Contact lenses

Same power, two different eyes, two different lenses

A spectacle prescription does not transfer straight onto a contact lens. The spectacle lens sits twelve millimetres from the eye and the contact lens sits on it, and past a certain strength that gap changes the number.

Then come the measurements spectacles never need: the curvature of your cornea, its diameter, how the tear film spreads when you blink and how long it takes to break up. Material, base curve and replacement schedule all follow from that.

The fitting ends with the lens in and you looking through it for a while, not standing at the counter. Seeing well is half of it. The other half is still being comfortable six hours later.

Lenses and water: the rule nobody here likes

The sea, the pool, the hot tub and the shower. In all four the water carries microorganisms, and a contact lens holds them pressed against your cornea for hours. It is the route by which the hardest corneal infections arrive, which is why no serious fitter will tell you to swim in them.

Living beside the beach makes this the most broken rule of the lot. If you are going to swim anyway, do it in daily disposables and goggles, and throw those lenses away as you come out of the water rather than putting them back in the case.

The alternative that annoys people least is usually a different one: prescription sunglasses for the beach day, lenses for everything else. We put it that way because telling you never to swim achieves nothing.

Eyes dry out faster on this coast

Wind, salt air, long hours of daylight and air conditioning from May to October. That combination evaporates the tear film faster, and a contact lens needs those tears to keep from gripping the cornea.

It shows in specific ways: vision that smears and clears when you blink, stinging by mid-afternoon, and a lens you could not feel in the morning asking to come out by the seventh hour.

All of that can be worked with. We change the material or the replacement interval, adjust the wearing hours, add a preservative-free drop. Sometimes the honest answer is lenses in the morning and spectacles from six o’clock.

After forty-five

Reading age does not rule out contact lenses, but it changes the conversation. Multifocals put distance and near in the same lens and handle most situations well, in exchange for a little sharpness on very small print or in poor light.

The other route corrects one eye for distance and the other for near. Some people find it natural within a week and others never warm to it. You try it before buying anything, because this is not a decision to make from a leaflet.

The check-up almost nobody asks for

The lens you have stopped noticing is exactly the one worth checking. The cornea gives warning late and quietly, and an eye that has slowly got used to less oxygen does not hurt.

At the check we look at the eye with the lens in and with it out, confirm it still moves as it should, and go through how you clean them and how often a bottle of solution gets stretched past its date. Half the problems turn up right there.