Prescribing GP Contact Lenses for Ocular Diseases
These lenses offer therapeutic benefits to diseased and traumatized eyes.
By Barbara Anan Kogan, O.D.; Ann Laurenzi, O.D.; Vishakha Thakrar, O.D.; and Jill Beyer, O.D.

GP scleral contact lenses provide not only visual rehabilitation in eyes with corneal ectatic diseases or irregular corneal astigmatism, but can also provide therapeutic benefits to eyes with ocular surface disease (OSD).  Severely diseased eyes are in need of mechanical protection, surface hydration and sufficient oxygen supply to allow physiological repair.

Ocular manifestations of OSD may present as lid edema, keratinized lid margins, cicatricial entropion,ectropion,trichiasis, symblepharon, epithelial defects, infection and corneal vascularization. Initially, management may involve patching, lubrication and soft contact lens extended wear.If the disease is progressive, it may lead to tarsorrhaphy and ocular surface reconstruction surgeries such as limbal stem cell transplantation and amniotic membrane grafting.

Therapeutic properties

An alternative or adjunctive therapy would be to fit a GP scleral lens, because their therapeutic properties may benefit the hostile external ocular environment created by OSD. Contact lens materials have evolved and scleral lenses now can be made of highly oxygen permeable materials. The Dk/t values to avoid epithelial and stromal are between 87 Dk/t and 125 Dk/t for overnight wear, according to Holden and Mertz and Harvitt and Bonnano. These materials avoid induction of hypoxic complications and, with sufficient oxygen, allow mitosis of the epithelial cells enhancing physiologic repair. The lens protects the migrating epithelium from mechanical insult of the lids and external ocular environment; this allows earlier attachment of the basal epithelial cells to the basement membrane and promotes corneal epithelium healing.

Scleral GP designs for optimal healing

The large diameter of the lens, typically 15.0mm - 24.0mm, provides effective protection of the entire cornea from keratinized lid margins, entropion and trichiasis. It fits under the upper lids and results in less lid sensation and a more comfortable fit than a corneal GP lens. The scleral contact lens, acting as a barrier, may provide better protection than patching or tarsorrhaphy and not cause mechanical friction between the eyelid and corneal epithelium. The contact lens completely vaults the cornea and limbus, entirely supported by the sclera, which negates corneal interaction of smaller diameter corneal GP lenses. This fit also maintains a constant aqueous interface by retention of a pre-corneal tear layer, hydrating the cornea in severely diseased and dry eye conditions.

Case in point

A 75-year-old white female with a five-year history of Sjogren's syndrome and related keratitis sicca, presented with recurrent epithelial defects and corneal ulcers OU. Prior management included large bandage hydrogel contact lenses, artificial tears, antibiotic treatment and tarsorrhaphy. Her best-corrected visual acuities were OD 20/40 and OS 20/50 and applying artificial tears every two hours OU. External ocular examination revealed punctate epithelial erosions (PEE) spread diffusely across the cornea, corneal edema, central scarring, deep stromal neovascularization OU and moderate conjunctival injection.

The initial daily wear scleral lens, which was fit on the left eye, vaulted the cornea and limbus, thus creating a tear reservoir to provide constant corneal hydration. After two months of wear, the PEE's and corneal edema resolved, bulbar conjunctiva quiet and OS best corrected visual acuity improved to 20/30. She currently wears the lens comfortably on a full-time basis and no longer uses artificial tears while the lens is on the eye, though she uses Restasis b.i.d to reduce mucous production. A scleral lens is currently being fit in the patient's right eye.

GPs to the rescue: Fitting the post-trauma eye

Utilizing GP (oxygen permeable) contact lenses on post-trauma eyes is an easy practice-building strategy. Consider that an estimated 2.4 million ocular traumas occur in the United States per year; whether these patients come to your office through ophthalmology or self referrals, they are seeking to gain any visual improvement possible. This is an opportunity for your practice to differentiate itself from the crowd -- you will often return the first real sign of visual improvement when you dispense the lens, and finally the patient experiences a little overall relief.

GPs for corneal irregularities

An overlooked area of post-trauma eyes is the occurrence of corneal irregularities due either to the initial trauma or subsequent surgeries. Here, the GP lens is clearly the treatment of choice. Topography or keratometry verifies or denies the presence of irregular corneal astigmatism, and the average topography on the affected eye or keratometry of the fellow eye provides an excellent starting point for the initial diagnostic lens curvature. Quite frequently, the first lens placed on the eye is the final selected base curve. More often than not, a spherical GP will do the trick. You'll need a specialty toric GP lens if the trauma has left significant orthogonal astigmatism in addition to the minor irregularities. Additionally, secondary scarring may result in steepening that resembles keratoconus on occasion; in these specialty cases, a keratoconus design is in order.

With a surprising prevalence of aphakia occurring in post- trauma eyes, GPs provide excellent oxygen permeability through thick, powerful aphakic contacts while still correcting minor corneal irregularities. Lens material is a balance a maximum oxygen permeability and keeping the specific gravity as low as possible to minimize inferior decentration and discomfort. If necessary, the lenses for aphakia may be fit slightly steeper than typical GPs to facilitate centration. However, be sure to compensate by flattening the peripheral curves thus maintaining adequate tear exchange in these instances.

Routinely measure mesopic pupil size on aphakic eyes to assist in selecting the optimal lens optic zone (OZ). The OZ should be large enough to prevent haloes and glare, yet small enough to minimize lens weight and decentration. Remember that these patients now lack a natural lens, so request UV absorption on your GP lens to minimize ultraviolet ray damage.

GPs for pupil irregularities

Pupil irregularities are a common occurrence on eyes that have suffered trauma. If the pupil is irregular and fixed, then light sensitivity may be another added complication. Requesting a dark tint to the GP lens can easily treat minor glare issues. However, for iridodialysis or large fixed pupils, a soft lens with iris occlusion significantly decreases photophobia and eliminates the need for constant use of sunglasses. To go a step further, just piggyback your custom made GP on top of the soft lens and the refractive issues are neutralized. This method also provides the benefit of minimizing costs. Minor changes can be made to the GP lens while the non-refundable iris occlusion soft lens need not be changed.

Choose the right solutions

"Many ocular complications associated with compliance-related issues often occur from one-bottle cleaning and disinfectant solutions," Keith Parker, VP of Operations of a Colorado-based laboratory specializing in custom-designed GPs for compromised corneas, says. Parker continues to explain: "Some disinfecting and storage systems are different from others. The Optimum Solution calls for lenses to be soaked overnight in a cleaning, disinfecting and storage solution. In the morning, this solution needs to be thoroughly rinsed with saline or water (if appropriate) leaving the lens surface clean, creating a healthy, comfortable lens. Applying a wetting insertion drop on a clean lens works well without leaving a filmy lens surface." One leading soft, GP and IOL material manufacturer provides a one-year warranty on the performance of its GP materials if this solution is used.

Some care systems' protocol includes rubbing a cleaning and disinfecting solution on the lens in the palm of the hand for a few seconds prior to storing in a so-called conditioning solution. How clean your patient's hands are, or what kind of lanolin soap they use, may determine how clean the lens surface is before storing it in a conditioning solution. If the lens surface is not clean, no conditioning will take place. Often the cleanser residue or hand soap/lotion contaminants render the lens surface filmy, causing poor lens performance. All-in-one systems may appear simple, but the results often yield ocular complications, as they are less effective. Most all-in-one solutions suggest an "extra strength" solution or an "extra enzyme" to maximize their effectiveness.