epidemiology of blindnesss and low vision aids
Post on 13-Apr-2015
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BY DR. FAIZ-UR-RAB
ASSISTANT PROFESSOR DUHS
LEARNING OBJECTIVES
• Definitions of blindness
• WHO classification of visual impairment
• Causes of blindness in developing & developed countries
• Causes of high prevalence in Pakistan
• Low vision aids
DEFINITIONS
• Legal Blindness: Visual acuity of less than 3/60 or its
equivalent.
• Low Vision: Visual acuity of less than 6/ 18 but ≥ 3/60 or
corresponding to visual field loss to less than 20° in the better
eye with best possible correction.
• Avoidable Blindness: Blindness which could be either treated
or prevented by known cost-effective means.
DEFINITIONS
• Functional Blindness: Loss of vision sufficient to prevent one
from being supporting in an occupation, making the
individual dependent on other persons, agencies or devices
in order to live.
• Industrial Blindness: It is present when a worker can no
longer pursue an occupation because of poor vision
WHO Classification (Visual Impairment)
Category Grade Visual Acuity Best
Corrected
Low Vision
1
2
6/18
20/60
3/10 (0.3)
6/60
20/200
1/10 (0.1)
Blindness
3
4
3/60
20/400
1/20 (0.05)
1/60
5/300
1/50 (0.02)
5 No light perception
THE PROBLEM:
• Worldwide 161 m people are visually impaired- 124m low vision & 37m blind.
• >90% of world’s visually impaired live in low and middle
income countries.
• Except in most developed countries, cataract remains the most common cause of blindness.
CAUSES OF BLINDNESS:
• IN DEVELOPED COUNTRIES:
•
Accidents ,Glaucoma, Diabetes, Vascular
diseases(hypertension), Cataract and Degeneration of Ocular
tissues esp. of the Retina and Hereditary conditions.
• IN DEVELOPING COUNTRIES:
Cataract
Refractive Errors
Glaucoma
Post. Segment Disorder
Surgical Complication
CAUSES OF CHILDHOOD BLINDNESS:
Refractive errors, Trachoma, Conjunctivitis, Xerophthalmia,
Congenital Cataract , Retinopathy of Prematurity.
CAUSES OF AVOIDABLE BLINDNESS: Cataract, Trachoma, Onchocerciasis, Childhood Blindness,
Refractive errors, Glaucoma, Diabetic Retinopathy.
EPIDEMIOLOGICAL DETERMINANTS:
• Age: More than 82% belongs to the group of >50yrs.
• Gender: Higher in females.
• Malnutrition: Vitamin A deficiency ,infectious diseases of
new born
.
• Social Class: Higher in low socio-economic status.
• Geographical: >90% in developing countries.
REASONS FOR HIGH PREVALENCE IN PAKISTAN
• Overall rise in size of population.
• Major population in rural areas have poor access to eye
care facilities.
• Inadequate availability of trained health personnel &
inadequate utilization of available ophthalmic surgeons.
• Poor nutritional status of mother and young children
• Adverse environmental conditions and domestic
unhygienic conditions.
• Lack of community awareness & poor health seeking
behaviour.
• Myths & misconceptions about surgeries.
LOW VISION AIDS
• All low vision aids work by presenting the patient
with
• A magnified view of object. Most are optical
systems
• Which act by increasing the angle subtended by
the
• Object at the eye, thus producing an enlarged
retinal
• Image.
GOALS OF LOW VISION
Increase functionality o Make the most of the remaining vision
Provide link to community resources and support services
Education
FUNCTIONAL EFFECTS OF LOW VISION
• Loss of central vision (visual acuity)
• Loss of peripheral vision (visual field)
• Glare and contrast
Issues Related to Decreased Acuity
• Difficulty reading
• Problems writing/ completing paperwork
• Inability to recognize distance objects and faces
Issues Related to Visual Field Loss
• Location of scotoma important!
• Generalized loss of visual field difficult to compensate for
• Mobility and independent travel
• Reading may require adaptations
Issues Related to Contrast
• Need for additional lighting
• Problems with glare
• Increased adjustment to changes in illumination
• Visual discomfort and fatigue
LIGHTING
GLARE & CONTRAST
Devices To Help Low Vision
STAND MAGNIFIERS
• Video magnifiers are sometimes called “closed-circuit television (CCTV) systems” and generally use stand-mounted or hand-held video cameras to project a magnified image onto a video monitor, a television (TV) screen, or a computer monitor.
COMMUNICATION GOALS
• Educate patient on eye condition
• Help them to understand what options are available and how
to use/ care for tools
– Glasses
– Low vision devices
– Technology
– Community resources
• Educate parents and teachers/ professionals on functional
implications
FUNCTIONAL IMPLICATIONS
• Print size
• Visual efficiency and fatigue
• Mobility issues
• Positioning/ classroom placement
• Lighting/ glare reduction needs
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