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There are eye complications, which result from deteriorated contact
lens quality. One reason for deterioration of lens quality is
careless handling of lenses causing spoilage and damages. Quality
deterioration could also result from natural wear and tear or
natural ageing of contact lenses. The factors that affect lens
quality are spoilage, deposits on the lens, warpage and damages.
Spoilage
Spoilage in contacts is due to factors such as tear chemistry,
cleaning and disinfecting techniques, the contact lens material
and contaminates in the environment. Spoilage is more common in
soft contacts and therapeutic lenses than in RGP lenses.
Spoilage is of many kinds. These are organic, inorganic, mixed
deposits, microbial contamination, contact lens defects and ageing
of contact lenses.
Spoilage results in problems such as poor visual clarity due
to loss of transparency, uneven surface and poor wetting of lenses
leading to increased discomfort. Some other complications are
poor fitting resulting from altered lens dimensions, eye problems
due to lens deposit and reduced oxygen flow through the lens to
the cornea. Serious situations arise when sometimes lens spoilage
leads to eye inflammation and severe allergic reactions like the
giant papillary conjunctivitis.
Lens deposits
The main constituents of lens deposits are proteins and lipids.
These are natural and unavoidable deposits, which are formed on
the lenses by the interaction of the tear proteins and the contact
lens. The denatured protein, which constitutes most of the total
protein deposits, clouds the lenses. Lipids are gland secretions
which rub off on the contacts giving them a greasy appearance.
These deposits, rub against the eye causing eye complications.
Deposits also change the fit, oxygen permeability, surface and
edge quality of the contacts. They also make the lens tighter
and interfere with tear flow. Furthermore, they reduce comfort,
visual acuity and wearing time besides causing burning and irritation.
An interesting observation has been the incidence of less protein
deposits and more lipid deposits in silicon-hydrogel lenses compared
to disposable hydrogel lenses. The significance of this difference
has eluded clinicians.
Environmental contaminants like dirt, dust, smoke, oils and make-ups
can also coat the lenses.
Deposits can form within hours or can occur after months and
have been seen to be more common in those having dry eyes, blepharitis,
poor tear quality and abnormal blinking.
A good cleaning regimen should be able to remove the deposits.
Wearing daily wear disposable contacts may be tried out since
the incidence of deposits with these lenses is significantly lower
as compared to soft contact lenses. In case of persistent deposits
the RGP lenses may be worn.
Warpage
In contact lens warpage, the curvature of the lens is changed
from its original parameter. Such alterations of the curvature
are often caused by exposing the lens to excessive heat such as
rinsing them in hot water or placing them near a source of heat.
The RGP lenses change their curvature when they are squeezed too
hard by the fingers during cleaning. Changed curvature leads to
poor fitting and causes several eye problems.
One of the more serious fallout of lens warpage is corneal warpage.
The warped lens, as it were, molds the cornea to its own distorted
shape giving rise to what is known as induced irregular astigmatism.
The complication results in, poor vision with contact lens which
worsens with time, frequent changes in lenses, and sometimes an
irritated red eye. The corneal warpage should be evaluated with
a keratometer or a corneal topographer. Corneal warpage is more
common with hard PMMA lenses than with RGP or soft contact lenses.
The only treatment is discontinuation of contact lenses but it
may take weeks or even months for the cornea to regain a regular
and stable shape. Meanwhile during the interim period the patient
may wear RGP lenses. Contacts may be worn again if the cornea
has a stable shape. In case corneal warpage persists then wearing
of glasses or refractive surgery may be needed.
Damages
Contact lenses are sometimes damaged during manufacture or due
to careless handling. Damages produce tears, cracks and chips
on the lenses which can cause eye irritations. Depending on where
the damage is, patients may or may not have symptoms. Some of
the symptoms are ocular injection, foreign body sensation, tearing
and blurred vision. Additionally bacterial organisms may enter
the cracks caused by damages and intensify any existing complication.
Treatment includes removal of the affected lens and instructing
the patient on proper lens handling. Lubricant treatment may be
done if the corneal epithelium is affected. Antibiotic use should
be rare.
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