The pupillary light reflex pathway

Abstract

It was demonstrated that the pupillary light reflex (PLR) depends on the input of suprageniculate neurons, thus supporting the involvement of a cortical pathway also. The site of integration of cortical signals in relation to the PLR into the pupillomotor pathway may be located suprageniculately in the vicinity of the lateral geniculate nucleus. Moreover, the suggested combination of established lesion analysis techniques with the probabilistic cytoarchitectonic atlas turned out to be a very helpful amelioration of stroke data analyses.

Relative Afferent Pupillary Defects in Homonymous Visual Field Defects Caused by Stroke of the Occipital Lobe Using Pupillometer

“…10 Conversely, small RAPD due to HVFDs has been detected immediately after stroke, when no retinal atrophy should be present. 4 Therefore, such a discrepancy between the OCT and pupillary findings suggest that a major contribution of RTSD to the abnormal light reflex demonstrated here is considered to be unlikely. In the present study, the median time interval between lesion onset and the measurement of the RAPD was about 4 months and 8 of 15 patients with HVFDs were examined within 1 year of onset, RTSD of retinal ganglion cells should have been incomplete at the time of our pupillary examination.…”

“…27 In previous studies of RAPD in patients with HVFDs, since the RAPD score of 0.3 log units was used for distinguishing between the presence and absence of RAPD, RAPDs smaller than 0.3 log units had not been evaluated. 3,4 It was reported that there was a significant correlation between RAPD score by SFT using ND filter and RAPD score by RAPDx® ,28 and the normal value of RAPDx® in normal subjects was determined to be ≤0.2 log units. 16 While such a threshold should be useful in the clinical settings, this pupillometer has an advantage that a small RAPD can be measured because it is directly calculated from the amplitude and latency of the pupillary constriction obtained, unlike the conventional quantification by SFT using ND filter.…”

“…Their MRI analysis has suggested that a region including the course of the optic radiation at its early beginning in the temporal white matter is involved in RAPD. 4 Therefore, it seems that an RAPD appears when this particular region near the LGN is damaged. The relationship between the area Papageorgiou et al demonstrated 4 and the responsible lesion for normal vision with RAPD 6,7 remains unclear.…”

“…3,4 The reported occurrence of the RAPD appears to be definitely more than a chance. However, it may be difficult to detect a small contralateral RAPD due to a difference in the crossed and uncrossed fibres during a subjective evaluation.…”

“…3,4 These phenomena could be explained by the notion that the pupillomotor response depends upon or is influenced by the occipital cortex. 3–5 However, convincing anatomical evidence for this interpretation is lacking.…”