Use of vancomycin in vitrectomy infusion solution and evaluation of retinal toxicity

The retinal toxicity of vancomycin in infusion solution used in vitrectomy and lensectomy was investigated in rabbit eyes by means of electroretinography and histologie study (light microscopy). Concentrations of 8g/ ml, 16g/ml, and 32g/ml of vancomycin in balanced salt solution caused no abnormal ERG or histologic changes. However, ERG amplitude depression and abnormal histologie changes occurred when the concentration of 100g/ml of vancomycin was used.Supported in part by U.S. Public Health Service grants EY07541 and EY02377 from the National Eye Institute, National Institutes of Health, Bethesda, MD.     

Cytotoxic effects of antiproliferative agents on human retinal glial cells in vitro

Purpose: Proliferative vitreoretinopathy (PVR) is characterizedby the formation of cellular membranes on the detached retina and also in the vitreous. Glial cellscan be found in epiretinal and subretinal membranes from eyes with PVR, proliferative diabeticretinopathy (PDR), idiopathic macular pucker, uveitis and other diseases affecting theretina. Proliferation and contraction of glial cells appears to play a role in the pathogenesisof PVR. This study is designed to inspect the effectiveness of harringtonine, as well as colchicine,daunomycin and fluorouracil, against cellular proliferation of cultured human retinal glial cellsthat might be involved in the retinal and/or vitreous proliferation. Methods: Cultures of human retinal glial cells were preparedusing the enzyme digesting method. Cells that had been in culture for 2–5 passages were usedin this study. Harringtonine (0.063 g/ml 2.0 g/ml), colchicines(0.5 g/ml 16.0 g/ml), daunomycin (0.1 g/ml 3.2 g/ml) and 5-fluorouracil(0.5 g/ml 16.0 g/ml) were added to cultures of human retinal glial cellsand the proliferation rates of the cells were measured by the MTT method. Results: Harringtonine at the dosage of 0.063 g/mlinduced suppression of cellular growth, but the changes were not statistically significant (p > 0.05).At a dosage ranging from 0.125 g/ml to 2.0 g/ml, harringtonine significantly suppressedcellular growth according to the test (p < 0.01). Likewise, other antiproliferativeagents inhibited cellular growth significantly at a dosage from 1.0 g/ml to 16.0 g/ml(colchicine), 0.2 g/ml to 3.2 g/ml (daunomycin) and 1.0 g/ml to 16.0 g/ml(5-fluorouracil), but not at 0.5 g/ml (colchicine), 0.1 g/ml (daunomycin) and0.5 g/ml (5-fluorouracil). The ID₅₀ were 0.33 g/ml (harringtonine), 3.11 g/ml (colchicine), 0.79 g/ml (daunomycin) and 5.23 g/ml (5-fluorouracil), respectively.Conclusions: Harringtonine was extremely effective ininhibiting human retinal glial cell proliferation, like other antiproliferative drugs such as colchicine,daunomycin and 5-fluorouracil. Harringtonine, therefore, may be a candidate for further studies regardingthe treatment of experimental PVR.     

Vitreoretinal toxicity of basic fibroblast growth factor

Basic fibroblast growth factor (b-FGF) is one of the multifunctional growth factors with important therapeutic potential in the field of ophthalmology. It is also implicated in pathogenesis of vitreoretinal proliferative diseases. In the present study, we evaluated its vitreoretinal toxicity by means of clinical observation, electroretinography (ERG), and histopathology after injection of different doses of b-FGF into the vitreous of rabbit eyes. Doses of b-FGF up to 2 g per eye caused no toxicity; however, injection of 4 g or more resulted in sight-threatening vitreoretinal proliferative changes. This information is important for studies aimed at evaluating the therapeutic potential of b-FGF in retinal diseases.Despite some degree of vitreous organization and opacification, retinal folds, and small areas of traction retinal detachment, the amplitudes of ERGs were normal or even increased (hyperpolarization) in eyes which received 8 g of b-FGF.     

In-vivo-Messungen der Breite des Schlemmschen Kanals beim Hydrophthalmus

Zusammenfassung In-vivo-Messungen der Breite des Schlemmschen Kanals ergaben bei 9 Hydrophthalmusaugen einen Mittelwert von 678 m. Die Extremwerte lagen bei 600 m und 800 m. Damit unterscheiden sich diese Werte signifikant von denen, die bei Glaucoma-simplex-Augen in vivo ermittelt worden waren (Mittelwert ¯x: 542 m, Extremwerte 425 m und 625 m).Die Kanalbreite bei Hydrophthalmusaugen nimmt sowohl mit dem Hornhautdurchmesser als auch mit der Höhe des Augeninnendrucks zu.Die Erfolgsaussichten einer Trabekulotomie bei Hydrophthalmusaugen sind offenbar besser, wenn die Kanalbreite unter 650 m liegt. Die Trabekulotomie sollte deshalb so früh wie möglich ausgeführt werden.

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In vivo-measurements of the latitude of Schlemm's canal in buphthalmos

Summary In 9 cases of buphthalmos in vivo-measurements of the latitude of Schlemm's canal gave us a mean value of 678 m. The extreme values ranged between 600 m and 800 m. Therefore these values differ significantly from those measured in vivo in chronic simple glaucoma (¯x: 542 m, extreme values 425 m and 625 m). The latitude of Schlemm's canal correlates with the diameter of cornea and the rise of intra-oculare pressure.In cases of buphthalmos the success of trabeculotomy seems to be better, if the latitude of Schlemm's canal is less than 650 m. Trabeculotomy should therefore be performed as soon as possible.

     

Retinal toxicity and ocular kinetics of 1-β-D-arabinofuranosyl-E-5-(2-bromovinyl)uracil in rabbits

The intraocular penetration of 1--d-arabinofuranosyl-E-5-(2-bromovinyl)uracil (BV-araU), a new antiviral drug, after oral administration, the effects of non-toxic intravitreal doses of BV-araU, and the intraocular kinetics of BV-araU after intraocular injection were studied in rabbits. The intravitreal penetration of BV-araU after oral administration was very poor: 0.11 ± 0.13 g/ml and 0.20 ±0.02 g/ml respectively in albino and pigmented rabbits 2 h after 30 mg/kg. An intravitreal injection of 200 g BV-araU caused transient electroretinographic (ERG) changes, whereas a 100-g injection and intravitreal irrigation with 20 g/ml BV-araU caused no ERG and histologic changes over the 4-week follow-up period. The half-life of the intravitreal concentration of BV-araU after an intravitreal injection was short (2.4 h). The results suggest that an intravitreal injection of 100 g BV-araU or an intravitreal irrigating solution containing 20 g/ml BV-araU is nontoxic to the retina and may be used for treatment of retinitis caused by varicella-zoster virus or herpes simplex virus type 1.     

The resistance of the trabecular meshwork to aqueous humor outflow

A theoretical model is presented that is able to explain for the first time the pressure drop across the trabecular meshwork. The ramified flow paths in the subendothelial region of the trabecular meshwork can be interpretated as a filter bed. Data from transmission electron microscope (TEM) photographs are the starting point of the theoretical consideration. Taking shrinkage of the sections into account, the pressure gradient across the subendothelial region amounts to 0.05 mm Hg. As these canaliculi are coated by a film of glycosaminoglycans (GAGs), the pressure drop is presumably a function of the film thickness. Only film thicknesses of 0.35 m lead to pressure gradients in the experimentally verified magnitude. As the whole filter bed probably does not contribute to the filtration but only about 10%, the pressure drop specified is reached when the GAG coating is 0.25 m. As these values seem to be fairly realistic, it can be concluded that the subendothelial region of the juxtacanalicular meshwork (about 2 m thickness) can be regarded as the locus generis of aqueous humor outflow resistance.     

Die Stereo-Ultrastruktur der Cornealoberfläche bei der Ratte

Zusammenfassung Die dreidimensionale Beschaffenheit der Cornealoberfläche der Ratte wurde mittels des Scanning Electron Microscope und anhand konventioneller elektronenmikroskopischer Schnittpräparate untersucht. Dabei konnte das Vorhandensein von Mikrovilli (0,15 breit, bis 1,0 hoch) und von Mikroplicae (0,1–0,2 breit, 0,3–0,4 hoch, 1–3 lang) nachgewiesen werden. Bei diesen Strukturen dürfte es sich um während der Desquamation entstandene Ausstülpungen der Epithelzellmembran im Bereiche der Desmosomen handeln.

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The stereo ultrastructure of the corneal surface in rat

Summary Combined morphological examination of the corneal surface of rat both with the scanning and the transmission electron microscope reveals two kinds of protrusions covering the polygonal, regularly arranged epithelial cells: Mikrovilli and Mikroplicae; the former being approximatively 0.15 large and up to 1.0 high, the latter being 0.1–0.2 large, 0.3–0.4 high and 1–3 long. These formations are with high probability the remnants of desmosomes having been formed during desquamation.

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Diese Untersuchungen wurden mit Unterstützung des Fonds National suisse de la recherche scientifique (Nr. 5322.3) durchgeführt.     

The effect of body temperature on the murine electroretinogram

Purpose: To study the effect of body temperature on the murine electroretinogram (ERG). Methods: The corneal ERG elicited by a strobe flash from dark-adapted mice was recorded using a saline wick electrode while measuring rectal temperature continuously. The mouse was placed within a cylindrical coil of tubing through which water circulated from a temperature controlled bath. The body temperature of the mouse was changed stepwise between 30 and 37°C. Results: ERGs of approximately normal configuration were recorded at body temperature ranging between 30 and 37°C. The maximum amplitude of the a- and b-waves varied linearly with temperature. The rate of change of b-wave amplitude was about 100 V/degree. At 30°C, maximum b-wave amplitude was about 400 V; at 37°C it was about 1000 V. A change in body temperature produced a rapid change in ERG amplitude. Conclusion: The murine ERG is very sensitive to changes in temperature. In order to monitor the ERG accurately over time, continuous recording of body temperature is essential.     

Correlation of electroretinographic and fluorescein angiographic findings in unilateral central retinal vein obstruction

Background: In central retinal vein obstruction (CRVO), electroretinogram (ERG) abnormalities and extensive retinal capillary dropout (CD) in the fluorescein angiogram (FA) are good indicators of retinal ischemia. We retrospectively studied patients with unilateral CRVO and compared the ERG and FA results Methods: Single white flash ERG, photopic ERG, scotopic ERG and flicker ERG were recordered in 30 cases of unilateral CRVO. We analyzed the correlation between the ERG results and the presence/absence of extensive CD Results: The ERG b/a-wave amplitude ratios, photopic and scotopic b-wave amplitudes, and flicker amplitudes were significantly smaller (P<0.05) in eyes with extensive CD (n=12, 40%), than in eyes without (n=18, 60%). When the photopic or scotopic b-wave amplitudes were normal or supernormal, extensive CD on FA was absent in all eyes. When the b/a-wave ratios were 1.0 or when the b-wave amplitudes with white flash or flicker amplitudes were normal or supernormal, extensive CD was present in less than 32% of eyes Conclusion: These results suggest that the ERG results, especially the b/awave amplitude ratio, are significantly correlated with the presence/absence of CD on FA in CRVO.     

Effects of the beta1-selective adrenergic antagonist betaxolol on electroretinography in the perfused cat eye

The effects of the ₁-selective adrenergic antagonist betaxolol on electroretinography (ERG) were studied in the isolated and arterially perfused cat eye. Betaxolol increased the perfusion flow rate, significantly at the administrations of more than 50M concentrations and induced a dose-related, reversible increase in the amplitudes of both the a-wave and b-wave of ERG. These results suggest that the calcium-channel blocking mechanism of betaxolol has a beneficial influence on ocular blood flow and retinal electrical activity in response to light. As it is known that ERG is a good indicator of the functional integrity of the retina, this indicates that betaxolol could be an ideal drug for treating glaucoma in which ischemia is involved to some extent.     

Clinical S-cone ERG recording with a commercial hand-held full-field stimulator

Our purpose was to explore S-cone ERG protocols for a commercial full-field hand-held stimulator that contains colored LEDs, and to see whether the test would be useful as a part of routine ERG testing. S-cone responses were elicited by blue flashes over a longer-wavelength background. With the standard stimulator containing blue (461 nm), green (513 nm) and red (652 nm) LEDs, we were unable to obtain satisfactory responses. Reproducible S-cone ERGs were obtained with a stimulator that had been custom-fitted with shorter-wavelength blue (440 nm) LEDs for stimulation, and orange (590 nm) LEDs for background adaptation. S-cone responses took only a few minutes to record, and the typical waveform showed a slow peak at 45–50 ms with amplitude 3–9 V, but ranging from 0 V to more than 10 V. Larger waves appeared in a patient with enhanced S-cone syndrome. S-cone responses could also be obtained with an alternating blue-orange flicker protocol. We added the S-cone response to our regular ERG protocol for a number of months. Although most normal subjects and patients showed recognizable S-cone responses with this stimulator, the amplitudes were small and there was too much variability to make the technique effective for routine clinical testing. In general, the S-cone responses followed the standard cone ERG responses in disease.     

Untersuchungen über die Ultraviolettabsorption des normalen und des entzündlich veränderten Kammerwassers

Zusammenfassung In zahlreichen Untersuchungen wurde die Ultraviolettabsorption des menschlichen Kammerwassers vor und nach Bebrütung bei 37° C sowie vor und nach Zusatz von Hefenukleinsäure (Hoechst) im Bereiche zwischen 220 und 320 m untersucht. Das normale menschliche Kammerwasser zeigte eine UV-Absorptionskurve, wie sie bei allen eiweißhaltigen Flüssigkeiten beobachtet werden konnte. Nach der Bebrütung des Kammerwassers bei 37° C wurde ein Anstieg der Extinktion im gesamten Absorptionsbereich beobachtet. Kammerwasser, das bei der Hypopyon-Iritis gewonnen wurde, zeigte ein ausgeprägtes Absorptionsmaximum bei 280 m, das nach der Bebrütung bei 37° C anstieg. Zusatz von Hefenukleinsäure (Hoechst) zum Kammerwasser bei der Hypopyon-Iritis führte zum Auftreten eines Absorptionsmaximums bei 260 m. Durch Bebrütung bei 37° C wurde ein Ansteigen dieses Maximums erreicht. Aus den Untersuchungen wurde der Schluß gezogen, daß im Kammerwasser Enzyme eine Rolle spielen, die für die Beseitigung zelliger Elemente von Bedeutung sein könnten.

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Summary In numerous investigations the ultraviolet absorption of human aqueous humour was examined within the range of 220–320 m before and after being incubated at 37° C, as well as before and after addition of yeastnucleinic acid (Hoechst). The normal human aqueous humour showed an ultraviolet absorption curve similar to that which can be observed in all fluids containing proteins. After the incubation of aqueous humour at 37° C an increased extinction was noticed within the whole range of absorption. Aqueous humour derived from hypopyon iritis showed a marked maximum of absorption at 280 m which increased after incubation at 37° C. Addition of yeast-nucleinic acid (Hoechst) to the aqueous humour derived from hypopyon iritis resulted in the appearance of maximal absorption at 260 m. An increase of this maximum was reached by incubation at 37° C. It was deducted from these examinations that enzymes which could be of importance in removing cellulary elements, play an important part in the aqueous humour.

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Résumé Dans de nombreux cas on a examiné l'absorption des rayons ultraviolets par l'humeur aqueuse de l'homme dans une zone de 220 á 320 m. Ces examens furent faits avant et après maintien du liquide dans une couveuse à 37°, et avant et après addition de l'acide nucléique de levure. L'humeur aqueuse normale montrait une courbe d'absorption telle qu'on l'observe pour tous les liquides contenant des protéines. Après maintien de l'humeur aqueuse dans une température de 37° on a constaté une extinction plus grande dans tout le champ d'absorption. L'humeur aqueuse des yeux atteint d'une irite à hypopyon montre un maximum d'absorption très marqué à 280 m qui augmente encore après exposition à 37°. Après addition de l'acide nucléique de levure à l'humeur aqueuse le maximum fut constaté à 260 m, et après exposition à 37° ce maximum se trouvait encore accru. De ces observations on a conclu qu'il y a dans l'humeur aqueuse des enzymes qui pourraient avoir une importance dans l'elimination des élements cellulaires.

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Riassunto In numerose ricerche venne studiato l'assorbimento dei raggi ultravioletti dell'acqueo umano prima e dopo riscaldamento a 37° e prima e dopo aggiunta di acido nucleinico dei fermenti (Hoechst) in un campo oscillante fra 220 e 320 m. L'acqueo umano normale mostrava una curva di assorbimento quale si osserva in tutti i liquidi contenenti proteine. Nell'acqueo riscaldato a 37° si è notato un aumento dell'estinzione in tutto il campo di assorbimento. L'acqueo ottenuto da occhi affetti da ipopionirite mostrava un marcato massimo di assorbimento a 280 m che aumentava dopo riscaldamento a 37°. Con l'aggiunta di acido nucleinico dei fermenti (Hoechst) all'acqueo in caso di ipopion-irite, si osservò un massimo di assorbimento a 260 m, che aumenta dopo riscaldamento a 37° C. Si conclude da tali ricerche che gli enzimi nell'acqueo giuocano un ruolo che potrebbe avere importanza nell'eliminazione di elementi cellulari.

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Universitäts-Augenklinik, Würzburg.     

Toxicity of 1-(β-d-arabinofuranosyl)cytosine after intravitreal injection in the rabbit eye

The retinal toxicity of intravitreally injected 1-(-d-arabinofuranosyl)cytosine (cytarabine) was examined in 7 chinchilla rabbits to determine if cytarabine can be used as local therapy for vitreoretinal non-Hodgkin's lymphoma. Fractionated dose of 600 g, 1500 g, and 2700 g cytarabine in stabilized saline were given intravitreally in one eye (2 × 300 g, 5 × 300 g, and 3 × 900 g, respectively, with an interval time of 24 h) and stabilized saline in the other eye as control. Toxic effects were evaluated with biomicroscopy, direct ophthalmoscopy, fluorophotometry, electroretinography, light, and electron microscopy. Toxic effects were found with the 1500 g and 2700 g doses only. They consisted of a temporary impairment of the blood retina barrier function for fluorescein as measured by fluorophotometry and an irreversible change of the b-wave in the electroretinograms. No histopathologic changes were seen under the light microscope. Electron microscopic examination showed aberrations in the synaptic pedicles of the photoreceptor cells at a dose of 1500 g cytarabine. The results suggest that the cytarabine dose that is expected to be therapeutic for vitreoretinal non-Hodgkin's lymphoma (about 90 g given in three doses of 30 g) is non-toxic for ocular structures.Correspondence to: J.A. van Best     

Die Dunkeladaptation des Protanomalen

Zusammenfassung Bei einem normalen Trichromaten und einem Protanomalen wird der Dunkeladaptationsverlauf der Helligkeitsschwelle für weiße sowie für 4 verschiedene langwellige Spektrallichter (585 m, 603 m, 628 m, 667 m) registriert. Während die Kurven für weiße Testreize bei beiden Vpn. vollkommen übereinstimmen, ergibt sich mit monochromatischen Testreizen beim Protanomalen eine mit der Wellenlänge zunehmende relative Schwellenerhöhung, die sich ausschließlich auf den vor dem Knick gelegenen photopischen Kurvenabschnitt beschränkt und mitMit 2 Textabbildungen     

Lamellar excimer laser keratoplasty: Reproducible photoablation of corneal tissue

We examined the depth of ablation of the recipient bed with different counts of oscillations of excimer laser beam, to determine the correlation between planned and real depth. The ablation rate per oscillation was tested preoperatively by blackened photographic paper of defined thickness and thus was calculated to be 5 m. Forty pig eyes were used for the first study. Each eight eyes were ablated in the planned depth 100 m, 200 m, 300 m, 400 m and 500 m. The corneal thickness was measured with an ultrasonic pachymeter before and after the procedure. The depth measured after the photoablation was 99.4 ± 36.4 m for 100 m planned depth, 186.7 ± 55.3 m for 200 m, 298.4 ± 68.5 m for 300 m, 373.9 ± 65.7 m for 400 m and 480.1 ± 59.3 m for 500 m. Comparing the depth measured after the photoablation to planned depth, there was a significant correlation (correlation coefficient: R = 0.93; p < 0.0001). Five other corneas trephinated from pig cadaver eyes were ablated from the endothelial side to the desired thickness (100 to 500 m) of lamellar graft. In a second step a donor mask was placed onto the cornea and a laser light spot was led until perforating on all sides. The lamellar keratoplasty was completed by suturing the corneal graft into the bed. Macroscopic and microscopic examination of sutured eyes after fixation showed a good fit of wound margins and stromal interface. These results indicate that excimer laser is useful for reproducible corneal photoablation in lamellar keratoplasty.     

Effect of Prostaglandin E2 on aqueous humor flow in the rabbit eye

Summary The examinations were carried out in albino rabbits under urethane anaestesia. After intracameral injection of 0.5 g Prostaglandin E₂, dissolved in 10 l 10% ethanol, intraocular pressure increased by 20.5±4.9 mm Hg. Aqueous humor protein concentration in the uninjected control eyes was 0.176±0.03 g%. Thirty minutes after intracameral injection of 10 l 10% ethanol solution the concentration rose to 0.38±0.19 g-%, and after of 0.5 g Prostaglandin E₂ to 1.85 ±0.41 g% These interventions were not followed by significant changes in aqueous humor osmolarity (normal value 313.7±17.9 mOsm, after ethanol 330 5±18. 0, and after prostaglandin E₂ 329.3±6.9).In a special series of experiments the rate of aqueous humor production was determined. In the uninjected control eyes a value of 1.57±0.61 l/min was found, but after intracameral injection of 0.5 g prostaglandin E₂, 5.45±1.99 l/min.The authors draw the conclusion that prostaglandin E₂ increases intraocular tension not by enhancing aqueous humor production but by disrupting the bloodaqueous humor barrier.

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Zusammenfassung Die Untersuchungen wurden an Albinokaninchen in Urethannarkose durchgeführt. Nach Injektion von 0,5 g Prostaglandin E₂ (in 10 l10%iger Äthanollösung) in die Vorderkammer stieg der Augenbinnendruck um 20,5±-4,9 mm Hg an. Der Gesamteiweißgehalt im Kammerwasser der intakten Kontrollaugen betrug 0,176±0,03 g-%. 30 min nach Einspritzung von 10 l 10%iger Äthanollösung in die Vorderkammer erhöhte sich der Gesamteiweißgehalt auf 0,38±0,19 g-%. Diese Einwirkungen hatten keine signifikante Änderung der Kammerwasser-Osmolarität zur Folge (Normalwert 313,7±17,9 mOsm, nach Äthanol 330,5±18,1 und nach Prostaglandin E₂ 329,3±6,9).In einer besonderen Versuchsreihe wurde die Kammerwasserproduktion bestimmt. In den intakten Kontrollaugen ergab sich hierbei ein Wert von 1,57±0,61 (l/m, nach Gabe von 0,5 g Prostaglandin E₂ aber 5,45±1,99 l/min.Die Autoren ziehen den Schluß, daß Prostaglandin E₂ den Augenbinnendruck nicht durch Steigerung der Kammerwasserproduktion, sondern durch Schädigung der Blut-Kammerwasserschranke erhöht.

     

Inhibition of corneal allograft reaction by CTLA4-Ig

Background: Activation of T cells requires both the interaction of T-cell receptor with major histocompatibility complex on the antigen-presenting cell and costimulatory signals, for instance the B7 antigens expressed on antigen-presenting cells and the CD28 molecule expressed on T cells. A recombinant fusion protein, CTLA4-Ig, has been produced that contains the extracellular domain of human CTLA4 fused to IgGl constant region and that binds the B7 molecule with high affinity. Blocking the CD28/B7 interaction with CTLA4-Ig inhibits T cell activation in vitro and in vivo. Methods: We used CTLA4-Ig in a fully MHC-mismatched mouse keratoplasty model. The animals were divided into four groups: (1) no treatment, (2) intraperitoneal treatment with 130 g CTLA4-Ig, (3) intraperitoneal treatment with 300 g CTLA4-Ig, (4) subconjunctival treatment with 290 g CTLA4-Ig. Results: The allograft reaction occurred in untreated animals between days 12 and 16 (mean 13.5). While topical application of CTLA4-Ig seemed to shorten the graft survival (mean 11.6 days) and systemic application of 130 g had no influence (mean 14.0), only intraperitoneal injection of 300 g of CTLA4-Ig prolonged the survival of allografts (mean >20 days) (P<0.01). Conclusion: CTLA4-Ig prolonged significantly the survival of corneal allografts in a fully MHC-mismatched mouse keratoplasty model, but the small antigen load of the corneal transplant and the anterior chamber-associated immune deviation (ACAID) may have a disadvantage to induce tolerance in this model of CTLA4-Ig therapy.Presented at JERMOV 1996 in Montpellier     

Argon-Laser Coagulation der Kanincheniris

Zusammenfassung Beim Chinchilla-Kaninchen wurde das kammerwinkelnahe Drittel der Iris nach Ermittlung der Schwellenwerte mit Argon-Laser-Energien von 0,02–4,8 J und einem Brennfleckdurchmesser von 50 m coaguliert. Irisschädigungen, die mit einer Energie von 1,2 J erzielt werden konnten, untersuchten wir 30 min post coagulationem sowie 72 Std, 10 und 28 Tage nach der Exposition spaltlampen-, stereo- und rasterelektronenmikroskopisch. Nach 30 min findet sich ein zentraler Substanzdefekt von 50–80 m Durchmesser, der von einer intermediären Zone 30–60 m Breite stärkerer Zelldestruktion umgeben ist. Daran schließt sich eine periphere Zone abnehmender Zellstörung bis zu 200 m Breite an. Nach 72 Std lassen sich am Rand des zentralen Defektes entzündliche Zeichen nachweisen. Nach 10 bzw. 28 Tagen bleibt der zentrale Defekt erhalten, die oben genannten angrenzenden Zonen sind jedoch nicht mehr eindeutig abgrenzbar.

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Argon-laser coagulation in the rabbit irisDetermination of threshold dosis and respective scanning electron microscopic findings

Summary The lateral third of the iris near the chamber angle was photocoagulated after determination of the threshold dose with argon-laser energy of 0.02–4.8 J and spot diameters of 50 m. Iris lesions produced with energy levels of 1.2 J, were examined with slitlamp, dissecting microscope, and scanning electron microscope. After 30 minutes the following findings were recorded: central stromal defect 50–80 m in diameter, surrounded by an intermediary zone of 30–60 m with severe cell destruction; a peripheral zone up to 200 m in breadth with less cell fragmentation adjacent to the intermediary zone. After 72 hours the margin of the central defect showed inflammatory changes. After 10–28 days the central defect remained stable; the bordering zones described previously were no longer discernible.

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Auszugsweise vorgetragen auf der 45. Versammlung der Vereinigung Rhein-Mainischer Augenärzte am 14. und 15. Oktober 1972 in Mainz.

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Die Untersuchungen wurden in dankenswerter Weise unterstützt durch die Jung-Stiftung für Wissenschaft und Forschung und die Stiftung Volkswagen-Werk.     

Contact diode laser: High power application through fiberoptic cutting tips

Diode laser energy has been applied through a fiberoptic probe using a power setting of 2.5 watts (W) in the continuous mode. In this study we employed high-power diode laser energy (4 to 12 W, continuous wave) to incise ocular tissue through a fiberoptic probe using 100m and 300m tips. The retina was photocoagulated with a 300m orb tip. No bleeding occurred at the incision sites. Histologic evaluation revealed coagulation into the healthy tissue ranging from 10 to 50m.     

Distribution of calcium and sulphur in the blue-light-exposed rat retina

Background: Blue-light exposure inhibits cytochrome oxidase and may therefore inhibit retinal metabolism. The reduced metabolism decreases the extrusion of calcium from the photoreceptor cell. Overload of calcium is proposed as one of the factors that lead to photoreceptor degeneration after light exposure. The light-induced photoreceptor degeneration can be ameliorated by calcium overload blocker. In the present study the calcium concentration was measured in the inner and outer segment layer of the rat retina. Methods: Six eyes were exposed to blue (404 nm) light at a retinal dose of 380 kJ/m². Five eyes served as the control group. The calcium and sulphur distributions were measured with a nuclear microprobe in the freeze-dried rat retina. The proton beam size was 12 × 12 m and the energy of the protons was 2.55 MeV The calcium concentration was calculated using sulphur as a reference. Results: The level of calcium per milligram sulphur was 21 g (range 17–23 g) in the inner segment of the control retina. It increased to 62 g/mg sulphur (range 52–67 g) and 61 g/mg sulphur (range 58–66 g) 1 h and 12 h after blue-light exposure, respectively. Conclusion: The findings of the present study support the idea that accumulation of calcium in the inner segment layer is one of the factors that cause photoreceptor degeneration.