Combining vascular and nerve fiber layer thickness measurements to model glaucomatous focal visual field loss

Abstract

We compare the focal structure–function correlation of structural measurements of peripapillary retinal nerve fiber layer thickness (RNFL‐T) using optical coherence tomography (OCT), capillary density (CD) measurements using OCT‐angiography (OCT‐A), or a combination of both, with visual field deviation (VFD) in early to advanced glaucoma. Primary open angle glaucoma patients (n = 46, mean ± SD age: 67 ± 10 years; VF mean deviation: −10.41 ± 6.76 dB) were included in this cross‐sectional study. We performed 30–2 standard automated perimetry OCT (3.5‐mm diameter ring scan) and 15°×15° OCT‐A (superficial vascular complex slab). Based on a nerve fiber trajectory model, each VF test spot was assigned to an OCT‐A wedge and an OCT ring‐sector. Two univariate linear models (Mv and Mt) using either CD‐based vascular (Mv) or RNFL‐T–based thickness information (Mt) and one multivariate model using both (Mv:t) were compared in their associations with measured focal VFD, which were higher for the multivariate model Mv:t (mean ± SD correlation coefficient: 0.710 ± 0.086) than for either nested model (0.627 ± 0.078 for Mv and 0.578 ± 0.095 for Mt). Using a focal visual field approach, the combination of RNFL‐T and CD showed better structure–function correlations than thickness or vascular information only.

Comparison of machine learning approaches for structure–function modeling in glaucoma

“…This floor level, which has been reported to range from −8 to −12 dB in other studies, 18,33,34,36,37 can also be inferred from the flattening of the VF MD estimations at around the −10 dB level with the LR models in Figure 1. In our study and others using nonlinear approaches based on decision trees, support vectors, or neural networks, a pertinent question to ask is why these difficulties at higher severities remain?-even in nonlinear models trained with relatively larger datasets.…”

“…While different models could be trained for different severities, this would ostensibly require predetermination of disease severities using an additional classification model, or the use of anatomical compensation 39 to adjust RNFL measurements for interindividual demographic differences to better stratify disease severity. Inclusion of vascular information from OCT angiography, which we and others have shown to be less susceptible to floor effects, could also help to improve the structure–function association, 40–43 particularly in more advanced glaucoma 37 . These and other strategies, such as the use of repeated VF data to reduce VF variability or a more precise determination of neuronal content in the RNFL, 44 can be considered in future studies to further improve the VF estimation to allow these models to be used clinically.…”

“…Variability in the structure-function relationship, due to the presence of non-neuronal components in the RNFL and individual differences, 38 is increased in later stages of glaucoma due to residual floor effects, 34 which we and others have shown to be less susceptible to floor effects, could also help to improve the structure-function association, [40][41][42][43] particularly in more advanced glaucoma. 37 These and other strategies, such as the use of repeated VF data to reduce VF variability or a more precise determination of neuronal content in the RNFL, 44 can be considered in future studies to further improve the VF estimation to allow these models to be used clinically.…”

Retrospective Analysis of Prognostic Value of Optical Coherence Tomography Angiography for the Development of Glaucomatous Damage – One Year Follow-Up Retrospective Observational Cohort Analysis

“…It should be also mentioned that it seems that in glaucoma eyes, practically all vascular plexuses measured by OCTA around the optic disc and also in the macula, be it in-depth or horizontally (perifoveal/parafoveal), are affected 18 , 19 , 20 . Also, it is the combination of the OCT structural data and OCTA data that correlates best with the observed focal VF defects 21 .…”

Retinal Oxygen Extraction in Patients with Primary Open-Angle Glaucoma

“…OCT angiography studies have consistently demonstrated a reduction in capillary density in the macular region as well as in the peripapillary region in patients with early and manifest glaucoma [ 28 , 29 ]. Recently, it has been reported that there is a strong association between local perfusion defects and local visual field changes in glaucoma [ 30 , 31 , 32 , 33 , 34 ], indicating that at least part of the vascular changes is the result of reduced metabolic demand secondary to retinal ganglion cell loss.…”