Ophthalmic Epidemiology: A Clouded Vision

1
Ophthalmic EpidemiologyA Clouded Vision

• April 10, 2000
• Michael B. Gorin, M.D. Ph.D.
• gorinmb_at_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

• Cataract 17 million
• Trachoma 6.0 million
• Glaucoma 3.0 million
• Xerophthalmia 0.5 million
• Onchocerciasis 0.5 million
• AMD 1.0 million
• Diabetic retinopathy 0.25 million
• Leprosy 0.25 million
• Others 2.5 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 lt 20 years old
• 51 lose sight gt50 and lt80
• 15 lose sight gt 80 years old
• Incidence
• 50 of new cases are people over 80
• Imbalance due to differences in life
  expectancy and duration of blindness.
• Blind lt 10 years - 74
• Blind gt10 years - 26
• Blind gt 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 lt 20 degrees)
• 20/500 - 20/1000 profound vision impairment -
  WHO and several European countries definition of
  blindness (visual field lt 10 degrees), CF lt 3m
• lt 20/1000 Near-total visual impairment used by
  some developing countries as definition of
  blindness (visual field lt 5 degrees), HM, LP
• NLP Total visual impairment

11
Ocular pathology

• Clinical examination
• Slit lamp biomicroscopy
• Ophthalmoscopy (fundus examination)

12
(No Transcript)
13
Ocular pathology

• Grading systems
• Ocular dryness
• (use of vital dyes, rose bengal and lissamine
  green) - comparison with standard photos (CSP).

• Conjunctival scarring - CSP
• Cataracts - LOCS III (CSP)
• Optic nerve- optic nerve cupping, CSP
• Retina - disease-specific (ie ARM, diabetes)

14
Documentation of ocular pathology

• Ratings by clinicians tend to be poorly
  standardized and inconsistent.
• Major emphasis in recent years has been on
  photodocumentation 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 (gt80), 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 lt20/30
• ARM - no vision impairment
• Prevalence ()
• Age range AMD ARM Blindness due to AMD
• 60 - 64 2.3 12.3 0.007
• 65 - 69 5.9 18.0 0.012
• 70 - 74 12.1 17.0 0.057
• 75 - 80 27.3 17.8 0.115
• Vinding (1989) - Denmark
• Krumpasky et al (1996) - Germany

21
Age-related macular degeneration (AMD)

• 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

22
Age-related macular degeneration (AMD)

• Success of laser treatment
• Vision 2 years after randomization to treatment
  or observation (subfoveal lesions)
• Deterioration in vision Treated Observed
• lt 2 lines 33 18
• 2-3 lines 23 17
• 4-5 lines 24 28
• gt 6 lines 20 37
• MPS 1991

23
Age-related macular degeneration (AMD)

• Success of laser treatment
• Vision 2 years after randomization to treatment
  or observation (extrafoveal lesions)
• Deterioration in vision Treated Observed
• Unchanged, improved 57 28
• Decreased 2-5 lines 28 27
• Decreased 6-9 lines 6 27
• Decreased gt 10 lines 6 18
• MPS 1982

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
• gt60 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)
• Vision Young Onset Older Onset
• 20/40 - 20/63 3.3 7.3
• 20/80 - 20/160 1.4 3.0
• below 20/200 3.6 1.6
• Diabetic retinopathy
• Nonproliferative Proliferative
• Macular edema Ischemic maculopathy

28
Nonproliferative Diabetic Retinopathy
Proliferative Diabetic Retinopathy
29

• Diabetes mellitus
• Visual impairment in IDDM and NIDM
• Age range (yrs) of patients
• Unilateral Bilateral
  Blindness
• visual impairment
• IDDM
• lt50 5.4 0.9 3.6
• gt50 18.2 8.7 12.2
• NIDM
• lt70 7.7 2.8 2.1
• gt70 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 group Treated group
• 12 3.4 1.8
• 24 13.6 6.6
• 48 27.4 12.6
• 60 32.1 15.2
• 72 34.2 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