Universal Eye Health
Can you see to read this?
Yes? But imagine going blind or having any vision loss.
About 314 million people worldwide live with visual impairment, of whom 45 million are blind and 87% live in developing countries. About 85% of visual impairment is treatable or preventable. Visual loss is a serious public health problem in India. About 1/3 of the world’s blindness caused by cataract occurs in India. Each year about 3.8 million in India are blinded by cataract.
There are significant variations in visual impairment. Some people can distinguish only light. Some people may have only side vision. Some see everything as a blur while others have blank spots.
There are 4 levels of visual function, according to the International Classification of Diseases
- Normal vision
- Moderate visual impairment
- Severe visual impairment
Moderate visual impairment combined with severe visual impairment are grouped under the term “low vision”: low vision taken together with blindness represents all visual impairment.
Visual impairment (or vision impairment) is vision loss (of a person) to such a degree as to qualify as an additional support need through a significant limitation of visual capability resulting from either disease, trauma, or congenital or degenerative conditions that cannot be corrected by conventional means, such as refractive correction or medication his functional loss of vision is typically defined to manifest with
- best corrected visual acuity (is acuteness or clearness of vision) of less than 20/60, or significant central field defect,
- significant peripheral field defect including homonymous or heteronymous bilateral visual, field defect or generalized contraction or constriction of field, or
- reduced peak contrast sensitivity with either of the above conditions
Some of the most common causes of visual impairment include:
- age-related macular degeneration (AMD) – where the central part of the back of the eye (the macula, which plays an important role in central vision) stops working properly
- cataracts – where cloudy patches can form within the lenses of the eyes
- glaucoma – where fluid builds up inside the eye, damaging the optic nerve (which relays information from the eye to the brain)
- diabetic retinopathy – where blood vessels that supply the eye become damaged from a build-up of glucose
Visual impairment can also be caused by brain and nerve disorders, in which case it is usually termed Cortical Visual Impairment (CVI).
Vision loss caused by AMD, glaucoma and diabetic retinopathy cannot usually be reversed. However, there are several treatments that can prevent further damage to vision, or at least slow down the progression of these conditions.
Your visual acuity and visual field will have to be tested by an ophthalmologist (a doctor who specializes in diagnosing and treating eye conditions)
Types of Visual Impairment
Visual impairment is usually classified as either ’sight impaired’ or ‘severely sight impaired’.
Sight impairment, previously called ‘partial sight’, is usually defined as:
- having poor visual acuity (3/60 to 6/60) but having a full field of vision, or
- having a combination of slightly reduced visual acuity (up to 6/24) and a reduced field of vision or having blurriness or cloudiness in your central vision, or
- having relatively good visual acuity (up to 6/18) but a significantly reduced field of vision
Severely sight impaired
The legal definition of severe sight impairment (which was previously called ‘blindness’) is when ‘a person is so blind that they cannot do any work for which eyesight is essential’.
This usually falls into one of three categories:
- having very poor visual acuity (less than 3/60), but having a full field of vision
- having poor visual acuity (between 3/60 and 6/60) and a severe reduction in your field of vision
- having slightly reduced visual acuity (6/60 or better) and a significantly reduced field of vision
The sooner vision loss or eye disease is found and treated, the greater your chances of keeping your remaining vision. You should have regular comprehensive eye exams by an eye care professional. The role of a low vision specialist (Ophthalmologist) is to maximize the functional level of a patient’s vision by optical or non-optical means.
(Dr.Mrs Archana Swarnakar is an Ophthalmologist at Getwell Hospital, Dhantoli, Nagpur.)
It’s her endeavour to create awareness among masses on the eve of World Sight Day.