Acuvue Oasys (6 lenses)

Two weeks from the moment the blister is opened. The term runs on the calendar, not on the number of insertions: if you spent a couple of days in glasses, the lens still ages in its case. Stretching it because you wore it less is a poor trade — the material and its wettability are engineered for 14 days, and comfort and safety fall off after that.

The manufacturer permits extended wear for Acuvue Oasys, but only a specialist prescribes it in person. The decision depends on the state of the cornea and on how the eye tolerates overnight hypoxia, and it is made individually. By default the lenses come out at night. If a clinician does approve sleeping in them, they will also state how many consecutive nights.

Different materials and different economics. 1-Day is a daily disposable in senofilcon A with a different surface technology, thrown away every evening, with no solution or case involved. The two-week Oasys costs less per day of wear but requires an evening routine. Their optics and on-eye feel are close; the daily rhythm is not.

Only with a small one a clinician judged safe to leave uncorrected. If the prescription carries a cylinder (Cyl) and an axis (Axis), a spherical lens will not correct them and vision stays blurred. The toric version exists for exactly this — Acuvue Oasys for Astigmatism, on the same material and schedule. Which one you need is a specialist's call.

It is on a contact lens prescription, on the BC line. This model comes in two: 8.4 and 8.8 mm. The difference is fit — too flat and the lens shifts on blinking, too steep and it presses and lets less tear fluid move underneath. A base curve cannot be picked by feel at home; it is assessed on a slit lamp.

We don't require one to place an order, but you enter the parameters yourself, and getting them wrong costs more than the appointment would. A contact lens is a medical device that sits on the cornea, and it is fitted to the state of the eye, not to visual acuity alone. With no prescription, or one over a year old, book the free fitting.

Best avoided. Water — tap, pool and sea alike — carries microorganisms that a lens holds against the surface of the eye; the most dangerous of them, acanthamoeba, causes severe keratitis. In the shower, keeping your eyes closed under the stream is enough. For a pool use goggles, or better, take the lenses out beforehand.

Any multipurpose solution for soft contact lenses. The case is replaced every three months: a biofilm grows on its walls that rinsing does not remove. The solution in the case is changed in full every evening — topping up yesterday's defeats the disinfection. Once a bottle is opened the solution keeps for a limited period, stated on the pack.

Twelve weeks for one eye, or roughly 42 days worn in both. Two packs come to about 84 days, a quarter of daily wear. If you don't wear lenses every day the pack lasts longer by insertions but not by calendar: the two weeks from opening the blister run either way, whether the lens is on your eye or in its case.

Start with the obvious: room air, blink rate at a monitor, and whether the lens has outlived its two weeks. Rewetting drops compatible with contact lenses help. If the dryness repeats daily, that is a reason to see a specialist — the cause may lie in the tear film rather than in the lens.

The lens carries a «123» marking. Rest it on a fingertip and look from the side: the correct way round the edges form an even bowl, inside out they splay slightly outwards. The marking then reads correctly rather than mirrored. An inside-out lens does no harm, but it is felt and seats less well on blinking.

A pack of 6 covers about 42 days of wear for two eyes, and the cost per day is the pack price divided by that — the current figure is shown in the key facts block on this page. A daily disposable of comparable class runs roughly three times more per day, but needs no solution or case, so the difference is worth counting together with the care.