PURPOSE. Optical coherence tomography (OCT) shows retinal nerve fiber layer (RNFL) thickening in optic nerve head (ONH) swelling, but does not provide information on acute axonal disruption. It was hypothesized that scanning laser polarimetry (SLP) compared with OCT might reveal the status of axon integrity and visual prognosis in acute RNFL swelling.METHODS. Threshold perimetry, OCT, and SLP were used to prospectively study eyes with papilledema (24), optic neuritis (14), nonarteritic anterior ischemic optic neuropathy (NAION) (21), and ONH swelling (average RNFL value by OCT was above the 95th percentile of controls at presentation). Regional RNFL was judged reduced if the quadrant measurement was below the fifth percentile of controls.
RESULTS.At presentation, average RNFL by OCT was similar for eyes with papilledema and NAION (P = 0.97), and reduced for optic neuritis. Average RNFL by SLP was slightly increased for papilledema and optic neuritis, and reduced for NAION (P = 0.02) eyes. The RNFL by SLP was reduced in at least one quadrant in 1 eye with papilledema, 1 eye with optic neuritis, and in 13 eyes with NAION. In NAION eyes, quadrants with reduced SLP had corresponding visual field loss that did not recover. By one month, eyes with NAION showed RNFL thinning by OCT (7/17 eyes) and by SLP (14/16 eyes) in contrast to optic neuritis (by OCT, 0/12, P = 0.006; and by SLP, 1/12, P = 0.0004).CONCLUSIONS. OCT and SLP revealed different aspects of RNFL changes associated with ONH swelling. OCT revealed thickening due to edema. SLP revealed a decrease in retardance in eyes with axonal injury associated with visual field loss, which is unlikely to recover. (Invest Ophthalmol Vis Sci. 2012;53:1962-1970 DOI:10.1167/iovs.11-9339 O ptical coherence tomography (OCT) and scanning laser polarimetry (SLP) show loss of peripapillary retinal nerve fiber layer (RNFL) in glaucoma and at later time points after optic neuritis, nonarteritic anterior ischemic optic neuropathy (NAION), or traumatic optic neuropathy.1-11 Prior investigations, which used older methodologies to compensate for the corneal birefringence, have found that RNFL derived from SLP is not changed in eyes with edematous optic discs due to entities such as NAION.6,12 However, the RNFL thickness derived from OCT was shown to be increased with swelling of the optic discs due to intracranial hypertension. [13][14][15] A previous study of optic neuritis using both OCT and SLP has shown that mild RNFL edema is better demonstrated by OCT. In this optic neuritis study, acute reduction in birefringence is generally transient in acute optic neuritis, mostly reflecting temporarily increased RNFL water content (Kupersmith M, et al. IOVS 2009;50:ARVO E-Abstract 5664). Additionally, minimal RNFL thinning has been detected by both OCT and SLP one month after acute optic neuritis, even though OCT still shows some degree of RNFL swelling.
16For this study, consideration was given to whether using both OCT and SLP to image the peripapillary RNFL might provide complementa...