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Biomedical subjects

W J Heriot

Publications and source records attributed to W J Heriot.

15 recordsLinked to original sources
PubMed2000

New approaches in the management of choroidal neovascular membrane in age-related macular degeneration.

Age-related macular degeneration (AMD) is a leading cause of blindness in the elderly population. The prevalence is reported to be 1.2-1.4% in several population-based epidemiological studies. Currently 25-30 million people worldwide are blind due to AMD. With the aging world population it is bound to increase significantly, and could become a significant public health problem in next two decades, with serious socio-economic implications. Several strategies are today available to treat the wet form of AMD, which is responsible for significant visual loss. These were until recently confined to laser photocoagulation, and subretinal surgery, but today two other modalities, namely, radiation and photodynamic therapy, are available. These treatment modalities however, are aimed at preservation of vision only, and not at reversing the process of the disease. Further research on antiangiogenic drugs and gene therapy could significantly help AMD patients.

Blindness↗
PubMed1998

Use of silicone oil in the treatment of complicated retinal detachment: results from 1981 to 1994.

PURPOSE: To evaluate the advantages and disadvantages of the retention and removal of silicone oil in the treatment of complicated retinal detachments. METHODS: The records of 344 patients (348 eyes) that underwent vitrectomy and silicone oil injection for complicated retinal detachments were abstracted and analysed. The anatomical and functional results, complications and influencing factors are discussed. The outcome in eyes after removal of the silicone oil was compared with the outcome in a comparable group of eyes in which the silicone oil was retained. RESULTS: The overall retinal reattachment rate was 63% (220/348). The final vision of 5/300 or better was 52% (115/220) in those eyes with totally attached retinas. The silicone oil-related complications included keratopathy (23%) and secondary glaucoma (11%). Comparing removal of silicone oil with retention of silicone oil, we found: (i) there was no statistical difference in the redetachment rate (19 vs 17%); (ii) oil-removed eyes had a better final vision (P < 0.05); and (ii) keratopathy (13 vs 23%), secondary glaucoma (11 vs 25%) and optic nerve atrophy (4 vs 18%) were significantly lower in oil-removed eyes. CONCLUSION: Silicone oil injection is useful in the treatment of complicated retinal detachments. For reducing the incidence of complications, early removal of silicone oil is recommended in those cases in which the retina is attached, all breaks adequately closed and traction relieved.

Adolescent↗
PubMed1995

Metastatic endophthalmitis in dialysis patients.

Metastatic bacterial endophthalmitis is a rare but devastating complication of septicaemia. We present 3 recent cases occurring in dialysis patients. Septicaemic dialysis patients seem particularly prone to staphylococcal endophthalmitis which developed in the face of therapeutic serum concentrations of appropriate antibiotics in all 3 cases. Prompt treatment, including consideration of intravitreal antibiotics, is required if vision is to be preserved. Early signs of endophthalmitis should be actively sought in septicaemic dialysis patients, as they are easily overlooked.

Adult↗
PubMed1993

Needle drainage of subretinal fluid. A randomized clinical trial.

Needle drainage of subretinal fluid with simultaneous observation using the indirect ophthalmoscope has been reported to have a very low complication rate. The technique was evaluated by a prospective clinical trial. The study group consisted of 100 patients undergoing scleral buckling for rhegmatogenous retinal detachment who were randomly assigned to groups treated with needle drainage or conventional two-stage drainage. At 1 month, the retina was anatomically flat in 88% of all cases. Subretinal hemorrhage occurred in 10 of 45 patients (22.2%) after needle drainage and in 7 of 55 patients (12.7%) after conventional drainage. The difference was not statistically significant. Retinal puncture occurred during conventional drainage in one case and in no cases during needle drainage. There were no cases of retinal incarceration. The results showed that subretinal hemorrhage was more common after needle drainage, but a larger study would be required to show whether this difference was statistically significant. The fear that the retina would be damaged by placement of a needle in the subretinal space throughout the drainage procedure was unfounded.

Aged↗
PubMed1992

Transmission electron microscopic study of a subretinal choroidal neovascular membrane due to age-related macular degeneration.

From a patient with age-related macular degeneration we studied ultrastructurally a disciform scar that was removed from an eye with a vitreous hemorrhage. In cross section, the scar was divided by a retinal pigment epithelial (RPE) cell layer. The choroidal side consisted of fibrovascular tissue with active neovascular buds and inflammatory cells, including macrophages attached to the RPE basement membrane. Apart from the RPE, no components of Bruch's membrane could be identified. The retinal side contained organizing hemorrhage and a collagenous matrix with fibroblastlike cells probably of RPE and choroidal origin. The anatomy and the clinical findings at surgery suggest that such scars lie on (rather than within) the inner collagenous layer of Bruch's membrane and contain two components divided by the original RPE layer. The choroidal side is fibrovascular, including active neovascularization, and the retinal side is fibrous and formed by metaplastic RPE cells and choroidal fibrovascular ingrowth.

Aged↗
PubMed1992

Pigment epithelial repair.

We studied the repair of large, surgically induced retinal pigment epithelial defects in rabbit eyes for up to 28 days. Ophthalmoscopically, the pigment epithelium surrounding the defect became less pigmented and scattered pale foci appeared. The margin remained distinct for 28 days and the defect was subsequently covered by a variable lacework of pigmentation. Angiographically, the acute defect was hyperfluorescent and leaked heavily, but within 7 days fluorescein leakage had ceased. Histology, transmission and scanning electron microscopy, and autoradiography for the study of cells in division revealed that the pigment epithelium surrounding the defect became pleomorphic after 1 day, began to proliferate within 3 days, and covered the defect within 7 days. Subsequently, many cells became pigmented and some were fibrocyte-like. The cells within the healing defect appeared to have derived from the pigment epithelium. Our findings suggest that similar processes occur in large human defects such as pigment epithelial rips.

Animals↗
PubMed1992

Treatment of subfoveal choroidal neovascular membranes with systemic interferon-alpha 2a.

Systemic interferon-alpha has recently been reported to be useful in the treatment of choroidal neovascular membranes (CNVM) in age-related macular degeneration. To further investigate its effect we treated eight patients with subfoveal choroidal neovascular membranes of various aetiologies including idiopathic, age-related macular degeneration and myopic chorioretinal degeneration. Only one of the eight patients responded with an angiographically demonstrated decrease in the size of the CNVM; this was in a patient from the idiopathic group. Considerable side-effects were reported with marked lethargy and malaise limiting compliance with some patients. Although this is an initial report with limited patient numbers and follow-up, it does suggest a role for interferon-alpha in patients with idiopathic neovascular membranes where the retina is otherwise normal, but raises some doubt as to its efficacy in the treatment of age-related macular degeneration.

Adult↗
PubMed1986

Ultrastructure of Bruch's membrane after krypton laser photocoagulation. II. Repair of Bruch's membrane and the role of macrophages.

The accompanying ultrastructural study showed that ophthalmoscopically white krypton laser photocoagulation in rats is followed by cellular invasion causing breakdown of Bruch's membrane (BM). We have expanded these observations, using scanning electron microscopy, transmission electron microscopy, and high-voltage transmission electron microscopy to describe the healing process. The repair of BM involves regenerating retinal pigment epithelial cells and choriocapillaris (CC) that form new basement membranes and fibroblasts that secrete collagen and elastin. The reformation of the CC is also associated with subretinal neovascularization. The involvement of macrophages was evident throughout the process of BM repair and formation of new vessels. We propose that the macrophages act as a common factor linking the diverse diseases associated with choroidal subretinal neovascularization, deduced from our evaluation of the healing process and the reformation of choriocapillaris.

Animals↗
PubMed1986

Cellular processes causing defects in Bruch's membrane following krypton laser photocoagulation.

Krypton laser photocoagulation of the posterior fundus of the rat created white retinal lesions comparable with therapeutic burns in the human. Twenty-four hours after injury, the retinal pigment epithelium was destroyed and the majority of the endothelial cells survived. The choriocapillary lumen was occluded. Bruch's membrane was not fractured nor had it undergone thermal lysis in any area studied but choriocapillary endothelial cell buds invaded the choroidal side of Bruch's membrane. After seven days, cellular protrusions arising from retinal pigment epithelial cells traversed Bruch's membrane through full-thickness defects and entered the choroid. Although intense laser burns may destroy Bruch's membrane, we conclude from this data that many so-called "breaks" in Bruch's membrane following laser therapy are formed by cellular processes and are not caused primarily by laser coagulation.

Animals↗
PubMed1986

Basal infolding density in the normal pigmented rat.

A variation in retinal pigment epithelial (RPE) basal infolding (BI) density in normal rats was observed and quantified. Serial electron micrographs of the midequatorial region of all quadrants from both eyes of litter-mate pigmented rats, 58 days old, were prepared. The lengths of BI and Bruch's membrane (BM) were determined by tracing enlarged micrographs to a Zeiss MOP-3 analyser. BI density per unit length of BM was assessed over the choriocapillary (CC) lumen, nucleated cytoplasma and intercapillary septum (ICS), and expressed as the dimensionless ratio BI/BM. Fenestrae were counted. The average BI/BM was 8.7; the BI/BM over the ICS, 6.1, was significantly lower than over the CC, 10.7 (P less than 0.001). BI/BM over the lumen and nucleated CC cytoplasm was the same. The number of fenestrae was not strongly associated with BI density (R2: 0.33). These data support the notion that the density of BI is related to diffusion within BM and is proportional to the distance from the CC lumen.

Animals↗
PubMed1985

Gas gangrene infection of the eyes and orbits.

The literature on Clostridium perfringens infections is reviewed up to 1983. An additional case is reported with bilateral clostridial infections of the eye and orbit. One eye followed the classical course of relentless panophthalmitis, amaurosis, and orbital cellulitis ending in enucleation. The second eye contained intracameral mud and gas bubbles that were removed by vitrectomy instrumentation. Subsequent removal of the toxic cataract resulted in a final aided visual acuity of 6/18, N8. This is the third report of a retained globe, and we believe the only known case where the patient was left with useful vision.

Adult↗
PubMed1984

Choroidal neovascularization can digest Bruch's membrane. A prior break is not essential.

A novel form of retinal phototoxicity has facilitated investigation of the effect of retinal pigment epithelial (RPE) damage on the choriocapillaris of the rat. In response to isolated RPE injury, the choriocapillaris buds, digests the endothelial basement membrane, and projects pseudopodia that erode Bruch's membrane. The development of subretinal neovascularization in one of the rats demonstrates that breaks in Bruch's membrane may result from this lytic process and that neither degeneration of Bruch's membrane nor a preexisting break is essential for subretinal neovascularization to occur.

Animals↗
PubMed1983

Ophthalmic findings among one thousand inhabitants of Rarotonga, Cook Islands.

A survey of 986 Polynesians was conducted in Rarotonga, Cook Islands, for the complications of diabetes. The ophthalmologists in the team made a general assessment of eye health. Trauma was a major cause of blindness. Diabetic retinopathy, trachoma, cataract and macular degeneration were not common findings. The initial criteria of nuclear cataract were pigmentation or opacification with loss of fetal suture detail. This was invalidated by the finding in young adults of enhanced pigmentation may augment the intrinsic filter of near ultraviolet light. Of the 118 people with chorioretinal scars, 25 shared features with cases reported from the Pacific region attributed to filariasis. The majority, however, were typical of toxoplasmosis. Cases of pseudoexfoliation were rare. This is surprising in view of the high prevalence reported among Australian Aborigines at a comparable latitude.

Adult↗
PubMed1983

Diabetic retinopathy in a natural population.

Most epidemiological studies of diabetic retinopathy have been based on clinic populations. This produces a bias for the more severe cases and later stages of the disease. To avoid this bias, 1567 Micronesian adults of Nauru (82% of total adult population) were examined. Diabetic retinopathy was classified by both the World Health Organization (WHO) criteria and the Airlie House reference photographs. Results were subject to multiple logistic regression model analysis. Diabetic retinopathy was present in 7% of the general population and in 24% of diabetics. Of the signs, microaneurysms and microhaemorrhages were the most important, being present alone in 19.5%; and in 68.1% when associated with exudates. Proliferative retinopathy was present in 4.5% of cases. Exudates alone were found in two cases (2.2%). Duration of diabetes was the strongest predictor variable and increasing two-hour plasma glucose levels significantly increased the risk of developing retinopathy.

Adult↗