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At least 19 recordsLinked to original sources
PubMed2001

Visual deprivation stimulates the exchange of the fibrous sclera into the cartilaginous sclera in chicks.

Form deprivation myopia in chicks is a widely accepted model to study visually-regulated postnatal ocular growth. The chick sclera has a cartilaginous layer as well as the fibrous layer found in mammals. It appears that a dynamic relationship exists between these two layers during visual deprivation-induced growth. The changes in the fibrous sclera of myopic eyes, however, have not been previously described. This investigation is focused on the comparative morphological analyses of the cartilaginous and fibrous scleral changes in myopic chick eyes. The fibrous scleral changes in the posterior segment of myopic eyes were examined in detail using light and electron microscopy, and the expression of growth factors was analysed by immunohistochemistry. In the posterior segment of myopic eyes the border between the cartilaginous and fibrous layers was indistinct because of collagen bundles of the fibrous sclera that spread into the cartilaginous sclera, whereas in control eyes the distinction was clear. Various types of transitional cells, from fibroblast-like mesenchymal cells to chondrocytes, were found in the border between the cartilaginous and fibrous layers. Collagen fibrillar diameters of the fibrous sclera in the posterior segment of myopic eyes were smaller than in control, whereas those in the equatorial segment were almost the same in myopic and control eyes although the distribution of sizes was obviously different. Thus, changes in the fibrous sclera in myopic eyes of chicks seem to be similar to scleral changes in myopic eyes of mammals. The cells in the posterior sclera of myopic eyes were more intensely immunostained for TGF-beta and IGF-II than control, whereas no immunoreaction of TGF-alpha could be detected in either control or myopic eyes. These results suggest that the structural characteristics of the posterior sclera are different from those of the anterior and equatorial segments. Undifferentiated mesenchymal cells might be concentrically distributed exclusively in the innermost layer of posterior fibrous sclera. TGF-beta and IGF-II might influence cell growth, differentiation, and migration in the exaggerated scleral growth accompanying myopia.

Animals↗
PubMed2001

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 10 sec to 10 min at temperatures of 37-100 degrees 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 degrees C for 20 sec or longer, at 70 degrees C for 10 sec 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 degrees C when samples were heated for 10 min, 62-63 degrees C when heated for 1 min, and 66-67 degrees C when heated for 10 sec; the threshold exposure time at 60 degrees C was estimated to be 7-12 min. These results indicate a temperature of 60 degrees C for 1 min 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.

Adolescent↗
PubMed1997

[Repair of cornea-sclera defect by autogenous sclera graft from the same eye].

In order to rescue the serious cornea-sclera defect, normal piece of a sclera from the damaged eye was used to serve as a donor material to repair the cornea-sclera defect. Eighteen cases were treated by transplantation of sclera graft with the operation to decompress the intra-ocular tension and to perform an artificial pupil from 1979 to 1994. Because the ocular-store seriously lacks in mostly internal locality, in the 18 cases, laceration of avulsive in 5 cases, severe corneal fistula complicated to other corneal diseases in 8 cases, locolized staphyloma of aornea in 2, laceration of sclera fistula in 1. The resulte were: The repairs were all healed up in an average of 20 days. The tension returned to normal and the vision was improved. The scleral graft was fused with the cornea, and the white area form the graft tended to reduce in size gradually with increase in transparency. There was no sign of iritis and rejection reaction. Follow-up of 3 to 36 months showed that the grafting operation was simple and an easy method, at the same time, once gained effect if would prevent or cure blindness.

Adolescent↗
PubMed2003

Luxated intraocular lens fixation using anterior chamber slipknot of the haptic to the sclera: a simple procedure to fixate intraocular lens to the sclera.

PURPOSE: To describe a technique for suturing a luxated intraocular lens (IOL) in the vitreous cavity directly to the ciliary sulcus using intraocular slipknot without IOL extraction. DESIGN: Noncomparative interventional case series. MATERIALS AND METHODS: A three-port vitrectomy was performed in all cases. According to the Lewis procedure, two scleral flaps and relative sclerectomies were performed at 3 and 9 o'clock position. IOL was rescued from vitreous cavity by means of perfluorocarbon and stabilized in anterior chamber by intravitreal forceps. Corneal endothelium was preserved by a dispersive ophthalmic viscosurgical device coating. Double armed 10-0 polypropylene was introduced into the vitreous cavity through the 9 o'clock sclerotomy incision and both the needles were passed out of the eye by the 3-o'clock position sclerotomy, guided by a bent 27-gauge needle 1.5 mm from the limbus. Hooking the slipknot around the haptics of the IOL in the anterior chamber by means of vitreous forceps, the 10-0 polypropylene was pulled so that the IOL haptic was fixated onto the sulcus. The same procedure was used to fixate the opposite haptic to the ciliary sulcus at the opposite position. RESULTS: In all four cases, the IOL fixated stably and remained well positioned. No significant intraoperative or postoperative complications occurred. CONCLUSIONS: This technique enables secure fixation of the luxated IOL in the vitreous without extracting it.

Adult↗
PubMed1989

Distribution of complement in the sclera.

In the present study, we compared hemolytic activities of C1, C4, C2, C3, C5, C6 and C7 in the anterior and posterior sclera. Additionally, we used radial immunodiffusion to measure levels of Factor B, IgG, IgA and albumin in the anterior and posterior sclera. Except for C1, complement levels were significantly higher in the posterior than anterior sclera. Additionally, levels of immunoglobulins as well as albumin were significantly higher in the posterior than anterior sclera. These results suggest that the posterior sclera has a better adjacent vascular supply than the anterior sclera. On the other hand, the results of this study show that the anterior sclera has more C1, the recognition unit of the classical pathway, than the posterior sclera. Because there is nearly twice as much C1 in the anterior sclera, it may be easier for antigen-antibody complexes, whether formed in the sclera itself or derived from the neighboring vessels, to set off the complement cascade in the anterior sclera. This finding may help explain why scleritis associated with immune complex disease is more common in the anterior than posterior sclera.

Adult↗
PubMed1997

Nonsurgical and surgical methods of sclera reinforcement in progressive myopia.

PURPOSE: As shown by the clinical picture of progressive myopia, derangements in biomechanical properties of sclera may be more or less manifested. The study aims at the development of a discriminating approach to their correction. METHODS: Patients with the condition were given a sclera strengthening injection, in which a dose of liquid polymeric composition is injected under the Tenon's capsule on the scleral surface. After polymerization, the composition forms over the scleral surface a layer of elastic foamed gel. RESULTS: Complex experiments on 146 rabbit eyes showed that the injected material promotes collagen formation. Gradually dissolving, the gel stimulates the growth of connective tissue on the surface of the sclera, whose stress-strain parameters improve. A thorough clinical study of 240 eyes of patients aged 8-25 years with progressive 6-10 D myopia showed that the refraction remained stable in 79.6% eyes 1 year after the sclera strengthening injection and in 52.9% cases 4-9 years after the sclera strengthening injection. At the same time, fellow intact eyes have shown, respectively, 40.3% and 13.3% of myopia stabilization, and 212 untreated eyes of the control group 26.0% and 11.1%, respectively. 612 children and adolescents with high myopia and a yearly progression of over 1.0 D were subjected to a scleroplastic operation. It was found that the myopia remained stable in 95.7% cases 1 year after the operation, and in 71.9%, 7 years after the operation. If myopia progression continued after a sclera strengthening injection or scleroplasty, a second procedure was performed. Second interventions were effected on 118 eyes of 102 patients, including 42 eyes where a sclera strengthening injection followed a sclera strengthening injection, 27 eyes where scleroplasty followed a sclera strengthening injection, 31 eyes where a sclera strengthening injection followed scleroplasty, and 18 eyes on which a second scleroplasty was performed. Second interventions provide a double decrease of myopia progression rate and, in 63% of patients, stop the progression altogether. CONCLUSION: It can be concluded that nonsurgical and surgical techniques of correcting the biomechanical properties of sclera for the treatment of progressive myopia as well as discriminative methods of determining the indications to these procedures have proven to be effective.

Acrylamides↗
PubMed1999

Biochemical and ultrastructural changes in rabbit sclera after treatment with 7-methylxanthine, theobromine, acetazolamide, or L-ornithine.

AIMS: To examine a possible effect of 7-methylxanthine, theobromine, acetazolamide, or L-ornithine on the ultrastructure and biochemical composition of rabbit sclera. METHODS: Groups of pigmented rabbits, six in each group, were dosed during 10 weeks with one of the substances under investigation, and one untreated group was the control. Samples of anterior and posterior sclera were taken for determination of hydroxyproline, hydroxylysine, proline, proteoglycans, uronic acids and dermatan sulphate, chondroitin sulphate, and hyaluronic acid. Sections were examined with electron microscopy, and the diameter of the individual collagen fibrils was measured. RESULTS: Treatment with theobromine produced a significant increase in the contents of hydroxylysine, hydroxyproline, and proline in both anterior and posterior sclera, while 7-methylxanthine increased the contents of hydroxyproline and proline selectively in posterior sclera. Acetazolamide, on the other hand, significantly decreased the contents of hydroxyproline and proline in samples from anterior sclera. Uronic acids in both anterior and posterior sclera were significantly reduced by treatment with 7-methylxanthine, and L-ornithine significantly reduced uronic acids in posterior sclera. An inverse correlation between contents of hydroxyproline and uronic acids was found. The mean diameter of collagen fibrils was significantly higher in the posterior sclera from rabbits treated with 7-methylxanthine or theobromine, and significantly lower in rabbits treated with acetazolamide or L-ornithine compared with controls. In the anterior sclera, fibril diameter was significantly reduced in all treatment groups compared with controls. A positive, significant correlation between fibril diameter and content of hydroxyproline and proline was found in posterior sclera. CONCLUSION: 7-Methylxanthine, a metabolite of caffeine, increases collagen concentration and the diameter of collagen fibrils in the posterior sclera, and may be useful for treatment or prevention of conditions associated with low level and/or inferior quality of scleral collagen, such as axial myopia, chronic open angle glaucoma, and possibly neovascular age related macular degeneration. The apparent loss of collagen induced by chronic treatment with acetazolamide should be taken into consideration as a potentially harmful side effect. These results may indicate that scleral biochemistry and ultrastructure are influenced by the retinal pigment epithelium. One possible explanation is that the scleral fibroblasts which produce the collagen are sensitive to changes in the physiological electric field created by the retinal pigment epithelium.

Acetazolamide↗
PubMed1998

Glycoproteins of trabecular meshwork, cornea and sclera.

PURPOSE: To analyse high-molecular-weight matrix glycoproteins in trabecular meshwork, cornea and sclera using SDS/PAGE and immuno- and lectin blotting. METHOD: Extracts of normal trabecular meshwork (TM), cornea and sclera were analysed under reducing conditions on SDS/ PAGE. Western blots were stained for total protein, and major high-molecular-weight components were identified by immunoblotting with antibodies to fibronectin (FN) and type VI collagen. Lectin blotting with PSA, MPA and DSA identified some of the glycoprotein glycans. RESULTS: FN antibody bound to the 240 kDa band in TM, cornea and sclera. Type VI collagen antibody bound more strongly to one band and less so to two other bands at approximately 200 kDA in normal TM and to a ladder of bands in cornea and sclera. PSA and DSA bound at 240, 200 and 140 kDa in TM, cornea and sclera. MPA bound at 240, 200 and 140 kDa in TM and at 240, 200 and approximately 120 kDA in cornea and sclera. CONCLUSIONS: FN is a component of the band at 240 kDA in TM, cornea and sclera. Normal TM was found to contain relatively more of one of the isoforms of the alpha 3 (VI) chain whilst cornea and sclera contained all the alpha 3 (VI) isoforms. Complex N-linked bi/tri-antennary glycans were localised in FN and the alpha 1, alpha 2 and alpha 3 (VI) chains in TM, cornea and sclera. O-linked glycans (identified by MPA binding) were located in FN and alpha 3 (VI) chains of TM, cornea and sclera.

Aged↗
PubMed2002

Acute scleral thinning after pterygium excision with intraoperative mitomycin C: a case report of scleral dellen after bare sclera technique and review of the literature.

PURPOSE: To describe a patient with scleral dellen after pterygium excision with intraoperative mitomycin C. METHODS: Case report and MEDLINE review of the medical literature on scleral dellen after bare sclera technique. RESULTS: A 48-year-old man had a left nasal pterygium excised by the bare sclera technique with intraoperative mitomycin C. Eight days after surgery, the patient noticed a small black spot in the bare sclera area with mild irritation. Slit-lamp examination revealed a focal area of extreme thinning, centered on the nonepithelialized bare sclera, surrounded by edematous conjunctiva. The ciliary body was visible through the thin and dry scleral lesion. After topical lubricant therapy, the scleral lesion appeared normal thickness and white in color 3 days later. Therapy was continued until the sclera epithelialized. CONCLUSIONS: Scleral dellen is an early postoperative complication of bare sclera technique owing to delayed conjunctival wound closure. Hydration of the thinned sclera will rapidly thicken it. However, medical therapy should be continued until the surrounding conjunctiva has flattened and the sclera has epithelialized. Surgical wound closure is an alternative management and may be the way to prevent scleral dellen formation after bare sclera technique. All patients after bare sclera surgery should be followed up until the conjunctival wound has healed. If delayed healing is found, frequent artificial tears, patching, or surgical intervention is necessary.

Acute Disease↗
PubMed1999

Gelatinase A and TIMP-2 expression in the fibrous sclera of myopic and recovering chick eyes.

PURPOSE: Myopia, or nearsightedness, is characterized by excessive lengthening of the ocular globe and is associated with extracellular matrix remodeling in the posterior sclera. The activity of gelatinase A, a member of the matrix metalloproteinase family, has been shown to increase in the posterior sclera during the development of induced myopia in several species. In the present study, the distribution and relative expression of gelatinase A and its associated inhibitor, tissue inhibitor of metalloproteinases (TIMP)-2, were measured within the fibrous scleras of experimentally myopic (form-deprived) eyes, control eyes, and eyes recovering from form deprivation to better understand the mechanisms that regulate scleral remodeling and the rate of ocular elongation. METHODS: Total RNA was extracted from the posterior scleras of form-deprived chick eyes, eyes recovering from deprivation myopia, and paired contralateral control eyes, and subjected to northern blot analysis analyses using cDNA probes to chicken gelatinase A and TIMP-2. The distribution of gelatinase A and TIMP-2 mRNAs was evaluated by in situ hybridization on frozen sections of chick scleras using 33P-labeled RNA probes. Gelatinase A activity within the fibrous scleras of form-deprived eyes and paired contralateral recovering eyes was evaluated by gelatin zymography. RESULTS: Northern blot analysis indicated that the relative expression of gelatinase A was increased by 128% in deprived eyes (P = 0.009), whereas after 1 day of recovery, levels were decreased by 80% in scleras from recovering eyes (P = 0.005). In contrast, TIMP-2 expression was significantly decreased (-53%, P = 0.027) in the posterior scleras of form-deprived eyes. No significant differences were detected in levels of TIMP-2 expression between recovering eyes and paired control eyes. In situ hybridization indicated that most of the gelatinase A transcripts were present in the fibrous layer of the posterior scleras from form-deprived and recovering eyes. CONCLUSIONS: Changes in the steady state levels of gelatinase A and TIMP-2 mRNA lead to changes in gelatinase activity within the fibrous sclera and mediate, at least in part, the process of visually regulated ocular growth and scleral remodeling.

Animals↗
PubMed1995

Increased latent gelatinase activity in the sclera of visually deprived chicks.

PURPOSE: Gelatinase activity was measured in the normal chick sclera and in sclera of form-deprived (myopic) eyes to assess the role of this metalloproteinase in ocular elongation associated with experimental myopia. METHODS: Gelatinases were extracted from anterior and posterior regions of normal chick sclera and sclera from eyes that had been form-vision deprived for 11 days. Gelatinase activity in the extracts was determined by measuring the digestion of 3H-gelatin after incubation with the extracts in the absence or presence of 1 mM aminophenylmercuric acetate (APMA) to activate latent gelatinases. Scleral gelatinases were characterized by sodium dodecyl sulfate-polyacrylamide gel electrophoresis gelatin zymography and immunoprecipitation analyses. RESULTS: No significant differences were detected in gelatinase activity between normal and deprived posterior sclera in the absence of APMA. However, when scleral extracts were incubated with APMA, extracts from the posterior sclera of deprived eyes contained significantly more gelatinase activity than paired controls (+127%, P = 0.0105). In contrast, no differences in active or latent gelatinase activity were detected in extracts from the anterior sclera. Removal of tissue inhibitors of metalloproteinases (TIMP) from control scleral extracts by reduction and alkylation resulted in a 222% increase in gelatinolytic activity after APMA-activation (P < or = 0.001), whereas similar treatment of deprived scleral extracts resulted in only a 76% increase in gelatinolytic activity (P < or = 0.001). A 65/58-kd doublet was the major gelatinolytic species from control and deprived posterior sclera that represent the proenzyme and active forms of the 72-kd gelatinase (MMP-2). CONCLUSIONS: These data indicate that visual deprivation is associated with an increased amount of the 72-kd progelatinase and a decreased amount of TIMP within the posterior sclera. Therefore, an imbalance between the levels of 72-kd progelatinase and its inhibitor may play a role in the remodeling processes of the posterior sclera during the development of form-deprivation myopia.

Animals↗
PubMed1991

Increased aggrecan (cartilage proteoglycan) production in the sclera of myopic chicks.

A previously characterized chick model of myopia was used to evaluate biochemical changes in the sclera which are associated with ocular enlargement and myopia. Chicks were monocularly occluded for 10 days and the DNA, hydroxyproline, and glycosaminoglycan contents of the sclera were compared between the normal and the myopic eyes. No significant differences could be detected in total DNA or hydroxyproline content. There was, however, a 34% increase in glycosaminoglycans and a 20.7% decrease in cell density within the posterior sclera of myopic eyes. The biosynthesis of scleral proteoglycans was determined by measuring 35SO4 incorporation in the sclera of chicks visually occluded for 5, 10, and 15 days. No differences could be detected in 35SO4 incorporation into the cornea or the anterior sclera. However, 35SO4 incorporation was significantly increased in the posterior sclera of myopic eyes by 64% at Day 5, 39% at Day 10, and 49% at Day 15. When fractionated on Sepharose CL-4B, scleral proteoglycans were resolved into two peaks which were identified by Western blot analysis as aggrecan (cartilage proteoglycan) and decorin. Furthermore, Western blot and dot blot analyses indicated that significantly more aggrecan core protein was present in the sclera of myopic eyes compared with equivalent amounts of sclera from control eyes. These results indicate that increased synthesis and accumulation of aggrecan, which increases the volume of extracellular matrix in the posterior sclera, are responsible for the ocular enlargement observed in this model of myopia.

Aggrecans↗
PubMed1999

Residual ethanol content of donor sclera after storage in 95% ethanol and saline rinse of various durations.

PURPOSE: Some surgeons are wary of using alcohol-preserved sclera for allografts because they fear a toxic effect on surrounding tissue after placement. We set out to determine the amount of ethanol remaining in scleral allograft material after storage in 95% ethanol. METHODS: Sixty half scleras from 30 donors were preserved in 95% ethanol for an average of 31+/-14 days (range, 11 to 50 days). Rehydration was performed by soaking each half sclera in 4 ounces of balanced salt solution. Half scleras were randomly assigned to six groups of 10 each. Assays for ethanol were performed on the following groups: no balanced salt solution soak and balanced salt solution soak for 10 minutes, 20 minutes, 30 minutes, 40 minutes, and 50 minutes. Ethanol assay was performed by Headspace Gas Space Chromatography at ChemaTox Laboratory, Inc, Boulder, Colorado. RESULTS: The 10 half scleras without balanced salt solution soak had a mean ( SD) ethanol level of 175+/-14.1 mg per g of sclera. After 10 minutes of balanced salt solution s oak, the level decreased to 7.57+/-1.56 mg per g, then 3.77+/-3.02 mg per g at 20 minutes, 1.59+/-0.61 mg per g at 30 minutes, 1.07+/-0.30 mg per g at 40 minutes, and 0.96+/-0.26 mg per g at 50 minutes. Approximately 96% of the ethanol is leeched out of the half sclera by 10 minutes and 98% by 20 minutes. CONCLUSIONS: For sclera preserved in 95% ethanol, soaking in balanced salt solution for 20 minutes or longer leeches approximately 98% of the ethanol from the preserved donor sclera.

Drug Residues↗