Virtual Scleral Lens Fitting over Large Filtering Bleb Using Corneal-Scleral Topography

Scleral lens fitting can be challenging in the presence of localized conjunctival/scleral elevations (pingueculae or filtering blebs) in the area of the lens landing zone. We report on a case that was virtually fit successfully with a new corneal-scleral topography system. The patient had a history of keratoconus and subsequent penetrating keratoplasty as well as a previous trabeculectomy and glaucoma shunt surgery. Scleral topography revealed a 7mm wide and 2mm deep supero-temporal elevation. The topography software contained a “cut-out” tool which removed the elevation for the purposes of scleral lens fit since inclusion of that area could adversely affect fit when a notch or a localized vault of the scleral lens is used to avoid this area. Customized fitting software recommended a base curve (BC) of 42D and 288μ of posterior haptic toricity to achieve 300μ of central corneal clearance and haptic alignment. The diameter and elevation of the bleb from scleral topography were used to order a notched lens and one with a customized back surface haptic. Both lenses were successfully fit in the same eye, equally comfortable with improved vision. No fitting complications resulted from either design and both lenses were well stabilized with posterior haptic toricity. The patient currently wears the lens with the customized back surface haptic. Key Words: scleral lenses; scleral obstacle; scleral shape