Corneal Optical Coherence Tomography Speckle in Crosslinked and Untreated Rabbit Eyes in Response to Elevated Intraocular Pressure.

Purpose: To ascertain the influence of intraocular pressure (IOP) on corneal optical coherence tomography (OCT) speckle in untreated and ultraviolet A-riboflavin induced corneal collagen crosslinked rabbit eyes. Methods: Left corneas of eight rabbits were de-epithelialized and crosslinked by applying riboflavin and 30-minute ultraviolet A light exposure. After enucleation (6 months after treatment), each eyeball (treated and untreated) was mounted in a measurement setup, in which IOP was increased from 15 to 45 mm Hg in steps of 5 mm Hg. At each IOP value, single B-scans of the central cornea were acquired three times with the spectral-domain OCT Copernicus-HR. Then, three regions of interest, including the anterior, posterior, and entire corneal stroma, were automatically extracted. Five different probability distributions were used as a model for the corneal speckle and the one with the best goodness of fit was chosen for further analysis. Results: The generalized gamma distribution achieved the best goodness of fit and its scale (a) and shape (v) parameters statistically significantly changed with increasing IOP in the three regions of analysis (two-way repeated measures analysis of variance, all P < 0.05). The statistically significant difference between untreated and crosslinked eyes was observed for the shape parameters of the posterior and entire corneal stroma. Conclusions: Corneal OCT speckle is influenced by IOP and shows to be significantly different in untreated and crosslinked eyes. Corneal OCT speckle analysis has the potential to be indirectly used for assessing changes in corneal stroma in ex vivo and in vivo studies. Translational Relevance: Investigation of corneal OCT speckle statistics can offer additional diagnostic biomarkers related to changes in the corneal stroma after ocular surgeries.

[Use of automatic alignment and combining adjacent images in fundus imaging]. / Zastosowanie metody automatycznego dopasowania i laczenia sasiadujacych zdjec w obrazowaniu dna oka.

The paper presents a method for automatic alignment and combining adjacent images of the fundus. Presented algorithm is based on specific arrangement of the vessels in the fundus. A correlation function is used to the adjacent images with extracted net of the vessels. An optimum location of the images is found by applying successive approximations method. An angle of rotation and shift of the combining images are taken into an account during this search. The paper shows also the examples of application of the method in fundus imaging.