Martin Reim

Retinal Hemodynamics Using Scanning Laser Ophthalmoscopy and Hemorheology in Chronic Open-angle Glaucoma

PURPOSE Recent studies suggest that elevated intraocular pressure is not the only causative factor for the development of visual field loss and optic nerve damage in glaucomatous eyes. The authors determine whether retinal hemodynamics or blood fluidity are alternated in eyes of patients with open-angle glaucoma compared with those of age- and sex-matched healthy subjects. METHOD High-quality video fluorescein angiograms were obtained from single eyes of 51 patients with chronic open-angle glaucoma. From these angiograms, the arm-retina time, mean dye velocity, and arteriovenous passage time were quantified. The data from patients were compared with those of an age- and sex-matched group of healthy subjects. RESULTS In patients with chronic open-angle glaucoma, an 11% reduction of the mean dye velocity (P < 0.05) and a 41% prolongation of the arteriovenous passage time (P < 0.01) was observed relative to the values obtained among the control subjects. Among hematocrit values, plasma viscosity, and erythrocyte aggregation, only plasma viscosity showed a significant increase (4%; P < 0.01) in patients with chronic open-angle glaucoma. CONCLUSION These results indicate that a pronounced circulatory deficit exists within the retinal vasculature of glaucomatous eyes, which may coexist with, but cannot be fully attributed to, an increase in plasma viscosity.

Retinal Capillary Blood Flow Measurement with a Scanning Laser Ophthalmoscope Preliminary Results

The scanning laser technique in combination with digital image analysis allows direct objective measurement of flow velocities in perimacular capillaries. In addition, the complete macular network of capillaries can be observed. By means of digital frame-to-frame picture analysis of digital recordings, blood flow velocities and morphologic data have been measured. The mean flow velocity in perimacular capillaries observed with the scanning laser ophthalmoscope in healthy subjects (n = 21) amounted to 3.28 +/- 0.45 mm/second. In patients (n = 13) with diabetes mellitus (no or background retinopathy), the mean flow velocity was significantly reduced (2.89 +/- 0.57 mm/seconds) compared with healthy subjects. Morphologic data of the perifoveal capillary bed showed a significant reduction of capillaries in patients with diabetes mellitus when compared with healthy subjects.

Hemodilution therapy in central retinal vein occlusion

Systemic hemorheologic abnormalities may play a part in the pathogenesis of central retinal vein occlusions. A statistically significant elevation of plasma viscosity was found in patients with acute central retinal vein occlusion compared with control patients. Local retinal blood flow parameters including arteriovenous passage time and mean arterial dye bolus velocity were significantly altered in the central retinal vein occlusion patients compared with age-matched controls at baseline examination. We performed a randomized, prospective, single-blind clinical investigation to determine the effect of hemorheological manipulation on the clinical course and retinal blood flow of eyes with central vein occlusion. Hemodilution included plasma expansion with hydroxyethyl-starch, withdrawal of whole blood if the hematocrit was above 42%, and rheologic manipulation with parenteral pentoxifylline. We found a statistically significant improvement in visual acuity at 1 year post-treatment for the treated group compared with the control group (increase of visual acuity of 1.5 lines vs decrease of 1.5 lines). The retinal blood flow parameters were markedly improved soon after the institution of therapy, and this may have contributed to the improvement in visual acuity in the treated group. There was no statistically significant difference between the two groups in the progression to ischemic central vein occlusion.

Measurement of retinal hemodynamics with scanning laser ophthalmoscopy: Reference values and variation

High resolution video fluorescein angiography using scanning laser ophthalmoscopy allows the assessment of retinal macro- and microcirculation. Data on the retinal macrocirculation were obtained from 221 healthy subjects. The data were derived from estimations of the arm-retina time, the arteriovenous passage time and mean arterial dye velocity, characterizing the passage of fluorescein to the eye, the mean arterial plasma velocity, and the arteriovenous passage through the entire vascular bed of one segment. Additionally, the transit of hypofluorescent segments in the capillary macular network were measured in 90 healthy subjects. These parameters provide a wide range of information for understanding the physiology of healthy and diseased eyes. Fundamental for all interpretations is the knowledge of the physiological variations. In the present study the inter- and intraindividual variability of retinal hemodynamics in healthy volunteers were assessed. The interindividual variation was 23.8% for the arm-retina time, 20.7% for the arteriovenous passage time, 23.7% for the mean arterial dye velocity, and 14.2% for the capillary flow velocity; the coefficient for variation, characterizing the intraindividual variation, was 26.6%, 15.6%, 16.7%, and 7.9%, respectively. The knowledge of the inter- and intraindividual variation of retinal blood flow indices allows for a priori power estimations for pathophysiologic and pharmacological studies.

Eye burns: an emergency and continuing problem

Adequate treatment of eye burns is an essential task of rescue teams. Clinical and occupational medicine studies have shown that efficient emergency treatment can prevent severe eye damage, but therapy is frequently delayed or inadequate. When initial therapy has been delayed or missed, several treatment strategies, including surgery, are available that may improve the outcome of an injury with poor visual prognosis. Discussed in this review are common accident mechanisms, causative agents and biophysical/pathogenetic aspects of eye burns, together with emergency and long-term treatment strategies including surgical procedures, and factors influencing outcome.

The cornea surface and wound healing

Abstract Wound healing of the corneal is closely associated with the regeneration of the epithelium. It may be impaired by mechanical or chemical damage to the basement membrane, under infections, and in neuroparalytic conditions. Eye burns show such damage. Therefore, experimental models of alkali burns were widely used to investigate wound healing of the ocular surface. Mediators of inflammation play an important part in disease and healing processes. High amounts of inflammatory mediators inhibit the regeneration of the epithelium and induce ulceration. Then, serine and metalloproteinases are released on the ocular surface and inside the tissues. These enzymes melt the stromal matrix. Especially when leukocytes are present, superoxides also appear and destroy the organic substrates of tissues. Therefore, therapeutical support of wound healing on the ocular surface has to take into account many factors. It seems that rather a polyvalent therapy may have a better chance of success. As soon as the epithelial cover is completely closed, stromal wounds heal better, and sometimes inflammation subsides.

Retinal circulation times in quantitative fluorescein angiography.

We tried to obtain an overview of the quantitative state of the retinal circulation. Optical density measurements by an image analyzer were performed on video fluorescein angiograms for the determination of dye-dilution curves. To ensure that curves with a sharp peak were obtained, 1 ml sodium fluorescein 10% was flushed with 20 ml physiological saline. From dilution curves of a retinal arteriole and the corresponding venule, various retinal circulation times, T (x) (x=1, 25, 50, 75, and 100) and Tm, were calculated. T(1) corresponds to the difference in the time of initial dye appearance; T(50), to the so-called half-maxim time difference; T(100), to the difference in the time to peak intensity; and Tm, to the mean circulation time. T(50) showed the best reproducibility when it was examined at 49 retinal regions of 10 healthy volunteers with a double video-fluorescein angiogram that was obtained within 1 min. Normal values (mean ± SD) at the temporal superior region of 37 healthy volunteers were as follows: T (1) = 0.87 ± 0.66 s, T(25)=1.52±0.48 s, T(50)=1.83±0.50 s, T(75)=2.12±0.56 s, T(t00) = 2.73±0.76 s, and Tm = 2.69±1.25 s. We believe that these values give a general overview of the quantitative state of normal retinal circulation.

Surgical procedures in the treatment of most severe eye burns. Revival of the artificial epithelium.

Abstract Report of some clinical observations in 16 patients with severe and most severe burns of 19 eyes. Major problems were delayed regeneration of the epithelium, extensive ulceration of the sclera near the limbus, and subsequent corneal ulceration. The therapy with anti‐inflammatory drugs, macromolecular hyaluronic acid, fi‐bronectin, epidermal growth factor, free transplants of oral mucosa and conjunctiva was sometimes helpful, but could not induce stable epithelial regeneration. The major problem remained the inability of the epithelium to regenerate on the cornea. Therefore, an artificial epithelium was applied in many cases. When healthy conjunctiva touched closely the artificial epithelium at the limbus, it remained tightly attached to the corneal stroma, preserved its structure and even prevented corneal vascularisation for many months. However, when corneo‐scleral ulceration was present, the artificial epithelium failed to protect the corneal stroma from secondary ulceration and sloughed off. Therefore, new surgical procedures, a conjunctiva‐Tenon flap and a Tenon plasty were introduced to cover and to cure corneoscleral ulceration. These operations formed a new limbus, attached tightly to the rim of the artificial epithelium and prevented secondary ulceration underneath. Then under the protection of the artificial epithelium and the Tenon plasty the eye could be treated topically with corticosteroids for a long time. When the inflammatory response to the burn was healed, the natural epithelium recovered and the eye became ready for successful keratoplasty.

Retrospective study of severe alkali burns of the eyes

BACKGROUND Alkali burns are of special interest because of the rapid and deep penetration of alkali into the ocular tissues. PATIENTS AND METHODS This report examines the epidemiology, management and outcome of 42 cases of alkali burns of the eye admitted to the eye clinic of the RWTH Aachen from 1985 to 1992. Aspects examined were the nature of accident, type of alkali, treatment and complications. The intention was to use this information for improvement of prevention and treatment of these cases. RESULTS The age analysis showed the greatest at-risk population were the 20-40 year-old patients. 73.8% were industrial accidents, 30% happened to builders and labourers, 20% in the chemical industry and 20% in machine factories. At home most of the injuries were caused by lime and drain cleaners. Sodium and potassium hydroxide produced more extended and deeper damages than lime due to their rapid penetration through the ocular tissues. A delayed surgical intervention led to a longer time of stay in hospital and to a higher number of operations. All eyes could be prevented from melting, but an optical rehabilitation (visual acuity > 0.3) was achieved only in a few cases (14.5%). CONCLUSION There is a need to ensure adequate public awareness of the danger of alkali burns to the eye. Beside the primary prevention, adequate first aid with immediate and continuous irrigation is of paramount importance. A uniform concept for the management of these severe cases is necessary including an antiinflammatory medical and surgical treatment.

Remarks on the vitality of the human cornea after organ culture.

The purpose of this study was to obtain further information on the viability of organ-cultured human cornea. We thus used a specific staining method for succinate dehydrogenase (SDH), which is located in the membrane system of vital mitochondria. We examined fresh and long-term-cultured human corneas. After an initial incubation period in dextran-free culture medium, corneas were stored in a medium containing dextran. With respect to different appearances of the SDH staining, minimal essential medium without dextran seems to have a positive effect on the condition of epithelial cells. After renewal of the medium, keratocytes showed a brief improvement followed by a delayed deterioration, while the endothelial cells were severely damaged. However, best results for all three cell types were observed on the fourth day in a medium containing dextran. We therefore conclude that these corneas were best suited for transplantation.