Abstract
Purpose: :
Inferior limited macular translocation (LMT) involves little if any internal scleral surface reduction. Yet it results in downward retinal displacement. The role of redistribution of the neurosensory retina (RNR) has therefore been suspected. Our purpose was threefold: try and demonstrate the role of RNR; perform displacement mapping all over the area centralis; try to improve The accuracy of the displacement evaluation.
Methods: :
Using piecewise linear image registration (on Matlab) on indocyanine green angiographic frames, we have evaluated the deformation (on both retinal and choroido–scleral layer) of a pre–operative grid superimposed on the area centralis, plotted displacement vectors all over the area centralis, and calculated a scale ratio between pre and post–operative frames. The scale ratio tests whether or not the same physical distance is represented by the same distance on these frames.
Results: :
The choroido–scleral layer is not deformed following surgery. The retinal layer shows areas of stretching and compression demonstrating the RNR. Displacement vectors feature a rotating pattern around the optic disk (except if a macular fold exists) and a positive naso–temporal gradient. Displacement angle ranges from 6.5 ° to 37.5 °. Mean scale ratio is 3.8%.
Conclusions: :
LMT involves RNR accounting for inferior displacement despite the supposedly limited internal scleral shortening. Our study confirms that the optic disk temporal edge is the displacement axis (except if a macular fold exists). Our method, unaffected by a non–zero scale ratio, provides more precision than previously published ones and could be used to evaluate surgical results of different macular translocation techniques in future studies.
Keywords: imaging/image analysis: clinical • age-related macular degeneration • vitreoretinal surgery