Therapeutic use of contact lenses

 
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Contact lens conjunctivitis
Giant papillary conjunctivitis
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Therapeutic Contact Lenses

From the early part of the 1970’s, hydrophilic soft contact lenses have been used to rectify corneal edema and corneal epithelial defects. Contact lenses for therapy have the benefits of relieving pain and enhancing corneal epithelial healing. Through the years, lens materials with enhanced hydration and less thickness have been created to improve contact lens performance for therapeutic use.

The Aim of Treatment with Contact Lenses

The two major aims in the use of therapeutic contact lenses are relief of pain and corneal epithelial healing. Contact lenses can also help in wound stabilization, laceration, holes in the cornea and for bullous keratopathy, where besides pain reduction, contact lenses prevent secondary corneal infection and corneal vascularization. Prevention of corneal edema plays an important role in the betterment of epithelial adhesives in the later stages of corneal epithelium healing. Therapeutic usage may be as a non-surgical procedural treatment of corneal edema and corneal epithelial disease. As therapeutic contact lens wear involves an extended period of time, use of silicone hydrogel lenses is an improvement on any other kind of lenses.

Different Therapeutical Lenses for Different Conditions

Epithelial corneal indications may be acute, recurrent or chronic. Recurrent corneal erosions can occur in conditions such as abrasive trauma, epithelial basement membrane dystrophy, calcific band keratopathy, posthypertic keratitis. The symptoms include haziness, photophobia, discomfort and pain. These can be cured by bandage contact lens therapy.

Persistent epithelial conditions like filamentary keratitis, persistent epithelial defect, infectious or neutrophic keratopathy, trichias are treated with bandage contact lens therapy, which not only gives pain relief when the back surface of the cornea is elevated but improves visual activity as well. They can be used to reduce discomfort related to surface disorders like Thygson’s superficial punctuate keratitis and superior limbic keratitis.

Bandage Contact Lens Therapy

These are used mostly in the treatment of corneal ulcers that are infectious, trophic and autoimmune related. Atrophic corneal ulcers result in a continuous epithelial disorder with stromal ulceration, which leads to reduced corneal sensations and are non infectious.

Bandage lenses provide protection of healing the cornea so a hydrophilic, thick, low water content lens, which allows oxygen to permeate results in enhancement of stromal vuscularization to prevent further melting. Postoperative use of bandage contact lenses is beneficial in treating surgical conditions of the cornea and ocular surface. These also reduce the subepithelial scars and haze formation by shielding the bare underlying stroma from the persistent trauma of the eyelid. They can be used after cyanocrylate adhesive is applied for closing the corneal perforations sealing wound leaks. After glaucoma surgery, bandage lenses can be used to seal leaks and reduce bleb enlargement and prevent pain.

Gradual Improvement of Lenses

The first hydrophilic soft contact lenses, which were used as a bandage, were thick and made with low water content and low oxygen permeable materials. They were found to be successful in pain reduction and epithelial healing. With more modification and increased hydration and better design, the rate of success reached 71% and ultimately with the coming of hydrogel disposable lenses the success was high. With the development of the extra thin glyceryl methacrylate lens, the occurrence of giant papillary conjunctivitis was considerably reduced and the use of silicone elastometer lenses with extremely high oxygen permeability, the reduction of corneal vascularization can be achieved. The advent of silicone hydrogel material heralded the availability of the high oxygen permeability lenses, which had a stable post lens tear film resulting in less deposit formation and negligible tight lens syndrome.

Limitations to Therapeutic Lenses

Despite the improved rates of success in new high water content lenses, there continue to be drawbacks in their usage like the risk of infection, deposit formation, vascularization and development of giant papillary conjunctivitis. Occasionally a tight lens syndrome develops and leads to immobility of the lens leading to irritation and discomfort. The cause is attributed to water evaporation.

Silicone Hydrogel Lenses

Though silicone hydrogel lenses were not approved by the FDA as therapeutic lens, the clinical experiments performed revealed that the two silicone hydrogel materials that were used to produce contact lenses namely balafilcon A and lotrafilcon A when employed as a correcting medium succeeded in rectifying refractive error and extended wear modalities. Thus, with these new silicone hydrogel lenses, incidence of vascularization was zero and the incidence of infection is much less than in the case of low Dk lenses in extended and overnight wear.

It is seen that different lenses are used for different healing purposes. If the aim of therapy is to protect and heal the corneal epithelium, high Dk silicone hydrogels like balafilcon A and lotrafilcon or a very thin membrane like crofilcon. If the aim of the therapy is stimulation of stromal wound vascularization in addition to surface protection, a low water content thick hydrophilic lens should be chosen. People prone to misplacing lenses or requiring frequent replacement lenses should choose a daily disposable moderate water content lens. The options nowadays are wider than ever before.