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Results for “Sclera”

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At least 19 recordsLinked to original sources

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↗

PubMed1991

[Blue sclera in iron deficiency conditions].

The study involved 91 inpatients with anemia or/and blue sclera. Of them 66 proved iron-deficient: 59 with blue sclera against 7 without such. Twenty-three anemic patients free of iron-deficiency included 9 patients with blue sclera and 16 without them. Blue sclera were identified in 2 patients in the absence of anemia. Blue sclera as an indication of iron-deficiency has sensitivity of 89, specificity of 64 and accuracy of 82%. It is an additional sign in identification of anemia.

Anemia, Hypochromic↗

PubMed1979

Normal and staphylomatous sclera of high myopia. An electron microscopic study.

The posterior sclera of three normal eyes and five staphylomatous, myopic eyes was examined by electron microscopy. The following notable differences were found in myopic sclera: a predominantly lamellar, collagen fiber bundle arrangement; a reduction in the diameter of the fibrils; a greater dispersion for the range of fibril diameters; an increase in unusual star-shaped fibrils on cross section; and a greater prevalence of fibril groups with uniform but extremely fine diameters. These findings essentially agree with those in other studies of the myopic sclera. The ultramicroscopic changes encountered inpathologic myopia are judged to be compatible with an abnormal proteoglycan composition of the interfibrillary substance in the ectatic sclera.

Adult↗

PubMed1992

Devices for the control of laser transmission across the sclera during transscleral photocoagulation.

Improving the reproducibility of transscleral photocoagulation necessitates controlling the transmission of the laser beam through the sclera. Two factors make such control problematic: the locally increased transparency of the sclera resulting from the contact procedure and the occurrence of time-related relaxation phenomena. Two instruments have been devised to help control these factors. The first is a mechanical compensation unit comprised of magnets and a spring that allows the force exerted on the sclera to be adjusted to between 0.1 and 0.4 N, the pressure being determined by the outer diameter of the contact tip. The second instrument monitors the portion of the aiming beam reflected by the sclera as a means of determining the exact level of power actually transmitted through it. This information theoretically could be fed back to the treatment laser, allowing the level of power being delivered to be adjusted accordingly.

Ciliary Body↗

PubMed1991

Electron microscopic study of distribution of proteoglycans in bovine cornea and sclera.

To study differences in the distribution of proteoglycans and their relationships to collagen fibrils in the cornea and sclera, bovine cornea and sclera were examined histochemically using the ruthenium red (RR) staining method. RR-positive granules (30 nm in diameter) were present in association with fine filamentous materials (3 nm in diameter and 30-100 nm in length) in the interfascicular spaces of collagen bundles in both the corneal stroma and sclera. The amount of these materials was smaller in the sclera than in the cornea. The characteristic band-like arrangement of RR-positive granules connected by filamentous materials at intervals of 80-100 nm was found only in the cornea. In enzyme digestion experiments, tissue sections were treated by chondroitinase ABC, AC, and keratanase before RR staining. The RR-positive granules and their associated filamentous materials were darkly stained after chondroitinase AC or keratanase digestion, but displayed markedly lighter staining after chondroitinase ABC digestion. These results indicate that RR-positive granules and filamentous materials contain dermatan sulfate proteoglycan.

Actin Cytoskeleton↗

PubMedDate not supplied

Evaluation of sclera as a homograft in facial plastic and reconstructive surgery.

Augmentation of deficient soft tissue contours accounts for a large part of facial plastic and reconstructive surgery. An attempt to use homograft sclera in the feline animal model is presented. Augmentation of nasal dorsum and the chin contours was carried out in the cat model with preserved homograft sclera. Serial soft tissue radiographs and histologic study of the homografts demonstrated complete resorption of the grafts by six months. Further physical and chemical alterations of homograft sclera appear to be necessary prior to its implantation for the purpose of soft tissue augmentation.

Animals↗

PubMed1991

Quantitative study of collagen and elastin of the optic nerve head and sclera in human and experimental monkey glaucoma.

Quantitative studies of collagen density and fibril size distribution as well as elastin density were carried out in the optic nerve head and sclera of human and experimental monkey glaucoma eyes. The collagen fibrils of the normal lamina cribrosa are smaller and more uniform in size than those of the sclera. This feature may be an adaptation to maximize either elasticity or resistance to mechanical stress. In glaucomatous nerve heads, there is a major disruption of the structure of the lamina cribrosa beam structure, including a decrease in collagen density. The peripapillary sclera undergoes similar collagen density changes to those in the nerve head in human glaucoma eyes. Elastin fiber density is unchanged in the glaucomatous nerve heads that we studied.

Aged↗

PubMed1992

Ultrastructure of the extracellular matrix of bovine dura mater, optic nerve sheath and sclera.

The sclera, the outermost sheath of the optic nerve and the dura mater have been investigated histologically and ultrastructurally. Although these tissues appear very similar under the light microscope, being dense connective tissues mainly composed of collagen bundles and a limited amount of cells and elastic fibres, they exhibit subtle differences on electron microscopy. In the dura and sclera collagen appears in the form of large, nonuniform fibrils, similar to those commonly found in tendons, while in the optic nerve sheath the fibrils appear smaller and uniform, similar to those commonly observed in reticular tissues, vessel walls and skin. Freeze-fracture also reveals these fibrils to have different subfibrillar architectures, straight or helical, which correspond to 2 distinct forms of collagen fibril previously described (Raspanti et al. 1989). The other extracellular matrix components also vary with the particular collagen fibril structure. Despite their common embryological derivation, the dura mater, optic nerve sheath and sclera exhibit diversification of their extracellular matrix consistent with the mechanical loads to which these tissues are subjected. Our observations indicate that the outermost sheath of the optic nerve resembles the epineurium of peripheral nerves rather than the dura to which it is commonly likened.

Animals↗

PubMedDate not supplied

[Clinical and morphological aspects of the state of the sclera in various types of genetically determined corneal changes].

The authors analyze the results of a morphologic examination of 5 trephination scleral disks in various types of corneal curvature changes: with ectasia of the lower half of the cornea (1), with uneven corneal ectasia (1), with true keratoconus (2), and with keratoglobus (1), and come to a conclusion that involvement of the scleral connective tissue presenting as extracellular dysproteinosis is the morphologic substrate of deterioration of the elastic properties of the sclera, clinically observed in patients with various genetic corneal ectasias. Involvement of the sclera in the dystrophic process indicates a general involvement of the total external capsule of the eye in genetically determined corneal ectasias. The least marked changes presenting as fragmentation and fiber degeneration of collagen bundles are seen in uneven corneal ectasia. More profound changes in the sclera and its homogenization were detected in the patients with true keratoconus, ectasia of the lower half of the cornea, and keratoglobus.

Cornea↗

PubMed1991

Biochemical changes in rabbit sclera following destruction of pigment epithelium.

The long-term effect of destruction of the pigment epithelium by sodium iodate on the biochemistry of rabbit sclera was studied in one group with intravenous injection of sodium iodate, and in a second group with injection of sodium iodate into the right eye. Intravenous treatment produced a non-significant increase in the uronic acid concentration. In the second group the untreated fellow eye was microscopically intact, but was shown (as the treated eye) to alter the concentration of uronic acid in different parts of the sclera. All eyes from treated animals exhibited changes in the relative content of the various glycosaminoglycans and in the content of hydroxyproline, hydroxylysine and proline. This work indicates that the pigment epithelium may play a key role in the control mechanism of the scleral connective tissue, and this again has major implications in terms of a possible medical treatment of axial myopia.

Amino Acids↗

PubMed1979

Scleral pockets and lyophilized sclera in retinal detachments.

For our buckling operations in retinal detachment, we prefer lyophilized sclera because it is well tolerated without tissue reaction, and very easy to handle. Its inertness is demonstrated by histopathological examination of sclera fragments taken during reoperations.

Freeze Drying↗

PubMed1992

A new instrument for controlling pressure exerted on the sclera during contact Nd:YAG laser cyclodestruction.

We tested the device described by Rol et al in their article in this issue, designed to define and precisely control the pressure applied to the sclera during contact cyclodestruction with a cw-Nd:YAG laser. Since scleral transparency, and hence transmission of laser energy, depends on the pressure applied, control of this parameter represents an important advance toward the goal of standardizing the cyclodestructive procedure. In eight of nine cadaver pig eyes, pressure was exerted on the sclera using the pressure-controlling device, with a setting of 0.25 N for two of these eyes, and one of 0.4 N for the other six. In the remaining eye, pressure was controlled intuitively by an experienced surgeon. Applying forces of 0.25 or 0.4 N yielded similar success rates, although these fluctuated greatly even under constant pressure conditions (from 17% to 50% at 0.25 N; from 27% to 42% at 0.4 N). The highest success rate (55%) was achieved by the intuitively controlled pressure irradiations of the experienced surgeon. The variation in coagulation intensity that occurred despite constant pressure suggests that additional factors contribute to the results achieved. Nonetheless, this pressure-controlling probe represents an important achievement. It will permit not only the novice but even experienced operators to adhere unambiguously to a protocol of quantitative, reproducible parameters, and will also help researchers to better understand the relationship between energy delivered and intraocular pressure reduction achieved in contact cyclophotocoagulation.

Animals↗

PubMed1977

Experience with donor sclera for extruding orbital implants.

Accumulated clinical evidence has confirmed the suitability of eye bank sclera as a structural and reconstructive material for lid and orbital surgery. Since 1970 we have been using fresh donor sclera. In our series of sixty-four cases, seventeen were for extruding or extruded orbital implants. Of these seventeen only two had any sort of complication, and these were easily corrected. This technique has permitted a successful prosthetic fitting within six weeks following surgery, with good cosmesis in all cases.

Child↗

PubMed1976

Cellular blue nevus of the sclera.

An isolated cellular blue nevus of the sclera was discovered and removed during a retinal detachment operation. Such benign tumors may be misdiagnosed clinically as an extension of a melanoma of the choroid or histologically as melanoma.

Choroid Neoplasms↗

PubMed1991

Optical properties of human sclera, and their consequences for transscleral laser applications.

The spectral dependence of the optical properties of human sclera adjacent to the limbus was investigated and related to the potentials of transscleral photocoagulation. The total transmission, absorption, and reflection, as well as the angular distribution of the transmitted and reflected light were measured at five laser wavelengths (442 nm, 514 nm, 633 nm, 804 nm, and 1,064 nm), both for noncontact and contact applications. Absorption and scattering coefficients were determined using the Kubelka-Munk model for light propagation through a scattering tissue. The scleral transmission is only 6% at 442 nm but increases to 35% at 804 nm and to 53% at 1,064 nm. The absorption is high at short wavelengths with 40% at 442 nm but it is only 6% at 804 nm and 1,064 nm. The reflection is generally higher than 40% and shows little wavelength dependence. The transmitted light is scattered diffusely at short wavelengths, but at 804 nm and 1,064 nm it exhibits a fairly narrow angular distribution in forward direction. Fiber contact leads to an increase of transmission, with a factor of 3.5 at 442 nm, of 2.0 at 804 nm, and 1.5 at 1,064 nm. Our results indicate that the diode laser (804 nm) and the Nd:YAG laser (1,064 nm) with contact delivery are best suited for transscleral photocoagulation.

Absorption↗

PubMed1978

[Laser lesions of the anterior segment of the rabbit eye. Studies of cornea, iris, lens and sclera using an argon, ruby and YAG-laser].

The anterior segment of the eye of 100 rabbits was exposed to radiation from Argon, Ruby and YAG lasers. The healing process of liminal and supraliminal lesions was evaluated histologically. The iris is the most sensitive tissue for all three lasers (threshold radiant exposure, Argon: 0.004 kJ/cm2, Ruby: 0.01 kJ/cm2, YAG: 0.05 kJ/cm2). Higher energies necessary for lesions in the transparent media were available only with the Argon and YAG lasers. The Argon laser failed to produce lesions in the lens, and threshold radiant exposure for the central cornea was 8 kJ/cm2. The thresholds for YAG lasers lesions in the central cornea and lens were of the same magnitude. The marked absorption of energy by the iris may lead to an accumulation of heat, resulting in lesions of adjacent tissues or a reduction of threshold for those lesions: The threshold in the peripheral cornea was ten times lower than in the center with the Argon laser, four times lower for the YAG laser. The thresholds for Argon and YAG laser lesions in the peripheral sclera lay between the thresholds for the iris and for the peripheral cornea. A safety standard for the anterior segment of the eye should be based on the lowest threshold (Argon laser lesion of the iris). The application of a factor 100 results in a maximal permissible exposure of 40 mJ/cm2. The influence of the beam diameter could not be evaluated.

Animals↗

PubMed1977

[Syndrome of blue sclerae and keratoglobus (ocular type of Ehlers-Danlos syndrome (author's transl)].

Two children born on Crete of consanguinous parents presented the following manifestations of the ocular type of Ehlers-Danlos syndrome (EDS): blue sclerae, keratoglobus and rupture of cornea following minor trauma. In cultivated fibroblasts of one of the patients there was no evidence of defective lysine hydroxylation. The possible relation of our case to a recent similar report by Judisch et al. (1976) is discussed. The ocular type of EDS may be genetically heterogenous. Provisionally, we propose for cases with normal lysyl hydroxylation in vitro the term 'type VIII of EDS'.

Child↗

PubMed1977

Keratoglobus and blue sclera.

Five patients from two families had similar features including keratoglobus, blue scleras, hyperextensibility of the hand, wrist, and ankle joints, sensorineural conduction hearing alterations, and mottling of the teeth. Keratoglobus had been observed in all patients at, or shortly after, birth. Corneal perforations developed in seven of the ten eyes after minimal trauma. Repair of these perforations was complicated by the extremely thin corneas and six eyes had to be either enucleated or eviscerated. Histopathological examination of two of the enucleated eyes showed the corneal stromas of both eyes to be estremely thin, Bowman's membrane was absent, and Descemet's membrane was unusually thick. This condition has an autosomal-recessive inheritance pattern.

Adolescent↗