Retinal Nerve Fibre Layer Assessment in Glaucoma and Glaucoma Suspect by Optical Coherence Tomography (OCT)

Background Glaucoma is a progressive optic neuropathy characterized by structural changes in the optic nerve head, retinal nerve fiber layer (RNFL) defect, and accompanying visual field damage (VFD). In glaucoma management, detecting progression is essential in both early and late stages of the disease. In patients with an established diagnosis of glaucoma, evidence of progression will influence a clinician’s decision whether to modify glaucoma therapy. In patients who are suspected of having the disease, progression detection can confirm the diagnosis, and help decide how to manage the patient. Although standard automated perimetry has been the most commonly used test to monitor glaucomatous progression, evidence suggests that in some eyes substantial structural damage can be detected before the development of clinically detectable VFD. Objective To compare retinal nerve fibre layer thickness between glaucoma and glaucoma suspects. Methods We conducted our cross sectional comparative study on Forty eight eyes from patients recruited from Ain Shams University Hospitals, Ophthalmology Department during the period from February 2019 to December 2019. The Forty eight eyes were recruited in this study and divided into 2 groups. Group A- (Twenty-four eyes with moderate open angle glaucoma) and Group B- (Twenty four eyes with criteria of glaucoma suspects). Results There was highly Significant difference as regards OCT parameters of the patients (p < 0.001 for all). As the mean value of Cup/disc ratio was lower in Glaucoma Suspected cases, while Total RNFL, RNFL Superior and RNFL Inferior was higher in Glaucoma Suspected cases than patients with Moderate glaucoma. This study showed that; by using ROC-curve analysis, cup to disc ratio (CDR) at a cutoff point (>0.59) detected patients with glaucoma, with excellent accuracy, sensitivity= 95% and specificity= 100%. Also, by using ROC-curve analysis, superior RNFL at a cutoff point (≤116) detected patients with glaucoma, with fair accuracy, sensitivity= 66% and specificity= 91%. While inferior RNFL at a cutoff point (≤113) detected patients with glaucoma, with good accuracy, sensitivity= 70% and specificity= 95%. Conclusion In conclusion, structural progression measured using SD OCT was associated with functional progression shown in VF loss in glaucoma suspect or preperimetric glaucoma eyes and in glaucomatous eyes. Average, inferior and superior RNFL attenuations were the most important risk factors for visual field progression.