THE VARIOUS KINDS OF CONTACT LENSES
THE HARD, SEMI-HARD or GAS PERMEABLE CONTACT LENSES
These contact lenses have the advantage of correcting high degree astigmatism and corneal irregularities. They are easy to put on the eye.
However, they are uncomfortable during the first three weeks of wear. Taking them off may be also difficult during the learning period.
The toric soft contact lenses correct mild to moderate astigmatism at the cost of initial mild discomfort and instability of vision.
Multifocal contact lenses can be prescribed to non-visually-exigent presbyopic patients.
LIFETIME OF CONTACT LENSES
Depending on their material, contact lenses should be discarded every day, 1 week, 2 weeks, 1 month, 3 months, 6 months, 1 year or 2 years.
From the medical point of view, the shortest use is the best. A short use avoids the complications due to the deposits that cover the lenses after some weeks of wear.
CONTACT LENS CARE
Usually, contact lenses are kept on the eyes from the awakening up until bedtime.
Contact lenses made of one- day-disposable or day-and-night-wear materials do not need any chemical care.
All the other kinds of material need to be cleaned, daily, with an antiseptic product and, monthly (unless they are monthly-disposable), by a proteolytic product.
Given that these products are, after an unpredictable time, a frequent source of irritation or intolerance, the daily-disposable contact lenses or the night-and-day-wear
(weekly-, 2-weekly-, monthly-disposable) contact lenses are preferred.
Although they have the advantages of avoiding the, potentially irritant, chemical cleaning products and decreasing the risk of infection (because the eye is touched only 8 times per month, instead of 60 times as it is the case of the monthly disposable daily cleaned lenses), the night-and-day-wear contact lenses are reserved to patients who are highly hygienic in their manipulations and very disciplined in respecting the duration of use of these lenses.