PRESERFLO™ Microshunt: 1-Year Results of a 25-Gauge vs. 27-Gauge Needle Tract.

Background: The purpose of this study was to evaluate the effectiveness and safety of the PreserFlo™ microshunt (PMS) using a 25-Gauge vs. 27-Gauge needle tract. Methods: This is a prospective postoperative examination of 60 glaucoma eyes that received a PMS. The main outcome measures were intraocular pressure (IOP), glaucoma drug score (GDS), Kaplan-Meier success rates, complications, and secondary intervention rates. Two subgroups were formed for data comparison: 27-Gauge (27G), and 25-Gauge (25G). Success was defined as IOP < 18 mmHg together with ≥20% IOP reduction with medication allowed (qualified success = QS18) or not (full success = FS18). Results: IOP and GDS were reduced from baseline to the 1-year study visit as follows: All eyes from 23.4 ± 8.6 mmHg (3.1 ± 0.9) to 15.1 ± 5.9 mmHg (0.8 ± 1.1); 25G from 24.2 ± 7.3 mmHg (3.0 ± 0.8) to 12.7 ± 2.7 mmHg (0.5 ± 0.8); and 27G from 23.1 ± 9.2 mmHg (3.1 ± 1.0) to 16.2 ± 6.7 mmHg (0.9 ± 1.2). IOP at one year was lower in the 25G group compared to the 27G group (p = 0.035). Bleb needling was required in eight (13.3%) eyes and open bleb revisions in three (5.0%). Transient hypotony occurred in 21% and choroidal effusion in 8% of all eyes. Choroidal effusions were more frequent in the 25G group (21%) compared to the 27G group (2%, p = 0.031). One-year success rates were significantly higher in the 25G group compared to the 27G group for both QS18 (25G: 67.9% vs. 27G: 35.7%, p = 0.002) and FS18 (25G: 63.6% vs. 27G: 29.2%, p = 0.007). Conclusions: The PreserFlo microshunt is an effective and safe glaucoma surgery with a low rate of bleb revisions or needlings. We show that the 25G needle tract might be more efficient for IOP control at the cost of increased IOP-related complications compared to 27G.

Thermally tuned VCSEL at 850†nm as a low-cost alternative source for full-eye SS-OCT.

Swept-source optical coherence tomography (SS-OCT) demonstrates superior performance in comparison to spectral domain OCT with regard to depth ranging. The main driver of cost for SS-OCT systems is, however, the price of the source. Here we show a low-cost alternative swept source that uses a thermally tuned vertical-cavity surface-emitting laser (VCSEL) at 850 nm. Its center wavelength can be tuned by adjusting the operating temperature through modulation of the injection current. At 2 kHz sweep rate, the depth range of the system was 5 cm, with a sensitivity roll-off of under -3 dB across this range. The system achieved a sensitivity of 97 dB with a sample beam power of 0.3 mW and an axial resolution of 50 µm in air. To demonstrate the system performance in vivo, an eye of a healthy volunteer was measured, and full-eye scans were acquired at 25 and 50 kHz from the cornea to the retina. Based on our results, we believe that this technology can be used as a cost-effective alternative OCT for point-of-care diagnostics.

Birefringent Properties of the Peripapillary Retinal Nerve Fiber Layer in Healthy and Glaucoma Subjects Analyzed by Polarization-Sensitive OCT.

Purpose: To study the circumpapillary retinal nerve fiber layer (RNFL) birefringence (BIR) of early glaucoma and age-matched healthy eyes using polarization-sensitive optical coherence tomography (PS-OCT). Methods: In this prospective cross-sectional study, we compared virtual circular PS-OCT B-scans with a diameter of 3.5 mm centered on the optic disc (OD) acquired with a PS-OCT prototype (860 nm center wavelength). Early glaucoma was defined by the glaucomatous appearance of the OD and a pathologic visual field test with a mean deviation (MD) better than -6 dB. The main outcome parameters were BIR, RNFL-thickness (RNFL-T), and phase retardation (RET). The BIR value at each virtual A-scan position was the quotient of the RET measured at the inner segment/outer segment junction divided by the RNFL-T. Results: The dataset comprised 49 early glaucoma patients (mean ± standard deviation [SD]: 64 ± 10 years) and 49 healthy control subjects (61 ± 9 years). Glaucomatous eyes showed a statistically significant lower BIR globally (mean ± SD: 0.108 ± 0.008°/µm vs. 0.112 ± 0.009°/µm, P = 0.033), superiorly (0.116 ± 0.017°/µm vs. 0.126 ± 0.013°/µm, P = 0.0001), and inferiorly (0.112 ± 0.011°/µm vs. 0.121 ± 0.011°/µm, P < 0.0001), and increased BIR in the temporal quadrant (0.088 ± 0.015°/µm vs. 0.078 ± 0.014°/µm, P = 0.0001) compared to healthy eyes. Conclusions: We report a reduced BIR of the RNFL in early perimetric glaucoma, which can be interpreted as a sign of loss or change of intracellular microtubules and may contribute to a better understanding of early disease development. Prospective longitudinal studies are needed to determine whether BIR is altered in pre-perimetric human glaucoma before RNFL-T decline.

Retinal Oxygen Extraction in Patients with Primary Open-Angle Glaucoma.

Objective: To compare total retinal oxygen extraction between patients with primary open-angle glaucoma (POAG) and healthy control subjects. Design: A prospective, single-center, cross-sectional, case−control study performed at the Medical University of Vienna. Subjects: Forty patients with POAG and 40 age- and sex-matched control subjects. Methods: Total retinal blood flow was measured using Doppler optical coherence tomography (OCT). Retinal arterial and venous oxygen saturation was measured using reflectance spectroscopy. From these parameters, oxygen content in the retinal arterial and venous circulation as well as total retinal oxygen extraction were calculated. Results: Total retinal blood flow was lower in POAG (25.2 ± 6.7 µL/min) as compared to healthy control subjects (35.6 ± 8.3 µL/min, p < 0.001). Retinal arterial oxygen content was not different between the two groups (0.18 ± 0.01 mL(O2)/mL in both groups, p < 0.761), but retinal venous oxygen content was higher in POAG (0.15 ± 0.01 mL(O2)/mL) than in healthy controls (0.14 ± 0.01 mL(O2)/mL p < 0.001). Accordingly, retinal oxygen extraction was reduced in POAG (0.8 ± 0.3 µL(O2)/min as compared to healthy controls: 1.4 ± 0.4 µL(O2)/min, p < 0.001). There was a significant association between total retinal blood flow and total retinal oxygen extraction with measures of structural and functional damage (p < 0.001 each). Conclusions: This study indicates that POAG is associated with a reduction in total retinal oxygen extraction linked to structural and functional damage of the disease. Since the technology is non-invasive, it allows for longitudinal studies investigating to which degree low retinal oxygen extraction is linked to the progression of the disease.

Automatic retinal nerve fiber bundle tracing based on large field of view polarization sensitive OCT data.

A technique to accurately estimate trajectories of retinal nerve fiber bundles (RNFB) in a large field of view (FOV) image covering 45° is described. The method utilizes stitched projections of polarization-sensitive optical coherence tomography (PS-OCT) data, as well as a mathematical model of average RNFB trajectories as prior. The fully automatic process was applied to data recorded in healthy subjects and glaucoma patients and automatically detected individual RNFB trajectories are compared to manual traces.

Optical coherence tomography-measured retinal nerve fiber layer thickness values compensated with a multivariate model and discrimination between stable and progressing glaucoma suspects.

PURPOSE: Our previously introduced multivariate model, compensating for intersubject variability, was applied to circumpapillary retinal nerve fiber layer (RNFL) values measured with optical coherence tomography in glaucoma suspects with or without prior progressive optic disc (OD) change in a series of confocal scanning laser tomography (CSLT, HRT III) measurements. METHODS: In this prospective study, OD change during CSLT follow-up was determined with strict, moderate, and liberal criteria of the topographic change analysis (TCA). Model compensation (MC) as well as age compensation (AC) was applied to RNFL sectors (RNFLMC vs. RNFLAC). Diagnostic performance of RNFLMC vs. RNFLAC was tested with an area under the receiver operating characteristic (AUROC) and was compared between methods. RESULTS: Forty-two glaucoma suspects were included. Patients without prior progressive OD change during the CSLT follow-up (= stable) had thicker RNFL thickness values in most areas and for all progression criteria. RNFLMC AUROC for the global RNFL (0.719) and the inferior quadrant (0.711) performed significantly better compared with RNFLAC AUROC (0.594 and 0.631) to discriminate between stable and progressive glaucoma suspects as defined by the moderate criteria of CSLT progression analysis (p = 0.028; p = 0.024). CONCLUSION: MC showed a slight but significant improvement in detection of subjects with prior progressive OD change among a group of glaucoma suspects, when compared to AC, which is the compensation method commonly used during OCT data evaluation in daily routine. Further studies are warranted to validate the present results.

Needling and open filtering bleb revision after XEN-45 implantation-a retrospective outcome comparison.

PURPOSE: To compare efficacy and safety of needling and open bleb revision after XEN-45 surgery. METHODS: This retrospective study represents real-life data of patients who underwent XEN-45 surgery between November 2014 and June 2018 in the Vienna General Hospital. The following groups were formed for data evaluation: (PSEA) primary surgery secondary intervention allowed (n = 268); (PS) primary surgery until secondary intervention (n = 268); (N) first needling until additional secondary intervention (n = 55); (BR) first bleb revision until additional secondary intervention (n = 105). Main outcome measures were pre- and postoperative intraocular pressure (IOP), number of glaucoma medication (GM), Kaplan-Meier success rates, and secondary intervention rates. Success was defined as postoperative IOP < 21 mmHg and < 18 mmHg together with ≥ 20% IOP reduction with medication allowed. RESULTS: IOP (and GM) was lowered from 23.5 ± 8.0 (GM 3.1 ± 1.0) to 14.9 ± 8.2 mmHg (1.2 ± 1.4) in group PSEA and 18.1 ± 8.2 mmHg (1.5 ± 1.4) in group PS, in group N from 23.2 ± 10.1 (1.5 ± 1.0) to 19.3 ± 8.5 mmHg (2.2 ± 1.3) and in group BR from 22.0 ± 8.0 mmHg (2.5 ± 1.1) to 15.5 ± 6.4 mmHg (1.3 ± 1.5) after a median follow-up of 16.0, 8.4, 4.8, and 7.3 months, respectively. Success rates at 1 year were significantly higher in group BR (50.7%) compared to PS (37.7%, p = 0.019) and N (24.3%; p = 0.015). An additional intervention was required less frequently in group BR (17.1%) compared to group PS (49.6%, p < 0.001) and group N (54.5%, p < 0.001). CONCLUSION: Our data appear to indicate favorable outcomes for open XEN bleb revision in terms of Kaplan-Meier success rates and secondary intervention rate compared to the needling procedure.

Generating large field of view en-face projection images from intra-acquisition motion compensated volumetric optical coherence tomography data.

A technique to generate large field of view projection maps of arbitrary optical coherence tomography (OCT) data is described. The technique is divided into two stages - an image acquisition stage that features a simple to use fast and robust retinal tracker to get motion free retinal OCT volume scans - and a stitching stage where OCT data from different retinal locations is first registered against a reference image using a custom pyramid-based approach and finally stitched together into one seamless large field of view (FOV) image. The method is applied to data recorded with a polarization sensitive OCT instrument in healthy subjects and glaucoma patients. The tracking and stitching accuracies are quantified, and finally, large FOV images of retinal nerve fiber layer retardation that contain the arcuate nerve fiber bundles from the optic nerve head to the raphe are demonstrated.

Comparison of Spectralis and Cirrus spectral domain optical coherence tomography for the objective morphometric assessment of the neuroretinal rim width.

PURPOSE: The assessment of cup-disc ratio as a surrogate parameter for the neuroretinal rim width (NRW) of the optic nerve is well established, but prone to human error and imprecision. Objective assessment of the NRW is provided by spectral domain optical coherence tomography (SD-OCT). This study is the first to systematically compare NRW measurements acquired with the Carl Zeiss Meditech Cirrus HD-OCT 5000 and the Heidelberg Engineering Spectralis SD-OCT. METHODS: In this cross-sectional study, 20 eyes of each 20 glaucoma patients and 20 age-matched healthy controls underwent ophthalmic examination, SD-OCT imaging, and computer perimetry. Regression analyses were performed for the NRW comparability and the effect of the rotational alignment disconcordance (RAD), receiver-operating characteristics (ROC) for NRW-based healthy glaucoma discrimination capability, and Pearson's correlation for covariate association. RESULTS: Mean NRW differences were 8 ± 48 µm (p = 0.4528), 91 ± 80 µm (p < 0.01), and 49 ± 77 µm (p < 0.001) in the glaucoma, healthy, and whole group. On average, the Cirrus showed higher NRW values (+ 50 µm) than the Spectralis, this difference increased with values starting with 159 µm. Discrimination ROC were 1.0 (Spectralis) and 0.9675 (Cirrus). RAD showed very little effect on NRW (R2 = 0.9661, p < 0.001). NRW-covariate correlation was highly significant (p < 0.001) with both devices for clinical cup/disc ratio, calculated rim width, visual field mean, and pattern deviations. CONCLUSIONS: Our results suggest to only cautiously compare Spectralis and Cirrus NRW measurements only in patients with morphologically manifest glaucoma. For morphological progression analysis, we recommend the continuous usage of the same device.

Optic nerve head blood flow regulation during changes in arterial blood pressure in patients with primary open-angle glaucoma.

PURPOSE: Abnormal autoregulation of optic nerve head blood flow (ONHBF) has been postulated to play an important role in primary open-angle glaucoma (POAG). We used laser Doppler flowmetry (LDF) to estimate quantitatively the ONHBF and compared ONHBF autoregulation between glaucoma patients and healthy controls during isometric exercise. METHODS: Forty patients with POAG and 40 healthy age- and sex-matched subjects underwent three periods of isometric exercise, each consisting of 2 min of handgripping. Optic nerve head blood flow (ONHBF) was measured continuously using LDF. Systemic blood pressure, intraocular pressure and ocular perfusion pressure were assessed in all participants. RESULTS: Isometric exercise was associated with an increase in ocular perfusion pressure during all handgripping periods in both groups (p < 0.001). However, there was no change in ONHBF in either group. Three of the glaucoma patients and two of the healthy subjects showed a consistent 10% decrease in blood flow during isometric exercise, in spite of an increase in their blood pressure. This difference between groups was not significant (p = 0.61). Four other glaucoma subjects showed a consistent increase in blood flow of more than 10% during isometric exercise, whereas this was not seen in healthy subjects (p = 0.035). CONCLUSION: This study suggests that abnormal ONHBF autoregulation is more often seen in patients with POAG than healthy control subjects. The relationship to the glaucoma disease process is currently unknown and requires further investigation.

Optic nerve head morphology in primary open-angle glaucoma and nonarteritic anterior ischaemic optic neuropathy measured with spectral domain optical coherence tomography.

PURPOSE: Optic nerve head (ONH) parameters as well as circumpapillary retinal nerve fibre layer (RNFL) thickness values measured with two different spectral domain optical coherence tomography (SD-OCT) machines (Spectralis® and Cirrus® OCT) have been compared between two patient groups, primary open-angle glaucoma (POAG), nonarteritic anterior ischaemic optic neuropathy (NAION) and healthy controls. A comparison of the performance of the two OCT machines was made. METHODS: Twenty healthy controls, 20 POAG and 20 NAION patients with comparable visual field defects were included. Comparison between groups was made using anova and post hoc t-tests. To evaluate the diagnostic power of OCT to differentiate POAG from NAION, a stepwise linear regression analysis of the rim-RNFL correlation with adjusting covariates (optic disc area and age) was performed. Based on the regression formula, the area under the receiver operator characteristic (AUROC) was calculated. RESULTS: Both glaucoma and NAION patients showed significantly smaller global RNFL thickness values compared to healthy subjects in t-tests (p < 0.001), while only patients with glaucoma showed significantly smaller global ONH parameters for both devices compared to healthy subjects (p < 0.001). Correlation between global ONH parameters was highly statistically significant (r = 0.93), whereas in t-test a statistically significant difference between the two machines was detected (p < 0.001). Area under the receiver operator characteristic revealed a similarly good discrimination between glaucoma and NAION for Spectralis® (0.980) and Cirrus® OCT (0.945). CONCLUSION: NAION patients have similar RNFL thickness values as do glaucomatous eyes, whereas ONH parameters in NAION eyes were similar to those seen in healthy controls. This difference might help discriminating between these two different disease conditions in a chronic disease stadium, and in this regard, none of the two OCT machines performed better.

A Functional Regression Model of the Retinal Nerve Fiber Layer Thickness in Healthy Subjects.

PURPOSE: A new functional regression model is presented to explain the intersubject variability of the circumpapillary retinal nerve fiber layer (RNFL) thickness in healthy subjects. METHODS: To evaluate the functional regression approach we used data from 202 healthy volunteers, divided equally into training samples (TS) and validation samples (VS). Covariates included RNFL, fovea distance, fovea angle, optic disk ratio, orientation and area provided by Fourier-domain-optical coherence tomography, age, and refractive error. Root mean square errors (RMSE) were calculated for each of the 256 sectors and for the 12 clock-hour sectors in the TS and VS and were compared to the RMSE of the previous model and the standard deviation of the raw data. RESULTS: With the functional regression approach, we were able to explain on average 27.4% of the variation in the TS and 25.1% of the variation in the VS. The new model performed better compared to a multivariate linear regression model. It performed best in the superior-temporal and inferior-temporal clock-hour sectors where the percentage of RMSE reduction ranged between 26.3% and 44.1% for the TS and between 20.6% and 35.4% for the VS. CONCLUSIONS: The new functional regression approach improves on the multivariate linear regression model and allows an even larger reduction of the amount of intersubject variability, while at the same time using a substantially smaller number of parameters to be estimated. TRANSLATIONAL RELEVANCE: The demonstrated reduction of interindividual variation is expected to translate into an improved diagnostic separation between healthy and glaucomatous subjects, but this remains to be demonstrated in further studies.

Influence of disc-fovea angle and retinal blood vessels on interindividual variability of circumpapillary retinal nerve fibre layer.

BACKGROUND: To assess whether intersubject variability of circumpapillary retinal nerve fibre layer (RNFL) thickness in healthy subjects acquired with spectral domain optical coherence tomography (SD-OCT) can be reduced by considering the disc-fovea angle (DFA), either alone or together with a compensation based on retinal blood vessel distribution (RVD). METHODS: 106 healthy volunteers underwent SD-OCT examination centred on the optic disc (OD) and on the macula. OD contours and foveal positions were automatically calculated. RVD at 3.4 mm diameter circle was manually assessed. We made two approaches to reduce interindividual variability in RNFL values using compensation processes; RVD compensation: RNFL thickness values were compensated according to RVD variation (RNFLRVD) and DFA compensation: we shifted the RNFL thickness measurements according to the DFA (RNFLDFA). Coefficient of variance (CoV) was calculated in 12 clock hour sectors for original RNFL (RNFLo), RNFLDFA, RNFLRVD and RNFL with both compensation methods (RNFLDFA-RVD). RESULTS: Compared with the mean CoV of RNFLO, mean CoV of RNFLDFA, RNFLRVD and RNFLDFA-RVD was changed by -0.71% (p>0.05), -9.51% (p<0.001) and -7.55% (p=0.001), respectively. When compared with RNFLDFA, RNFL DFA-RVD significantly reduced the mean CoV by -6.69% (p=0.001), while compared with RNFLRVD, RNFL DFA-RVD did not significantly increase the mean CoV (+2.20%), (p>0.05). CONCLUSIONS: Although reaching an improvement in some sectors, rotation of RNFL measurements according to the DFA on average does not reduce intersubject variability of RNFL. However, adjusting for RVD reduced the variance significantly. The results reinforce our work in assessing RVD as an important anatomical factor responsible for intersubject variability in RNFL measurements.

Multivariate Model of the Intersubject Variability of the Retinal Nerve Fiber Layer Thickness in Healthy Subjects.

PURPOSE: We present and validate a multivariate model that partially compensates for retinal nerve fiber layer (RNFL) intersubject variability. METHODS: A total of 202 healthy volunteers randomly attributed to a training (TS) and a validation (VS) sample underwent complete ophthalmic examination, including Fourier-domain optical coherence tomography (FD-OCT). We acquired FD-OCT data centered at the optic disc (OD) and the macula. Two-dimensional (2D) projection images were computed and registered, to determine the distance between fovea and OD centers (FD) and their respective angle (FA). Retinal vessels were automatically segmented in the projection images and used to calculate the circumpapillary retinal vessel density (RVD) profile. Using the TS, a multivariate model was calculated for each of 256 sectors of the RNFL, including OD ratio, orientation and area, RVD, FD, FA, age, and refractive error. Model selection was based on Akaike Information Criteria. The compensation effect was determined for 12 clock hour sectors, comparing the coefficients of variation (CoV) of measured and model-compensated RNFL thicknesses. The model then was applied to the VS, and CoV was calculated. RESULTS: The R value for the multivariate model was, on average 0.57 (max = 0.68). Compensation reduced the CoV on average by 18%, both for the TS and VS (up to 23% and 29%), respectively. CONCLUSIONS: We have developed and validated a comprehensive multivariate model that may be used to create a narrower range of normative RNFL data, which could improve diagnostic separation between early glaucoma and healthy subjects. This, however, remains to be demonstrated in future studies.

Compensation for retinal vessel density reduces the variation of circumpapillary RNFL in healthy subjects.

This work intends to assess circumpapillary retinal vessel density (RVD) at a 3.46 mm diameter circle and correlate it with circumpapillary retinal nerve fiber layer (RNFL) thickness measured with Fourier-Domain Optical Coherence Tomography. Furthermore, it aims to evaluate the reduction of intersubject variability of RNFL when considering RVD as a source of information for RNFL distribution. For that, 106 healthy subjects underwent circumpapillary RNFL measurement. Using the scanning laser ophthalmoscope fundus image, thickness and position of retinal vessels were assessed and integrated in a 256-sector RVD profile. The relationship between local RVD value and local RNFL thickness was modeled by linear regression. RNFL was then compensated for RVD variation by regression formulas. A strong statistically significant intrasubject correlation was found for all subjects between RVD and RNFL profiles (mean R = 0.769). In the intersubject regression analysis, 247 of 256 RNFL sectors showed a statistically significant positive correlation with RVD (mean R = 0.423). RVD compensation of RNFL resulted in a relative reduction of up to 20% of the intersubject variance. In conclusion, RVD in a 3.46 mm circle has a clinically relevant influence on the RNFL distribution. RVD may be used to develop more individualized normative values for RNFL measurement, which might improve early diagnosis of glaucoma.

Retinal Blood Vessel Distribution Correlates With the Peripapillary Retinal Nerve Fiber Layer Thickness Profile as Measured With GDx VCC and ECC.

PURPOSE: Aim of the present study was to evaluate whether there is a correlation between retinal blood vessel density (RVD) and the peripapillary retinal nerve fiber layer (RNFL) thickness profile. METHODS: RNFL thickness of 106 healthy subjects was measured using scanning laser polarimetry, GDx variable corneal compensation (VCC), and GDx enhanced corneal compensation (ECC). A proprietary software was developed in MATLAB to measure the peripapillary retinal vessels using scanning laser ophthalmoscopy fundus images, centered on the optic disc measured by Cirrus spectral domain optical coherence tomography. The individual retinal vessel positions and thickness values were integrated in a 64-sector RVD profile and intrasubject and intersubject correlations were calculated. RESULTS: The mean R value±SD for intrasubject correlation between RVD and RNFL thickness measured with GDx VCC and GDx ECC was 0.714±0.157 and 0.629±0.140, with 105 of 106 subjects presenting significant correlations. In the intersubject linear regression analysis for GDx VCC, 33 of 64 (52%) sectors presented a significant Pearson correlation coefficient between RNFL thickness and RVD values, with a mean R value of 0.187±0.135 (P<0.05). CONCLUSIONS: Peripapillary RNFL thickness profiles correlate with the RVD over 50% of the sectors and might explain up to 26% of the interindividual variance of the peripapillary RNFL thickness values as measured with GDx VCC. To our opinion, taking into account RVD might reduce interindividual variation in peripapillary RNFL thickness profiles measured with scanning laser polarimetry.

Correlation between retinal vessel density profile and circumpapillary RNFL thickness measured with Fourier-domain optical coherence tomography.

AIM: To assess circumpapillary retinal vessel density (RVD) profiles and correlate them with retinal nerve fibre layer (RNFL) thickness measured by Fourier domain optical coherence tomography (FD-OCT). METHODS: RNFL thickness of 106 healthy volunteers was measured using Cirrus FD-OCT. A proprietary software was developed in MATLAB to assess the thickness and position of circumpapillary retinal vessels using the scanning laser ophthalmoscopy fundus image, centred on the optic disc. The individual retinal vessel positions and thickness values were integrated in a 256-sector RVD profile, and intrasubject and intersubject correlations were calculated. RESULTS: The mean value ± SD for intrasubject correlation between RVD and RNFL was 0.5349 ± 0.1639, with 101 of 106 subjects presenting significant correlation (p<0.05). 181 (out of 256) sectors presented a significant correlation between RVD and RNFL, with a mean value ± SD of 0.2600 ± 0.1140 (p<0.05). CONCLUSIONS: Using our model of the circumpapillary retinal vessel distribution, 70% of the RNFL thickness is influenced by RVD. On average, 7% of the interindividual variance of the RNFL thickness may be explained by RVD. A normative database that takes into account the circumpapillary blood vessels might slightly improve the diagnostic power of RNFL measurement.

A double-masked randomized crossover study comparing the effect of latanoprost/timolol and brimonidine/timolol fixed combination on intraocular pressure and ocular blood flow in patients with primary open-angle glaucoma or ocular hypertension.

PURPOSE: Ocular blood flow dysregulation has been implicated in the pathogenesis of glaucoma. Whereas the effect of single antiglaucoma substances on ocular blood flow has been addressed in various experiments, evidence for fixed combinations is sparse. In the present study, we set out to compare the effects of latanoprost 0.005%/timolol 0.5% (LT) fixed combination and brimonidine 0.2%/timolol 0.5% (BT) fixed combination on intraocular pressure (IOP) and ocular blood flow. METHODS: In the present study, which followed a randomized, double-masked 2-way crossover design, 16 patients with primary open-angle glaucoma and 2 patients with ocular hypertension were included. The patients underwent a 6-week treatment with LT and a 6-week treatment with BT after a washout for previous antiglaucoma medication. Optic nerve head blood flow (ONHBF) was measured using laser Doppler flowmetry; retrobulbar flow velocities were measured using color Doppler imaging in the ophthalmic artery, the central retinal artery, and the posterior ciliary arteries. IOP was measured at 8 AM, 12 PM, and 4 PM. RESULTS: The mean baseline IOP was 25.3±2.8 mmHg. Both drugs were equally effective in reducing IOP (LT: -35.0%±10.0%; BT: -33.6%±8.8%, P=0.463 between groups). In addition, no difference in ocular perfusion pressure was observed between the 2 treatment groups (P=0.1, between groups). Neither LT nor BT altered ONHBF (P=0.4, baseline vs. treatment) and no effect on flow velocities in the retrobulbar vessels was seen with either of the 2 treatments. CONCLUSIONS: In the present study, a 6-week treatment with LT or BT was equally effective in reducing IOP. In addition, none of the administered drugs induced a significant effect on ocular blood flow parameters.

Comparison of optic disc parameters using spectral domain cirrus high-definition optical coherence tomography and confocal scanning laser ophthalmoscopy in normal eyes.

PURPOSE: To compare Cirrus HD - optical coherence tomography (HD-OCT) with confocal scanning laser ophthalmoscopy (HRT 3) for analysis of optic disc parameters in healthy eyes. METHODS: In 126 subjects, cup volume (CV), vertical cup/disc ratio (CDR), neuroretinal rim area (NRA), cup area (CA) and optic disc area (ODA) were measured with the Cirrus HD-OCT and HRT 3. These optic disc parameters were chosen for statistical analysis because they can be analysed in both OCT and HRT 3 and they are widely used parameters for glaucoma assessment. RESULTS: Mean values and significances of paired t-tests for OCT and HRT were for CV: 0.099 ± 0.11 versus 0.082 ± 0.10 (p < 0.001), CA: 0.42 ± 0.31 versus 0.39 ± 0.31 (p < 0.001), CDR: 0.36 ± 0.17 versus 0.27 ± 0.21 (p < 0.001). NRA and ODA were not significantly different between instruments. The Pearson coefficients were 0.905 (CV), 0.824 (CA), 0.734 (CDR), 0.295 (NRA) and 0.378 (ODA). CONCLUSION: To our interpretation, the delineation of the optic disc border is error-prone with both instruments and all parameters directly depending on it are thus poorly correlated. However, the determination of the optic disc excavation (CV and CA) appears comparable taking into account a small systematic difference between instruments.

Effect of regular smoking on flicker induced retinal vasodilatation in healthy subjects.

BACKGROUND: Habitual smoking is a risk factor for a variety of vascular diseases, including ocular pathologies. In the current study, we set out to investigate whether the regulation of retinal vascular tone is impaired in habitual smokers. For this purpose, vascular reactivity was tested during flicker light induced vasodilatation in smokers and in a non-smoking control group. METHODS: In this prospective, balanced, parallel group study 24 chronic smokers (28.1 ± 3.3 years) and 24 age-matched never-smoking volunteers (28.2 ± 4.0 years) were included. Flicker induced vasodilatation was measured in major retinal arteries and veins using a retinal vessel analyzer and flicker induced changes in retinal blood velocities were assessed in retinal veins by laser Doppler velocimetry. Three flicker periods of 60s were scheduled. Blood cotinine concentration was determined and a Fagerstrom questionnaire was performed to evaluate nicotine dependency. RESULTS: In non-smoking subjects, stimulation with flicker light increased retinal venous diameter by +7.7 ± 3.1%, +6.9 ± 2.9% and +7.1 ± 2.8% during the three flicker periods, respectively. Flicker induced vasodilatation in veins was significantly diminished in chronic smokers (+4.9 ± 2.4%, +6.3 ± 3.1% and +5.7 ± 3.4%, ANOVA between groups, p=0.032) as compared to the non-smoking control group. Calculated retinal blood flow in the measured veins increased by a maximum of +54 ± 21%, +43 ± 18% and +46 ± 19% during the three stimulation periods in the non-smoking subjects, respectively. The flicker induced increase in retinal blood flow as assessed in the veins was significantly reduced in chronic smokers as compared to the non-smoking control group (+19 ± 16%, +26 ± 14%, +24 ± 13%, ANOVA between groups, p=0.013). In retinal arteries, flicker stimulation increased retinal arterial diameters by 5.2 ± 3.8%, 5.8 ± 4.8% and 5.5 ± 5.6% during the three flicker periods in the non-smoking group. In smokers, the flicker induced arterial vasodilatation was not significantly different compared to non-smokers (4.6 ± 4.1%, 3.8 ± 3.7% and 4.8 ± 3.4%, ANOVA between groups, p=0.4). CONCLUSION: Our data indicate that the flicker induced hemodynamic response of retinal veins is reduced in chronic smokers as compared to age matched healthy volunteers. This supports the hypothesis that chronic smoking leads to vascular dysfunction in the eye.