Comparison of Fundus Biomicroscopy Examination of the Optic Nerve Head with and without Mydriasis.

BACKGROUND: Notwithstanding the significant advances in automated imaging techniques in the past 2 decades, subjective evaluation of the optic disc still remains an important part of glaucoma propaedeutic. In places with limited resources and a high demand for ophthalmic care, anatomical evaluation of glaucoma cases often relies solely on slit-lamp-based fundus biomicroscopic examination, which is frequently performed without mydriasis. OBJECTIVE: The aim of this study was to compare metrics related to fundus biomicroscopy examination of the optic nerve head and peripapillary retinal nerve fiber layer (pRNFL) with and without mydriasis. MATERIAL AND METHODS: Healthy individuals, patients with early glaucoma, and glaucoma suspects were prospectively enrolled. Patients were examined before and after mydriasis by three glaucoma specialists, who estimated patients' vertical cup-to-disc ratio (CDR) and evaluated the presence of glaucomatous signs: laminar dot sign, disc hemorrhage, disc saucering, disc notching, peripapillary atrophy, localized pRNFL defect, and loss of the ISNT pattern. Main outcome measures were the intra-observer comparison, the inter-observer agreement, and the abilities to identify glaucomatous signs before and after mydriasis. RESULTS: Thirty patients (60 eyes) were enrolled (mean age, 62.3 ± 11.6 years). Considering the evaluation of the three examiners, the mean vertical CDR increased from 0.41 to 0.44 (p = 0.02), and the median of the coefficient of variation of the measures was reduced from 0.24 to 0.11 (p = 0.01) after mydriasis. Regarding the inter-observer agreement evaluation, the kappa coefficient values ranged from 0.64 to 0.72 before mydriasis and from 0.71 to 0.77 after mydriasis. Dot sign and disc notching were better identified through fundoscopic examination with mydriasis compared to the nonmydriatic examination (p < 0.01). CONCLUSION: Our results suggest that fundus biomicroscopy should be performed with mydriasis whenever possible, as it yells a better intra- and inter-observer agreement and improves the detection of glaucomatous signs. Moreover, examiners seem to underestimate CDR values without mydriasis. Further investigation is warranted to validate these findings by general ophthalmologists and in different populations.

Diagnosing preperimetric glaucoma with spectral domain optical coherence tomography.

PURPOSE: To evaluate the diagnostic accuracy of spectral domain optical coherence tomography (SD-OCT) for detection of preperimetric glaucoma and compare it with the performance of confocal scanning laser ophthalmoscopy (CSLO). DESIGN: Cohort study. PARTICIPANTS: A cohort of 134 eyes of 88 glaucoma suspects based on the appearance of the optic disc. METHODS: Patients were recruited from the Diagnostic Innovations in Glaucoma Study (DIGS). All eyes underwent retinal nerve fiber layer (RNFL) imaging with Spectralis SD-OCT (Heidelberg Engineering, Carlsbad, CA) and topographic imaging with Heidelberg Retinal Tomograph III (HRT-III) (Heidelberg Engineering) CSLO within 6 months of each other. All patients had normal visual fields at the time of imaging and were classified on the basis of history of documented stereophotographic evidence of progressive glaucomatous change in the appearance of the optic nerve occurring before the imaging sessions. MAIN OUTCOME MEASURES: Areas under the receiver operating characteristic curves (AUCs) were calculated to summarize diagnostic accuracies of the SD-OCT and CSLO. Likelihood ratios (LRs) were reported using the diagnostic categorization provided by each instrument after comparison to its normative database. RESULTS: Forty-eight eyes of 42 patients had evidence of progressive glaucomatous change and were included in the preperimetric glaucoma group. Eighty-six eyes of 46 patients without any evidence of progressive glaucomatous change followed untreated for an average of 14.0 ± 3.6 years were included in the control group. The parameter with the largest AUC obtained with the SD-OCT was the temporal superior RNFL thickness (0.88 ± 0.03), followed by global RNFL thickness (0.86 ± 0.03) and temporal inferior RNFL thickness (0.81 ± 0.04). The parameter with the largest AUC obtained with the CSLO was rim area (0.72 ± 0.05), followed by rim volume (0.71 ± 0.05) and linear cup-to-disk ratio (0.66 ± 0.05). Temporal superior RNFL average thickness measured by SD-OCT performed significantly better than rim area measurements from CSLO (0.88 vs. 0.72; P=0.008). Outside normal limits results for SD-OCT parameters were associated with strongly positive LRs. CONCLUSIONS: The RNFL assessment with SD-OCT performed well in detecting preperimetric glaucomatous damage in a cohort of glaucoma suspects and had a better performance than CSLO.

Comparison of the diagnostic accuracies of the Spectralis, Cirrus, and RTVue optical coherence tomography devices in glaucoma.

PURPOSE: To compare the diagnostic accuracies of retinal nerve fiber layer (RNFL) thickness measurements obtained with the Spectralis (Heidelberg Engineering, Dossenheim, Germany), Cirrus (Carl Zeiss Meditec, Dublin, CA), and RTVue (Optovue Inc., Fremont, CA) devices for the detection of glaucoma. DESIGN: Diagnostic, case-control study. PARTICIPANTS: A total of 233 (107 healthy, 126 glaucomatous) of 149 participants from the longitudinal Diagnostic Innovations in Glaucoma Study (DIGS) and from the African Descent and Glaucoma Evaluation Study (ADAGES). METHODS: All participants underwent RNFL thickness imaging with the Spectralis, Cirrus, and RTVue devices in the same visit. Receiver operating characteristic (ROC) curves adjusted for age and race were obtained for quadrants (superior, nasal, inferior, temporal) and global RNFL thickness for all instruments. Areas under ROC (AUC) and sensitivities at fixed specificities (80% and 95%) were calculated and compared. MAIN OUTCOME MEASURES: Comparison of diagnostic accuracy using AUCs and sensitivities at fixed specificities of 80% and 95%. RESULTS: The RNFL thickness parameter with the largest AUCs was the superior quadrant for the Spectralis (0.88) and the global RNFL thickness for the Cirrus (0.88) and the RTVue (0.87). The pairwise comparison among the ROC curves showed no statistical difference for all parameters except for the nasal quadrant, which had significantly larger AUC in the Spectralis and RTVue compared with the Cirrus (P<0.03 for both comparisons). There were no significant differences in sensitivities among the best parameters from each instrument (P>0.05). The superior quadrant thickness measured with the Spectralis had sensitivity of 81.9% at a fixed specificity of 80% and 70% at a fixed specificity of 95%. The global thickness measured by the Cirrus had a sensitivity of 80.3% at a fixed specificity of 80% and 65.6% at a fixed specificity of 95%. For the RTVue, the global thickness had a sensitivity of 77.9% at a fixed specificity of 80% and 62.1% at a fixed specificity of 95%. CONCLUSIONS: Although the spectral-domain optic coherence tomography (SD-OCT) instruments have different resolution and acquisition rates, their ability to detect glaucoma was similar.

Ascorbic acid concentration is reduced in the secondary aqueous humour of glaucomatous patients.

BACKGROUND: We aimed to evaluate the ascorbic acid concentration in secondary aqueous humour (AH) from glaucomatous patients and to compare it with primary AH from primary open-angle glaucoma patients and non-glaucomatous patients. METHODS: Primary AH samples were prospectively obtained from clinically uncontrolled primary open-angle glaucoma patients and senile cataract patients (controls) prior to trabeculectomy and cataract surgery. Secondary AH samples were obtained from eyes with previous intraocular surgery, prior to trabeculectomy or cataract surgery. AH (0.1 mL) was aspirated by inserting a 26-gauge needle into the anterior chamber just before surgery and then immediately stored at -80 degrees C. The ascorbic acid concentration was determined in a masked fashion by high-pressure liquid chromatography. RESULTS: A total of 18 patients with senile cataract, 16 glaucomatous patients with primary AH (no previous intraocular surgery) and 11 glaucomatous patients with secondary AH (previous intraocular surgery) were included. There was no difference in mean age between groups (P = 0.15). The mean +/- standard deviation concentration of ascorbic acid in the secondary AH from glaucomatous patients (504 +/- 213 micromol/L [95% confidence interval {CI}, 383-624]) was significantly lower than the concentration of ascorbic acid found in the primary aqueous of primary open-angle glaucoma (919 +/- 427 micromol/L [95% CI, 709-1128]) and control patients (1049 +/- 433 micromol/L [95% CI, 848-1249]; P < 0.01, Kruskal-Wallis test). CONCLUSIONS: The ascorbic acid concentration in secondary AH of glaucomatous patients was approximately twofold lower in comparison with primary AH of glaucomatous and cataract patients. The implications of a reduced concentration of ascorbic acid in the secondary AH deserve further investigation.

Identification of the Most Accurate Spectral-domain Optical Coherence Tomography Parameters in Eyes With Early High-Tension and Low-Tension Glaucoma.

PURPOSE: The aim of the study was to compare the diagnostic ability of macular ganglion cell complex (GCC) and peripapillary retinal nerve fiber layer (pRNFL) thickness in high-tension glaucoma (HTG) and low-tension glaucoma (LTG). PATIENTS AND METHODS: Glaucoma was defined as glaucomatous optic neuropathy and reproducible visual field defects. Patients were classified as having LTG if untreated intraocular pressure was ≤21 mm Hg on 2 different occasions. Only eyes with early glaucoma (mean deviation <-6 dB) were included. All patients underwent spectral-domain optical coherence tomography (SDOCT) imaging. RESULTS: A total of 56 normal subjects, 64 HTG patients, and 35 LTG patients were enrolled. Overall, after adjusting for mean deviation and age, the average pRNFL thickness in eyes with LTG was 18.7 µm thinner than in eyes with HTG (17% difference, P<0.01). In the HTG group, no significant difference was found between areas under the receiver operating characteristic curve (AUCs) for average GCC and average pRNFL thicknesses (0.77 vs. 0.68, P=0.06). In the LTG group, average pRNFL thickness had a significantly larger AUC compared with average GCC thickness (0.95 vs. 0.81, P<0.001). Comparing AUCs between HTG and LTG groups, although the average GCC had similar AUCs in both groups (P=0.47), the average pRNFL thickness had a significantly larger AUC in the LTG group (P<0.001). CONCLUSIONS: In eyes with early glaucoma, the pRNFL thickness scan seems to be a more accurate SDOCT protocol to identify those with LTG compared with the GCC thickness scan.

Eyes with Suspicious Appearance of the Optic Disc and Normal Intraocular Pressure: Using Clinical and Epidemiological Characteristics to Differentiate Those with and without Glaucoma.

Among all glaucoma suspects, eyes with optic nerve head features suspicious or suggestive of early glaucoma are probably those that offer the greatest challenge for clinicians. In contrast with the robust longitudinal data published on ocular hypertension, there is no specific management guideline for these patients. Therefore, evaluating eyes with suspicious optic disc appearance and normal intraocular pressure (IOP), we sought to investigate potential differences in clinical and epidemiological characteristics to differentiate those with normal-tension glaucoma (NTG) from those with presumed large physiological optic disc cups (pLPC). In this observational case-control study, we consecutively enrolled individuals with pLPC and NTG. All eyes had vertical cup-to-disc ratio (VCDR)≥0.6 and untreated IOP<21 mmHg. Glaucomatous eyes had reproducible visual field defects. Eyes with pLPC required normal visual fields and ≥30 months of follow-up with no evidence of glaucomatous neuropathy. Clinical and epidemiological parameters were compared between groups. Eighty-four individuals with pLPC and 40 NTG patients were included. Regarding our main results, NTG patients were significantly older and with a higher prevalence of Japanese descendants (p<0.01). Not only did pLPC eyes have smaller mean VCDR, but also larger optic discs (p≤0.04). There were no significant differences for gender, central corneal thickness, and spherical equivalent (p≥0.38). Significant odds ratios (OR) were found for race (OR = 2.42; for Japanese ancestry), age (OR = 1.05), VCDR (OR = 5.03), and disc size (OR = 0.04; p≤0.04). In conclusion, in patients with suspicious optic disc and normal IOP, those with older age, Japanese ancestry, smaller optic discs, and larger VCDR are more likely to have NTG, and therefore, deserve deeper investigation and closer monitoring.

Suitability of the Visual Field Index according to Glaucoma Severity.

PURPOSE: To investigate the suitability of the visual field index (VFI) in different degrees of disease severity in glaucoma patients. METHODS: In this cross-sectional study, we consecutively enrolled patients with primary open-angle glaucoma and glaucoma suspects (ocular hypertension). All eyes required a reliable standard automated perimetry (SAP) test to be included. Subjects were categorized into five groups based on glaucoma severity using SAP's mean deviation (MD). To evaluate the correlation among VFI, MD and pattern standard deviation (PSD), a linear regression model was built. To evaluate the nature of the correlation (i.e. linear vs nonlinear), results were plotted in a scatterplot graph. RESULTS: One hundred and twenty-two eyes of 81 patients (mean age, 59.8 ± 14.5 years) were included. A strong, positive association was found between MD and VFI values (R(2) = 0.98, p < 0.001), showing a 3.2% reduction in the VFI for each dB loss in the MD index. It was noticed that 15% of eyes with mild glaucoma (average MD of -3.1 dB) had VFI > 99%. Considering only the eyes with mild and moderate damage in the regression, we found a weaker (nonlinear) correlation than the one we found using all eyes (R(2) = 0.85, p < 0.001). There was also a significant, nonlinear correlation between VFI and PSD (R(2) = 0.85, p < 0.001). Although higher PSD values were found with increasing visual field damage, this initial trend was reversed when VFI became smaller than 50%, approximately. CONCLUSION: Visual field index had a strong correlation with MD; however, this correlation was weaker in mild disease, as some patients with early disease had very high VFI values (ceiling effect). Therefore, initial deterioration in visual field status (as assessed by MD values) in patients with early disease may not be detectable using the VFI alone. How to cite this article: Sousa MCC, Biteli LG, Dorairaj S, Maslin JS, Leite M, Prata TS. Suitability of the Visual Field Index according to Glaucoma Severity. J Curr Glaucoma Pract 2015;9(3):65-68.

Eyes with large disc cupping and normal intraocular pressure: using optical coherence tomography to discriminate those with and without glaucoma.

We evaluated the ability of spectral-domain optic coherence tomography (SD-OCT) to differentiate large physiological optic disc cupping (LPC) from glaucomatous cupping in eyes with intraocular pressure (IOP) within the normal range. We prospectively enrolled patients with glaucoma or presumed LPC. Participants had optic discs with confirmed or suspected glaucomatous damage (defined as a vertical cup-to-disc ratio≥0.6), and all eyes had known untreated IOP<21 mmHg. For glaucomatous eyes, a reproducible glaucomatous visual field (VF) defect was required. LPC eyes required normal VF and no evidence of progressive glaucomatous neuropathy (follow-up≥30 months). Peripapillary retinal nerve fiber layer (pRNFL) and macular ganglion cell complex (GCC) thicknesses were obtained using SD-OCT. For all studied parameters of pRNFL and GCC thicknesses, eyes with glaucoma (n=36) had significantly thinner values compared to eyes with LPC (n=71; P<0.05 for all comparisons). In addition, pRNFL parameters had sensitivity of 66.7% and specificity of 83.1%, and GCC parameters had sensitivity of 61.2% and specificity of 81.7%. The combination of the two analyses increased the sensitivity to 80.6%. In conclusion, while evaluating patients with large optic disc cupping and IOP in the statistically normal range, SD-OCT had only limited diagnostic ability to differentiate those with and without glaucoma. Although the diagnostic ability of the pRNFL and the GCC scans were similar, these parameters yielded an increase in sensitivity when combined, suggesting that both parameters could be considered simultaneously in these cases.

Comparison of different spectral domain OCT scanning protocols for diagnosing preperimetric glaucoma.

PURPOSE: To compare the ability of spectral-domain optical coherence tomography (SDOCT) retinal nerve fiber layer (RNFL), optic nerve head (ONH), and macular measurements to detect preperimetric glaucomatous damage. METHODS: The study included 142 eyes from 91 patients suspected of having the disease based on the appearance of the optic disc. All eyes had normal visual fields before the imaging session. Forty-eight eyes with progressive glaucomatous damage were included in the preperimetric glaucoma group. Ninety-four eyes without any evidence of progressive glaucomatous damage and followed untreated for 12.8 ± 3.6 years were used as controls. Areas under the receiver operating characteristic curves (AUC) were calculated to summarize diagnostic accuracies of the parameters. RESULTS: The three RNFL parameters with the largest AUCs were average RNFL thickness (0.89 ± 0.03), inferior hemisphere average thickness (0.87 ± 0.03), and inferior quadrant average thickness (0.85 ± 0.03). The three ONH parameters with the largest AUCs were vertical cup-to-disc ratio (0.74 ± 0.04), rim area (0.72 ± 0.05), and rim volume (0.72 ± 0.05). The three macular parameters with the largest AUCs were GCC average thickness (0.79 ± 0.04), GCC inferior thickness (0.79 ± 0.05), and GCC superior thickness (0.76 ± 0.05). Average RNFL thickness performed better than vertical cup-to-disc ratio (0.89 vs. 0.74; P = 0.007) and GCC average thickness (0.89 vs. 0.79; P = 0.015). CONCLUSIONS: SDOCT RNFL measurements performed better than ONH and macular measurements for detecting preperimetric glaucomatous damage in a cohort of glaucoma suspects. (ClinicalTrials.gov number, NCT00221897.).

African descent and glaucoma evaluation study: asymmetry of structural measures in normal participants.

PURPOSE: The purpose of the study is to determine the degree of intereye asymmetry of optic disc topography and retinal nerve fiber layer (RNFL) thickness in healthy individuals of African descent (AD) and European descent (ED). DESIGN: Observational, clinical study. METHODS: Five hundred nineteen healthy individuals (AD, n=262, mean age=44.9 years; ED, n=257, mean age=47.1 years) from the African Descent and Glaucoma Evaluation Study and Diagnostic Innovations in Glaucoma Study were tested using Heidelberg retina romograph (HRT), GDx variable corneal compensation (GDx-VCC), and standard, automated perimetry within 6 months of one another. HRT-II measurements included cup area, cup volume, rim area, and rim volume. GDx-VCC measurements included average RNFL thickness. Intereye asymmetry was calculated as the absolute value of the differences in measurements between the right and left eye. RESULTS: AD participants showed significantly higher median asymmetry in cup volume and rim volume (P<0.001 and 0.033, respectively) compared with ED participants. The effect of race lost significance after adjustment for mean disc area and disc area asymmetry in multivariable models. Axial length asymmetry was not correlated with increased asymmetry in any of this study's asymmetry parameters. Normal ranges of asymmetry for the HRT-II measurements of cup area (up to 0.39 mm), cup volume (up to 0.15 mm), rim area (up to 0.45 mm), and rim volume (up to 0.22 mm) were derived, as were asymmetry ranges for GDx-VCC-measured average RNFL thickness (up to 6.25 µm). CONCLUSIONS: The effect of race was no longer significant after adjustment for mean disc area and disc area asymmetry. Individuals with asymmetries with magnitudes greater than those of the normal ranges could be considered as suspicious for glaucoma.

Structure-function relationships using the Cirrus spectral domain optical coherence tomograph and standard automated perimetry.

PURPOSE: To evaluate the relationship between glaucomatous structural damage assessed by the Cirrus Spectral Domain OCT (SDOCT) and functional loss as measured by standard automated perimetry (SAP). METHODS: Four hundred twenty-two eyes (78 healthy, 210 suspects, 134 glaucomatous) of 250 patients were recruited from the longitudinal Diagnostic Innovations in Glaucoma Study and from the African Descent and Glaucoma Evaluation Study. All eyes underwent testing with the Cirrus SDOCT and SAP within a 6-month period. The relationship between parapapillary retinal nerve fiber layer thickness (RNFL) sectors and corresponding topographic SAP locations was evaluated using locally weighted scatterplot smoothing and regression analysis. SAP sensitivity values were evaluated using both linear as well as logarithmic scales. We also tested the fit of a model (Hood) for structure-function relationship in glaucoma. RESULTS: Structure was significantly related to function for all but the nasal thickness sector. The relationship was strongest for superotemporal RNFL thickness and inferonasal sensitivity (R(2)=0.314, P<0.001). The Hood model fitted the data relatively well with 88% of the eyes inside the 95% confidence interval predicted by the model. CONCLUSIONS: RNFL thinning measured by the Cirrus SDOCT was associated with correspondent visual field loss in glaucoma.

Association between corneal biomechanical properties and glaucoma severity.

PURPOSE: To investigate the association between corneal biomechanical parameters using the Ocular Response Analyzer (ORA) and glaucoma severity. DESIGN: Observational cross-sectional study. METHODS: Two hundred ninety-nine eyes of 191 patients with confirmed or suspect glaucoma were recruited at the University of California, San Diego. Corneal hysteresis (CH) and corneal resistance factor (CRF) were obtained from all participants. Standard automated perimetry was done using the 24-2 Swedish Interactive Threshold Algorithm. Retinal nerve fiber layer (RNFL) thickness measurements were obtained using GDx ECC and spectral-domain optical coherence tomography (SD-OCT). The association between ORA parameters and disease severity was evaluated using univariable and multivariable regression models. RESULTS: CH and CRF were both positively associated with mean defect (MD) (R(2) = 0.03; P < .01 and R(2) = 0.10; P < .01, respectively). In multivariable analysis, the association between CRF and MD remained significant while CH to MD did not (P < .01 and P = .77). In the GDx ECC subgroup (204 eyes), there was a weak association between CH and CRF and average RNFL thickness (R(2) = 0.07; P < .01 and R(2) = 0.05; P < .01, respectively), which was not observed in the SD-OCT subgroup (146 eyes) (R(2) = 0.01; P = .30 and R(2) = 0.01; P = .21). After adjusting for central corneal thickness, age, and axial length, the relationship of CH and CRF to RNFL thickness no longer reached statistical significance. CONCLUSIONS: The current study found only a weak relationship between corneal biomechanical parameters and measures of structural and functional damage in glaucoma.

Combining structural and functional measurements to improve detection of glaucoma progression using Bayesian hierarchical models.

PURPOSE: To present and evaluate a new methodology for combining longitudinal information from structural and functional tests to improve detection of glaucoma progression and estimation of rates of change. METHODS: This observational cohort study included 434 eyes of 257 participants observed for an average of 4.2 ± 1.1 years and recruited from the Diagnostic Innovations in Glaucoma Study (DIGS). The subjects were examined annually with standard automated perimetry, optic disc stereophotographs, and scanning laser polarimetry with enhanced corneal compensation. Rates of change over time were measured using the visual field index (VFI) and average retinal nerve fiber layer thickness (TSNIT average). A bayesian hierarchical model was built to integrate information from the longitudinal measures and classify individual eyes as progressing or not. Estimates of sensitivity and specificity of the bayesian method were compared with those obtained by the conventional approach of ordinary least-squares (OLS) regression. RESULTS: The bayesian method identified a significantly higher proportion of the 405 glaucomatous and suspect eyes as having progressed when compared with the OLS method (22.7% vs. 12.8%; P < 0.001), while having the same specificity of 100% in 29 healthy eyes. In addition, the bayesian method identified a significantly higher proportion of eyes with progression by optic disc stereophotographs compared with the OLS method (74% vs. 37%; P = 0.001). CONCLUSIONS: A bayesian hierarchical modeling approach for combining functional and structural tests performed significantly better than the OLS method for detection of glaucoma progression. (ClinicalTrials.gov number, NCT00221897.).

Effect of disease severity and optic disc size on diagnostic accuracy of RTVue spectral domain optical coherence tomograph in glaucoma.

PURPOSE: To evaluate the effect of disease severity and optic disc size on the diagnostic accuracies of optic nerve head (ONH), retinal nerve fiber layer (RNFL), and macular parameters with RTVue (Optovue, Fremont, CA) spectral domain optical coherence tomography (SDOCT) in glaucoma. METHODS: 110 eyes of 62 normal subjects and 193 eyes of 136 glaucoma patients from the Diagnostic Innovations in Glaucoma Study underwent ONH, RNFL, and macular imaging with RTVue. Severity of glaucoma was based on visual field index (VFI) values from standard automated perimetry. Optic disc size was based on disc area measurement using the Heidelberg Retina Tomograph II (Heidelberg Engineering, Dossenheim, Germany). Influence of disease severity and disc size on the diagnostic accuracy of RTVue was evaluated by receiver operating characteristic (ROC) and logistic regression models. RESULTS: Areas under ROC curve (AUC) of all scanning areas increased (P < 0.05) as disease severity increased. For a VFI value of 99%, indicating early damage, AUCs for rim area, average RNFL thickness, and ganglion cell complex-root mean square were 0.693, 0.799, and 0.779, respectively. For a VFI of 70%, indicating severe damage, corresponding AUCs were 0.828, 0.985, and 0.992, respectively. Optic disc size did not influence the AUCs of any of the SDOCT scanning protocols of RTVue (P > 0.05). Sensitivity of the rim area increased and specificity decreased in large optic discs. CONCLUSIONS: Diagnostic accuracies of RTVue scanning protocols for glaucoma were significantly influenced by disease severity. Sensitivity of the rim area increased in large optic discs at the expense of specificity.

Structure-function relationship in glaucoma using spectral-domain optical coherence tomography.

OBJECTIVES: To determine the structure-function relationship in glaucoma using spectral-domain optical coherence tomography (SDOCT)-derived structural measurements and to evaluate this relationship using a linear model. METHODS: In a cross-sectional study, structure-function relationships were determined for all the participants in the DIGS (Diagnostic Innovations in Glaucoma Study) and the ADAGES (African Descent and Glaucoma Evaluation Study) who had undergone standard automated perimetry (SAP) and SDOCT within 6 months of each other. Strength of relationship was reported as coefficient of determination (R(2)). The relationship was also evaluated using a previously described linear model. RESULTS: The results of 579 SAP and SDOCT examinations from 80 eyes of 47 control subjects, 199 eyes of 130 patients with suspected glaucoma, and 213 eyes of 146 patients with glaucoma were analyzed. The R(2) for the association between SAP total deviation and SDOCT variables ranged from 0.01 (P = .02) for the nasal rim area to 0.30 (P < .001) for inferior inner retinal thickness at the macula. The linear model fitted the data well. CONCLUSIONS: The strongest structure-function associations using SDOCT were found for retinal nerve fiber layer measurements at arcuate areas and inner retinal thickness at the macula measurements. The linear model is useful in studying the structure-function relationship in glaucoma.

Agreement among spectral-domain optical coherence tomography instruments for assessing retinal nerve fiber layer thickness.

PURPOSE: To assess the agreement of parapapillary retinal nerve fiber layer (RNFL) thickness measurements among 3 spectral-domain optical coherence tomography (SD-OCT) instruments. DESIGN: Observational, cross-sectional study. METHODS: Three hundred thirty eyes (88 with glaucoma, 206 glaucoma suspects, 36 healthy) from 208 individuals enrolled in the Diagnostic Innovations in Glaucoma Study (DIGS) were imaged using RTVue, Spectralis and Cirrus in a single visit. Agreement among RNFL thickness measurements was assessed using Bland-Altman plots. The influence of age, axial length, disc size, race, spherical equivalent, and disease severity on the pairwise agreements between different instruments was assessed by regression analysis. RESULTS: Although RNFL thickness measurements between different instruments were highly correlated, Bland-Altman analyses indicated the presence of fixed and proportional biases for most of the pairwise agreements. In general, RTVue measurements tended to be thicker than Spectralis and Cirrus measurements. The agreement in average RNFL thickness measurements between RTVue and Spectralis was affected by age (P = .001) and spherical equivalent (P < .001), whereas the agreement between Spectralis and Cirrus was affected by axial length (P = .004) and spherical equivalent (P < .001). Disease severity influenced the agreement between Spectralis and both RTVue and Cirrus (P = .001). Disc area and race did not influence the agreement among the devices. CONCLUSIONS: RNFL thickness measurements obtained by different SD-OCT instruments were not entirely compatible and therefore they should not be used interchangeably. This may be attributable in part to differences in RNFL detection algorithms. Comparisons with histologic measurements could determine which technique is most accurate.

Corneal asphericity and spherical aberration after refractive surgery.

PURPOSE: To evaluate changes in corneal asphericity (Q) and spherical aberrations after refractive surgery using Scheimpflug imaging. SETTING: University of California, San Diego, Shiley Eye Center, La Jolla, California, USA. DESIGN: Cohort study. METHODS: After wavefront-guided laser in situ keratomileusis, patients within ± 0.50 diopter of plano and with an uncorrected distance visual acuity of at least 20/20 were evaluated. The Q values and corneal spherical aberration Zernike values were obtained using Scheimpflug imaging preoperatively and 1 to 3 months postoperatively. RESULTS: The study enrolled 177 myopic eyes and 32 hyperopic eyes. The mean Q value was -0.28 ± 0.11 (SD) and -0.22 ± 0.15, respectively, preoperatively and +0.35 ± 0.44 and -0.64 ± 0.31, respectively, postoperatively. The asphericity change was highly correlated with preoperative spherical equivalent (r(2) = 0.81; P ≤ .001). The mean corneal spherical aberration was +0.21 ± 0.08 µm in myopic eyes and +0.36 ± 0.11 µm in hyperopic eyes preoperatively and +0.36 ± 0.17 µm and 0.00 ± 0.29 µm, respectively, postoperatively. The corneal spherical aberration changes were correlated with the amount of preoperative refractive error (r(2) = 0.34; P < .001). There was a tendency for Q values and spherical aberrations to become more positive after myopic ablation and more negative after hyperopic ablation. CONCLUSIONS: Myopic and hyperopic corrections induced changes in the Q value and spherical aberrations in opposite directions (ie, positive and negative, respectively). The changes depended on the magnitude of the refractive correction. FINANCIAL DISCLOSURE: No author has a financial or proprietary interest in any material or method mentioned.

Comparison of corneal biomechanical properties between healthy blacks and whites using the Ocular Response Analyzer.

PURPOSE: To analyze and compare corneal biomechanical properties in healthy black and white subjects using the Ocular Response Analyzer (ORA) and to evaluate their relationship with other ocular parameters. DESIGN: Observational cross-sectional study. METHODS: One hundred eighty one eyes (46 in blacks, 135 in whites) of 119 patients (37 blacks, 82 whites) were recruited from the longitudinal Diagnostic Innovations in Glaucoma Study (DIGS) and from the African Descent and Glaucoma Evaluation Study (ADAGES) at the University of California, San Diego. Corneal curvature, axial length, central corneal thickness (CCT), corneal hysteresis (CH), and corneal resistance factor (CRF) were obtained from all participants. Univariable and multivariable regression analyses were used to evaluate the associations between ORA measurements and age, CCT, axial length, corneal curvature, and race. RESULTS: Black subjects had significantly lower values of CH (9.7 mm Hg vs 10.4 mm Hg; P = .033), CRF (9.84 mm Hg vs 10.70 mm Hg; P = .028), and CCT (534 mum vs 562 mum; P = .001) compared to white subjects. A significant relationship was found between CH and CCT (R(2) = 0.25; P < .001) and between CRF and CCT (R(2) = 0.42; P < .001). After adjusting for CCT, age, axial length, and corneal curvature, the difference between blacks and whites in CH (P = .077) and CRF (P = .621) measurements lost statistical significance. CONCLUSION: Black subjects tended to have lower measurements of corneal hysteresis compared to white subjects; however, this was largely explained by differences in corneal thickness. Therefore, it is unlikely that CH would have an independent effect in explaining differences in susceptibility of disease between these 2 racial groups.

Effect of disease severity on the performance of Cirrus spectral-domain OCT for glaucoma diagnosis.

PURPOSE: To evaluate the effect of disease severity on the diagnostic accuracy of the Cirrus Optical Coherence Tomograph (Cirrus HD-OCT; Carl Zeiss Meditec, Inc., Dublin, CA) for glaucoma detection. METHODS: One hundred thirty-five glaucomatous eyes of 99 patients and 79 normal eyes of 47 control subjects were recruited from the longitudinal Diagnostic Innovations in Glaucoma Study (DIGS). The severity of the disease was graded based on the visual field index (VFI) from standard automated perimetry. Imaging of the retinal nerve fiber layer (RNFL) was obtained using the optic disc cube protocol available on the Cirrus HD-OCT. Pooled receiver operating characteristic (ROC) curves were initially obtained for each parameter of the Cirrus HD-OCT. The effect of disease severity on diagnostic performance was evaluated by fitting an ROC regression model, with VFI used as a covariate, and calculating the area under the ROC curve (AUCs) for different levels of disease severity. RESULTS: The largest pooled AUCs were for average thickness (0.892), inferior quadrant thickness (0.881), and superior quadrant thickness (0.874). Disease severity had a significant influence on the detection of glaucoma. For the average RNFL thickness parameter, AUCs were 0.962, 0.932, 0.886, and 0.822 for VFIs of 70%, 80%, 90%, and 100%, respectively. CONCLUSIONS: Disease severity had a significant effect on the diagnostic performance of the Cirrus HD-OCT and thus should be considered when interpreting results from this device and when considering the potential applications of this instrument for diagnosing glaucoma in the various clinical settings.