Low vision is a condition caused by eye disease, where the visual acuity is 20/70 or poorer in the better-seeing eye, which cannot be corrected or improved with regular eyeglasses. A visual acuity of 20/70 means that the person standing 20 feet from an eye chart can see what a person with perfect vision can see from 70 feet away.
How is low vision measured?
A Snellen Eye Chart is used to measure a person’s visual acuity. The chart contains rows of letters, numbers, or symbols, printed in standardized graded sizes. One is asked to read or identify the rows at a distance of 20 feet. If one is able to read the 8th line from 20 feet away, the visual acuity is recorded as 20/20. If the last thing one can read from 20 feet away is the 3rd line, the visual acuity is recorded as 20/70. If you are analyzed to have low vision, you will need to have a different kind of eye examination performed by an eye specialist doctor who will use different and more detailed tests to determine what you can and cannot see.
How is low vision different from legal blindness?
Legal blindness is a term used by ophthalmologists to determine one’s eligibility for vocational training, schooling, rehabilitation, low vision devices, disability benefits, and tax exemption programs. This does not determine what a person can and cannot see. Legal blindness can be defined as a visual acuity of 20/200 or less in the better-seeing eye with best conventional correction. If one can read only the first line from 20 feet away on the Snellen Eye Chart, the visual acuity is recorded as 20/200. If this is the case, the person is qualified as legally blind. If you are worried about your child suffering from vision problems, you can always approach a specialized paediatric ophthalmologist to determine if your child is a victim of low vision, legal blindness, or any other eye problem that can be treated to bring back the vision of your little one.
Different levels of visual impairment
As per the World Health Organization’s measurements, here is the list of the various levels of visual impairment.
- Moderate Visual Impairment – The Snellen visual acuity here ranges from 20/70 to 20/160.
- Severe Visual Impairment – The Snellen visual acuity here ranges from 20/200 to 20/400.
- Profound Visual Impairment – The Snellen visual acuity here ranges from 20/500 to 20/1000.
Light perception
How a person perceives the difference between light and dark, or day and night, depends upon the condition of their visual level. Persons with low vision can definitely differentiate between light and dark, but people with severely reduced vision can also determine the difference between the two! Total blindness is when there is complete lack of light perception. However, today, only 15% of eye patients belong to the total blind category. Others who cannot see actually have a light perception of some percentage, which means they are not totally blind. They can yet differentiate between light and dark.
Arohi Eye Hospital is a reputed and reliable eye care hospital where you can come for all your vision related problems and doubts. Your eyes can be diagnosed to determine the actual problem you are having, while helping you with the most appropriate treatment required for your condition.
Dr. Shradha Goel
Dr. Shradha Goel, Chief Surgeon at Arohi Eye Hospital, is a renowned Phaco-LASIK surgeon with over 10,000 surgeries to her credit. She earned her MBBS from Grant Medical College, Mumbai, and a Master’s in Ophthalmology from Kasturba Medical College, Manipal. As a member of the American Academy of Ophthalmology, Dr. Goel specialises in LASIK, refractive errors, and cataract treatments.