The Scleral Lens Vault
Haptic Evaluation and Fit
BY GREGORY W. DENAEYER, OD, FAAO
The haptic portion of a scleral contact lens is the peripheral section that lands on the bulbar conjunctiva and sclera. Ideally, the lens haptic evenly lands and “sticks” to the surface without compression. Scleral contact lenses should be comfortable to wear and should remove easily from the eye.
The most common way to evaluate the scleral haptic is to use diffuse illumination under slit lamp examination. A successful scleral contact lens fit will not cause significant vascular blanching. The edge of the scleral lens should align to the surface without impingement or edge lift. Optical coherence tomography (OCT) can be used as an additional reference to evaluate the fitting relationship between the lens and the eye.
Removing a scleral lens is another way to evaluate the haptic fit. With a plunger positioned just inside the lens edge, a well-fit scleral lens will lift off without resistance.
Scleral lens compression can result from midperipheral curves that are too steep or from flexure. Circumferential blanching of the bulbar conjunctival vessels, as well as paralimbal edema and redness, will be evident when a scleral lens is compressing the eye.
A scleral lens that is pushed on too hard can result in temporary circumferential blanching even when the lens has an acceptable fitting relationship (Figures 1 and 2). Again, a well-fit lens will remove without resistance if the blanching is caused by excessive pressure during application. If there is significant resistance with removal, the scleral lens is compressing the eye.
Figure 1. A scleral lens that is too firmly pushed on during application, resulting in vascular blanching.
Figure 2. The same lens applied with a gentle push.
To eliminate compression, flatten the midperipheral curves to loosen the fit. You will then need to steepen the central curves of the lens to compensate for loss of sagittal depth to maintain lens vault.
Edge impingement results when the scleral lens edge is digging into the anterior ocular surface. Impingement may occur with or without compression.
Flatting the outermost peripheral curves is necessary to obtain an alignment fit. If you are unable to eliminate impingement with peripheral curve modification, consider switching to an alternative scleral lens design.
Although the scleral surface is nonrotationally symmetrical, often you can achieve adequate 360º alignment with a back-surface spherical lens design. Occasionally, an eye will have enough scleral asymmetry to create a fitting mismatch between the lens and the sclera that results in edge lift. Most of the time in these cases, the lens will exhibit a with-the-rule fit, causing edge lift in the superior and inferior quadrants. Edge lift will cause discomfort and can act as an opening for debris to migrate into the reservoir. Switch to a back-surface toric haptic design to minimize or eliminate edge lift. CLS
Dr. DeNaeyer is the clinical director for Arena Eye Surgeons in Columbus, Ohio, and a consultant to Aciont, Alcon, B+L, and Visionary Optics. You can contact him at firstname.lastname@example.org.