Chandra S. Garudadri

Predictors of normal optic nerve head, retinal nerve fiber layer, and macular parameters measured by spectral domain optical coherence tomography.

PURPOSE To evaluate the effects of signal strength, age, sex, optic disc size, and axial length on the normal optic nerve head (ONH), retinal nerve fiber layer (RNFL), and macular measurements with spectral domain optical coherence tomography (SD-OCT). METHODS In an observational, cross-sectional study, 119 eyes of 60 normal subjects of Indian origin underwent ONH, RNFL, and macular imaging with SD-OCT during the same visit. Linear mixed-modeling methods were used to evaluate the effects of signal strength, age, sex, optic disc area, and axial length on ONH, RNFL, and macular measurements. RESULTS ONH rim measurements increased and cup measurements decreased with increasing signal strengths. For a 10-unit increase in signal strength, total rim area increased by a mean of 0.1 mm(2). ONH measurements also increased with increasing optic disc size. Rim measurements decreased and cup measurements increased with increasing axial length. None of the predictors influenced RNFL measurements. Macular inner retinal thickness decreased by a mean of 1.7 μm and macular full retinal thickness decreased by an average of 3.4 μm for every decades increase in age. Sex did not influence any of the measurements. CONCLUSIONS Signal strength, optic disc size, and axial length had a significant effect on ONH measurements, whereas age had a significant effect on macular measurements. None of the predictors evaluated influenced the RNFL measurements. These predictors should be considered when evaluating change in the structural measurements in glaucoma over time.

An ultrasound biomicroscopic study of the anterior segment in Indian eyes with primary angle-closure glaucoma.

PurposeTo evaluate the presence of plateau iris in eyes with primary angle-closure glaucoma (PACG) after laser peripheral iridotomy by gonioscopy and ultrasound biomicroscopy and to evaluate the pathogenesis of this condition by comparing the UBM parameters of these eyes with those in normal subjects. Patients and MethodsThis prospective study was carried out in the Glaucoma clinic of a tertiary eye care center. A detailed clinical examination including applanation tonometry, indentation gonioscopy with a Sussman four-mirror gonioscope, and ultrasound biomicroscopic examination in one randomly selected eye of 55 patients (55 eyes) with PACG who had undergone laser peripheral iridotomy and 22 normal subjects (22 eyes). ResultsAmong the PACG eyes, 40% (22/55) had an open angle (angle opening distance > 130 microns) and 60% (33/55) eyes had a narrow angle (angle opening distance ≤ 130 microns). A large anteriorly placed ciliary process with a narrow ciliary sulcus was found in 9 of the 22 eyes with open angle (40.9%), and 22 of the 33 eyes with narrow angles (66.66%). Trabecular ciliary process distance was significantly larger in the eyes with open angles compared with those with narrow angles (P = 0.001). ConclusionsPlateau iris was common in the clinic population studied. Anteriorly directed ciliary processes were seen both in eyes with plateau iris as well as in eyes with PACG that had deep anterior chambers after iridotomy.

Effect of Spectrum Bias on the Diagnostic Accuracy of Spectral-Domain Optical Coherence Tomography in Glaucoma

PURPOSE To evaluate the influence of a control group on the diagnostic accuracy of spectral-domain optical coherence tomography (SD-OCT) in early glaucoma. METHODS In a diagnostic, case-control study, 119 eyes of 60 normal subjects with no findings suspicious for glaucoma (control cohort 1); 76 eyes of 41 subjects referred by general ophthalmologists as glaucoma suspects based on optic disc morphology, but found by glaucoma experts to be normal but with physiological variations in their optic nerves (control cohort 2); and 65 eyes of 46 early-glaucoma patients (cases) underwent imaging of the optic nerve head (ONH), retinal nerve fiber layer (RNFL), and ganglion cell complex (GCC) by SD-OCT. RESULTS Areas under the receiver operating characteristic curves (AUC) of ONH parameters discriminating glaucomatous eyes from normal eyes of control cohort 2 were significantly lesser (P < 0.001) than those discriminating glaucomatous eyes from normal eyes of control cohort 1. AUCs of RNFL parameters discriminating glaucomatous eyes from normal eyes of control cohorts 2 and 1 were comparable. Although the AUCs of GCC thickness parameters were comparable, AUCs of GCC focal and global loss volume in control cohort 2 (0.684 and 0.671. respectively) were significantly less (P < 0.05) than in control cohort 1 (0.881 and 0.841, respectively). CONCLUSIONS The effectiveness of most SD-OCT parameters in detecting glaucoma significantly decreased when evaluated against a clinically relevant control group with suspicious-looking optic nerves compared with that against a control group consisting of normal subjects with no findings suspicious for glaucoma.

Ability of different scanning protocols of spectral domain optical coherence tomography to diagnose preperimetric glaucoma.

PURPOSE To evaluate the ability of the optic nerve head (ONH), retinal nerve fiber layer (RNFL), and ganglion cell complex (GCC) parameters of spectral domain optical coherence tomograph (SDOCT) in detecting preperimetric glaucoma. METHODS In a cross-sectional study, 34 preperimetric glaucoma eyes (34 patients) and 72 control eyes (72 subjects) with large physiologic optic disc cupping underwent ONH, RNFL, and GCC imaging with SDOCT. Preperimetric glaucoma was diagnosed in the presence of glaucomatous optic neuropathy on masked evaluation of optic disc photographs by two glaucoma experts and normal visual fields. The ability of SDOCT parameters to discriminate preperimetric glaucoma eyes from eyes with large physiologic cups was evaluated by areas under the receiver operating characteristic curves (AUC), sensitivities at fixed specificities, and likelihood ratios (LR). RESULTS All SDOCT parameters were significantly different (P < 0.05) between the two groups. The ONH, RNFL, and GCC parameters with best AUCs to differentiate preperimetric glaucoma from eyes with large physiologic cups were vertical cup to disc ratio (0.76), inferior quadrant RNFL thickness (0.76), and inferior quadrant GCC thickness (0.75), respectively. Sensitivities at 95% specificity of SDOCT parameters ranged between 15% and 29%. Likelihood ratios of outside normal limits category of parameters ranged between 3 and 11, and within normal limits category between 0.5 and 0.8. CONCLUSIONS Diagnostic abilities of ONH, RNFL, and GCC parameters of SDOCT to differentiate preperimetric glaucoma eyes from control eyes with large physiologic cupping were only moderate.

Relationship between Severity of Visual Field Loss at Presentation and Rate of Visual Field Progression in Glaucoma

PURPOSE To evaluate the relationship between severity of visual field (VF) loss at presentation and rate of VF progression in glaucoma. DESIGN Clinic-based, retrospective study. PARTICIPANTS We included 512 eyes of 310 primary glaucoma patients. METHODS We analyzed the VFs of all subjects of primary glaucoma who had >5 VFs between 1989 and 2008. Based on the mean deviation (MD), we classified the VF loss as mild (MD > -6 dB), moderate (MD ≤ -6 to ≥ -12 dB) or severe (MD < -12 dB). Guided Progression Analysis software which gives the rate of progression (ROP) of Visual Field Index per year was used to assess the ROP. MAIN OUTCOME MEASURES Relationship between severity of VF loss at presentation and ROP. RESULTS The median duration of follow-up was 6.8 years. The ROP increased (worsened) by 0.02% per year for every dB worsening of MD (P = 0.02) and for every year of increasing age (P = 0.001). Association between MD and ROP showed a significant positive relationship in mild (β = 0.18; P = 0.001) and a significant negative relationship in severe (β = -0.16; P<0.001) VF loss category. Association between MD and ROP was not significant in the moderate VF loss category (β = -0.05; P = 0.61). CONCLUSIONS In early stages of glaucoma, the ROP worsened as the severity increased, but, in later stages of the disease, ROP became smaller as the severity increased. There is a need for better methods to detect progression in eyes with severe glaucomatous damage.

Comparison of outcomes of trabeculectomy with mitomycin C vs. ologen implant in primary glaucoma

Purpose: To compare the safety and efficacy of trabeculectomy with Ologen implant vs. trabeculectomy with Mitomycin C (MMC). Materials and Methods: In a prospective, randomized, pilot study, 39 eyes of 33 subjects with medically uncontrolled primary glaucoma, aged 18 years or above underwent trabeculectomy either with MMC (20 eyes) or with Ologen implant (19 eyes). The primary outcome measure was cumulative success probability, defined as complete if the intraocular pressure (IOP) was > 5 and ≤ 21 mm Hg without anti-glaucoma medications or additional surgery and qualified if an IOP was > 5 and ≤ 21 mm Hg with or without anti-glaucoma medications. Results: Mean (± standard deviation) follow-up in Ologen group was 19.1 ± 8.1 months, and in MMC group was 18.0 ± 8.4 months. Mean IOP reduction at 6 months was significantly lower (P = 0.01) in the MMC group (11.9 ± 2.9 mm Hg) as compared to Ologen group (14.6 ± 2.7 mm Hg). However, at 12 months (P = 0.81) and 24 months (P = 0.32), the mean IOP was similar between the 2 groups. Complete success probability at the end of 6 months in Ologen group was 100% (95% confidence interval: 59.1 - 99.0) was similar (P = 0.53) to that in MMC group (93.8%, 95% CI: 63.2 - 99.1). The incidences of early post-operative complications were similar in the 2 groups, except hyphema, which was significantly more in Ologen group (P = 0.02). Conclusion: In this pilot study, the success of trabeculectomy and complications were similar in both Ologen and MMC groups at the end of 6 months.

Evaluation of central corneal thickness measurement with RTVue spectral domain optical coherence tomography in normal subjects.

Purpose: To determine (1) repeatability of central corneal thickness (CCT) measurements by spectral domain optical coherence tomography (RTVue; Optovue, Inc, Fremont, CA) and (2) agreement between CCT measurements by RTVue and those by ultrasonic pachymetry, Orbscan, and anterior segment optical coherence tomography (ASOCT). Methods: In a prospective observational study, 2 cohorts of normal subjects were recruited. In the first cohort (51 subjects), 5 measurements of CCT were obtained by RTVue during the same visit to determine the repeatability. In the second cohort (65 subjects), CCT measurements were obtained by RTVue, ultrasonic pachymetry, Orbscan, and ASOCT during the same visit to determine the agreement among these instruments. Repeatability was assessed by intraclass correlation coefficient (ICC), within-subject standard deviation, coefficient of repeatability, and within-subject coefficient of variation. Agreement was assessed by ICC and Bland and Altman plots. Results: Repeatability of CCT measurements by RTVue as assessed by ICC, within-subject standard deviation, coefficient of repeatability, and within-subject coefficient of variation was 0.99 (0.99-0.99), 2.2 (1.9-2.5), 4.2 μm (3.6-4.8), and 0.4% (0.3-0.5), respectively. The average CCT by RTVue (529 μm) was comparable to that by ultrasonic pachymetry (539 μm; P = 0.15), Orbscan (536 μm; P = 0.54), and ASOCT (526 μm; P = 0.77). The 95% limits of agreement on Bland and Altman plots ranged from 20 μm (between RTVue and ASOCT) to 33 μm (between RTVue and Orbscan). Conclusions: CCT measurements by RTVue have an excellent repeatability. Although CCT measurements by RTVue are comparable to that by ultrasonic pachymetry, Orbscan, and ASOCT, the difference between instruments can be significant depending on the clinical situation considered.

Treatment outcomes in malignant glaucoma.

PURPOSE To report treatment outcomes in malignant glaucoma. DESIGN Retrospective case series. PARTICIPANTS Twenty-eight eyes of 26 patients who were treated for malignant glaucoma between 1991 and 2009. METHODS Malignant glaucoma was diagnosed based on the presence of a shallow or flat central and peripheral anterior chamber in the presence of patent iridotomy, with intraocular pressure (IOP) of 22 mmHg or more after any intraocular surgery. The treatment algorithm included antiglaucoma medications and cycloplegics as first-line methods; the second-line therapy in pseudophakic eyes was laser hyaloidotomy, followed by vitrectomy-hyaloidotomy-iridectomy (VHI) or transscleral cyclophotocoagulation (TSCPC). MAIN OUTCOME MEASURES Resolution was defined as deepening of the central anterior chamber and IOP of 21 mmHg or less (on 2 successive follow-ups at least 1 week apart) with or without topical antiglaucoma medications in the absence of systemic antiglaucoma medications. RESULTS At the diagnosis of malignant glaucoma, 5 eyes were phakic and 23 were pseudophakic. The preceding surgeries were trabeculectomy (11 eyes), cataract surgery (10 eyes), and combined cataract and glaucoma surgery (7 eyes). Mean IOP decreased from 34 ± 8.3 mmHg at presentation to 14.3 ± 5.2 mmHg at the last visit (P<0.001). Resolution of malignant glaucoma was seen in 27 eyes (27/28; 96%), 17 eyes resolved with 1 intervention, and 10 eyes required repeat procedures. Of the 27 eyes whose disease resolved, this result was achieved in 4 eyes with medical treatment, in 7 pseudophakic eyes with laser hyaloidotomy, in 4 eyes with VHI, and in 12 eyes with TSCPC. The median duration of follow-up was 192 days (interquartile range, 35-425 days). There was no difference in the visual acuity at presentation and at the final visit in 14 eyes. Eight eyes gained 2 lines or more and 6 eyes lost 2 lines or more of visual acuity. CONCLUSIONS Malignant glaucoma can be managed successfully by appropriate and timely interventions. Medical treatment was beneficial in phakic eyes, laser hyaloidotomy was beneficial in pseudophakic eyes, and vitrectomy and TSCPC were beneficial in refractory cases. A stepladder approach to treatment was successful (96%) in this series. FINANCIAL DISCLOSURE(S) The author(s) have no proprietary or commercial interest in any materials discussed in this article.

Effect of cataract extraction on Visual Field Index in glaucoma.

Purpose:To determine the effect of cataract on the Visual Field Index (VFI) in glaucoma patients. Methods:Reliable visual fields (VFs) of 53 patients (53 eyes) with primary glaucoma who underwent phacoemulsification either alone or combined with trabeculectomy were analyzed before and after surgery. All patients had VFs within a period of 15 months before and after surgery. VFI, mean deviation (MD), and pattern standard deviation (PSD) before surgery were compared with those after surgery. Results:Median (25th and 75th percentiles) MD after cataract surgery [−10.52 dB (range, −19.25 to −4.86 dB)] was significantly better (P=0.003) than that before surgery [−11.74 dB (range, −20.61 to −7.15 dB)]. Median PSD after surgery [4.76 dB (range, 2.48 to 9.83)] was worse (P=0.01) than that before surgery [3.50 dB (range, 1.93 to 8.20 dB)] when eyes with MD better than −20 dB were considered (41 eyes). VFI after surgery [80% (range, 44% to 94%)] was similar (P=0.92) to that before surgery [77% (range, 37% to 92%)]. MD improved while VFI remained unchanged in both nuclear sclerotic (n=41) and posterior subcapsular cataracts (n=12). Conclusions:MD and PSD were significantly affected, whereas VFI was not affected by cataract. VFI may be a more robust measure of VF damage than MD or PSD in glaucomatous eyes with coexisting cataracts.

Behavior of Visual Field Index in Advanced Glaucoma

PURPOSE To evaluate the magnitude of Visual Field Index (VFI) change attributable to change in the estimation algorithm from the pattern deviation probability plot (PDPP) to the total deviation probability plot (TDPP) when the mean deviation (MD) crosses -20 decibels (dB). METHODS In a retrospective study, 37 stable glaucoma eyes in which MD of the VFs crossed -20 dB were identified. For each eye, a pair of VFs was selected so that one VF of the pair had a MD better than but close to -20 dB and the other had a MD worse than but again close to -20 dB. The change in VFI in the VF pairs and its associations with the number of points in probability plots with normal threshold sensitivities were evaluated. Similar pairs of VFs from 28 stable glaucoma eyes where the MD crossed -10 dB were chosen as controls. RESULTS The change in VFI in VF pairs when the MD crossed 20 dB ranged from 3% to 33% (median: 15%), while the change when MD crossed -10 dB ranged from 1% to 8% (median: 4%). Difference in the number of points with normal threshold sensitivities in PDPP when MD was better than -20 dB compared to those in TDPP when MD crossed -20 dB significantly influenced the VFI change (R(2) = 0.65). Considering the eccentricity of these points further explained the VFI change (R(2) = 0.81). CONCLUSIONS The decrease in VFI when MD crosses -20 dB can be highly variable. This has to be considered with the use of VFI in clinical and research settings.