A 52-year-old male complained about the quality of his vision with his glasses. At his most recent eye exam about a year ago, his glasses had to be remade several times; although it seemed that the vision got better, it was never to the level that he was expecting. Examination revealed best-corrected visual acuity (BCVA) of OD 20/30, OS 20/40. Slit lamp evaluation with fluorescein revealed significant areas of negative staining consistent with a diagnosis of epithelial basement membrane dystrophy. All other exam findings were normal.

We discussed the condition and treatment options with the patient—specifically, specialty lenses, phototherapeutic keratectomy (PTK), and mechanical epithelial debridement in attempts to re-normalize the corneal surface. The patient was interested in the option of specialty contact lenses. He noted that he used to wear soft lenses for astigmatism, but about 15 years ago, he felt that his vision never seemed consistently clear through the lenses.

The Why of a Decentered Lens

The patient was fit with 15.8mm-diameter lenses with toric peripheral curves OD and OS. The BCVA with diagnostic lenses was OD 20/20, OS 20/20, OU 20/15. The diagnostic lenses were decentering inferiorly OD and OS. This could easily be observed with the vertical cross section through the lens and cornea using anterior segment optical coherence tomography (AS-OCT) (Figure 1).

An inferiorly decentered scleral lens can result in less-than-optimal visual acuity because of decentered optics, discomfort, and post-lens fogging. As such, it is critical to consider the scleral lens clearance vertically and, if decentered, to determine why it is decentered and to modify the fit to improve the fitting characteristics. Several factors can cause a scleral lens to decenter inferiorly including a flat landing zone, excessive vault or lens size, or surface drying, causing the lid to push the lens down on the blink.

The landing zone was well aligned nasally and temporally (corresponding to the flat meridian); however, in the vertical meridian, there was clearly a flat fitting relationship compared to the profile of the underlying sclera, likely causing the lens to decenter inferiorly.

The ordered lenses had landing zones that were two steps steeper in the steep meridian. When dispensed, the fit of the new scleral lenses was much more evenly centered vertically (Figure 2).

The Verdict

The vertical OCT cross-section is critical; it can reveal whether a scleral lens is fitting the way it should. If leveraging this OCT feature is not the new norm, we don’t want to be normal. CLS