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Biomedical subjects

R Machemer

Publications and source records attributed to R Machemer.

At least 163 records · Page 9Linked to original sources
PubMed1977

Ultrasonographic diagnosis of massive periretinal proliferation in eyes with opaque media (triangular retinal detachment).

A triangular pattern of retinal detachment, as seen by B-scan ultrasonography in eyes with opaque media has been correlated with advanced massive periretinal proliferation (MPP). The ultrasonographic triangular configuration was created by a proliferative membrane that united detached retina anteriorly. Thirteen eyes with opaque media and a triangular retinal detachment by ultrasound had severe MPP at vitrectomy or enucleation. Twelve eyes with clear media with advanced MPP were also studies by B-scan ultrasonography and a triangular detachment could be demonstrated in each case. The finding of a triangular retinal detachment by B-scan ultrasonography in eyes with opaque media is diagnostic of advanced MPP. Eyes with this type of retinal detachment have a poor surgical prognosis even with modern vitrectomy techniques.

Adolescent↗
PubMed1977

Glial cell proliferation in human retinal detachment with massive periretinal proliferation.

By transmission electron microscopy we studied 38 epiretinal membranes obtained from human eyes by vitrectomy operation in rhegmatogenous retinal detachment. Two of the membranes were composed of closely packed glial cell processes. The cytoplasm of the glial cell processes in both membranes contained little besides loosely packed filaments and microtubules. Microvilli protruded from the cells at the vitreal surface of one of the membranes. Junctional complexes were present between the cells only at the vitreal surface. In the other glial membrane, microvilli extended into a duct-like structure with junctional complexes sealing the lumen. A discontinuous basal lamina was laid down by cell processes at the retinal side of the membranes. Similar glial membranes, formed by migration and proliferation of astrocytes from the retina, were seen in owl monkeys with experimental and naturally occurring retinal detachment. A new epiretinal membrane (reformed in one of the eyes from which a dense glial membrane had been removed three weeks previously), was composed primarily of single large cells with extensively developed rough endoplasmic reticulum. The new cells were surrounded by collagen, fine fibrillar material, and fibrin. The new membrane also contained free pigment granules and pigment-containing macrophages. Additionally, we observed spicule-like crystals between the cells in the glial membrane specimens, identified as calcium phosphates by energy-dispersive x-ray analysis.

Animals↗
PubMed1977

Results of vitrectomy for rare proliferative and hemorrhagic diseases.

We compiled the results of pars plana vitrectomy in rare proliferative and hemorrhagic diseases. In retinal vasculitis of unknown origin (perhaps Eales' disease), six out of seven eyes had visual improvement; in sickle cell disease, two out of three eyes improved. Three eyes with presumed toxocariasis were successfully treated. In retrolental fibroplasia (RLF), only lighter degrees of the cicatricial stage with traction detachments can be treated. Some cases may simulate Coats' disease. There are also cases which simulate the typical picture of RLF, where there is no history of prematurity or oxygen usage. Five patients with RLF were treated, three of these successfully. Cryoglobulinemia (one case) and hereditary hemorrhagic telangiectasia (one case) were successfully treated. Senile macular degeneration can also be an indication for vitrectomy (two out of three eyes were successfully treated).

Adolescent↗
PubMed1977

Pars plana lens removal with vitrectomy.

We used a modification of lens removal by phacofragmentation in conjunction with posterior vitrectomy without any serious complications in over 200 procedures. This modification allowed removal of hardened nuclear sclerotic lenses and reduced the time required for lens removal.

Cataract Extraction↗
PubMed1977

Massive periretinal proliferation: a logical approach to therapy.

Massive periretinal proliferation (MPP), a serious complication of retinal surgery is caused by proliferation and fibrous metaplasia of cells mostly deriving from retinal pigment epithelium and retinal glial cells. Contracting fibrous membranes in the vitreous and on and also under the retina cause the intraocular changes of MPP. Early signs such as increased "tobacco dust," pigmented clumps in the vitreous, subtle preretinal and even retroretinal membranes are usually overlooked. The late signs such as starfolds, irregular retinal folds and funnel-shaped detachments are well known. The pathogenesis of the clinically visible signs is described and a four stage classification of the disease is given. Based on the improved understanding of this disease, a new therapeutic approach is presented, with the technique of pars plana vitreous surgery. Not only vitreous membranes but also preretinal membranes are removed. Forty-seven consecutive patients who suffered from severe massive periretinal proliferation were operated on with this technique and followed for six months or more. Seventeen patients (36%) had an attached retina. Twelve patients had a major visual improvement. The major postoperative complication is phthisis bulbi (10 eyes, 21%).

Aged↗
PubMed1977

Prophylactic vitrectomy in proliferative diabetic retinopathy.

Ten eyes with proliferative diabetic retinopathy but good visual function had pars plana viterectomies in an attempt to limit the future progression of the disease and maintain the good preoperative visual acuities. This goal was successfully achieved in nine of the eyes with no evidence of new proliferations after the vitrectomy procedure.

Adult↗
PubMed1976

Retinal tears 180 degrees and greater. Management with vitrectomy and intravitreal gas.

A new technique for the treatment of giant retinal dialysis of 180 degrees or more has been devised. After the lens and vitreous have been removed via the pars plana, the patient is rotated into a prone position on a special operating table. The retina is unfolded by filling the eye completely with gas and is held in place by gas. The patient is then brought back into the normal supine position, and a scleral encircling procedure is added. The initial success rate of reattachment is 12 out of 14 cases. Afterward, many eyes develop massive periretinal proliferation. After six months or more of follow-up, the retina remained attached in six of 14 cases.

Electrocoagulation↗
PubMed1976

Pars plana vitrectomy for the management of sever diabetic retinopathy.

In 100 severely diseased diabetic eyes we performed pars plana vitrectomy. After a median follow-up time of seven months, major visual improvement was achieved in 49% of the eyes. An additional four eyes maintained a preoperatively good visual acuity resulting in an overall success rate of 53%. Eyes with only vitreous hemorrhages did better (71%) than eyes with posterior retinal detachments (31%). We did not observe new tissue proliferation in any of the operated eyes.

Cataract Extraction↗
PubMed1976

Severe perforating injuries treated with pars plana vitrectomy.

Forty-one patients underwent vitrectomy through the pars plana for sequelae of severe penetrating injuries. Almost all were inoperable by conventional techniques. After a minimum follow-up time of six months, 13 eyes (32%) had visual improvement and six (15%) were technical successes. The main cause for failure was intravitreal proliferation of fibrous tissue.

Adult↗
PubMed1976

Repair and adhesion mechanisms of the cryotherapy lesion in experimental retinal detachment.

Cryotherapy to the pigment epithelium and retina induced a proliferation and metaplasia of pigment epithelial cells, Mueller cell hypertrophy, and proliferation of astrocytes. When cryotherapy was applied to the pigment epithelium and to the retina during retinal detachment surgery, a strong adhesion developed, characterized by the occurrence of true cell junctions between pigment epithelium and retinal cells. When only the pigment epithelium was treated, the adhesion appeared weak due to the absence of microvillous interdigitations normally present between pigment epithelium and retina.

Animals↗
PubMed1975

Bright-flash electroretinography for the evaluation of eyes with opaque vitreous.

Standard retinal function tests are of limited value in assessing retinal function in eyes with opaque vitreous. We developed a method for obtaining an electroretinogram (ERG) from eyes with significant vitreous opacity by utilizing a much brighter than normal stimulating light. Of 115 eyes with vitreous opacities and good ERG responses to this bright-flash photostimulator, 47% would have been nonrecordable with a conventional ERG light source. Bright-flash ERG was often helpful in evaluating eyes with vitreous opacities for vitrectomy and was sometimes the only source of information regarding potential retinal function.

Aged↗
PubMed1975

Proliferation and metaplasia of intravitreal retinal pigment epithelium cell autotransplants.

Pigment epithelium cells autotransplanted into the vitreous cavity of owl monkey eyes, proliferated and metaplased. The metaplastic cells looked like pigmented macrophages, membrane forming fibrocyte-like cells, and frank epithelium cells. This in vivo experiment demonstrated that the vitreous cavity is an adequate culture medium for cells deriving from the pigment epithelium and that pigment epithelium cells could be the source of intraocular proliferation seen in massive periretinal proliferation.

Animals↗
PubMed1975

Autotransplantation of retinal pigment epithelium in intravitreal diffusion chamber.

Retinal pigment epithelial (RPE) cells were autotransplanted intravitreally in diffusion chambers in rabbit eyes. The RPE cells underwent transformation; first into macrophages, later into spindle-shaped cells with collagen production having epithelial cell characteristics. DNA replication, shown by autoradiography, and loss of pigment granules indicated proliferation of these cells. These results support the hypothesis that RPE proliferation and transformation play a major role in the formation of collagen containing membranes, such as are found in massive periretinal proliferation.

Animals↗