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Results for “Limbus Corneae”

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At least 19 recordsLinked to original sources
PubMed1987

[Lymph drainage of the cornea, limbus and conjunctiva].

Air (n = 30), patent blue (n = 30), Berlin blue (n = 30), Berlin blue and air (n = 30), and Berlin blue and Mercox (n = 30) were injected into the corneas and conjunctivas of 150 enucleated cattle eyes. Using air for injection, so-called Bowman "corneal tubes" form in the cornea, which can easily be filled with pigment (patent blue, Berlin blue). In some cases (n = 3) the conjunctival lymphatics were filled with air during injection into the cornea. Besides the "corneal tubes", larger vessel-like structures can be demonstrated, which seem to be connected to corneal nerves. The significance of these structures as prelymphatics and their importance in the lymph drainage of the cornea are discussed. The injection of patent blue and Berlin blue into the limbus leads to the formation of a delicate network of arch-shaped lymphatics, from which larger lymphatics take their color. In the case of Berlin blue and Mercox, and Berlin blue and air injection, sections of lymphatic vessels in the shape of pointed arches form at the edges of the segments. It can be shown stereomicroscopically that these are not valves or invaginations, but only hump-shaped diverticula of the vessels. Annular constrictions of the lymphatic vessels were found, rather than bicuspid valves. The valveless pump mechanism described by Liebau is discussed as a possible means of lymph transport in the conjunctiva.

Animals↗
PubMed1990

Reticulohistiocytoma of the limbus and cornea. A clinicopathologic study of two cases.

Reticulohistiocytoma is a rare, benign histiocytic lesion usually occurring as an isolated skin nodule or as part of a systemic disorder known as "multicentric reticulohistiocytosis." The clinical and histopathologic findings of two women who presented with a single, painless mass localized to the cornea and limbus without skin lesions or systemic disease are reported. Histopathologically, the lesions were composed predominantly of large mononuclear and a few multinucleated cells with finely granular, "ground-glass" cytoplasm and large nuclei with prominent nucleoli. Immunohistochemical and electron microscopic studies conformed the histiocytic nature of these cells. Reticulohistiocytoma should be included in the differential diagnosis of epibulbar benign histiocytic lesions.

Adult↗
PubMed1986

Differential distribution of ATPase- and T6-positive cells (Langerhans cells) in the limbus and cornea of Hereford and non-Hereford cattle.

Epithelial sheets from the limbus, cornea, and third eyelid of Hereford and non-Hereford cattle were examined for the presence of Langerhans cells (LC) using the membrane enzyme ATPase as a marker for LC. The aim of the study was to test the hypothesis that differences in LC density exist between the various ocular epithelia of these animals producing depressed immune surveillance in the case of Hereford cattle. The presence of LC in ocular tissues was confirmed by parallel studies which detected epithelial cells bearing T6, an antigen expressed by human LC. Studies using serial sections demonstrated that T6+ cells also reacted with an anti-human HLA-DR monoclonal antibody. The detection of T6+, DR+ and ATPase+ cells in ocular epithelium in the absence of infiltrating macrophages suggested that LC are present in these tissues. While there were no significant differences in the density of T6+ cells between non-Hereford and Hereford cattle, in the latter ATPase+ cells were significantly fewer in the lateral, medial, and upper limbus.

Adenosine Triphosphatases↗
PubMed2000

Combined intraepithelial squamous neoplasia and atypical fibroxanthoma of the cornea and limbus.

PURPOSE: To investigate a case of an unusual neoplasm of the cornea and limbus. METHODS: A 59-year-old man presented with a highly vascularized, nodular mass involving the left cornea and limbus. An excisional biopsy and, subsequently, a superficial lamellar keratectomy and multiple conjunctival biopsies were performed. At the 6-month follow-up examination, repeat conjunctival biopsies were performed. RESULTS: Histopathologic examination of the corneal specimen showed a high-grade intraepithelial squamous neoplasia (in situ carcinoma) overlying an atypical fibroxanthoma. CONCLUSION: We report the clinical and histologic appearance of a corneal/limbal neoplasm consisting of an intraepithelial squamous neoplasia and an atypical fibroxanthoma.

Carcinoma in Situ↗
PubMed1993

In vitro growth and differentiation of rabbit bulbar, fornix, and palpebral conjunctival epithelia. Implications on conjunctival epithelial transdifferentiation and stem cells.

PURPOSE: The anterior surface of the eye is covered by several physically contiguous but histologically distinguishable epithelial overlying the cornea, limbus, bulbar conjunctiva, fornix conjunctiva, and palpebral conjunctiva. It is important to determine whether the different phenotypes of these epithelia are the result of intrinsic divergence, extrinsic modulation, or a combination of both. Based on keratin expression and cell kinetic criteria, the authors previously suggested that corneal epithelial stem cells may actually reside in the limbal basal layer. METHODS: In this article, the relationship between the corneal-limbal epithelial cells and conjunctival epithelial cells was analyzed by comparing their growth and differentiation properties in an identical cell culture environment. RESULTS: Using Dispase instead of trypsin to dissociate the cells, the authors were able to grow all five rabbit ocular surface epithelia in the presence of 3T3 feeder cells. They found that corneal and limbal cells synthesize identical keratins, including large amounts of the K3 and K12 markers of corneal-type differentiation. By contrast, all three conjunctival epithelia shared another keratin pattern, with large amounts of simple epithelial keratins but only minute amounts of K3/K12 keratins. CONCLUSIONS: This observation, coupled with previous findings that the "transdifferentiation" of conjunctival epithelial cells to corneal epithelium appears to be both incomplete and reversible, provides strong evidence that (1) the limbal-corneal epithelial cells form a lineage distinct from the conjunctival lineage and (2) conjunctival transdifferentiation actually represents a process of environmental modulation. In addition, of the three types of conjunctival epithelial cells, fornix cells were found to have a much greater proliferative potential than bulbar and palpebral cells. This observation, coupled with recent finding that fornix is enriched in slow-cycling (label-retaining) cells, raises the possibility that conjunctival epithelial stem cells may preferentially reside in the fornix.

Animals↗
PubMed1988

Topical application of all-trans-retinoic acid. A look at the cornea and limbus.

A 0.1% all-trans-retinoic acid in petroleum-base ointment was applied daily in eight normal rabbit eyes. Epithelial samples were collected from the cornea and limbus of six rabbits by impression cytology at 3- to 4-day intervals. Cytological changes were followed for 21 days and the eyes subsequently harvested for histochemical, scanning electron microscopic (SEM), and transmission electron microscopic (TEM) analysis of corneal and limbal structures. Two rabbits were treated with 0.1% all-trans-retinoic acid for 24 days without impression cytology until the 21st day. On the 24th day these eyes were harvested for similar studies. Impression cytology studies of the corneal epithelium demonstrated perinuclear halos and vacuolization of the cytoplasm. Additionally, vacuolization of the cytoplasm was observed by TEM, with attendant extrusion of the cytoplasmic contents and a subjective increase in surface microvilli as seen by SEM. Histochemical analysis revealed mucinlike staining of the corneal epithelium.

Administration, Topical↗
PubMed1984

Elastic and related fibres in the normal cornea and limbus of the domestic cat.

The presence of elastic and related fibres in the corneal and limbal tissue of the domestic cat is described. Various ages of animal from birth to maturity were studied by light and electron microscopy. Oxytalan fibres were present throughout the new-born kitten cornea. They were seen in greatest concentration both at the junction of the posterior limiting lamina with the inner substantia propria and beneath the peripheral anterior epithelium. With increasing maturity, oxytalan fibres disappeared from all but the most peripheral parts of the cornea where some of the, by now, thicker oxytalan fibres had matured into elaunin. All ages of animals studied showed an abrupt increase in fibre thickness and numbers at the corneal limbus. Oxytalan fibres predominated in the newborn kitten limbus but material from adult animals showed an increased proportion of elaunin fibres. Occasional elastic fibres were also seen in the more superficial region of the adult limbus. An overall decrease in elastic fibre types with increasing maturity was most obvious in the middle limbal layers.

Aging↗
PubMed1998

Circumcorneal annulus of collagen fibrils in the human limbus.

PURPOSE: To quantify the orientation of the collagen fibrils in the human limbus and to compare it with the orientation in the cornea and the sclera. METHODS: Fibril orientation was measured from 100 synchrotron x-ray diffraction patterns collected at intervals along lines across the cornea, limbus, and sclera. RESULTS: A distinct circumcorneal annulus of collagen fibrils was revealed in the limbus. For the individual cornea investigated, the annulus was not uniform around the corneal circumference; its width, fibril angular spread, and fibril density all varied with position. The average width of the annulus was narrower in the superior sector (1.5 mm) than in the inferior sector (2.0 mm). The results from the edge of the cornea suggested that the preferentially aligned corneal fibrils bend sharply at the limbus to run circumferentially or that, together with this bending or alone, extra fibrils arising in the sclera run across this zone. In the cornea the biaxial preferred directions became more pronounced from the center of the cornea toward the limbus along the superior-inferior axis. CONCLUSIONS: The excess of circumferential fibrils in the limbus, predicted from the sharp change of curvature in the surface of the eye at the limbus, appeared to take the form of a well-defined annulus. From a consideration of the mechanics of the system it seemed probable that the purpose of this annulus was to help maintain the correct curvature of the cornea. Before further research, it was hypothesized that some refractive problems associated with an incorrect curvature of the cornea may be related in part to abnormalities of this circumcorneal annulus.

Aged↗