Refractive Error Treatment

Seeing sharply requires light to be brought to focus exactly on the retina. Whether that happens depends on the length of the eyeball and the focusing power of the cornea and lens in front of it, and a refractive error is a mismatch between the two.

There are four patterns. In short sight the eye is slightly too long for its focusing power, so distant objects focus in front of the retina and blur while near work stays clear. In long sight the eye is relatively too short, and the focusing muscle has to work continuously to compensate, which in younger people shows up as strain and headache before it shows up as blur. In astigmatism the cornea is curved more steeply in one direction than the other, so no single distance is properly in focus. After the age of about forty the lens inside the eye stiffens and near focus is lost, which happens to everyone and is a normal ageing change.

Short sight is becoming markedly more common in Indian children. Long hours of close work and little time outdoors are the two factors most consistently linked to it. Powers usually change through childhood and settle in the early twenties.

Vision is measured in each eye separately on a chart, with and without your current glasses. An instrument then takes an objective reading of your focusing error in a few seconds, and that reading is refined subjectively by your optometrist showing you pairs of lenses and asking which is clearer. The subjective result is the prescription, because the number that makes you see best is the one that counts.

In children, drops are put in first to switch off the focusing muscle completely. A child's focusing muscle is strong enough to mask a large amount of long sight, and measuring without the drops gives a wrong and sometimes badly wrong answer. The drops blur near vision for a day.

Before any surgical correction is considered, the assessment goes further: the shape and thickness of the cornea are mapped to rule out thinning, the pupil size is measured in the dark, the tear film is assessed, and the retina is examined with the pupils dilated. Your doctor also wants two prescriptions at least a year apart showing the power has stopped changing.

Glasses correct the error the moment you put them on, though a new prescription or a first astigmatic correction can make the floor look tilted for two or three days while you adapt. Contact lenses need a fitting appointment and a teaching session, and the hours of wear are built up over a week or two.

Surgical correction is a day procedure with numbing drops and takes minutes per eye. Most people see usefully the next morning, though it is common to be light-sensitive, watery and uncomfortable for the first six to twelve hours. Plan two to three days away from desk work, a week for dusty or physical work, and no swimming, eye rubbing or contact sport for a month. Drops run for two to four weeks.

Driving waits until your vision has been measured at a review, usually the day after. Vision can fluctuate and night glare can be noticeable for the first few weeks and settles over three months. Your surgeon will see you the next day, at one week and at one month.