GP Lens Decisions
Learn how to figure out whether to fit from inventory or to order a lens.
JAMES A. BOUCHER, O.D., M.S., F.A.A.O. AND GARY M. POTEET, M.S., O.D.,
Two of the most important considerations practitioners must keep in mind when fitting a gas permeable contact lens patient are chair time and patient confidence. And unfortunately, choosing one means trading off on the other. Though fitting from a trial lens inventory increases initial chair time, it also increases patient confidence.
Make your inventory work
Fitting from a trial lens inventory increase the chances of getting the correct fit with fewer follow-up appointments. By observing the fit on the eye, you will learn whether the lenses satisfy your criteria. If they do, then you can dispense the lenses immediately. This helps to elevate the practice in the patient's eyes. There have been countless times when the patient exclaims, "You have the lenses here?!"
Here are some things to remember to achieve the optimal GP fit:
Every cornea is different. You will need to individualize the overall size, shape, eccentricity and corneal rigidity for each patient.
Lid configurations vary not only in shape, but also in tonicity.
Tear compositions differ -- according to age, gender, medications taken, allergies, etc.
Consider custom designs for all GPs to ensure the optimal fit, visual acuity and comfort. To do this, you must know the patient's refraction and corneal shape. Computerized corneal topography can assess shape factor with a customized computer GP design program, but slit lamp observations are still needed to assess lens dynamics and lid interactions.
Every lens is different.
Consultants at the Contact Lens Manufacturers Association (CLMA) member labs are there to help. The services they offer cover every existing GP contact lens. And the CLMA's Rigid Gas Permeable Lens Institute's
(RGPLI's) Web site (www.rgpli.org) offers fitting guides. The monthly online symposia (the second Tuesday of each month at 9 p.m. EST) is an excellent source for learning how to achieve the optimal fit.
Here's what you'll need
The ideal fitting situation is to have enough inventory lenses of known parameters, including base curve, overall diameters, peripheral curve radii and widths, to evaluate the trial lens on the eye based on initial empirical calculations and the closest available trial lens. Using a topical anesthetic before insertion of the trial lens increases patient comfort and consequently helps in the evaluation.
The advantage of using an inventory trial lens based on the empirical findings is that it provides information on lens dynamics. You can make modifications to the custom lens design based on the fit. To adequately assess trial lenses, the inventory should include conventional lens designs of 8.5-mm,
9.0-mm and 9.5-mm diameters, a macro trial set of a couple diameters and two or three keratoconus lens designs as well as a couple of variable geometry design lenses.
Know when to custom order
Custom ordering, on the other hand, decreases chair time. Sending the refraction, the keratometer readings and/or topographic maps to the laboratory is easy and efficient. When you dispense the finished lenses, you can, if necessary, modify or re-order them to solve any problems with fit or comfort.
Custom ordering is often necessary when the corneal toricity is more than 2.00D
(bitoric lenses) or there is significant lenticular astigmatism (front surface
toric). You should also order GP bifocal lenses; with these types of specialty lenses, it may be best to order them warranted.
The best results in less time
The bottom line: You can prescribe GP contact lenses with no more chair time than soft contact lenses, but with the benefit of better, more stable vision and healthier eyes.
DR. BOUCHER AND DR. POTEET ARE IN PRIVATE PRACTICE AT SNOWY RANGE VISION CENTER IN LARAMIE, WY.
CONTACT THEM AT (307) 742-2020 OR WWW.SNOWYRANGEVISION.COM.
Optometric Management, Issue: October 2003