It has been reported that relative afferent pupillary defects (RAPDs) may be present in patients with occipital lobe lesions. However, a small contralateral RAPD due to a difference in the crossed and uncrossed fibres can be difficult to detect using the standard swinging flashlight test. The authors of this paper measured the pupillary light reflex objectively in 15 patients with homonymous visual field defects due to occipital stroke using a new pupillometer. The pupillometer measures the pupillary light reflex by alternating the stimulation of both eyes and can calculate two kinds of RAPD scores from the pupillary constriction amplitude and latency. The study detected significantly smaller and slower pupillary light reflexes in the eye contralateral to the brain lesion, compared to the eye ipsilateral to the lesion. These results confirm those of the previous reports of RAPD using a swinging flashing test using more objective methods. 

Relative afferent pupillary defects in homonymous visual field defects caused by stroke of the occipital lobe using pupillometer.
Takizawa G, Miki A, Maeda F, et al.
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Claire Howard

Salford Royal NHS Foundation Trust, Salford, UK.

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