Analysis of filtration according to implant type after deep sclerectomy in the rabbit]

PURPOSE: The purpose of this study was to compare the aqueous humor outflow using three type of implants after deep sclerectomy. A numeric imaging system with ICG and fluorescein angiography was used. The evolution over time was recorded, while filtration and outflow facility were measured. MATERIAL AND METHODS: Numeric imaging system with ICG and fluorescein angiography were performed before and after deep sclerectomy at regular intervals after surgery. Both resorbable (collagen) and non-resorbable (hema) intrascleral devices have been tested in eight rabbits. The resorption time of the collagen implants has been monitored using UBM technique. The outflow facility was measured with the technique of anterior chamber canulation and constant pressure method. RESULTS: The resorbable collagen implants could be observed with UBM and angiography during the first six weeks post-operatively. The image of the non-resorbable Hema implant remained clearly visible over time. New drainage vessels were observed around the filtering bleb. The filtration significantly increased as the outflow facility improved after surgery, while the intraocular pressure remained stable over time. CONCLUSION: This conjunction of UBM, angiography and outflow measurement allowed us to study and compare three types of implants used as space maintainer after deep sclerectomy, and analyse their effect on the aqueous filtration and outflow facility.     

盐酸哌唑嗪对脱交感家兔眼葡萄膜巩膜途径的形态学研究

目的：从形态学探讨盐酸哌唑嗪（PZ）对脱交感家兔眼（FSRE）葡萄膜巩膜途径（FU）的作用。方法：家兔作单侧颈交感神经节切除术后第14日在手术侧点PZ滴眼液,通过前房内注入异硫氰酸荧光素牛血清白蛋白,PZ点眼后每2h各处死家兔2只,于荧光显微镜下观察FU各部位的荧光强度等级。结果：PZ点眼后FSRE眼压下降,但降压幅度低于正常家兔眼;点眼后FU各部位的荧光强度均稍强于对侧眼的相应部位。结论：PZ增加FU排出的作用在FSRE明显减弱,其作用部分依赖于交感神经活性,尚有未通过交感活性的其它机制。     

Evaluation of the blood-aqueous barrier after vitreous replacement with perfluoropropane gas and liquid silicone.

Fluorophotometric measurements of blood-aqueous barrier permeability after intravitreal injection of perfluoropropane gas in rabbit eyes revealed fluorescein leakage immediately after injection; 3 days later, recovery of barrier integrity had begun to occur and 7 days and 14 days after gas injection, when the gas bubble was still in the eye, anterior chamber fluorescein concentrations were normal. Similarly, in eyes undergoing vitrectomy and injection of silicone liquid or vitrectomy only, anterior chamber fluorescein levels were elevated 3 days and 1 week after surgery. Nevertheless, normal barrier integrity was reestablished in both the silicone-filled eyes and the vitrectomized eyes after 1 week. Since there was no difference between the group injected with silicone and the group that underwent vitrectomy only with respect to anterior chamber fluorescein concentration at any of the times studied, it is concluded that the temporary disruption of the blood-aqueous barrier is associated with the surgical procedure rather than the presence of silicone liquid in the vitreous cavity.     

Dye-enhanced cataract surgery. Part 1: anterior capsule staining for capsulorhexis in advanced/white cataract

PURPOSE: To evaluate anterior capsule staining using 3 dyes to perform continuous curvilinear capsulorhexis (CCC) in postmortem human eyes with advanced/white cataract. SETTING: Center for Research on Ocular Therapeutics and Biodevices, Storm Eye Institute, Medical University of South Carolina, Charleston, South Carolina, USA. METHODS: In experimental closed-system surgery, CCC was performed in 12 postmortem human eyes with cataract after the anterior capsule was stained with 3 capsule dyes (fluorescein sodium 2%, indocyanine green [ICG] 0.5%, and trypan blue 0.1%). Two commonly used techniques for capsule staining were also compared: staining within an air bubble and intracameral subcapsular injection of dye. RESULTS: In all globes, CCC was uneventful using the 3 dyes and with both techniques. With the intracameral subcapsular injection, the dye remained trapped in the subcapsular space in contact with the posterior surface of the anterior capsule, allowing enough time to perform any maneuver. The staining provided by ICG, at the concentration used, was slightly superior to that of the other dyes. Leakage of fluorescein sodium into the vitreous cavity was seen using the Miyake-Apple posterior video/photographic technique. CONCLUSION: Intracameral subcapsular injection of ICG allowed the easiest recognition of the capsular flap by staining the posterior surface of the anterior capsule and without leaking into the vitreous cavity.     

Effects of intravitreal indocyanine green injection in rabbits

PURPOSE: To report the clinical, electrophysiologic, and histologic findings of different concentrations of indocyanine green (ICG) injected into the vitreous cavity of rabbit eyes. METHODS: Forty-two rabbits underwent intravitreal injection of 0.1 mL of ICG in three different concentrations: 0.5 mg/mL (250 mOsm), 5 mg/mL (270 mOsm), and 25 mg/mL (170 mOsm). Fellow eyes were injected with 0.1 mL of balanced salt solution. Biomicroscopy, ophthalmoscopy, electroretinography, fluorescein angiography, and histologic evaluation were performed. RESULTS: Eyes injected with 0.5 mg/mL of ICG showed b-wave latency delay on the first day after injection. Eyes injected with 5 mg/mL of ICG showed b-wave latency delay and decreased b-wave amplitude on the first and seventh days after injection; delayed a-wave latency on the first day after injection was also observed. Eyes injected with 25 mg/mL of ICG showed b- and a-wave amplitude and latency abnormalities during the entire follow-up. Direct correlation of increasing retinal edema proportional to the progressively increasing ICG concentrations was shown on histologic evaluation. CONCLUSION: Intravitreal ICG injection in rabbit eyes may impair retinal function and morphology proportional to the progressively increasing ICG dosages.     

Dye leakage in indocyanine green fundus angiography of a laser photocoagulated lesion]

Argon green laser photocoagulation was performed on adult pigmented rabbit eyes at various intensities (parameters:500 microns spot size, 0.2 sec. exposure, and 70-, 100-, 150- and 200-mW power levels), and fluorescein and indocyanine green (ICG) angiography was performed within one hour after coagulation. Each coagulum of ICG angiography was hypofluorescent in the early phase and brightly fluorescent in the late phase. The fluorescein and ICG dyes spread from the periphery to the center in the moderate and large coagula. The characteristic finding of ICG angiography was expansion of ICG dye around the coagulum, regardless of the degree of the coagulation. This ICG leakage was intra-choroidal because there was no fluorescein dye leakage around the coagulum. We concluded that the ICG dye leakage shows damage to the choroidal vessels due to laser photocoagulation, and is not related to the barrier function of the retinal pigment epithelium.     

Nonaxoplasmic transfer of indocyanine green into the optic nerve after intravitreal application

PURPOSE: To investigate whether indocyanine green (ICG) migrates into the optic nerve after intravitreal application in the rabbit eye. METHODS: Gas vitrectomy was performed in one eye of adult Dutch belted rabbits by pars plana injection of 0.4 ml of 100% C3F8 (n = 10). One week later, vitrectomy was performed and 0.2 ml of 0.25% ICG was instilled into the vitreous cavity of these vitrectomized eyes. After 30 seconds of ICG application, the vitreous cavity was rinsed with balanced salt solution plus. Unoperated rabbits served as controls (n = 2). Globes, optic nerves, and the entire brain were removed, and ICG fluorescence of the specimens was examined with a digital fundus camera starting from the first day to the fourth postoperative week. Other rabbit eyes (n = 2) were injected with ICG directly into the vitreous without vitrectomy, and assessed for ICG signal after 1 day of ICG application. In the second part of the experiment, four rabbit eyes were gas vitrectomized and ICG was instilled onto retina after blockage of axonal flow by vinblastine. They were evaluated on the first (n = 2) and seventh postoperative days (n = 2). RESULTS: No fluorescein was detected in the visual pathways and the brains of the control group of rabbits. The optic nerves of the ICG-instilled eyes were stained diffusely with ICG starting from the first day after surgery. ICG injected nonvitrectomized eyes showed similar ICG staining patterns when compared with vitrectomized eyes. ICG staining pattern of the optic nerve did not differ in vinblastine-pretreated eyes. Fluorescence extended along the intraorbital portion of the optic nerve but did not transport more posteriorly in all animals. At the fourth week after vitrectomy, ICG signal was still detectable, but staining was less intense. CONCLUSION: Intravitreal ICG injection results in nonaxoplasmic extension into the optic nerve in the rabbit.     

Outflow of aqueous humor following cyclodialysis or ciliochoroidal detachment in rabbit

Cyclodialysis and ciliochoroidal detachment were performed in three eyes of three rabbits and in three eyes of another three rabbits, respectively. After aspiration of the aqueous humor, 0.1 ml of 10% sodium fluorescein was injected intracamerally, and the eyeball was enucleated between 30 minutes and one hour after injection and prepared for fluorescence microscopy. Sodium fluorescein concentrations in the supraciliary space were much greater in the group with cyclodialysis or ciliochoroidal detachment than in the normal control group. These results suggest that (1) in the eye with cyclodialysis, the aqueous humor may freely gain access to the supraciliary space through the cleft between the anterior chamber and the supraciliary space and then be removed rapidly and (2) in the eye with ciliochoroidal detachment, the aqueous humor may pass through the uveoscleral outflow pathway.     

Anterior capsule staining for capsulorhexis in cases of white cataract: comparative clinical study

PURPOSE: To compare the safety and efficacy of trypan blue 0.1%, gentian violet 0.001%, indocyanine green 0.5% (ICG), fluorescein 2%, and the patient's autologous blood for anterior capsule staining in cases of white cataract. SETTING: Rajendra Prasad Center for Ophthalmic Sciences, All India Institute of Medical Sciences, New Delhi, India. METHODS: Fifty eyes of 50 patients with age-related white cataract had anterior capsule staining with trypan blue, ICG, or gentian violet under an air bubble or subcapsularly with fluorescein or autologous blood followed by phacoemulsification with foldable intraocular lens implantation. Each stain was used in 10 eyes. The ease of creating a continuous curvilinear capsulorhexis (CCC) and the complications during the surgery were noted. Postoperative examinations at 6 hours, 1 day, 1 week, and 1 month included slitlamp microscopy, uncorrected visual acuity, and best corrected visual acuity (BCVA). The staining patterns on the anterior capsule, side port, corneal tunnel, and anterior cortex were assessed intraoperatively and within 6 hours and at 1 day. The intraocular pressure (IOP) was assessed at 1 day; pachymetry, at 1 day and 1 month; and the endothelial cell count, at 1 month. RESULTS: The surgeon had best visualization during the anterior capsulorhexis with trypan blue, ICG, and gentian violet, and a complete CCC was achieved in all eyes in the 3 groups. Two eyes each in the fluorescein and autologous blood groups had extension of the CCC so that the capsulorhexis was complete but not curvilinear. Anterior capsule fibrosis was detected with trypan blue (1 eye) and ICG (2 eyes). The anterior vitreous was stained with fluorescein in 2 eyes. All eyes achieved a BCVA of 20/30 or better from 1 week postoperatively to the last follow-up. The side port and corneal tunnel were stained most intensely with gentian violet followed by trypan blue and ICG and less intensely with fluorescein and autologous blood. The IOP, pachymetry, and endothelial cell loss were comparable between the stains. CONCLUSION: Although trypan blue, ICG, gentian violet, fluorescein, and autologous blood were safely used to stain the anterior capsule for phacoemulsification in eyes with white cataract, trypan blue, ICG, and gentian violet were more effective in staining the capsule.     

Indocyanine green angiography of juvenile X-linked retinoschisis

PURPOSE: In juvenile X-linked retinoschisis (XLRS), fluorescein angiography is usually unremarkable and contributes poorly to the diagnosis. However, indocyanine green (ICG) angiography features in eyes that are affected with XLRS were not yet described. DESIGN: Retrospective observational case series. METHODS: A complete ophthalmologic examination that included ICG angiography was performed on three unrelated male patients (six eyes) who were 15, 22, and 48 years old. RESULTS: A distinct hyperfluorescent stellate pattern in the macular area that was associated with radial lines of hypofluorescence that were centered on the foveola was observed on the early phase of ICG examination (six of six eyes). This feature disappeared on the late phase of ICG examination. CONCLUSION: On these six XLRS eyes, early phases of ICG examination revealed an unusual radial aspect on the macula. This finding suggests that ICG angiography may be useful for the diagnosis of XLRS.     

Correlation of aqueous humor ascorbate with intraocular pressure and outflow facility in hereditary buphthalmic rabbits

The hypotensive effect of ascorbate on intraocular pressure has been reported following topical application, oral administration, or anterior chamber infusion in animals. The present report describes the correlation of aqueous humor ascorbate concentration with intraocular pressure as well as outflow facility in vivo. Low aqueous ascorbate level was seen in buphthalmic eyes with high intraocular pressure and low outflow facility. The opposite correlation was observed in normal eyes. Ascorbate concentration in the anterior chamber of the rabbit eye is apparently related to the alteration of outflow facility and the movement of fluid in the anterior chamber.     

The fate of anterior chamber flurescein in the monkey eye. 1. The anterior chamber outflow pathways.

As defined by freeze-dry tissue techniques, there are two distinct routes by which fluorescein leaves the anterior chamber of the living rhesus monkey eye. I. The conventional pathway: Within five minutes of the initiation of fluorescein perfusion through the anterior chamber, the conventional pathway filled. Tracer passed through the trabecular meshwork into Schlemm's canal, and flowed back within scleral and episcleral venous derivatives to enter large veins in the extraocular muscles. II. The uveo-vortex pathway: Fluorescein rapidly moved into the iris stroma and into the anterior part of the ciliary body. The anterior chamber border of the ciliary body is little more than a sparse mesh from which fluorescein entered directly into the substance of the anterior ciliary muscle. Fluorescein penetrated blood vessels in the iris stroma and in the anterior ciliary body from where it could be traced posteriorly to the equatorial choroid and vortex veins. The specific sequential tissue distribution of fluorescein strongly supports the existence of a uveo-vortex pathway for aqueous outflow.     

The mode of action of trabeculectomy (author's transl)]

We could ascertain the mode of action of trabeculectomy by clinical research in more than 370 eyes after the operation and especially by the injection of fluorescein into the anterior chamber in 90 of these eyes. The following drainage mechanisms of the aqueous humor were observed: 1. Outflow through new developed aqueous veins (trabeculectomy-veins), 2. Bulkflow through lymphatic vessels, 3. Diffuse resorption into the subconjunctival tissue, 4. Outflow through normal aqueous veins. The latter mechanism is seldom of great importance. In only three cases passed all of the visible aqueous outflow through normal aqueous veins. In these cases an opening of Schlemm's canal could be assumed. In all of the other eyes we could not find any evidence for an outflow through Schlemm's canal whether there was a filtering bleb or not. This means that from the presence or absence of a visible bleb no conclusion can be drawn as to the mode of action.     

Morphology and function of the aqueous outflow system in monkey eyes perfused with sulfhydryl reagents

The aqueous outflow system from anterior chamber to Schlemm's canal was examined by electron microscopy in pairs of enucleated macaque and baboon eyes, perfused via the anterior chamber with mock aqueous humor in one eye and the same fluid with added iodoacetamide (IA) or N-ethyl maleimide (NEM) in the other eye. Many details of the electron micrographs were analyzed in a masked manner using a digitizing bit pad and computer, and also using visual evaluation. Both IA and NEM increased aqueous humor outflow facility, but the morphologic changes induced by IA were quantitatively different from those induced by NEM. Intercellular junctions were not affected by IA, but were disrupted by NEM (P less than 0.01). Vacuoles in the endothelial lining of Schlemm's canal tended to increase in area, but not in number, under the influence of IA, whereas they were not so affected by NEM. No loss of extracellular material was observed in either IA- or NEM-treated eyes. The results indicate that the chemical status of cellular-SH groups may influence aqueous humor outflow facility at multiple sites in the outflow pathway.     

Effects of indocyanine green injection on the retinal surface and into the subretinal space in rabbits

PURPOSE: To evaluate the effects of indocyanine green (ICG) injection on the retinal surface and into the subretinal space of rabbit eyes. METHODS: Twenty-two Dutch-belted rabbits underwent two-port vitrectomy followed by injection of ICG (5 mg/mL) on the retinal surface and into the subretinal space. Balanced salt solution (BSS) was also injected subretinally. The locations where ICG was delivered (both epiretinal and subretinal) were exposed to light from an endoilluminator for 7 minutes. The animals were examined at 1, 7, and 14 days after surgery. The eyes were studied by fluorescein angiography as well as light and electron microscopy. RESULTS: No damage was observed after epiretinal ICG injection, but subretinal ICG injection resulted in damage to the outer nuclear layer, photoreceptor inner and outer segments, and retinal pigment epithelium. This damage was more severe with longer follow-up. Control experiments without ICG, in which balanced salt solution was injected into the subretinal space or light was delivered on the epiretinal surface, demonstrated only damage to the photoreceptor outer segments. CONCLUSION: Subretinal delivery of ICG (5 mg/mL) in rabbits induces retinal pigment epithelium, photoreceptor inner and outer segment, and outer nuclear layer damage. These mechanisms of damage may explain the retinal pigment epithelium changes that are sometimes seen after ICG-assisted internal limiting membrane peeling in humans.     

Ocular fluorescein kinetics before and after vitrectomy on swine

PURPOSE: To study the quantitative effects of vitrectomy on fluorescein transport kinetics across the ocular barriers. METHODS: Thirty-six domestic swine were used in this study. Twenty anesthetized swine were given a standardized fluorescein intravenous injection immediately after unilateral vitrectomy. This was followed by one single central sample aspiration from the vitreous and the anterior chamber of both eyes in individual animals at increasing intervals up to 24 h after the injection. Fluorescein concentrations in the samples were determined by high-pressure liquid chromatography (HPLC). Eight swine underwent unilateral vitrectomy followed by anterior chamber and vitreous fluorophotometry on both eyes 1 month later. The fluorescein concentrations determined using this method were followed for 24 h. Similar examinations were performed in a control group of eight swine that did not undergo vitrectomy. Anterior chamber, vitreous, and plasma fluorescein concentration/time courses were analyzed kinetically by iterative nonlinear regression analysis. RESULTS: The barrier surrounding the anterior chamber of the eye was immediately impaired after vitrectomy, as evidenced by an increased area under the fluorescein concentration versus time curve, but the transport kinetics were restored within 1 month after surgery. The blood-retinal barrier was, however, persistently altered following vitrectomy. Transport rate and extent of drug penetration into the vitreous were increased, while drug elimination from the vitreous remained unchanged. CONCLUSION: Vitrectomy led to persistent kinetic fluorescein transport changes in the blood-retinal barrier resulting in faster and increased drug penetration to the vitreous, whereas similar alterations in the anterior chamber barrier transport were only transitory.     

Transport of fluorescein in the rabbit eye after treatment with sodium iodate

The outward active transport and the inward permeability of the blood-retinal barrier were studied in the rabbit eye after i.v. administration of sodium iodate. The active transport was evaluated from the half-time of disappearance of the vitreous fluorescein following intravitreal administration, and the inward permeability was evaluated from the vitreous concentration of fluorescein monoglucuronide after i.v. administration. The half-time of the vitreous fluorescein was 3.5 +/- 0.3 (mean +/- S.D.) hr, and 3.9 +/- 0.2 hr before and within 6 hr after iodate administration, respectively. After 24 hr, the half-time was 11.7 +/- 1.7 hr, similar to that of fluorescein monoglucuronide, 12.0 +/- 2.7 hr. The vitreous and the anterior chamber concentration of fluorescein monoglucuronide was measured at 1 hr after the i.v. dye injection. The vitreous concentration in the rabbits given iodate 3 hr before the dye injection was significantly greater than in the normal eyes, while the anterior chamber concentration was not different. Since fluorescein is rapidly metabolized to fluorescein monoglucuronide, differences in parameters determined using systemic fluorescein under two treatments or in disease states may be the result of alteration of the dynamics of fluorescein, fluorescein monoglucuronide, or both.     

Uveoscleral outflow using different-sized fluorescent tracers in normal and inflamed eyes

Sodium fluorescein and fluorescinated dextrans (FD) of selected molecular weights were combined and perfused into the anterior chamber of normal and inflamed eyes of cynomolgus monkeys. The eyes were dissected into iris, anterior and posterior uvea, anterior and posterior sclera, retina and intraocular fluids (excluding aqueous). Each tissue was homogenized and centrifuged and the supernatant was run through a gel-filtration column to separate the fluorescent tracers. Each of the resultant peaks was quantitated and facility of uveoscleral outflow was determined. In control eyes the calculated facility of uveoscleral outflow was very similar with all tracers (from 0.047-to 0.052 microliter min-1 mmHg-1) and each tracer was found in highest concentration in the anterior sclera and anterior uvea. In inflamed eyes the calculated facility of uveoscleral outflow increased two- to five-fold with each tracer (0.12-; 0.17-; 0.29-; and 0.24 microliter min-1 mmHg-1 with fluorescein, and the fluorescinated dextrans of MWs 4000, 40,000 and 150,000, respectively). Each tracer was found in the anterior sclera and uvea in inflamed eyes whereas the posterior sclera and uvea contained predominantly the higher molecular-weight tracers (MWs 40,000 and 150,000). It is concluded that iridocyclitis causes an increase in uveoscleral outflow by increasing the permeability of the anterior uvea to all tracers and fluid. Small tracers may then diffuse into uveal blood vessels or across the sclera, yielding lower values for uveoscleral outflow. Of the four tracers studied, the optimal tracer size for studying uveoscleral outflow in either normal or inflamed eyes is MW 40,000.     

Fluorescein angiographic studies of the effect of Harms' and Dannheim's trabeculotomia ab externo]

The mechanism of the outflow of the aqueous humor was investigated on 9 eyes with open angle glaucoma operated by traveculotomia ab externo. The anterior chamber was filled with 0,2% Fluorescein-Ringer-solution, before and after the operation. Comparing the fluorescein angiographic pictures it can be concluded that the effect of the operation it caused by an improvement of the outflow of the aequous humor through the system of Schlemm's canal as well as through the formation of a fistula.     

Early post-phacoemulsification hypotony as a risk factor for intraocular contamination: in vivo model

PURPOSE: To observe cataract wound dynamics and determine the risk for intraocular contamination under induced conditions of early postoperative hypotony after anterior chamber decompression for high intraocular pressure (IOP) spikes after uneventful phacoemulsification surgery. SETTING: Department of Ophthalmology, Queen's Hospital, Burton-on-Trent, United Kingdom. METHODS: In a prospective case series, 30 patients were treated with anterior chamber decompression for elevated IOP (>35 mm Hg) 1 to 2 hours after uneventful phacoemulsification through clear corneal temporal incisions. A drop of 2% fluorescein was instilled in the conjunctival sac before aqueous release to study the ocular fluid movements during and after the decompression procedure. The patterns of fluorescein movement were observed and photographed under cobalt blue light. RESULTS: Fluorescein staining of the entire corneal tunnel was observed in all 30 eyes after decompression. An immediate fluorescein flare was observed in the anterior chamber after aqueous release in 24 eyes (80%) (P<.001). Observations over several seconds after decompression found a frank influx of fluorescein-stained fluid into the anterior chamber in 12 eyes (40%) (P<.001), giving rise to an "inverse Seidel's test." An intermittent ingress of fluorescein-stained fluid continued for several minutes after the procedure in 6 eyes (20%) (P<.05). CONCLUSIONS: An incompetence of clear corneal cataract wound with intraocular contamination was observed during the period of induced hypotony after anterior chamber decompression in the early post-phacoemulsification period.