contact lens Q&A

Fitting Contact Lenses Following LASIK

BY DAVID I. GEFFEN , OD
OCTOBER 1998

A frequently asked question is, "What type of contact lenses are doctors using on post-LASIK patients?" To fully answer this question, we must approach it as two issues.

How do you fit patients who have normal postop results?

ANSWER: Patients who need contact lenses after a laser in situ keratomileusis (LASIK) procedure are typically undercorrected or overcorrected and need a temporary solution until an enhancement procedure is performed. Another type of post-LASIK patient who may benefit from occasional contact lens wear is the monovision patient.Those who choose monovision may need binocular correction for high distance-demand activities.

Fortunately, most everything in your contact lens arsenal works for these patient types. If astigmatism is a problem, toric soft lenses will usually work. Don't be deceived by the flat central keratometry readings on astigmatic patients. Remember that only the central 6.0mm have been flattened by the laser. Soft lenses will usually fit well due to the normal peripheral corneal curves, but watch for central bubbles and adequate lens movement.

Keep in mind that you can easily use rigid gas permeable (RGP) lenses with astigmatic patients. I recommend using large diameter lenses of at least 10.0mm. The lens will vault over the central 6.0mm, so prescribing an adequate contact lens material is required to maintain a good fitting relationship in the periphery. Design the RGP lens according to your personal preference, although standard tricurve designs work very well.

How do you fit patients who have postop complications?

ANSWER: The more difficult situation is the rare patient who has complications with surgery. Complications that typically require contact lenses for treatment are irregular astigmatism, excessive glare and displaced ablations.

Irregular astigmatism is the most common complication of LASIK, which can cause a reduction in two to four lines of visual acuity and occasionally even more. These patients cannot be refracted and acuity cannot be improved to preop levels. RGPs are the best choice and will usually correct the acuity to close to the preop level.

Patients with excessive glare problems were probably poor candidates for surgery to begin with. Proper patient screening should prevent this problem. In cases of excessive glare, the only satisfactory choice is prescribing very large diameter RGP contact lenses.

Displaced ablations appear to be extremely rare. However, if you encounter such a case in your office, you'll most likely end up fitting an RGP. Due to the decentered optics, manage this patient similarly to how you manage a patient who has irregular astigmatism. Work with a lab that has a good warranty policy because you may need to make several changes before the end product.

I prefer the new generation aspheric periphery lenses in mid to high Dk materials. The aspheric periphery allows for a good bearing relationship in the mid and peripheral cornea. The central zone will vault due to central flattening. The tear lens will fill in the central zone to negate any irregularities. Make sure to see the patient after four or more hours of contact lens wear to observe any adherence or tightening of the lens. Adequate tear flow is a must for good comfort and corneal physiology.

I feel that trial fitting is mandatory for patients with displaced ablations due to the unpredictability of the fitting relationship, so be sure to have a useful trial set in your office. Topography is very helpful in determining the starting trial lens.

Dr. Geffen is in a joint refractive surgery practice in San Diego, Calif. He is also a consultant for Infinity Optical.