Managing Scleral Contact Lens Seal-Off
BY GREGORY W. DENAEYER, OD, FAAO
Corneal GP lenses, soft lenses, and hybrid lenses require some lens movement with blinking for tear exchange. When these lens types fit too tightly without movement, they cause patients to experience irritation and redness.
Scleral lenses, on the other hand, are unique in that when they are properly fit, they semi-seal to patients’ eyes without movement. In fact, a scleral lens that translates with blinking is uncomfortable to wear. Tear exchange with a semi-sealed scleral lens results from a pumping effect that occurs with blinking-related lens flexure. Amazingly, this occurs even though the lens is depressed into the patient’s conjunctiva. A scleral contact lens that is properly semi-sealed to the eye can generally provide a patient with comfortable, full-time daily wear.
If a scleral lens fits too tightly, then it causes the lens to shift from a semi-sealed state to a completely sealed state. In a sealed state, the scleral lens will cause blanching of the blood vessels, paralimbal edema, and it will prevent any tear exchange. When this occurs, patients will experience significant irritation and redness, leading to decreased wear time. Chronic wear of a scleral lens that completely seals to the eye can result in significant corneal neovascularization. Late-onset seal-off can occur if the scleral contact lens causes conjunctival chemosis, leading to a progressively tighter fit over time.
Checking for Seal-Off
During diagnostic lens fitting, the haptic portion of a scleral lens should rest on the scleral conjunctiva without excessive compression. One way to test for this is to remove the lens with a plunger that is positioned on the lens haptic. A well-fit lens should lift off without resistance.
Also, a scleral lens that fits too tightly will often exhibit circumferential blanching. If the diagnostic lens demonstrates excessive compression during the diagnostic lens fitting, then flatten the peripheral curves to loosen the fit. Keep in mind that the lens will lose some sagittal depth when the peripheral curves are flattened, which may require a slightly steeper base curve to compensate.
Beware the Hinge Effect
Successfully loosening a scleral contact lens that seals off requires that you start flattening the haptic with the peripheral curve that is central to the area of blanching. If you flatten the peripheral curves only within the corresponding area of the lens haptic that blanches the eye, then the scleral lens will actually fit tighter. Essentially, the haptic will act like a hinge and dig farther into the eye as the edge is lifted up. Measuring the width of the blanching will allow you to determine which peripheral curve to start flattening (Figure 1).
Figure 1. The peripheral curve flattening should start with the peripheral curves of the design central to the area of blanching (arrow).
An Essential Skill
Scleral lens seal-off can reduce wearing time and put patients’ eyes at risk for inflammation and neovascularization. Correctly diagnosing and managing this complication will get patients back into comfortable, full-time lens wear. CLS
|Dr. DeNaeyer is the clinical director for Arena Eye Surgeons in Columbus, Ohio, and a consultant to Visionary Optics, B+L, and Aciont. You can contact him at gdenaeyer@arenaeyesurgeons. com.|