OCT can distinguish compressive from glaucomatous optic neuropathy

In this cross-sectional, observational study, SD-OCT and Heidelberg retinal tomography (HRT) revealed distinct patterns of retinal nerve fiber layer (RNFL) loss and change in optic nerve head morphology between eyes with open-angle glaucoma and those with compressive optic neuropathy.

The authors used SD-OCT and HRT to examine and compare the optic nerve head morphology of 69 eyes with compressive optic neuropathy, 58 eyes with open-angle glaucoma and 73 control eyes.

Although both compressive optic neuropathy and open-angle glaucoma discs showed enlargement of the cup and thinning of the RNFL, compressive optic neuropathy discs showed proportionally more thinning nasally and temporally compared with open-angle glaucoma discs. However, the inferior RNFL was thinner in open-angle glaucoma eyes when the level of visual field sensitivity damage was adjusted.

Both open-angle glaucoma and compressive optic neuropathy discs had larger and deeper cups than normal discs, while compressive optic neuropathy discs had significantly shallower cups than open-angle glaucoma discs. Furthermore, although compressive optic neuropathy discs had a larger vertical cup to disc area ratio compared with normal discs, this was significantly less than in open-angle glaucoma discs.

Compressive optic neuropathy discs were not significantly different from normal discs for HRT parameters, confirming previous findings that HRT cannot distinguish compressive optic neuropathy from normal discs. Open-angle glaucoma discs were significantly different from normal discs in all HRT and OCT parameters (P < 0.001).