Surgical risk factors for severe postoperative proliferative vitreoretinopathy (PVR) in retinal detachment with grade B PVR

Background: Previous studies have shown that grade B proliferative vitreoretinopathy (PVR) is a considerable risk factor for the development of severe postoperative PVR. We conducted a prospective study to elucidate which surgical procedures used in retinal detachment management may stimulate the PVR process in such eyes. Materials and methods: The study included 156 eyes of 152 consecutive patients with rhegmatogenous retinal detachment complicated by grade B PVR referred before any failed surgery and operated on between 1983 and 1993. The parameters evaluated by multivariate statistical analysis included the cumulative circumferential extent of the retinal tears, the extent of the scleral buckle, gas injection, vitrectomy, the method used for retinopexy, and the time of surgical management during the period of the study. Results: The incidence of severe postoperative PVR was 25.8% in eyes managed with cryotreatment versus 2.2% in eyes managed with argon laser photocoagulation (P=0.001). The rate of severe postoperative PVR was not influenced by the other surgical variables. Conclusion: We conclude that cryotherapy may be a risk factor for the development of severe postoperative PVR in retinal detachments associated with grade B PVR.     

Indocyanine green and fluorescein angiography of surgically excised macular choroidal neovascularizations: correlations with histopathologic and ultrastructural findings

Background: Informations are expected from the histopathological study of surgically excised choroidal neovascular membranes (CNMs), particularly in relation to the angiographic aspects of vascular architecture. Methods: Fluorescein and indocyanine green (ICG) angiograms were studied together with the histopathological features of 12 surgically excised subfoveal CNMs in eyes affected by age-related macular degeneration (ARMD). Results: Instead of the early and delayed diffuse hyperfluorescence secondary to CNMs observed on fluorescein angiography (seven were well defined, five scar evolved), ICG revealed (a) very early hypofluorescence of the membrane bulk over the fluorescence of the outer choroidal vascular bed and (b) late hyperfluorescence gradually increasing and partially defining the border of membranes. CNMs with well-defined hyperfluorescent aspects were characterized by fibrovascular bulk lined on one side by retinal pigment epithelium. Fibrosis reaction predominated over the vascular components in scar-evolved membranes. Conclusions: Fluorescein and ICG angiographic differences in the appearance of CNMs could depend on (a) the morphological structure and size of the CNM (b) its location within the chorioretinal layers and (c) different molecular characteristics of the dyes used.     

Quantitative analysis of immunogold labellings of collagen types I,III, IV and VI in healthy and pathological human corneas

Background: We studied the distribution of collagen types I, III, IV and VI in one healthy human cornea and in seven pathological human corneas, in which the disorders were three cases of pseudophakic bullous keratopathy (two severe, one moderate) and one case each of stage IV keratoconus, chronic ulcer, vascularized cornea and disciform keratitis. Methods: Transmission electron microscopy examinations were performed on post-embedding immunogold-labelled sections. The staining was evaluated by gold particle count in the different tissues. The presence or absence of a given antigen was determined by statistical analysis, using a d-value test. Results: Our results on healthy corneal tissues corroborate the data available from previous studies, except for collagen type VI, which we found to be absent in Bowman's layer. In pathological corneas with a collagenous layer posterior to Descemet's membrane, collagen types I, III and especially IV were detected in this collagenous layer. Collagen types I, III and VI were detected in the anterior healed stroma of other pathological corneas, except for the keratoconus cornea, in which intense collagen III staining was observed. Conclusion: The presence of collagen types I and III in the posterior collagenous layer of our pseudophakic bullous keratopathy corneas suggests that this layer corresponds to scar tissue secreted by stimulated endothelial cells.     

Immunohistochemical evaluation of the integrity of the blood-aqueous barrier in normal and rubeotic human eyes

Background: The integrity of the blood-aqueous barrier (BAB) was analyzed using an immunohistochemical technique for the demonstration of albumin. Methods: Paraffin sections of 36 normal eyes obtained from eye banks or at autopsy (mean age 62.8 ± 15.2 years) and 46 eyes with marked iris neovascularization (mean age 54.6 ± 25.3 years) were formalin-fixed and examined using rabbit anti-human albumin. Results: In normal eyes, albumin staining was found in the iris stroma inside and outside the iris vessels but was not detected across the anterior iris border; albumin was present in the anterior chamber in one eye, but not internal to the nonpigmented ciliary epithelium. In rubeotic eyes, albumin staining extended along the anteri or iris in all 46 cases; albumin was demonstrated in the anterior chamber in 31 eyes and along to the nonpigmented ciliary epithelium in 13 eyes. Differences between normal and rubeotic eyes were significant for intensity of albumin staining in the iris stroma and for presence of albumin along the anterior iris, within the anterior chamber, and along the ciliary epithelium (P < 0.001, ² test). Conclusion: Our findings indicate that the BAB may be less resistant to leakage in the iris stroma than at the ciliary epithelium. BAB breakdown in rubeotic eyes occurred mainly in the iris; the ciliary epithelium was much less involved. Immunohistochemical staining for albumin appears to be useful for evaluating the integrity of the BAB in human pathologic specimens.     

Galactose-containing glycoconjugates of the iris,the aqueous outflow passages and the cornea in capsular glaucoma

Background: The aim of the study was to compare galactose-containing glycoconjugates of the iris, the aqueous outflow pas sages and the cornea with exfoliation material in capsular glaucoma. Methods: Six formalinfixed, paraffin-embedded human eyes with capsular glaucoma and six control eyes were studied by using a panel of 11 biotinylated lectins to galactose- and N-acetylgalactosamine-containing glycoconjugates. Results: The Gal ( 3) GaINAc-reactive lectins peanut agglutinin (PNA) and Bauhinia purpurea alba agglutinin (BPA) and the Gal (14)GlcNAc-reactive lectins Ricinus communis agglutinin (RCA-I) and Phaseolus vulgaris erythroagglutinin (PHA-E) gave the strongest label with exfoliation material. Lectin binding to the iris was variable. The binding of PNA, BPA, RCA-I, Erythrina cristagalli agglutinin (ECA), PHA-E and Glycine max agglutinin (SBA) to the subendothelial region of iris blood vessels closely resembled their binding to exfoliation material. RCA-I and PHA-E bound moderately to the aqueous outflow passages. The surface of the corneal epithelium showed positive reaction with most lectins studied, but the keratocytes reacted with RCA-I and PHA-E only. Neuraminidase pretreatment generally increased the reaction intensity. Conclusions: The findings suggest that the glycoconjugate composition of exfoliation material in the classical locations along the anterior and posterior chamber closely resembles that in the subendothelial region of iris blood vessels.The authors have no financial interest in any product or process mentioned herein     

Oxidative reactions in the tear fluid of patients suffering from dry eyes

Purpose: To evaluate whether products of oxidative and inflammatory reactions are detectable in the tear fluid of patients suffering from dry eyes. Methods: The tear fluid of 217 patients (397 eyes) was sampled. Criteria for grouping of the patients were (1) basic secretion test (sicca l: BST = 0–5 mm, n = 78 eyes; sicca 2: BST = 6–10 mm, n = 109 eyes) and (2) subjective symptoms (normal BST, burning, foreign body sensations, tearing, dryness of the eyes: n = 78 eyes). One group of healthy patients (normal BST, n = 132 eyes) served as controls. Lipid peroxide levels and myeloperoxidase activity, as parameters for oxidative tissue damage and inflammatory activity, were determined in the tear fluid. Those patients whose consent could be obtained were subjected to the rose bengal test (sicca 1: 56 eyes; sicca 2: 97 eyes; subjective symptoms: 44 eyes; controls: 49 eyes). The correlation between BST and rose bengal test results was calculated. Results: Lipid peroxides were significantly (P < 0.05) higher in the groups sicca 1 and subjective symptoms than in healthy controls, as was the inflammatory activity in groups sicca 1, sicca 2 and subjective symptoms. Additionally, the inflammatory activity in the group sicca 1 was significantly (P < 0.05) higher than in the groups sicca 2 and subjective symptoms. No evidence of a significant correlation between BST and rose bengal test results was observed. Conclusions: Both oxidative tissue damage and polymorphonuclear leukocytes indicating an oxidative potential occur in the tear film of patients suffering from dry eyes. These reactions lead to severe damage of the involved tissue. Free radicals and inflammation may be involved in the pathogenesis or in the self-propagation of the disease.     

Calculation of size and location of autologous ipsilateral rotating keratoplasty

Background: Autologous ipsilateral rotating keratoplasty is a special form of keratoplasty in which a nonprogressive opacification of the centre of the cornea is rotated towards the limbus and the clear peripheral cornea is rotated into the optical axis of the eye. This study was performed to find an equation for calculating the best size and location of the trephine for this special kind of keratoplasty Methods: Geometrical calculations were used to derive the formula Results: We arrived at the following equation for the best diameter of the trephine: diameter _(trephine) = 3/4 diameter(_cornea)–1/2e(e = preoperative distance between corneal centre and nearest edge of opacity covering corneal centre). The postoperative diameter of the optical zone is: 2 × diameter_(trephine) diameter_(cornea). A postoperative clear optical zone of half the corneal diameter is achieved if the opacity just touches but does not extend beyond the corneal centre. For a postoperative optical zone of at least 30% (40%) of the corneal diameter, the opacity is preoperatively not allowed to extend beyond the corneal centre for more than 20% (10%) of the corneal diameter Conclusion: This equation can be used for calculating the optimum size and location of the trephine for autologous ipsilateral rotational keratoplasty. For that purpose it is advisable to take photographs preoperatively.     

Unusual retinal pigment epitheliopathy and choroidopathy in carcinomatosis: A rare case of cancer-associated retinopathy

Background: Cancer-associated retinopathy is a syndrome causing ocular symptoms. It is a rare entity and only a few cases have been reported. Methods: A 67-year-old woman with small-cell endometrial carcinoma suffering from deterioration of visual acuity is presented. Results: The patient presented with extensive mottled changes of the retinal pigment epithelium, accompanied by diffuse subretinal fluid in the posterior pole and exudative retinal detachments inferior in both eyes. Conclusion: This patient suffered from a rare variety of cancer-associated retinopathy.     

Preoperative vitreous hemorrhage associated with rhegmatogenous retinal detachment: a risk factor for postoperative proliferative vitreoretinopathy?

Background: We conducted a prospective clinical study to elucidate the role of preoperative vitreous hemorrhage in the development of postoperative proliferative vitreoretinopathy (PVR) in primary rhegmatogenous retinal detachment. Materials and methods: We prospectively evaluated 409 eyes of 390 patients affected by primary rhegmatogenous retinal detachment referred before any failed attempt to reattach the retina. Single and multiple logistic regression analysis were used to test 14 categories of variables. Results: Postoperative PVR occurred in 48 (11.7% of 409 eyes). Postoperative PVR developed in 41 (11.8%) of the 347 eyes with no preoperative vitreous hemorrhage, and 7 (11.3%) of the 62 eyes with preoperative vitreous hemorrhage (P=0.90). The results of multiple logistic regression analysis showed that only four variables were significant factors which had independently and jointly an effect on the risk of postoperative PVR: (1) 90° or greater circumferential extent of the retinal tears; (2) preoperative PVR grade B; (3) preoperative PVR grade C-D; and (4) the use of cyrotreatment as the method of retinopexy. Conclusion: With the surgical techniques currently used, mild preoperative vitreous hemorrhage is not an independent risk factor for postoperative PVR in primary rhegmatogenous retinal detachment. The role of moderate and severe vitreous hemorrhage remains to be fully evaluated in a larger series of eyes.     

Fundus pulsation measurements in diabetic retinopathy

Background: There is experimental evidence that retinal blood flow is impaired in patients with diabetes mellitus. Much less attention has been paid to choroidal blood flow. Hence it was the aim of the present study to investigate choroidal blood flow in diabetic retinopathy. Methods: A new noninvasive laser interferometric technique was used to measure fundus pulsations in the macula. The fundus pulsation amplitude, which is the maximum distance change between cornea and retina during the cardiac cycle, is a measure of local pulsatile blood flow. The eyes (n = 214) were divided into four groups according to the modified Airlie House classification: (1) no retinopathy (control group), (2) background retinopathy, (3) moderate to severe preproliferative retinopathy, (4) proliferative retinopathy. In 83 eyes of different groups fundus pulsation measurements were repeated after 1–6 weeks. Results: Fundus pulsation amplitudes were significantly smaller in group 4 than in the control group (P < 0.027). The reproducibility of the measurements was high and did not differ among the study groups. Conclusions: Local fundus pulsations in the macula are reduced in proliferative diabetic retinopathy, which is compatible with previous findings of reduced choroidal blood flow in late stages of the disease. Laser interferometric measurement of fundus pulsations is non-contactile, assures optimal comfort for the patient and could be used for the long-term observation of patients with diabetes mellitus.     

Optic disc morphology in myopic primary open-angle glaucoma

Objective: To evaluate the morphology of the optic disc in highly myopic eyes with primary open-angle glaucoma. Methods: Color stereo optic disc photographs of 44 patients with primary open-angle glaucoma and a myopic refractive error exceeding –8 diopters were morphometrically examined and compared with disc photographs of 571 patients with primary open-angle glaucoma and a myopic refractive error of less than –8 diopters. Results: In the highly myopic group, compared to the control group, the optic disc was significantly (P<0.0001) larger, the disc shape was significantly (P<0.0005) more elongated, and the optic cup depth was significantly (P<0.0001) more shallow. The loss of neuroretinal rim was more concentric, and localized retinal nerve fiber layer defects were found significantly less frequently in the highly myopic group than in the control group. In the highly myopic group, zone beta of parapapillary atrophy was significantly (P<0.0001) larger. Conclusion: The optic disc morphology in primary open-angle glaucoma differs significantly between highly myopic eyes and eyes with hyperopia or low to moderate myopia. The highly myopic eyes are characterized by secondary macrodiscs with elongated shape, shallow and concentric disc cupping, large parapapillary atrophy, and low frequency of localized retinal nerve fiber layer defects. Glaucomatous optic nerve damage in highly myopic eyes, compared to eyes with a normal refractive error, is more diffuse than localized.     

Anterior chamber inflammation after transconjunctival cryosurgery

Background: Inflammation caused by transconjunctival cryotherapy for prophylactic retinal detachment surgery was measured in various conditions. Methods: Thirty-four eyes of 28 patients with peripheral retinal lesions predisposing to retinal detachment were studied by laser flare cell meter before and after treatment. Results: The mean flare value for 34 eyes was 4.06 ± 1.45 photon counts/ms before surgery and 5.72 ± 2.52 pc/ms after surgery (p < 0.05). Flare value was elevated at 1, 2, and 3 weeks after treatment, peaking at 2 weeks (p < 0.05), and normal again at 4 weeks. There were no significant differences in flare increase between eyes with and without retinal breaks, eyes with and without limited retinal detachment, eyes with myopia more and less than – 8.0 D, and eyes with a treatment area limited to one quadrant and extending over more than one quadrant. Conclusion: Transconjunctival cryosurgery caused mild inflammation in the anterior chamber of the eye for 3 weeks. The inflammation was not affected by the presence of retinal break or limited retinal detachment, the degree of myopia, or the extent of the treatment area.     

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.     

DNA-based HLA class II postmortem typing: evaluation of different techniques for prospective corneal allografting

Background: The objective of this study was to establish DNA-based HLA-DR postmortem tissue typing techniques in order to improve the quality and quanity of fully HLA-typed corneas for prospective allografting. Methods: Four hundred and thirty-seven cornea donors were investigated. DNA was derived from cultivated retinal pigment epithelial cells by spin column purification or a salting out technique, and from scleral tissue by a very simple boiling method. Donors were typed by hybridization of polymerase chain reaction (PCR) products with sequence-specific oligodesoxynucleotide probes (PCR-SSOP) or by PCR with sequence-specific primers (PCR-SSP). Twenty-two of the donors were pretyped by serology. Results: We observed high concordance (96%) between the results of DNA-based postmortem typing and the serological lymphocytotoxicity test. Furthermore, the distribution of the HLA-DR specificities that were detected correlated well with the distribution in a control population. Conclusions: The results of this study demonstrate that both PCR-SSP and PCR-SSOP allow prospective allocation of HLA class II-matched corneas with high accuracy.     

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.     

Inhibitory effects of plasminogen fragment on experimentally induced neovascularization of rat corneas

Background: Corneal neovascularization plays an important role in the pathogenesis of a number of corneal disorders. Recently a polypeptide was demonstrated, generated by the primary tumor, that inhibited angiogenesis and growth in metastases. This polypeptide is similar to a 38-kDa plasminogen fragment. Methods: We surgically implanted into rat corneal stroma a slow-release ethylene-vinyl-acetate (EVA) copolymer pellet containing basic fibroblast growth factor (bFGF) to induce corneal neovascularization. Then we applied aqueous solution containing plasminogen fragment to the rat cornea in order to observe the degree of inhibition of angiogenesis. Results: In the eyes of control rats, neovascularization from the limbus to the pellet occurred, graded 4+ in all five animals. In plasminogen fragment-treated rats, there was virtually complete inhibition of the neovascular response to the pellet. Of five treated rats, three showed no neovascularization and two demonstrated grade 1+ neovascularization. The difference in the degree of neovascularization between control and plasminogen fragment treatment was statistically significant (P<0.05). Conclusion: Our studies provide the first direct evidence that rat corneal neovascularization is inhibited by instillation of plaminogen fragment. This agent may prove useful in the treatment of corneal angiogenic disorder.     

Corneal neovascularization in rats as a model for photothrombotic therapy using bacteriochlorin a and an argon laser

Background: The presence of vessels has a negative influence on corneal transplant survival. Closure of such vessels prior to transplantation may improve the transplant results, and this might be achieved by irradiating the vessels with argon laser light after intravenous administration of a photosensitizer, e.g. bacteriochlorin a (BCA). A suture-induced corneal neovascularization model in rats was set up to test this hypothesis. Methods: Suture-induced vessels in the cornea of male Wistar rats were irradiated with argon laser light after intravenous administration of BCA. We applied irradiation of varying energy levels and duration and assessed the changes in the vessels by slit-lamp examination, fluorescein angiography and histology. Results: Suture-induced corneal vessels in the rat could be used effectively to study photothrombosis therapy. Intravenous administration of BCA prior to irradiation (=514.5 nm) of the corneal vessels led to vessel closure at lower energy levels and of longer duration than occurred with laser treatment alone. Conclusion: Suture-induced corneal neovascularization in the rat can be used as a model to study the efficacy of photothrombosis therapy. BCA can be used to enhance the rate and duration of vessel closure.     

Therapeutic use of the 193-nm excimer laser in corneal pathologies

Purpose: To analyze the results of phototherapeutic keratectomy. Patients and methods: We performed 193-nm excimer laser phototherapeutic keratectomy (PTK) in 252 eyes of 216 patients suffering from pain and/or decrease in visual acuity. One hundred and three eyes had recurrent erosions of the cornea, 86 eyes underwent excimer laser smoothing of the cornea after pterygium surgery, 29 eyes had a bandlike keratopathy (25 rough, 4 smooth) and 34 eyes had other pathologic conditions such as amyloidosis of the cornea, anterior corneal dystrophies, scars after injuries, alkali burns, superficial stromal dystrophies and infections. Recurrent erosions and epithelial dystrophies were treated with 15–20 pulses (160–200 mJ/cm², 8 mm ablation zone) after mechanical abrasion of the epithelium. Removal of corneal opacities and scars required the use of a masking fluid (methylcellulose) in different concentrations and slit-lamp control (integrated in the delivery system of the excimer laser). Results: Some 91% of the eyes with recurrent erosions were recurrence-free. Fifty-two per cent of the eyes with pterygium had recurrences if the baresclera technique was used and 33% of the eyes if a free conjunctival graft was used. The difference was not significant. All of the patients with bandlike keratopathy were pain-free. In 88% of the eyes with special indications the treatment goal was achieved. No positive effect was seen after alkali burn, in a patient with anterior membrane dystrophy (Grayson-Wilbrandt corneal dystrophy) or in a patient with a corneal protuberance. In one patient with scleroperikeratitis a late recurrence of the opacity was observed 3 years after surgery. A loss of best corrected visual acuity was found only in one patient with bullous keratopathy in whom the treatment goal was the reduction of pain. All patients with smooth bandlike keratopathy had an improvement in best corrected visual acuity of at least one line. About 70% of patients with special indications improved by at least one line, up to nine lines. A possible hyperopic shift in all groups could be minimized using a large ablation zone. Conclusion: PTK with the 193-nm excimer laser is a safe and effective treatment for many superficial diseases of the cornea.Werner Förster is the Primary Investigator for Schwind Keratom     

Orthotopic corneal transplantation in the mouse — a new surgical technique with minimal endothelial cell loss

Background: The murine model of orthotopic perforating keratoplasty is important for studying the allograft reaction, but the small dimensions cause technical difficulties. Methods: The anterior chamber of the eye of the BALB/c mouse was measured with the confocal microscope and with histological methods. Ten C3H mouse donor corneas each were separated by the conventional technique and by the newly developed underwater technique, where the opened donor eye did not lose its shape under water. The corneal endothelium was stained with trypan blue and alizarin red S. Ten BALB/c (H-2d) mice received a corneal graft taken from a C3H (H-2k) mouse by the underwater technique. Results: The 3.7-mm eye of the BALB/c mouse has a corneal diameter of 3.5 mm. The cornea has a central thickness of 170 m, the epithelium comprising 30% and the stroma 70%. While none of the corneas separated by the new underwater technique evidenced endothelial damage, a 28 ± 17.0% defect of the endothelial surface was found with the conventional technique. All transplanted corneas were clear when the lids were opened on the 2 post-operative day and clouded between the 7th and 30th days (mean 16.5 days) due to an allograft reaction. Conclusion: The newly developed underwater technique is superior to the conventional technique, since floating of the very thin donor cornea during the separation procedure prevents endothelial defects by guarding against folds. By enabling reliable keratoplasty in the mouse, this technique facilitates studies on the experimental allograft reaction.     

The retinal depression sign in diabetic retinopathy

Background: The retinal depression sign, an abnormal light reflex due to ischemia-induced focal inner retinal atrophy, was initially described in patients with sickle cell retinopathy. We undertook this study to characterize the finding in diabetic retinopathy. Methods: The fundus photographs of 97 consecutive patients with diabetic retinopathy seen in the Penn State University Ophthalmology Department were reviewed. We recorded age, sex, type of retinopathy, visual acuity and photographic details, including the presence or absence of the retinal depression halo. Results: The retinal depression sign was present in 9 of 22 patients age 45 years or under, versus 1 of 75 patients age 46 or older (P<0.0001, two-tailed Fisher's exact test). The presence or absence of retinal depression sign did not predict the type of retinopathy in a given patient. Eleven (70%) of the affected eyes had visual acuity 20/40. Conclusion: The retinal depression sign is common in younger patients with diabetes and should be distinguished from other macular lesions associated with diabetic retinopathy.