The nasal circling phenomenon pattern of visual field loss on automated static perimetry Implications on the neuroanatomy of the optic chiasm

Abstract

Purpose: Progressive chiasmal dysfunction can produce nasal quadrant visual field defects after the development of a temporal hemianopia. The study determined if preservation of the superior nasal visual quadrant (i.e., predominant inferior nasal quadrant defect) is restricted to inferior chiasmal compressive lesions. Methods: Seventeen consecutive patients with temporal hemianopia and nasal quadrant defect (termed the ‘nasal circling phenomenon’) were studied. Full-threshold automated static perimetry and neuroradiologic imaging were performed on all patients. The proportion of predominant superior and inferior nasal quadrant defects was calculated. A predominant superior or inferior nasal quadrant defect was defined as having at least twice as many defective points at p<0.05, and more defective points at p<0.005, when compared with the corresponding inferior or superior nasal quadrant in that eye. Results: Twenty-five (74%) inferior but only 12 (35%) superior nasal defects were identified among the 34 eyes tested. The inferior nasal quadrant defect was the predominant nasal defect in 19 (83%) of 23 eyes with predominant nasal defect, irrespective of the lesion being superior, inferior, or intrinsic to the optic chiasm. Conclusions: The redominance of inferior nasal quadrant defect when temporal hemianopia with the nasal circling phenomenon is present appears to be related to alteration of the normal chiasmal architecture following compression, demyelination, or atrophy.