Quantifying the irregular

The mainstay of mapping and monitoring macular function is the Amsler chart. Since its introduction in 1947, the grid chart has become synonymous with macular disease. Its use has spread beyond the consulting room and most practitioners issue some form of the grid to the suspect maculopathy for their home use. It is quick and simple to use and, as shown in Figure 1, may help distinguish a scotoma from a distortion or metamorphopsia.

Familiar as it is, the Amsler is of questionable sensitivity and when it comes to metamorphopsia, where a line is distorted or shimmering, it is very difficult to assess how bad this effect is. Metamorphopsia is a feature of exudative changes at the macular (such as caused by wet AMD) or structural defects such as caused by epiretinal membranes or macular holes. Quantification of the metamorphopsia is a useful way of gauging the severity of impact of the condition or indeed of any treatment, assuming one has no access to an OCT (and even then, the OCT will reflect structural severity but not necessarily functional severity).