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.