Low vision: when the answer is not a stronger prescription

There is a point in some consultations where no lens improves matters. The refraction is optimal, the eye has been treated as far as treatment goes, and the vision is still substantially reduced. A great many people are told, at that point, that nothing more can be done.

That is the wrong conclusion, and it is where low vision rehabilitation begins.

What low vision means

Low vision is significant visual impairment that cannot be fully corrected by spectacles, contact lenses, medication or surgery, but where useful sight remains. It sits between full sight and blindness, and that middle ground is where most visual impairment actually is.

Very few people who are registered blind see nothing at all. Most have some vision — peripheral, or patchy, or usable only under particular lighting. Rehabilitation is the work of finding what remains and organising life around it.

What causes it here

In Nigeria the commonest causes are glaucoma, uncorrected refractive error, cataract that has not been operated, diabetic retinopathy, and corneal scarring from injury or infection. Age-related macular degeneration is increasingly present as the population ages.

Several of those are preventable, which is the argument for screening. But for someone already living with the consequence, prevention is beside the point. The question is what can be done now.

What an assessment involves

A low vision assessment is a different consultation from a routine eye examination, and it starts from the other end: not "what can you see?" but "what do you need to do?"

Reading the Bible or the Qur'an. Seeing a grandchild's face. Counting money. Reading a phone. Recognising a bus number. Continuing to work. The goals are specific, and the assessment works towards them.

It then measures the vision that remains in detail — not just acuity, but contrast sensitivity, the shape of the visual field, and how glare and lighting affect performance. Contrast and lighting frequently matter more to real function than the acuity figure does.

What helps

Magnification, in the right form for the task. Hand magnifiers, stand magnifiers, spectacle-mounted high-addition lenses, telescopes for distance, electronic magnifiers that enlarge onto a screen. Different tasks want different tools, and the strongest available magnifier is usually the wrong choice — higher power means a smaller field and a shorter working distance.

Lighting. The single most underrated intervention. Task lighting positioned close and over the shoulder can transform reading ability at no great cost. Many people are struggling in ambient light that would be inadequate for a fully sighted person.

Contrast. A dark cup on a light surface. A white chopping board for dark vegetables and a dark one for light. Marking the edges of steps. Cheap, and effective.

Filters to cut glare and raise contrast, which help substantially in some conditions.

Technology. Phones have screen magnification, high-contrast modes and screen readers built in and free. Text-to-speech, camera-based text reading, and object recognition apps have made an enormous difference in the last decade and cost nothing beyond the phone.

Training in eccentric viewing, for people with central field loss — learning to use a healthy off-centre part of the retina deliberately rather than fighting to look straight at things.

The part that is not clinical

Losing sight in adulthood is a significant life event and is frequently accompanied by depression, withdrawal and a loss of independence that outruns the actual visual impairment. Rehabilitation that addresses only the optics is doing half the job. Orientation and mobility training, occupational therapy, peer support and family education all belong in the picture.

Families sometimes help in the wrong direction — taking over tasks the person could still do, out of kindness, which accelerates the loss of independence. Being shown how to support without taking over is worth a conversation of its own.

Where to start

Ask your optometrist about a low vision assessment. Practitioners in the chapter's register can either provide one or refer you to a colleague who does. It is worth asking even if you have been told nothing more can be done — that sentence usually means nothing more can be done to the eye, which is a different statement.