PROSPECTIVE EVALUATION OF VISUAL ACUITY AGREEMENT BETWEEN STANDARD EARLY TREATMENT DIABETIC RETINOPATHY STUDY CHART AND A HANDHELD EQUIVALENT IN EYES WITH RETINAL PATHOLOGY EHSAN RAHIMY, MD,* SAHITYA REDDY, BS,* FRANCIS CHAR DECROOS, MD,* M. ALI KHAN, MD,* DAVID S. BOYER, MD,† OMESH P. GUPTA, MD,* CARL D. REGILLO, MD,* JULIA A. HALLER, MD* Purpose: To evaluate the visual acuity agreement between a standard back-illuminated Early Treatment Diabetic Retinopathy Study (ETDRS) chart and a handheld internally illuminated ETDRS chart. Methods: Two-center prospective study. Seventy patients (134 eyes) with retinal pathology were enrolled between October 2012 and August 2013. Visual acuity was measured using both the ETDRS chart and the handheld device by masked independent examiners after best protocol refraction. Examination was performed in the same room under identical illumination and testing conditions. Results: The mean number of letters seen was 63.0 (standard deviation: 19.8 letters) and 61.2 letters (standard deviation: 19.1 letters) for the ETDRS chart and handheld device, respectively. Mean difference per eye between the ETDRS and handheld device was 1.8 letters. A correlation coefficient (r) of 0.95 demonstrated a positive linear correlation between ETDRS chart and handheld device measured acuities. Intraclass correlation coefficient was performed to assess the reproducibility of the measurements made by different observers measuring the same quantity and was calculated to be 0.95 (95% confidence interval: 0.93–0.96). Agreement was independent of retinal disease. Conclusion: The strong correlation between measured visual acuity using the ETDRS and handheld equivalent suggests that they may be used interchangeably, with accurate measurements. Potential benefits of this device include convenience and portability, as well as the ability to assess ETDRS visual acuity without a dedicated testing lane. RETINA 35:1680–1687, 2015

V

practice. Currently, the Snellen eye chart is the most widely used eye chart for determining visual acuity clinically, despite a variety of disadvantages. To address the limitations of Snellen acuity measurement,1–4 the Early Treatment of Diabetic Retinopathy Study (ETDRS) chart was developed5 based on the work of Bailey and Lovie4 and guidelines proposed by the National Academy of Science.6 The ETDRS chart uses 5 letters on each line with standardized spacing, geometric progression from line to line, and 10 letters of equal difficulty using a Sloan7 optotype. Additionally, the charts also use a standardized light box to remove the variable of inconsistent illumination.1 Visual acuity measurements

isual acuity is an outcome of paramount importance in ophthalmic clinical research. Accurate and reproducible measurement of visual function is the sine qua non for most trials and allows comparison among studies, as well as their translation into clinical

From the *Retina Service, Wills Eye Hospital, Philadelphia, Pennsylvania; and †Retina-Vitreous Associates Medical Group, Los Angeles, California. Supported in part by Innovation Grant awarded through Wills Eye Hospital. None of the authors have any conflicting interests to disclose. Reprint requests: Julia A. Haller, MD, Retina Service, Wills Eye Hospital, 840 Walnut Street, Suite 1510, Philadelphia, PA 19107; e-mail: [email protected]

1680

EVALUATION OF HANDHELD ETDRS DEVICE  RAHIMY ET AL

performed with the ETDRS chart have been shown to be highly repeatable.5,8 Because of this precision, the ETDRS is the current gold standard in retinal clinical trials where visual acuity is a study endpoint. Despite the increased reliability of measurements recorded from ETDRS charts, some drawbacks exist. Perhaps, the main limitation is the increased time required to measure vision using an ETDRS chart compared with a Snellen chart. One group reports that in certain patients, ETDRS acuity can take nearly twice as long to perform as Snellen acuity.9 Other barriers to widespread ETDRS utilization include the bulky chart size, physical space requirements for the testing lane, and an unfamiliar scoring system. In 2002, a computerized version of the ETDRS testing protocol, the electronic ETDRS visual acuity (EVA) tester, was developed, which addressed a number of these limitations.10 This system was shown to be comparable with the traditional ETDRS chart while providing some unique advantages over its counterpart. Specifically, the computerized data acquisition allowed for automated scoring and better standardization of the testing procedure, reduced potential bias by limiting the role of the technician in the testing procedure, and offered the ability to test visual acuity from 20/12 to 20/800 at a single distance. The EVA has been implemented by numerous large multicenter initiatives, including the AREDS2, CATT, and the DRCR.net. A novel backlit handheld ETDRS chart (ETDRS Vision Meter, formerly RAM-ETDRS; AMA Optics, Miami Beach, FL) may allow for reproducible acuity measurements at greater convenience to the examiner during clinical studies (Figure 1, A and B). The pocketsized ETDRS device uses the same standardized letter optotype, geometric line progression, and letters of equal difficulty found in the ETDRS chart. Additionally, the device is equipped with an attenuation filter that produces luminance to a standardized brightness (85 cd/m2) to further minimize measurement variation (Figure 1B). This study prospectively compared visual acuity scores obtained with the handheld ETDRS device with vision scores obtained with the standard ETDRS chart to determine the utility of the handheld device for future clinical studies in patients with retinal diseases.

Methods Institutional review board/ethics committee approval was obtained for this two-center prospective study, which was registered on ClinicalTrials.gov (identifier: NCT01622816). Study procedures adhered to the tenets of the Declaration of Helsinki, and research was conducted in accordance with regulations set forth by

1681

Fig. 1. Handheld internally illuminated ETDRS device (A). Side-by-side size comparison with a standard 20-diopter binocular indirect ophthalmoscopy lens (B). Visual acuity in patients with various retinal diseases was measured using the standard ETDRS chart and the handheld device chart by masked independent examiners after best protocol refraction (C).

the Health Insurance Portability and Accountability Act (HIPAA). After informed consent was obtained, 70 patients were enrolled between October 2012 and August 2013 among 2 retina practices (Retina Service, Wills Eye Hospital, Philadelphia, PA, and Retina-Vitreous Associates Medical Group, Los Angeles, CA) who met the following inclusion criteria: aged older than 18 years, clinical diagnosis of retinal disease in at least 1 eye, and visual acuity greater than or equal to 20/800 in the participating study eye(s). Patients with significant cataract (more than 2+ nuclear sclerosis as graded by the examining ophthalmologist), significant posterior capsular opacity in pseudophakic eyes, or active uveitis were excluded to assess only true “retinal acuity.” The primary outcome measured in this trial was agreement between the handheld ETDRS and standard EVA as measured in individual letter units. The following information was also recorded for each patient: age, gender, lens status, and clinical diagnosis.

1682 RETINA, THE JOURNAL OF RETINAL AND VITREOUS DISEASES

Visual Acuity Testing Visual acuity in patients with various retinal diseases was measured using both the ETDRS chart and the handheld ETDRS device by independent examiners after best protocol refraction (Figure 1C). Examiners were masked to the visual acuity score obtained using the alternate testing method. Examination was performed in the same room under identical illumination conditions. An experienced refractionist initially measured an ETDRS protocol acuity5 for both eyes using Charts 1, 2, and R (Lighthouse International, New York, NY). All charts were presented in a floor-mounted light box with a luminance of 85 cd/m2. This luminance was verified using a handheld light meter (Digital Lux Meter, Model: LX1330B; Dr. Meter, Union City, CA). Using the refraction obtained during the standard ETDRS protocol testing, vision was then measured using the handheld ETDRS device during occlusion of the opposite eye. Acuity was first tested using the device at 20 cm after adding +5.00 to the spherical prescription for the 20/200, 20/160, and 20/125 lines. Next, visual acuity was tested using the device at 40 cm after adding +2.50 to the spherical prescription for the 20/100 to 20/16 lines until 4 or more mistakes are made on a single line. The device’s letter score was the sum of letters correctly read at both 20 cm and 40 cm. Study protocol dictated that if fewer than 20 letters were read correctly at the initial testing distances of 20 cm and 40 cm, repeat testing at 5 cm using a +20.00 adjust to the spherical prescription is required. The handheld ETDRS device has a deployable +20.00 lens fixed at 5 cm. After retesting at 5 cm, the final device visual acuity score was calculated by adding the number of letters correctly read at 5 cm to the number of letters correctly read at 20 cm and 40 cm. During testing at 5 cm, if the patient was able to read more than 30 letters when retested, repeat refraction and measurement were performed to ensure that letters of equivalent visual acuity were not counted twice in the final visual acuity score. The rationale for testing visual acuity with the standard ETDRS chart followed by the handheld device was 2-fold. First, by completing standard ETDRS chart assessments before additional testing, we avoided interfering with other studies at our institution for which standard ETDRS acuity was being collected. Second, our study was designed to demonstrate noninferiority of the handheld device against the gold standard measurement, thus we sought to mitigate variables, which could hinder the standard ETDRS chart score. Specifically, we recognized that subject fatigue with consecutive testing may adversely affect



2015  VOLUME 35  NUMBER 8

the second method under evaluation. Hence, the standard ETDRS score may have been negatively impacted, inadvertently improving the handheld device performance in head-to-head comparison, had the alternative testing order been used. Rather, we preferred to test the handheld device follow the standard chart to see if was able to achieve comparable results, despite this potential handicap. Statistical Analysis The study was planned to enroll 130 or more eyes of at least 65 patients based on the following sample size calculation. A sample size of 55 eyes undergoing retesting with a correlation of 0.90 achieves 80% power to detect equivalence between the handheld ETDRS and standard ETDRS charts when the margin of equivalence is from −2.5 to 2.5 letters and the actual expected mean difference is 0 letters. The significance level (alpha) is 0.05 using 2 one-sided paired t-tests. These results are based on 2,000 Monte Carlo samples from the null distribution: normal (mean: 41.8, standard deviation [SD]: 13.6) to normal (mean: 44.3, SD: 13.6) and the alternative distribution: normal (mean: 41.8, SD: 13.6) to normal (mean: 41.8, SD: 13.6). Distributions, SD, and correlation were derived from a previous pilot study. Sample size was determined using nQuery 7.0 (Statistical Solutions, Saugus, MA). Agreement between the handheld ETDRS and standard EVA was quantified with intraclass correlation coefficients with 95% confidence intervals. Bland– Altman plots were used to depict the variability of handheld ETDRS and standard ETDRS measurements. Results A total of 134 eyes from 70 patients were included in the study. Baseline patient demographics and retinal diagnoses are outlined in Table 1. The mean age of participants was 65 years (SD: 15, median: 68, range: 24–93 years). Fifty-three eyes were pseudophakic from previous cataract surgery, whereas the remaining 81 were phakic. Visual acuity assessment by the handheld ETDRS device was compared with that measured by the standard ETDRS chart. The total number of letters read was 8,437 for the standard ETDRS chart versus 8,196 for the handheld ETDRS device. The mean number of letters correctly read per eye with the standard ETDRS chart was 63.0 (SD: 19.8) in comparison with 61.2 (SD: 19.1) using the handheld ETDRS device. The mean difference between the 2 methods was 1.8 more letters (SD: 6.2) read with the standard ETDRS chart per eye than the handheld

1683

EVALUATION OF HANDHELD ETDRS DEVICE  RAHIMY ET AL Table 1. Patient Demographics and Ocular Findings Age, years Mean ± SD Median Range Gender (n = 70) Male Female Lens status (n = 134) Phakic Pseudophakic Retinal diagnosis (n = 134) DME Nonneovascular AMD Neovascular AMD Proliferative DR Nonproliferative DR CSCR Central RVO Stargardt macular dystrophy Branch RVO

65 ± 15 68 24–93 35 (50.0%) 35 (50.0%) 81 (60.4%) 53 (39.6%) 40 39 21 9 6 6 6 4 3

(29.9%) (29.1%) (15.7%) (6.7%) (4.5%) (4.5%) (4.5%) (3.0%) (2.2%)

AMD, age-related macular degeneration; CSCR, central serous chorioretinopathy; DME, diabetic macular edema; DR, diabetic retinopathy; RVO, retinal vein occlusion; SD, standard deviation.

device. Although the mean values were similar, equivalence could not be concluded within the prespecified bounds of ±2.5 letters (equivalence paired t-test, P = 0.13). The distribution of the letter differences between the 2 methods is displayed in Tables 2 and 3 and Figure 2. When participants had both eyes tested (n = 64), the right eyes on average differed by 2.3 more letters read with the standard ETDRS over the handheld device, whereas left eyes differed by 1.4 letters between tests, resulting in a marginal net difference of approximately 0.9 letters between eyes. The Pearson’s product–moment correlation coefficient (r) of 0.95 indicated a strong positive correlation between both modalities (Figure 3). This measured agreement was independent of the underlying retinal disease. Furthermore, intraclass correlation coefficient was calculated to assess the reproducibility of the measurements made by different observers measuring the same quantity. As with the Pearson’s coefficient, the intraclass correlation coefficient (0.95, 95% confidence interval: 0.93–0.96) suggested a high level of correlation. A Bland–Altman analysis (Figure 4) demonstrated differences between acuity scores on the standard ETDRS chart and handheld ETDRS device plotted against their average visual acuity score. Using the mean paired difference (1.8) and coefficient of repeatability (12.1), the limits of agreement containing 95% of differences between measurements was derived (−10.3 to 13.9 letters), indicating a broad within subject variability. However, the difference points are plotted relatively symmetrically above and below the mean

Table 2. Differences Between the ETDRS Chart and Handheld ETDRS Device Absolute Value of Difference in Letters

Number (%)

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 ... 21 22

12 13 24 15 15 10 9 6 4 7 5 4 1 4 2 1

(9.0) (9.7) (17.9) (11.2) (11.2) (7.5) (6.7) (4.5) (3.0) (5.2) (3.7) (3.0) (0.7) (3.0) (1.5) (0.7)

1 (0.7) 1 (0.7)

Cumulative Percentage 9.0 18.7 36.6 47.8 59.0 66.4 73.1 77.6 80.6 85.8 89.6 92.5 93.2 96.3 97.8 98.5 99.3 100.0

paired difference line, demonstrate consistent variability across the graph, and show no discernable trend in level of visual acuity between the differences (y-axis) and the averages (x-axis), confirming the lack of consistent bias throughout the study.

Discussion Visual acuity has long been the gold standard primary endpoint in ophthalmic clinical trials. Standardization of visual acuity protocols in research studies is accordingly crucial.11–14 Under ideal testing conditions, visual acuity measurements are accurate and reproducible without influence from extraneous factors so that only changes related to disease evolution or treatment are measured. However, in the “real world,” vision testing is affected by numerous variables, including ambient lighting in the examination Table 3. LogMAR Differences Between ETDRS Chart and Handheld Device Absolute Value of Difference #0.1 #0.2 #0.3 #0.4 #0.5

logMAR logMAR logMAR logMAR logMAR

Number

Cumulative Percentage

89 120 132 132 134

66.4 89.6 98.5 98.5 100.0

0.1 logMAR = 5 letters; 0.2 logMAR = 10 letters; 0.3 logMAR = 15 letters; 0.4 logMAR = 20 letters; 0.5 logMAR = 25 letters. logMAR, logarithm of the minimal angle of resolution.

1684 RETINA, THE JOURNAL OF RETINAL AND VITREOUS DISEASES

Fig. 2. Distribution of differences between acuity scores on standard ETDRS chart and handheld ETDRS device testing. A positive difference indicates that the standard ETDRS scored higher than the corresponding handheld ETDRS device did.

room, as well as the design of the testing chart selected. Although numerous charts are available for visual acuity assessment, the two most commonly used in both clinical and research settings are the Snellen and ETDRS charts. Despite the U.S. Food and Drug Administration (FDA) requiring ETDRS-measured visual acuities in registration trials and the ETDRS charts having been repeatedly shown to be more accurate with less variability in results,8,10,15–20 the vast majority of published clinical case series in the ophthalmic literature report Snellen acuities.11 This discrepancy is perhaps

Fig. 3. Scatter plot of ETDRS letter scores. For each tested eye, the number of letters read by the standard ETDRS chart (x-axis) is plotted against the number of letters read by the handheld ETDRS device (y-axis). A correlation coefficient (r) of 0.95 indicated a strong positive correlation between the two.



2015  VOLUME 35  NUMBER 8

nowhere more glaring than in retina, where visual acuity scores have been demonstrated to be significantly better on ETDRS charts compared with Snellen charts, with the greatest differences observed in patients having vision ,20/200 (e.g., in eyes with advanced age-related macular degeneration in several studies).15,20 The widespread incorporation of the ETDRS system has not occurred for a number of reasons: testing with this chart is believed to take longer to complete and be more difficult to administer than testing with the Snellen and also requires specialized lanes that may not necessarily be available at a given clinical site.20,21 This makes comparison between studies using Snellen acuity with the larger clinical trials that report on ETDRS acuity problematic. Furthermore, physicians are often presented with clinical trial data showing ETDRS acuity results yet must attempt to translate these findings into their Snellen vision-based clinical practices. With the proliferation of clinical trials and case series investigating treatment options for macular diseases, along with the increasing expectation that clinicians have an objective evidence base for patient care decision making,22 there are clear-cut advantages to a portable device such as the ETDRS Vision Meter, were it able to uniformly assess visual acuity and move with agility between clinical and research platforms. The battery-operated handheld device consists of a high-intensity calibrated light source, a viewing window that isolates 1 of 12 lines of letters, a reading scale displaying 20/16 to 20/800 ETDRS letters, and a recoiling 40-cm cord to easily measure the examining distance. Both standard acuity (corrected visual acuity) and retinal acuity (assessing macular function) can be measured with this instrument, although only

EVALUATION OF HANDHELD ETDRS DEVICE  RAHIMY ET AL

1685

Fig. 4. Bland–Altman plot demonstrating visual acuity measurement discrepancy between the standard ETDRS chart and the handheld ETDRS device. The x-axis displays the mean between the standard ETDRS and the handheld ETDRS letter score (standard ETDRS + handheld ETDRS)/2. The y-axis displays the difference between measurements by both charts (standard ETDRS − handheld ETDRS). All negative value points along the y-axis reflect standard ETDRS score worse than the handheld ETDRS score in the same person and vice versa for positive value points.

the former was tested in this study. For standard acuity, the window brightness is reduced to standard luminance with an attenuation filter and is viewed through a near add only. The retinal acuity option has also been evaluated23,24 and uses the same window viewed at full brightness through a near add and a pinhole clip. Previous versions of the handheld ETDRS device have been noted to accurately predict postprocedure visual acuity in eyes undergoing Nd:YAG laser capsulotomy23 and cataract surgery,24 demonstrating that the agreement between near and distance measurement of acuities is not unprecedented. In the cataract study, subgroup analysis of 21 eyes with comorbid conditions consisting of primarily retinal diseases demonstrated that the handheld chart was also highly predictive of postcataract extraction visual acuity.24 Our study represents the first effort to evaluate the standard acuity testing capability of the handheld ETDRS device in a prospective masked comparison to the gold standard ETDRS chart among a cohort of patients with retinal disease. The strong correlation observed (r = 0.95, intraclass correlation coefficient = 0.95) between the 2 methods suggests that they may be used interchangeably, although we could not conclude that the 2 mean letter scores were equivalent within the fairly strict prespecified bounds of ±2.5 letters. In this study, the handheld ETDRS device underestimated ETDRS vision on average by 1.8 letters per study eye compared with the standard ETDRS chart.

As such, one limitation of our study design may have been the contribution of patient fatigue induced by testing the handheld ETDRS vision after the standard ETDRS chart each time as per study protocol rather than randomizing the order. This may have accounted for some of the variability between measurements. Indeed, when analyzing the distribution of score differences (Table 2 and Figure 2), 2 points (21 and 22 letters) from 2 of the oldest patients enrolled in the study stand apart from the rest of the data. These 2 eyes actually had relatively preserved visual acuity by the standard ETDRS chart, reading 79 and 78 ETDRS letters (Snellen equivalent = 20/30), respectively, yet fell well short of these marks with the handheld device (58 and 56 letters). We attribute both the patients’ ages and having to read a greater number of letters during the initial chart assessment as contributors to subject fatigue and the resulting wide scoring variation during these instances. Alternatively, it has been demonstrated that in patients with certain retinal diseases, notably age-related macular degeneration, near vision can be impaired to a greater extent than distance acuity.25,26 Thus, it is plausible that the 1.8 letter difference may actually be a reflection of the different testing distances. Nevertheless, the overall distribution of score differences between the two modalities seems comparable with previous reported studies. In the aforementioned EVA protocol using the electronic ETDRS, Beck et al10 found that of 265 tested eyes, 196 (74.0%)

1686 RETINA, THE JOURNAL OF RETINAL AND VITREOUS DISEASES

had score differences that fell within 0.1 logarithm of the minimal angle of resolution (logMAR) units (5 ETDRS letters) of each other, 248 (93.6%) within 0.2 logMAR units (10 letters), 261 (98.5%) within 0.3 logMAR units (15 letters), and 262 (98.9%) within 0.4 logMAR units (20 letters). Our study’s corresponding proportions were 66.4%, 89.6%, 98.5%, and 98.5%, respectively (Table 3). These differences may be partly explained by the number of eyes with retinal disease included in each trial. Only 98 eyes (36.9%) had underlying retinal pathology in the study by Beck et al, and of those, only 15 carried a diagnosis of diabetic retinopathy. Additionally, 53 of their study subjects (20%) were considered normal, and the investigators did not separate scores based on whether pathology was present. However, the authors did find that with the electronic ETDRS, variability in testing between methods was greater in patients with poorer visual acuity. In comparison, all of the subject eyes in our study had retinal disease as part of the inclusion criteria, thus were more likely to demonstrate some degree of visual acuity impairment and potentially greater testing variability. Although this was a prospective study, certain other limitations still exist. First, we did not retest patients using the handheld ETDRS device to assess its repeatability and consistency; however, the standard ETDRS system has been shown to be highly reliable, and here, we have demonstrated a high level of agreement with it. Second, the time required to complete each test was not recorded, thus, although it may seem intuitive, we cannot definitely state whether the handheld ETDRS device is actually more time efficient than the standard ETDRS chart. Third, we did not quantitatively assess patients’ subjective evaluations of each test, as we believed more reliable distinctions between categories were needed for this pilot study. In the future, a survey with multiple specific criteria would be useful to extract consistent data for analysis on patients’ experiences. Finally, the full spectrum of diseases a retina specialist routinely encounters is only partially represented here. Notably, absent from the sampled clinical diagnoses, although not part of the study’s exclusion criteria, were patients with previous or current retinal detachment, vitreous opacities (e.g., vitreous hemorrhage), or vitreoretinal interface pathology (vitreomacular traction, epiretinal membrane, macular hole). Even with the included disease categories, a number of them still only have a few patients tested relative to conditions such as diabetic macular edema and age-related macular degeneration, which predominated. The ability of the handheld ETDRS device to accurately reflect the standard ETDRS chart in these conditions is not known and could be



2015  VOLUME 35  NUMBER 8

potentially evaluated in a second follow-up study. Despite these limitations, this study prospectively validates the handheld ETDRS device using masked examiners on a large cohort of eyes with retinal disease. Potential benefits of this handheld portable device include the ability to use one unit in multiple locations, making it an attractive option for retina practices with numerous satellite offices. Additionally, the lack of required examination space enables ease of EVA assessment without a dedicated testing lane. Integration of this device into protocols for FDA-registered clinical trials could potentially expedite a number of cumbersome steps in the process of checking patient’s visual acuities. Currently, the FDA necessitates all acuity testing with ETDRS charts to start at a distance of 4 m. For studies where most patients likely have good visual acuity, this would be considered a reasonable starting distance. Retina studies, however, may enroll patients with poorer baseline visual acuities, for whom this requirement adds considerable time to the visual acuity testing, as the chart has to be tested first at 4 m and then moved forward to 2 m if none of the letters can be read.20 Use of the handheld ETDRS device would obviate the need for these extra steps and potentially save research staff significant time. In summary, although the back-illuminated ETDRS chart is regarded by many as the gold standard method of testing visual acuity in ophthalmology clinical trials, the novel handheld ETDRS device with standard calibrated lighting may fulfill a complementary role, one that enables freedom to test acuity without a designated examination lane and offers economy of using the same equipment in multiple locations. In this study, we observed a strong positive correlation between visual acuity measurements obtained by the standard ETDRS chart and the handheld ETDRS device in patients with retinal pathology. These findings suggest that the portable device may serve as a valuable tool for future use in both retina research and clinical practice settings. Key words: age-related macular degeneration, diabetic macular edema, ETDRS, Snellen, retinal disease, retinal vein occlusion, vision testing, visual acuity. Acknowledgments The authors thank Dr. Ben Leiby of Jefferson Medical College, Philadelphia, PA, for assisting with statistical analysis. References 1. Kniestedt C, Stamper RL. Visual acuity and its measurement. Ophthalmol Clin North Am 2003;16:155–170, v.

EVALUATION OF HANDHELD ETDRS DEVICE  RAHIMY ET AL 2. Pandit JC. Testing acuity of vision in general practice: reaching recommended standard. BMJ 1994;309:1408. 3. Gibson RA, Sanderson HF. Observer variation in ophthalmology. Br J Ophthalmol 1980;64:457–460. 4. Bailey IL, Lovie JE. New design principles for visual acuity letter charts. Am J Optom Physiol Opt 1976;53:740–745. 5. Ferris FL III, Kassoff A, Bresnick GH, Bailey I. New visual acuity charts for clinical research. Am J Ophthalmol 1982;94:91–96. 6. Recommended stardard procedures for the clinical measurement and specification of visual acuity. Report of working group 39. Committee on vision. Assembly of Behavioral and Social Sciences, National Research Council, National Academy of Sciences, Washington, D.C. Adv Ophthalmol 1980; 41:103–148. 7. Sloan LL. New test charts for the measurement of visual acuity at far and near distances. Am J Ophthalmol 1959;48:807–813. 8. Elliott DB, Sheridan M. The use of accurate visual acuity measurements in clinical anti-cataract formulation trials. Ophthalmic Physiol Opt 1988;8:397–401. 9. Rosser DA, Laidlaw DA, Murdoch IE. The development of a “reduced logMAR” visual acuity chart for use in routine clinical practice. Br J Ophthalmol 2001;85:432–436. 10. Beck RW, Moke PS, Turpin AH, et al. A computerized method of visual acuity testing: adaptation of the early treatment of diabetic retinopathy study testing protocol. Am J Ophthalmol 2003;135:194–205. 11. Williams MA, Moutray TN, Jackson AJ. Uniformity of visual acuity measures in published studies. Invest Ophthalmol Vis Sci 2008;49:4321–4327. 12. Dong LM, Marsh MJ, Hawkins BS. Measurement and analysis of visual acuity in multicenter randomized clinical trials in the United States: findings from a survey. Ophthalmic Epidemiol 2003;10:149–165. 13. Ferris FL III, Bailey I. Standardizing the measurement of visual acuity for clinical research studies: guidelines from the Eye Care Technology Forum. Ophthalmology 1996;103:181–182. 14. Moutray TN, Williams MA, Jackson AJ. Change of visual acuity recording methods in clinical studies across the years. Ophthalmologica 2008;222:173–177.

1687

15. Falkenstein IA, Cochran DE, Azen SP, et al. Comparison of visual acuity in macular degeneration patients measured with Snellen and early treatment diabetic retinopathy study charts. Ophthalmology 2008;115:319–323. 16. Lovie-Kitchin JE. Validity and reliability of visual acuity measurements. Ophthalmic Physiol Opt 1988;8:363–370. 17. Camparini M, Cassinari P, Ferrigno L, Macaluso C. ETDRSfast: implementing psychophysical adaptive methods to standardized visual acuity measurement with ETDRS charts. Invest Ophthalmol Vis Sci 2001;42:1226–1231. 18. Blackhurst DW, Maguire MG. Reproducibility of refraction and visual acuity measurement under a standard protocol. The Macular Photocoagulation Study Group. Retina 1989;9: 163–169. 19. Kiser AK, Mladenovich D, Eshraghi F, et al. Reliability and consistency of visual acuity and contrast sensitivity measures in advanced eye disease. Optom Vis Sci 2005;82:946–954. 20. Kaiser PK. Prospective evaluation of visual acuity assessment: a comparison of Snellen versus ETDRS charts in clinical practice (An AOS Thesis). Trans Am Ophthalmol Soc 2009;107: 311–324. 21. Sprague JB, Stock LA, Connett J, Bromberg J. Study of chart designs and optotypes for preschool vision screening–I. Comparability of chart designs. J Pediatr Ophthalmol Strabismus 1989;26:189–197. 22. Bhatt R, Sandramouli S. Evidence-based practice in acute ophthalmology. Eye (Lond) 2007;21:976–983. 23. Hofeldt AJ. Illuminated near card assessment of potential visual acuity. J Cataract Refract Surg 1996;22:367–371. 24. Hofeldt AJ, Weiss MJ. Illuminated near card assessment of potential acuity in eyes with cataract. Ophthalmology 1998; 105:1531–1536. 25. Richter-Mueksch S, Stur M, Stifter E, Radner W. Differences in reading performance of patients with drusen maculopathy and subretinal fibrosis after CNV. Graefes Arch Clin Exp Ophthalmol 2006;244:154–162. 26. Munk M, Kiss C, Huf W, et al. Therapeutic interventions for macular diseases show characteristic effects on near and distance visual function. Retina 2013;33:1915–1922.

PROSPECTIVE EVALUATION OF VISUAL ACUITY AGREEMENT BETWEEN STANDARD EARLY TREATMENT DIABETIC RETINOPATHY STUDY CHART AND A HANDHELD EQUIVALENT IN EYES WITH RETINAL PATHOLOGY.

To evaluate the visual acuity agreement between a standard back-illuminated Early Treatment Diabetic Retinopathy Study (ETDRS) chart and a handheld in...
409KB Sizes 0 Downloads 6 Views