Temporal crescent syndrome vs arcuate scotoma

Dear Editor,

It was with great interest that we read the article by Camacho-Velasquez et al.¹ describing a case of left monocular temporal scotoma, which was attributed to temporal crescent syndrome of ischaemic origin.

The case report includes the results of the Humphrey visual field test for the left eye, which shows arcuate scotomas crossing the midline in the inferior visual field.

Temporal crescent syndrome is a visual field defect caused by lesions to the most anterior part of the primary visual cortex. The most striking feature of the syndrome is that patients exhibit monocular scotomas despite the lesion being retrochiasmatic.²

Visual field defects in this syndrome are located between 60° and 90° in the temporal hemifield of the eye contralateral to the lesion; they cannot therefore be detected with the Humphrey visual field test as this technique usually focuses on the central 30° of the visual field.²

Defects can nonetheless be seen with confrontation visual field testing (when the examination begins at the periphery); graphical representation requires a technique including the whole visual field (e.g., Goldmann perimetry).

In the case presented by Camacho-Velasquez et al., if the scotoma is monocular, as the authors state, it should be attributed to an artefact or a prechiasmatic lesion as it involves the central 30° of the visual field. On the contrary, if it is secondary to a transient ischaemic attack, a congruent visual field defect should be detected in the contralateral eye.