Contact Lens Case Reports
“Life” Beneath a Scleral Lens...Epithelial Bogging
BY PATRICK J. CAROLINE, FAAO, & MARK P. ANDRÉ, FAAO
The environment beneath scleral lenses is incredibly unique and something we are just beginning to understand (Figure 1). Posters presented by Morrison et al and by Walker et al at the 2014 Global Specialty Lens Symposium have shown that once an apical and limbal clearance scleral lens is placed onto the eye, little or no tear exchange takes place throughout the day. This means that the preservative-free (PF) saline or PF artificial tears placed into the bowl of the lens upon application will remain in contact with the ocular surface throughout the wearing schedule.
Figure 1. The unique environment beneath today’s scleral lenses.
We can only imagine the shock to the surface epithelium when the complex nutrient- and electrolyte-rich tear film is replaced/diluted with simple 0.9% saline. We believe that this “shock” clinically manifests itself as a condition called epithelial bogging.
Here Is the Scenario
You successfully fit your patient with a scleral lens and instruct him to place PF saline into the lens bowl prior to application. On follow up, the patient reports excellent comfort and visual acuity. However, when you remove the lens and perform a slit lamp exam, the ocular surface is irregular and appears “water-logged” (i.e., epithelial bogging).
We are unclear as to the exact etiology/mechanism for this phenomenon, but we suspect that it is the epithelium’s initial response to the sodium chloride solution that contains no nutrients or electrolytes. In our experience, the condition appears to be transient; with time, the epithelium adjusts to its new environment and, after approximately four to six weeks, the ocular surface resumes a more normal appearance (Figure 2).
Figure 2. Epithelial bogging following one week of scleral lens wear and the same eye at two months.
Logic then dictates that we need a PF solution specifically formulated for the environment beneath scleral lenses that contains nutrients and electrolytes essential for the health of the ocular surface. Our work at Pacific University has shown that this needs to be approached with a great deal of caution.
Those of us who have fitted hundreds or thousands of diseased eyes with scleral lenses have been humbled (and confused) by the extremely low incidence of microbial keratitis in these severely diseased and compromised eyes. Why is this? Is the sclerals’ semi-closed, saline filled environment responsible for this? Will we compromise this unique, perhaps anti-microbial, environment if we incorporate nutrients and electrolytes in a PF solution beneath these lenses?
Right now, epithelial bogging is just another relatively benign scleral lens complication that, like tear film fogging and conjunctival prolapse, we clinically manage as we wait for ongoing studies to provide more clarity. CLS
For references, please visit www.clspectrum.com/references and click on document #232.
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.