Corneal complications from contact lenses

 
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Contact Lens Induced Corneal Complications

Of all the users of contact lenses in the U.S. about 6% experience contact lens related complications yearly. Wearing of contact lenses causes alterations in corneal physiology, which in turn leads to epithelial, stromal and endothelial damages, disorders of the ocular surface and can aggravate already present complications. Complications range from practically harmless allergic conjunctivitis to the adverse microbial keratitis. Other associated disorders are giant papillary conjunctivitis, corneal edema or hypoxia, neovuscularization, limbal keratoconjunctivitis, sterile infiltrates, red eye and tight lens syndrome.

Causes

All kinds of contact lenses affect the health of the eyes to some extent leading sometimes to complications. However, RPG lenses have less adverse complications compared to soft lenses used for daily wear or extended hydrogel lenses. Contact lenses are found to be the most significant cause in the development of the extremely serious and damaging microbial keratitis.

These disorders are caused by the failure of contact lens maintenance systems, and patient related reasons like non-adherence to wearing schedules. Pre existing complications aggravate the problems but are not a cause of these.

Microbial Keratitis

This is the ultimate corneal damaging complication associated with contact lens usage and is distinguished from other forms of harmless sterile infiltrates. Microbial keratitis is serious to the extent that it can lead to permanent loss of vision due to scars and perforations in the cornea. Though the occurrence of this disorder is low, its high morbidity makes it a serious cause for concern. In a study it was found that for every 10,000 persons using 1.1 suffer from it annually. The figures in the case of daily wear contacts and extended wear contacts are 3.5 and 20 respectively pointing to the fact that extended wear contact lenses leads to the highest incidence of microbial keratitis compared to any other modality.

The organisms responsible for the development of microbial keratitis are the gram-negative Pseudonomas aeruginosa as well as the gram positive Staphylococcus. Corneal hypoxia and the adherence of organisms on the corneal epithelium particularly in the case of extended wear lenses are risk factors. Also improper care and use of lenses play a significant role. Thus, epithelial damage and exposure to pathogenic bacteria are major factors in the aggravation of microbial keratitis.

The infiltrates are larger than 1.5mm, stromal and have a whitish overlying epithelial defect. Patients experience moderate to severe pain, foreign body sensation, photophobia, and tearing. The anterior chamber of the cornea shows moderate to severe activity.

Therapy includes broad-spectrum topical fortified antibiotics that should be started without delay. For milder cases, monotherapy with fluoroquinolone is advised. Therapy is initiated after the responsible organism is identified and return of sensitivity. The results of microbial keratitis are corneal scarring, sometimes irregular astigmatism and low visual acuity and some patients require corneal transplantation to improve visual acuity. Contact lenses can be used again after healing but in accordance to the instructions given y the doctor. Daily wear RGP lenses caned vision be used by patients experiencing irregular astigmatism can improve vision.

Hypoxia or corneal edema

Hypoxia occurs when sufficient oxygen does not reach the cornea due to contact lens imermeability. Decrease in the levels of oxygen in the cornea mainly to the endothelium and the stroma results in change of metabolic activity and stromal swelling. Tight lenses, Dk lenses, PMMA’s or extended wear of regular hydrogel lens are sources of hypoxia, which in turn leads edema either chronic or acute.

In acute edema, microcystic epithelial changes occur and with further advancement can lead to cell death and imbalance of traumatized epithelial cells. Symptoms include extreme pain, tearing, reduced vision, photophobia and intolerance of contact lens wear.

Chronic edema occurs with extended contact lens use and the symptoms and findings are subtler. Presence of epithelial microcysts, thickening of stroma, endothelial blebs with hypoxia and neovascularizaton develop. There is no extreme pain and vision is affected minimally. The treatment for hypoxia mainly involves the termination of contact lens wear until edema is resolved. Lubrication and topical steroids can be used. After healing, patients can use a flat high oxygen permeable lens.

Tight lens syndrome

Hydrogel lenses with high water content results in the steeping of the base curve and leads to contact lens tightening and drying. This occurs when the lens has been on the eye surface for some time. The symptoms include irritation, pain, photophobia and blurred vision. There is conjunctival injection and corneal staining, epithelial damage, infiltrates, anterior chamber reaction. There is negligible movement of the lens on blinking. There is the dragging of conjunctival vessels on the edge of the contact lens wear, use of topical antibiotics and cyclopegic agents, topical steroids to decrease inflammation. Once healed, patients can be fitted with a flat high oxygen permeable lens.

Red Eye

This manifests itself as acute red eyes due to corneal infiltrates. When the eye is closed toxins from bacteria are activated resulting in inflammatory response. Symptoms include ocular discomfort, foreign body sensation and redness of the eye on awakening. There is presence of conjunctival injections, mild chemises, anterior chamber reaction. The treatment involves termination of contact lens wear till complete healing, which usually occurs within two weeks of therapy and no medicines are prescribed. However, this condition can recur if extended wear lenses are used again.