Three-dimensional depth perception significantly improves when patients with keratoconus switch from spectacles to gas-permeable contact lenses, according to a study, with binocular keratoconus showing greater improvement.
The study, conducted at the LV Prasad Eye Institute of Hyderabad, India, enrolled 33 patients with bilateral keratoconus, 10 with keratoconus in one eye and 20 healthy controls. All keratoconus subjects were experienced GP contact lens users with at least 1 year of regular use, 8 hours per day.
Monocular and binocular LogMAR acuity and stereoacuity were measured under unaided, best spherocylindrical spectacle-corrected and best GP contact lens-corrected conditions. Monocular logMAR acuity improved in both the monocular and binocular keratoconus group, and binocular logMAR improved in the binocular keratoconus group from spectacles to contact lenses. Stereoacuity also improved in both groups.
“In fact, the switch from spectacles to rigid gas-permeable contact lenses appears relatively more beneficial for depth visons than for spatial vision in both cohorts,” the authors wrote.
Switching from spectacles to contact lenses also resulted in reduction of inter-subject variability of logMAR acuity and stereoacuity, indicating that contact lenses lead to a more uniform and predictable visual performance.
Improved stereoacuity with contact lenses may be due to reduction in the magnitude and interocular difference in wavefront aberrations, reduction of aniseikonia and increase accuracy of binocular vergence, according to the authors. They pointed out, however, that stereoacuity with GP contact lenses was still significantly poorer than the median stereoacuity of control subjects, suggesting that performance enhancement, also with contact lenses, has a limit in eyes with keratoconus.
“Our study showed an improvement in three-dimensional depth perception of subjects with bilateral and unilateral keratoconus with rigid gas-permeable contact lens wear, relative to spectacles,” co-author Shrikant R. Bharadwaj BSOpt, PhD, told Primary Care Optometry News. “This information will aid clinicians to advocate RGP contact lenses as a management modality for keratoconus not only for improved spatial resolution but also for enhanced binocular depth perception. This advantage in depth perception is expected to be pronounced for patients with unilateral keratoconus, vis-a-vis, their bilateral counterparts.” – by Michela Cimberle
Disclosure: None of the authors has reported a relevant financial disclosure.