1. Ophthalmic Epidemiology: A Clouded Vision April 10, 2000 Michael B. Gorin, M.D. Ph.D. gorinmb@msx.upmc.edu

2. Objectives of ophthalmic epidemiology Establish the incidence and prevalence of eye disorders that cause vision impairment and/or blindness Determine the societal impact (social and economic) of vision loss Assess the potential and real impact of preventive and treatment efforts for eye problems

3. Causes of Worldwide Blindness Cataract17 million Trachoma6.0 million Glaucoma3.0 million Xerophthalmia 0.5 million Onchocerciasis0.5 million AMD1.0 million Diabetic retinopathy0.25 million Leprosy 0.25 million Others2.5 million –85% of blindness is in Africa and Asia –85% of cases are potentially treatable or preventable Prevalence: –0.125-0.25% in Western world –0.2-1.5% (av 0.75%) in Asia –0.3-3.1% (av 1.2%) in Africa Allen Foster in Clinical Ophthalmology - Duane, ed. (1991)

4. Aging and Blindness Prevalence (in Germany) : –15 % lose sight < 20 years old –51% lose sight >50 and <80 –15 % lose sight > 80 years old Incidence : –50% of new cases are people over 80 “Imbalance” due to differences in life expectancy and duration of blindness. –Blind < 10 years - 74% –Blind >10 years - 26% –Blind > 20 years - 10%

5. What is vision? Central visual acuity –Uncorrected and corrected –Refractive error (definition of myopia) –The Snellen chart and the ETDRS chart

6. What is vision? Contrast sensitivity –Pelli Robison chart –grating systems

7. What is vision? Peripheral vision –Visual Fields Kinetic and static Manual versus automated

8. What is vision? Color vision –Color plates, color chips, anomaloscopes Adaptation –Light recovery from bleach –Adaptometry

9. What is vision? Other measures of visual function –Electrophysiology –Ocular movements –Visual function questionnaires - VF-14 Initially validated for cataracts more extensive use in all eye studies

10. What is the definition of blindness? 20/10 - 20/25: Normal 20/30 - 20/60: Near-normal 20/70 - 20/160 : Moderate vision impairment - eligible for education assistance in US 20/200 - 20/400: Severe vision impairment - legal blindness in US (visual field < 20 degrees) 20/500 - 20/1000: profound vision impairment - WHO and several European countries definition of blindness (visual field < 10 degrees), CF < 3m < 20/1000: Near-total visual impairment: used by some developing countries as definition of blindness (visual field < 5 degrees), HM, LP NLP: Total visual impairment

11. Ocular pathology Clinical examination: –Slit lamp biomicroscopy –Ophthalmoscopy (fundus examination)

13. Ocular pathology –Conjunctival scarring - CSP –Cataracts - LOCS III (CSP) –Optic nerve- optic nerve cupping, CSP –Retina - disease- specific (ie ARM, diabetes) Grading systems: – Ocular dryness (use of vital dyes, rose bengal and lissamine green) - comparison with standard photos (CSP).

14. Documentation of ocular pathology Ratings by clinicians tend to be poorly standardized and inconsistent. Major emphasis in recent years has been on photodocumentatio n and the use of Reading Centers to grade pathology The general level of photographic quality in the medical community is low. For research studies, extensive training and certification of photographers is required.

15. Documentation of ocular pathology Reading Centers have been very effective in studies of diabetic retinopathy. (subjects diagnosed prior to entry) Reliability of graders for large numbers of patients with mixed (and unspecified) disorders is unknown.

16. Specific issues in eye research Is one assessing the subject or the eye? Relatedness between eyes of a single individual Research design with bilateral and monocular cases Use of the contralateral eye as a control Masking of the subject and observer Is one comparing the same definition of the disease among studies? (ie AMD, myopia, glaucoma) Diagnostic reliability, sample bias 10% of cases have vision loss from 2 different conditions, though studies often only cite the cause of the second eye.

17. Causes of vision loss Trauma –Recreational, work-related, military Systemic Disease –Diabetes, vascular disease, hypertension Aging/Eye Specific –Cataracts, age-related maculopathy, glaucoma Infectious –Trachoma, onchocerciasis, immunocompromised individuals Congenital/Hereditary - –Cataracts, malformations, glaucoma, retinal degenerations Nutritional and Toxic –Vitamin A deficiency, methanol Tumors –Metastatic, primary malignancies (children / adults)

18. Infectious causes of vision loss Trachoma –Affects 500 million –Estimated 6 million are blind Onchocerciasis –Endemic across equatorial Africa (99%), some areas of South and Central America –80 million exposed, 18 million infected, 2 million blind –Transmitted by blackfly - filial nematode –Treatment - vector control, ivermectin (annual dose for a minimum of 10 years) Other ID: leprosy, syphillis –Estimated 10-12 million cases of leprosy –WHO estimated that 250,000 blind from disease

19. Leading causes of blindness in Western societies Age-related macular degeneration (aka: AMD, ARM, SMD) Dry versus Wet Atrophic versus Exudative (CNVM) Most common cause of blindness Majority of cases are “dry” form (>80%), however 88% of those registered as legally blind (in Germany) from AMD had exudative disease.

20. Age-related macular degeneration (AMD) –AMD defined as macular changes and <20/30 –ARM - no vision impairment Prevalence (%) Age rangeAMD#ARM#Blindness due to AMD* 60 - 64 2.312.30.007 65 - 69 5.918.00.012 70 - 7412.117.00.057 75 - 8027.317.80.115 # Vinding (1989) - Denmark * Krumpasky et al (1996) - Germany

21. Risk factors: –Smoking 2.5 fold increased risk – positive family history –Others - sex, diet, eye color, hypertension, cardiovascular disease are controversial Unilateral CNVM - risk to other eye: –Incidence of 12-15% per year for 60-69 year olds Age-related macular degeneration (AMD)

22. Success of laser treatment –Vision 2 years after randomization to treatment or observation (subfoveal lesions) Deterioration in visionTreated Observed < 2 lines33%18% 2-3 lines23%17% 4-5 lines24%28% > 6 lines20%37% MPS 1991 Age-related macular degeneration (AMD)

23. Success of laser treatment –Vision 2 years after randomization to treatment or observation (extrafoveal lesions) Deterioration in visionTreated Observed Unchanged, improved 57%28% Decreased 2-5 lines 28%27% Decreased 6-9 lines 6%27% Decreased > 10 lines 6%18% MPS 1982 Age-related macular degeneration (AMD)

24. Leading causes of blindness in Western societies Glaucoma –Loss of vision due to progressive optic nerve damage often (but not always) associated with increased intraocular pressure –Varying definitions - IOP, Visual fields, cupping –Different types of glaucoma Congenital Open- angle Narrow-angle Syndromic

25. Glaucoma –Glaucoma affects 1.5-2.0% of population over the age of 40. Rises with age up to 8% for those over 80 –Current prevalence is 15% of all cases of blindness (developed nations) –Age of onset of blindness from glaucoma >60 years : 79% –Those under 65 years old Glaucoma-related blindness associated with other conditions - 36% –Those greater than 65 years old Glaucoma-related blindness associated with other conditions - 46%

26. Leading causes of blindness in Western societies Diabetic retinopathy –Women greater than men: 56% of the younger blind diabetic individuals 87% of the older blind diabetic individuals –In those under the age of 65, diabetes is the most common cause of blindness –However, 2/3 of diabetics do not become blind until after the age of 60 –Blindness from DR is a poor prognosis for survival

27. Diabetes mellitus –IDDM: 0.5-1.0% –NIDDM: large variations among countries and ethnic groups 0.7-3.0% –Prevalence (%) of vision impairment among diabetics - (Klein et al 1984) VisionYoung OnsetOlder Onset 20/40 - 20/63 3.37.3 20/80 - 20/1601.43.0 below 20/2003.61.6 –Diabetic retinopathy: NonproliferativeProliferative Macular edemaIschemic maculopathy

28. Proliferative Diabetic Retinopathy Nonproliferative Diabetic Retinopathy

29. Diabetes mellitus –Visual impairment in IDDM and NIDM Age range (yrs)% of patients Unilateral Bilateral Blindness visual impairment IDDM <505.4 0.9 3.6 >50 18.2 8.7 12.2 NIDM <707.7 2.8 2.1 >70 20.8 17.1 7.3 Nielson 1982 (Denmark)

30. Diabetes mellitus –Cumulative events of vision loss in DRS study after laser treatment Follow-up Cumulative rate of events (%) (months) Control groupTreated group 12 3.41.8 2413.66.6 4827.4 12.6 6032.1 15.2 7234.2 17.5 DRS 1981

31. Leading causes of blindness in Western societies Cataract Congenital - major cause of infantile blindness Secondary to or associated with other disorders Age-related –Age at onset of blindness from cataract Age 70 and greater : 70-85% of cases –Risk factors Age, poor education, myopia, hypertension, diabetes, glaucoma, smoking, beer drinking, certain drugs, low vital capacity, severe diarrhea, kidney failure