Clinical review of retinotopy

Abstract

Two observations made 29 years apart are the cornerstones of this review on the contributions of Dr Gordon T. Plant to understanding pathology affecting the optic nerve. The first observation laid the anatomical basis in 1990 for the interpretation of optical coherence tomography (OCT) findings in 2009. Retinal OCT offers clinicians detailed in vivo structural imaging of individual retinal layers. This has led to novel observations which were impossible to make using ophthalmoscopy. The technique also helps to re-introduce the anatomically grounded concept of retinotopy to clinical practise. This review employs illustrations of the anatomical basis for retinotopy through detailed translational histological studies and multimodal brain-eye imaging studies. The paths of the prelaminar and postlaminar axons forming the optic nerve and their postsynaptic path from the dorsal lateral geniculate nucleus to the primary visual cortex in humans are described. With the mapped neuroanatomy in mind we use OCT-MRI pairings to discuss the patterns of neurodegeneration in eye and brain that are a consequence of the hard wired retinotopy: anterograde and retrograde axonal degeneration which can, within the visual system, propagate trans-synaptically. The technical advances of OCT and MRI for the first time enable us to trace axonal degeneration through the entire visual system at spectacular resolution. In conclusion, the neuroanatomical insights provided by the combination of OCT and MRI allows us to separate incidental findings from sinister pathology and provides new opportunities to tailor and monitor novel neuroprotective strategies.

Differentiating glaucoma from chiasmal compression using optical coherence tomography: the macular naso-temporal ratio

“…This study suggests that the mNTR is a novel OCT metric which may contribute to distinguishing chiasmal compression from atrophy due to POAG, as it is reduced in chiasmal compression but increased in POAG. This is based on the pattern of macular inner retinal layer atrophy, 5 and far superior to the global mGCIPL thicknesses which were not discriminatory. These data indicate that regional macular atrophy patterns can be easily quantified and convey important diagnostic clues that are obscured by overall retinal thickness measures.…”