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Biomedical subjects

H Barry Collin

Publications and source records attributed to H Barry Collin.

18 recordsLinked to original sources
PubMed2006

The corneal epithelial surface in the eyes of vertebrates: environmental and evolutionary influences on structure and function.

The smooth optical surface of the cornea is maintained by a tear film, which adheres to a variety of microprojections. These microprojections increase the cell surface area and are thought to improve the movement of oxygen, nutrients, and metabolic products across the outer cell membranes. However, little is known of these structural adaptations in vertebrates inhabiting different environments. This field emission scanning electron microscopic study examined the cell density and surface structure of corneal epithelial cells across 51 representative species of all vertebrate classes from a large range of habitats (aquatic, amphibious, terrestrial, and aerial). In particular, we wished to extend the range of vertebrates to include agnathans and some uniquely Australian species, such as the Australian lungfish (Neoceratodus forsteri), the Australian galah (Eolophus roseicapillus), the Australian koala (Phascolarctos cinereus), and the rat-tailed dunnart (Sminthopsis crassicaudata). Epithelial cell densities ranged from 28,860 +/- 9,214 cells mm(-2) in the flathead sole Hippoglossoides elassodon (a marine teleost) to 2,126 +/- 713 cells mm(-2) in the Australian koala (a terrestrial mammal), which may indicate a reduction in osmotic stress across the corneal surface. A similar reduction in cell density occurred from marine to estuarine to freshwater species. The structure and occurrence of microholes, microplicae, microridges, and microvilli are also described with respect to the demands placed on the cornea in different environments. All species that spend significant periods out of an aquatic environment possess microvilli and/or microplicae. These include all of our species of Mammalia, Aves, Reptilia, Amphibia, and even one species of Teleostei (Australian lungfish). Well-developed microridges occur only in teleosts in high osmolarity environments such as marine or estuarine habitats. Clear interspecific differences in corneal surface structure suggest a degree of adaptive plasticity, in addition to some phylogenetic trends.

Animals↗
PubMed2004

Primary cilia in vertebrate corneal endothelial cells.

The presence of primary cilia in corneal endothelial cells of a range of species from six non-mammalian vertebrate classes (Agnatha, Elasmobranchii, Amphibia, Teleostei, Reptilia and Aves) is examined by scanning and transmission electron microscopy. Our aim is to assess whether these non-motile cilia protruding into the anterior chamber of the eye are a consistent phylogenetic feature of the corneal endothelium and if a quantitative comparison of their morphology is able to shed any new light on their function. The length (0.42-3.80 microm) and width (0.12-0.44 microm) of the primary cilia varied but were closely allied with previous studies in mammals. However, interspecific differences such as the presence of a terminal swelling in the Teleostei and Amphibia suggest there are functional differences. Approximately one-third of the endothelial cells possess cilia but the extent of protrusion above the cell surface varies greatly, supporting a dynamic process of retraction and elongation. The absence of primary cilia in primitive vertebrates (Agnatha and Elasmobranchii) that possess other mechanisms to control corneal hydration suggests an osmoregulatory and/or chemosensory function.

Amphibians↗
PubMed2002

Morning glory syndrome.

Morning glory syndrome is a congenital optic disc anomaly in which much of the excavated colobomatous optic disc is filled with glial tissue. Ocular complications may include strabismus, reduced visual acuity and retinal detachment and it may have systemic associations as in Aicardi's syndrome. A patient with monocular morning glory syndrome and reduced visual acuity is reported. The pattern reversal visually evoked potential was reduced and the latency increased in the affected eye.

Child↗
PubMed2002

Microspherophakia.

Microspherophakia is present when the crystalline lens is small and relatively spherical with increased antero-posterior thickness. Clinical findings for a patient with idiopathic bilateral microspherophakia are described. The patient was moderately myopic with slightly reduced visual acuity. The anterior chambers (R: 1.57 and L: 1.37 mm) were shallow compared with normals (3.46 to 3.80 mm) and the crystalline lenses were thicker (R: 4.77 and L: 4.89 mm) than normal (3.3 to 3.96 mm) with steeper than normal anterior (radii of curvature R: 6.2 and L: 6.3 mm) and posterior (R: 6.3 and L: 5.6 mm) surfaces. Microspherophakia may be associated with various syndromes and there is a strong possibility of glaucoma, particularly if the small lens is displaced.

Anterior Chamber↗
PubMedDate not supplied

Editorial.

Explore the source record for details and available documents.

Editorial↗
PubMedDate not supplied

A comparative study of the corneal endothelium in vertebrates.

INTRODUCTION: In vertebrates, a corneal endothelium is essential for the maintenance of corneal transparency in a variety of environments, including aerial, terrestrial and aquatic. Knowledge of the surface structure of the corneal endothelium may assist our understanding of this unique tissue and its evolutionary development. Except for humans and some mammals, there have been few studies of other vertebrates, particularly the unique Australian species. METHODS: The field emission scanning electron microscope was used to study the corneal endothelium in representatives of four vertebrate classes: Teleostei (five species), Reptilia (two species), Aves (four species) and Mammalia (three species), including Marsupialia (two species). Endothelial cell densities were calculated from micrographs using computer-based image analysis. RESULTS: The cell densities varied considerably from 1,900 +/- 197 cells per mm(2) for the bream to 11,734 +/- 1,687 cells per mm(2) for the emu. Most of the corneal endothelia were similar to those reported for mammals. However, in some species such as the koala, the pattern was irregular. Some endothelial cells in birds possessed cilia. CONCLUSIONS: The shape of the corneal endothelial cells of vertebrates is typically a mixture of hexagonal and pentagonal cells, in which the cell borders are irregular and interdigitating. An exception is the koala, in which the cells were markedly irregular. Many of the cells have surface microvilli but only in the birds are cilia found in the centre of many endothelial cells. In spite of the range of corneal environments, there are no systematic differences in the cell densities of the various classes and species.

Journal Article↗
PubMedDate not supplied

Ocular injury due to bungee jumping.

BACKGROUND: Bungee jumping is a well-established recreational activity in New Zealand and Australia which may be associated with injuries to the eyes and other tissues. CASE HISTORY: A patient with a retinal haemorrhage which resulted from bungee jumping is reported and the clinical characteristics described. DISCUSSION: There have been several reports of injury due to bungee jumping. The types of ocular injury are reviewed and the aetiological theories discussed.

Journal Article↗
PubMedDate not supplied

Granular dystrophy of the cornea.

BACKGROUND: Granular corneal dystrophy is the commonest of the dystrophies and usually results in visual disability in the fourth or fifth decades. CASE HISTORY: A patient with granular corneal dystrophy is reported and the clinical characteristics described. DISCUSSION: The classical clinical features and the pathology and management of granular dystrophy are reviewed. Two unusual variations of the corneal dystrophy, namely, juvenile granular dystrophy and Avellino dystrophy, which is a concurrence of the features of granular and lattice dystrophies, are also described.

Journal Article↗
PubMedDate not supplied

Epiretinal membrane with macular pucker.

BACKGROUND: Epiretinal membranes are a common finding in people over the age of 50 years. Clinically, they usually cause minor visual distortion. However, in some patients, there may be a significant visual loss and/or metamorphopsia and surgery may be required in more severe cases. CASE HISTORY: In this report, we document the findings of a patient having an epiretinal membrane with macular pucker. The patient underwent surgery consisting of posterior vitrectomy and peeling away of the membrane. DISCUSSION: The classification and terminology commonly used to describe epiretinal membranes are reviewed. In addition, the aetiology, prevalence, symptoms, differential diagnosis, treatment and complications of epiretinal membranes are discussed.

Journal Article↗
PubMedDate not supplied

Pattern dystrophies of the retinal pigment epithelium.

We describe a family that shows autosomal dominant pattern dystrophy of the retinal pigment epithelium. There were 10 affected family members encompassing three generations. The various manifestations of these dystrophies, their inheritance characteristics, affects on vision function and their pathogenesis are discussed.

Journal Article↗
PubMedDate not supplied

Management of patients undergoing hydroxychloroquine (Plaquenil) therapy.

The quinolines, hydroxychloroquine (Plaquenil) and chloroquine are used primarily for their anti-inflammatory effects in the treatment of auto-immune conditions such as rheumatoid arthritis. Another common use of these drugs is the prophylaxis and suppression of malaria. The use of quinolines may cause several ocular side-effects. The most significant complication is irreversible macular damage resulting in both visual acuity and visual field loss. However, the Royal College of Ophthalmologists, UK (RCO) recently recommended against the monitoring of patients receiving quinoline therapy as it was deemed to be too costly, given the low incidence of retinal complications. In this article, we present a case of hydroxychloroquine retinopathy, describe the ocular changes associated with quinoline therapy and recommend an optometric review schedule for patients who are currently taking these drugs. Furthermore, we recommend a proactive approach toward medical practitioners prescribing these drugs for optometric-based monitoring of these patients.

Journal Article↗