Amblyopia.

Microstrabismus is characterized by a small angle of squint (either convergent or divergent) of less than 5 degrees and a harmonious anomalous correspondence. Stimuli falling on retinal areas that normally do not correspond nevertheless form one percept. The angle between the retinal area in one eye and the fovea in the other eye is the same as the objective angle of squint. In these patients, some degree of stereopsis and mild amblyopia are generally found. Nevertheless, visual function and particularly reading performance may be relevantly impaired. Diagnosis of amblyopia is based on reduced visual acuity, but other anomalies such as reduced contrast sensitivity and anomalous spatial sense frequently coexist. Eccentric fixation is manifest in up to 80% of amblyopes and this, along with other fixation anomalies, contributes to the visual acuity reduction. For clinical observation of visual parameters, it has been proven that only standardized testing procedures provide reproducible and comparable measurements. The recently developed fundus-related MP-1 microperimeter allows for a fast, reliable microperimetric examination of fixation and scotoma characteristics in patients affected by macular diseases. even when visual acuity can be extremely poor and fixation is unstable and eccentric. The authors hypothesize that an objective, repeatable examination of fixation may be a useful tool to study visual impairment in microstrabismic amblyopia. In the present study, children with microstrabismic amblyopia were tested in a standardized clinical setting considering the characteristics of amblyopic vision; visual acuity was determined using ETDRS charts and fixation patterns were assessed using the MP-1 microperimeter in order to evaluate some of the most relevant functional deficits.