As per The Rights of Persons with Disabilities Act, 2016, "low-vision" means a condition where a person has any of the following conditions:
- visual acuity not exceeding 6/18 (person can see at 6 metres what someone with standard vision could see from 18 metres away) or less than 20/60 (feet) up to 3/60 (metres) or up to 10/200 (Snellen, feet) in their better eye with best possible corrections; or
- limitation of the field of vision subtending an angle of less than 40 degree up to 10 degree.
For low vision, the following two definitions are in use by the World Health Organization (WHO):
- (WHO) Low vision is visual acuity less than 6/18(person can see at 6 metres what someone with standard vision could see from 18 metres away)and equal to or better than 3/60 in the better eye with best correction
- (Low Vision Services or Care) Aperson with low vision is one who has impairment of visual functioning even after treatment and/or standard refractive correction, and has a visual acuity of less than 6/18 to light perception, or a visual field less than 10 degrees from the point of fixation, but who uses, or is potentially able to use, vision for the planning and/or execution of a task for which vision is essential
- Moderate Vision Impairment – presenting visual acuity worse than 6/18.
- Severe Vision Impairment – presenting visual acuity worse than 6/60.
Low vision can be caused due to numerous conditions. The main causes of low vision in India are:
- Refractive error: Also known as refraction error, is a problem with focusing light accurately onto the retina due to the shape of the eye. The most common types of refractive error are near-sightedness, far-sightedness, astigmatism, and presbyopia. Refractive errors are most commonly due to genetics and environmental/lifestyle factors
- Cataract: Is a clouding of the lens in the eye which leads to a decrease in vision. Cataracts are most commonly due to aging but may also occur due to trauma or radiation exposure, be present from birth, or occur following eye surgery for other problems, or due to other reasons.
- Posterior segment eye disease/disorder: Epidemiologically is commonly defined as diseases of the retina, choroid and optic nerve and primarily includes (other than glaucoma discussed below) age-related macular degeneration and diabetic retinopathy. Age-related macular degeneration is a medical condition which may result in blurred or no vision inthe center of the visual field, most commonly due to ageing but also due to genetics and smoking. Diabetic retinopathy, also known as diabetic eye disease, is a medical condition in which damage occurs to the retina due to diabetes mellitus.
- Glaucoma: Is a group of eye diseases which result in damage to the optic nerve and cause vision loss. Glaucoma is most commonly due to ethnicity, genetics, diabetes, use of steroids and any trauma to the eyes.
The treatment of low vision depends on the cause of low vision, including but not limited to the following:
- Visual impairment due to uncorrected refractive error can be addressed by doing a refraction and providing appropriate spectacles.
- For cataractpatients, cataract surgery would, in most cases, restore their sight.
- Inflammatory andinfectious causes of low vision can be treated with medication in the form of drops or pills.
- Low vision due to nutritional deficiency can be addressed by dietary changes.
Statistics in India
The WHO has estimated approximately 54 million people with low vision in India.
References for More Reading and Understanding/Sources