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Results for “Descemet Membrane”

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At least 19 recordsLinked to original sources
PubMed1979

A new technique for isolation of Descemet's membrane: preliminary studies.

The structure and function of basement membranes have been the subject of extensive investigation. The present study takes advantages of a new experimental procedure to yield ultrastructurally pure basement membranes and applies this methodology to Descemet's membrane, a highly specialized ocular basement membrane. Rabbit Descemet's membranes and associated endothelial cells were mechanically isolated without contaminating stromal elements. The endothelial cells were then solubilized and removed by treatment with detergents as verified by light microscopy and scanning and transmission electron microscopy. The Descemet's membrane remained intact and retained its fibrillar fine structure. Therefore purity of starting material for ongoing morphological and biochemical studies of isolated Descemet's membranes is demonstrated. These investigations will provide a valuable data base for comparison with disease-altered Descemet's membranes.

Animals↗
PubMed1978

[Functional morphology of the cornea].

The corneal epithelium serves as a barrier between tear film and stroma and maintains a smooth corneal surface. The optical features of the cornea, namely refraction and transparence, depend largely upon the characteristics of the superficial corneal layers. Any lesion of this superficial cell coat facilitates the penetration of particles of even small diameter (virus, bacteria) towards the stroma. In fact, viral corneal diseases usually start in the epithelium, the virus being replicated in transformed epithelial cells. Corneal wounds are rapidly covered by migrating epithelial cells, invading the lesion from the border of the epithelial defect. Cohesion between epithelium and underlying stroma remains very weak unless regenerating epithelial cells have synthesized a basement membrane, allowing thus a firm attachment between epithelial hemidesmosomes and basement membrane. Recurrent erosions occur readily in the absence of epithelial basement membranes. Presumably, corneal epithelium is involved in the biosynthesis of fibrillar collagen of the superficial stromal layers. Corneal wound healing is delayed by a pathological epithelium. Corneal hydratation is controlled by the endothelium. It maintains a bulk flow of water towards the aqueous humor side against a pressure gradient and regulates the movement of metabolites. In the case of endothelial malfunction, the corneal stroma thickens due to a swelling of mucopolysaccharides. The endothelium synthesizes a very thick basement membrane (Descemet's membrane). In penetrating corneal wounds, Descemet's membrane is synthesized by the endothelium.

Animals↗
PubMed1979

[Histochemical studies on the structure and the age changes of Descemet's membrane in cattle (author's transl)].

Descemet's membrane of 15 cattle-corneas, aged 6 month to 13 years was studied by various histochemical and morphometric methods. 3 zones could be differentiated. Zone 1 is relatively small and does not show significant changes with age; zone 2 comprises the main part of Descemet's membrane, its diameter increased with age. Zone 2 is rich in sulfated glycosaminoglycans. Zone 3, below the endothelial lining, does not develop before the 3rd and 5th year of life and stains different from zone 2.

Aging↗
PubMed1978

The distribution of disulfide-groups in Descemet's membrane, lens capsule, and zonular fibers.

Zonular fibers contain large quantities of disulfide-groups which histochemically can be demonstrated after thiosulfation or reduction with sodium thioglycollate. Zonular fibers share these staining behaviours with oxytalan fibers and elastic fiber microfibrils. Smaller amounts of disulfide-groups can be demonstrated when visualized by means of the thioglycollate/ferric-ferricyanide method. Diffusion of acidic staining solutions seems to be limited in Descemet's membrane and in the lens capsule: only surfaces of these membranes become reactive after thiosulfation. It is assumed that the distribution of disulfide-groups in Descemet's membrane and in the lens capsule shows the distribution of type IV collagen.

Animals↗
PubMed1977

Thermokeratoplasty in the treatment of persistent corneal hydrops.

Thermokeratoplasty (TKP) was used to treat six cases of chronic corneal hydrops previously refractory to traditional therapy. In all instances TKP resulted in a clearing of the hydrops within three weeks. In four cases the resultnat comfort and clarity precluded the necessity for transplantation, while in the remaining two cases subsequent penetrating keratoplasty was successfully performed. Thermokeratoplasty is advocated in chronic hydrops refractive to standard therapy, in acute hydrops to accelerate recovery, in recurrent hydrops to assist in healing of breaks in Descemet membrane, thus preventing recurrences, in cases with extensive hydrops to deturgesce the peripheral cornea prior to transplantation, and as definitive therapy in cases where transplantation is contraindicated.

Acute Disease↗
PubMed1977

Lipid keratopathy following corneal hydrops.

A case of lipid keratopathy occurred following acute rupture of Descemet membrane. The cause of the hydrops remained undetermined. There was no history of any prior corneal inflammation or vascularization in the initially involved eye. Lipid deposition was observed following resolution of the corneal edema, and its course was followed for the next several months. Histopathologic studies of the specimen showed lipid deposits in the posterior and middle corneal stroma and degenerative changes in the corneal lamellae and Bruch membrane. Laboratory examination disclosed a type IV hyperlipemia, with normal serum cholesterol levels and elevation of pre-beta-lipoproteins and triglycerides. It cannot be determined from our study if this condition was a causative factor.

Adult↗
PubMed1978

Endothelial cell population changes of human cornea during life.

A photo slit lamp was used to obtain color, specular reflex, high magnification photographs of the corneal endothelium of subjects ranging in age from 3 to 88 years. Multiple areas of the cornea were examined to determine the endothelial cell population. No appreciable difference in cell density was found between the right and left eyes of the subjects nor between male and female subjects of similar age. Apparent defects in the endothelial cell coverage of Descemets membrane were found in subjects as young as 20 years of age and with increased frequency in older age groups. These defects were at times associated with variations in endothelial cell populations between the central and peripheral cornea. The average corneal cell population fell from nearly 1 million cells in the first years of life to about one third that number by the eight decade of life.

Adolescent↗
PubMed1976

Chalcosis in the human eye. A clinicopathologic study.

A clinicopathologic study of eight human eyes containing intraocular copper foreign bodies was undertaken. These foreign bodies, which had been retained in the eyes from three weeks to 22 years, were analyzed by atomic-absorption spectrophotometry and x-ray diffraction to determine their chemical composition. Copper deposits in Descemet membrane, vitreous, internal limiting membrane of the retina, and fibrous capsule around the foreign bodies could be demonstrated by rhodanine, rubeanic acid, and alizarin blue stains and were correlated with clinical findings and pathologic changes. Eyes with foreign bodies containing more than 85% copper tended to show more disseminated copper deposits. Eyes with alloy containing less than 85% copper showed more localized deposits of copper. Retinal structures were well preserved, even in an eye with an intraocular copper foreign body that had been retained for 22 years.

Adolescent↗
PubMed1979

[Experimental alpha-chymotrypsin model of glaucoma in the rabbit: histopathological studies (author's transl)].

The injection of alpha-chymotrypsin into the posterior chamber of the eye is known to produce an experimental ocular hypertension of long duration in animals. The present study reports the pathological changes which occur in the eye during the first nine months after the ocular injection of alpha-chymotrypsin in rabbits. Six weeks after treatment most of the eyes showed a buphthalmia and an intraocular pressure elevation which varied greatly from animal to animal. The anterior chamber angle of the treated eyes showed a progressive enlargement. Several days after the enzyme injection a transient increase in thickness of the cornea and Descemet membrane was noted. Cupping of the optic disc, characterized by a total disappearance of the optic nerve head fibers and an excavation beginning at margins of the retina appeared after four months and in most cases were present seven months after the treatment. More or less prominent retinal degeneration was also evidenced three months after enzyme injection. The results indicate alpha-chymotrypsin-induced occular hypertension in the rabbit leads after several months to pathological change in the eye analogous to that observed in human glaucoma.

Animals↗
PubMed2025

Peripheral Macular Endothelial Dystrophy: Clinical, Histopathologic, Genetic and Functional Characterization.

OBJECTIVE: To report a CHST6-associated corneal endothelial dystrophy. DESIGN: Prospective observational case series. PARTICIPANTS: Thirty-five individuals from seven families, including 13 affected individuals exhibiting corneal epithelial and stromal edema, peripheral posterior corneal macular opacities, and endothelial guttae, as well as 22 unaffected family members. METHODS: Whole-exome sequencing was performed in 3 families and Sanger sequencing of CHST6 was performed in all individuals. Histological examination of Descemet membrane (DM) excised at the time of endothelial keratoplasty was performed for three probands. Serum keratan sulfate (KS) levels were measured in members of six families. Functional analysis of identified mutations was performed using CHST6 promoter containing CHST6 expression vector in human keratocytes (HK) and corneal endothelial cells (HCEnC). MAIN OUTCOME MEASURES: Clinical phenotype; genetic analysis; functional analysis of identified CHST6 mutations; serum KS levels; histologic examinations of DM. RESULTS: All affected individuals demonstrated peripheral macular opacities at the level of DM. Visually significant corneal edema in affected individuals was successfully managed by endothelial keratoplasty. Genetic analysis demonstrated a rare CHST6 promoter mutation (c.-690G>C) in the homozygous state in affected individuals from three families and in the compound heterozygous state with a CHST6 coding mutation (p.R211Q, p.Y268C or p.P280L) in affected individuals from the other four families. In silico analysis predicted c.-690G>C to be a regulatory variant, located at the RNA polymerase II binding site. Functional analysis in vitro demonstrated that c.-690G>C leads to increased KS sulfation in the corneal endothelium and DM, with no change of KS sulfation in keratocytes. Histologic examination of DM from affected individuals revealed elevated levels of sulfated and non-sulfated KS in DM and endothelium, consistent with the functional analysis. Minimum changes in serum sulfated KS levels were observed in affected individuals. CONCLUSIONS: We suggest the name Peripheral macular endothelial dystrophy (PMED) to describe this dystrophy that is characterized by peripheral posterior corneal macular opacities and endothelial dysfunction without stromal haze or opacities. Given that both PMED and macular corneal dystrophy are associated with promoter and coding region mutations in CHST6, we propose that they be categorized as CHST6-associated corneal dystrophies.

Humans↗
PubMed1979

The ultrastructural features of laser trabeculopuncture and cyclodialysis. Problems related to successful treatment of chronic simple glaucoma.

Microexplosions induced by a Q-switched Nd:glass laser working above optical breakdown power density levels are able to destroy the inner wall of Schlemm's canal and to tear open both the supraciliary and suprachoroidal space. Furthermore, the ciliary muscles bundles may be disrupted, becoming subsequently permeable to the aqueous and thus also acting as a new outflow route. However, whereas breaks of the inner wall of Schlemm's canals are sealed in the monkey by the activity of endothelial cells forming a new Descemet membrane over the impact site, the supraciliary and suprachoroidal spaces remain open over an observation period of up to 480 days. Perfusion experiments with a HgS tracer substance have shown that these newly created, potential outflow routes may be considered as real additional filtration areas.

Animals↗
PubMed1978

[Corneal covering of cornea in ulcerative keratitis: clinical and histological observations (author's transl)].

Clinical and histological findings are demonstrated in 4 cases with ulcerative keratitis treated by covering with full-thickness cornea. In only two cases the initial keratitis healed with scarring and a keratoplasty could be performed. The donor cornea is resorbed very slowly, remnants of Descemet-membrane of the graft are seen even after 20 months. Immunological reactions could not be observed.

Aged↗
PubMedDate not supplied

Further studies on the ridge at the internal edge of the cataract incision.

A pathologic and experimental study of the etiology and morphology of the ridge, visible gonioscopically in the region of the internal lips of the cataract incision during and after the cataract operation, is described. The ridge observed clinically cannot be reproduced in human eye-banks eyes but can be reproduced in vivo in the eye of the owl monkey. Histopathology and ultramicroscopic studies of these experimental eyes, together with evidence derived from histopathologic slides of postmortem human eyes, suggest that the ridge is probably the result of immediate edematous swelling of the deeper layers of the corneal stroma after the incision transects corneal endothelium and the Descemet membrane. While internal wound lip malapposition may be a contributing factor to formation of the ridge, it is probably not an essential component. The ridge is not caused by the incision-closing sutures for it is already present prior to suturing of the wound. The role in ridge formation of mechanical stress alterations produced immediately by the incision is considered but is not known.

Animals↗
PubMed1978

Chandler's syndrome as a variant of essential iris atrophy. A clinicopathologic study.

Trabeculectomy and peripheral iridectomy specimens from one male and two female patients with Chandler's syndrome (age, 30 to 42 years) showed that all had unilateral corneal endothelial "dystrophy," corneal edema, mild to moderate iris atrophy without holes, peripheral anterior synechiae, and glaucoma. In one, fluorescein angiography of the iris disclosed a sector filling delay of limbal and conjunctival vessels and pupillary and extrapupillary leakage. Histopathologic examination showed a layer of degenerated corneal endothelium and Descemet's membrane extending across the inner uveal trabeculum. Descemet's membrane displayed irregular, nodular, scroll-like excrescences in some cases, and thinner placoid configurations with abnormal widely spaced collagen (100 nm) in others. Corneal endothelial cells exhibited increased microvilli, widened cellular interdigitations, and occasional shrunken cells with enlarged or disrupted cytoplasmic blebs. Peripheral iris specimens displayed mild to moderate stromal atrophy without vascular occlusions. Pigment epithelium was normal.

Adult↗