Contact Lens Case Reports
The Toric Sclera
BY PATRICK J. CAROLINE, FAAO, & MARK P. ANDRÉ, FAAO
Modern GP scleral lenses have had a tremendous impact on our contact lens industry. This is especially true when managing conditions in which there are significant height differences across the cornea or in cases involving ocular surface disease. We believe the rebirth of scleral lenses was brought about by: the availability of large-diameter GP lens buttons; improved computer-controlled lathing technology; improved fitting techniques; and a greater understanding of corneal, limbal, and scleral shape.
Our observations at Pacific University have shown the sclera to be both toric and asymmetric in the vast majority of normal and pathologic eyes. Therefore, when problem-solving patients who are experiencing scleral lens discomfort, a number of etiologies should come to mind: improper lens cleaning or handling; solution incompatibilities; inadequate or excessive clearance across the central, midperipheral, and limbal ocular surface; and the landing of a symmetric lens across a toric or asymmetric sclera.
Modern scleral mapping techniques have provided us—for the first time—with the ability to better understand the complexities of the scleral shape. This was described in a poster presented at the 2016 Global Specialty Lens Symposium by Kinoshita et al (2016) in which they used the sMap3D (Visionary Optics) to evaluate the scleral shape of three individuals reporting unilateral or bilateral discomfort with their scleral lenses.
Patient #1 had bilateral corneal transplants following radial keratotomy (RK) and reported bilateral discomfort with his symmetric scleral lenses. The scleral height differential (the toricity) between the steep and flat scleral meridians was right eye 323µm, left eye 239µm (Figure 1).
Figure 1. Patient post-bilateral corneal transplants with bilateral scleral lens discomfort.
Patient #2 had bilateral laser-assisted in-situ keratomileusis (LASIK) and reported discomfort in the right eye only. The scleral height differential was right eye 498µm, left eye 43µm (Figure 2).
Figure 2. Post-LASIK patient with scleral lens discomfort in the right eye only.
Patient #3 had bilateral RK with symptoms of discomfort in the right eye only. The scleral height differential was right eye 536µm, left eye 155µm (Figure 3).
Figure 3. Post-RK patient with scleral lens discomfort in the right eye only.
This case series illustrates the clinically anecdotal relationship between scleral lens comfort and the shape (toricity) of the sclera. All three patients noted a dramatic improvement in their lens comfort and wearing time when switched to a peripheral toric haptic lens design.
Additional studies are needed to understand other mechanisms of scleral lens intolerance, such as idiopathic ocular neuralgia. CLS
We wish to thank Drs. Beth Kinoshita and Sheila Morrison for their assistance with this month’s Case Reports column.
For references, please visit www.clspectrum.com/references and click on document #246.
Patrick Caroline is an associate professor of optometry at Pacific University. He is also a consultant to Contamac. Mark André is an associate professor of optometry at Pacific University. He is also a consultant to CooperVision.