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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.
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