Frustration or Fenestration?
Lynette Johns OD FAAO FSLS
In some patients with keratoconus, keratoglobus, or pellucid marginal degeneration who have been grafted, the thinning and ectasia may continue to advance in the host tissue at the graft host junction. This steeping of the graft can render the eye unfittable with corneal (R)GP lenses because of lens instability. Scleral lenses provide an optimal fitting choice for a steep graft because they bypass the cornea entirely. What happens if the graft cannot support a scleral lens?
A patient with bilateral grafts returned for a routine scleral lens evaluation in August 2008. His left eye had a penetrating keratoplasty in 1980 for keratoglobus, and he was first fit with gas permeable scleral lenses in 1993. He complained of blurry vision and rainbows at night OS with the lens. His entering acuity after four hours of lens wear was 20/40-1.
After removal, the graft demonstrated mild-to-moderate microcystic epithelial edema; pachymetry was 705 microns, and the endothelial cell count was 745 ± 20 cells/mm2. His corneal profile is shown below.
Before considering a repeat transplant, he was fit with a fenestrated scleral lens. The goal of the fit was to maximize wearing time before edema occurs, minimize the bubble, and prevent the bubble from interfering with the visual axis. Due to the ectasia, bubble control was challenging.
Below is one of the fenestrated devices used during his fitting. He achieved 20/15-2 acuity with 16 hours of uninterrupted wearing time. The bubbles were mobile with various positions of gaze, and they did not desiccate the underlying cornea.
The patient recently returned for a follow-up in April of this year, and he continues to report between 14 to 16 hours of uninterrupted wearing time. His acuity was 20/20 after 5 hours of wearing time, and he denied any rainbows or clouding of his vision.
There was no corneal staining or microcystic edema after removal of the lens. His current device is 19.0 mm, is made of Boston XO2 material, has 950 µm sagittal depth, has 1 fenestration and has toric peripheral curves that vary between 215 and 800 µm from the flat haptic edge in four quadrants.
One fenestration provided this gentleman with over two-and-a-half years of successful lens wear with 20/20 vision. When a graft fails under a scleral lens, it may be related to endothelial dysfunction or lens suction. It is unclear whether the benefit of the fenestration is a reduction in suction or if it is increased oxygenation, but this is something we consider at the Boston Foundation for Sight if a graft fails with a non-fenestrated scleral lens.
Dr. Lynette Johns has been the senior optometrist at the Boston Foundation for Sight since 2005.
She is a graduate of the New England College of Optometry where she completed a residency in cornea and contact lenses. She is adjunct clinical faculty at the New England College of Optometry.
Dr. Johns is a fellow of the American Academy of Optometry and a fellow of the Scleral Lens Education Society.