- Study Design
A prospective observational comparative study was conducted on patients with POAG (controlled on medical treatment) versus non-glaucomatous patients of the same age group.
- Patient Selection
After the approval of the Human Ethical Committee in Sohag faculty of Medicine; written consent was taken from all patients who participated in this study after explanation of the procedure and nature of the disease. The tenets of the Helsinki Declaration were followed.
The study included 130 eyes of 130 subjects, 70 were eyes with POAG (glaucoma group) , 60 were healthy eyes (control group). The right eye was included in the control and glaucoma groups. In the glaucoma group, IOP was controlled for at least 6 months with one or more of the following anti-glaucoma medications (Prostaglandin analogs, Beta-blockers, Alpha agonists, Carbonic anhydrase inhibitor eye drops). The study population attended to Sohag ophthalmic investigation center for their routine scheduled follow up (VF, OCT PRNFL, and macular GCC) in the period from June 2019 to December 2019.
Glaucoma Staging System 2 (GSS 2) was used for the classification of glaucoma, it is based on two main perimetric global indices Mean Deviation [MD] and Pattern Standard Deviation [PSD], plotted on an X-Y coordinate. It classifies visual field defects in 6 stages (stage 0 which includes normal population, a borderline stage which is a stage defined between stage 0 and one, and 5 consecutive stages from (1:5) according to damage severity. Classification also includes 3 types of defects (generalized, localized, and mixed). 15
In this study, we considered stages one and two GSS2 as an early stage (40 eyes) and groups three, four, and five GSS2 an advanced group of glaucoma (30 eyes).
Sixty control subjects were the relatives of the patients and workers in Sohag ophthalmic investigations center of the same age group. The control group was examined two times for IOP measurement in two different occasions. They were also tested for VF, RNFL thickness to exclude normal tension glaucoma.
Inclusion Criteria:
Eyes with medically controlled IOP measurement for at least six months (15.5 mm Hg +/- 2.6 mm Hg) by Goldman applanation tonometry 16.Eyes with cup/disc ratio (C/D) ratio ≥ 0.7, or asymmetry > 0.2, or difference in Vertical (C/D) and Horizontal (C/D) > 0.2. Notching, or disc hemorrhage, or excavation reaching disc margin. Glaucomatous visual field (VF) changes (stages 1:5 according to GSS2). Peripapillary RNFL thinning. Visual acuity (VA) of 0.4 Log MAR or more were included.
Exclusion Criteria:
Eyes with juvenile open-angle glaucoma, angle-closure glaucoma, normal-tension glaucoma, pseudo exfoliation syndrome (PEX). chronic contact lens wearers, ametropia > +/- 6D, myopic fundus changes, media opacities, any neurological disorders, previous operations or retinal pathologies, unreliable VF tests, and OCT images of signal strength less than 60 17.
All eyes were subjected to VF examination using standard automated perimetry (SAP) Humphrey Field Analyzer (HFA) II 750 (Carl Zeiss Meditec Inc., Dublin, California) 30-2 test with Standard Swedish Interactive Thresholding Algorithm (SITA) Strategy. SAP tests were classified following Anderson and Patella criteria.
OCT of the optic disc (ONH/RNFL scan) and macular ganglion cell layer (GCC, ganglion cell complex segmentation) was performed using RTVue (Optovue Inc., Fermont, CA).
Specular microscopy (SP-2000P; TOPCON, Tokyo, Japan). Images were captured from the central cornea (central measurement) and analyzed using IMAGEnet 2000 software (TOPCON). Endothelial (CED), (HEX%), and (CV%) were determined. All examinations were performed by the same examiner who was masked to the participant’s condition. Multiple images are taken by a central view for each eye to obtain a clear image of a good quality of the central endothelium, in which the centers of at least 100 contiguous endothelial cells were marked using software available in the system with clear cell boundaries.
- Statistics:
Software version (26.0) (SPSS, Inc., Chicago, IL, USA) was used. All participants were chosen by using the systematic random sample technique from the attendees who fulfilled the inclusion criteria.
The data were tested for normality using the Kolmogorov-Smirnov test and for homogeneity variances before further statistical analysis.
Differences between groups for continuous measures were analyzed by an independent sample t-test and the chi-squared test for categorical measures. Z test was used to compare 2 proportions.
Pearson’s correlation coefficients (r) were used to assess the correlations between variables of corneal parameters, VF, and OCT disc parameters. A p-value ≤ 0.05 was considered statistically significant.