Stella N. Arthur

The location of the inferior and superior temporal blood vessels and interindividual variability of the retinal nerve fiber layer thickness.

PurposeTo determine if adjusting for blood vessel (BV) location can decrease the intersubject variability of retinal nerve fiber layer (RNFL) thickness measured with optical coherence tomography (OCT). Subjects and MethodsOne eye of 50 individuals with normal vision was tested with OCT and scanning laser polarimetry (SLP). The SLP and OCT RNFL thickness profiles were determined for a peripapillary circle 3.4 mm in diameter. The midpoints between the superior temporal vein and artery (STva) and the inferior temporal vein and artery (ITva) were determined at the location where the vessels cross the 3.4 mm circle. The average OCT and SLP RNFL thicknesses for quadrants and arcuate sectors of the lower and upper optic disc were obtained before and after adjusting for BV location. This adjustment was carried out by shifting the RNFL profiles based upon the locations of the STva and ITva relative to the mean locations of all 50 individuals. ResultsBlood vessel locations ranged over 39 (STva) and 33 degrees (ITva) for the 50 eyes. The location of the leading edge of the OCT and SLP profiles was correlated with the location of the BVs for both the superior [r=0.72 (OCT) and 0.72 (SLP)] and inferior [r=0.34 and 0.43] temporal vessels. However, the variability in the OCT and SLP thickness measurements showed little change due to shifting. After shifting, the difference in the coefficient of variation ranged from −2.1% (shifted less variable) to +1.7% (unshifted less variable). ConclusionsThe shape of the OCT and SLP RNFL profiles varied systematically with the location of the superior and inferior superior veins and arteries. However, adjusting for the location of these major temporal BVs did not decrease the variability for measures of OCT or SLP RNFL thickness.

Update on the role of alpha-agonists in glaucoma management

Glaucoma is the second most common cause of world blindness (following cataract) with estimated cases reaching 79.6 million by 2020. Although the etiology of glaucoma is multi-factorial, intraocular pressure (IOP) is the only modifiable factor in glaucoma management proven to alter the natural course of the disease. Among various classes of IOP-lowering medications currently available, alpha-adrenergic receptor agonists are used either as monotherapy, as second-line therapy, or in fixed combination with beta-blockers. Non-selective adrenergic agonists such as epinephrine and dipivefrin are infrequently used today for the treatment of glaucoma or ocular hypertension, and have been replaced by the alpha-2-selective agonists. The use of apraclonidine for IOP reduction in glaucoma or OHT is limited due to a high rate of follicular conjunctivitis. The alpha-2-selective agonist in use today is brimonidine. The brimonidine-purite formulations are preferred to brimonidine-benzalkonium chloride (BAC) formulations due better tolerability while maintaining similar efficacy. Brimonidine is also effective when used in combination with a beta-blocker. Using brimonidine-timolol fixed combination (BTFC) as first-line therapy has an added potential for neuroprotection. This would be a valuable strategy for glaucoma treatment, for patients who are intolerant of prostaglandin analogs, or for patients where prostaglandin analogues are contraindicated as first-line therapy, such as in patients with inflammatory glaucoma.

Optic nerve diffusion tensor imaging parameters and their correlation with optic disc topography and disease severity in adult glaucoma patients and controls.

Purpose:To evaluate optic nerve diffusion tensor imaging (DTI) parameters in glaucoma patients and controls, and to correlate DTI parameters with the rim area obtained with Heidelberg retina tomography (HRT) and with the severity of glaucomatous damage using the Glaucoma Staging System. Design:Pilot study. Methods:Twenty-seven patients with glaucoma and 12 control subjects underwent DTI and HRT imaging. Main outcome measures included: fractional anisotropy, mean diffusivity, axial diffusivity, radial diffusivity, HRT rim area, and Glaucoma Staging System stage. Results:In group comparison, mean diffusivity (1.33 vs. 0.91 &mgr;m2/ms, P=0.0002), axial diffusivity (1.70 vs. 1.43 &mgr;m2/ms, P=0.036), and radial diffusivity (1.24 vs. 0.71 &mgr;m2/ms, P<0.0001) were significantly higher and fractional anisotropy (0.21 vs. 0.44, P<0.0001) was significantly lower in the glaucoma compared with those of control subjects. In glaucoma patients, mean, axial, and radial diffusivities increased and fractional anisotropy decreased as rim area decreases and the Glaucoma stage increased (P<0.05). However, there were no statistically significant differences in the DTI parameters when adjacent pairs of stages were compared (P>0.05). Conclusions:DTI may be a useful technique for detection and evaluation of glaucomatous damage in the optic nerve, particularly for patients in whom conventional imaging and perimetry are not possible. Future studies are needed to evaluate how DTI parameters change longitudinally with glaucomatous damage within the visual pathways and address cerebrospinal fluid partial volume effects in diffusion tensor quantification, especially for patients with advanced glaucoma stage.

Efficacy, safety, and survival rates of IOP-lowering effect of phacoemulsification alone or combined with canaloplasty in glaucoma patients.

Purpose:To evaluate efficacy and survival rates of intraocular pressure (IOP)-lowering effect obtained with phacoemulsification (phaco) alone or in combination with canaloplasty (PCP) in patients with open-angle glaucoma (OAG). Methods:Retrospective chart review of consecutive cases at the Department of Ophthalmology, Indiana University. Visual acuity (VA), IOP, number of medications (Meds), failures, and survival rates of IOP-lowering effect were analyzed. Inclusion criteria were: patients older than 18 years with OAG and cataract. Exclusion criteria were: no light perception vision, prior glaucoma surgery, chronic uveitis, angle-closure glaucoma, and advanced-stage or end-stage OAG. Failure criteria were: IOP>21 mm Hg or <20% reduction, IOP<6 mm Hg, further glaucoma surgeries, and loss of light perception vision. Results:Thirty-seven patients underwent phaco and 32 patients had PCP. Follow-up was 21.8±10.1 versus 18.8±9.6 months for phaco and PCP, respectively (P=0.21). Age (y) (74.7±9.8 vs. 76.1±8.3, P=0.54), sex (P=81), and laser status (P=0.75) were similar between the groups. Preoperatively, mean±SD logMAR VA (0.5±0.7 vs. 0.5±0.5, P=0.77), IOP (16.2±4.6 vs. 18.2±5.1, P=0.13), and Meds (1.4±1.1 vs. 1.3±0.7, P=0.75) were similar for phaco and PCP, respectively. At 24-month phaco (n=17) and PCP (n=11), respectively, mean±SD were: logMAR VA 0.2±0.2 versus 0.4±0.7, P=0.29; IOP 14.1±4.0 versus 12.9±3.8, P=0.43; and Meds 1.5±1.2 versus 0.3±0.5, P=0.005. Rates of successful IOP lowering without medications for phaco versus PCP at 12 months were 34% versus 75%, respectively (P=0.003). Conclusions:A combination of canaloplasty with phaco results in a decreased number of glaucoma medications and increased survival rate of IOP-lowering effect compared with phaco alone.

HRT III glaucoma probability score and Moorfields regression across the glaucoma spectrum.

ObjectiveTo compare the agreement, sensitivity, and specificity of the Heidelberg Retina Tomograph III Glaucoma Probability Score (GPS) and Moorfields Regression Analysis (MRA) across the spectrum of glaucomatous visual field (VF) loss. DesignRetrospective observational study. MethodsData from 247 glaucoma patients and 142 controls who underwent standard achromatic perimetry (SITA-SAP) and Heidelberg Retina Tomograph III imaging within 6 months were analyzed. Sensitivity, specificity, agreement, and discrimination capability of MRA and GPS were assessed. ResultsAge-adjusted specificity was 92% and 93% and sensitivity was 76.88 and 80.85 for GPS and MRA, respectively. Sensitivity for early VF loss [mean deviation (MD) <−5 dB] (N=81) was 66.64% and 69.82%, for moderate VF loss (−5 dB −15 dB) (N=62) was 87.70% and 86.48% (GPS and MRA, respectively). Age-specific receiver operating characteristics ranged from 0.89 to 0.92 and from 0.87 to 0.90 (GPS and MRA, respectively). Kappa ranged from 0.64 to 0.77. ConclusionsSpecificity for MRA and GPS was similar and agreement was good. GPS offered slightly higher age-specific receiver operating characteristic. GPS, which does not require contour line placement, may have a potential role in screening for severe glaucomatous damage.