D-Chart: a novel method of measuring metamorphopsia in epiretinal membrane and macular hole

Background:
Metamorphopsia is common in macular disease. Current techniques for measuring metamorphopsia require good vision or costly equipment. The authors report a method that uses printed cards.

Methods:
The cards have a grid of squares arranged in a ring around fixation. There are four rings, at different distances from fixation, divided into eight sectors. The separation of the grid elements ranges from 0.4° to 1.8°. Subjects indicate in which sectors the lines of squares are distorted. The sum of the maximum separation perceived as distorted in each sector gives the total metamorphopsia score. Thirty-three eyes with epiretinal membrane and 29 eyes with macular hole were tested. Twenty-four eyes were tested again after surgery. In 18 subjects, the preoperative test was performed twice to assess repeatability.
Results:
The median preoperative total metamorphopsia score was 10.2 for macular hole and 5.2 for epiretinal membrane. After surgery, the median total metamorphopsia score was 0.5 for macular hole and 0.45 for epiretinal membrane. Test–retest results showed good correlation. Improvement in metamorphopsia did not correlate with change in visual acuity.
Conclusion:
Measurement of metamorphopsia may be useful in the management of macular hole and epiretinal membrane. D-charts are a simple and inexpensive method of quantifying metamorphopsia that can be used in a clinical setting.