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Though contact lenses can rectify several refractive problems
and improve vision, it has become certain that some types of contact
lens usage like overnight use of soft lenses is associated with
serious infectious bacterial keratitis in some patients. Nearly
two thirds of contact lens related ulcers was caused by P.aeruginosa
bacteria and was found in patients who were using extended wear
contacts. Later, contact lens wear was established to be the primary
cause behind infectious keratitis in the group corneal ulcer kind
of complications and outdid even trauma.
The risk of corneal infection was about 10 to 15 times higher
in users of soft lenses on an extended wear as compared to daily
wear basis. The occurrence of infectious ulcerative keratitis
with extended wear was 20.9 cases in 10,000 patients while the
figure was 4.1 per 10,000 patients for daily wear usage.
Causes of Infection
The sources of bacteria and peroculor disease results in contact
lens contamination and patients already having blepharitis or
dry eyes are more prone to bacterial colonization leading to infection.
The other sources of bacteria were found to be improper hygiene
amongst users and contamination of contact lens solutions and
cases lead to infection. In some instances the contact lens was
found to develop pathogens on its own. Thus, improper lens care
was a major factor in the development of infectious keratitis
with contact lens wear.
P.aeruginosa bacteria readily adhered to contact lens deposits.
This complication led to the necessity for developing disposable
and frequent replacement contact lenses as these were thought
to be less prone to develop microbial biofilm.
P.aeruginosa keratitis is a serious disorder of contact lens
wear as this leads to fast coagulation of corneal tissue and can
even lead to corneal perforation. Thus, it is the cause of vision
loss with a few patients using contact lenses.
Contributing Factors
Studies have shown that pattern of lens wear and not the type
of lens used was a consideration for ulcerative keratitis. Daily
wear of disposable soft lenses was the least risky and overnight
wear increased the risk of manifold. Users of disposable and conventional
extended wear lenses had the same risk for ulcerative keratitis.
However, sterile keratitis was more common with extended wear
disposable lenses whereas conventional reusable extended wear
was associated with the more adverse culture positive ulcerative
keratitis.
Another factor for ulcerative keratitis was that of oxygen transmissibility.
Disposable soft lenses also were not able to transmit oxygen than
did conventional extended wear lenses and led to many epithelial
aeruginosa adherences. It was seen that aeruginosa was more prone
to bind to exfoliated corneal epithelium when lenses of low Dk/f
were used. However, hyper oxygen transmissible lenses for extended
have brought about considerable improvement and the rate of microbial
keratitis is much less than in the case of disposable hydrogel
lenses and the occurrence of corneal hypoxia was also negligible.
Fungal Keratitis
This occurs with high water content hydrogel lenses and is more
common in humid climates where fungal organisms are more prevalent.
Also with therapeutic contact lenses this can occur. Fungal keratitis
is present as a superficial dirty grey colored feathery infiltrate
with satellite lesions in the periphery of the corneal infiltrate.
Excessive inflammation is there. This infection was reported with
daily disposable soft lenses. For prevention, proper lens care
should be taken.
Acanthamoeba keratitis
Acanthamoeba is free-living pathogenic protozoa and is found
in the soil, dust and contaminated water or may be airborne. This
infection was largely in case of persons wearing soft daily wear
lenses and used homemade saline, did not take proper care of lenses
and swum with lenses on. Initial invasion of the corneal epithelium
and a secondary epithelial phase of infection occur. Infection
invades deeper into the corneal tissue and can even progress into
the sclera. Treatment is a prolonged process and topical steroids
are given in combination with topical antiamoebic therapy. The
prevention includes avoidance of non-sterile solutions, tap water
either to rinse lenses or the case. Proper disinfection is also
important.
Sterile Corneal Infiltrates
This may occur due to preservative reaction, immune reaction,
toxic reaction or hypoxia. Patients can be sensitive to preservatives
used in contact lens solutions. The complaints are of burning,
itching and decreased lens wearing time. Sterile Corneal infiltrates
have been reported with the use of disposable contact lenses,
which are generally located in the periphery. There is increased
pain and discharge. Patients suffering from corneal infiltrates
are to be treated with topical antibiotics and if necessary later
with topical steroids.
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