Quantitive evaluation of metamorphopsia in macular disease

Introduction: Visual acuity loss and scotoma are not the only functional co nsequence of macular disease. Frequently, patients also complain of metamor phopsia. Such visual distortion should be taken into account when evaluatin g the potential benefit of surgical procedures in macular disease. The Amsl er grid does not allow any quantified analysis. In addition, a precise conf rontation of the macular lesion with its functional consequences is not pos sible by this test. We present a new method for analyzing metamorphopsia in macular disease. Methods: Opto-acustic modulation controlled laser emission allowed to gener ate a retinal image of 256 squares with an angular size of 1 degrees each. The subject was instructed to fixate the center of the grid and to push a h andheld button every time he perceived abnormalities within the presented p attern. At the end of the procedure, the responses were represented on grap h superimposed on the fundus image. 15 eyes of 15 successive patients compl aining of metamorphopsia were included in this preliminary study. Informed consent was obtained prior to inclusion. All patients reported abnormalitie s on standard Amsler testing. The test-retest reliability was evaluated by repeating the same procedure between 2 hours and 7 days after the first pro cedure. Results: The evaluation of 3 patients did not provide reliable information on metamorphopsia because of instable fixation. In 12 patients, a coherent response was obtained. In 9 eyes, the result was unchanged when repeating t he procedure, concerning both the number of abnormal elements and their spa tial distribution. Conclusion: The preliminary results appear to be encouraging, indicating a good reproducibility of the results of this method. They should be confirme d an a larger scale. Further work is necessary to evaluate the interest of this method in assessing functional results of macular surgery.