Light retardance lower in NAION eyes

Patients with optic disc swelling caused by nonarteritic anterior ischaemic optic neuropathy (NAION) have less light retardance compared with patients with optic disc swelling caused by papilloedema or optic neuritis.

For this cross-sectional study, researchers set out to compare retinal nerve fibre layer thickness (RNFLT) in patients with optic disc swelling of different etiologies, and included a total of 47 patients. Scanning laser polarimetry (SLP; enhanced corneal compensation) and spectral-domain optical coherence tomography (OCT) RNFLT measurements were done in 19 eyes with papilloedema, 10 eyes with optic neuritis, and 18 eyes with NAION.

They found no statistical differences on average OCT-RNFLT in papilloedema, optic neuritis, and NAION. The average SLP-RNFLT in patients with NAION was smaller compared with that measured in patients with papilloedema (P P = 0.02).

Comparisons of RNFLT in each retinal quadrant reveled no difference among the etiological groups upon OCT; upon SLP comparisons, however, the superior quadrant was found to be thinner in NAION patients compared with papilloedema or optic neuropathy patients (P P

Superior SLP-RNFLT in patients with NAION was smaller (P = 0.026). The ratio of average SLP-RNFLT to average OCT-RNFLT was smaller in patients with NAION compared with papilloedema (P = 0.001).

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