Automated measurement of longitudinal IS/OS junction abnormalities on SD-OCT in postoperative macular holes

Abstract

 

Purpose

 

To determine the correlation between visual acuity and segmented features on longitudinal SD-OCT scans after macular hole repair

 

Methods

 

An automated segmentation algorithm produced outlines of the IS/OS junction in SD-OCT cubes. IS/OS abnormalities were defined in a 2 mm radius from the foveal center if the axial distance or mean reflectivity between the outlined segments was less than two standard deviations from the mean of a normative distribution computed from a set of 16 scans from healthy patients. The total area of abnormal regions were recorded, as well as maximum, minimum, and mean distances from the regions edges to the foveal center. Percentage of IS/OS junction loss was also computed for a set of defined macula regions (similar to ETDRS regions), as well as circularity and eccentricity of the area of loss. We calculated the correlation significance between the quantitative measurements and visual acuity in a longitudinal set of 25 eyes from 25 patients examined after macular hole repair surgery, comprising a total of 61 SD-OCT scans. Correlation significance was defined as presenting a p-value less than 0.05 for testing against the hypothesis of zero correlation, using Pearson's linear correlation coefficient method.

 

Results

 

Significant correlation was found between visual acuity and percent of IS/OS junction loss at the foveal pit and parafoveal regions. Furthermore, visual acuity was also significantly correlated to measured area of abnormality and to the maximum, minimum and mean distances from the segmented outlined area to the foveal center. Higher percentage of loss, higher total loss area, shorter minimum distances, and higher maximum distances correlated with higher vision loss. There was also significant correlation of visual acuity to the circularity and eccentricity of the segmented region, with higher values of both features indicating more severe vision loss.

 

Conclusions

 

Loss of IS/OS area, the foveal pit, and the parafoveal area; distance of loss from the center of the fovea, and the eccentricity and circularity of loss are significant quantitative measures correlated to vision in eyes recovering from macular hole surgery.

 

 

SD-OCT B-scan. The IS/OS has been segmented between the two red lines. The green line delineates IS/OS loss.

 

 

2D map of IS/OS loss in a single SD-OCT cube generated by combining the segmented areas of IS/OS loss from all the B-scans.

 

Keywords: 586 macular holes • 550 imaging/image analysis: clinical • 552 imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound)