Central Retinal Microperimetry by Scanning Laser Ophthalmoscopy in Chiasmal Patients with Visual Inattention Temporally at Monocular Visual Acuity Testing

Background: In a previous study, a specific visual behaviour was described in four chiasmal patients. It manifested as inattention/ignorance within the temporal visual space (“visual blocking”) at monocular visual acuity testing. Moreover, in 3 out of the 4, the process of reading a text appeared cognitively impaired. Methods: As a supplement to conventional visual field testing, the present analysis focus was on microperimetry by Scanning Laser Ophthalmocopy (SLO). Our aim was to identify the perceptual retinal counterparts to the temporally located visual field defects as caused by the visual pathway lesion on a chiasmal level, possibly also to indicate the apparently ineffective saccadic movements underlying that only part of the line on the chart could be given. Results and Conclusions: The central retinal areas with lacking recognition by SLO testing were given by black rectangles expressing scotomatous points; they clustered in a zone extending nasally from the fixation area, as expected. The methodology further depicted an orderly fixation in two cases, and only minor deviation in two. Fixation saccades thus were considered by and large within normal and with only exceptional outlier points recorded. All considered, the shortcomings of the perceptual mechanisms underlying the lateralised visual inattention as observed in the four patients have remained without a satisfactory explanation.