Search PubMed⌕ Search

Biomedical subjects

R Machemer

Publications and source records attributed to R Machemer.

At least 55 records · Page 3Linked to original sources
PubMed1990

Retinopathy of prematurity: approaches to surgical therapy.

Retinopathy of prematurity (ROP) is a vasoproliferative disease with infiltration of the vitreous gel. Contraction of the infiltrate results in traction detachment with typical peripheral trough formation. Cryotherapy inhibits proliferation in the active stages of the disease (Stage 3, 'plus'). With development of traction detachment involving the macula (Stage 4B) encircling buckling procedures should first be tried. Closed vitrectomy is considered when high retinal detachment and opacification by vitreous strands occur. The surgical technique is described. Anatomical (64%) and functional (43%) successes are reasonably high for Stage 4 cases, but disappointing (anatomical 40%, functional 16%) for Stage 5 ROP. Open funnels of detached retina fare better than closed ones. It is probably best to perform surgery not before the cicatricial stage, i.e. six months after birth.

Cryosurgery↗
PubMed1990

Relaxing retinotomies. Analysis of anatomic and visual results.

The authors analyzed 100 consecutive eyes undergoing relaxing retinotomies to determine the anatomic and visual results associated with the use of this procedure. With a minimum follow-up of 6 months, 58 eyes were completely attached, 8 were partially attached (macula on), and 34 were detached. Thirty-four percent of all eyes and 50% of attached eyes obtained a visual acuity of 5/200 or greater at 6 months. At last examination, 29% of all eyes and 43% of attached eyes had a visual acuity of at least 5/200. Eyes that had circumferential relaxing retinotomies involving the entire temporal quadrant generally had lower visual acuities when compared with eyes that had relaxing retinotomies sparing the entire temporal quadrant. The use of a radial relaxing retinotomy also was associated with lower final visual acuity. The length of the relaxing retinotomy or the placement of the relaxing retinotomy either anterior or posterior to the encircling scleral buckle did not appear to influence the anatomic or visual results. Hypotony (intraocular pressure less than 5 mmHg) was seen in 43% of reattached eyes.

Adolescent↗
PubMed1990

Advanced retinopathy of prematurity. The anatomic and visual results of vitreous surgery.

The anatomic and visual results of vitreous surgery in 140 eyes of 108 children with stage 4 and 5 retinopathy of prematurity (ROP) were reviewed. Macular attachment was achieved in 9 (64%) of 14 eyes with stage 4. In stage 5 eyes, partial posterior attachment was obtained in 38 (31%) of 121 eyes and complete posterior attachment was obtained in 11 eyes (9%). Final visual acuity of fix and follow or greater occurred in 6 (43%) of 14 eyes with stage 4 and in 13 eyes (11%) with stage 5 ROP. Retinal detachment (RD) funnel configurations were classified according to the International Committee on ROP. The funnel type which was wide anteriorly and wide posteriorly had the best anatomic (63%) and visual (19%) success. Reoperation rarely improved visual acuity (4%), although reattachment was possible in 6 (22%) of 27 eyes. All children in this series underwent surgery by 2 years of age. Anatomic and visual success was achieved less often in children who underwent surgery at age 6 months or younger.

Age Factors↗
PubMed1989

Surgical management of retinal traction caused by toxocariasis.

We reviewed the results of vitreous surgery in 12 eyes of 12 patients with tractional macular detachment from Toxocara canis. We performed a vitrectomy and membrane peeling in all eyes, with additional scleral buckling in four eyes. After a minimum of six months' follow-up, ten of the 12 eyes (83%) had complete retinal reattachment. Visual acuity improved in seven eyes, two had no change, and three eyes had decreased visual acuity. Good postoperative vision correlated best with good preoperative vision. Preoperative traction retinal folds through the macula were associated with a poor visual outcome.

Adolescent↗
PubMed1989

Results of silicone oil removal in advanced proliferative vitreoretinopathy.

We reviewed the results of silicone oil removal after vitreous surgery for recurrent retinal detachment with proliferative vitreoretinopathy in 55 eyes. The minimum follow-up period was six months. Retinal detachment recurred in five eyes (9%). Evidence of recurrent epiretinal membrane formation at the time of or after silicone oil removal was noted in 21 eyes (38%). Penetrating keratoplasty combined with silicone oil removal was successful in five of six patients. Mild corneal changes noted in ten eyes (18%) remained the same or cleared in seven eyes after silicone oil removal. Overall, postoperative visual acuity improved in 24 eyes (44%), remained the same in 18 eyes (33%), and decreased in 13 (24%). In 22 eyes without clinical evidence of silicone-associated complications at the time of silicone oil removal, postoperative visual acuity remained unchanged or improved in 20 (91%).

Cornea↗
PubMed1989

Silicone oil injection after failed primary vitreous surgery in severe ocular trauma.

In 42 cases of complicated retinal detachment following trauma after failed primary vitrectomy, at six months follow-up anatomic retinal reattachment posterior to the scleral buckle was achieved in 20 of 40 eyes (50%). Of the 40 eyes, 11 (28%) had a visual acuity of 5/200 or better. Of the eyes that were completely attached posterior to the buckle at six months, 13 of the 20 (65%) remained attached at the last follow-up examination. Many patients who had visual acuities of 5/200 or better at six months experienced a progressive decrease in visual acuity over three years, primarily because of recurrent retinal detachments and corneal edema. A final visual acuity of 5/200 or better was obtained in only five of the 42 eyes (12%) at the last follow-up examination.

Acute Disease↗
PubMed1988

Ultrastructural characteristics of new vessels in proliferative diabetic retinopathy.

We studied the ultrastructural characteristics of 23 vascularized preretinal membranes removed from 22 eyes during pars plana vitrectomy for proliferative diabetic retinopathy. Traction detachment of the macula was the most frequent reason for surgery (15 of 22 eyes), followed by nonclearing vitreous hemorrhage (seven of 22 eyes). Vessels found in the membranes were studied by serial sectioning and categorized as having either developing, mature, or regressing characteristics. Developing vessels were seen in ten of 23 membranes (43%), mature vessels in 19 of 23 membranes (83%), and regressing vessels in 13 of 23 membranes (57%). Endothelial fenestrations and cell separations were rare. With three-dimensional reconstruction, we found that new vessels often extended cytoplasmic processes into the extracellular matrix and that lumina were present even at the distalmost tips of the vessels. Solid cords of endothelial cells were not seen. We concluded that in proliferative diabetic retinopathy, new vessels develop by a process of focal extracellular matrix degradation, generalized and exuberant extracellular matrix production, cytoplasmic microvillus extension into the extracellular matrix, and active lumen formation.

Adult↗
PubMed1988

Pathogenesis and therapy of traction detachment in various retinal vascular diseases.

We examined six patients with retinal vasculopathies (two cases each of angiomatosis retinae [von Hippel-Lindau disease], exudative vitreoretinopathy, and Coats' disease), who developed preretinal and vitreal membranes, retinal traction detachment, and exudation under the retina. The membranes consisted of a core of collagen of various diameter fibers usually covered on both sides by cells that displayed glial cell characteristics. The retina reattached spontaneously and exudates disappeared when traction was eliminated by vitreous surgery. Membrane formation did reoccur after vitrectomy if the vessels continued to leak, leading again to traction and subretinal exudation. Treatment consisted of surgical removal of vitreal and preretinal membranes and destruction of leaking vessels.

Adult↗
PubMed1988

Vitreous surgery for hemorrhagic and fibrous complications of age-related macular degeneration.

We applied vitreous surgical techniques in the treatment of hemorrhagic and fibrous complications of choroidal neovascular membranes by removing subretinal scars or hemorrhage, or both, in four patients. The surgical goals were achieved in all patients. Visual acuity improved in three patients. The major complication was recurrent detachment associated with large retinotomies.

Aged↗
PubMed1988

The role of ultrasound in the management of retinopathy of prematurity.

The authors reviewed the ultrasonic appearance of 54 eyes (27 patients) with advanced retinopathy of prematurity (ROP) and compared the various retinal configurations with the findings at surgery. They found that ultrasound is a sensitive indicator of retinal configuration (type and degree of retinal detachment [RD]), as well as showing the existence of subretinal or choroidal hemorrhage often present in these severely affected eyes. Ultrasound is a useful modality to evaluate, document, and follow the progression of RD in ROP.

Choroid Hemorrhage↗
PubMed1987

Ultrastructural characteristics of proliferative tissue in retinopathy of prematurity.

We examined the histologic and ultrastructural characteristics of 27 membranes (from 18 patients) removed during vitreous surgery for partial and total retinopathy of prematurity. In membranes removed anteriorly from a child with active disease, we found vessels that had characteristics of developing neovascularization. In the membranes from older infants with inactive disease (16 patients), glial cells were common and vessels, if present, had more mature characteristics. Retinal glial cells (presumably Müller cells) were seen fragmenting the internal limiting lamina and migrating into the overlying vitreous by projecting long microvilli into the vitreous cavity. Anterior membranes (13 patients), particularly in active disease, were likely to contain vessels, whereas posterior membranes (five patients) were more often avascular and were composed of glial cells.

Basement Membrane↗
PubMed1987

Long-term results of successful vitrectomy with silicone oil for advanced proliferative vitreoretinopathy.

We have analyzed the six-month, one-year, and two-year follow-up examinations in 47 patients who had silicone oil injection in combination with revision of vitrectomy for intractable retinal detachment and advanced proliferative vitreoretinopathy. A visual acuity of 5/200 or better was attained in 22 eyes at six months (47%), 17 eyes at one year (36%), and 14 eyes at two years (30%). Of eyes that were completely attached posterior to the buckle at six months, 77% remained attached at two years. In those eyes that were attached at six months, corneal decompensation was the most frequent cause of a loss of vision between six months and two years. Silicone oil was removed in 22 eyes (47%).

Corneal Diseases↗
PubMed1987

Improvement in efficacy of corticosteroid therapy in an animal model of proliferative vitreoretinopathy by pretreatment.

Intraocular injection of the corticosteroid triamcinolone acetonide reduces the incidence of retinal detachment in rabbit eyes injected with tissue-cultured fibroblasts. When the steroid was injected simultaneously with the cells, a reduction of retinal detachment from 93% (control) to 75% (treated) was achieved on day 28. When the steroid was injected 24 h preceding cell injection, the reduction of retinal detachment was from 85% (control) to 43% (treated). The development of retinal detachment is caused by proliferation of injected fibroblasts. Reduction of this proliferation is probably achieved partially through direct inhibition of mitosis, but more important may be the reduction of the reactive inflammatory process.

Animals↗
PubMed1987

Pars plana vitrectomy for vitreous amyloidosis.

Thirty-six pars plana vitrectomies were performed on 30 eyes of 17 patients with biopsy-proven vitreous amyloidosis. Reopacification of the retrolental vitreous was the most common reason for vitrectomy revision, required in 24% of patients. Complications of amyloid or vitrectomy included retinal detachment requiring scleral buckling in 17% of eyes and glaucoma requiring filtering surgery in 17% of eyes. After a mean 35-month post-vitrectomy follow-up, 48% of eyes had visual acuities of 20/40 or better, and 32% of eyes had visual acuities between 20/50 and 20/100. Twenty percent of eyes had visual acuities of 20/200 or worse due either to persistent retinal detachment, open angle glaucoma, or residual opacification of the vitreous.

Amyloidosis↗