the contact lens exam
Prosthetic Soft Lens Basics
BY DAVID KADING, OD, & JENNIFER L. SMYTHE, OD, MS, FAAO

The recent explosion in direct-to-consumer advertising and the availability of cosmetic tinted contact lenses have generated interest in our practice for using tinted lenses to mask ocular disfigurement. The goals of prosthetic lens fitting vary from improving appearance to enhancing vision or visual comfort.

Prosthetic lenses require a systematic fitting approach with additional testing. In some cases this falls under a therapeutic evaluation that medical insurance may cover under CPT Code 92070, accompanied by a contact lens "V" code and a diagnosis code to indicate medical necessity.

Pre-fitting Points of Discussion

The first step is to set realistic expectations. It's imperative to elicit as much information from the patient as possible regarding both cosmetic and visual goals.

When reviewing prosthetic lens options, explain that it may not be possible to perfectly match the "good eye" in all situations and environments. The lens performance and aesthetics are dependent upon lighting conditions, pupil size and glare. As with any specialty lens, outlining the drawbacks and being realistic about expectations prevents potential frustration or disappointment after the fitting process has begun.

Fitting Pearls

Add digital photography, corneal topography, and pupil and corneal/iris diameter measurement to your normal contact lens exam. In the case of a disfigured but seeing eye, you can use a detailed refraction and possibly a GP lens over-refraction to determine the visual acuity potential.

You can piggyback a hyper-Dk GP lens over a prosthetic soft lens to correct irregular astigmatism. Perform corneal topography or keratometry over the soft lens and then select the GP lens parameters based on the curvature over the prosthetic lens.

Figure 1. A prosthetic lens improved the appearance of this disfigured eye.

Color Matching

Iris color varies dramatically with changes in lighting conditions, head position and eye movement. Although it's difficult to perfectly match the color of the good eye, a digital camera can aid in the process. Capture the following images: Close-up shots of the affected eye, unaffected eye and the two eyes together, plus a full-face photo. Take all of the images with and without a flash to simulate bright and dim illumination.

Follow up and Fine-tuning

You can refine the color and fit after you allow the dispensed lenses to equilibrate. To problem solve color variations, repeat the photography protocol with the lenses on under varying light conditions with and without a flash. You might consider prescribing an opaque cosmetic lens for the "good eye" to more closely match the prosthetic lens color. In a light-eyed patient, the normal eye may need a darker opaque lens to resemble the prosthetic lens.

Finishing Touch

A final tip is to prescribe non-AR coated polycarbonate spectacles to wear with the contact lenses. These protect the eyes, and the glare from the lens surface helps camouflage any irregularities in color or shape matching.

Dr. Kading completed a cornea and contact lens residency at the Pacific University College of Optometry and is now in private practice in Bellevue, Washington. Dr. Smythe is an associate professor of optometry at Pacific University and is in private group practice in Beaverton, Oregon.

Contact Lens Spectrum, Issue: October 2005