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Abstract
The aim of this study was to determine the sensitivity of retinal areas involved in
a localized retinal nerve fiber layer (RNFL) defect and to assess correlations between
microperimetry and the standard full threshold central 30 deg visual field test. Twenty-five
patients with focal RNFL defects, evaluated by means of Argon-blue scanning laser
ophthalmoscopy (SLO), underwent an automated 30 deg central visual field examination
and a microperimetry with SLO. Microperimetry was performed according to standard
procedures (infrared laser for fundus imaging; HeNe laser for 10 candles/m2 background
illumination, fixation aid and generation of stimuli; manual fundus tracking). The
size of stimuli was Goldmann III with 0.1 sec duration. In eyes with focal RNFL defects
a deep microperimetric scotoma of at least 5 dB was found in 12 cases and a mild scotoma
(1-4 dB) in 13 cases. These scotomas were mainly located throughout the whole defect
or grouped in the temporal or nasal sides of the defect and were characterized by
sharp and well-defined borders. With automated perimetry, a scotoma, defined by a
single point depression of at least 10 dB or a depression of at least 5 dB in two
or more contiguous points corresponding to the RNFL, defect, was found in only 14
out of 25 eyes with microperimetric defect. Focal RNFL defects correspond to localized
areas of depressed retinal sensitivity as evaluated by microperimetry. The close correspondence
between structural and microperimetric findings suggests that, in hypertensive eyes
also, localized RNFL defects correspond to visual dysfunction possibly associated
with substantial atrophy of ganglion cells.