Structural and functional differentiation between compressive and glaucomatous optic neuropathy

Abstract

Clinical diagnoses of slow, progressive, painless visual losses with various degrees of visual field (VF) losses and disc atrophy are often confused between suprasellar compressive optic neuropathy (CON) and open-angle glaucomatous optic neuropathy (GON). We plotted the thickness of the peripapillary retinal nerve fiber layer (RNFL) and macular ganglion cell-inner plexiform layer (GCIPL) against the mean deviation (MD) of the VF of 34 eyes of CON at diagnosis, 30 eyes of CON after therapy, 29 eyes of GON, and 60 eyes of healthy controls in a cross-sectional investigation. At diagnosis, a disproportionally early pattern of structural thinning compared with the corresponding VF losses was unique to CON. GON- and CON-specific thinning parameters were generally useful in differentiating GON and CON from moderate to severe MD losses, but early MD losses (0 to − 6 dB) overlapped with GON in a CON-stage specific manner. GON-specific thinning parameters, RNFL in the inferior sector, and inferior to temporal macular GCIPL ratio showed overlap with posttreatment CON in the early MD losses with AUCs of 0.916 (95% CI 0.860–0.971; P < 0.001) and 0.890 (95% CI 0.811–0.968; P < 0.001), respectively. In comparison, CON-specific thinning parameters, superonasal, and inferonasal GCIPL showed overlap with CON at diagnosis for early MD losses. Overall, the nasal-to-temporal macular GCIPL ratio showed good discrimination between CON and GON throughout the MD range, with an AUC of 0.923 (95% CI 0.870–0.976; P < 0.001). Comparing GON with all stages of CON, the cut-point of 0.95 showed the lower nasal-to-temporal GCIPL ratio had a sensitivity of 72% and specificity of 90% for CON. However, the cut-point of 1.10 showed the superior-to-inferior GCIPL ratio had a sensitivity of 60% and specificity of 98% for GON.

A practical guide to measuring optic disc size and its clinical correlation in diagnosing Glaucoma for the eye care professional

“…The innermost boundary of the reflective tissue, internal to any pigmented tissue and containing just neuroretinal tissue, is referred to as the disc's borders. The optic disc's size depends on the size of the scleral canal (Laowanapiban et al, 2022). Although the disc might be round, it usually has an oval shape that is vertically oriented, with the vertical diameter being approximately 9-10% bigger than the horizontal diameter.…”

“…The average optical disc has a horizontal diameter of 1.76 mm and a vertical of 1.92 mm in diameter. Larger discs are defined as >2.20 mm, while small discs are classified as 1.50 mm (Laowanapiban et al, 2022).…”

“…Evaluation of glaucoma risk and advancement can be done in several ways. Ocular coherence tomography, automated perimetry testing, and intraocular pressure (IOP) measuring are a few of these (Laowanapiban et al, 2022). Direct examination with a slit-lamp biomicroscope and condensing lens is one of the easiest and most effective techniques a doctor has at their disposal to evaluate the optic nerve.…”

“…Clinically, the CDR, in relation to disc size, helps diagnose tiny glaucomatous discs. To better understand the presence or risk of glaucoma, it is crucial to consider the size of the entire optic nerve head when measuring the CDR (Laowanapiban et al, 2022). This is because disc and cup size both have a high degree of variability, and a large cup does not necessarily mean that there has been glaucomatous damage.…”