Contact Lens Case Reports
Adjusting for Settling Over Time with Scleral Lenses
BY PATRICK J. CAROLINE, FAAO, & MARK P. ANDRÉ, FAAO
In our September 2011 column, we reported that apical and limbal clearance scleral lenses settle into the conjunctiva approximately 120 microns throughout an eight-hour wearing period. We theorize that this has to do with the weight and bearing of the scleral lens on the “boggy” bulbar conjunctival tissue. The settling effects of a scleral lens are evident in Figure 1, in which we monitored a patient at 30 minutes and at one, two, four, six, and eight hours of wear. This 28-year-old female patient’s right lens settled 150 microns, and the left lens settled 130 microns.
Figure 1. Scleral lens settling as monitored throughout the day.
This month’s patient was referred to us from an ophthalmology practice in Alaska. She reported a longstanding history of keratoconus. Figure 2 shows the patient’s axial and elevation display maps for both eyes. The patient reported that she worked in a logging mill and was exposed to significant airborne debris in her work environment.
Figure 2. Our patient’s axial (top) and elevation (bottom) display maps.
Due to a growing intolerance to her left contact lens (secondary to her highly asymmetric cornea), it was decided that she would be an appropriate candidate for a scleral lens. A diagnostic lens was placed on her left eye, and a –7.50D sphere manifest refraction was performed over the contact lens, with an end-point visual acuity of 20/25.
We like our patients to wear the diagnostic scleral lens as long as possible (i.e., four to six hours) so we can monitor the amount of lens settling and the relationship of the lens haptic across the conjunctiva. To aid the patient’s visual acuity throughout this settling period, we placed a –7.00D Acuvue Oasys (Johnson & Johnson Vision Care Inc.) lens over the top of the scleral lens (Figure 3).
Figure 3. The –7.00D Acuvue Oasys soft lens over the diagnostic scleral lens.
The patient’s visual acuity was now 20/25, and her comfort was reported to be excellent—the most comfortable she had ever experienced with contact lenses. We re-examined the patient six hours later and were more confident in our assessment of the lens fit and in our adjustments to the diagnostic lens parameters.
In our experience, “piggybacking” a soft lens over the scleral lens is a wonderful way to provide functional acuity to patients during the initial diagnostic scleral lens settling period. CLS
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 for CooperVision.