Abstract
Purpose :
Optotype visual acuity (OVA) in patients with infantile nystagmus syndrome (INS) is time, attention, and gaze (eye in orbit) dependent (GDVA). In their alert state, these patient’s best GDVA occurs at their null-position where their nystagmus is most dampened. Treatment goals for these patients are multifactorial as one goal is to improve best corrected VA; whereas another goal is increase the breadth and depth of the null-position. If OVA is to be used as an outcome measure for interventional studies in patients with INS, a method of collection needs to address its dynamicity. The purpose of this case-series is to present a novel method to quantify OVA across horizontal gaze as a measure called “functional vision space” (FVS) in patients with INS and show its utility as a measure of treatment effects.
Methods :
OVA (logMAR) was measured binocularly with best correction horizontally from -20 to +20 degrees in 5 degree intervals before and after combined medical, optical and surgical treatment in 85 patients with oculocutaneous albinism type 1 and INS. The best and worst OVA and the size of the null-position (degrees) was determined pre- and post-treatment. Additionally, the area under-the-curve (AUC) was calculated by integration with the horizontal eye position on the x-axis while logMAR OVA was on the y-axis to represent the zone of FVS with respect to horizontal eye position. A paired t-test was used to determine statistical significance between best and worst static OVA, size of the null-position and AUC for the zone of FVS pre- and post-treatment.
Results :
As a group, patients had a significant improvement in both their best (p<0.001) and worse (p<0.001) static OVA. Patients also had a significant increase (p<0.001) in the size of their null-position and a significant decrease (p<0.001) in the AUC (increase in FVS) after treatment.
Conclusions :
Specific changes of OVA in patients with INS can be quantified as a static change in best corrected OVA, worst OVA or improvement as a function of gaze (eye in orbit). We have also proposed a method of integration for calculating changes in OVA across horizontal gaze positions, e.g., GDVA, which encompass all three static measures into one metric, representing an area of functional vision space. The new metric may be used to monitor treatment outcomes in patients with INS.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.