contact lens case reports

Post-LASIK Decenterd Ablations

BY PATRICK CAROLINE, FAAO, & MARK ANDRE, FCLSA
AUGUST 1998

A 41-year-old woman presented with a 20-year history of both rigid and soft contact lens wear. She had discontinued use of her soft lenses three months prior to undergoing a LASIK procedure, and her refraction stabilized at OD -9.50 -1.00 x 15 and OS -9.00 -0.75 x 170, with visual acuities of 20/20 OU. An uneventful LASIK procedure was performed on her left eye, and at two weeks postoperatively, the uncorrected visual acuity was 20/300, with a manifest refraction of -4.00 -0.50 x 180, 20/30. Photokeratoscopy and corneal mapping revealed a nasally decentered ablation (Fig. 1).

Potential Complications

LASIK complications can be divided into three categories: intraoperative, postoperative and refractive. Intraoperative complications are usually traced to microkeratome or suction ring malfunction, resulting in incomplete or irregular cuts. Postoperative complications include flap detachment, epithelial ingrowth, foreign bodies within the flap interface and infection. While intraoperative and postoperative complications are rare, they can significantly jeopardize the surgical outcome. The majority of LASIK complications are refractive in nature and include: undercorrections, overcorrections, regression effects, stromal haze, central islands and decentration of the ablation.

Decentration of the laser ablation is a serious complication that does not have any simple solutions. Postoperatively, the patient sees through the sloping edge of the ablation, resulting in a loss of best corrected visual acuity, irregular astigmatism, undercorrection, monocular diplopia and ghosting.

The Soft Lens Solution

We fitted our patient with a standard -4.00D planned replacement soft contact lens, but due to the thinness of the lens, she experienced significant fluctuation in vision throughout the day. We then fitted her with a -4.00D Harrison Post Refractive Surgery soft contact lens (Fig. 2) manufactured by Flexlens Products, a division of Paragon Vision Sciences. Her visual acuity immediately improved to 20/25, and her visual stability improved significantly as well.

The Harrison PRS design incorporates a number of unique design features to accommodate the topographic and physiologic requirements of the post-refractive surgery cornea. These features include: a thicker central optic zone to stabilize the optics over the flatter central zone, a thin peripheral lens design to maximize oxygen permeability to the peripheral cornea, and a wide range of lens parameters -- base curves 6.00mm to 9.90mm, powers +30.00D to -30.00D and diameters 10.0mm to 16.0mm.

Patrick Caroline is an assistant professor of ophthalmology at the Oregon Health Sciences University and an assistant professor of optometry at Pacific University. Mark Andre is director of contact lens services at the Oregon Health Sciences University.