the effects of damage to contact lenses


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Damage to Contact Lenses

While contact lens safety improves as contact lenses improve, certain problems can arise from deteriorated lenses. Normal wear and tear, natural aging or poor handling of the lenses can cause deterioration. Factors affecting lens quality are damages, spoilage, deposits and warpage.

Contact lenses can be damaged due to careless handling or manufacture defects. Damages include tears, cracks or chips on the lenses. Occasionally the damage is so minimal that no symptoms result. Symptoms may be minor as in tearing, blurred vision, ocular injection, or the feeling something is in the eye. However, the cracks and chips can allow bacteria to enter the eye causing more severe symptoms.

Treatment of problems resulting from damaged lenses is to remove the damaged lens. It is replaced if necessary. If the cause is poor handling, the patient is re-instructed in proper lens care. Lubricant may be used if the corneal epithelium has been affected. In rare cases of bacterial infection an antibiotic is used.

Spoilage is more common in soft contacts than Rigid Gas Permeable (RGP) lenses. Spoilage can be the result of unstable tear chemistry, poor cleaning and disinfecting techniques, environmental contaminants or the contact lens material itself.

Spoilage can result in eye discomfort due to an uneven surface, poor wetting of the lens or poor fitting. It can also result in poor visual clarity. Corneal problems can result due to lens deposits or decrease oxygen flow. Lens spoilage can also lead to eye inflammation and giant papillary conjunctivitis.

Deposits found on contact lenses are primarily proteins and lipids, which are formed naturally in the eye and are deposited on the lens. Protein deposits cloud the lens and lipid deposits make them seem greasy. Dirt, dust, oils, make up, and smoke can all deposit on the lenses.

These deposits on the lens can change the fit, surface edge quality, oxygen permeability, and alter tear flow. All these will cause burning, irritation, and decrease visual acuity. Proper cleaning should remove all deposits. Daily wear disposable lenses can solve the problem, or RGP lenses may be worn.

When a contact lenses warp, the curvature of the lens changes. This can be caused when a lens is exposed to excessive heat, i.e. hot water, or being stored near a radiator. Rigid Gas Permeable (RGP) lenses can be warped if they are squeezed too hard. Warped lenses can lead to eye problems.

One of the most serious problems lens warpage can cause is corneal warpage. The cornea molds to the shape of the warped lens, this is known as induced irregular astigmatism. It is most common with hard PMMA lenses. This warpage results in poor vision even with contact lenses on, irritated red eye, and frequent lens changes. Corneal warpage is usually evaluated with a keratometer or corneal topographer.

Treatment of corneal warpage is discontinuance of contact lens wear. Corneal correction may take up to several months. Once corrected contact lens use may be initiated again. However, if corneal warpage persists glasses or surgery are required.

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