contact lens case reports

Piggyback System for Centration Woes

BY PATRICK J. CAROLINE, FAAO, & MARK P. ANDR�, FCLSA
April 1999

B.L. is a 48-year-old male who suffered a lid and corneal laceration to his right eye, which was surgically repaired (Fig. 1). He subsequently developed a traumatic lens opacification OD and underwent an uneventful intracapsular cataract extraction. Since 1996, he has had periodic spikes in intraocular pressure OD, which have been successfully controlled with Timoptic and Trusopt. B.L.'s left eye developed a subfoval chroridal neovascular membrane with a best corrected visual acuity of 20/50 (Fig. 2).

Corneal mapping OD revealed significant nasal flattening of approximately 40.00D, and a temporally displaced apex of approximately 53.00D. Simulated keratometric readings were OD 45.59 @ 16/49.75 @ 106 (Fig. 3). Attempts to fit the patient with a rigid gas permeable contact lens resulted in significant decentration due to the high asymmetrical astigmatism.

Decentration Solution

Lens decentration was overcome by using a custom piggyback soft lens manufactured by Flexlens (Mesa, AZ). This lens incorporates a circular groove in the anterior two thirds of the lens into which the rigid lens positions. The soft lens parameters were: base curve 7.40mm, power plano, diameter 15.0mm. The soft lens incorporated a 10.4mm circular cut-out into which the RGP lens was placed; base curve 7.50mm (45.00D) +2.50 9.0mm (Fig. 4). Visual acuity with the lenses was 20/25 with a wearing time of 14 hours each day.

In this case, the major advantage of the Flexlens piggyback system was centration of the rigid lens over the pupillary axis, despite the high asymmetric astigmatism. Additionally, lens comfort was excellent by virtue of the soft lens being the only plastic in contact with the cornea.

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Patrick Caroline is an associate professor of optometry at Pacific University and an assistant professor of ophthalmology at the Oregon Health Sciences University.

Mark Andr� is director of contact lens services at the Oregon Health Sciences University.