Abstract :
Background: The concept of retrograde axonal degeneration is well studied for visual pathway lesions upto lateral geniculate body. Since clinically evident optic nerve head changes and papillary changes are usually absent in post geniculate lesions, very few studies have been reported to look for the presence of retrograde axonal degeneration in these lesions.
Aims: To analyse RNFL and GCC thickness in patients with retrogeniculate lesions using Spectral Domain OCT and to determine any characteristic thinning pattern corresponding to the visual field defect.
Materials and Methods : Patients attending Ophthalmology OPD as diagnosed cases of unilateral retrochiasmal lesions were included in the study. Those who showed homonymous hemianopia corresponding to the retrochiasmal lesions were subjected to OCT RNFL and GCC. Spectral domain OCT was performed on all patients using ZEISS Cirrus HD-OCT Model 400.
Results: Mean age of the study population was 55.5±14.02 years. 21(70%) patients were males, 9(30%) were females. Ipsilateral eyes have superior RNFL thinning, contralateral eyes have inferior, nasal and temporal quadrants thinning. Average RNFL thickness and GCC thickness was reduced in the contralateral eyes. In ipsilateral eyes, temporal GCC was thinner compared to nasal, whereas in contralateral eyes, nasal GCC was thinner compared to temporal.
Conclusion: The pattern of RNFL and GCC thinning corresponds with pattern of visual field loss. The thinning of RNFL and GCC is in accordance to the known trajectories of the crossed and uncrossed projections arising in the nasal and temporal hemiretinae respectively. Our study substantiates that retrograde axonal degeneration occurs in post geniculate lesions also.
Keyword :
Ganglion cell complex, Optical coherence tomography, Post geniculate lesions, Retinal nerve fiber layer, Retrograde axonal degeneration.