Retinal vessel oxygen saturation in healthy subjects and early branch retinal vein occlusion

AIM: To measure the retinal oxygen saturation in healthy subjects and early branch retinal vein occlusion (BRVO) in Chinese population. METHODS: The retinal vessel oxygen saturation of the healthy subjects and BRVO patients were measured by a noninvasive retinal oximeter (Oxymap ehf., Reykjavik, Iceland). RESULTS: The study included 22 patients with unilateral BRVO (mean age: 55.1±8.8y) in the study group and 91 healthy participants (mean age: 37.5±14.0y) in the control group. In the healthy individuals, mean arterial and venous oxygen saturation were significantly (P<0.001) higher in the superior nasal quadrant (98.5%±10.1% and 57.3%±8.7%, respectively) than in the inferior nasal quadrant (94.2%±9.0% and 54.1%±9.6%, respectively), followed by the superior temporal quadrant (89.1%±10.1% and 51.9%±8.9%, respectively) and the inferior temporal quadrant (86.4%±9.4% and 46.6%±9.6%, respectively). In patients with ischemic BRVO, arterial oxymetric values were significantly higher and venous measurements significantly lower for the affected vessel (107.5%±9.7% and 46.4%±14.2%, respectively) than the unaffected vessel in the same eye (99.2%±12.2% and 55.5%±7.9%, respectively) and as compared to the vessel in the unaffected fellow eye (93.1%±6.9% and 55.7%±6.8%) (P=0.005 and P=0.02, respectively). In the patients with non-ischemic BRVO, mean venous oxygen saturation was lower in the affected vein (39.8%±12.2%) than in the unaffected vessels of the same eye (50.8%±10.5%) and in the fellow eye (58.21%±5.7%) (P=0.03). Mean arterial oxygen saturation did not differ significantly (P=0.42) between all three groups. CONCLUSION: In patients with BRVO, the venous oxygen saturation in the affected vessels is decreased potentially due to decreased blood velocity and flow. Interestingly, the arterial oxygen saturation in eyes with ischemic BRVO is increased in the affected arteries.     

Phenylephrine 5% added to Tropicamide 0.5% eye drops does not influence retinal oxygen saturation values or retinal vessel diameter in glaucoma patients

Purpose: To test whether adding topical phenylephrine 5% to tropicamide 0.5% eye drops in the protocol for pupil dilation affects the retinal vessel oximeter measurements in patients with glaucoma. To test whether phenylephrine 5% has an influence as a vasoconstrictor on the retinal vessel width and can improve the proportion of high‐quality retinal images in patients with glaucoma. Methods: Retinal images of 66 patients with chronic open‐angle glaucoma were obtained before and after the administration of phenylephrine 5% eye drops to patients already dilated with tropicamide 0.5% with the Oxymap Retinal Oximeter (Oxymap ehf, Reykjavik, Iceland). Specialized software, Oxymap Analyzer, analysed the images and measured the oxygen saturation and vessel diameter. Oxygen saturation was measured in first‐ and second‐degree vessels. A Mann–Whitney U‐test was used to compare both groups. Quality of the images was assessed, and a Fisher’s exact test was used to compare the proportion of high‐ and poor‐quality images. Results: There was no significant difference in arterial and venous oxygen saturation in patients with glaucoma whether dilated by tropicamide alone or a combination of tropicamide and phenylephrine (97 ± 6% versus 96 ± 5%, p = 0.88 for arterial saturation and 66 ± 6% versus 67 ± 6%, p = 0.78 for venous saturation, n = 27). There was no significant difference in vessel diameter between both conditions for the different vessels (p = 0.61 for arterial saturation and p = 0.51 for venous saturation, n = 27). The proportion of high‐quality images was significantly higher after the combination regimen compared with tropicamide only (p = 0.0001). Conclusion: The addition of topical phenylephrine 5% after tropicamide 0.5% improved the proportion of high‐quality retinal oximetry images without influencing the retinal oxygen saturation values or the retinal vessel diameter in patients with glaucoma.     

The effect of pars plan vitrectomy on oxygen saturation in retinal vessels – a pilot study

Purpose: To determine the effect of pars plana vitrectomy (PPV) on oxygen saturation in retinal vessels. Methods: We performed a prospective consecutive interventional case series of 20 eyes of 20 patients with macular hole or epiretinal membrane. We performed automatic retinal oximetry (Oxymap Inc., Reykjavik, Iceland) in each patient 24 hr prior to and 45 days (range 42–49) after PPV (classic 20G or sutureless 23G). We analysed oxygen saturations in retinal arteries and veins. Vessel segments of first or second degree were selected. The same segment was analysed before and after PPV. Oximetry data were compared by paired two‐tailed t‐test. Results: Pars plana vitrectomy did not alter arterial haemoglobin saturation with oxygen (98 ± 2% prior to the surgery and 98 ± 3% after the procedure, p = 0.549). The mean venous haemoglobin saturation with oxygen increased after vitrectomy from 63 ± 10% to 66 ± 8% (p = 0.012). Conclusions: Oxygen saturation is higher in retinal veins after pars plana vitrectomy. Further studies are needed to unveil the mechanism of how vitrectomy affects oxygen metabolism in the retina.     

Reactivity of retinal blood flow to 100% oxygen breathing after lipopolysaccharide administration in healthy subjects

Administration of low doses of Escherichia coli endotoxin (LPS) to humans enables the study of inflammatory mechanisms. The purpose of the present study was to investigate the retinal vascular reactivity after LPS infusion. In a randomized placebo-controlled cross-over study, 18 healthy male volunteers received 20IU/kg LPS or placebo as an intravenous bolus infusion. Outcome parameters were measured at baseline and 4h after LPS/placebo administration. At baseline and at 4h after administration a short period of 100% oxygen inhalation was used to assess retinal vasoreactivity to this stimulus. Perimacular white blood cell velocity, density and flux were assessed with the blue-field entoptic technique, retinal branch arterial and venous diameters were measured with a retinal vessel analyzer and red blood cell velocity in retinal branch veins was measured with laser Doppler velocimetry. LPS is associated with peripheral blood leukocytosis and increased white blood cell density in ocular microvessels (p<0.001). In addition, retinal arterial (p=0.02) and venous (p<0.01) diameters were increased. All retinal hemodynamic parameters showed a decrease during 100% oxygen breathing. This decrease was significantly blunted by LPS for all retinal outcome parameters except venous diameter (p=0.04 for white blood cell velocity, p=0.0002 for white blood cell density, p<0.0001 for white blood cell flux, p=0.01 for arterial diameter, p=0.02 for red blood cell velocity and p=0.006 for red blood cell flux). These data indicate that LPS-induced inflammation induces vascular dysregulation in the retina. This may provide a link between inflammation and vascular dysregulation. Further studies are warranted to investigate whether this model may be suitable to study inflammation induced vascular dysregulation in the eye.     

Long‐term results of the effect of intravitreal ranibizumab on the retinal arteriolar diameter in patients with neovascular age‐related macular degeneration

Purpose: To study the effect of intravitreal (IVT) ranibizumab on the retinal arteriolar diameter in patients with neovascular age‐related macular degeneration (AMD). Methods: Ten eyes of 10 patients with previously untreated neovascular AMD were included. All eyes had three monthly IVT injections of ranibizumab and then were retreated as needed, based on visual acuity and optical coherence tomography (OCT) criteria. The diameter of the retinal arterioles was measured in vivo with a retinal vessel analyser (RVA) before the first IVT injection, 7 and 30 days after the first, the second and the third injection, and at month 12 of follow‐up. Results: A significant vasoconstriction of the retinal arterioles was observed following each one of the first three IVT injections of ranibizumab. Thirty days following the first, second and third injection, there was a mean decrease of 8.4 ± 3.2%, 11.9 ± 4.5% and 18.5 ± 7.2%, respectively, of the retinal arteriolar diameter compared with baseline (p < 0.01). At month 12, the vasoconstriction was still present with a mean decrease of 19.1 ± 8.3% of the retinal arteriolar diameter compared with baseline (p < 0.01). Median number of ranibizumab injections was 4 (range 3–10). There was no correlation between the number of injections and percentage diameter decrease at month 12 (r = ?0.54, p > 0.1). There was no significant change in mean arterial pressure (MAP) during the period of follow‐up (p > 0.05). Conclusions: These results suggest that IVT ranibizumab induces sustained retinal arteriolar vasoconstriction in eyes with neovascular AMD.     

Intraocular pressure and ocular hemodynamics in patients with primary open‐angle glaucoma treated with the combination of morning dosing of bimatoprost and dorzolamide hydrochloride

Acta Ophthalmol. 2011: 89: e57–e63

Abstract.

Aims: This prospective, multicenter, single‐masked study evaluated the additive effect of dorzolamide hydrochloride 2% on the diurnal intraocular pressure (IOP) curve and retinal and retrobulbar hemodynamics in patients with primary open‐angle glaucoma (POAG) treated with morning‐dosed bimatoprost 0.03%. Methods: Eighty‐nine patients (aged, 60.7 ± 11.8 years, range 33–80; 68 women) with POAG received bimatoprost dosed once in the morning for 1 month, after which dorzolamide was added twice daily for 2 months. IOP (Goldmann) and arterial blood pressure (BP) and diurnal ocular perfusion pressures (OPP) were measured every 2 hr for 24 hr. Heidelberg retina flowmetry of the retinal microcirculation was recorded four times daily in 64 patients and colour Doppler imaging of the ophthalmic and central retinal arteries was recorded five times daily in 25 patients. All measurements were taken after the two phases of treatment and compared using anova analysis with Bonferroni adjustment. Results: Mean baseline IOP was 16.5 ± 3.4 mmHg. Mean diurnal IOP with dorzolamide adjunctive therapy (12.9 ± 2.1 mmHg) was significantly lower compared to mean IOP with bimatoprost monotherapy (13.6 ± 2.2 mmHg) (p = 0.03). Adjunctive dorzolamide therapy significantly decreased vascular resistance in the ophthalmic artery (p = 0.02). Mean diastolic BP and OPP were significantly lower after adjunctive therapy. There were no changes in retinal microcirculation between the two phases of treatment. Conclusions: Adjunctive dorzolamide therapy to morning‐dosed bimatoprost 0.03% reduced diurnal IOP and vascular resistance in the ophthalmic artery but did not alter retinal circulation in this group of patients with POAG.     

Oximetry in glaucoma: correlation of metabolic change with structural and functional damage

Purpose: To determine whether retinal vessel oxygen saturation in patients with glaucoma is associated with structural optic disc and retinal nerve fibre layer (RNFL) changes and visual field (VF) defects. Methods: Fifty‐nine patients with confirmed glaucoma were recruited at University Hospitals Leuven. Retinal oxygen saturation in patients with glaucoma was measured with a noninvasive spectrophotometric retinal oximeter (Oxymap ehf, Reykjavik, Iceland). VF and Heidelberg retinal tomographies (HRTs) were performed on the same day. Statistical analysis was performed using Student’s t‐test and Pearson’s or Spearman correlation coefficient. Results: The mean oxygen saturation in venules was higher in patients with severe VF defects compared to those patients with mild VF defects (69 ± 3% versus 65 ± 6% respectively; p = 0.0003; n = 59). Accordingly, the arteriovenous (AV) difference in oxygen saturation was lower in patients with worse VF compared to those with better VF (29 ± 3% versus 33 ± 6% respectively; p = 0.002). The oxygen saturation in venules correlated with the VF mean defects (r = ?0.42; p = 0.001; n = 59) as well as with the structural HRT parameters rim area and RNFL thickness (r = ?0.39; p = 0.008 and r = ?0.26; p = 0.05 respectively; n = 53). The AV difference decreased significantly as the VF defect worsened (r = 0.38; p = 0.003), as the rim area diminished (r = 0.29; p = 0.03) and as the RNFL thickness decreased (r = 0.27; p = 0.05). No correlation was found between the oxygen saturation in retinal arterioles and either of these parameters. Conclusion: Severe glaucomatous damage is associated with increased oxygen saturation in retinal venules and decreased AV difference in oxygen saturation. These data suggest that in eyes with severe glaucomatous damage, reduced retinal oxygen consumption is consistent with tissue loss.     

The effect of caffeine on retinal vessel diameter in young healthy subjects

Purpose: To investigate the effect of caffeine on retinal vessel diameter before and during flicker light stimulation in young healthy subjects. Methods: Seventeen healthy subjects (mean age: 29.6 ± 3.73 years, range: 22–35 years) were included in this study. The diameter of retinal vessels was measured continuously with the retinal vessel analyzer (RVA) before and 1 hr after 200 mg oral caffeine intake. After baseline assessment, a green luminance flicker of 20‐second duration was applied to stimulate retinal activity. The diameter of a segment of an arteriole and of a venule were measured during stimulation and 80 second after cessation of the stimulus. Flicker stimulation and 80‐second measurement interval were carried out three times. Blood pressure parameters, systemic mean arterial pressure (MAP), ocular perfusion pressure (OPP) and intraocular pressure (IOP) were obtained before and after oral caffeine intake. Results: The mean diameter of the arterioles at baseline before caffeine intake was 123.30 ± 14.0 μm (arithmetic mean ± standard deviation) and after caffeine 117.30 ± 13.0 μm which was significantly different (p = 0.004). The mean diameter of the venules at baseline before caffeine intake was 147.60 ± 19.5 μm and after caffeine 137.73 ± 19.9 μm which was significantly different (p = 0.005). The mean diameter of the arterioles during flicker light stimulation before caffeine intake was 126.65 ± 13.24 μm and after caffeine intake 121.59 ± 12.12 μm (p = 0.012). The mean diameter of the venules during flicker light stimulation before caffeine intake was 151.87 ± 18.63 μm and after caffeine intake was 145.14 ± 19.82 μm (p = 0.027). The flicker response of the arterioles increased from 2.8% before caffeine to 3.8% after caffeine intake (p = 0.010). The flicker response of the venules increased from 3.4% before caffeine to 5.5% after caffeine intake (p = 0.0001). Baseline diameters and diameters during flicker light stimulation after caffeine intake showed a significant negative correlation to the MAP for the arterioles (baseline: r = ?0.338, p = 0.049 and flicker: r = ?0.345, p = 0.046) and the venules (baseline: r = ?0.496, p = 0.003 and flicker: r = ?0.479, p = 0.004). Conclusions: The present study showed a significant vasoconstrictory response of the retinal vessels 1 hr after caffeine intake in young healthy subjects. Retinal vessel diameter changes were negatively correlated with MAP after caffeine consumption. These effects seem to be elicited by an autoregulatory response of the retinal vessels to the increased blood pressure changes after caffeine.     

Reproducibility of retinal vessel oxygen saturation measurements in healthy young subjects

Purpose: An adequate oxygenation and perfusion is essential for the function of the inner retina. Recently, several techniques for the measurement of retinal oxygen saturation became available. We set out to evaluate reproducibility of the measurements using a modified Retinal Vessel Analyzer. Methods: A total of 20 healthy female and male subjects aged between 18 and 35 years (22.9 ± 3.9; mean ± SD) were included. The measurement of retinal oxygen saturation with the retinal oximeter employed in this study is based on optical reflectometry using the different absorption characteristics of oxygenated and deoxygenated haemoglobin. The intraclass correlation coefficients and the coefficients of variation (CV) for test–retest, short‐term as well as day‐to‐day measurements were calculated. Results: The intraclass correlation coefficients were between 0.91 and 0.94 for retinal branch arteries and between 0.84 and 0.88 for retinal branch veins. In retinal arteries, we calculated a test–retest CV of 3.24 ± 3.18% for oxygen saturation measurements. In retinal veins, data were slightly less reproducible with a CV of 4.92 ± 3.57%. Short‐term reproducibility of both measurement cycles on each study day was in the same range (CV in retinal arteries: 2.91 ± 2.42% and CV in retinal veins: 4.76 ± 3.14%). The day‐to‐day coefficient of variation was slightly higher (CV in retinal arteries: 3.97 ± 2.87% and CV in retinal veins: 6.18 ± 3.36%). Conclusion: The reproducibility of haemoglobin oxygen saturation measurements using the retinal oximeter is acceptable. Further studies on the validity of the obtained results are, however, required.     

Retinal blood flow indices in patients infected with human immunodeficiency virus.

AIMS/BACKGROUND: Abnormal blood flow dynamics are believed to contribute to the development of retinal microvascular disease in patients infected with human immunodeficiency virus (HIV). In this study, the scanning laser ophthalmoscope (SLO) was used, combined with fluorescein angiography, to measure retinal blood flow indices in HIV seropositive patients. METHODS: Arteriovenous passage time (AVP) and perifoveal capillary blood flow velocity (CFV) were measured in 23 HIV infected patients and 23 control subjects with SLO fluorescein angiography. RESULTS: No significant difference in AVP was found between the two groups. However, CFV was significantly reduced in HIV infected patients (p = 0.013). CONCLUSION: Patients infected with HIV show abnormal haemodynamics at the level of the perifoveal capillaries.     

Impaired retinal vasodilator responses in prediabetes and type 2 diabetes

Purpose: In diabetes, endothelial dysfunction and subsequent structural damage to blood vessels can lead to heart attacks, retinopathy and strokes. However, it is unclear whether prediabetic subjects exhibit microvascular dysfunction indicating early stages of arteriosclerosis and vascular risk. The purpose of this study was to examine whether retinal reactivity may be impaired early in the hyperglycaemic continuum and may be associated with markers of inflammation. Methods: Individuals with prediabetes (n = 22), type 2 diabetes (n = 25) and healthy age and body composition matched controls (n = 19) were studied. We used the Dynamic Vessel Analyzer to assess retinal vasoreactivity (percentage change in vessel diameter) during a flickering light stimulation. Fasting highly sensitive c‐reactive protein (hs‐CRP), a marker of inflammation, was measured in blood plasma. Results: Prediabetic and diabetic individuals had attenuated peak vasodilator and relative amplitude changes in retinal vein diameters to the flickering light stimulus compared with healthy controls (peak dilation: prediabetic subjects 3.3 ± 1.8%, diabetic subjects 3.3 ± 2.1% and controls 5.6 ± 2.6%, p = 0.001; relative amplitude: prediabetic subjects 4.3 ± 2.2%, diabetic subjects 5.0 ± 2.6% and control subjects 7.2 ± 3.2%, p = 0.003). Similar findings were observed in retinal arteries. Levels of hs‐CRP were not associated with either retinal vessel response parameters. Conclusion: Retinal reactivity was impaired in prediabetic and type 2 diabetic individuals in parallel with reduced insulin sensitivity but not associated with levels of hs‐CRP. Retinal vasoreactivity measurements may be a sensitive tool to assess early vascular risk.     

Calculation of central retinal artery diameters from non‐invasive ocular haemodynamic measurements in type 1 diabetes patients

Purpose: The aim of the study was to compare the diameter of the central retinal artery (CRA) between patients with diabetes mellitus and healthy subjects in vivo. CRA diameters were calculated from retinal haemodynamic parameters measured with noninvasive measurement techniques. Methods: Sixteen patients with type 1 diabetes with no or mild diabetic retinopathy and 16 age‐matched healthy controls were included in this study. Total retinal blood flow was assessed by combining bidirectional laser Doppler velocimetry in all veins entering the optic disc with measurements of retinal vessel diameters using a Dynamic Vessel Analyser. Blood flow velocity in the CRA was measured with colour Doppler imaging (CDI). The diameter of the CRA in the optic nerve was then calculated for each subject using the individual ocular haemodynamic data. Results: Calculated CRA diameters were significantly larger in patients with diabetes (180 ± 13 μm) compared with healthy controls (166 ± 10 μm, p = 0.001). No significant differences were found in retinal blood flow, retinal artery or vein diameters or mean flow velocity of the CRA. Conclusion: The data of the present study show increased calculated CRA diameter in patients with type 1 diabetes with no or mild retinopathy. Blood flow velocity measurements in retrobulbar vessels using CDI need to be interpreted with caution in terms of retinal blood flow, because no information about vessel diameters is obtained by this technique.     

Central serous chorioretinopathy shows reduced retinal flow circulation in retinal function imaging (RFI)

Purpose: To assess retinal blood flow in patients with central serous chorioretinopathy (CSR). Methods: The hospital‐based observational comparative study included a study group with 12 patients (age: 45 ± 13 years) with an acute onset of CSR and a control group of 12 subjects matched for age and gender with the study group. The diagnosis was substantiated by fluorescein angiography and optical coherence tomography. All study participants underwent measurement of retinal blood perfusion using the retinal function imager (RFI). Results: The retinal blood flow velocity in the retinal veins was significantly lower in the study group than in the control group (2.76 ± 0.53 mm/s versus 3.33 ± 0.76 mm/s; p = 0.03).The difference between the study group and control group was more marked for the larger retinal veins (2.87 ± 0.51 mm/s versus 3.47 ± 0.48 mm/s; p = 0.001) than for the smaller veins (2.69 ± 0.53 mm/s versus 3.42 ± 1.05 mm/s; p = 0.04). Both groups did not differ significantly in the data of the retinal arterial flow velocities. Conclusions: The data suggest an abnormal retinal venous blood flow regulation in patients with active CSR.     

Lack of effect of short‐term treatment with Amlodipine and Lisinopril on retinal autoregulation in normotensive patients with type 1 diabetes and mild diabetic retinopathy

Purpose: Diabetic retinopathy is characterized by morphological changes in the retina secondary to disturbances in retinal blood flow. It has been shown that antihypertensive treatment has a protective effect on the development of diabetic retinopathy, and evidence suggests that inhibitors of the renin–angiotensin system have a protective effect beyond the antihypertensive effect. The background for this additional effect is unknown but might be related to an effect on retinal autoregulation. Methods: In a double‐blinded, two‐way cross‐over study, 25 normotensive patients with type 1 diabetes (T1D) aged 20.6–33.9 (mean 27.9) with mild retinopathy were randomized to receive either 5 mg of the calcium channel blocker (CCB) amlodipine for 14 days followed by a washout period and treatment with 10 mg of the angiotensin converting enzyme (ACE) inhibitor lisinopril for another 14 days or the two treatments in the reverse order. Using a Dynamic Vessel Analyzer (DVA), the diameter response of retinal arterioles during an acute increase in the blood pressure induced by isometric exercise, during flicker stimulation and during both stimulus conditions simultaneously was studied before and during the two treatments periods. Results: Amlodipine and lisinopril induced a similar non‐significant decrease in the arterial blood pressure. At baseline, the arterial diameter decreased by 2.4 ± 0.9% (p = 0.004) during isometric exercise, increased by 2.2 ± 0.9% (p = 0.019) during flicker stimulation and increased by 1.8 ± 0.9% (p = 0.03) during the combined stimulus conditions. Neither of the antihypertensive drugs amlodipine (p = 0.76) or lisinopril (p = 0.11) changed the diameter response of retinal vessels significantly; however, the two treatments induced a different response in the veins during combined exercise and flicker (p = 0.021). Conclusions: Short‐term treatment with amlodipine and lisinopril had no significant effect on retinal autoregulation in young normotensive patients with T1D and mild retinopathy, and this lack of effect was similar for the two drugs. A possible normalizing effect of antihypertensive treatment on retinal autoregulation was not observed; however, it might take longer time to improve autoregulation than to reduce the arterial blood pressure.     

Functional and anatomical results after a single intravitreal Ozurdex injection in retinal vein occlusion: a 6‐month follow‐up – The SOLO study

Purpose:  To evaluate the efficacy of intravitreal dexamethasone implants in eyes with cystoid macular oedema (CME) secondary to branch retinal vein occlusion (BRVO) or central retinal vein occlusion (CRVO) in the clinical everyday practice, examine the effects of early retreatment and compare the results with the GENEVA study. Methods:  The charts of 102 patients (102 eyes) with CME secondary to BRVO (n = 54) or CRVO (n = 48) treated with Ozurdex at 8 centres were retrospectively reviewed. The patients were examined monthly over a 24‐week period. Slit‐lamp biomicroscopy, measurement of best‐corrected visual acuity (BCVA) and measurement of the central retinal thickness (CRT) with spectral‐domain optical coherence tomography (SD‐OCT) were performed at baseline and at every follow‐up examination. With progression of the disease (loss of one line or increased central retinal thickness (CRT) of 150 μm), a reinjection of Ozurdex or anti‐VEGF was offered. Additional supplementing sectorial or panretinal laser photocoagulation was considered based on the individual status of the retina. Results:  In the BRVO group, the median BCVA was 0.6 logMAR (Snellen equivalent of 0.25) at baseline and improved to 0.4 logMAR (Snellen equivalent of 0.40) after 4 weeks, 0.3 logMAR (Snellen equivalent of 0.50) after 8 weeks, 0.4 logMAR (Snellen equivalent of 0.40) after 12 weeks, 0.5 logMAR (Snellen equivalent of 0.32) after 16 weeks, 0.4 logMAR (Snellen equivalent of 0.40) after 20 weeks and 0.45 logMAR (Snellen equivalent of 0.35) after 24 weeks. The mean CRT was 559 ± (SD) 209 μm at baseline and it decreased to 335 ± 148 μm after 4 weeks, 316 ± 137 μm after 8 weeks, 369 ± 126 μm after 12 weeks, 407 ± 161 μm after 16 weeks, 399 ± 191 μm after 20 weeks and 419 ± 196 μm after 24 weeks. In the CRVO group, the median BCVA was 0.7 logMAR (Snellen equivalent of 0.20) at baseline and improved to 0.4 logMAR (Snellen equivalent of 0.40) after 4 weeks, 0.4 logMAR (Snellen equivalent of 0.40) after 8 weeks, 0.6 logMAR (Snellen equivalent of 0.25) after 12 weeks, 0.6 logMAR (Snellen equivalent of 0.25) after 16 weeks, 0.5 logMAR (Snellen equivalent of 0.32) after 20 weeks and 0.52 logMAR (Snellen equivalent of 0.30) after 24 weeks. The mean CRT at baseline was 740 ± 351 μm and it decreased to 419 ± 315 μm after 4 weeks, 352 ± 261 μm after 8 weeks, 455 ± 251 μm after 12 weeks, 497 ± 280 μm after 16 weeks, 468 ± 301 μm after 20 weeks and 395 ± 234 μm after 24 weeks. The BCVA improvement was statistically significantly better (p < 0.05) compared with baseline in both groups at every follow‐up visit. The mean CRT maintained significantly better when compared with baseline in both groups at all follow‐up visits. Early reinjection was indicated in BRVO in 40.7% after 17.5 ± 4.2 weeks and in CRVO in 50% after 17.68 ± 4.2. Six eyes (11%) with BRVO received a sectorial laser photocoagulation at a mean interval of 22 ± 5.0 weeks. Seven eyes (15%) with CRVO received a panretinal laser photocoagulation after a mean interval of 18 ± 7.0 weeks. The BCVA improvement and the mean CRT reduction were statistically significant (p < 0.05) compared with baseline in both groups at every follow‐up visit. Conclusions:  Dexamethasone intravitreal implant resulted in a significant improvement of the BCVA and reduction of CME in patients with BRVO or CRVO. Early retreatment after 16 weeks instead of 24 weeks, like in the GENEVA study, was indicated in 50% to stabilize the improved functional and anatomical results.     

Diagnostic compatibility of structural and haemodynamic parameters in open‐angle glaucoma patients

Purpose: Current evidence indicates that alteration in ocular blood flow may be relevant in open‐angle glaucoma (OAG) patients independent of intraocular pressure (IOP). Presently, the lack of an adequate methodology capable of assessing all vascular beds limits the clinical role of blood flow parameters in glaucoma management. We aimed to compare differences in retinal nerve fibre layer (RNFL) thickness and retrobulbar haemodynamics between OAG patients and healthy age‐matched control subjects. Methods: Sixty eyes of 30 OAG patients and 30 healthy age‐matched controls were enrolled into the prospective, randomized study. Retinal nerve fibre layer thickness was analysed by scanning laser polarimetry (SLP). Standard SLP parameters were determined, including: average temporal, superior, nasal, inferior thickness (TSNIT); superior and inferior averages; TSNIT standard deviation (TSNIT‐SD), and nerve fibre indicator (NFI). Retrobulbar haemodynamics were assessed using colour Doppler imaging (CDI). Peak systolic velocity (PSV), end‐diastolic velocity (EDV), pulsatility index (PI) and resistivity index (RI) in the ophthalmic artery (OA), central retinal artery (CRA) and short posterior ciliary artery (SPCA) were evaluated. Results: The RNFL in OAG patients was statistically significantly thinner compared with that in age‐matched controls: the NFI was 24.9 ± 10.24 in OAG patients and 16.13 ± 7.95 in healthy controls (p < 0.05). Statistically significant differences were observed: CRA PSV was 20.54 ± 7.84 cm/second in OAG subjects and 16.5 ± 6.19 cm/second in healthy controls (p = 0.0038); OA EDV was 8.99 ± 4.71 cm/second in OAG subjects and 5.93 ± 3.23 cm/second in healthy controls (p = 0.0048). Correlation analysis of NFI was in positive association with CRA EDV (r = 0.395; p < 0.05) and CRA PI (r = 0.403; p < 0.05) in OAG subjects, but no statistically significant association was seen in healthy controls. Conclusions: Statistically significant thinning of the RNFL in association with reduced retrobulbar blood flow velocities was observed in OAG patients. Combining ocular structural alterations with ocular circulation assessment may increase our ability to elucidate potential IOP‐independent glaucomatous risk factors.     

Investigation of blood flow regulation and oxygen saturation of the retinal vessels in primary open-angle glaucoma

Purpose

To examine the supply of oxygen to the retina in primary open-angle glaucoma (POAG).

Methods

Forty-one patients with primary open-angle glaucoma (mean age 64.1?±?12.9 years) and 40 healthy subjects (63.6?±?14.1 years) were included. Fundus images, centered at the optic disc, were taken using the Retinal Vessel Analyzer (RVA). The vessel diameters were calculated as central retinal artery (CRAE) and vein equivalent (CRVE) from diameter measurements in the peripapillary vessels. The oxygen saturation of the arteries and veins was investigated employing a two-wavelengths technique. After the measurement at baseline, the vascular response to flicker light exposure was measured.

Results

In glaucoma patients the mean oxygen saturation of the retinal veins at baseline was higher than in the healthy controls (64.36?±?7.11 vs. 59.78?±?8.47, p?=?0.01), whereas the mean arteriovenous oxygen saturation difference was lower (33.07?±?5.24 vs. 37.53?±?6.95, p?=?0.002). The arterial oxygen saturation as well as the arterial and venous diameters showed no difference between the groups. The increase of the CRVE during flicker light stimulation (3.72?±?3.29 % vs. 5.43?±?4.04, p?=?0.039), as well as the change of the venous oxygen saturation (2.08?±?3.74 % vs. 4.18?±?3.88 %, p?=?0.016) and the arteriovenous saturation difference (?2.1?±?3.31 % vs. ?4.43?±?3.6 %, p?=?0.003) were smaller in POAG patients than in the healthy group.

Conclusions

The reduction in the arteriovenous difference in oxygen saturation in POAG patients might show a decreased oxygen demand of the retina caused by the glaucomatous loss of neuroretinal tissue. The lower extent of the flicker light-induced change of the diameter of retinal veins and the venous oxygen saturation could indicate an impairment of blood flow regulation.