Date Published: December , 2017
Publisher: Makerere Medical School
Author(s): Khathutshelo P Mashige.
To determine the intra-session and inter-session reproducibility of corneal, macular and retinal nerve fiber layer thickness (RNFL) measurements with the iVue-100 optical coherence tomography in normal eyes.
These parameters were measured in the right eyes of 50 healthy participants with normal vision. Six scans each for corneal thickness, macular and optic nerve head were taken on one day (intra-session), followed by similar repeated measures on five separate days (inter-session). Reproducibility was computed using intra-class correlation coefficient (ICC), coefficient of variation (COV), and test-retest variability (TRV).
For intra-session reproducibility, the ICC, COV and TRV values for mean corneal thickness were 0.924, 2.82%, and 3.06 µm respectively. For the mean macular thickness, they were 0.978, 4.64% and 4.51 µm respectively, while for mean RNFL thickness they were 0.946, 3.19%, and 5.66 µm respectively. Inter-session values for mean corneal thickness were 0.926, 2.65% and 3.48 µm, and 0.916, 2.24% and 2.03 µm for mean macular thickness. For mean RNFL thickness, they were 0.962, 2.21%, and 4.72 µm respectively.
There was good reproducibility of all measured parameters. However, mean RNFL thickness measurements were the most reproducible, suggesting that this may be the best parameter to use to determine measured changes over time.
Corneal thickness measurements are important for the planning of refractive surgery, diagnosis of glaucoma, and for therapeutic applications such as monitoring corneal oedema and endothelial function.1 Accurate and reliable determination of macular and retinal nerve fiber layer (RNFL) thicknesses have become increasingly necessary in the diagnosis and management of macular and optic nerve head anomalies, respectively.1
The study was approved by the University of KwaZulu-Natal’s Biomedical Research and Ethics Committee and adhered to the tenets of the Declaration of Helsinki. All participants gave written informed consent after the nature of the study had been explained to them. Participants were assured that their data would be presented anonymously to protect their identity. The study was conducted at the Discipline of Optometry, School of Health Science, University of KwaZulu-Natal, and a convenience sampling method was used to recruit 50 healthy participants from the employee pool and student population of the institution.
Fifty right eyes of 50 normal participants with a mean age of 26.6 ± 4.8 years (range, 19 to 38 years) were studied and analyzed. There were 25 women and 25 men, and 39 of whom were Black and 11 were Indians. For each participant six sets of results were obtained for each parameter; the parameters being the corneal, macular and RNFL thickness measurements in each quadrant. The OCT was well tolerated by all participants and their scans were good, with SSI values of above 70.
The iVue-100 is a relatively new generation SD-OCT device used to qualitatively and quantitatively assess ocular structures important to the pathogenesis and anatomical variations of several ocular diseases, and to identify approaches to successful treatment.11 Assessing the reproducibility of an instrument used for ophthalmic examination is important, as it affects the diagnostic accuracy and the ability to detect changes over time.12 Consequently, the goal of this study was to assess the reproducibility of the iVue-100 OCT corneal, macular and RNFL thickness measurements. To the best of the author’s knowledge, this is the first report on the reproducibility of these parameters using the iVue-100 OCT in normal subjects. The current study demonstrates that iVue-100 OCT corneal, macular, and RNFL thickness measurements are reproducible.