Reversal of disc cupping after intraocular pressure reduction in topographic image series

To identify and characterize 'reversal' of optic nerve cupping following intraocular pressure (IOP) lowering in scanning laser tomography (SLT) longitudinal image series.

Modification was made to a previously described analytical approach to longitudinally study putatively increased rim area following IOP lowering. Sustained IOP reduction of 25% was by topical medication. Forty SLT image series with equivalent follow up were assessed: 10 with ocular hypertension (OHT), 10 with primary open angle glaucoma (POAG), and as controls, 20 normal. Reproducible rim area reversal was identified by sector and its time-course over 1 year examined.

By a 2-of-3 reproducibility criterion, reversal following IOP lowering was confirmed in about a third of treated eyes (POAG and OHT) but not in any controls. Rim sectors showing reversal were mostly nasal, with a few occurring superotemporally. Reversal in a fifth of treated eyes persisted for at least 1 year; all these were in the nasal half of the disc. The number of sectors with persisting reversal affected less than 6% of all treated eyes' rim sectors.

Rim area is not uncommonly increased after IOP lowering and this 'reversal' may persist for at least a year. Within topically treated eyes having IOP lowering of at least 25%, the proportion of rim sectors with persistent reversal appears small. Nevertheless, the effects of IOP reduction on topography, especially in the short term, should be considered when longitudinally assessing progressive rim loss in SLT images.