Effect of Demographic Variables on the Regional Corneal Pachymetry.

PURPOSE: The measurement of corneal thickness by corneal pachymetry provides valuable information in the setting of corneal disease; however, spectral-domain optical coherence tomography (SD-OCT)-based assessment of different corneal sectors has been scarce in Pakistan. DESIGN: We aimed to obtain a whole-corneal thickness map using SD-OCT and to evaluate its correlation with age, sex, and axial length. METHODS: Our study included 214 subjects with healthy corneas; each eye was scanned with an SD-OCT covering a 9-mm diameter, and reproducibility was evaluated in a subset of 50 participants by means of an identical scan protocol repeated by 2 different OCT operators. RESULTS: Our analysis revealed corneal thickness to be thinnest inferotemporally whereas thickest in the superior and superonasal quadrants. No statistically significant differences could be detected between male and female participants with respect to corneal thickness, age, intraocular pressure, axial length, and refractive errors. However, we identified a significant negative correlation between age and corneal thickness in all corneal sections, excluding the inner and middle superior, inner superonasal, and inner and middle superotemporal quadrants. Conversely, the correlation between axial length and corneal thickness was found to be positive in the central region (P = 0.03, R = 0.149), the outer inferotemporal quadrant (P = 0.012, R = 0.171), throughout the temporal quadrant (P = 0.024, R = 0.154 for inner; P = 0.025, R = 0.153 for middle; P = 0.006, R = 0.186 for outer), and in the inner superotemporal quadrant (P = 0.018, R = 0.162). CONCLUSIONS: Different corneal sectors may interact heterogeneously with patient-related characteristics. This may provide incentive to evaluate whole-corneal thickness as a distinct parameter for clinical identification of disease processes.

Macular vascular density at the superficial capillary plexus using the optical coherence tomography angiography.

PURPOSE: The aim of this study was to assess the effects of age, gender, axial length and retinal thickness on the vascular density in a normal population using the Optovue optical coherence tomography angiography (OCT-A). METHODS: A total of 209 eyes of 209 healthy subjects were scanned using the OCT-A on an outpatient basis. Patients were 20-75 years of age. The built-in software covered a 3×3 mm circle centered at the macula. The circle was divided into five sectors: a 1 mm central foveal circle and an upper, lower, nasal and temporal sector each spanning 1-3 mm away from the central circle. The vascular density (VD) at the superficial capillary plexus was measured, which spanned from the inner limiting membrane to the inner plexiform layer. RESULTS: The fovea was the least dense area (32.5%±5.9%), and the temporal area was the densest (52.4%± 4.4%). Similarly, the fovea was the thinnest part of the retina (237.8±20.7 µm); however, the nasal sector was the thickest (308.5±15.1 µm). We found a correlation of the retinal thickness (r=0.541, P<0.001) with VD only at the fovea. Similarly, males had a greater density at the fovea (P=0.002). All regions significantly and negatively correlated with age even after adjusting for axial length. The age sees a decline in the density after the fifth decade where the variability also seems to increase. CONCLUSION: This study provides normative data for the Pakistani population. Additionally, it demonstrates that VD is affected by the retinal thickness at the fovea and the density begins to decline after the fifth decade.

Assessing reproducibility and the effects of demographic variables on the normal macular layers using the Spectralis SD-OCT.

PURPOSE: To quantify and view the possible influence of demographic variables on normal macular layers. Additionally, we wanted to assess the reproducibility using the Spectralis SD-OCT. METHODS: A Spectralis SD-OCT machine using a commercially available algorithm was used to scan 242 healthy subjects in an outpatient setting. We examined retinal thicknesses in seven layers: retinal nerve fiber layer (RNFL), ganglion cell layer (GCL), inner plexiform layer (IPL), inner nuclear layer (INL), outer plexiform layer (OPL), outer nuclear layer (ONL) and retinal pigment epithelium (RPE). Combined retinal thicknesses were expressed as inner retinal layer (IRL), photoreceptor layer (PL) and total retinal thickness (TRT). Measurements were taken from each of the nine sectors defined by the Early Treatment Diabetic Retinopathy Study; the center was the fovea, the inner circle (IC) was 1-3 mm away, and the outer circle (OC) was 3-6 mm away. RESULTS: The TRT was thickest inferiorly in the IC, and superiorly in the OC. The RNFL (P=0.030), GCL (P=0.006), IPL (P=0.006), IRL (P=0.030), PL (P<0.001) and TRT (P=0.001) were found to be thicker in males. The GCL (r=0.078, P=0.001), IPL (r=0.079, P=0.001), IRL (r=0.072, P=0.002), PL (r=0.076, P=0.001) and TRT (r=0.090, P<0.001) were found to decrease with age. The INL (r=0.060, P=0.010), ONL (r=0.078, P=0.001), and RPE (r=0.066, P=0.004) were inversely related to axial length. Excellent reproducibility was observed in all layers. CONCLUSION: Our study shows differences in various retinal layers according to age, gender, and axial length. Additionally, we demonstrate excellent reproducibility of this algorithm using the Spectralis SD-OCT.