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.

     

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.     

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.     

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     

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.     

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.     

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.     

Pattern electroretinogram for monitoring the efficacy of intravitreal triamcinolone injection in diabetic macular edema

Purpose: To investigate the efficacy of intravitreal triamcinolone (IVT) by evaluation of pattern electroretinogram (PERG) in diabetic patients with clinically significant macular edema (CSME). Methods: Forty eyes of 40 diabetic patients were treated with 8 mg of IVT injection as primary therapy for CSME. The main outcome measures included best-corrected visual acuity, fundus fluorescein angiography, P₅₀ amplitudes of pattern electroretinogram (PERG) and intraocular pressures before and after injection. Results: The mean follow-up time was 6.1 months. Mean visual acuity improved significantly from a mean LogMAR value of 1.14 ± 0.16 at baseline to a maximum of 0.73 ± 0.30. The mean baseline P₅₀ amplitude of PERG before intravitreal injection was 1.5 ± 0.9 V. After the treatment, it was 2.l ± 1.1 V at 1-month, 2.4 ± 1.0 V at 3-month and 2.1 ± 0.9 V at last visit and the differences were significant when compared with baseline values (for each, p < 0.001). Temporary increases in intraocular pressures were controlled with topical antiglaucomatous medications, if required. Conclusion: IVT injection provides rapid improvement in visual acuity of diabetic patients with CSME that has been supported by P₅₀ amplitudes of PERG. P₅₀ amplitudes of PERG may be used as novel predictive value in the evaluation of the effectiveness of IVT injection.     

Effects of retinal dopamine depletion on the rabbit electroretinogram

This study evaluated the effects of intravitreal injections of 300 g of 6-hydroxydopamine (6-OHDA) on electroretinogram (ERG) amplitudes and implicit response times of adult pigmented rabbits. One eye was injected intravitreally with 300 g 6-OHDA and 600 g ascorbic acid in a 0.3 ml 0.9% NaCl solution; the fellow eye received a similar solution containing only 600 g ascorbic acid. Following this treatment ERG recordings were performed at 1, 4, and 7 days. After the last recordings, animals were sacrificed and retinas were isolated for biochemical analyses. Significant and progressive reductions in retinal concentrations of dopamine (DA) and its main metabolites homovanilic acid (HVA), and dihydroxyphenylacetic acid (DOPAC) were found in treated retinas. Concentrations of norepinephrine (NE), serotonin (5HT), and 5 hydroxyindoleacetic acid (5-HIAA) were not affected, thus demonstrating the specific neurotoxic action of 6-OHDA on retinal dopaminergic neurons. Concurrently, significant increases in ERG a- and b-wave amplitudes as well as in implicit response times were observed. These electrophysiological changes were progressive reaching a maximum 7 days after intravitreal injections. Changes in b-wave amplitudes and response times were more pronounced at low intensities of stimulation. These results clearly show that, in rabbits, selective decreases in retinal DA concentrations result in pronounced ERG changes, which offer additional evidence supporting a role for this transmitter in lateral inhibition in the retina.This work was supported by MRC research Grants No. MT2593 and DG284.     

Die Latenzzeit (retino-thalamo-cortical) beim Kaninchen bei Reizung mit energiegleichem verschiedenfarbigem Licht

Zusammenfassung Bei Reizung des Kaninchenauges mit energiegleichen Lichtern verschiedener Spektralbereiche zeigte sich, daß nur mit Rotlicht _max 641 m kein Elektroretinogramm und keine spezifischen Aktionspotentiale des Corpus geniculatum laterale und der Sehrinde abzuleiten sind.Gleiche Latenzzeiten der Augen- und Gehirnaktionspotentiale ergeben sich bei Anwendung von Lichtreizen gleicher Energie, 1,7·10^–2 W, im kurzwelligeren Spektralbereich (_max 479 m blau, 538 m grün, 585 m gelb).Die Feststellung, daß kurze Einzellichtreize eines Spektralbereiches über 600 m gleicher Energie am Auge und Gehirn keine Aktionspotentiale erstehen lassen, legt nahe, daß Rotlicht beim Kaninchen keinen Seheindruck hinterläßt.Mit 7 TextabildungenDie Untersuchungen wurden mit freundlicher Unterstützung der Deutschen Forschungsgemeinschaft durchgeführt.     

Nontoxic concentration of amphotericin B for intravitreal use — evaluated by in vitro ERG

Amphotericin B (AMPH)-induced changes of the electroretinogram (ERG) were studied in the in vitro eye-cup of the albino rabbit. The a-wave, b-wave, oscillatory potentials and c-wave were not changed by 1 M AMPH, and these all were slightly suppressed by 5 M AMPH. These changes were mostly reversible. The b-wave and oscillatory potentials were greatly suppressed by 50 M AMPH. These changes were only partially reversible 75 minutes after re-perfusion without AMPH. Address for offprints Kazuo Kawasaki, M.D., Department of Ophthalmology Kanazawa University School of Medicine, 13-1 Takara-machi, Kanazawa, 920 Japan.     

Effects of β-agonists on b- and c-waves implicit for adrenergic mechanisms in cat retina

Nylidrin (buphenine) is a -adrenergic agonist known to dilate peripheral vessels and used therapeutically in retinal degeneration and glaucoma. We studied retinal function under -agonists in arterially perfused cat eyes and observed a dose-dependent, reversible increase in b-wave amplitude and a decrease in c-wave amplitude in concentrations from 4.5 to 120M. A half maximal response was obtained at 40 to 50M. The optic nerve response to light showed dose-dependent reversible changes under nylidrin. Standing potential, light peak, intraocular pressure, vascular resistance, and diameter of or retinal vessels showed no consistent changes under nylidrin.The effects were inhibited by each of the -blocking agents propranolol, ICI 118, and oxprenolol (in sequence of decreasing potency).Another potent ₂-agonist, clenbuterol, was used to determine the extent to which the responses to nylidrin were due to -receptor-mediated action. Clenbuterol had similar effects on the b-wave and optic nerve response at slightly higher concentrations (30–200 M) but more variable effects on the c-wave.The data are interpreted as functional evidence that -adrenergic mechanisms are involved in retinal signal processing. This concept is corroborated by identification of -adrenergic binding sites in cat retina (Bruinink et al., 1986).     

Die fixation des menschlichen auges

Zusammenfassung Während der Fixation wird ein Fixationsfeld beansprucht im Ausmaße von 100 , d.i. das Bereich der dünnsten und höchsten Zapfen, von 1 Durchmesser. In diesem Fixationsfeld ist der Fixationspunkt der Willkür entzogen. Während der strengen Fixation macht das Auge bekanntlich dreierlei Bewegungen, von denen die schnellen ebenfalls in einem Feld von 100 Durchmesser liegen. Das maculopapilläre Bündel führt die Erregungen aus dem auch in Bezug auf das Ableitungssystem ausgezeichneten Fixationsfeld ab. Die Sehschärfe unterschreitet weit die Grenze von 1 , was auf die Synapsenfunktionen der Retina, des Corpus geniculatum laterale und auf die cortikalen Bezirke zurückgeführt wird.

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Summary During fixation a fixation-field of 100 diameter is required, corresponding to the area of the thinnest and longest cones of 1 diameter. Within this fixation-field the position of the fixation point is involuntary and at random. The fast component of the three eye movements during fixation also covers a field of 100 diameter. Impulses from this field are conducted via the maculo-papillary bundle. The visual acuity is far below the limit of 1 ; this is attributed to the synaptic function of the retina, the lateral geniculate body and the cortical areas.

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Résumé Pendant la fixation un champ de 100 se trouve occupé, c'est-à-dire la région des cônes les plus hauts et les plus minces, qui ont pour diamètre 1 . Dans le champ de fixation le point de fixation n'est plus soumis à la volonté. Pendant la fixation précise l'oeil fait trois sortes de mouvements; les plus rapides d'entre eux intéressent aussi un champ d'un diamètre de 100 . Le faisceau papillo-maculaire conduit les influx nerveux hors du champ de fixation. L'acuité visuelle descend bien en-dessous de 1 . Ce fait est attribué aux fonctions synaptiques de la rétine, du corps genouillé externe et des régions corticales.

     

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     

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.     

The effects of β-adrenergic agonists on cone systems in the cat eye

The effects of the -adrenergic agonist nylidrin and the ₂-adrenergic agonist clenbuterol on electroretinogram and optic nerve response were studied in the isolated and arterially perfused, light-adapted cat eye. Two cone mechanisms, short wavelength-sensitive and long wavelength-sensitive, were functionally separated by means of intense yellow adaptation. A reversible increase in b-wave amplitude in response to nylidrin or clenbuterol was observed for the cone systems. Both drugs also caused a reversible alteration in configuration of the optic nerve response, mainly a depression of the late components related in time to the changes in the electroretinogram. These observations suggest that -adrenergic mechanisms are involved in cone systems. The greater increase in b-wave amplitude on 558-nm stimulation and preliminary evidence for greater increase in sensitivity observed in the V-log I function compared with 439 nm further suggest that the short and long wavelength cone systems are affected differently by -adrenergic agonists.     

Electrophysiologic characteristics of human and rat retinas in vitro

To promote studies on the human retina, we investigated the survival of function in postmortem specimens. Visual pigment has been regenerated in normal human retinas, 5 to 58 hours postmorten, by exposure to retinal isomers in the dark. Levels from 0.1 to 0.41 nmol/ mg protein were reached. Photoresponses were obtained in 9 of 13 retinas: P III maximum amplitudes ranged from 20–398 V and thresholds, taking the criterion amplitude as 3 V, ranged from 8.8–1340 quanta/m ². In three cases, the b-wave was also seen. The P III amplitude vs. log intensity curves gave values of n between 0.6 and 1.0, and (the stimulus intensity for a half maximal response) between 132–3700 quanta/m². Recovery of sensitivity did not always correspond to that of maximum response.     

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.     

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.