PREVALENCE O F SENILE CATARACT, DIABETIC RETINOPATHY, SENILE MACULAR DEGENERATION, AND OPEN-ANGLE GLAUCOMA IN T H E FRAMINGHAM EYE STUDY M. M. K I N I , M.D.,

H. M. L E I B O W I T Z ,

M.D.,

T. COLTON, SC.D., AND R. J. NlCKERSON, M.A. Boston, Massachusetts J. G A N L E Y ,

M.D.

Bethesda, Maryland AND T. R. D A W B E R ,

M.D.

Boston, Massachusetts

According to the data from the Model Reporting Area, 1 senile cataract, chronic simple glaucoma, senile macular degen­ eration, and diabetic retinopathy are the major causes of adult blindness in the United States today. Few surveys have been designed to study these diseases in the general population. Instead, studies tend to concentrate on eye clinic patients. The representative group of volunteers who have participated in the Framingham Heart Study 2 since 1949 gave us a unique opportunity to determine the prevalence of these major causes of blindness in an elderly population. In im­ plementing this study, we emphasized standardized observations by trained examiners following a detailed protocol.

for participation in the Framingham Eye Study. Detailed descriptions of this study have been published. 3 ' 4 The ocular exam­ ination consisted of two parts. Initially, a preliminary screening examination was performed. This included a short oph­ thalmic history, determination of best corrected visual acuity, applanation tonometry, and after mydriasis, examina­ tion of the lens by slit-lamp biomicroscopy and the macula by direct ophthalmoscopy, as well as measurement of the cup: disk ratio by indirect ophthalmoscopy. Gonioscopic examination was per­ formed if narrow angles were suspected. The second part consisted of a definitive examination, by a senior observer, of those patients with evidence of any of the four diseases under consideration.

S U B J E C T S AND M E T H O D S

If the patient was aphakic or had lens changes characteristic of senile cataract (posterior subcapsular or cortical changes or nuclear sclerosis) in association with a best corrected visual acuity of 6/9 (20/30) or worse, we referred him to a more experienced definitive examiner for an extensive corroborative cataract evalua­ tion. Prevalence data for senile cataract were based on the judgement of the defin­ itive examiner. We used historical data and the results of the ocular examination to exclude patients with congenital cata­ racts or secondary cataracts caused by trauma, uveitis, or the like. A pat'ent was declared a glaucoma sus-

Of the 3,977 surviving members of the original Framingham Heart Study popu­ lation, 2,675 members, ranging in age from 52 to 85 years in 1973, volunteered From Boston University School of Medicine, De­ partment of Ophthalmology (Drs. Kini and Leibo­ witz), Harvard Medical School Department of Pre­ ventive and Social Medicine (Dr. Colton and Ms. Nickerson); National Eye Institute (Dr. Ganley), Bethesda, Maryland, and Boston University School of Medicine, Department of Medicine (Dr. Dawber). This study was supported in part by contract NIHNEI-72-2112 from the National Eye Institute. Reprint requests to M. M. Kini, M.D., Boston University School of Medicine, Department of Oph­ thalmology, 80 E. Concord St., Boston, MA 02118. 28

AMERICAN JOURNAL OF OPHTHALMOLOGY 85:28-34, 1978

VOL. 85, NO. 1

THE FRAMINGHAM EYE STUDY

pect on the basis of the screening exami­ nation if any of the following were noted in either eye: (1) history of previous diag­ nosis or treatment for glaucoma; (2) ante­ rior chamber angle closed or less than 10 degrees in any quadrant; (3) average in­ traocular pressure (IOP) of 22 mm Hg or greater, recorded by applanation tonometry; (4) average pressure difference of 3 mm Hg or greater between the two eyes and IOP of 16 mm or more in one eye; (5) cup:disk ratio of 0.5 or greater in the horizontal or vertical meridian; or (6) the cup: disk ratio in the two eyes differed by 0.2 or more. Glaucoma suspects were re­ ferred for a definitive examination, in­ cluding repeat applanation tonometry, gonioscopy, and visual field testing for glaucoma screening by a modification of Armaly's technique. 5 Perimetry was used to detect the characteristic visual field defects associated with open-angle glau­ coma (such as blind spot enlargement of the Seidel type, arcuate scotoma, paracentral scotoma, nasal step, or advanced glaucomatous defect). We defined openangle glaucoma as the presence of any of the above field defects in those glaucoma suspects without angle abnormalities, lens dislocation, intraocular tumor, con­ genital disorders, uveitis, or other condi­ tions precluding a diagnosis of angle-clo­ sure, secondary or congenital glaucoma. Patients were referred for a definitive examination if the screening examiner, using direct ophthalmoscopy, identified or suspected the presence of microaneurysms or dot hemorrhages. We considered individuals positive for diabetic retinopathy if the definitive examiner reported they had any of the following: (1) retinal hemorrhages or microaneurysms; (2) soft or hard exudates; (3) intraretinal microvascular abnormalities; (4) macular ede­ ma; or (5) neovascularization of charac­ teristic number and distribution, with noncontributory history of other predis­ posing conditions (such as systemic hy­ pertension, blood dyscrasias, hypervisc-

29

osity states). The evaluation of changes consistent with diabetic retinopathy was based on a modification of the protocol used in the Collaborative Diabetic Reti­ nopathy Therapy Trials. Each character­ istic abnormality was illustrated in stan­ dard fundus photographs available as a reference to the examiner. Similarly, the screening examiner re­ ferred for a definitive examination all patients with definite or suspected drusen or macular pigment disturbance when the best corrected visual acuity in the affect­ ed eye was 6/9 (20/30) or worse. Persons were also referred for definitive examina­ tions if they had definite or suspected elevation of the pigment epithelium or the neurosensory retina, or perimacular circinate exudates. The definitive exami­ nation included inquiry and examination for evidence of uveitis, intraocular sur­ gery or tumors, ocular trauma, hypotony, retinal vein occlusion, diabetes melli'tus, sun gazing or retinal detachment, and factors that might cause macular pigmen­ tary disturbance. The diagnosis of senile macular degeneration was made if the definitive examiner observed degenera­ tive changes of either the dry type (in­ cludes pigment disturbance or drusen formation) or the exudative type (includes elevation of the pigment epithelium or neurosensory retina), and if the results of examination were noncontributory for a congenital, secondary, or other cause. Thus, we made the diagnosis of each disease on the basis of exclusion. It was not possible to achieve 100% success in examining the total population, nor was it possible to obtain the contin­ ued participation of all subjects selected for the definitive examination. True prev­ alence rates can rarely be determined and our data are no exception. Therefore, we initially calculated prevalence rates under three alternative assumptions, 3 , 4 provid­ ing a range within which the true value probably lies: 1. All persons not screened and all sus-

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AMERICAN JOURNAL OF OPHTHALMOLOGY

pects with incomplete status (either failed to take the definitive examina­ tion or to return for a glaucoma recall examination) have no disease. 2. All persons for whom final diagnosis was not completed are negative for disease, and those not screened have the same disease prevalence as those who were. 3. Suspects for whom a final diagnosis was not completed have the same disease prevalence as suspects with final diagnoses, and those not screened are similar in disease prev­ alence to those who were. Method 1 almost certainly provides a prevalence estimate that is too low. Most studies show that nonparticipants tend to have higher disease rates than partici­ pants. Method 3 assigns the same disease rates to the nonparticipants and those who did not have a definitive examination as were found in the examined group. While this probably still underestimates the true prevalence, of the three methods, it most likely approximates the true value. Further discussion of prevalence will present data calculated under the assumptions outlined in method 3. RESULTS

Approximately one fourth of the surviv­ ing Framingham Heart Study cohort had moved outside the Framingham area, de­ fined by a radius of approximately 25 miles from the city (Table 1). We exam­ ined 84% of those living within the im­ mediate Framingham environs, but only 19% of those living outside the area. Data are presented for the former group only. The association between senile cata­ racts and age is demonstrated (Table 2). Our data show a prevalence of 4.6% at age 52 to 64 years, 18% at 65 to 74 years, and 46% at age 75 to 85 years. In each age group, women have higher prevalence rates than men, but the differences are within reasonable limits of chance fluctu-

JANUARY, 1978 TABLE 1

FRAMINGHAM EYE STUDY POPULATION

Age (yrs)

No. Eligible

No. Examined (%)

52-64 65-74 75-85

1,544 909 478 2,940

1,372 (89) 755 (83) 350 (72) 2,477 (84)

52-64 65-74 75-85

502 357 178 1,037

94 (19) 78 (22) 26 (15) 198 (19)

"Includes all subjects living within a 25-mile radius of Framingham.

ation even when differences within the separate age groups are combined. At age 52 to 64 years, the prevalence rate of diabetic retinopathy (Table 2) is about 2%, rising to about 3% at age 65 to 74 years, and 7% at age 75 to 85 years. The upward trend with age is significant (P

Prevalence of senile cataract, diabetic retinopathy, senile macular degeneration, and open-angle glaucoma in the Framingham eye study.

PREVALENCE O F SENILE CATARACT, DIABETIC RETINOPATHY, SENILE MACULAR DEGENERATION, AND OPEN-ANGLE GLAUCOMA IN T H E FRAMINGHAM EYE STUDY M. M. K I N I...
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