Influence of Myopia on Size of Optic Nerve Head and Retinal Nerve Fiber Layer Thickness Measured by Spectral Domain Optical Coherence Tomography.

PURPOSE: To investigate optic nerve head size and retinal nerve fiber layer (RNFL) thickness according to refractive status and axial length. METHODS: In a cross-sectional study, 252 eyes of 252 healthy volunteers underwent ocular biometry measurement as well as optic nerve head and RNFL imaging by spectral-domain optical coherence tomography. Correlation and linear regression analyses were performed for all subjects. The magnification effect was adjusted by the modified axial length method. RESULTS: Disc area and spherical equivalent were positively correlated (r = 0.225, r2 = 0.051, p = 0.000). RNFL thickness showed significant correlations with spherical equivalent (r = 0.359, r2 = 0.129, p = 0.000), axial length (r = -0.262, r2 = 0.069, p = 0.000), disc radius (r = 0.359, r2 = 0.129, p = 0.000), and radius of the scan circle (r = -0.262, r2 = 0.069, p = 0.000). After adjustment for the magnification effect, those relationships were reversed; RNFL thickness showed negative correlation with spherical equivalent and disc radius, and positive correlation with axial length and radius of the scan circle. The distance between the disc margin and the scan circle was closely correlated with RNFL thickness (r = -0.359, r2 = 0.129, p = 0.000), which showed a negative correlation with axial length (r = -0.262, r2 = 0.069, p = 0.000). CONCLUSIONS: Optic disc radius and RNFL thickness decreased in more severely myopic eyes, but they increased after adjustment for magnification effect. The error due to the magnification effect and optic nerve head size difference might be factors that should be considered when interpreting optical coherence tomography results.

Comparison of Intraocular Pressure Measurements Obtained by Rebound, Noncontact, and Goldmann Applanation Tonometry in Children.

PURPOSE: To compare intraocular pressure (IOP) among rebound, noncontact, and Goldmann applanation tonometry (GAT) and their relationships to central corneal thickness in children. DESIGN: Diagnostic protocol comparison and evaluation. METHODS: In right eyes of 419 children, mean IOP, rates of successful measurement with 3 tonometries, and intermethod agreement by Bland-Altman plot were assessed. The influences of central corneal thickness, and of average IOP of 3 tonometries on IOP differences between tonometries, were evaluated. RESULTS: The mean age was 8.89 ± 3.41 years (3-15 years). There was significant difference in mean IOP of each tonometry; GAT showed the lowest values (P < .05). The IOP was successfully measured by noncontact tonometry in 89%, by rebound tonometry in 75%, and by GAT in 64% of children less than 10 years old, and in 100%, 98%, and 94% of children older than 10 years, respectively. The IOP of each tonometer positively correlated with central corneal thickness (P < .05). The mean differences and limits of agreement were 0.81 ± 6.19 mm Hg (noncontact minus rebound), 2.56 ± 4.62 mm Hg (rebound minus GAT), and 1.81 ± 4.76 mm Hg (noncontact minus GAT). Rebound and noncontact tonometry overestimated IOP relative to GAT for thicker central corneal thicknesses. Rebound tonometry overestimated IOP relative to GAT and noncontact tonometry at higher average IOP of 3 tonometries. CONCLUSIONS: Rebound, noncontact, and Goldmann applanation tonometries can be considered appropriate methods for children, though noncontact tonometry is the most accessible. Given the risk of false-positive diagnosis of pediatric glaucoma, attention should be devoted to children with IOP within a suspicious range or thicker cornea.