M Charts Versus Amsler Test in Evaluating Metamorphopsia in Neovascular AMD Patients Treated With Anti-VEGF

Introduction

Age-related macular degeneration (AMD) is a complex eye disorder and the most common macular disease affecting millions of aged people in developed countries, with an estimation that the number of AMD patients will be increased to 196 million in 2020, 288 million in 2040. Vision loss, central scotomas, and metamorphopsia are the hallmark signs in patients with macular diseases. Metamorphopsia can be defined as a deformation of seen rectilinear lines due to photoreceptor separation/location and it is a typical but not exclusive sign of retinal disease. The most effective method of treating wet AMD is currently the anti-vascular endothelial growth factor intravitreal injections (anti-VEGF). Fluorescein angiography (FA) could be crucial for diagnosis but may be associated with serious complications, hence it has been replaced in clinical practice by Optical Coherence Tomography (OCT).

OCT is a quick and non-invasive procedure proving to be a detailed and reproducible tool for qualitative and quantitative assessment of the macular structure, and a useful tool for investigating the efficacy of anti-VEGF treatments in AMD patients. A further concern is the enormous costs and restriction of human resources that make periodic FA and OCT imaging unfeasible. Therefore, in patients with AMD treated by intravitreal anti-VEGF, monitoring with sensitive psychophysical tools could advance the time for diagnosis of CNV reactivation and enhance the outcome of treatment. For assessment of the visual function, visual acuity and Amsler grid have been the gold standard. The Amsler grid is a set of 7 charts of which the number one is the most commonly used: it a simple and noninvasive test effortlessly understood by the patient, consisting of evenly spaced vertical and horizontal lines outlining 400 square, it has been widely adopted as a subjective test for metamorphopsia. However, it also produces a decent false-negative rate. Moreover, the answer to this test is dichotomous: straight or crooked lines and does not allow for quantification thus, it is problematic to monitor the visual function along the course and to evaluate the effectiveness of treatment with anti-VEGF agents. The M-chart (Inami Co., Tokyo, Japan) is a diagnostic device developed by Matsumoto to quantify the grade of metamorphopsia in patients with various types of macular diseases.

The usefulness of M-charts has been already demonstrated in different retinal diseases from macular pucker to BRVO.

The aim of this study is to compare the traditional Amsler grid and the M-Charts in evaluating metamorphopsia in patients suffering from wet AMD before and after Anti VEGF injection, and to match it with OCT results.