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Biomedical subjects

J S Lean

Publications and source records attributed to J S Lean.

34 records · Page 2Linked to original sources
PubMed1986

Aqueous concentrations of fluorouracil after intravitreal injection. Normal, vitrectomized, and silicone-filled eyes.

Treatment of postoperative vitreoretinopathy with combined intravitreal fluorouracil and liquid silicone may result in increased corneal and retinal toxicity. We therefore investigated the movement of carbon 14-labeled fluorouracil from the vitreous into the anterior chamber in normal rabbit eyes and in eyes filled with either balanced salt solution or silicone after vitrectomy and lensectomy, with or without preservation of the anterior capsule. Only 0.56% of intravitreally injected fluorouracil was recovered from the anterior chamber over a four-hour period in normal eyes. This impermeability was partly maintained if the anterior capsule was retained (9.98%), particularly if the eye contained silicone (2.52%). The greatest amount was recovered when both lens capsules were removed (43.7%). Corneal toxicity is most likely to occur in this situation.

Animals↗
PubMed1986

Relative permeability of retina and retinal pigment epithelium to the diffusion of tritiated water from vitreous to choroid.

The movement of intravitreally injected tritiated water from the vitreous to the choroid was accelerated by the removal of intervening retina. Both rate of transfer and peak choroidal levels of the tracer were increased, but the proportion of the intravitreal dose recovered was unaltered. In contrast, the movement of tritiated water after diffuse damage to the retinal pigment epithelium by sodium iodate was similar to that of control eyes. The main resistance to the diffusion of this tracer from the vitreous to the choroid is the retina. The differential permeability of the retina and the retinal pigment epithelium may have a role in normal retinal adhesion.

Animals↗
PubMed1984

Intravitreal expanding gas bubble. A morphologic study in the rabbit eye.

The morphologic changes induced by an expanding bubble of perfluoropropane (C3F8) gas in the vitreous body have been studied in the rabbit eye by dissecting microscopy and scanning and transmission electron microscopy. Initial expansion of the gas displaces water from the vitreous; the remaining vitreous forms a compressed layer on the retinal surface. Subsequent absorption and contraction of the gas bubble is associated with gradual detachment of the compressed vitreous from the retina. Eventually, vitreous detachment is complete, except for residual attachments posteriorly to the medullary rays and anteriorly to the ciliary processes. The plane of vitreous separation is predominantly at the anatomic vitreoretinal junction, although scattered islands of outer cortical vitreous are found on the surface of the retina.

Animals↗
PubMed1984

Unexpected traction retinal detachment: a complication of an animal model of pars plana vitrectomy.

We evaluated a rabbit model of the vitrectomized eye. In 16% of eyes the surgical procedure leads to the development of traction detachment of the vascularized portion of the retina (medullary ray). The traction originates in the vitreous base and is probably transmitted to the posterior retina via a sheet of detached vitreous cortex. In time course and morphology this differs from the experimental traction detachment seen after the injection of cells. Provided this complication is recognized, the vitrectomized rabbit eye is a useful and economic model for experimental studies.

Animals↗
PubMed1984

Experimental model of proliferative vitreoretinopathy (PVR) in the vitrectomised eye: effect of silicone oil.

Silicone oil alone or as an adjunct to vitrectomy is widely used for the treatment of retinal detachment complicated by proliferative vitreoretinopathy (PVR). It appears to reduce the tendency for recurrent traction detachment, but the mechanism of this action is obscure. We have studied the effects of silicone oil in an experimental animal model. Twenty five thousand homologous fibroblasts were injected into the aphakic vitrectomised rabbit eye, and traction detachment of the vascularised retina (medullary rays) regularly resulted. Intraocular silicone oil did not influence the development of this experimental detachment.

Animals↗
PubMed1984

Vitrectomy and fluid/silicone-oil exchange for giant retinal tears: results at six months.

The results of vitrectomy combined with fluid/silicone-oil exchange in 73 eyes with giant retinal tears are reported at six months after surgery. Initial anatomical success was achieved in 71 out of 73 eyes (97%) and, prior to removal of silicone-oil, in 66 out of 73 eyes (90%). In 63 eyes (86%) the retina remained attached six months after surgery. Of these visual acuity was 6/60 or better in 44 (70%). The high proportion of eyes with macular detachment before surgery and the frequency of macular abnormalities are thought to account for reduced vision in many of the anatomically successful cases.

Adolescent↗
PubMed1983

Retinal membrane in the vitrectomized eye: an animal model.

A fibroblast induced model of retinal membrane has been developed in the vitrectomized rabbit eye. Localization of the membrane on the retinal surface requires a two stage procedure. An initial lensectomy and vitrectomy results in partial posterior vitreous detachment; the vitreous remains attached to the vascular retina (medullary rays) and vitreous base. At a subsequent procedure the detached posterior hyaloid face is excised; a fluid/SF6-air exchange is performed and fibroblasts are injected. Despite the use of only 25,000 cells, retinal membrane and subsequent traction retinal detachment develop. In contrast to cell injection in the nonvitrectomized eye, in which vitreous membranes predominate, this model stresses epiretinal membrane and surface retinal traction.

Animals↗
PubMed1982

Management of complex retinal detachments by vitrectomy and fluid/silicone exchange.

The combined procedure of pars plana vitrectomy and liquid silicone exchange has been developed for the management of complex retinal detachment. Complete re-attachment was achieved in 88 per cent of eyes with giant retinal breaks and visual improvement occurred in 71 per cent. Macular re-attachment was obtained in 68 per cent of eyes with massive periretinal proliferation (MPP) and visual improvement occurred in 53 per cent. In contrast, in thirteen cases of severe diabetic traction detachment, only four remained attached with visual improvement in one. In seven eyes with severe perforating trauma and retinal detachment, retinal re-attachment was achieved in four and visual improvement in three. We conclude that this technique is indicated in giant retinal breaks, is encouraging in MPP, has a very limited role in the management of diabetic traction detachment, and requires further evaluation in the management of traumatic detachment.

Diabetic Retinopathy↗
PubMed1981

Management of giant retinal tears using vitrectomy and silicone oil/fluid exchange. A preliminary report.

The long-term management of giant retinal breaks presents a difficult problem. A surgical method is described in which removal of the vitreous and complete filling of the preretinal space with silicone oil is used to close the giant tear and re-attach the retina. The silicone oil is removed from the eye after 2 to 3 months in most cases. The results are reported of using this technique in a consecutive series of seventeen eyes with giant retinal breaks.

Adolescent↗
PubMed1980

Effect of preoperative posture and binocular occlusion on retinal detachment.

In an unselected series of retinal detachments a 24-hour period of binocular occlusion and posture with a retinal hole dependent produces some resolution of subretinal fluid in 13% of cases. If only patients with acute, freely mobile detachments and retinal holes above the horizontal meridian were selected the proportion of detachments showing some resolution rose to 30%. In 8% of cases a paradoxical response occurred, the detachment increasing in depth or extending to involve an additional area of retina.

Eye Movements↗
PubMed1980

The Sylvian aqueduct syndrome and neurofibromatosis.

A 23-year-old man initially presented with the Sylvian aqueduct syndrome and subsequently developed cutaneous neurofibromata. The case is reported and the possibility that these represent manifestations of the same genetic abnormality is discussed.

Adult↗
PubMed1980

The acute vitreous haemorrhage.

One hundred cases of acute vitreous haemorrhage have been analysed prospectively. It was possible to identify the cause of the haemorrhage at presentation in 79% of the cases. 40% were due to retinal tears and only 6% were associated with diabetic retinopathy.

Acute Disease↗
PubMed1977

Infection following retinal detachment surgery.

Since the introduction of gentamicin (given both as a soaked sponge and as an injection below Tenon's capsule at the end of surgery) no case of early infection either with or without intraocular signs after operation for retinal detachment has occurred in a series of 206 cases comprising 243 operations. However, late infection many months after operation has appeared in 3 cases (1-5%), though this rate appears to have been favourably influenced by the administration of gentamicin. Local or systemic side effects from the administration of gentamicin have not been seen, and therefore the sub-Tenon injection in the quadrant where the sponge has been placed is strongly advocated in all cases of surgery for retinal detachment when such sponges are used.

Gentamicins↗