contact lens case reports
The Importance of Maintaining Basic Fitting Principles
BY PATRICK J. CAROLINE,
FAAO, & MARK P. ANDRÉ, FAAO
J.D. is a 57-year-old male with a history of high myopia and 40 years of rigid gas permeable (RGP) contact lens wear. His spectacle prescription was: OD -13.75 -0.75 x 002; OS -13.00 -0.50 x 68, with visual acuities of 20/25 OU. He discontinued RGP lens wear for three months prior to undergoing LASIK on his right eye.
The surgery was aborted intra-operatively due to a tear in the flap created by a loss of suction during the microkeratome sectioning. The tear resulted in a linear scar with subjective symptoms of glare, especially under scoptic conditions (Fig. 1). Three months later, J.D. was again evaluated for LASIK on his right eye. However, he was advised to pursue contact lens correction due to slight corneal thinning and irregularity OD (Fig. 2).
FIG. 1: Corneal scar following an aborted LASIK procedure OD.
FIG. 2: Irregularity and thinning OD.
The microkeratome and suction ring are extremely complex instruments that can cause a number of mechanical and operator-induced complications, including: corneal perforation, an incomplete primary cut, a decentered or irregular primary cut, a 360 degree flap section (free-cap), tears, holes or folds in the flap, incorrect replacement or adhesion of the flap and intraoperative contamination of the surfaces.
It's important to remember that any surface irregularities over the visual axis have the potential to cause symptoms of glare or diplopia.
We eventually fit J.D. with soft contact lenses. However, custom parameters (base curve 8.00mm and diameter 15.0mm) were required due to the excessive sagittal height of his anterior segment. J.D.'s excessive sagittal height was created by a combination of anatomical features, including a large corneal diameter of 12.8mm and steep keratometric readings of greater than 45.00D (Figs. 3a & b).
This patient's case history illustrates the importance of maintaining the basic fitting principles of sagittal height in the face of corneal irregularities following refractive surgery.
FIG. 3a: J.D.'s excessive sagittal height secondary to a large corneal diameter and steep keratometric readings.
FIG. 3b: Average sagittal height created by an 11.8mm corneal diameter and a 43.00D keratometric reading
Patrick Caroline is an associate professor of optometry at Pacific University and an assistant professor of ophthalmology at the Oregon Health Sciences University.
Mark André is director of contact lens services at the Oregon Health Sciences University.