Abstract
Purpose :
OCT image quality can be degraded by cataract, dry eye, corneal scarring, and vitreous hemorrhage. Little is known about the impact of such degradation on image segmentation and measurement of parameters such as macular or RNFL thickness. Here, we evaluate the effect of intentionally degrading the quality of Heidelberg SD-OCT images on RNFL and macular thickness measurements.
Methods :
Subjects were recruited in accordance with an IRB-approved protocol. Informed consent was obtained. Subjects underwent a screening ophthalmic evaluation consisting of visual-acuity measurement and slit-lamp examination. Inclusion criteria were: i) best corrected visual acuity of 20/20 to 20/25; (ii) no prior diagnosis of RNFL or macular pathology; (iii) no lenticular opacity or cataract; and (iv) no clinically evident corneal opacity. Subjects were excluded if they had any primary or secondary glaucoma, diabetes, or optic nerve, RNFL, or macular pathology. Subjects had RNFL and macular images taken under physiologic conditions using Spectralis SD-OCT. Subjects then had images captured with a 0.2 Bangerter occlusion foil in front of each eye to degrade the image quality. The values for central macular and RNFL thickness obtained under physiologic conditions were compared to those obtained under degraded conditions.
Results :
Data from 12 eyes (6 subjects) were analyzed. All images obtained with the foil in place exhibited lower Heidelberg image quality scores than the images obtained under physiologic conditions. In 10 of 12 eyes (83.3%) the global RNFL thickness measurement was increased in the lower-quality image. 2 of 12 eyes exhibited no change in global RNFL thickness measurement. The average increase in global RNFL thickness was 2.92 microns. In 7 of 12 eyes (58.3%) the central macular thickness (CMT) was increased in the lower-quality image, with a mean increase of 11.85 microns. In 3 eyes the CMT was decreased in the lower-quality image, with a mean decrease of 3.67 microns. 2 eyes exhibited no change in CMT.
Conclusions :
Measured RNFL and CMT were altered with intentional degradation of OCT image quality. A majority of eyes studied exhibited an increase in measured RNFL or CMT when OCT image quality was degraded. Clinicians should consider the possibility of erroneous measurements when evaluating poor quality OCT images.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.