Corneal (R)GP lenses after LASIK - do they work?
Stephanie L. Woo OD FAAO FSLS
LASIK surgery or other refractive surgery procedures can leave many myopic patients with an oblate-shaped cornea. This oddly shaped cornea can be difficult to fit, especially when using corneal gas permeable (R)GP lens designs. The pre-surgical keratometry values and prior refraction information can be quite useful when attempting to fit these types of corneas. Any information about the ablation zone (diameter of treatment zone) can be helpful as well. If you do not have any of this information, a diagnostic fitting performed within the office often yields great results.
A 57-year-old white female presented to the office on January 2, 2014. She was a new patient with history of myopia OU and LASIK performed OD only in 2000. She had previously worn (R)GP lenses prior to LASIK surgery. She had also attempted soft contact lens wear in the past, but did not like them because of removal issues. Her goal was to see more clearly at distance with a GP lens for the right eye only.
BCVA: OD -2.00-0.75x090 20/40, OS -2.50-0.50x091 20/25
The axial and elevation topography maps were taken into consideration before selecting a diagnostic lens (Figures 1 and 2, below).
Figure 1 + 2: Axial map (top) and Elevation map
A reverse curve diagnostic fitting set was utilized, and the first lens was selected (following the manufacturer’s fitting guide) had the following parameters:
Lens 1: 8.0/ -4.00/ 10.0 OAD/ 8.00 OZD/ 7.60 (0.4mm) / 11.50 (0.2mm)
Figure 3: drastic edge lift and maximum peripheral clearance
This lens demonstrated inferior nasal touch and pooling superior temporal. There was midperipheral bearing, which required a steeper secondary curve. There was also drastic edge lift and maximum peripheral clearance (Figure 3), so the edge needed to be steepened as well. Making these two simple changes the altered the fit of the lens.
Lens 2: 8.0/ -3.50/ 10.00 OAD/ 8.0 OZD/ 7.30 (0.4mm)/ 10.50 (0.2mm)
The lens was now aligned fairly well with the central and midperipheral cornea. Although the lens positioned slightly inferiorly, it was fairly stable, and the patient reported good comfort. The edges were also very well aligned with average peripheral clearance (Figure 4). With an over-refraction, the patient achieved 20/25 visual acuity and was pleased with the vision. She has been wearing the lens successfully for over 3 months.
Figure 4: well aligned edges with average peripheral clearance
Fitting post-refractive surgery patients with corneal GPs can be easy and rewarding. If a reverse curve fitting set is available, performing a diagnostic fit in office can produce a great contact lens fit.
Dr. Stephanie L. Woo graduated from the Southern California College of Optometry and completed a Cornea/Contact Lens residency at the University of Missouri - St. Louis.
She is a Fellow of the American Academy of Optometry and a Fellow of the Scleral Lens Education Society.
She is a contributing author for the American Optometric Association Contact Lens and Cornea section, and she is the author of the "GP Expert" column for Review of Contact Lenses.
She is also the Public Education Chair for the Scleral Lens Education society and is an Advisory Board member for GPLI. She currently practices at Havasu Eye Center in Lake Havasu, AZ.