M. Reim

Retinal microcirculation in patients with diabetes mellitus: dynamic and morphological analysis of perifoveal capillary network.

The new scanning laser technique allows one to quantify the retinal microcirculation. A digital image analysing system was used to study capillary blood flow velocities and morphological parameters of perifoveal intercapillary areas and foveal avascular zones in normal and diabetic subjects. Diabetic patients showed a significant reduction in capillary blood cell velocities in comparison with normal subjects. Perifoveal intercapillary areas and foveal avascular zones were significantly increased in all stages of diabetic retinopathy, and both parameters increased with progressing diabetic retinopathy. Significant changes in the perifoveal intercapillary areas were observed between normal subjects and patients with no retinopathy.

Video fluorescein angiography: method and clinical application.

Video fluorescein angiography, combined with a picture analyzing system, is a clinically applicable, objective method of evaluating the retinal blood-flow parameters. Optical density measurements were performed on videorecordings of fluorescence angiograms by means of a picture-analyzing system in order to determine the circulation parameters of the retina. These included: the arm-retina time (ART), the arteriovenous passage time (AVP), and the mean arterial dye-bolus velocity (MDV). Normal values for these parameters were derived from measurements in 75 healthy volunteers. The mean arm-retina time (ART) was 11.2 ± 3.3 s, the mean arteriovenous passage time (AVP) 1.45 ± 0.4 s and the mean arterial dye-bolus velocity (MDV) 6.39 ± 1.7 mm/s. No significant correlation could be shown between pulse or blood pressure and one of the retinal circulation parameters. A group of ten healthy volunteers was examined twice in order to obtain the intraindividual variation for the measuring parameters. The coefficient of variation for the ART was 18%, 10% for the AVP, and 26% for the MDV.

Perifoveal microcirculation with non-insulin-dependent diabetes mellitus

Fluorescein angiograms were performed to evaluate perifoveal capillary blood velocities (v), capillary density (perifoveal intercapillary areas: PIA) and the foveal avascular zone (FAZ) by means of the scanning laser technique (SLO-101 Rodenstock). The angiograms were digitally stored and the data quantified off-line with an image analyzing system (IBAS). In the present study 46 patients with non-insulin-dependent diabetes mellitus (NIDDM) were examined and their data compared with that of 31 healthy volunteers. The perifoveal capillary flow velocity of the NIDDM subjects (v = 2.33±0.36 mm/s) was significantly (P <0.01) decreased as compared to healthy subjects (v = 2.86 ±0.41 mm/s). The perifoveal intercapillary areas in the foveal avascular zone were significantly increased in patients with NIDDM (PIA=10029 ± 3402 μm2; FAZ = 0.415 ± 0.272 mm2) as compared with healthy subjects (PIA = 3965 ± 467 μm2; FAZ=0.221 ± 0.071 mm2). These data suggest the possibility that a decrease in perifoveal capillary blood velocities in combination with decreased capillary density (enlarged PIA) and an enlargement of the foveal avascular zone may occur in patients with NIDDM. The determination of these parameters could help in monitoring the progress of diabetic retinopathy and diabetic maculopathy.

Role of Rheologic Factors in Patients with Acute Central Retinal Vein Occlusion

PURPOSE To assess the rheologic findings in acute central retinal vein occlusion (CRVO) with respect to associated risk factors, the clinical appearance of ischemic or nonischemic CRVO, and to elucidate the etiology of possible changes. METHODS The authors enrolled 173 patients with acute CRVO (ischemic, 33%; nonischemic, 67%) in this prospective study. One hundred seventy-three patients who were matched for age, sex, and cardiovascular risk factors served as control subjects. All patients underwent testing to determine hematocrit values, plasma viscosity (PV), erythrocyte aggregation (SEA), and erythrocyte rigidity (SER). RESULTS Hemocrit values and PV were increased significantly (P<0.01) in patients with ischemic and nonischemic CRVO compared with control subjects but did not differ significantly between the two groups. No significant differences were found in SEA and SER values between the clinical subsets of patients with CRVO and when the patients were compared with matched control subjects. Analysis revealed that hemocrit and PV values were (P<0.001) increased significantly independent of associated cardiovascular risk factors. CONCLUSION These results suggest that increased hemocrit and PV values may be contributing factors in the pathogenesis of CRVO.

Retinal circulation times in diabetes mellitus type 1.

Video fluorescein angiography was performed in 124 patients between 18 and 65 years of age (mean 35.0, SD 12.3 years) with juvenile-onset, insulin-dependent diabetes mellitus (type 1). The arm-retina time (ART) and the retinal arteriovenous passage time (AVP) were measured by means of a picture analysis system to quantify the retinal microcirculation. Glucose metabolism was assessed by the blood level of haemoglobin A1c. The ART 11.5, SD 3.4 s) was similar to that in normal persons (11.2, SD 3.3 s), while the AVP was significantly longer in the diabetics (AVP = 2.35, SD 0.87 s) than in normal persons (AVP = 1.45, SD 0.40 s). The patients with severe diabetic retinopathy showed the most impressive change in AVP. The diabetics with good glycaemic control, that is, with glycosylated haemoglobin (HbA1c) less than or equal to 8.0 g/dl, had a shorter AVP than patients with bad glycaemic control (HbA1c greater than or equal to 9.5 g/dl). The group with a history of diabetes for less than five years showed circulation parameters similar to those of normal persons. The AVP in this group was significantly shorter than in groups with a history of diabetes for five or more years.

Explorative study of interleukin levels in the human cornea

Abstract• Background: The presence of interleukins has been demonstrated in the cornea and other ocular tissues. Although pathogenic mechanisms are unknown, interleukins seem to be involved in inflammatory disorders of the cornea. The present study was undertaken to analyse concentrations of interleukin- Iβ (IL-1β) and interleukin-6 (IL-6) in human corneas with various clinical diagnoses. • Methods: Immediately after keratoplasty 127 explanted human corneas with various corneal diseases were snap frozen and cryosections were prepared for histological examination. Furthermore, the protein content was measured according to the method of Bradford and the concentration of IL-1β and IL-6 were determined using a specific immunosorbent test (ELISA). • Results: It was found that IL-1β and IL-6 level were clearly higher in corneas with ulcerations and distinct inflammatory signs. Lower levels of both interleukins were found in corneas with a weak expression of inflammatory signs. • Conclusions: Keratitis, keratoconus with inflammatory signs, and ulcerating processes showed higher interleukin levels than corneas with non-inflammatory disorders like scar formation, corneal dystrophy and keratoconus. The results could show that, depending on the clinical diagnosis, the inflammatory status of the cornea may be evaluated by the interleukin levels determined in the corneal tissue.

Poor prognosis of severe chemical and thermal eye burns: the need for adequate emergency care and primary prevention.

The epidemiology and wound healing following medical and surgical treatment of 101 patients with 131 severely burnt eyes due to chemical or thermal agents have been analyzed. Most of the accidents occurred at work (72.3%); the majority of the burns were chemical (84.2%), of which 79.8% were caused by alkalis. The long average duration of treatment on ward (5.2 ± 4.1 months) and the high number of surgical interventions (8.0 ± 8.0) indicate the difficulties in treatment and the delayed recovery of the affected eyes. Despite improved possibilities of immuno-suppression after keratoplasty (cyclosporin A) and new methods of surgery (Tenon plasty), the possibilities of an optical rehabilitation are still limited. A visual acuity of 6/60 or better was achieved in 39 eyes (32.2%). Immediate irrigation was reported in 56.1% of accidents at the place of work and in 42.8% of accidents sustained at home. There was a significant difference with respect to the extent of damage, the treatment on ward and the number of surgical interventions. The visual prognosis for eyes which received immediate irrigation was significantly improved. Eye protection was not used in any of the 101 cases. Spread of information is necessary for adequate emergency care for eye burns as well as for permanent employment of protective glasses in high-risk occupations.

Quantification of characteristic blood-flow parameters in the vessels of the retina with a picture analysis system for video-fluorescence angiograms: initial findings

Fluorescence angiograms of the retina were performed on 12 healthy, adult subjects between the ages of 20 and 52 years with a 30° fundus camera (C. Zeiss), a low-light TV camera and a video recorder. Characteristic blood-flow parameters for the retina were obtained from the video recording using the picture-analysis system (Mikrovideomat 3, C. Zeiss). These included: the arm-retina time (ART), the arteriovenous passage time (AVP) and the arterial contrast-medium velocity (ACMV). Normal values for these parameters were derived for the four retinal quadrants and then discussed. In addition, the filling characteristics of venules were measured and discussed.

Macular capillary particle velocities: a blue field and scanning laser comparison

Abstract• Background: Two different techniques are available for measurement of macular capillary particle velocities. The psychophysical blue field simulation technique gives data on macular leukocyte flow velocities, while the scanning laser technique provides information on capillary blood velocities of hypofluorescent segments in the macular network. Published velocity data differ considerably between the two methods. The current study was undertaken to compare the two measuring techniques in a group of healthy volunteers. • Methods: Thirty-two healthy subjects (12 man, 20 women, mean age 27 years) participated in this study. All subjects underwent entoptic leukocyte visualization by means of blue field simulation followed by fluorescein angiography using scanning laser ophthalmoscopy. • Results: The capillary blood velocities measured using the scanning laser technique were significantly higher (P < 0.01) than the flow velocities estimated with the blue field simulation technique (2.68 ± 0.3 mm/s vs 0.89 ±0.2 mm/s). No significant correlation between the flow velocities was found (r = −0.22). • Conclusion: The differences may be related to different measuring locations and/or measurements of different phenomena. The blue field technique estimates average leukocyte flow in the macular network, whereas the scanning laser technique quantifies the velocity of erythrocyte aggregates in the capillary lumen of the para- and perifoveal network. A combination of both techniques may be helpful in interpreting physiological responsiveness and altered velocity pattern in diseased eyes.

Macular microcirculation in cystoid maculopathy of diabetic patients.

BACKGROUND--In patients with diabetic macular oedema and central cysts ischaemia of the retina appears to be an important contributing factor in the pathogenesis of cysts. This study was performed to further elucidate the role of the inner retinal microcirculation in diabetic cystoid macular oedema (CMO). METHODS--Video fluorescein angiography allows visualisation of the macular microvasculature and measurements of the capillary blood velocity (CBV), foveal avascular zone (FAZ), and perifoveal intercapillary area (PIA, characterising capillary density). RESULTS--Twenty three diabetic subjects with CMO, matched diabetic patients without macular oedema (n = 23), and healthy subjects (n = 23) were included. CBV, PIA, and FAZ did not differ significantly among diabetic groups regardless of presence of cystoid changes. CBV was significantly reduced (p < 0.0001) and PIA was more than doubled in both diabetic groups (p < 0.0001) when compared with healthy subjects. Furthermore, FAZ showed a nearly doubled size in diabetic patients without macular oedema (p < 0.01) and a less pronounced enlargement (by 29%) in diabetics with CMO (p < 0.05). CONCLUSION--The results indicate that the retinal microcirculation in diabetic patients is markedly altered when compared with healthy subjects, regardless of CMO presence. In CMO patients the microcirculatory changes are similar to those of diabetic patients without macular oedema. Thus inner retinal perfusion does not contribute to tissue ischaemia leading to cystoid formations in diabetic maculopathy.