Increased release of tenascin in tear fluid after photorefractive keratectomy

Background: Extracellular matrix protein tenascin (TN) is expressed in the anterior stroma during corneal wound healing. In this study we analysed TN release in tear fluid after photorefractive keratectomy (PRK). Methods: Tear fluid TN concentrations of ten PRK patients were measured with an immunoassay. Tear fluids were collected preoperatively and 1, 2 and 7 days after PRK. The tear fluid collection time and the volume of tears collected were registered. Because tear fluid flow was greatly increased postoperatively, tear fluid flow-corrected release (TN flux) was calculated. Results: The tear fluid flow was 4.50±0.94 l/min (mean±SEM) preoperatively, 55.48±16.70 l/min (P<0.01) on the 1st, 33.91±7.91 l/min (P<0.01) on the 2nd, and 13.79±5.49 l/min (P>0.05) on the 7th postoperative day. The preoperative TN concentration was 0.85±0.20 g/ml. On the 1st postoperative day it decreased to 0.37±0.17 g/ml (P>0.05), most likely due to the dilution effect caused by hypersecretion after PRK. The TN concentration was 0.67±0.12 g/ml (P>0.05) on the 2nd and 0.78±0.15 g/ml (P>0.05) on the 7th postoperative day. The preoperative TN flux was 5.23±1.88 ng/min. On the 1st and 2nd postoperative days the TN flux was 14.40±4.99 ng/min (P<0.05) and 22.66±6.I2 ng/min (P<0.05), respectively. On the 7th postoperative day a tendency towards decreased flux (14.00±6.02 ng/min, P>0.05) was observed. Conclusion: Although there is a minor decrease in TN concentration after PRK due to increased tear fluid flow, a significant increase in TN flux was observed. Complete reepithelialization of the ablated area was observed in all eyes at the follow-up visit on postoperative day 7.     

Intraocularer Druck und Kammerwasserzirkulations-Untersuchungen an Kaninchenaugen nach intravenöser Verabreichung von Propranolol (Inderal®)

Zusammenfassung Der intraoculare Druck der mit Urethan anaesthesierten Kaninchen betrug 20,8 mm Hg. I.v. verabreichtes Propranolol (Inderal, 0,3 mg/kg Körpergewicht) verringerte diesen Druck auf 18,8±1,3 mm Hg. Die totale Leichtigkeit des Kammerwasserabflusses an den Kontrollaugen betrug 0,309±0,090 l/mm Hg/min, während sich nach Verabreichung von Propranolol dieser Wert auf 0,237 ±0,083 l/mm Hg/min veränderte. Die Kammerwasserproduktion in den Kontrollaugen betrug 2,16±0,78 l/min. Nach Verabreichung von Propranolol ging sie auf 1,15±0,64 l/min zurück. Die Differenzen erwiesen sich als statistisch signifikant. Die Abnahme der Abflußleichtigkeit erscheint den Daten nach geringer als die Abnahme der Kammerwasserproduktion. Dadurch erklärt sich die Verringerung des intraocularen Druckes. Aufgrund des Vergleiches der verschiedenen und von einander abweichenden Literaturangaben vermuten die Verfasser, daß das Propranolol außer der tonusverringernden Wirkung auf die -adrenergen Receptoren auch noch einen anderen Wirkungsmechanismus entfalten kann.

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Intraocular pressure and circulation of aqueous humour in rabbit eyes following intravenous administration of propranolol (Inderal^®)

Summary The intraocular pressure of rabbits under urethan anaesthesia was found to be 20.8±2.4 mm Hg. 0.3 mg/kg body weight propranolol given intravenously lowered intraocular pressure to 18.8±1.3 mm Hg. The total facility of outflow from control eyes examined at constant pressures of perfusion was 0.309 ±0.09 l/mm Hg/min, which was reduced to 0.237±0.08 l/mm Hg/min by propranolol given systemically. The formation of aqueous humor in the control eyes was 2.16±0.78 l/min, which was diminished to 1.15±0.64 l/min by propranolol. The differences are statistically significant. The decrease in facility of outflow is smaller than the decrease in formation of aqueous humour, which accounts for the lower intraocular pressure. On the basis of the various and gently differing data in the literature it is assumed that propranolol may have some other mode of action in addition to its -adrenolytic effect on receptors.

     

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.

     

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.     

The routes for bulk drainage of aqueous humour in rabbits with and without cyclodialysis

Summary The bulk drainage of aqueous humour into the general circulation and into the orbital tissues was studied with ¹³¹I-labelled albumin and red dextran (molecular weight 40,000) in rabbits with and without cyclodilaysis.In animals at a normal intraocular pressure of about 20 mm Hg and without an artificial cleft between the anterior chamber and the suprachoroid the rate of aqueous bulk flow into the general circulation was 3.99 ± 0.55 l/min. There seemed to be some outflow also through other routes ending up in the episcleral tissues in the limbus region but less than 0.11 ± 0.02 l/min was drained in that way.Even in dead eyes maintained at an intraocular pressure of 14 mm Hg only negligible quantities of labelled anterior chamber fluid passed into the tissues with bulk flow.In acute experiments in living animals, after a cleft had been opened between the anterior chamber and the suprachoroid without damaging the sclera, the rate of aqueous production was 5.64 ± 0.65 l/min. On an average 54% of the aqueous humour was drained into the suprachoroid from where great amounts penetrated the sclera in part by way of perivascular spaces in part directly through the scleral substance. Before the cleft was produced the facility of outflow was 0.237 ± 0.038 l/min per mm Hg, afterwards it was on an average 0.505 ± 0.092 l/min per mm Hg higher.

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Zusammenfassung Der bulk Abfluß von Kammerwasser in den Blutstrom und in die Gewebe der Orbita wurde in normalen und cyclodialysierten Kaninchen mit ¹³¹I-Albumin and rotem Dextran (Molekulargewicht 40,000) studiert. In Tieren mit normalem intraocularen Druck (20 mm Hg) war der Abfluß ins Blut 3.99 ± 0.55 l/Min. Es gab wahrscheinlich auch einen Abfluß in die Gewebe, aber dieser Abfluß war geringer als 0.11 ± 0.02 l/Min. Auch in toten, perfundierten, Augen gab es bei einem intraocularen Druck von 14 mm Hg nur einen sehr geringen Abfluß in die Gewebe.Nachdem in akuten Experimenten ein Spalt zwischen der Vorderkammer und dem Suprachoroidalraum geöffnet war, war die Kammerwasserproduktion 5.64 ± 0.65 l/Min. Durchschnittlich 54% davon wurden zum Suprachoroidalraum drainiert, von wo große Mengen die Sklera zum Teil durch perivaskulare Spatien, zum Teil direkt durch die Skleralsubstanz durchsetzten. Bevor der Spalt geöffnet wurde, war die Abflußfazilität 0.237 ± 0.038 l/Min per mm Hg, nachher war sie um 0.505 ± 0.092 l/Min per mm Hg gesteigert.

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Résumé Le bulk drainage d'humeur aqueuse dans la circulation générale et dans les tissues orbitaux était étudié avec d'albumine marquée par ¹³¹I et de dextrane rouge (poids moléculaire 40,000) chez des lapins avec et sans cyclodialyse. Chez des animaux avec une pression intraoculaire normale d'environ 20 mm Hg et sans une communication artificielle entre la chambre antérieure et la suprachoroïde la vitesse du bulk flux aqueux dans la circulation générale était 3.99 ± 0.55 l/min. Il semblait avoir quelque flux aussi par d'autres voies directement dans le tissue épiscléral dans la région limbale; mais moins que 0.11 ± 0.02 l/min. était drainé ainsi.Même dans des yeux morts maintenus sous une pression intraoculaire de 14 mm Hg seulement des quantités insignifiantes d'humeur aqueuse marquée filtraient de la chambre antérieure dans le tissu épiscléral comme bulk flux. Dans des expériences aiguëes avec des animaux vivants, après avoir fait une ouverture entre la chambre antérieure et la suprachoroïde sans blesser la sclérotique, le débit de l'humeur aqueuse était 5.64 ± 0.65 l/min. En moyenne 54% de l'humeur aqueuse étaient drainés dans la suprachoroïde, et de là partiellement par des espaces périvasculaires partiellement par la substance sclérotique. Avant que l'ouverture était créée la facilité du flux était 0.237 ± 0.038 l/min per mm Hg, après elle était en moyenne 0.505 ± 0.092 l/min per mm Hg plus haut.

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Department of Pharmacology, University of Uppsala.     

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.     

Methods of visual acuity determination with the spatial frequency sweep visual evoked potential

Purpose The spatial frequency sweep visual evoked potential (sVEP) is used to rapidly determine visual acuity in children or non-responsive patients. Two techniques have been used to separate signal from noise: (1) the 95% confidence interval for the signal amplitude (95% CI) or (2) the amplitude of a Fourier frequency adjacent to 2×the signal frequency (DFT). The purpose of this study is to determine if there is a significant difference in acuity estimates with these techniques.Methods Ten normal subjects (approximately 0.00logMAR acuity) and 11 patients with decreased visual acuity took part in this project. Stimulus production and data analysis were done with an Enfant 4010 (Neuroscientific Corp). Standard VEP recording techniques were employed. The stimulus was a horizontal-oriented, sine wave grating that swept up the spatial frequency spectrum (contrast 80%, temporal reversal rate 7.5Hz). Sweeps were repeated until the confidence intervals for the data were no longer decreasing. The Bailey LovielogMAR chart was used to determine visual acuity. A line was fit to the high spatial frequency data using either the 95% CI or the DFT as the noise estimate. By using these linear equations, acuity estimates were obtained at 0, 1, and 2V signal amplitudes.Results The average logMAR acuity for the subjects with normal acuity was –0.06±0.070 (SD). The sVEP acuity estimates were 0.08±0.098, 0.18±0.092, and 0.33±0.195 (0, 1, and 2V extrapolations) with the 95% CI used as noise and 0.07±0.100, 0.18±0.103, and 0.33±0.202 (0, 1, and 2V extrapolations) with the DFT used as noise. By using the average noise from the Fourier frequency as the extrapolation level, the acuity was 0.10±0.098logMAR. The averagelogMAR acuity for the subjects with decreased visual acuity was 0.67±0.306 (SD). The sVEP acuity estimates were 0.53±0.175, 0.66±0.171, and 0.88±0.295 (0, 1, and 2V extrapolations) with the 95% CI used as noise and 0.53±0.179, 0.65±0.176, and 0.86±0.268 (0, 1, and 2V extrapolations) with the DFT used as noise. By using the average noise from the Fourier frequency as the extrapolation level, the acuity was 0.57±0.186logMAR. No significant difference was found between the two acuity estimate techniques for all of the subjects (repeated measures ANOVA, p=0.16, F₂₀=2.131). The sVEP estimates of acuity to the 0V and noise levels were not significantly different from the logMAR acuity (paired t-test, all p values >0.05).Conclusions The results indicate that the sVEP acuity does not depend on the noise estimation technique. In agreement with prior studies, the sVEP acuity underestimates the logMAR acuity in normally sighted individuals by about an octave.     

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.     

Measurement of basal tear turnover using a standardized protocol

Background: The aim of this study was to compare basal tear turnover values of healthy volunteers in different countries. Methods: Healthy volunteers aged between 20 and 70 years were selected in three European cities. Basal tear turnover values were calculated according to a standardized protocol from the decay of the fluorescein concentration in tears after instillation of 1-l drop of fluorescein in the conjunctival sac. Fluorescein concentration was measured with identical commercial fluorophotometers. A monoexponential decay of fluorescein was assumed to represent basal tear flow. Results: The mean tear turnover values were 13.1%/ min ± 4.6 SD (n=4), 16.0%/ min ± 5.2 SD (n=24) and 17.5%/ min ± 3.4 SD (n = 20) in Clermont-Ferrand (France), Leiden (The Netherlands) and Madrid (Spain), respectively. The differences between the values were not significant (Mann-Whitney test P > 0.09). Conclusions: The tear turnover in the different cities was similar. The methods used were simple and the software easy to use.Concerted Action, supported in part by the European Commission, on Ocular Fluorometry: Standardization and Instrumentation Development of the 4th European Community Medical and Health Research Programme (No. MR 4*/0314/P).     

Ciliary body toxicity of cyclosporin A and octreotide acetate in rabbit eyes: a comparison with mitomycin C and 5-fluorouracil

Purpose To compare the toxicities of cyclosporin A, octreotide acetate, mitomycin C and 5-fluorouracil to the ciliary body.Method We applied sponges soaked in these compounds to the open scleras of rabbit eyes. Histopathological specimens were obtained from the operation site and at 180° from it on the 14th day after surgery.Results Mean ciliary epithelial thickness in the study groups was as follows: 12.29±2.69 m in group 1 (mitomycin C), 13.85±4.56 m in group 2 (5-fluorouracil), 17.71±3.09 m in group 3 (cyclosporin A), 11.64±2.92 m in group 4 (octreotide acetate), 11.92±2.89 m in group 5 (topically applied octreotide acetate) and 21.85±4.29 m in group 6 (control). The ciliary epithelial thickness in groups 1, 2, 4 and 5 was statistically different from that in the control group. Intracellular vacuolisation and degenerative changes of the non-pigmented epithelium, and pigment loss of the pigmented epithelium, were found mostly in group 1 and moderately in group 2 and 3.Conclusion Octreotide acetate and cyclosporin A are less toxic alternatives to mitomycin C and 5-fluorouracil in glaucoma filtration surgery.     

„Aberrante“ Ganglienzellen in der Wurzel des Nervus oculomotorius des Menschen

Zusammenfassung 56 Nn. oculomotorii von 37 Erwachsenen (mittleres Alter 66 Jahre) wurden untersucht. In 25 der 56 Nerven (44,6%) bzw. bei 19 der 37 Erwachsenen (51%) wurden insgesamt 243 Ganglienzellen in der Nervenwurzel gefunden. Der mittlere Durchmesser von 100 Zellen betrug 43.7 (range: 26,8–69,8 ; größte Frequenz bei 35–45 ). Histologisch ähneln sie den sensiblen Zellen eines Spinalganglions. Es wird die Frage aufgeworfen, ob es sich um aberrante Ganglienzellen oder ein Zellsystem handelt.Der Befund eines sensiblen Ganglion mit 46 Ganglienzellen im Verlauf des N. trochlearis wird erwähnt.

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Aberrant ganglion cells in the human ocullomotor nerve

Summary 56 oculomotor nerves of 37 adult men (mean age 66 years) were examined. A total amount of 243 nerve cells were counted in 25 nerves (44.6%) that is to say in 19 men (51%). The mean diameter of 100 cells was 43.7 (range: 26.8–69.8 ,). The diameter of most of the cells fell between 35 to 45 . Histologically they look like sensory cells of a spinal ganglion. The question arises, whether these neurones represent aberrant cells or an independent neuronal grouping.The finding of a sensory ganglion in the course of the trochlear nerve with 46 nerve cells in it is mentioned.

     

Experimental evaluation of online optical coherence pachymetry for corneal refractive surgery

Purpose Online optical coherence pachymetry (OCP) allows to monitor central changes of the corneal cross section intraoperatively. In this experimental evaluation the validity of the optical measurements for corneal refractive surgery was assessed.Methods Online OCP based on low-coherence interferometry with a wavelength of 1310 nm and a measurement frequency of 74 Hz was directly integrated in a clinical excimer laser. In 16 patients the central corneal thickness was measured with online OCP and ultrasound pachymetry (US). Furthermore, the ablation characteristics were assessed in corneoscleral discs unsuitable for transplantation (n=12) and PMMA samples (n=18).Results Online OCP was possible in all patients and materials studied. The mean central corneal thickness was 537±31 m (OCP) and 546±33 m (US). The corneal reproducibility was ±4.3 m (coefficient of variation [CV] 0.8%) with online OCP and ±3.7 m (CV 0.68%) with US. The reproducibility in PMMA samples was ±1.0 m (CV 0.16%). There was a significant correlation between online OCP and US measurements (r=0.93, P<0.001). The mean difference was 9.1 m or 1.69% (P=0.01), and the limits of agreement (95% CI) ranged from –15 m to 33 m. There was a significant linear relationship (r=0,95; P<0.001) between the calculated and the optically determined ablation depth with online OCP. Also ablation depth measurements in PMMA correlated positively with spectrophotometric values (r=0.98; P<0.001).Conclusion In this experimental evaluation, online OCP revealed to be a precise and reproducible method to assess the central corneal thickness and its changes intraoperatively. This could be important to monitor incisional and excimer laser-based corneal refractive procedures, such as PRK or LASIK.The authors have no commercial, proprietary or financial interest in any research or devices described in the presented study     

Does aqueous humor secretion decrease with age?

Aqueous humor flow was calculated during day-time in 148 healthy volunteers and 75 older patients using the Fluorotron Master II anterior chamber protocol (Coherent, Palo Alto, USA). Healthy volunteers as well as patients had no history of ocular pathology, surgery or laser treatment. Slitlamp examination revealed no ocular pathology. Hypertension, diabetes, local and systemic drug therapy, neoplasia, kidney or liver disease, contact lens and ocular trauma were excluded. Mean age of volunteers was 26.5±3.8 years; age of patients: 65.5±10.5 years. Aqueous humor flow during day-time in healthy volunteers in the OD: (mean± s.d.) 2.26±1.0l/min, in the OS: 2.17±1.0l/min. Correlation coefficient: r=0.8. The mean aqueous humor flow in the older patients during day-time: OD: 1.91±1.1 l/min, OS: 1.86±1.1 l/min. Correlation coefficient: r=0.54. The Mann-Whitney-U-test revealed a significant difference when comparing the right eyes of healthy volunteers with the right eyes of patients (p<0.01). When comparing all left eyes the difference is also significant (p=0.01). The results of the study underline, that the mean aqueous humor secretion does significantly decrease with age. However, the data show that there is only a slight decrease of flow of approximately 2.5% per decade. From the clinical point of view it should be concluded, that although the aqueous humor secretion does decrease with age, this is not of clinical importance, even in cases of glaucoma surgery. Afterall we still don't know, whether this decrease of aqueous humor flow is caused by a decrease of the pigmented and non-pigmented epithelium cells, or via a decrease of outflow facility, or via a decrease of CNS-stimulation.     

Determination of the pseudofacility by fluorophotometry in the human eye

Purpose: Pseudofacility (decrease in aqueous humor flow in response to increase in the intraocular pressure (IOP)) has been evaluated in animals and in humans by a combination of different techniques that seriously alter the ocular physiology, such as the cannulation of the eyeballs, use of radioactive isotopes, perilimbic suction cups or tonography. Very different results have been obtained. Our objective is to relate the value of the aqueous humor flow in humans (as measured by fluorometry) with IOP. In order to obtain the widest range of IOP possible, we have performed this study in both normal as well as glaucoma patients. Methods: 48 eyes were studied, corresponding to 31 subjects (mean age 58 ± 14 years). Of these, 21 corresponded to normal subjects and 27 to glaucoma patients. The aqueous humor flow (F) was determined by fluorophotometry (Protocol of Yablonsky) and the IOP was measured thereafter. Results: The mean value of F was 2.1 ± 0.5 l/min for healthy eyes and 2.2 ± 0.7 l/min for glaucoma-affected eyes. The values were not different (p > 0.1). The mean value of the IOP was 15.3 ±3.1 mmHg in the normal population and 22.1 ± 4.3 mmHg in the glaucoma patients. A linear relationship between F and IOP was found (r = – 0.41, p < 0.05, decrease in F = 0.081 l min^–1 mmHg^–1). Conclusions: The value of the pseudofacility in the humans can be estimated at 0.081 l min^–1 mmHg^–1, which constitutes 27% of the total outflow facility. This figure also makes it possible to estimate the role of the ultrafiltration in blood in the production of the aqueous humor since it is assumed that active secretion is pressure-independent. The results obtained are concordant with a secondary but no unimportant role of the plasmatic ultrafiltration with respect to the active secretion.     

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 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.     

Pulsatile Ocular Blood Flow: Changes Associated with Scleral Buckling Procedures

Purpose To determine the changes in the pulse amplitude (PA) and the pulsatile ocular blood flow (POBF) after scleral buckling (SB).Methods Retrospectively, we studied 24 patients (average age, 52 years) who had undergone SB to repair a retinal detachment in one eye. The patients were divided into two groups: those in whom SB had been performed less than 6 months earlier (n = 10), and those in whom the procedure had been performed more than 6 months previously (n = 14). In each group, the PA and the POBF were determined with a computerized tonometry system, and the values in the SB eyes were compared with those in the control fellow eyes.Results Within 6 months postoperatively, the mean PA in the SB eyes (0.66 ± 0.30mmHg) was significantly lower than that in the control eyes (1.43 ± 0.34mmHg; P < 0.05). The mean POBF in the SB eyes (349.5 ± 154.1µl/min) was also significantly lower than that in the control eyes (631.0 ± 226.6µl/min; P < 0.05). After more than 6 months postoperatively, there were no significant differences in the PA or the POBF between the SB eyes (1.08 ± 0.49mmHg and 612.4 ± 341.2µl/min, respectively) and the control eyes (1.50 ± 0.51mmHg and 589.5 ± 278.4µl/min, respectively).Conclusions These results indicate that the choroidal blood flow decreases after SB but returns to normal levels after 6 months. Jpn J Ophthalmol 2005;49:162–165 © Japanese Ophthalmological Society 2005     

Count and density of human retinal photoreceptors

This investigation was directed at determining the count and regional distribution of photoreceptors in the eyes of 21 human cornea donors aged between 2 and 90 years. Mean count of rods was 60 123 000 ±12907000, and mean cone count was 3173000 ± 555000. Determined 40 m away from the foveola, cone density measured 125 500 cones/mm². Extrapolating the distribution curve, cone concentration in the foveal center can be assumed to be about 150 000 cells/mm² to 180 000 cones/mm². Towards the retinal periphery, cone density decreased from 6000 cones/mm² at a distance of 1.5 mm from the fovea to 2500 cells/mm² close to the ora serrata. Comparing different fundus regions, cone concentration was significantly highest in the nasal region. Cone diameter increased from the center towards the periphery. At a distance of 40 m away from the foveola, it measured about 3.3 m, and in the outer retinal regions about 10 m Rod density was highest in a ring-like area at a distance of about 3–5 mm from the foveola with a mean of 72 246 ± 17 295 cells/mm². Rod density peaked at 150 000 rods/mm². It decreased towards the retinal periphery to 30 000–40 000 rods/mm². Rod diameter increased from 3 m at the area with the highest rod density to 5.5 m in the periphery. The hexagonal rod and cone inner segments were regularly arranged in a honey-comb fashion.Supported by the Deutsche Forschungsgemeinschaft (Klinische Forschergruppe Glaukome Na 55/6-1/Jo) Correspondence to: J.B. Jonas     

A comparative study of the effects of argon and diode laser photocoagulation on retinal oxygenation

Background: The purpose of this study was to compare the effects of diode and argon laser photocoagulation (DLP and ALP) on the preretinal oxygen tension (P_O2): (1) directly over photocoagulated retina and (2) in between laser lesions. Methods: DLP or ALP was applied to avascular rabbit retina to produce grade II lesions. On the day of the oxygen measurement, a droplet of perfluorotributylamine was placed into the preretinal vitreous space over the lasered area of retina and the steady-state P_O2 was measured in normoxic animals using¹⁹F magnetic resonance spectroscopy. To determine the P_O2 directly over laser lesions, small (5l) droplets were placed over large ( 4 mm X 5 mm), confluent areas of treatment (burn area 95% of the treated retinal surface area). To determine the P_O2 in between laser lesions, a larger (10 –l) droplet was placed over a field of scatter photocoagulation (burn area 30% of the treated retinal surface area). The theoretical basis for this approach is discussed. Results: Untreated eyes had a preretinal P_O2 of 22±9 mm Hg (mean ± SD,n=15 eyes). The preretinal P_O2 was significantly higher over confluent, 12-day-old ALP or DLP lesions (51+13 mm Hg,n=8 eyes;P<0.01) compared to untreated eyes. However, at that time, DLP lesions had significantly higher P_O2 values (60±13 mm Hg,n=4 eyes) than did ALP lesions (42±6 mm Hg,n=4 eyes;P=0.04). The preretinal space in between laser lesions generally showed no significant increase in P_O2 (P>0.05) over controls on post-treatment days 1, 5, 14 and 47. The only exception was in the DLP group of eyes, in which a significant increase in P_O2 over untreated or ALP-treated eyes occurred on post-treatment day 5 (41±7 mm Hg,n=5 eyes;P=0.01). Over photocoagulation lesions in this study, DLP produced a greater increase in preretinal P_O2 compared to control values than did ALP. Conclusions: These results support the use of DLP as an alternative to ALP for the treatment of retinal vascular diseases in which hypoxia is suspected to play a role.