More sensitive correlation of afferent pupillary defect with ganglion cell complex

Abstract

PurposeThis study investigated the correlation between the relative afferent pupillary defect (RAPD) and retinal nerve fiber layer thickness (RNFLT) in optic neuropathy.MethodsRAPD assessment was performed using a log unit neutral density filter bar. Spectral domain optical coherence tomography RTVue-100 (Optovue) was used to examine the subjects. The optic nerve head pattern (ONH) was subdivided and identified for the purpose of the study into circumpapillary RNFLT (cpRNFLT) and peripheral circumpapillary RNFLT (pcpRNFLT). The cpRNFLT, pcpRNFLT and ganglion cell complex (GCC) parameters were analyzed.ResultsEighteen females and twenty three males with asymmetric optic neuropathy and a RAPD participated. Thirty-three subjects had glaucoma and eight had optic neuropathy other than glaucoma. Significant correlations (p < 0.02) were obtained for the RAPD and the percentage difference loss of the GCC and RNFLT parameters. The grouped mean percentage difference loss for RNFLT was significantly different from that of the GCC (p < 0.001). At a 0.6 log unit RAPD, the average mean percentage difference loss was 23% for the CRNFLT, 15% for the GCC, 12% for the global loss volume percentage and 6% for the focal loss volume percentage (FLV%).ConclusionsSignificant correlations between RNFLT loss for cpRNFLT, pcpRNFLT and GCC parameters with RAPD were observed. Approximately a 35% higher sensitivity was obtained using GCC compared to CRNFL parameters. The expected change in GCC average for every 0.3 log unit increment was approximately 8.49 μm. The FLV% corresponded more sensitively to a RAPD but appeared to be influenced by disease severity.

Focal Loss Volume Best Differentiates Eyes with Afferent Pupillary Defect

“…The communication of this hypothesis among the Eye Care Professionals may encourage research in this area and therefore may lead to the development of more sensitive methods for the evaluation and categorization of optic neuropathy. It should be emphasized that although relative RNFLT loss documented by GCC has the advantage of representing an objective measurement that seems to be more sensitive than cpRNFLT parameters at detecting a RAPD, in certain instances a RAPD may be observed without the presence of relative loss of RNFL in the affected eye (Besada et al, 2017;Takizawa, et al 2015;Noval et al, 2011). For instance, while RNFLT loss tends to occur after three to six months following an acute episode of anterior optic neuritis, during the acute phase paradoxically an increase in RNFLT has been reported.…”

“…Analogous to the results of Tatham et al (2014) and Chang et al (2013), we observed approximately 8.5 um RNFLT change or 9.4% inter-eye difference for every 0.3 log unit increment for the GCC average. For the focal loss volume (FLV) percentage, the intereye difference was lower, approximately 4.3% for every 0.3 log unit increment (Besada et al, 2017).…”

“…Since in our initial study we observed that the FLV percentage correlated more sensitively with a RAPD, we analyzed the distribution of FLV percentage values of subjects' eyes (Besada et al, 2017). We determined confidence limits to establish a criterion that may help categorize according to severity eyes that may have a RAPD and thus optic neuropathy.…”

A 30 s test for quantitative assessment of a relative afferent pupillary defect (RAPD): the infrared pupillary asymmetry (IPA)

“…Pupillary reaction testing is a crucial step in the clinical examination of patients with optic neuropathies. Presence of a relative afferent pupillary defect (RAPD) is one of the most informative clinical signs, indicating unilateral dysfunction at the level of the afferent visual pathways [1][2][3]. The RAPD is not helpful in situation of bilateral pathology [1].…”

“…The RAPD is not helpful in situation of bilateral pathology [1]. In patients with optic neuritis, a RAPD can be detected prior to development of inner retinal layer atrophy [2,[4][5][6]. Whilst clinically useful, the RAPD has not yet been included as a functional outcome measure in clinical trials and can be challenging to detect clinically in patients with dark eyes, or in the presence of anisocoria [7][8][9].…”