Therapeutic Contact Lenses

Robert Terry

Robert Terry graduated from the University of New South Wales with a Bachelor of Optometry in 1980. Over the following five years he worked in clinical practice in England before returning to Australia. In 1995 he was awarded a Master of Science degree from UNSW for research work undertaken at Cornea and Contact Lens Research Unit investigating the effect of rigid gas-permeable lens wear on the human corneal touch threshold.

Since 1985, Rob has worked as a Principal Research Optometrist and Manager of Clinical Education at the CCLRU and has been involved in many Contact Lens Education Programs conducted by CCLRU. Currently he is part of the Professional Education Team at the Vision Cooperative Research Centre.

At present he is the Chairman of the Contact Lens Society of Australia (NSW Division) and is a member of the British Contact Lens Association (BCLA) and the International Association of Contact Lens Educators (IACLE). In 1993 he was made a Fellow of the American Academy of Optometry.

Ambroziak AM, Szaflik JP, Szaflik J. Therapeutic use of a silicone hydrogel contact lens in selected clinical cases. Eye Contact Lens. 2004 Jan;30(1):63-7.

Szaflik JP, Ambroziak AM, Szaflik J. Therapeutic use of a lotrafilcon A silicone hydrogel soft contact lens as a bandage after LASEK surgery. Eye Contact Lens. 2004 Jan;30(1):59-62.

Department of Ophthalmology, University of Warsaw, Poland

Introduction

Therapeutic contact lenses, sometimes known as ‘bandage’ lenses, are special contact lenses worn for therapeutic reasons, e.g. treatment of a corneal or anterior eye disease. Although therapeutic contact lenses can be used to correct refractive error, and in some cases enhance drug delivery to the cornea, they are used primarily for physical therapeusis, mechanical eye protection, and as an aid to healing (Table 1).

Therapeutic lenses are particularly useful for post-surgical management of patients because surgery of the cornea and other ocular structures (epikeratophakia, cataract surgery, corneal epithelial debridement) requires a period of healing to allow time for cell growth and adhesion. Therapeutic contact lenses aid the healing process by protecting new corneal cells in situ from the action of blinking eyelids. This allows cellular adhesion and tissue relationships to develop normally. As therapeutic lenses provide a smooth interface between the cornea and lids, they can also protect the lids from sources of irritation such as suture knots.

The materials used for therapeutic contact lenses are hydrogels, silicone elastomers, collagen, and gas permeable (GP) polymers in the form of scleral (‘haptic’) lenses. Typically, hydrogel lenses are the lenses of choice because their large diameter ‘bandages’ the entire cornea and their soft, supple nature contributes to enhanced wearer comfort. However, hydrogel lenses dehydrate on the eye and the resulting water movement across the lens may result in water being drawn from an edematous cornea. This water movement may also challenge an eye that is already tending to be ‘dry’.

Additionally, the relatively low Dk of common hydrogel lens materials may induce corneal oedema if the lenses are not thin enough. Often, a mid-water content (approximately 50 - 60%) disposable hydrogel lens may be a good choice for parameter, design, and comfort considerations but also because it allows frequent lens replacement at minimum cost.

Silicone hydrogel lenses made from materials of high oxygen permeability (Dk) have been available since 1998 and are approved for therapeutic use in Europe and in the US. These lenses have the advantages of a typical hydrogel lens in that they provide excellent comfort and provide the practitioner with an opportunity to fit a therapeutic lens that has very high oxygen transmissibility.

Paper Reviews

The two papers from the Department of Ophthalmology at the University of Warsaw, Poland and published in Eye & Contact Lens present results from prospective, open and nonrandomized clinical studies examining the application of silicone hydrogel lenses for therapeutic use.

Ambroziak et al. fitted 70 eyes of 70 patients with anterior segment conditions for which therapeutic lenses were indicated. The majority of these conditions were bullous keratopathy (47), followed by postoperative keratoepitheliopathy (14), recurrent corneal erosions (5) and dry eye syndromes (4). Patients were fitted with a silicone hydrogel soft contact lens that was worn continuously for 7 to 30 days, and concomitant therapies were used.

Of 70 eyes, 64 (91%) showed improvement in the clinical condition of the eye (no improvement was seen in 6 cases of bullous keratopathy). The eyes of all patients with dry eye improved and in 3 of the 4 patients, the cornea healed completely. For comfort, 66 eyes (94%) were rated as very good or good and none rated comfort as poor.

In their companion paper, Szaflik et al. conducted a clinical trial involving 30 patients treated with unilateral LASEK. LASEK involves the creation of an epithelial flap that is folded away before the excimer laser ablation and put back afterwards. In this study, LASEK patients were fitted with a silicone hydrogel soft contact lens that was worn continuously for 3 to 4 days post-operatively.

The condition of the corneal epithelium after contact lens removal was rated as good to very good in 86% of eyes and an average of 77% of subjects reported good or very good comfort during the wear period. On average, post-blink lens movement was rated as good or very good in 73% of eyes during follow-up and none of the lenses were associated with excessive movement.

Discussion

Overall, the results from both studies indicate that high-Dk silicone hydrogel lenses are an effective and well-tolerated bandage lens for anterior segment disease and for post-operative management of LASEK patients. The studies were not designed to compare the effectiveness of silicone hydrogels with other lens types therefore it is not possible to conclude whether silicone hydrogels perform better as therapeutic lenses. However, silicone hydrogels deliver the benefits of a hydrogel lens with the addition of very high oxygen transmissibility. This allows practitioners to prescribe extended wear during treatment and potentially creates a healthier environment during healing.

The basic fitting criteria for silicone hydrogel bandage/therapeutic lenses are the same as with any other hydrogel lens fitting. The lenses must centre well and move adequately and the patient must be comfortable. For bandage lenses, vision should be no worse than with no lens at all. Obviously, if better vision can be achieved, it should be pursued.

A ‘one size fits all’ approach to fitting should be avoided and lens design/parameters selected to optimize on-eye lens performance. Attention to detail in the fitting relationship and fitting performance may be particularly critical for a compromised eye. Oddly shaped or ‘degenerating’ eyes may lead to an unpredictable fitting relationship in which lenses cannot be fitted satisfactorily.