Corneal Biomechanics Determination in Healthy Myopic Subjects

Purpose. To determine the corneal biomechanical properties by using the Ocular Response Analyzer™ and to investigate potential factors associated with the corneal biomechanics in healthy myopic subjects. Methods. 135 eyes from 135 healthy myopic subjects were included in this cross-sectional observational study. Cornea hysteresis (CH), corneal resistance factor (CRF), cornea-compensated intraocular pressure (IOPcc), and Goldmann-correlated intraocular pressure (IOPg) were determined with the Reichert Ocular Response Analyzer (ORA). Univariate and multivariate regression analyses were performed to investigate factors associated with corneal biomechanics. Results. The mean CH and CRF were 9.82±1.34 mmHg and 9.64±1.57 mmHg, respectively. In univariate regression analysis, CH was significantly correlated with axial length, refraction, central corneal thickness (CCT), and IOPg (r=-0.27, 0.23, 0.45, and 0.21, resp.; all with p≤0.015), but not with corneal curvature or age; CRF was significantly correlated with CCT and IOPg (r=0.52 and 0.70, resp.; all with p<0.001), but not with axial length/refraction, corneal curvature, or age. In multivariate regression analysis, axial length, IOPcc, and CCT were found to be independently associated with CH, while CCT and IOPg were associated with CRF. Conclusions. Both CH and CRF were positively correlated with CCT. Lower CH but not CRF was associated with increasing degree of myopia. Evaluation of corneal biomechanical properties should take CCT and myopic status into consideration

Relationship of corneal hysteresis and optic nerve parameters in healthy myopic subjects

Abstract The association between corneal biomechanical properties and glaucoma is an area of much interest. We determined the relationship between corneal hysteresis (CH) and optic nerve parameters in healthy myopic subjects in the current study. CH was measured with Reichert Ocular Response Analyzer in 108 eyes from 108 healthy myopic subjects. All subjects received retinal nerve fiber layer and optic disc imaging Cirrus HD-OCT, GDx ECC, and Heidelberg Retina Tomograph II. None of the tested optic nerve parameters showed statistical significance with CH by using correlation analysis. For RNFL parameters, there was a negative but not statistically significant correlation between CH and average RNFL thickness obtained with OCT (r = −0.15, p = 0.13). For optic disc parameters, there was a negative but not statistically significant correlation between CH and rim area measured with OCT (r = −0.10, p = 0.29). The current study did not find any statistically significant relationship between CH and optic nerve parameters as measured by all three imaging modalities in healthy myopic eyes. Therefore, the relationship observed previously in glaucoma subjects is likely coming to fruition as optic nerve damage is caused by the disease

Influence of optic disc-fovea distance on macular thickness measurements with OCT in healthy myopic eyes

Assessment of macular thickness is important in the evaluation of various eye diseases. This study aimed to determine the influence of the optic disc-fovea distance (DFD) on macular thickness in myopic eyes. We determined the DFD and the macular thickness in 138 eyes from 138 healthy myopic subjects using the Cirrus HD-OCT. Correlation analysis and multiple linear regression were performed to determine the influence of DFD, axial length, disc area, and β-PPA on macular thickness. To further remove the confounding effect of ocular magnification on the DFD and OCT scan area, a subgroup analysis was performed in eyes with a limited axial length range (24-25 mm). DFD was significantly correlated with both regional (central, inner, and outer ETDRS subfields) and overall average macular thickness at a Bonferroni corrected P value of 0.004 (r ranging from-0.27 to-0.47), except for the temporal outer (r =-0.15, P = 0.089) and inferior outer (r =-0.22, P = 0.011) macular thickness. In the multivariable analysis, DFD was significantly associated with the average inner and outer macular thickness, the central subfield thickness, and the overall macular thickness (all P < 0.001), independent of ocular magnification and other covariates. Our findings indicate that eyes with a greater DFD have a lower macular thickness

Influence of the Retinal Blood Vessel Topography on the Variability of the Retinal Nerve Fiber Bundle Trajectories in the Human Retina

PURPOSE. To determine the relationship between the retinal blood vessel topography and the retinal nerve fiber bundle (RNFB) trajectories in the human retina. METHODS. A previously collected dataset comprising 28 fundus photographs with traced RNFB trajectories was used. For all traced trajectories, the departure from our previously published RNFB trajectory model was calculated. Subsequently, we calculated, per subject, a "mean departure" for the superior-temporal and inferior-temporal region. We measured angles between a line connecting the optic nerve head (ONH) center and the fovea and lines connecting the ONH center and the crossings of the superior and inferior temporal arteries (arterial angles) and veins (venous angles) with circles around the ONH; circle radii were 25%, 50%, and 100% of the ONH center-to-fovea distance. We also defined two angles based on the location of the first arteriovenous crossing. Multiple linear regression analysis was performed with mean departure as dependent variable and refraction, ONH inclination, and vessel angles as independent variables. RESULTS. In the superior-temporal region, refraction (P = 0.017), ONH inclination (P = 0.021), and the arterial angle corresponding to the middle circle (P <0.001) were significant determinants of mean departure. Explained variance was 0.54. In the inferior-temporal region, the arterial angle corresponding to the largest circle (P = 0.002) was significant. Explained variance was 0.32. CONCLUSIONS. The retinal blood vessel topography explains a significant part of the RNFB trajectory variability but only if (1) the vessel topography is assessed at an appropriate distance from the ONH and (2) the superior and inferior hemifield are addressed independently

Influence of the Retinal Blood Vessel Topography on the Variability of the Retinal Nerve Fiber Bundle Trajectories in the Human Retina

Citation: Qiu K, Schiefer J, Nevalainen J, Schiefer U, Jansonius NM. Influence of the retinal blood vessel topography on the variability of the retinal nerve fiber bundle trajectories in the human retina. Invest Ophthalmol Vis Sci. 2015;56:6320-6325. DOI:10.1167/ iovs.15-17450 PURPOSE. To determine the relationship between the retinal blood vessel topography and the retinal nerve fiber bundle (RNFB) trajectories in the human retina. METHODS. A previously collected dataset comprising 28 fundus photographs with traced RNFB trajectories was used. For all traced trajectories, the departure from our previously published RNFB trajectory model was calculated. Subsequently, we calculated, per subject, a &apos;&apos;mean departure&apos;&apos; for the superior-temporal and inferior-temporal region. We measured angles between a line connecting the optic nerve head (ONH) center and the fovea and lines connecting the ONH center and the crossings of the superior and inferior temporal arteries (arterial angles) and veins (venous angles) with circles around the ONH; circle radii were 25%, 50%, and 100% of the ONH center-to-fovea distance. We also defined two angles based on the location of the first arteriovenous crossing. Multiple linear regression analysis was performed with mean departure as dependent variable and refraction, ONH inclination, and vessel angles as independent variables. RESULTS. In the superior-temporal region, refraction (P ¼ 0.017), ONH inclination (P ¼ 0.021), and the arterial angle corresponding to the middle circle (P &lt; 0.001) were significant determinants of mean departure. Explained variance was 0.54. In the inferior-temporal region, the arterial angle corresponding to the largest circle (P ¼ 0.002) was significant. Explained variance was 0.32. CONCLUSIONS. The retinal blood vessel topography explains a significant part of the RNFB trajectory variability but only if (1) the vessel topography is assessed at an appropriate distance from the ONH and (2) the superior and inferior hemifield are addressed independently. Keywords: retinal nerve fiber layer, retinal vessels, retinal vasculature G laucoma is one of the important causes of blindness, with irreversible damage to retinal ganglion cells, the retinal nerve fiber layer (RNFL), and the optic nerve as its pathological features. The detection of changes in these structures is part of the diagnostic armamentarium in glaucoma; a detailed anatomical knowledge of especially the retinal nerve fiber bundle (RNFB) trajectories is helpful to integrate information from each structure and to topographically correlate it with visual field data. In 2000, Garway-Heath et al. 1 reported nerve fiber bundle trajectories based on fundus photographs. Later, models based on axonal growth and maps based on the correspondence between optical coherence tomography thickness measurements and visual field data were published. It has been reported that the vascular and neuronal systems share many similarities. The blood vessels and nerves tend to develop in relative proximity, throughout the body of any species in general and in the primate retina in particular. 12 By using scanning laser polarimetry, Resch et al

Application of the ISNT rules on retinal nerve fibre layer thickness and neuroretinal rim area in healthy myopic eyes

PurposeWe determined the applicability of inferior>superior>nasal>temporal (ISNT) rules on retinal nerve fibre layer (RNFL) thickness and rim area and evaluated the impact of various ocular factors on the performance of the ISNT rules in healthy myopic eyes. MethodsA total of 138 eyes from 138 healthy myopic subjects were included in this cross-sectional observational study. The peripapillary RNFL and optic disc in each eye were imaged with Cirrus HD optical coherence tomography (OCT) and Heidelberg Retina Tomograph II (HRT2), respectively. The performance of the inferior>superior (IS), inferior>superior>nasal>temporal (IST) and ISNT rules on RNFL thickness and rim area was determined and compared between low-to-moderate myopia and high myopia. The effects of ocular factors [including axial length, disc area, disc tilt, disc torsion, disc-fovea angle (DFA) and retina artery angle] on the performance of ISNT rules were evaluated with logistic regression analysis. ResultsThe mean axial length and refractive error were 25.571.09mm (range, 22.52-28.77mm) and -5.12 +/- 2.30D [range, -9.63 to -0.50dioptres (D)], respectively. Sixty-three per cent of the healthy eyes were compliant with the ISNT rule on rim area, while ISNT rule on RNFL thickness was followed in only 11.6% of the included eyes. For rim area, smaller disc area was significantly associated with increased compliance of the IS rule (odds ratio: 0.46, p=0.039), IST rule (odds ratio: 0.46, p=0.037) and ISNT rule (odds ratio: 0.44, p=0.030). For RNFL thickness, greater DFA was significantly associated with increased compliance of the IS and IST rules (odds ratio: 1.30, p ConclusionIn healthy myopic subjects, 88.4% and 37% of eyes did not comply with the ISNT rule on RNFL thickness and rim area, respectively. Due to significant low compliance in healthy eyes, the ISNT rule and its variants have limited potential utility in diagnosing glaucoma in myopic subjects