Optical Coherence Tomography Interpretation for Glaucoma

Structural glaucomatous changes occur more frequently in the earlier stages of glaucoma than functional defects so we should give special care on oct (optical coherence tomography) importance as the best current method. RNFL change detection are more useful in early glaucoma, GCC in moderate to advanced glaucoma while visual field test is more useful in advanced stages but overall using a combination of RNFL, ONH and macular measurement modalities is recommended for glaucoma evaluation because each of these parameters may be affected earlier than the others so, taking into account the findings from the RNFL, ONH and macula enhances early diagnosis of glaucoma

A Comparative Analysis of Ganglion Cell Complex Parameters in Nigerian Negroes with Glaucoma and Macular Disease

Aim: To evaluate the differences between ganglion cell complex (GCC) of primary open angle glaucoma and ocular disorders affecting the macula.Methods and Materials: Forty-seven patients diagnosed with primary open angle glaucoma and 27 patients with macular diseases of different aetiology were enrolled in this pilot study. All patients underwent direct GCC analysis with the optical coherence tomographic scan, using the Optovue Fourier Domain RTVue-version. A comparison of the average GCC thickness, focal loss volume (FLV) and the global loss volume (GLV) of thetwo groups was made.Results: A total of 74 pairs of eyes were included in the study. This comprised 48 males and 26 females with a mean age of 53.8 ± 11.3 among glaucoma patients and 59.8 ± 9.8 among patients with macular disease. Eyes with macular disease (33.3%) and eyes with glaucoma(42.6%) had abnormal average GCC parameters. However, the mean average GCC value was significantly higher in eyes with macular disease (87.50 ± 20.73) when compared with eyes with glaucoma (76.55± 12.51) (p=0.01). A significantly higher percentage of eyes with macular disease (43.3%) had GLV values within normal range when compared with eyes with glaucoma (21.3%) (p=0.03). Abnormal FLV values were seen in both eyes with macular disease (83.3%) and eyes with glaucoma (80.9%) but the differences were not of statistical significance (p= 0.24).Conclusion: This pilot study demonstrated abnormal OCT GCC values in eyes with glaucoma as well as in eyes with macular disease. However, eyes with macular disease had significantly higher mean average GCC parameters but GLV parameters that were within normal values.Key words: glaucoma, macular disease, ganglion cell comple

Ganglion cell complex analysis in glaucoma patients: what can it tell us?

Glaucoma is a group of optic neuropathies characterized by a progressive degeneration of retina ganglion cells (RGCs) and their axons that precedes functional changes detected on the visual field. The macular ganglion cell complex (GCC), available in commercial Fourier-domain optical coherence tomography, allows the quantification of the innermost retinal layers that are potentially involved in the glaucomatous damage, including the retinal nerve fiber (RNFL), ganglion cell and inner plexiform layers. The average GCC thickness and its related parameters represent a reliable biomarker in detecting preperimetric glaucomatous damage. The most accurate GCC parameters are represented by average and inferior GCC thicknesses, and they can be associated with progressive visual field loss. Although the diagnostic accuracy increases with more severe glaucomatous damage and higher signal strength values, it is not affected by increasing axial length, resulting in a more accurate discrimination of glaucomatous damage in myopic eyes with respect to the traditional RNFL thickness. The analysis of the structure-function relationship revealed a good agreement between the loss in retinal sensitivity and GCC thickness. The use of a 10-2° visual field grid, adjusted for the anatomical RGCs displacement, describes more accurately the relationship between RGCs thickness and visual field sensitivity loss

Role of Optical Coherence Tomography in the Evaluation and Management of Glaucoma

Glaucoma is the leading cause of irreversible, yet preventable, blindness throughout the world. Since it is a disease which can be treated but not cured, it is crucial for the treating ophthalmologist to catch the disease as early as possible. The diagnosis of glaucoma is currently based on the appearance of the optic disc and standard achromatic perimetry. However, to detect glaucoma in its early stages, there are various diagnostic modalities of which optical coherence tomography serves as a novel tool. Optical coherence tomography has emerged over the years with the ability to detect changes in the optic nerve head, retinal nerve fiber layer, and currently the ganglion cell layer much earlier than the defects manifest functionally. Thus, optical coherence tomography acts as an important diagnostic aid to diagnose and monitor the progression of this sight threatening disease called glaucoma

In Vivo Evaluation of Retinal Neurodegeneration in Patients with Multiple Sclerosis

To evaluate macular morphology in the eyes of patients with multiple sclerosis (MS) with or without optic neuritis (ON) in previous history.Optical coherence tomography (OCT) examination was performed in thirty-nine patients with MS and in thirty-three healthy subjects. The raw macular OCT data were processed using OCTRIMA software. The circumpapillary retinal nerve fiber layer (RNFL) thickness and the weighted mean thickness of the total retina and 6 intraretinal layers were obtained for each eye. The eyes of MS patients were divided into a group of 39 ON-affected eyes, and into a group of 34 eyes with no history of ON for the statistical analyses. Receiver operating characteristic (ROC) curves were constructed to determine which parameter can discriminate best between the non-affected group and controls.The circumpapillary RNFL thickness was significantly decreased in the non-affected eyes compared to controls group only in the temporal quadrant (p = 0.001) while it was decreased in the affected eyes of the MS patients in all quadrants compared to the non-affected eyes (p<0.05 in each comparison). The thickness of the total retina, RNFL, ganglion cell layer and inner plexiform layer complex (GCL+IPL) and ganglion cell complex (GCC, comprising the RNFL and GCL+IPL) in the macula was significantly decreased in the non-affected eyes compared to controls (p<0.05 for each comparison) and in the ON-affected eyes compared to the non-affected eyes (p<0.001 for each comparison). The largest area under the ROC curve (0.892) was obtained for the weighted mean thickness of the GCC. The EDSS score showed the strongest correlation with the GCL+IPL and GCC thickness (p = 0.007, r = 0.43 for both variables).Thinning of the inner retinal layers is present in eyes of MS patients regardless of previous ON. Macular OCT image segmentation might provide a better insight into the pathology of neuronal loss and could therefore play an important role in the diagnosis and follow-up of patients with MS

OCT in Glaucoma Diagnosis, Detection and Screening

Glaucoma is a chronic and progressive optic neuropathy in which increased intraocular pressure is the most important risk factor in the etiopathogenesis. The basic pathology is the progressive loss of retinal ganglion cells (RGCs) especially the death of the axons of ganglion cells initially (apoptosis), followed by peripapillary retinal nerve fiber layer (RNFL) defects. Since optical coherence tomography (OCT)’s first demonstration in 1991 by Huang et al. and introduction commercially in 1996, it began gaining popularity in 2000s for retinal evaluation and the detection, diagnosis, and follow-up of glaucoma. Previously available OCT instruments used a technique referred to as time-domain (TD-) OCT, followed by spectral-domain (SD-) OCT, which has an increased scan acquisition rate, allowing for a more detailed sampling of the area of interest. Recently, swept-source OCT (SS-OCT), a newer generation of OCT, has been introduced. Clinical assessment using multiple parameters, including peripapillary RNFL, ganglion cells, optic nerve head, and macular parameters, has proven useful for managing and diagnosing glaucoma as well as for evaluating risk in glaucoma suspects. In this chapter, we aim to evaluate the use of OCT and its modalities in diagnosis, screening, and progression of glaucoma

Tools for creating wide-field views of the human retina using Optical Coherence Tomography

Optical Coherence Tomography (OCT) has allowed in-vivo viewing of details of retinal layers like never before. With the development of spectral domain OCT (SD-OCT) details of nearly 2µm axial resolution and higher imaging speed have been reported. Nevertheless, a single volume scan of the retina is typically restricted to 6mm x 6mm in size. Having a larger field of view of the retina will definitely enhance the clinical utility of the OCT. A tool was developed for creating wide-field thickness maps of the retina by combining the use of already available tools like i2k Retina (DualAlign, LLC, Clifton Park, NY) and the thickness maps from Cirrus HD-OCT research browser (Carl Zeiss Meditec, Dublin, California, USA). Normal subjects (n=20) were imaged on Zeiss Cirrus HD-OCT using 512x128 Macular Cube scanning protocol. Sixteen overlapping volumetric images were obtained by moving the internal fixation target around such that the final stitched maps were 12mm x 14mm in size. The thickness maps were corrected for inter-individual differences in axial lengths measured using Zeiss IOL Master and averaged to obtain a normative map. An algorithm was also developed for montaging 3-D volume scans. Using this algorithm two OCT volume scans can be registered and stitched together to obtain a larger volume scan. The algorithm can be described as a two step process involving 3-D phase-correlation and 2-D Pseudo-polar Fourier transform (PPFT). In the first step, 3-D phase-correlation provides translation values in the x, y and z axis. The second step involves applying PPFT on each overlapping pair of B-scans to find rotation in the x-y plane. Subsequent volumes can be stitched to obtain a large field of view. We developed a simple and robust method for creating wide-field views of the retina using existing SD-OCT hardware. As segmentation algorithms improve, this method could be expanded to produce wide-field maps of retinal sub-layers, such as the outer nuclear layer or retinal nerve fiber layer. These wide-field views of the retina may prove useful in evaluating retinal diseases involving the peripheral retina (e.g., retinitis pigmentosa and glaucoma)