Download Ophthalmic Epidemiology A brief introduction

Ophthalmic Epidemiology:
A Clouded Vision
April 10, 2000
Michael B. Gorin, M.D. Ph.D.
[email protected]
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
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)
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%
What is vision?
• Central visual
acuity
– Uncorrected and
corrected
– Refractive error
(definition of
myopia)
– The Snellen chart
and the ETDRS
chart
What is vision?
• Contrast
sensitivity
– Pelli Robison
chart
– grating systems
What is vision?
• Peripheral vision
– Visual Fields
• Kinetic and
static
• Manual versus
automated
What is vision?
• Color vision
– Color plates,
color chips,
anomaloscopes
• Adaptation
– Light recovery
from bleach
– Adaptometry
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
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
Ocular pathology
• Clinical examination:
– Slit lamp biomicroscopy
– Ophthalmoscopy (fundus examination)
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 - diseasespecific (ie ARM,
diabetes)
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.
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.
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.
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)
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
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.
Age-related macular degeneration (AMD)
– AMD defined as macular changes and <20/30
– ARM - no vision impairment
Prevalence (%)
Age range
AMD#
ARM# Blindness due to AMD*
60 - 64
65 - 69
70 - 74
75 - 80
2.3
5.9
12.1
27.3
12.3
18.0
17.0
17.8
0.007
0.012
0.057
0.115
# Vinding (1989) - Denmark
* Krumpasky et al (1996) - Germany
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
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
< 2 lines
2-3 lines
4-5 lines
> 6 lines
33%
23%
24%
20%
18%
17%
28%
37%
MPS 1991
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%
6%
6%
28%
27%
27%
18%
Decreased 2-5 lines
Decreased 6-9 lines
Decreased > 10 lines
MPS 1982
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
• 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%
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
• 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
20/40 - 20/63
3.3
20/80 - 20/160
1.4
below 20/200
3.6
Older Onset
7.3
3.0
1.6
– Diabetic retinopathy:
• Nonproliferative
• Macular edema
Proliferative
Ischemic maculopathy
Nonproliferative Diabetic Retinopathy
Proliferative Diabetic
Retinopathy
• Diabetes mellitus
– Visual impairment in IDDM and NIDM
Age range (yrs)
% of patients
Unilateral
Bilateral
visual impairment
Blindness
IDDM
<50
>50
5.4
18.2
0.9
8.7
3.6
12.2
<70
>70
7.7
20.8
2.8
17.1
2.1
7.3
NIDM
Nielson 1982 (Denmark)
• Diabetes mellitus
– Cumulative events of vision loss in DRS study
after laser treatment
Follow-up
(months)
12
24
48
60
72
Cumulative rate of events (%)
Control group
Treated group
3.4
1.8
13.6
6.6
27.4
12.6
32.1
15.2
34.2
17.5
DRS 1981
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