OCT 21, 2019
This retrospective review examines how optical biometry measurements are influenced by epithelial basement membrane dystrophy (EBMD) and Salzmann nodular degeneration (SND).
The authors obtained baseline biometry findings from eyes with cataract and EBMD or SND that were scheduled for superficial keratectomy (SK) or phototherapeutic keratectomy (PTK). Baseline findings were compared with repeat biometry performed at least 30 days after surgery. The primary outcome measures included keratometry (K) values, axial length and magnitude and axis of corneal astigmatism. Secondary outcome measures included change in IOL power, toricity and axis.
Keratometry were altered by both EBMD and SND, as evidenced by clinically significant changes in keratometry after SK or PTK. These changes affected the spherical and toric IOL power. Appropriate management of EBMD and SND before cataract surgery can yield more reliable biometric data for surgical planning.
The authors do not address a chief limitation of toric IOL use in patients with SND and, to a lesser extent, those with EBMD: namely, the ongoing changes that such eyes tend to experience. These changes are particularly unpredictable in people with SND. Even in the unlikely event that a patient is amenable to frequent SK or PTK, such interventions may not precisely restore astigmatism neutralized by the toric IOL.
This study confirms the need for SK or PTK in patients with significant SND or EBMD, in order to make spherical IOL power as predictable as possible. Toric IOL implantation may be acceptable in patients with EBMD, as recurrence tends to be indolent and retreatment tends to restore corneal shape to its baseline.