Using CorvisST tonometry to assess glaucoma progression

<div><p>Purpose</p><p>To investigate the utility of the Corneal Visualization Scheimpflug Technology instrument (CST) to assess the progression of visual field (VF) damage in primary open angle glaucoma patients.</p><p>Method</p><p>A total of 75 eyes from 111 patients with primary open-angle glaucoma were investigated. All patients underwent at least nine VF measurements with the Humphrey Field Analyzer, CST measurements, axial length (AL), central corneal thickness (CCT) and intraocular pressure (IOP) with Goldmann applanation tonometry (GAT). Mean total deviation (mTD) progression rates of the eight VFs, excluding the first VF, were calculated and the association between progression rate and the other listed measurements was analyzed using linear regression, and the optimal to describe mTD progression rate was selected based on the second order bias corrected Akaike Information Criterion (AICc) index.</p><p>Results</p><p>VF progression was described best in a model that included CST parameters as well as other ocular measurements. The optimal linear model to describe mTD progression rate was given by the equation: -8.9–0.068 x mean GAT + 0.68 x A1 time + 0.31 x A2 time -0.39 x A2 length– 1.26 x highest deformation amplitude.</p><p>Conclusion</p><p>CST measurements are useful when assessing VF progression in glaucoma patients. In particular, careful consideration should be given to patients where: (i) an eye is observed to be applanated fast in the first and second applanations, (ii) the applanated area is wide in the second applanation and (iii) the indentation is deep at the maximum deformation, since these eyes appear to be at greater risk of VF progression.</p></div

Subject demographics.

<p>Subject demographics.</p

The association between photoreceptor layer thickness measured by optical coherence tomography and visual sensitivity in glaucomatous eyes

<div><p>Purpose</p><p>To assess the thickness of the photoreceptor layer in the macular region in glaucomatous eyes.</p><p>Method</p><p>Humphrey 10–2 visual field (VF) testing was carried out and mean threshold (mTH) was calculated in 118 eyes from 118 patients with open angle glaucoma. Macular optical coherence tomography (OCT) measurements (RS 3000, Nidek Co.ltd., Aichi, Japan) were also carried out in all eyes. Thickness measurements were recorded in the outer segment and retinal pigment epithelium (OS+RPE), the nerve fiber layer (NFL), the ganglion cell layer and inner plexiform layer (GCL+IPL), the inner nuclear layer and outer plexiform layer (INL+OPL) and the outer nuclear layer and inner segment (ONL+IS). The relationship between mTH and the thickness of these five different layers was investigated. Additionally, the influence of OS+RPE on mTH was investigated using partial correlation eliminating the effect of other variables of NFL, GCL+IPL, INL+OPL, ONL+IS, age, gender and axial length.</p><p>Results</p><p>The thickness of the OS+RPE layer was significantly decreased with the decrease of mTH (coefficient = 0.63 p <0.001). Partial correlation analysis suggested OS+RPE thickness is significantly (coefficient = 0.31, p <0.001) related to mTH, independent from NFL, GCL+IPL, INL+OPL, ONL+IS, age, gender and axial length.</p><p>Conclusions</p><p>The thickness of the RPE+OS layer appears to be related to visual sensitivity in glaucoma.</p></div

The Relationship between Corvis ST Tonometry and Ocular Response Analyzer Measurements in Eyes with Glaucoma

<div><p>It is important to compare the results of Corneal Visualization Scheimpflug Technology instrument (CST) measurements and Reichert Ocular Response Analyzer (ORA) parameters. The purpose of the study was to investigate the association between CST measurements and ORA parameters in ninety-five patients with primary open-angle glaucoma. Measurements of CST, ORA, axial length (AL), average corneal curvature (CC), central corneal thickness (CCT) and intraocular pressure (IOP) with Goldmann applanation tonometry (GAT) were carried out. The association between CST and ORA parameters was assessed using linear regression analysis, with model selection based on the second order bias corrected Akaike Information Criterion index. Measurements from ORA (corneal hysteresis [CH] and corneal response factor [CRF]) had high intraclass correlation coefficients (ICC) and low coefficients of variation, but some CST parameters showed much lower reproducibility, namely: A1 length, A2 length, highest concavity time and peak distance. Of 12 CST parameters tested, 8 were significantly correlated with CH and 10 were significantly correlated with CRF, however, the magnitude of the correlation coefficients were weak to moderate at best. The optimal model to explain CH using CST measurements was given by: CH = -76.3 + 4.6*A1 time + 1.9*A2 time + 3.1 * highest concavity deformation amplitude + 0.016*CCT (R² = 0.67, p <0.001). Similarly, the optimal model for CRF was given by: CRF = -53.5 + 4.2*A1 time + 1.9*A1 length + 20.8*A1 deformation amplitude + 0.8*A2 time + 0.017*CCT (R² = 0.73, p <0.001). ORA parameters show higher reproducibility than CST measurements. Although many CST parameters are significantly related to ORA parameters, the strengths of these relationships are weak to moderate.</p></div

Subjects demographics and comparison of variables between groups.

<p>Subjects demographics and comparison of variables between groups.</p

Subject demographics.

<p>Subject demographics.</p

Mean ± standard deviation of CST and ORA parameters and their intraclass correlation coefficient and coefficient of variation.

<p>Mean ± standard deviation of CST and ORA parameters and their intraclass correlation coefficient and coefficient of variation.</p

Macular retinal layer thickness measurements in a sample case.

<p>NFL: nerve fiber layer, GCL+IPL: ganglion cell and inner plexiform layer, INL: inner nuclear layer, OPL: outer plexiform layer, ONL+IS: outer nuclear layer and inner segment layer: OS+RPE outer segment layer and retinal pigment epithelium.</p

Correlation coefficients (with significance levels) between CST/ORA parameters and ocular and systemic parameters.

<p>Correlation coefficients (with significance levels) between CST/ORA parameters and ocular and systemic parameters.</p

The relationship between retinal layer thickness measurements and mTH (each thickness was analyzed in a separate linear model).

<p>The relationship between retinal layer thickness measurements and mTH (each thickness was analyzed in a separate linear model).</p