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PubMed1997

Proteoglycans in the human sclera. Evidence for the presence of aggrecan.

PURPOSE: The proteoglycans synthesized and accumulated within the adult human sclera (aged 50 to 80 years) were identified by their size, glycosaminoglycan side chains, and core proteins in an effort to characterize the proteoglycan content of the human sclera. METHODS: Sclerae, unlabeled, or radiolabeled in organ culture with 35SO4 or 3H-proline, were extracted in 4M guanidine-HCl and separated by Sepharose CL-2B and Superose 6 forced-pressure liquid chromatography. Peak fractions, identified by glycosaminoglycan content or radioactivity, were pooled and subjected to G-50 chromatography or sodium dodecyl sulfate-polyacrylamide gel electrophoresis before and after digestion with specific glycosidases. Scleral proteoglycan core proteins were identified in Western blot analysis using specific antisera to decorin, biglycan, and aggrecan. Reverse transcription-polymerase chain reaction analyses were carried out on human scleral fibroblast RNA to confirm the transcription of one scleral proteoglycan. Proteoglycans were localized on sections of scleral tissue using specific antisera. RESULTS: After chromatography on CL-2B, scleral proteoglycans could be resolved into three major peaks, PG-1, PG-2, and PG-3. The largest scleral proteoglycan, PG-1, contained chondroitin sulfate and keratan sulfate glycosaminoglycan side chains. Results of Western blot analyses indicated that the core protein of PG-1 is the aggrecan core protein, migrating at approximately 350 kDa. Reverse transcription-polymerase chain reaction analyses confirmed that human scleral fibroblasts transcribe aggrecan in vitro and in vivo. PG-2 and PG-3 were identified as biglycan and decorin in Western blot analyses using antibiglycan and antidecorin antibodies, respectively. Immunostaining results indicated that aggrecan, biglycan, and decorin are distributed throughout the thickness of the human sclera. CONCLUSIONS: The adult human sclera contains three major proteoglycans; aggrecan, biglycan, and decorin. It is likely that these proteoglycans contribute to the structural properties of the sclera and that the ratios of these proteoglycans will change with age, specific region, and condition of the sclera.

Aged↗
PubMed2003

Differential effects of aging on transport properties of anterior and posterior human sclera.

The transport properties and composition of 44 pairs of human sclera, 37-91 years were compared. Solute transport, diffusion and partition coefficients of posterior sclera for solutes ranging in mass from 0.023-70kDa were higher than those of anterior sclera; the posterior region was also more hydrated. The differences in partition coefficient between anterior and posterior sclera became more pronounced as solute molecular weight increased. Partition coefficients and hydration of both regions decreased with increasing age. Chondroitinase ABC digestion, which removed the majority of glycosaminoglycans, increased partition coefficients of both regions significantly. These results suggest that for regions of equal scleral thickness, neglecting the influence of vascular factors, drug delivery will be more readily achieved across the posterior sclera than the anterior sclera in the age group studied and that, for both regions, ease of delivery will decrease with decreasing age.

Adult↗
PubMed1986

Blue sclerae: a common sign of iron deficiency?

169 hospital inpatients were studied to assess the association of blue sclerae with iron-deficiency anaemia. Three observers independently graded the signs of blue sclerae and mucosal pallor as absent, equivocal, definite, or striking. Blue sclerae were seen more often in patients with iron-deficiency anaemia (40/46, 87%) than in those with other anaemias (2/28, 7%; p less than 0.001) or without anaemia (5/95, 5.3%; p less than 0.001). The specificity of blue sclerae in iron-deficiency anaemia was 0.94 with a sensitivity of 0.87. By comparison, mucosal pallor was noted in only 30% of patients with iron-deficiency anaemia, with a specificity of 0.96 and a sensitivity of only 0.20 (p less than 0.001). The presence of blue sclerae was unaffected by age, sex, or colour of iris. Blue sclerae appear to be a good indicator of iron deficiency and should become a regular part of clinical examination.

Aged↗
PubMed2002

Central corneal thickness is lower in osteogenesis imperfecta and negatively correlates with the presence of blue sclera.

BACKGROUND: Osteogenesis imperfecta (OI) is a rare, autosomal-inherited, connective tissue disorder characterised by bone fractures, deafness and blue sclera. Additional ocular findings are decreased ocular rigidity, myopia, glaucoma, keratoconus, corneal opacity, small corneal diameter and congenital Bowman's layer agenesis. PURPOSE: This cross-sectional, masked, case-control study aimed to assess whether central corneal thickness (CCT) is affected in patients with OI and to focus on the clinical significance of scleral blueness. MATERIALS AND METHODS: Twenty-three children with OI (13 boys, 10 girls) and 15 age-, sex- and refraction-matched healthy control subjects (eight boys, seven girls) were assessed for CCT by ultrasound pachymetry. The CCT was compared between two different patient subgroups (type-I OI with blue sclera, n = 12; type-IV OI without blue sclera, n = 11). Mann-Whitney U-test or analysis of variance was used as indicated and only right eyes of each subject were included in statistical analysis. Results were expressed as mean +/- S.D. and statistical significance was taken as p < 0.05. RESULTS: Mean age and sex distribution was similar between the groups (10.1+/-2.5 vs 9.8+/-1.8 years, p > 0.05). Patients with OI had significantly lower CCT (459.5+/-24.6 microm) than in control subjects (543.6+/-21.4 microm; p < 0.001). The CCT was below 500 microm in 22 of 23 children (95.6%) with OI, 15 of which (65.2%) were below 450 microm. In contrast, CCT was over 500 microm in all eyes in the control group. Type-I OI eyes with blue sclera had significantly (p = 0.005) lower CCT readings (446.5+/-16.3 microm) than type-IV OI eyes without blue sclera (473.6+/-25.0 microm). Mean keratometric values were similar between the groups (44.2+/-1.7 vs 43.8+/-1.6 dioptre, p > 0.05). Mean cycloplegic refraction was similar between the groups (-0.32+/-0.5 vs -0.18+/-0.4 dioptre; p > 0.05), although five of 23 OI patients had myopia, and mean intraocular pressure was lower in OI patients than controls (12.7+/-1.8 mmHg vs 15.6+/-1.9 mmHg; p < 0.001). CONCLUSIONS: The CCT is thinner and negatively correlated with the blueness of the sclera in patients with OI. The CCT readings may therefore be of utmost importance in the diagnosis of OI. An ophthalmologist should be aware of an artificially low intraocular pressure measurement in such patients. In addition, when considering a keratorefractive treatment, CCT must be evaluated carefully to avoid unexpected results or complications. Sturdy protective spectacles should be prescribed to those who are not bed bound. Possible correlation of low CCT with biochemical changes in scleral collagen or systemic parameters awaits further investigation.

Adolescent↗
PubMed1980

[The role of the sclera in the pathogenesis of progressive myopia (author's transl)].

Different parts of the sclera have different biochemical and biomechanical properties. It was shown that the sclera is much more extensible in the meridional than in the equatorial direction; this extensibility of the sclera was especially marked in myopic eyes. Bulbar stretching is probably due to an accumulation of residual microdeformations in the sclera as a result of its periodical overload. In scleras of myopic eyes structural anomalies were found which might be explained by an incomplete fibrillogenesis. The deterioration of the biomechanical properties of the sclera in myopia seems to be linked to a metabolic disturbance of the acid mucopolysaccharides.

Adolescent↗
PubMed2004

Latanoprost eye drops increase concentration of glycosaminoglycans in posterior rabbit sclera.

PURPOSE: Glycosaminoglycans are important components of ocular tissues such as the sclera. The pressure reducing effect of a new antiglaucoma drug, latanoprost, is based on an increase in the uveo-scleral outflow by way of modulation of the intracellular matrix of the ciliary body. The purpose of the study was to test the effect of latanoprost on the content of glycosaminoglycans in rabbit cornea and sclera. METHODS: Twelve rabbits were studied. Six rabbits were treated for 12 weeks with latanoprost eye drops and 6 with hydroxypropylmethylcellulose, dextran 70 eye drops for control. Samples were taken from cornea and anterior, lateral, and posterior sclera. Glycosaminoglycans were determined quantitatively by spectrophotometry (uronic acids). RESULTS: A significant increase in the concentration of uronic acids was found in all three localisations of sclera from latanoprost-treated animals. The increase was 26%, 24%, and 20% in anterior, lateral, and posterior sclera, respectively. CONCLUSIONS: Long-term treatment with latanoprost induces biochemical changes in sclera. The results indicate that topically applied latanoprost reaches the posterior parts of the rabbit eye.

Animals↗
PubMed1999

Bovine pericardium versus homologous sclera as wrapping materials for hydroxyapatite ocular implants: an animal study.

PURPOSE: We compared bovine pericardium and homologous sclera as wrapping materials for hydroxyapatite (HA) ocular implants in enucleated New Zealand white rabbits. METHODS: Eighteen rabbits were unilaterally enucleated and the sockets implanted with 10-mm HA spherical implants. Six implants were wrapped with homologous sclera, 6 with bovine pericardium, and 6 were not wrapped. The rabbits were killed 7 weeks later and the sockets were examined clinically for inflammation and implant exposure. Exenterated specimens were assessed histopathologically for inflammation and vascularization. RESULTS: No clinical evidence of implant exposure or extrusion was detected in rabbits receiving sclera or bovine pericardium wrapped implants. Histopathologically, the bovine pericardium displayed more inflammation in its outer portion, as well as more disruption of its lamellar arrangement than did the sclera. Fibrovascular in-growth was complete in all wrapped implants. CONCLUSION: Bovine pericardium behaves similar clinically to homologous sclera as a wrapping material for spherical HA ocular implants in a rabbit model, and may represent a reasonable alternative to sclera in such procedures in humans.

Animals↗
PubMed2003

Bovine pericardium versus homologous sclera as a wrapping for hydroxyapatite orbital implants.

PURPOSE: To report our experience with bovine pericardium as a wrapping material for hydroxyapatite orbital implants after enucleation and to compare the exposure rates of the implants wrapped with bovine pericardium versus donor sclera. METHODS: We retrospectively reviewed the records of all patients who received bovine pericardium-wrapped or donor sclera-wrapped hydroxyapatite implant after primary enucleation between March 1995 and December 2001. RESULTS: Of the 26 patients who received donor sclera-wrapped implants after enucleation, 1 (3.8%) had implant exposure. Of the 26 patients who received bovine pericardium-wrapped implants after enucleation, 6 (23%) had implant exposure. The incidence of implant exposure with the use bovine pericardium wrapping material was found to be significantly higher than with sclera (P = 0.05). Six of the 7 implant exposures were noted in the first 6 months after placement of the orbital implant. Five of the 6 exposed bovine pericardium-wrapped hydroxyapatite implants were associated with socket infection. The case of exposure of the sclera-wrapped implant was treated conservatively by observation. Six patients who had exposure of bovine pericardium-wrapped implants required multiple repairs because of recurrent exposures. Four of these patients eventually required removal of the implant. CONCLUSIONS: Despite the advantages of using bovine pericardium as a wrapping material for hydroxyapatite orbital implants, we observed a significantly higher incidence of exposure with bovine pericardium compared with donor sclera in the early postoperative period. Use of bovine pericardium as a wrapping material for orbital implants should be avoided unless some future modifications of the technique can be developed to prevent such complications.

Adolescent↗
PubMed2006

Identification of resident and inflammatory bone marrow derived cells in the sclera by bone marrow and haematopoietic stem cell transplantation.

AIMS: To characterise bone marrow derived cells in the sclera under normal and inflammatory conditions, we examined their differentiation after transplantation from two different sources, bone marrow and haematopoietic stem cells (HSC). METHODS: Bone marrow and HSC from green fluorescent protein (GFP) transgenic mice were transplanted into irradiated wild-type mice. At 1 month after transplantation, mice were sacrificed and their sclera examined by histology, immunohistochemistry (CD11b, CD11c, CD45), and transmission and scanning electron microscopy. To investigate bone marrow derived cell recruitment under inflammatory conditions, experimental autoimmune uveitis (EAU) was induced in transplanted mice. RESULTS: GFP positive cells were distributed in the entire sclera and comprised 22.4 (2.8)% (bone marrow) and 28.4 (10.9)% (HSC) of the total cells in the limbal zone and 18.1 (6.7)% (bone marrow) and 26.3 (3.4)% (HSC) in the peripapillary zone. Immunohistochemistry showed that GFP (+) CD11c (+), GFP (+) CD11b (+) cells migrated in the sclera after bone marrow and HSC transplantation. Transmission and scanning electron microscopy revealed antigen presenting cells among the scleral fibroblasts. In EAU mice, vast infiltration of GFP (+) cells developed into the sclera. CONCLUSION: We have provided direct and novel evidence for the migration of bone marrow and HSC cells into the sclera differentiating into macrophages and dendritic cells. Vast infiltration of bone marrow and HSC cells was found to be part of the inflammatory process in EAU.

Animals↗
PubMed2000

[Collagen fibrils in nanophthalmic sclerae].

PURPOSE: To examine collagen fibrils in 3 nanophthalmos sclerae and to compare them with normal control sclerae morphometrically. MATERIALS AND METHODS: Three cases of nanophthalmos associated with uveal effusion were studied. When sclerectomy was performed, scleral specimens were collected and fixed with 3% glutaraldehyde/2.5% paraformaldehyde. After epon-embedding and ultrathin sectioning, they were examined by transmission electron microscopy. Collagen fibrils from both nanophthalmos and normal control sclerae were compared in diameters and numbers per micron 2 areas. RESULTS: All scleral tissues from the three cases were associated with irregularly woven and unclear collagen bundles. Several abnormal findings, such as twisting or fraying, were also detected in a few collagen fibrils. The diameter and density of normal-appearing collagen fibrils that occupied most areas of nanophthalmos sclerae were the same as those from normal control sclerae morphometrically. CONCLUSIONS: Although nanophthalmos sclerae even with uveal effusion showed thick irregular collagen bundles and a few abnormal collagen fibrils, most collagen fibrils appeared the same as normal controls.

Adult↗
PubMed2001

Enhanced FGF-2 movement through human sclera after exposure to latanoprost.

PURPOSE: To determine whether exposure of sclera to latanoprost acid alters transscleral permeation by FGF-2. METHODS: Pieces of human sclera were isolated from donor eyes after death, placed in organ culture, and exposed to 50 to 200 nM latanoprost acid or vehicle for 3 days. Transscleral permeability was then assessed by placing each scleral piece into a Ussing apparatus and measuring the amount of FGF-2 that moves from the orbital side to the uveal side of the scleral piece. Transscleral permeation by 10-kDa tetramethylrhodamine-dextran also was determined, for comparison. RESULTS: Transscleral permeation by FGF-2 through sclera that had been incubated with vehicle was 1.53 +/- 0.86 x 10(-8) cm/sec. Transscleral permeation by 10-kDa tetramethylrhodamine-dextran was 1.04 +/- 0.39 x 10(-6) cm/sec. FGF-2 permeation of sclera exposed to 50, 100, and 200 nM latanoprost acid was increased by an average of 48% +/- 62%, 100% +/- 108%, and 108% +/- 79%, respectively, compared with sclera exposed to vehicle (n = 13; P < 0.05). Scleral permeation by 10-kDa dextran after exposure to 50, 100, or 200 nM latanoprost acid was significantly increased by 42% +/- 36%, 59% +/- 51%, and 65% +/- 49%, respectively (n = 14; P < 0.05). The ratio of dextran to FGF-2 permeation was approximately 90 and did not vary with 50, 100, or 200 nM latanoprost acid (P = 0.93, ANOVA). CONCLUSIONS: Exposure of sclera to latanoprost acid increases transscleral permeation by FGF-2 in human scleral organ cultures. Because this increase parallels the increased scleral permeability caused by dextran, it may reflect a general enhancement of permeability, a possibility that future in vivo studies should explore.

Aged↗
PubMed2006

Characterization of the integrin receptor subunit profile in the mammalian sclera.

PURPOSE: During the increased eye growth that results in myopia, the sclera undergoes biochemical and biomechanical remodeling. The cell surface integrin receptor family has important roles during tissue remodeling, regulating the extracellular matrix environment and cellular biomechanical properties. As integrin receptors may have a role in remodeling during myopia, this study detailed subunit gene expression in the mammalian sclera. METHODS: Several tissues, including sclera, were isolated from the tree shrew, a mammalian model used in eye growth studies. Total RNA was purified, reverse transcribed and primers for the alpha- and beta-integrin subunits were designed to the published human sequence in areas of high inter-species homology. PCR was used to amplify products of predetermined size and all tree shrew integrin subunits were sequenced to confirm their identity. Multiple PCR conditions were used to identify the scleral integrin subunits, and positive control tissues were included to reduce the possibility of false negative results. RESULTS: Integrin PCR products corresponding to the beta1-, beta4-, beta5-, and beta8-integrin subunits and the alpha-integrin subunits, alpha1-6-, alpha9-11- and alphav-integrin were identified in the sclera and in scleral fibroblast cultures. The respective sequences showed a high identity (>81%) to their human counterparts. The beta2-, beta3-, beta6-, beta7-, alpha7-, and alpha8-integrin subunits were not detected in tree shrew scleral samples, despite being present in the respective positive controls. Association of the 4 beta-integrin subunits with the 10 alpha-integrin subunits suggests that the mammalian sclera is capable of expressing 13 of the 24 identified integrin receptors. CONCLUSIONS: This is the first systematic description of the integrin subunit expression profile in the sclera. Due to the multiple roles of integrin receptors during tissue remodeling, the identification of these scleral integrins is an important preliminary step in determining the role of these receptors during normal eye growth and myopia development.

Animals↗
PubMed1998

Proteoglycan turnover in the sclera of normal and experimentally myopic chick eyes.

PURPOSE: The turnover of chick scleral proteoglycans from control and form-vision deprived (myopic) eyes was compared in vivo and in explant cultures to determine whether proteoglycan degradation is altered during the development of myopia and to characterize the mechanism of proteoglycan turnover in the sclera. METHODS: Seven-day-old chicks were radiolabeled via an intraperitoneal injection of 35SO4, and monocular form deprivation was induced 48 hours later. After 1, 2, and 3 weeks of form deprivation, birds were killed, and the amount of 35SO4-proteoglycans remaining in different scleral regions was measured in control and deprived eyes. Posterior sclera were also radiolabeled in organ culture containing 35SO4, and radiolabeled scleral proteoglycans were chased into unlabeled medium for 0 to 11 days. 35SO4-labeled proteoglycans within the scleral matrix and those released into the medium were characterized by Sepharose CL-2B chromatography and western blot analysis. RESULTS: The biological half-life of scleral proteoglycans was significantly shorter within the posterior pole of form-deprived eyes (t1/2 = 7.212 days) compared with the same region of control eyes (t1/2 = 9.619 days; P < 0.001), whereas no differences in turnover rates were seen in the anterior sclera or equatorial sclera. When posterior scleral punches were placed in organ culture, 35SO4-labeled proteoglycan turnover rates were similar for control and form-deprived eyes. Chromatographic and western blot analyses indicated that approximately 80% of the total 35SO4 within the posterior sclera is incorporated into the aggrecan. Western blot analyses of aggrecan core protein released into the medium by control and form-deprived scleral punches indicated that the core protein was degraded into a series of smaller fragments of Mr = 102 to 220 kDa. A specific antiserum (anti-FVDIPEN) detected the presence of a 50-kDa C-terminal aggrecan fragment released into the medium, which was generated by the action of the matrix metalloproteinase gelatinase A and/or stromelysin. CONCLUSIONS: The turnover rate of 35SO4-labeled scleral proteoglycans is vision dependent and is accelerated in the posterior sclera of chick eyes during the development of experimental myopia. The loss of proteoglycans from the scleral matrix involves proteolytic cleavage at various sites along the aggrecan core protein through the action, at least in part, of gelatinase A and/or stromelysin.

Aggrecans↗
PubMed2003

Pterygium surgery with mitomycin C: how much sclera should be left bare?

PURPOSE: To evaluate the effect of covering the sclera with conjunctiva during surgical treatment of pterygium on the rate of postoperative complications, cosmetic outcome, and risk of recurrence. METHODS: A comparative, prospective clinical design was used. The study population consisted of 371 consecutive patients with unilateral primary advanced pterygium. All underwent bare sclera technique for pterygium excision. At completion of surgery, topical mitomycin C 0.02% was applied for 5 minutes. In the first 189 patients (group A), the conjunctiva was sutured to the sclera 2 mm from the limbus. The next 146 patients (group B), the conjunctiva was sutured at the limbus, covering the whole scleral postexcision defect. In the last 36 patients (group C), the conjunctiva remained unsutured to the sclera. The patients were followed for complications, cosmetic outcome, and recurrence for 26 months. RESULTS: After 26 months, 12 patients in group A (6.35%), 10 in group B (6.85%), and 9 in group C (25%) had recurrent pterygium. There were no cases of acute drug toxicity or scleral melting. Treatable delen were noted in 2 patients in group A (1.05%), 2 (1.36%) in group B, and 9 (25%) in group C. The cosmetic appearance was much better in group A than in groups B and C. CONCLUSIONS: Leaving the whole sclera uncovered in pterygium surgery places patients at high risk of complications and recurrence. There is no difference in complications and recurrence between covering the whole sclera with conjunctiva and leaving 2 mm bare, although the latter yields a more esthetic outcome.

Administration, Topical↗
PubMed1994

Regional proteoglycan synthesis in the sclera of experimentally myopic chicks.

Proteoglycan distribution and synthesis were compared in the sclera of normal and 10-day-form-vision-deprived (myopic) chick eyes using immunocytochemical, biochemical and autoradiographic techniques. Immunostaining with specific antibodies indicated that decorin is present in both the fibrous and cartilaginous layers of chick sclera, while aggrecan localizes only to the cartilaginous layer. For biochemical analyses of proteoglycan synthesis, sclera were isolated from control and 10-day-form-vision-deprived eyes and radiolabeled in organ culture with 35SO4. Proteoglycan synthesis was significantly increased only within a 6.5-mm-diameter button from the posterior pole of deprived eyes (+113%, P = 0.04), while no significant differences were detected in anterior and equatorial regions of control and deprived eyes. Chromatographic analyses of newly synthesized proteoglycans indicated that form-deprivation stimulates the synthesis of a large chondroitin/keratan sulfate proteoglycan (+77.47%), eluting at the position of aggrecan, as well as smaller chondroitin sulfate and keratan sulfate proteoglycans (+91.05%), which coelute with decorin. Autoradiographic analysis of incorporated sulfate indicated that the increase in proteoglycan synthesis observed in the posterior pole of deprived eyes occurs only in the cartilaginous scleral layer. The distribution of incorporated 35SO4, present over the cartilaginous layer of deprived sclera indicates that proteoglycan synthesis is lowest in scleral cartilage adjacent to the choroid and higher in interstitial regions of posterior cartilaginous sclera as well as in regions near the outer fibrous perichondrium. These results suggest that form-deprivation induced scleral growth in chicks can be attributed to growth and differentiation of scleral cartilage in the posterior pole.

Animals↗
PubMed2000

The effect of hydration and matrix composition on solute diffusion in rabbit sclera.

There is increasing interest in the possibility for drug delivery into the vitreous humor across the conjunctiva and sclera as an alternative route to the conjunctiva-cornea pathway. As a preliminary to human studies we have investigated the influence of scleral composition and hydration on solute transport in the rabbit sclera. Intermuscular sclera was excised from adult New Zealand rabbits. Tissue samples were either examined directly (controls), digested using chondroitinase ABC or crosslinked using glutaraldehyde. The effect of these treatments on the ultrastructural appearance of the sclera was assessed. Diffusion and partition coefficients for solutes of different molecular weights [sodium chloride (23 MW),(14)C sucrose (342 MW) and dextran-fluoresceins (3, 10, 40 and 70 kDa)] were measured in relation to tissue treatment. The results were used to determine the effect of tissue structure and composition on solute movement. We have found that: (1) diffusion and partition coefficients are sensitive to solute MW, decreasing as MW increases; (2) diffusion and partition coefficients are sensitive to tissue hydration, increasing as hydration increases; (3) crosslinking of the sclera by glutaraldehyde reduced the partition coefficients significantly for solutes with MW over 3 kDa; and (4) removal of glycosaminoglycans has only a small effect on either diffusion or the partition coefficient.

Animals↗
PubMed1979

Homograft sclera in tympanoplasty.

Homograft sclera was used as a supporting scaffold of the tympanic membrane and reinforcement for the fascia in 43 tympanoplasties. Fresh sclera donated for corneal transplantation to the eye bank in the ophthalmology department of the School of Medicine of Keio University was preserved in 70% alcohol after being stripped of uveal tissue. The sclera was cut as an interdigited method in grafting technique and the short process and the upper part of the manubrium of the malleus were exposed. The fascia was placed lateral to the sclera to cover the exposed mallus. Twenty-four cases have been observed for more than 6 months and ten cases for 3--6 months after surgery. Although the results of the long-term follow-up cannot be judged until after many years, there have been so far no recognizable complications, and it seems quite possible that this technique can reduce the complications as lateral healing and anterior blunting of the fascia alone. The postoperative closure rate of the tympanic membrane was 90% in all the cases except Type IV (two cases). The indications for the use of sclera were discussed.

Humans↗
PubMed1997

Human cornea and sclera studied by atomic force microscopy.

The purpose of this study was to investigate the ultrastructure of the extracellular matrix of human cornea and sclera by using the atomic force microscope (AFM). Specimens of human cornea (n=16) and sclera (n=10) were obtained from a cornea bank or from enucleated eyes (n=1; clinical and histopathological diagnosis: choroidal melanoma) and fixed in Karnovsky solution. The AFM resolved individual collagen fibrils in corneal and scleral tissue. Scleral collagen fibrils had a diameter ranging from 118.3 to 1268.0 nm and showed clear banding with a mean axial D-periodicity of 77.02 nm. The mean gap depth between the two overlaps was larger in the sclera than in the cornea. The diameter of corneal collagen fibrils ranged from 48.0 to 113.0 nm. In contrast to the sclera, the corneal collagen fibrils did not exhibit clear banding as their surface pattern. Closely attached fibrils with a beaded to globular structure were predominant in the cornea. The mean axial D-periodicity of the corneal collagen fibrils was 68.50 nm. In both tissues, the AFM resolved structures resembling cross-bridges between adjacent fibrils. The corneal collagen fibrils showed fibrillar properties that were different from those of the sclera, and that therefore might be essential for the spatial organization responsible for the optical quality of the cornea.

Cornea↗