Preliminary Analysis of a Novel Software-Based Method of Quantifying Metamorphopsia: A Pilot Study

Abstract

Purpose : To propose a digital method of quantifying metamorphopsia in patients with macular disease, and to assess its agreement with a commonly-used analog metric of metamorphopsia.

Methods : A software program was developed that displays on a monitor a straight vertical or horizontal dotted line bisecting a central fixation point, which a patient with metamorphopsia may reshape using the computer’s arrow keys until it appears straight to them (Figure 1). The program then calculates the area bound by the original straight line and the newly manipulated line (area under the curve, AUC) using the software-interface coordinates as units. This method of testing was attempted at a distance of 30 cm in 8 vision-corrected patients (16 eyes), each with differing macular pathologies. M-Charts metamorphopsia testing was also conducted on each patient for comparison. The relationship between M-Charts scores and AUC was analyzed using linear regression analysis. Testing was done in accordance with an IRB-approved protocol.

Results : Eight subjects (16 eyes) diagnosed in retina clinic with macular disease in at least one eye were included in this study. Description of subject characteristics and metamorphopsia testing results can be found in Table 1.
Linear regressions showed a significant relationship between AUC and M-Charts scores in both the horizontal (p < 0.001, coefficient 0.19, R²= 0.79) and vertical (p < 0.001, coefficient = 0.37, R²= 0.60) orientations.

Conclusions : User-based line manipulation such that it looks straight appears to be a viable method of characterizing visual distortions. Assuming constant central fixation, line length, and distance between the patient’s eye and the screen, perceived distortions along the vertical and horizontal axes can then be “mapped” onto corresponding slices of cross-sectional imaging, allowing for precise correlation between structure and visual function. Larger studies are needed to validate this proposed methodology.

This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.

 

Table 1

 

Figure 1—Screenshot of one subject’s changes to the objectively straight horizontal line presented to him. Although the patient had significant metamorphopsia as measured by M-Charts (0.2 H) and the patient felt confidently that this change resulted in straightening of the line, the observed changes are quite subtle (AUC 0.06).