Michael S. Kook

Macular and Peripapillary Retinal Nerve Fiber Layer Measurements by Spectral Domain Optical Coherence Tomography in Normal-Tension Glaucoma

PURPOSE To evaluate and compare the glaucoma discrimination ability of macular inner retinal layer (MIRL) thickness with that of peripapillary retinal nerve fiber layer (pRNFL) thickness measured by spectral-domain optical coherence tomography (RTVue-100; Optovue Inc, Fremont, CA) in patients with normal-tension glaucoma (NTG). METHODS Sixty-five healthy subjects and 102 with NTG were enrolled. MIRL thickness provided by a ganglion cell complex (GCC) scan and two RNFL thicknesses measured by the NHM4 (RNFL1) and RNFL 3.45 (RNFL2) modes of the RTVue-100 system were analyzed. The areas under the receiver operating characteristic curves (AUCs) of MIRL and pRNFL thicknesses for discriminating patients with NTG from control subjects were determined. The AUCs were compared between patients with central visual field (VF) defects (VF; <or=10 degrees of fixation) and peripheral VF defects (>10 degrees from fixation). RESULTS The average MIRL thickness showed a strong correlation with both RNFL1 and -2 thicknesses (R(2) = 0.773, 0.774, both P < 0.0001). The AUCs for average MIRL, RNFL1, and RNFL2 thicknesses were not significantly different at 0.945, 0.973, and 0.976, respectively. However, the AUCs of the average and superior MIRL thicknesses were significantly less than that of the pRNFL thickness in eyes with moderate-to-advanced glaucoma and eyes with peripheral VF defects. CONCLUSIONS The average MIRL thickness showed a strong correlation with pRNFL thickness, because patients with NTG at an early stage showed paracentral VF defects near the fixation point. MIRL thickness showed glaucoma discrimination ability comparable to that of pRNFL thickness in patients with NTG with early VF defects. In eyes with advanced or peripheral VF defect, pRNFL measurement showed a better glaucoma diagnostic ability than did MIRL measurement.

Comparison of Retinal Nerve Fiber Layer Thickness Measured by Cirrus HD and Stratus Optical Coherence Tomography

PURPOSE To study the relationship between retinal nerve fiber layer (RNFL) thickness measured by time domain (Stratus) and spectral domain (Cirrus HD) optical coherence tomography (OCT). DESIGN Cross-sectional study. PARTICIPANTS Sixty healthy participants, 48 glaucoma suspects, and 55 subjects with glaucoma. METHODS Participants were imaged by a single trained operator using the Stratus OCT (fast RNFL scan mode) and Cirrus HD-OCT (optic disc cube mode) at the same visit. MAIN OUTCOME MEASURES The RNFL thickness as measured by the Stratus OCT (fast RNFL scan mode) and Cirrus HD-OCT (optic disc cube mode) was compared (paired t test). The relationship between RNFL thickness measurements of the 2 OCTs were evaluated using a Pearson correlation analysis. The presence of abnormal classification, as determined by using an internal normative data base in each machine was compared (chi-square test). The sensitivity and specificity of normative classification of 2 OCT measurements were calculated. RESULTS Average RNFL thickness as determined by the 2 OCT machines was correlated (r = 0.94; P<0.001), but was significantly different with the 2 machines (Stratus, 98.0 mum, standard deviation [SD] 18.0; Cirrus, 85.6 mum, SD 14.6; P<0.001). The Cirrus HD-OCT classified a significantly higher percentage of eyes as abnormal (Stratus, 12.9%; Cirrus, 23.3%; P<0.001) in average RNFL thickness. Cirrus OCT demonstrated higher sensitivity and specificity (63.6% and 100%) than Stratus OCT (40.0% and 96.7%) in normative classification of average RNFL thickness. CONCLUSIONS There were significant differences in RNFL thickness and normative classification as determined by Stratus OCT and Cirrus HD-OCT despite an excellent correlation of RNFL thickness measurement. Overall sensitivity and specificity were higher with Cirrus OCT. These findings are particularly relevant when an individual undergoes longitudinal follow-up with different OCTs.

Twenty-four hour ocular perfusion pressure fluctuation and risk of normal-tension glaucoma progression.

PURPOSE To investigate the relationship between clinical factors including 24-hour mean ocular perfusion pressure (MOPP, (2/3) x mean arterial pressure [MAP] - intraocular pressure [IOP]) and visual field (VF) progression in eyes with medically treated normal-tension glaucoma (NTG). METHODS One hundred one eyes of 101 NTG patients followed up for more than 4 years (mean follow-up, 6.2 years +/- 12.1 months) were included after retrospective chart review. Several clinical factors including demographic, systemic, ocular risk factors, and 24-hour MOPP were explored for associations with decreasing VF. Kaplan-Meier analyses were performed to compare outcomes with reference to four risk factors (age, myopia, and elevated MAP and MOPP fluctuation) for VF deterioration. Hazard ratios (HRs) for the association between potential risk factors and glaucoma progression were obtained using Cox proportional hazards models. RESULTS Overall VF progression was detected in 29 (28.7%) eyes. There were significant differences between progressors and nonprogressors in nocturnal MAP and MOPP fluctuations (both P < 0.0001), 24-hour MAP, and MOPP fluctuations (both P < 0.0001), initial mean deviation (P = 0.0034), and pattern standard deviation (PSD) score (P < 0.0001). Both elevated 24-hour MAP and MOPP fluctuations were associated with greater VF progression probabilities based on Kaplan-Meier analyses. Among all risk factors investigated, the Cox proportional hazards model indicated that VF progression was significantly associated with 24-hour MOPP fluctuation and initial PSD score. CONCLUSIONS Clinical factors other than IOP were associated with VF progression in our series of medically treated NTG eyes. Twenty-four-hour MOPP fluctuation was the most consistent prognostic factor for glaucoma progression.

Relationship between Visual Field Sensitivity and Macular Ganglion Cell Complex Thickness as Measured by Spectral-Domain Optical Coherence Tomography

PURPOSE To evaluate the strength and pattern of the relationship between visual field (VF) mean sensitivity (MS), assessed by standard automated perimetry (SAP), and macular ganglion cell complex thickness (GCCT), measured with spectral-domain optical coherence tomography (SD-OCT). METHODS Ninety-seven glaucoma patients were enrolled. GCCT, determined by ganglion cell complex (GCC) scanning, and two peripapillary retinal nerve fiber layer thickness (pRNFLT) measurements, using the NHM4 (RNFL1) and RNFL 3.45 (RNFL2) modes, were recorded. MS was recorded on the decibel (dB) and 1/L scales. The relationship between function (MS) and structure (GCC, pRNFLT) was sought. RESULTS The association of MS (in decibels) with GCC global (r = 0.445) and sectoral (superior, r = 0.528; inferior, r = 0.370) thicknesses was not significantly different from that of MS to global (RNFL1, r = 0.505; RNFL2, r = 0.498) and sectoral (RNFL 1 superior, r = 0.559; inferior, r = 0.440; RNFL 2 superior, r = 0.535; inferior, r = 0.443) pRNFLT, on linear regression analysis. The relationship pattern was curvilinear on the dB scale against GCCT and RNFLT. Logarithmic regression of MS (using both the dB and 1/L scales) against GCCT and RNFLT was better than linear regression in describing the pattern of association. CONCLUSIONS GCCT, determined by SD-OCT, showed correlation to MS of a strength similar to that demonstrated between MS and pRNFLT.

Imaging of the retinal nerve fibre layer with spectral domain optical coherence tomography for glaucoma diagnosis

Optical coherence tomography (OCT) techniques have been applied to develop a new generation of the technology, called spectral domain (SD) or Fourier domain (FD) OCT. The commercially available SD-OCT technology offers benefits over the conventional time domain (TD) OCT such as a scanning speed up to 200 times faster and higher axial resolution (3 to 6 μm). Overall, SD-OCT offers improved performance in terms of reproducibility. SD-OCT has a level of discriminating capability, between healthy and perimetric glaucoma eyes similar to that obtained with TD-OCT. Furthermore, the capabilities and features of SD-OCT are rapidly evolving, mainly due to three-dimensional imaging and image rendering. More sophisticated approaches for macular and optic disc assessment are expected to be employed in clinical practice. Analysis software should be further refined for interpretation of SD-OCT images in order to enhance the sensitivity and specificity of glaucoma diagnostics. Most importantly for SD-OCT is determination of its ability to diagnostic structural glaucomatous progression. Considering the recent launch time of the commercially available SD-OCT and slow progressing characteristic of glaucoma, we must wait for longitudinal SD-OCT data, with a long enough follow-up, to become available.

Short-term effect of mitomycin-C augmented trabeculectomy on axial length and corneal astigmatism

Purpose: To evaluate the short‐term effect of trabeculectomy with adjunctive mitomycin‐C (MMC) on corneal astigmatism and axial length. Setting: Asan Medical Center, University of Ulsan, Department of Ophthalmology, Seoul, Korea. Methods: Eighteen consecutive eyes of 16 patients having trabeculectomy with adjunctive MMC were prospectively analyzed. Intraocular pressure (IOP) and axial length were evaluated preoperatively and 1, 3, 6, and 12 months postoperatively. Postoperative changes in corneal astigmatism were evaluated using vector analysis. Results: The overall mean induced astigmatism showed with‐the‐rule change up to 3 months postoperatively followed by an against‐the‐rule shift. The mean axial length was significantly less postoperatively and changed throughout the 12 month follow‐up. There was a positive correlation between postoperative axial length and IOP. Eyes with higher preoperative IOP had a greater decrease in axial length after trabeculectomy with MMC. Conclusion: The induced corneal astigmatism after trabeculectomy with MMC was long lasting, although less than that in previous studies. The change in axial length after surgery was significant, especially in eyes with a high preoperative IOP. The decrease in axial length persisted throughout the follow‐up.

Characteristics of visual field progression in medically treated normal-tension glaucoma patients with unstable ocular perfusion pressure.

PURPOSE To investigate the characteristics of visual field (VF) progression in medically treated normal-tension glaucoma (NTG) patients (Koreans) with unstable ocular perfusion pressure (OPP). METHODS One hundred one eyes of 101 NTG patients followed up for more than 4 years (mean follow-up, 6.2 years ± 12.1 months) were included. Modified Anderson criteria (MC) and linear regression analysis (LA) of VF mean deviation (MD) within the central 10° and 10° to 24° area were assessed for determining VF progression in groups with lowest (LMF) and highest (HMF) 24-hour mean OPP [MOPP = 2/3;(mean arterial pressure - IOP)] fluctuation. Kaplan-Meier analyses were used to compare the elapsed time of confirmed VF progression in the two groups. Hazard ratios (HRs) for the association between clinical risk factors including 24-hour MOPP and central VF progression were obtained by using Cox proportional hazards models. RESULTS Three of 33 eyes in the LMF progressed, whereas 12 of 34 eyes in the HMF progressed within the central 10° according to the MC; the between-group difference was significant (P = 0.010). By LA within the central 10°, two eyes from the LMF and nine from the HMF groups showed progression (P = 0.025). The HMF showed a greater cumulative probability of central VF progression than the LMF, by both LA and MC (Kaplan-Meier analysis, P = 0.003, 0.015, log-rank test). In multivariate analysis, only 24-hour MOPP fluctuation was significantly associated with central VF progression (P = 0.014). CONCLUSIONS The 24-hour MOPP fluctuation was the most consistent prognostic factor among various IOP, blood pressure, and clinical factors for central VF glaucomatous progression in our series of NTG eyes.

Characteristics and reproducibility of anterior chamber angle assessment by anterior-segment optical coherence tomography.

Purpose:  To evaluate the basic characteristics and reproducibility of anterior chamber angle (ACA) measurements determined by anterior‐segment optical coherence tomography (AS‐OCT) in open‐angle and primary angle closure suspect (PACS) patients.

Study of retinal nerve fibre layer thickness in eyes with high tension glaucoma and hemifield defect

AIM To quantitatively evaluate retinal nerve fibre layer (RNFL) difference in areas of apparently normal appearing visual field in eyes with high tension glaucoma (HTG) and hemifield defects using scanning laser polarimetry. METHODS 40 eyes from 40 patients with HTG with superior or inferior hemifield defects based on the Humphrey field analyser (HFA) underwent RNFL thickness measurements. 20 normal eyes from 20 subjects matched in age and refractive error were selected as a control group. The RNFL thickness was measured with a scanning laser polarimeter. Mean RNFL thickness was evaluated in four quadrants (superior, inferior, nasal, and temporal). A superior or inferior quadrant in the defined ring of scanning laser polarimetry corresponds to inferior or superior hemifield in HFA. RESULTS The mean RNFL thickness in the unaffected quadrant (the quadrant corresponding to the hemifield with apparently normal visual field based on HFA) of the HTG group was significantly thinner than the average RNFL thickness of the corresponding quadrant of the control eyes. The RNFL thickness of the unaffected quadrant in the eyes with HTG was reduced and statistically similar to that of the affected quadrant. Symmetry, calculated as the ratio of superior to inferior RNFL thickness, showed no statistical difference between the study and control group. CONCLUSION Changes in RNFL are present in the apparently normal hemifield in the eyes with HTG. The thickness of the RNFL is reduced symmetrically in both superior and inferior quadrants based on the GDx parameters.

Detection of glaucoma by spectral domain-scanning laser ophthalmoscopy/optical coherence tomography (SD-SLO/OCT) and time domain optical coherence tomography.

PurposeTo evaluate the relationship between time-domain and spectral domain-scanning laser ophthalmoscopy/optical coherence tomography (SD-SLO/OCT), and to compare the ability of these methods to detect glaucoma. MethodsForty-nine glaucoma and 43 healthy participants were imaged by SD-SLO/OCT and Stratus OCT. Bland-Altman plots were used to compare the measurements of retinal nerve fiber layer (RNFL) thickness. Areas under the receiver operating characteristics curves (AUCs), including the average thickness, thickness in each of the 4 quadrants, and thickness at each of the 12 clock-hours were compared. Sensitivity and specificity of normative classification of the 2 OCTs for detection of glaucoma were calculated. ResultsThe Bland-Altman plot showed good agreement between the 2 instruments. In eyes with glaucoma, RNFL thickness was greater when measured by SD-SLO/OCT than Stratus OCT in most sectors of the eye (Average RNFL thickness: SD-SLO/OCT, 82.7±15.3 &mgr;m; Stratus OCT, 76.9±18.4 &mgr;m; P<0.001). However, the differences between 2 OCTs were not significant in healthy participants. The AUCs of average RNFL measurements for discrimination of glaucoma did not differ significantly between the instruments (SD-SLO/OCT, 0.969; Stratus OCT, 0.959; P=0.535). SD-SLO/OCT showed similar sensitivity (57.1%) with Stratus OCT (53.4%) for detection of glaucoma in normative classification of average RNFL thickness. ConclusionsBoth OCT technologies did well in the diagnosis of glaucoma. Although there were small differences in the 2 instruments in measured RNFL thickness of glaucomatous eyes, in general there was good agreement between the 2 OCTs. SD-SLO/OCT classified more glaucomatous eyes as abnormal based on its normative database.