Scleral Damage Research Articles

Первый опыт транссклеральной лазерной термотерапии ретинобластомы

Purpose. To evaluate the efficacy of transscleral thermotherapy (TSTT) in eight patients with retinoblastoma (Rb). Material and methods. In total, 8 patients (9 eyes, 22 tumors) with Rb were treated by TSTT. The average age at the time of treatment was 28 months (from 10 to 45 months). Bilateral Rb was observed in six patients, unilateral – in two. All tumors had preequatorial localization (7 foci – on the mid periphery and 15 – on the far periphery of the fundus). The number of tumors in one eye varied from 1 to 6. The mean tumor thickness was 0.7 mm (from 0.5 to 1.4), the mean basal diameter was 1.5 mm (from 1.0 to 2.9). TSTT was performed transconjunctivally using a diode laser with the following parameters: wavelength – 810 nm, spot diameter – 1000 microns, power from 200 to 500 MW (average – 350 MW), exposure – from 3 to 15 seconds in the scanning mode. Results. Complete tumor regression after TSTT was achieved in 86% of cases (19 tumors). In one case (5%) an incomplete tumor regression was observed and transpupillary thermotherapy was performed. In two cases (9%) continued tumor growth occurred, which required the use of cryotherapy. Overall local tumor control was achieved in all cases (22 tumors). All eyes are preserved, all patients included in the study are alive without distant metastases. No complications from both the anterior and posterior segments, as well as visual signs of scleral damage were not observed in any case. The follow–up period after TSTT ranged from 3 to 11 months (mean – 6 months). Conclusion. First experience of TSTT showed that this method is very promising and can be used to treat small Rb of preequatorial localization in the absence of risk of damage to the iris and equator of the lens, which is the benefit of TSTT compared to transpupillary thermotherapy. Key words: retinoblastoma, transcleral thermotherapy, laser treatment, preequatorial localization, small tumors

Intravitreal dexamethasone: variation of surgical technique and prevention of ocular complications with ASOCT follow-up

PurposeTo verify the correct decision-making procedure on performing an intravitreal injection by investigating the in vivo wound morphology and evolution of 22-gauge wounds after dexamethasone oblique injection with anterior segment optical coherence tomography (OCT).DesignProspective, observational consecutive case series.MethodsSubjects underwent a dexamethasone injection at University Eye Clinic of Turin. All the injections have been performed in an oblique (aka beveled or angled) fashion. Patients were divided according to the number of injections already performed with dexamethasone. Group 1 consisted of patients at the first injection, group 2 of patients at a second or more injection always in the same quadrant, and group 3 of patients at the second or more injection in a different quadrant. The incisions were imaged with the Heidelberg SPECTRALIS OCT device on postoperative days 1, 8, and 15. The main outcome measure was wound structure/characteristics (e.g., presence of gaping) as evaluated with OCT. Surgical and ocular parameters were also recorded.ResultsThirty-three consecutive patients were investigated. OCT demonstrated closed wounds in all eyes on postoperative days 1, 8, and 15. In all patients, the external (entry) side of the incision was seen as a gape; however, the rest of the wound was closed. No complications were recorded in the different patients during the follow-up. In patients of group 1, we identified the scleral pathway in 10 eyes at day 1. At 8 days in 9 of 10 eyes, the sclera had returned to its restitutio ad integrum. In patients of group 2, the scleral pathway was recognizable on the first day of control; in 7 patients, this was accompanied by the presence of intrascleral edema with peri-wound fluid. At the 8-day checkup, 3 eyes still showed signs attributable to the intrascleral pathway accompanied by peri-wound edema. In group 3, it was possible to identify the intrascleral pathway in 8 patients. There were no signs of intrascleral peri-wound edema or other anatomical changes in 9 patients as early as the first day. In the 8-day follow-up, the signs of scleral edema were absent in the single patient who presented them. At 15 days, there were no signs of scleral pathway in all eyes analyzed.ConclusionsSpeaking of intravitreal injections of slow-release dexamethasone, the technique that involves moving the conjunctiva and a beveled or angled sclerotomy after a careful choice of the injection site, paying attention to vary the quadrant involved with each puncture, reduces the number of days of closure of the sclera via and the scleral damage, thus protecting the patient from complications. For the future, it is hoped that the operating microscope and intraoperative OCT will be used on every occasion.

Effects of topical erythropoietin on healing experimentally-induced avascular scleral damage in a rabbit model

The present study was designed to investigate the effect of topical erythropoietin on the healing process of induced necrotizing scleritis and to evaluate the ocular side effects of this treatment modality in a rabbit model. Necrotizing scleritis was induced in 8 New Zealand albino rabbits. The animals were then randomly divided into one of two groups: a treated group administered a topical erythropoietin-containing cellulose-based gel every 8 h or a control group treated with a cellulose-based gel without erythropoietin every 8 h. The sizes of the lesions measured at different time points were compared between the groups. After three months, the rabbits’ eyes were enucleated and histologically and immunohistochemically evaluated for angiogenesis and apoptosis. The lesions were completely vascularized in all eyes of the treated group and 50% of eyes of the control group. The mean interval from the induction of scleral necrosis to a complete improvement was 28 days in the treated group and 62.5 days in the control group (P = 0.04). Histological examination revealed that erythropoietin enhanced the improvement of necrotizing scleritis by stimulating angiogenesis and reducing apoptosis. Neovascularization of the cornea, iris, or retina was not observed in the treated group. We observed a significantly faster recovery to complete improvement of necrotizing scleritis in rabbit eyes treated with erythropoietin compared to those of the control group. Treated eyes had a higher rate of complete healing and had no ocular safety concerns. This therapeutic modality represents a promising treatment for scleral necrosis following various types of ocular surgery.

ARE INTRAVITREAL INJECTIONS WITH ULTRATHIN 33-G NEEDLES LESS PAINFUL THAN THE COMMONLY USED 30-G NEEDLES?

This study investigated whether pain from intravitreal injections (IVIs) can be reduced by injecting with a 33-G needle instead of the commonly used 30-G needle. Additionally, several pain-related psychological factors were explored as predictors of outcome. This randomized crossover trial included 36 patients who received injections with both needles in randomized order. After the injection, patients rated IVI pain on a 0 to 10 scale. Before injection, distress and pain expectations were assessed. Afterward, patients rated the IVI procedure and anticipated consequences. In addition, we assessed the force necessary to penetrate the sclera for both needles in porcine eyes. The 33-G needle did not result in lower IVI pain (2.8 vs. 3.1, P = 0.758) but tended to cause less vitreal reflux (0 vs. 5 times, P = 0.054). Factors related to more pain were distress, expecting IVI pain and discomfort, dissatisfaction with the preparation procedure, anticipating negative consequences, and female gender. Patients regarded povidone-iodine disinfection as particularly unpleasant. Exploration of the needles' mechanical properties showed that 33-G needles penetrate the sclera more easily. The thinner 33-G needle does not reduce IVI pain but may limit scleral damage. Future efforts could be aimed at optimizing patient information, reducing distress, and the use of better tolerable disinfectants.

Biometry-based concentric tubes robot for vitreoretinal surgery.

Vitreoretinal surgery requires dexterous manoeuvres of tiny surgical tools in the confined cavity of the human eye through incisions made on the sclera. The fulcrum effect stemming from these incisions limits the safely reachable intraocular workspace and may result in scleral stress and collision with the intraocular lens. This paper proposes a concentric tube robot for panretinal interventions without risking scleral or lens damage. The robot is designed based on biometric measurements of the human eye, the required workspace, and the ease of incorporation in the clinical workflow. Our system is suited to 23 G vitreoretinal surgery, which does not require post-operative suturing, by comprising sub-millimetre concentric tubes. The proposed design is modular and features a rapid tube-exchange mechanism. To grasp and manipulate tissue, a sub-millimetre flexible gripper is fabricated. Experiments demonstrate the ability to reach peripheral retinal regions with limited motion at the incision point and no risk of lens contact.

Foxg1-Cre Mediated Lrp2 Inactivation in the Developing Mouse Neural Retina, Ciliary and Retinal Pigment Epithelia Models Congenital High Myopia.

Myopia is a common ocular disorder generally due to increased axial length of the eye-globe. Its extreme form high myopia (HM) is a multifactorial disease leading to retinal and scleral damage, visual impairment or loss and is an important health issue. Mutations in the endocytic receptor LRP2 gene result in Donnai-Barrow (DBS) and Stickler syndromes, both characterized by HM. To clearly establish the link between Lrp2 and congenital HM we inactivated Lrp2 in the mouse forebrain including the neural retina and the retinal and ciliary pigment epithelia. High resolution in vivo MRI imaging and ophthalmological analyses showed that the adult Lrp2-deficient eyes were 40% longer than the control ones mainly due to an excessive elongation of the vitreal chamber. They had an apparently normal intraocular pressure and developed chorioretinal atrophy and posterior scleral staphyloma features reminiscent of human myopic retinopathy. Immunomorphological and ultrastructural analyses showed that increased eye lengthening was first observed by post-natal day 5 (P5) and that it was accompanied by a rapid decrease of the bipolar, photoreceptor and retinal ganglion cells, and eventually the optic nerve axons. It was followed by scleral thinning and collagen fiber disorganization, essentially in the posterior pole. We conclude that the function of LRP2 in the ocular tissues is necessary for normal eye growth and that the Lrp2-deficient eyes provide a unique tool to further study human HM.

Anatomical Manifestations of Primary Blast Ocular Trauma Observed in a Postmortem Porcine Model

We qualitatively describe the anatomic features of primary blast ocular injury observed using a postmortem porcine eye model. Porcine eyes were exposed to various levels of blast energy to determine the optimal conditions for future testing. We studied 53 enucleated porcine eyes: 13 controls and 40 exposed to a range of primary blast energy levels. Eyes were preassessed with B-scan and ultrasound biomicroscopy (UBM) ultrasonography, photographed, mounted in gelatin within acrylic orbits, and monitored with high-speed videography during blast-tube impulse exposure. Postimpact photography, ultrasonography, and histopathology were performed, and ocular damage was assessed. Evidence for primary blast injury was obtained. While some of the same damage was observed in the control eyes, the incidence and severity of this damage in exposed eyes increased with impulse and peak pressure, suggesting that primary blast exacerbated these injuries. Common findings included angle recession, internal scleral delamination, cyclodialysis, peripheral chorioretinal detachments, and radial peripapillary retinal detachments. No full-thickness openings of the eyewall were observed in any of the eyes tested. Scleral damage demonstrated the strongest associative tendency for increasing likelihood of injury with increased overpressure. These data provide evidence that primary blast alone (in the absence of particle impact) can produce clinically relevant ocular damage in a postmortem model. The blast parameters derived from this study are being used currently in an in vivo model. We also propose a new Cumulative Injury Score indicating the clinical relevance of observed injuries.

Experimental investigation of needles, syringes and techniques for intravitreal injections

To assess the techniques and materials used in intravitreal injections. Descriptive study realized at the Vision Institute of the Federal University of São Paulo, Brazil. Different brands of needles and syringes, as well as enucleated porcine eyeballs. The ultra-structures of commonly used needles were analysed by scanning electron microscope, and they were compared using different criteria, such as irregularities and debris from the lubrication process. The scleral incision was also assessed using needles of different brands and sizes. Accuracies in drug administration were studied by comparing the residual and delivered volume of needles and also by the analysis of reflux after intravitreal injections. Efficiency and quality of materials used in intravitreal injections. Ultra-structure analyses showed that all needles had different types of irregularities. Some photographs showed debris from the lubrication process, especially in BD needles. Scleral incision analysis showed a tendency of reducing the ocular damage with increasing gauge (P=0.024). The investigation of delivery accuracy showed that almost all needles underdosed the amount injected (P<0.05), and that the reflux could be minimized by tunnelled injections with thinner needles. Needles used in intravitreal injections possess many irregularities in their structures, which may cause different injection outcomes. Analyses of scleral incisions showed that the larger the needle gauge, the lesser the scleral damage and the risk of complications. Moreover, drug administration inaccuracies might be one of the causes for some unsuccessful attempts of treatment.

The use of imbricated sutures in radioactive plaque brachytherapy surgery

This paper describes a new technique to suture the radioactive plaque to sclera. The radioactive plaque is conventionally sutured to the sclera using 5/0 nylon sutures. The imbricated suture technique involves using a 1/0 silk or 2/0 mersilene suture imbricated with the 5/0 nylon suture when the nylon suture is tied and cut. The imbricated suture technique allows easy identification of the plaque at removal and provides a surface that separates the 5/0 nylon from the surface of the eyelet platform, making suture cutting easier and safer. The radiation exposure times ranged from 9.1 minutes to 14 minutes (mean: 10.8 minutes) during plaque insertion and from 2.8 to 3.3 minutes (mean: 3.0 minutes) during plaque removal with the imbricated suture technique. This technique may decrease radiation exposure time and may prevent inadvertent scleral damage.

Transscleral thermotherapy with laser-induced and conductive heating in hamster Greene melanoma.

The purpose of this study was to investigate the cytotoxic effect of heat as induced by transscleral thermotherapy (TSTT), which may be of interest in the treatment of patients with choroidal melanoma. The aim of TSTT is to heat both the sclera and the tumor up to a cytotoxic temperature of about 60 degrees C. TSTT was performed in hamsters with subcutaneously implanted Greene melanoma covered by a specimen of human donor sclera of thickness 0.5, 0.7 or 0.9 mm. A newly developed applicator, which combines conductive episcleral heating at 60 degrees C with laser-induced heating, was used at laser powers ranging from 500 to 1500 mW delivered by an 810 nm diode laser, beam diameter 3 mm, and exposure time 1 min. Temperatures were measured at the scleral surface and at the sclera-tumor interface. The extent of tumor necrosis was examined by light microscopy and the sclera was examined by polarized light microscopy. Maximal depth of tumor necrosis without scleral damage was 4.4 (SD 1.5) mm. The temperature at the scleral surface after TSTT was 58.8 (SD 2.4) degrees C. The temperature at the sclera-tumor interface ranged from 56.4 (SD 3.7) degrees C at 500 mW to 65.3 (SD 4.4) degrees C at 1250 mW laser power. Structural changes to the scleral collagen started to develop at 1250 mW. TSTT with combined laser-induced and conductive heating caused cytotoxic temperatures in the tumor and the sclera, which were well tolerated by the scleral collagen.

Temperature Dependence of Thermal Damage to the Sclera: Exploring the Heat Tolerance of the Sclera for Transscleral Thermotherapy

Thermal damage to the human sclera in relation to temperature and duration of exposure was studied in order to determine the heat tolerance of the sclera with respect to transscleral thermotherapy of choroidal melanoma. Samples of human sclera were submerged in saline for 10sec to 10min at temperatures of 37–100°C. The effects of heat on the shape, weight and size of the samples were studied. Thermal damage of scleral collagen was examined by polarized light microscopy (LM) and electron microscopy (EM). The sclera was embedded in epoxy resin and stained with toluidine blue for LM and with uranyl acetate and lead citrate for EM. Thermal damage of scleral collagen on polarized LM was graded on a five point scale. Scleral damage was visible on macroscopic examination and on LM and EM in sclera heated at 65°C for 20sec or longer, at 70°C for 10sec or longer, and at higher temperatures. A sigmoidal function was used to define the relation between temperature and changes in diameter, thickness, and weight of scleral samples. Using fitted functions, the threshold temperature for thermal damage was estimated to be 59–61°C when samples were heated for 10min, 62–63°C when heated for 1min, and 66–67°C when heated for 10sec; the threshold exposure time at 60°C was estimated to be 7–12min. These results indicate a temperature of 60°C for 1min is well tolerated by human donor sclera; information of in vivo studies is required to validate whether this setting can be used in transscleral thermotherapy (TSTT) for choroidal melanoma.

Transscleral Diode Laser Cyclophotocoagulation on Autopsy Eyes With Abnormally Thinned Sclera

To determine, using autopsy eyes, whether diode laser energy adjustments are indicated in patients with thin sclera. In the laboratory, the superior 180 degrees of sclera at the limbus was dissected to the level of barely visible anterior uvea and the opposite 180 degrees of sclera served as the control in three human cadaver eyes. A contact G-probe was placed at the limbus, and settings of a diode laser were increased in increments from 1.0 to 9.0 J at 4 burns per setting in each location. On gross examination, circular hypopigmented lesions were seen in the ciliary body (CB) beginning at 3.0 J in thin sclera and at 5.0 J in normal sclera. On light microscopic examination of thin scleral sections, CB damage began at 2.9 J and CB/ciliary body epithelium (CBE) damage occurred beginning at 3.5 J. In normal sclera, minimal CB/CBE changes occurred at 6.0 to 7.5 J. No scleral damage was visible in either the experimental or the control groups. Cycloablation energy adjustments are indicated on eyes with abnormally thin sclera to achieve similar histologic end points using the diode laser.

The In Vivo Effects of a Prototype Diode Laser Coagulator/Vaporizing Endoprobe Used to Perform Retinectomy and Retinotomy in Rabbits

A pilot study was conducted to evaluate the use of a prototype intraocular carbon-coated diode laser probe for performing single-instrument internal retinotomy and retinectomy. A 20-gauge endolaser probe was used to perform retinotomies on 10 anesthetized rabbits. Two protocols were examined: one using low power and long duration, and one using high power and short duration. Retinotomies were performed on attached and experimentally detached retinas. Retinotomies were performed in all eyes using both protocols. The edges had photocoagulative effects in all cases. The eyes treated with the longer duration, lower power protocol had scleral damage, whereas the eyes treated with shorter duration, higher power did not. Although the diode laser coagulator/cutter may be used for retinotomies, it should be studied further.

Histopathological findings in human choroidal melanomas after transpupillary thermotherapy

AIMSThe effect of transpupillary thermotherapy (TTT) on human choroidal melanomas was investigated by means of histopathology.METHODSBefore enucleation TTT was performed in 11 eyes with a xenon arc photocoagulator with a...

Value of ultrasound biomicroscopy for ciliodestructive procedures.

Ciliodestructive procedures are commonly performed by the transscleral approach because ciliary processes are seldom visible. Thus the ablative energy is directed toward an "invisible" target whose position can only be estimated on the basis of experimental data. Ultrasound biomicroscopy has been recently introduced in ophthalmologic practice. This high-frequency ultrasound B-scan method gives real-time images of the subsurface structures of the anterior portion of the living eye at microscopic resolution. Ultrasound biomicroscopy perfectly visualizes the ciliary body and its surrounding structures and is a promising complementary tool for ciliodestructive procedures. The system has been used to image early and late ciliary body alterations after transscleral cyclophotocoagulation, to establish the position of the ciliary body to ensure correct laser probe placement, to locate ciliary body residuals for retreatment, and to rule out scleral damage after the procedure. An apparatus has been designed for simultaneous contact cyclophotocoagulation and ultrasound biomicroscopy analysis. A prospective randomized clinical trial is now needed to clarify the influence of ultrasound biomicroscopy on the success rate of ciliodestructive procedures.

Microwave Diathermy of the Retina and Choroid

Microwaves were used to induce chorioretinal scar formation in normal rabbit eyes. We have developed a directional 6.8-gigahertz microwave applicator with a rectangular aperture. It was designed to mimic the shape and function of a T-shaped scleral depressor. For treatment, the applicator was placed on the conjunctiva over the sclera. Then, indentation was used to visualize probe placement during indirect ophthalmoscopy. Thermocouple-controlled heating was initiated such that conjunctival temperatures in a range of 51 degrees C to 65 degrees C were induced for 10 seconds per treatment. We found that treatment at temperatures of 51 degrees C or 52 degrees C for 10 seconds produced circular areas of acute retinal whitening. From these microwave-induced lesions, there evolved chorioretinal attenuation with and without evidence of retinal pigment epithelial hyperplasia. No evidence of scleral damage was noted at these thermal doses.

Transcleral contact krypton‐laser photocoagulation of the retina in rabbits

Transcleral contact retinal krypton laser photocoagulation of the retina was studied in rabbit eyes. The laser application was performed under indirect ophthalmoscope visual control with indentation of the sclera by the laser probe. Retinal lesions were produced with powers ranging from 0.2 to 0.3 W and application times between 1 and 2 sec. The lesions were studied histologically 2, 5, 10, 12, 20, 30 and 70 days after treatment. Histopathological examination of the lesions showed damage of mainly the outer retinal layers in light lesions, and to all layers of the retina in the more intense lesions. No scleral damage was observed in the light lesions, whereas transient oedema of the inner sclera was seen in the intense lesions. Studies with enucleated rabbit eyes showed that indentation of the sclera by the laser probe substantially decreased the power needed to produce a retinal lesion. It is concluded, that when used with scleral indentation, transscleral krypton laser photocoagulation of the retina can be performed with minimal damage to the sclera.

Focal Scleral Thinning After Transscleral Nd: YAG Cyclophotocoagulation

Transscleral neodymium (Nd):YAG cyclophotocoagulation, a new cyclodestructive procedure for controlling intraocular pressure in patients with refractory glaucoma, is designed to penetrate the sclera and selectively destroy the ciliary body and processes without damaging the overlying tissue. Complications include conjunctival edema, corneal edema, iritis, gas in the anterior chamber, pain, hyphema, hypopyon, vitreous hemorrhage, and cataract. We present a case in which a patient developed focal areas of scleral thinning 6 weeks after transscleral Nd:YAG cyclophotocoagulation. The possibility of scleral damage or thinning should be kept in mind when performing the procedure.

CO&lt;SUB&gt;2&lt;/SUB&gt;レーザーの眼科的応用

We developed a needle type probe consisted of fiberoptics to transmit CO2 laser effectively and intra- and extraocular photocoagulation with CO2 laser were performed successfully. In the experimental intraocular photocoagulation, the approach was similar to the pars plana vitrectomy. The retina was coagulated by almost touching the to it. And retinal vein was occluded by coagulation which may be applicable to treat neovascularization of various fundus disease. The extraocular coagulation is as effective as cryocautery with minimum scleral damage. Because of its several merits, it is already in many cases and useful results have been obtained as retinal detachment surgery.

Cryosurgery of the Retina

In 1931, J. Gonin presented his original concept that retinal detachment is caused by a retinal break and reattachment could be achieved by inducing inflammation around the break with diathermy and by simultaneous draining of subretinal fluid. The primary advantage of cryosurgery is the ability to penetrate the sclera and to create a retinal adhesion without causing scleral necrosis. The early ophthalmoscopic appearance of a cryosurgical lesion is a function of retinal transparency. The reluctance to employ cryosurgery was the uncertainty of the strength of the cryopexy-induced adhesion. Cryosurgery allows retinal coagulation through full-thickness sclera without scleral damage and thus allows a minimal extraocular procedure for retinal detachment that employs an elastic explant to buckle the area limited to the retinal break. The pattern of the healed retinal cryosurgical lesion depends on the depth of thermal necrosis created by the cryopexy application and the extent of the basement membrane interruption.