The impact of optic nerve and related characteristics on disc area measurements derived from different imaging techniques

Abstract

PurposeOptic nerve head (ONH) assessment and its interpretation in healthy patients and those with glaucoma remains a pivotal topic specifically considering rapid advancements in imaging technologies. We undertook a large-scale, mixed cohort, comparative study to assess the correlation of optic disc measurements between different imaging modalities and investigated the impact of patient and disc associated parameters.MethodsONH sizes were obtained from one randomly selected eye of each of 209 patients using stereophotography, confocal scanning laser ophthalmoscopy and two different optical coherence tomographers (OCT). Patient related data, glaucoma status and optic disc variables, specifically oblique insertion, torsion, presence of beta PPA and spherical equivalent were recorded. Measurements between imaging modalities were analysed using Pearson correlation, linear regression analysis and Blend-Altman plots. Individual variables were compared applying multivariate regression analysis, ANOVA and chi square statistics was used to determine correlations between patient and clinical characteristics.ResultsAbsolute measurements significantly differed between imaging modalities generally producing smaller measurements for OCT derived measurements of Bruch’s membrane opening (BMO). Pairwise correlations between imaging modalities were between 0.83 and 0.93 for discs without myopia, oblique insertion, or beta PPA. These features impacted on measurements for individual modalities and consequently contributed to inconsistencies and variability.ConclusionIn comparison to planimetry, OCT derived BMO measurements are more variable in the presence of oblique insertion, beta PPA or magnification errors due to myopia. Impact of these factors, however, differs between instruments and needs to be considered to accurately interpret optic disc features in particular within the context of glaucoma diagnosis.

Optic disc area frequency distribution in a large sample of retinographic images

“…28 Similarly, measurements obtained with OCT are usually lower than those obtained by stereophotography or confocal laser scanning ophthalmoscopy, with correlation coefficients between them ranging from 0.83 and 0.93. 29 This is not contradictory to obtaining good reproducibility values with a particular method, as has been pointed out in our case. Therefore, as mentioned in a previous paragraph, absolute values are of little clinical and comparative value and it has even been suggested to dispense of them and to use standardised values.…”

“…Similarly, measurements obtained with OCT are usually lower than those obtained by stereophotography or confocal laser scanning ophthalmoscopy, with correlation coefficients between them ranging from 0.83 and 0.93. 29 …”

Peripapillary RNFL cross-sectional area and its association with other parameters in a Chinese population

“…Estimation of actual size optic disc area with Littmann’s mathematical approximations from color fundus images has < 4% bias [ 38 , 39 ] compared with a bias within 2% when disc area is measured using confocal scanning laser ophthalmoscope [ 40 ]. A good correlation is shown between these two methods despite some differences in optic disc area measurements [ 41 ]. In addition, simultaneous measurements of optic disc area by color fundus photographs and confocal scanning laser ophthalmoscope were made in 52 randomly selected eyes during the present study and no significant differences were found between the two methods [ 20 ].…”

A comparison of optic disc area measured by confocal scanning laser tomography versus Bruch’s membrane opening area measured using optical coherence tomography

“…This was attributed in part to the manual outlining of the margin, which can be better detected in disc photographs versus disc scans [ 16 ].On the contrary, OCT tended to measure optic disc size about 10% smaller when compared to disc photographs [ 17 ]. Yapp et al (2018) compared operator-driven (stereoscopic photography and CSLT) and automatic (BMO-OCT) disc size area measuring techniques [ 18 ]. The results showed that while CSLT and disc photography showed good correlation, BMO size tended to be smaller when measured by OCT. Additionally, a slightly greater deviation tendency was noted with increasing disc size.…”