Abstract
Purpose :
The sensorial aspect of binocular vision is poorly studied in keratoconus. Little is known about the frequency of strabismus and the stereopsis that supports 3D vision in keratoconus. This knowledge may help in clinical or surgical decisions for vision rehabilitation. The aim of the present work is to evaluate the motor and sensorial aspects of vision on patients with keratoconus.
Methods :
A series of patients with keratoconus, confirmed by corneal tomography and graded by the ABCD grading system, were evaluated for binocular vision and extraocular muscle motor function. Best-corrected visual acuity (BCVA) with glasses was measured in ETDRS chart at 4 meters. Binocular vision status for distance was checked using simple and alternate cover tests, red striate Maddox (for simultaneous perception), 6Δ base down prism (for fusion), and a prism bar (for fusional convergence). Stereopsis was measured using the Titmus Fly Test.
Results :
Forty-eight patients, with a mean age of 19.3 ± 7.3 years old, with a female:male ratio of 25:23 were evaluated. Considering the eyes with the worst vision, 2 (4%) were classified as A0 (Kmax <46.5), 2 (4%) as A1 (Kmax <48), 24 (50%) as A2 (Kmax <53), 3 (6%) as A3 (Kmax <55) and 17 (35%) as A4 (Kmax >55). Six (13%) patients had exotropia and12 (25%) had heterophoria. Nine (20%) out of 46 had no simultaneous perception, 10 (22%) out of 46 had no binocular fusion and 10 (29%) out of 34 had a fusional convergence of less than 15Δ. For stereopsis, 8 (20%) out of 45 had stereopsis equal or less than 63" and 23 (51%) out of 45 had 400" or worse. Patients whose BCVA in the worse eye was less than 0.2 (categories D3 <0.2 or D4 <0.05) had a significantly higher frequency of exotropia (p<0.05; OR: 12; 95% CI, 2.1-68.1), absence of simultaneous perception (P<0.05), and absence of fusion (p<0.05; OR: 12; 95% CI, 2.3-61.7).
Conclusions :
In our study, keratoconus patients presented a higher frequency of impaired binocular vision than the general population. It indicates a worse 3 D vision in these individuals. Future studies are needed to elucidate the factors associated with the loss of binocularity in this disease, such as the age of onset of ectasia or high order aberrations. Testing for 3D vision may be helpful to considere in the guidelines of treatments for patients with keratoconus.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.