Mapping of Macular Substructures with Optical Coherence Tomography for Glaucoma Diagnosis

Abstract

Purpose-To use optical coherence tomography (OCT) to identify the specific retinal layers and macular regions damaged in glaucoma. Design-Observational cross-sectional study.Participants-One hundred forty-nine participants in the Advanced Imaging for Glaucoma Study, divided into 3 groups: normal (N) perimetric glaucoma (PG), and glaucoma suspect and preperimetric glaucoma (GSPPG) with 44, 73, and 29 persons, respectively. Methods-TheZeiss Stratus OCT system (Carl Zeiss Meditec, Inc., Dublin, CA) was used to map the macula over a 6-mm diameter and to scan the circumpapillary nerve fiber layer (cpNFL). The macular OCT images were exported for automatic segmentation using software developed by the authors. The thickness of the macular nerve fiber layer (mNFL), ganglion cell layer (mGCL), inner plexiform layer (mIPL), inner nuclear layer (mINL), outer retinal layer (mORL), and total retinal thickness were measured. Thickness measurements of GSPPG and PG eyes were compared with those of N eyes. The ability to differentiate between GSPPG and PG eyes against N eyes was assessed by fractional loss, standardized deviation, and the area under the receiver operating characteristic curve.Main Outcome Measures-Area-weighted average thicknesses of retinal sublayers in the macula.Results-The mNFL, mGCL, mIPL, and mINL were significantly (P<0.001) thinner in both the GSPPG and PG eyes than in the N eyes. In PG eyes, mNFL, mGCL, and mIPL thinning was most severe (approximately 20%), mINL thinning was intermediate (7%), and mORL thinning was minimal (3%). The repeatability (coefficient of variation and intraclass correlation) of thickness measurements was improved by combining the mNFL, mGCL, and mIPL measurements as the inner retinal layer (mIRL). The mIRL was the best macular parameter for glaucoma diagnosis and had discriminant power comparable with that of the cpNFL. The fractional loss of mIRL thickness was most severe in the inferior perifoveal region for both the PG and GSPPG groups.Conclusions-Glaucoma leads to thinning of the mNFL, mGCL, mIPL, and mINL, even before detectable visual field changes occur. A combination of the 3 innermost layers seems to provide optimal glaucoma detection. Increasing the sampling of peripheral macula with a new OCT scan pattern may improve glaucoma diagnosis further.Glaucoma is an optic neuropathy characterized by an irreversible loss of neural tissue and visual field function. Early detection of the disease or its progression is important in Advanced imaging systems such as optical coherence tomography (OCT), scanning laser polarimetry, and scanning laser tomography can measure objectively both retinal NFL thickness and optic disc contour.The macular region does not undergo clinically observable change with glaucoma. But the development of more sensitive measurement technology has sparked interest in investigating this area for glaucoma diagnosis. Zeimer 5-7 hypothesized that macular thickness was important because the retinal ganglion cell layer consists of the cell bodies of reti...

Diagnostic ability of retinal nerve fiber layer maps to detect localized retinal nerve fiber layer defects

“…The outer retinal layers are hardly affected in glaucoma, whereas the GCL and IPL of the retina, as well as the RNFL, are affected in glaucoma. 11 Recent studies reported that imaging of the macular RNFL is an effective means of detecting macular RNFL defects. 18 The mean thickness of the three innermost retinal layers is comparable with the cpRNFL thickness in discriminating whether glaucoma is present.…”

“…Glaucoma leads to thinning of the macular nerve fiber layer (NFL), ganglion cell layer (GCL), and inner plexiform layer (IPL). 10,11 Most of the commercial SD-OCTs can measure these three innermost layers (ganglion cell complex (GCC)) and can detect RNFL defects in GCC substructure imaging.…”

Structural and functional assessment by hemispheric asymmetry testing of the macular region in preperimetric glaucoma

“…The introduction of spectral domain optical coherence tomography (SD-OCT) allows us to measure the ganglion cell complex (GCC, the combination of retinal nerve fiber, retinal ganglion cell and inner plexiform layers) covering the central macula. Previous studies demonstrated that GCC thickness was significantly lower in glaucomatous eyes with visual field defects than in healthy eyes [13,14]. A number of studies report a high correlation between global visual field sensitivity and GCC in glaucomatous subjects using SD-OCT [15,16].…”

Optical coherence tomography—current technology and applications in clinical and biomedical research

“…OCT is the clinical standard for a number of retinal diseases and is increasingly being used for diagnosis, monitoring and treatment control of vitreoretinal traction and macular holes [143], age related macular degeneration [144], glaucoma [145] and diabetic retinopathy [146,147]. Recent reviews giving comprehensive description of ophthalmic OCT were published by van Velthoven et al [148] and Drexler and Fujimoto [149].…”

“…The diagnosis of glaucoma in early stages is difficult and is based on visual fields defects, i. e. the diagnosis is made when damage has already occurred. Recent studies have shown that OCT can detect the thinning of the retinal nerve fiber layer which typically precedes the loss of visual field [145,155,156]. With continuing improvement of resolution and speed, OCT will likely become a valuable tool for early stage glaucoma detection.…”