Ageing could be a cause for low vision in elderly people, but in others, the cause for low vision could be an infection, structural damage to some part of the eye, cancer of the eye, diabetes or even brain injury.
The term Low Vision is self-explanatory. It indicates a condition in which a person’s sight is compromised. The person has not lost his vision, but rather cannot see very clearly. Ageing could be a cause for low vision in elderly people, but in others, the cause for low vision could be an infection, structural damage to some part of the eye, cancer of the eye, diabetes or even brain injury. Depending on the cause of low vision and the extent to which vision is impaired, the eye doctor will prescribe medication and treatment. In many cases, vision rehab will prevent further deterioration of vision, even if it does not cure the condition
The Definition of Low Vision
As per the National Programme for Control of Blindness (NPCB) , low vision is defined as visual activity of less than 6/18 on Snellen’s chart. Ideally, when a person realises he/she cannot see very well, they visit the ophthalmologist, do a routine eye examination and return home with a prescription for eyeglasses; and when the eyeglasses arrive, they can see better. In some cases, corrective surgery will rectify blurred vision which is called curable blindness. However, in a few individuals neither prescribed eye gear nor surgery will improve their vision.
Types of Low Vision
Low Vision is divided into types based on how your vision has been compromised.
#1 Central Vision Loss – People with this condition cannot see things that are in the centre of their vision.
#2 Peripheral Vision Loss – In this case, the individual cannot see clearly things that lie in the periphery of his/her visual field.
#3 Night blindness – As the name indicates, it refers to poor vision after dark or in low light.
#4 Hazy Vision – In this case, the overall vision is poor. The person is not blind, but his/her entire visual field is hazy.
#5 Blurred Vision – For people with blurred vision, objects near and far appear out of focus.
Causes for Low Vision
There can be many causes for Low Vision and treatment varies depending on each. Some of the most common causes of Low Vision are:
Macular Degeneration. This is a condition that affects the retina. The macular area on the retina is responsible for sharp central vision. When the macular is affected, it causes blurry vision. While the exact cause of the condition is unknown, ageing is considered a key factor. If left unchecked Macular Degeneration can lead to permanent blindness.
Glaucoma. When the flow or draining of fluids within the eye is affected, this causes fluctuations in eye pressure. Increased internal pressure in the eyes damages the optic nerve. This condition is termed Glaucoma. Gradually deterioration of peripheral vision is the first sign of Glaucoma, but unfortunately, most people fail to realise it until they have lost most of their vision. When diagnosed in its early stages Glaucoma can be treated with drugs or surgery to prevent further vision loss.
Cataract. This condition occurs due to the clouding of the eye lens, which reduces the light reaching the retina, thereby resulting in poor vision. Ageing is the primary cause of a cataract. In most cases, the condition is rectified with surgery.
Diabetic Retinopathy. Uncontrolled blood sugar levels are known to cause vision trouble. Diabetes can cause blood vessels in the eyes to leak and over time this can damage the retina. Surgery can help prevent further vision loss, but keeping blood sugar levels under control is the best way to prevent diabetic retinopathy.
Retinal Detachment. In rare cases, eye trauma, a tumour or even an infection can cause the retina to detach itself from the underlying layer. This causes loss of vision. In most cases, with surgery, the retina can be reattached and vision can be partially or fully restored.
Brain Injury. Head injuries, brain damage and stroke can also cause poor vision. Symptoms include poor depth perception, misalignment of the eyes, blurred vision, double vision and defective field of vision.
Rehab and Treatment for Low Vision
Upon diagnosis of the cause of Low Vision, the doctor decides how to treat the condition. This could be via Low Vision devices or eye-exercises, or a combination of both. Even though vision may not be completely restored, treatment and rehab will enhance vision to help them carryout their day to day activities.
Some Low Vision Devices are listed below:
Spectacle-mounted Magnifiers – A magnifying lens is mounted on the person’s spectacles to help the person do close-up tasks such as reading or writing.
Handheld Telescopes – A miniature telescope with a magnifying lens is used to see objects across the room or at a slight distance. The telescope can even be mounted on the person’s spectacles.
Handheld Magnifiers – A handheld optical magnifying lens comes in handy for a quick close glance at objects.
Electronic Magnifiers – This is a system, almost like a camera, that allows the person to see things that are near and things that are at a distance. The colour, brightness and levels of magnification can be adjusted as per the individual’s requirement.
Vision Rehab – Patients with Low Vision, besides using the above-mentioned devices, can benefit from vision rehab. The program is designed to equip the patient with a variety of techniques that help them perform day-to-day activities independently.
CONSULTANT – OPHTHALMOLOGIST
MBBS, DNB, FMRF, FICO