CONTACT LENS INFECTIONS

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

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