 2.5 1.0 1.1 1.2 19.3 0.3 73.5 100
20 9 47 23 7 14 513 5 1301 1939
1.0 0.5 2.4 1.2 0.3 0.7 26.5 0.3 67.1 100
0.000
distance)’’. ‘‘Met need’’ was defined as the number of people who had presbyopia and were corrected while ‘‘unmet need’’ was defined as the number of people who had presbyopia but were uncorrected. Spectacle coverage was a function calculated using the formula {(met need)/[(met need) + (unmet need)]} 100%. Data were entered into database, cleaned and analyzed using STATA 10 (StataCorp LP, College Station, TX, USA). The significance level was fixed at 5%. For categorical data, chi-square and Fisher exact tests were used to determine the statistical significance of the differences in proportion. Multivariate logistic regressions on presbyopia and spectacle coverage (OR with 95% CI) for categories with a p value G0.25 were determined. Age group, gender, and education were used as explanatory variables for the initial model, and were followed by stepwise regression.
RESULTS A total of 2764 individuals were enumerated while 1939 were examined. The response rate was 70.2% (Table 1). The study found that the differences between the respondents and non-respondents were significant in all demographics (p G 0.01). From Table 1, it was observed that those from younger age groups, females, lower education levels, and unemployed showed higher participation rates. The median age of the respondents was 52 years old (interquartile range 45, 60). Three quarters (75%) of the respondents were females.
The prevalence of presbyopia was estimated at 77% (95% confidence interval [CI] 74.3%Y79.2%) with increasing likelihood of the condition with age. The findings indicate that the 35- to 49-year age group was less likely to have presbyopia than the 50- to 65-year-olds (odds ratio [OR] 3.2, 95% CI 2.3Y4.3, p = 0.000) (Table 2). The difference in proportion of presbyopic patients in males and females was not significant (p = 0.105) (Table 2). Those who have not completed primary school were 1.8 times (95% CI 1.2Y2.9) more likely to have presbyopia while those who have completed primary school were 1.6 times (95% CI 1.0Y2.4) more likely to have presbyopia (p G 0.05) as compared to those who have not have any formal education (Table 2). Of the 1939 examined, 72 presented wearing near reading glasses, all of whom were adequately corrected (aided binocular near visual acuity Q20/40). The spectacle coverage for presbyopia was therefore estimated at 4.84% (95% CI 3.35%Y6.33%). Respondents who were 65Y79 years old were most likely to be corrected for presbyopia (OR 5.8, 95% CI 2.3Y14.2) (p = 0.01) followed by those who were 50Y64 years old (OR 2.6, 95% CI 1.2Y5.6) (p = 0.03) (Table 2). There was no statistical significance found in the spectacle coverage between males and females (p = 0.577), and education and occupations (p 9 0.05) (Table 2). From Table 3, it was observed that that there was a positive trend in the addition of ready-made spectacles prescribed to increasing age (p = 0.000, Neyman-Pearson lemma test). More lower addition (+1.00 DS to +1.50 DS) of ready-made spectacles
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Presbyopia and Spectacle Coverage in DurbanVNaidoo et al.
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TABLE 2.
Prevalence of presbyopia, spectacle coverage, and history of spectacle wear among participants Presbyopia Age, yr 35Y49 50Y64 65Y79 80 and above Sex Male Female Education None Primary school incomplete Primary school complete Secondary school complete High school and higher Not stated Occupation Housework Agriculture Unskilled Skilled Business Professional Unemployed Others Not stated
Spectacle coverage
N (%)
OR (95% CI)
N (%)
OR (95% CI)
587 (70) 686 (88) 206 (70) 9 (26)
1 3.2 (2.3Y4.3) 1.0 (0.7Y1.4) 0.1 (0.1Y0.3)
14 (2.4) 36 (5.3) 19 (9.2) 3 (33.3)
1 2.6 (1.2Y5.6) 5.8 (2.3Y14.2) 39.9 (7.7Y208.0)
366 (76) 1122 (77)
1 1.2 (0.9Y1.6)
16 (4.4) 56 (5.0)
1 1.3 (0.6Y3.0)
77 (5) 519 (35) 402 (27) 185 (12) 102 (7) 203 (14)
1 1.8 (1.2Y2.9) 1.6 (1.0Y2.4) 1.3 (0.8Y2.1) 1.1 (0.7Y1.7) 1.3 (0.9Y1.9)
2 (2.6) 18 (3.5) 21 (5.2) 5 (2.7) 9 (8.8) 17 (8.4)
1 1.3 (0.3Y6.0) 2.3 (0.4Y11.8) 1.3 (0.2Y10.2) 4.7 (0.9Y25.5) 3.1 (0.5Y19.4)
18 (1) 7 (0.5) 36 (2.5) 19 (1.3) 6 (0.4) 12 (0.8) 384 (25.8) 4 (0.3) 1002 (67.3)
1 0.6 (0.1Y3.1) 0.3 (0.0Y2.0) 0.6 (0.1Y6.9) 0.5 (0.0Y10.7) 0.7 (0.0Y11.6) 0.3 (0.0Y2.5) 0.5 (0.0Y5.6) 0.4 (0.0Y2.7)
0 (0) 0 (0) 2 (5.6) 0 (0) 0 (0) 1 (8.3) 16 (4.2) 0 (0) 53 (5.3)
V V 1 V V 1.7 (0.1Y25.4) 0.5 (0.1Y2.5) V 0.9 (0.2Y4.0)
N indicates the number of people; OR, odds ratio; CI, confidence interval.
were prescribed in those 35 to 49 years old. The medium addition (+1.75 DS to +2.50 DS) was prescribed most to those who were 50 to 60 years old, and those who were 65 years and older were
mainly prescribed with high-addition (9+2.50 DS) ready-made spectacles.
TABLE 3.
Ready-made spectacles prescribed for participants Ready-made spectacles prescribed (DS) +1.00 +1.25 +1.50 +1.75 +2.00 +2.25 +2.50 +2.75 +3.00 +3.25 +3.50 +3.75 +4.00 +4.50 +5.00 Not stated Total
Age groups, yr 35Y49 N (%)
50Y64 N (%)
65Y79 N (%)
80+ N (%)
Total N (%)
145 (24.7) 44 (7.5) 185 (31.5) 40 (6.8) 108 (18.4) 12 (2.0) 18 (3.07) 1 (0.2) 3 (0.5) 0 (0) 1 (0.2) 0 (0) 0 (0) 0 (0) 0 (0) 30(5.11) 587 (100)
9 (1.31) 3 (0.4) 31 (4.5) 12 (1.8) 214 (31.2) 42 (6.1) 225 (32.8) 45 (6.6) 84 (12.2) 5 (0.7) 4 (0.6) 0 (0) 1 (0.2) 0 (0) 0 (0) 11 (1.6) 686 (100)
1 (0.5) 0 (0) 6 (2.9) 1 (0.5) 25 (12.1) 2 (1.0) 43 (20.9) 13 (6.3) 78 (37.9) 11 (5.3) 15 (7.3) 2 (2.0) 3 (1.5) 0 (0) 1 (0.5) 5 (2.4) 206 (100)
0 (0) 0 (0) 2 (22.2) 0 (0) 1 (11.1) 0 (0) 1 (11.1) 0 (0) 2 (22.2) 1 (11.1) 1 (11.1) 0 (0) 0 (0) 1 (11.1) 0 (0) 0 (0) 9 (100)
155 (10.4) 47 (3.2) 224 (15.1) 53 (3.6) 348 (23.4) 56 (3.8) 287 (19.3) 59 (4.0) 167 (11.2) 17 (1.1) 21 (1.4) 2 (0.1) 4 (0.3) 1 (0.1) 1 (0.1) 25 (1.7) 1488(100)
DS indicates diopter sphere; N, number of people. Optometry and Vision Science, Vol. 90, No. 12, December 2013
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1428 Presbyopia and Spectacle Coverage in DurbanVNaidoo et al.
DISCUSSION Presbyopia is generally believed to be a universal age-related condition which will affect all older individuals.16 However, this study demonstrated that prevalence of presbyopia increased from 70% in respondents from the 35- to 49-year age group to 88% in the 50- to 64-year age group, and decreased from 70% in those 65 to 79 years old to 26% in age group 80 years old, with an overall prevalence of 77% in INK. However, due to the small number of respondents in the age group 80 years and older, the reliability of the data in this group is limited. Respondents who were 80 years old and above in the sample were found to be significantly less likely to have presbyopia (OR 0.1, 95% CI 0.1Y0.3) as compared to those who were 35 to 49 years old. This might be due to most participants having developed some form of nuclear sclerosis, causing a myopic shift, which negated the need for near addition. Secondly, senile miosis might have also introduced a pinhole effect, increasing depth of field by up to 0.50 to 1.20 D, thus resulting in the ability to read the 20/40 line.17 Ergonomic factors, such as illumination, were impossible to be standardized in rural outdoor settings and can distort the estimates, a point alluded to by Seranno et al18 and Millodot and Millodot.17 In order to overcome this shortcoming, the clinical examinations were conducted in a community hall to ensure that sufficient illumination was provided for the testings. The questionnaire responses indicated that most of the participants’ daily tasks were outdoor-oriented and hence an outdoor assessment might have presented a more realistic assessment of the presbyopic needs. A presbyopia study conducted in Tanzania found a prevalence of 61.7%, with those over 44 years old ranging from 61.5 to 72.4% with a positive proportionate trend observed.5 That finding was lower than in this study which might be due to the difference in the definition of presbyopia, as Burke defined presbyopia as an improvement of at least one line on a near visual acuity chart with an addition of a plus lens. In Zanzibar, it was observed that 89.4% of the participants were presbyopic.6 A nonrandom sampling clinical case report study in Ghana in participants aged 40 to 85 years estimated the prevalence of presbyopia at 82.1%.19 Differences in participant selection and sampling methodologies could account for the higher prevalence found in Zanzibar and Ghana compared to the INK area. While studies have demonstrated that the prevalence of presbyopia was higher in those with a higher education level,1,5 an inverse relationship was found in this study, the reasons for which are unclear. One possible explanation, although not tested in the present study, is that participants with less education are more exposed to presbyopia-inducing factors such as UV light exposure. In a Kenyan study that investigated functional presbyopia, functional presbyopia was found to be associated in participants with low literacy in rural regions.6 While other studies found a higher prevalence in females5,20,21 this study did not find any statistically significant difference between males and females (p = 0.105). The prevalence of presbyopia indicates the estimated burden for near visual impairment, while spectacle coverage indicates the intervention that is required to treat the condition. The spectacle coverage in INK was relatively low, being estimated at 4.84%
which indicated a low uptake of refractive services. While this study did not explore the barriers to uptake of services, studies that have explored them found that they were mainly due to social stigma, and the cost of spectacles being too high and thus unaffordable.6,22 The participants aged 50 to 79 years had a significantly higher spectacle coverage than those 49 years and younger, as would be expected, being an age-related condition. Persons in this age group were more likely to be engaged in print-related near visual tasks such as reading and writing than those 80 and over, for whom near tasks are more likely involve domestic tasks such as cooking and sewing. In these circumstances, the near vision needs in the younger age groups might be more demanding and prominent than others, thus prompting them to seek treatment. Furthermore, the magnitude of their presbyopia is more difficult to overcome by holding material further out or increasing illumination, unlike in the younger age groups. Presbyopia and programs to address the condition have received little attention despite indications of a relatively high prevalence, the low spectacle usage, and the impact that this has on a significant percentage of working adults. The lack of accessible and affordable eye care facilities in the South African public health care system, as in many developing countries, highlights the need to develop effective infrastructure and systems to ensure that services are provided. The main challenge is training and deploying eye care personnel, developing the appropriate infrastructure, procuring affordable spectacles, overcoming stigma associated with wearing spectacles, and improving access to eye care services for those in need.
ACKNOWLEDGMENTS The authors thank the Fred Hollows Foundation and the World Health Organization for funding the project. Received February 12, 2013; accepted August 30, 2013.
REFERENCES 1. Patel I, West SK. Presbyopia: prevalence, impact, and interventions. Community Eye Health 2007;20:40Y1. 2. Ciuffreda K. Accommodation, the pupil, and presbyopia. In: Benjamin WJ, Borish IM, eds. Borish’s Clinical Refraction. Philadelphia: Saunders; 1998:77Y120. 3. Holden BA, Fricke TR, Ho SM, Wong R, Schlenther G, Cronje S, Burnett A, Papas E, Naidoo KS, Frick KD. Global vision impairment due to uncorrected presbyopia. Arch Ophthalmol 2008;126:1731Y9. 4. Vu HT, Keeffe JE, McCarty CA, Taylor HR. Impact of unilateral and bilateral vision loss on quality of life. Br J Ophthalmol 2005;89:360Y3. 5. Burke AG, Patel I, Munoz B, Kayongoya A, McHiwa W, Schwarzwalder AW, West SK. Population-based study of presbyopia in rural Tanzania. Ophthalmology 2006;113:723Y7. 6. Laviers HR, Omar F, Jecha H, Kassim G, Gilbert C. Presbyopic spectacle coverage, willingness to pay for near correction, and the impact of correcting uncorrected presbyopia in adults in Zanzibar, East Africa. Invest Ophthalmol Vis Sci 2010;51:1234Y41. 7. Sherwin JC, Keeffe JE, Kuper H, Islam FM, Muller A, Mathenge W. Functional presbyopia in a rural Kenyan population: the unmet presbyopic need. Clin Experiment Ophthalmol 2008;36:245Y51.
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Presbyopia and Spectacle Coverage in DurbanVNaidoo et al. 8. Kaimbo K, Maertens K, Missotten L. [Study of presbyopia in Zaire]. Bull Soc Belge Ophtalmol 1987;225(Pt. 2):149Y56. 9. Nwosu SN. Ocular problems of young adults in rural Nigeria. Int Ophthalmol 1998;22:259Y63. 10. Kamali A, Whitworth JA, Ruberantwari A, Mulwanyi F, Acakara M, Dolin P, Johnson G. Causes and prevalence of non-vision impairing ocular conditions among a rural adult population in sw Uganda. Ophthalmic Epidemiol 1999;6:41Y8. 11. Patel I, Munoz B, Burke AG, Kayongoya A, McHiwa W, Schwarzwalder AW, West SK. Impact of presbyopia on quality of life in a rural African setting. Ophthalmology 2006;113:728Y34. 12. Kempen JH, Mitchell P, Lee KE, Tielsch JM, Broman AT, Taylor HR, Ikram MK, Congdon NG, O’Colmain BJ. The prevalence of refractive errors among adults in the United States, Western Europe, and Australia. The Eye Disease Prevalence Research Group. Arch Ophthalmol 2004;122:495Y505. 13. Dandona R, Dandona L, Naduvilath TJ, Srinivas M, McCarty CA, Rao GN. Refractive errors in an urban population in Southern India: the Andhra Pradesh Eye Disease Study. Invest Ophthalmol Vis Sci 1999;40:2810Y8. 14. Taylor HR, Livingston PM, Stanislavsky YL, McCarty CA. Visual impairment in Australia: distance visual acuity, near vision, and visual field findings of the Melbourne Visual Impairment Project. Am J Ophthalmol 1997;123:328Y37. 15. Laitinen A, Koskinen S, Harkanen T, Reunanen A, Laatikainen L, Aromaa A. A nationwide population-based survey on visual acuity, near vision, and self-reported visual function in the adult population in Finland. Ophthalmology 2005;112:2227Y37.
1429
16. Weale RA. Epidemiology of refractive errors and presbyopia. Surv Ophthalmol 2003;48:515Y43. 17. Millodot M, Millodot S. Presbyopia correction and the accommodation in reserve. Ophthalmic Physiol Opt 1989;9:126Y32. 18. Garcia Serrano JL, Lopez Raya R, Mylonopoulos Caripidis T. [Variables related to the first presbyopia correction]. Arch Soc Esp Oftalmol 2002;77:597Y604. 19. Morny FK. Correlation between presbyopia, age and number of births of mothers in the Kumasi area of Ghana. Ophthalmic Physiol Opt 1995;15:463Y6. 20. Duarte WR, Barros AJ, Dias-da-Costa JS, Cattan JM. [Prevalence of near vision deficiency and related factors: a population-based study]. Cad Saude Publica 2003;19:551Y9. 21. Nirmalan PK, Krishnaiah S, Shamanna BR, Rao GN, Thomas R. A population-based assessment of presbyopia in the state of Andhra Pradesh, south India: the Andhra Pradesh Eye Disease Study. Invest Ophthalmol Vis Sci 2006;47:2324Y8. 22. Ramke J, du Toit R, Palagyi A, Brian G, Naduvilath T. Correction of refractive error and presbyopia in Timor-Leste. Br J Ophthalmol 2007;91:860Y6.
Ving Fai Chan 172, Umbilo Road Durban 4001 South Africa e-mail: [email protected]
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