Glial cell proliferation in retinal detachment (massive periretinal proliferation)

Spontaneous resolution of massive periretinal proliferation

A bullous retinal detachment with breaks in all quadrants developed in the right eye of a 72-year-old man four weeks after he had undergone cataract extraction. The retina was reattached successfully with a 360-degree scleral buckle. Four weeks later, the retina had redetached and developed fixed folds and broad equatorial membranes. These features and the hazy vitreous suggested massive periretinal proliferation. Fourteen days later, the patient's visual acuity suddenly improved and an examination disclosed that the retina had spontaneously reattached. Visual acuity was 6/12 (20/40) and has remained stable for 14 months.

Anatomical recovery following retinal detachment: clinicopathological correlations

The histological findings in experimental retinal detachment and reattachment of the cat retina are described. Loss of photoreceptor outer segments, mounding of the apical surface of the retinal pigment epithelium, and loss of the apical villi of the retinal pigment epithelium are prominent features of the detached cat retina. Reattachment within the first week of retinal detachment is followed by good photoreceptor regeneration and orientation. Longer term detachment of 2 to 6 weeks results in poorer photoreceptor outer segment regeneration and orientation 4 weeks following reattachment surgery. These experimental results are consistent with clinical data concerning visual recovery following retinal reattachment surgery.

Surgical management of retinal detachment without cryopexy

A clinical study of eyes with rhegmatogenous retinal detachment compared the reattachment rate in two groups of eyes: in the control group, cryopexy was applied over the retinal breaks during surgery; in the test group, cryopexy was not applied. There was a similar rate of retinal reattachment in the two groups in the immediate postoperative period. However, during the long follow-up period (36 months) there was a considerable difference in the two groups. Eyes that had undergone cryopexy had a lower rate of redetachment than eyes that had not. The rate of operative and postoperative complications was low in both groups, except for periretinal proliferation, which was more frequent in the test group. These results suggest that cryopexy may lower the incidence of redetachment after retinal detachment surgery.

Simulation of massive periretinal proliferation by autotransplantation of retinal pigment epithelial cells in rabbits

We compared the clinical pattern, the histologic findings, and the electron microscopic appearance of lesions produced by the autotransplantation into rabbit vitreous of freshly harvested and tissue-cultured (250,000) retinal pigment epithelial cells. Both harvested and cultured cells formed intravitreal strands, traction detachments, and retinal puckers, resembling the most prominent features of massive periretinal proliferation in humans. Strands produced by both types of retinal pigment epithelial cells contained cells resembling myofibroblasts which may explain the contractability of the strand. The clinical, histologic, and electron microscopic observations were similar to those found in eyes injected with tissue-cultured skin fibroblasts.

Ultrastructural features of progressive idiopathic epiretinal membrane removed by vitreous surgery

Clinical and electron microscopic studies of an idiopathic epiretinal membrane that was nonvascularized and progressive showed three types of cells: (1) predominant, fibrocyte-like cells; (2) macrophage-like cells; and (3) glial cells. Most of the abundant collagen showed characteristics of normal vitreous fibrils, although thicker collagen fibrils were also present. These ultrastructural findings, when compared with previously reported features of simple and secondary epiretinal membranes, suggest that clinically complicated epiretinal membranes are composed of more than one cell type, whereas simple epiretinal membranes consist only of glial cells. The fibrocyte-like and macrophage-like cells seen in our case were interpreted as being hyalocytes, rather than being derived from glial or retinal pigment epithelial cells. We support this interpretation by the ultrastructural features of the cells, the presence of abundant normal vitreous collagen, the biologic characteristics of hyalocytes as described by other investigators, and the absence of the ultrastructural features of glial or retinal pigment epithelial cells.

Treatment of intraocular proliferation with intravitreal injection of triamcinolone acetonide

We studied the inhibitory effect of triamcinolone acetonide on experimental intraocular proliferation. Autotransplantation of fibroblasts from rabbit rump skin into the vitreous cavity resulted in intravitreal strand formation and traction retinal detachment in 36 of 43 eyes (84%) over a period of three months. A single intravitreal injection of 1 mg of triamcinolone acetonide inhibited fibroblast growth and significantly reduced the number of retinal detachments in 15 of 44 eyes (34%). Retinal neovascularization caused by fibrous strands coming into contact with vacularized retina was also reduced by triamcinolone acetonide (31 of 43 control eyes [72%] vs eight of 44 treated eyes [18%]). Intravitreal corticosteroid therapy may be an important adjunct to the therapy of perforating injuries and massive periretinal proliferation.

Ultrastructure of traction retinal detachment in rhesus monkey eyes after a posterior penetrating ocular injury

We studied the ultrastructural characteristics of an experimental model of traction retinal detachment secondary to a penetrating eye injury in the rhesus monkey. Cells with the characteristics of myofibroblasts were present in the intravitreal fibrous tissue and in epiretinal membranes. These cells were probably derived from many sources, and were capable of contraction through the mechanism of intracytoplasmic contractile proteins such as actin or myosin. The morphologic observations supported our hypothesis that traction retinal detachment is a cell-mediated event analogous to the processes of wound healing and wound contraction. The force of contraction is mediated by cell-to-cell and cell-to-vitreous connections and by glial bridges that connect epiretinal membranes to the retina. These ultrastructural studies, which provide insight into the pathogenesis of traction retinal detachment in the experimental animal model, may well have significant clinical relevance.

Surgical approaches to subretinal strands

I successfully removed subretinal strands or membranes surgically in three patients with retinal detachments. Two approaches were used: (1) by cutting through the sclera with vitreous scissors (external approach), or (2) by cutting holes through the retina (internal approach). In two cases of retinal detachment, massive periretinal proliferation occurred, one of which was successfully managed with the external approach. In the other case, recurrence of massive periretinal proliferation caused the retina to detach again. In a third case a nonrhegmatogenous retinal detachment caused by a subretinal membrane was managed successfully with the internal approach.

Recurrent macular pucker

A 43-year-old man with a history of multiple anterior segment operations had a severe preretinal membrane affecting macular function. The bulk of this lesion was removed by using vitrectomy techniques, but a recurrence of preretinal tissue was observed a few months after this procedure. The recurrent epiretinal membrane was removed in a second operation.

Pars plana vitrectomy in ocular trauma

Visual improvement was achieved in 62% of 100 consecutive patients with ocular trauma treated by pars plana vitrectomy. Anterior segment injuries had a better prognosis than posterior segment injuries, and retinal detachment was a poor prognostic sign. Patients undergoing vitrectomy during the two weeks after injury had a better visual prognosis than those who had delayed vitrectomy. Pars plana vitrectomy has increased the recovery rate in traumatized eyes which previously were deemed inoperable and frequently were enucleated. Most such eyes have intraocular fibrocellular proliferations, resulting in traction retinal detachments, cyclitic membranes, and phthisis, as documented in clinicopathological and experimentally produced specimens of penetrating ocular trauma. Vitrectomy can interrupt this sequence, if performed one to 14 days after injury, by removing the vitreous scaffold onto which proliferation occurs, together with the elements of hemorrhage, damaged lens, vitreous, and foreign material which may incite proliferation. We believe four to ten days after injury to be the optimal time for vitrectomy to avoid the hazards of immediate intervention, while removing damaged tissue before serious sequenlae occur.

Scanning electron microscopy of the vitreous body. Massive vitreous retraction after perforating injury

Scanning electron microscopy of vitrectomy material shows a disintegrated vitreous fibril network which is partly replaced by newly formed collagen fibers and invaded cells.

Histology of wound, vitreous, and retina in experimental posterior penetrating eye injury in the rhesus monkey

We performed a histologic study to support our clinical observations on the mechanisms responsible for traction retinal detachment after a penetrating injury in the rhesus monkey eye. The monkey eyes (40 eyes; 40 monkeys) were characterized by intraocular fibrosis with the formation of a cyclitic membrane and epiretinal and subretinal membranes. The progression to a fibrous ingrowth from the wound occurred only in eyes with blood in the vitreous. The intravitreal fibroblastic proliferation had its origin mainly from the stroma of the ciliary body and choroid at the wound but probably also from the nonpigmented ciliary epithelium. A fibroblastic response was present within the vitreous as early as four days after injury, and had progressed to form a cyclitic membrane by six weeks. Epiretinal membranes were identified as early as four weeks after injury. They were most prominent over the peripheral retina anterior to the equator. It is likely that they are derived from multiple cellular sources including the fibrous ingrowth from the wound but they were also connected to the surface of the retina by bridges of tissue indicating a glial origin. The subretinal membranes appeared to be derived from both retinal pigment epithelium cells and glial cells.

Vitrectomy techniques in retinal reattachment surgery

Vitreous surgery techniques are useful in the management of selected retinal detachments with an otherwise poor prognosis. Vitrectomy methods can be used to remove intraocular opacities; cut vitreous sheets causing vitreo-retinal traction and separate epiretinal membranes covering or distorting the retina; provide a fluid space to aid in creation of a scleral buckle or use of an intravitreal gas bubble; perform other intraocular procedures, including transvitreal treatment of retinal breaks, transvitreal removal of subretinal fluid, and intraocular fluid-gas exchange. These surgical capabilities can be combined with conventional retinal reattachment methods to treat selected types of retinal detachment. The surgical techniques, indications for surgery, and role of vitrectomy methods in the current management of retinal detachment are reviewed.

Pathology of pars planitis

Seven eyes and one vitrectomy specimen from seven patients with pars planitis and complications such as secondary glaucoma and phthisis bulbi were studied histopathologically. Two of the specimens were also examined by electron microscopy. All cases showed a typical intravitreal "snowbank" opacity overlying the pars plana. On light microscopy, these "snowbanks" appeared to consist of a loose fibrovascular layer containing occasional fibrocyte-like cells and scattered mononuclear inflammatory cells adjacent to the hyperplastic nonpigmented epithelium of the pars plana. Within the vitreous base, an extensive fibroglial proliferation had developed, often drawing the peripheral retina anteriorly into the "snowbank." Electron microscopy showed this fibroglial tissue to be composed of condensed vitreous collagen and probable fibrous astrocytes which had produced larger-diameter (about 24 mm) collagen fibrils. The fibroglial proliferation also appeared continuous with an ultrastructurally similar preretinal fibroglial membrane. All eyes showed prominent lymphocytic cuffing and mural infiltration of retinal veins, with sparing of the arterioles. Several cases showed cystoid macular edema. Only mild choroiditis or cyclitis could be shown in some cases. We believe that in pars planitis the fibroglial "snowbank" may reflect a common inflammatory process involving both the peripheral retina and vitreous base.

Pathogenesis and classification of massive periretinal proliferation

Massive periretinal proliferation (MPP), a serious complication of retinal detachment, 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 and unpigmented clumps in the vitreous, and subtle preretinal and even retroretinal membranes are usually overlooked. The late signs such as starfolds, irregular retinal folds, circumferential folds, and funnel-shaped detachments are well known. The pathogenesis of the clinically visible signs is described, and a 4-stage classification of the disease is given.

[Studies on fibrous and fibro-glial surface wrinkling retinopathy by scanning electron microscopy (author's transl)]

The scanning electron microscope was used to examine 16 cases of epiretinal membrane formation and retinal puckers which occurred in a variety of primary retinal disorders. In this first section the authors describe three types of epiretinal membranes: (1) Fibrous acellular membranes with and without vitreous adhesions. Retinal puckering was caused by vitreous traction with collagen strands binding the residual folds. (2) Fibrous membranes containing isolated glial cells. (3) Fibrous membranes partly covered by sheets of glial cells. In all three forms the acellular fibrous component is believed to represent vitreous cortex remnants. The invariable presence of these fibrous membranes at sites of retinal pucker and their relationship to wrinkled internal limiting membrane suggests that contraction of these membranes is responsible for retinal puckering. Morphological evidence of glial membrane contraction and collagen production by glial cells was not found.

A logical approach to the treatment of massive periretinal proliferation

Based on the improved understanding of massive periretinal proliferation (MPP) as a proliferative membrane-forming 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 was phthisis bulbi, found in ten eyes (21%).

Proliferations in the vitreous cavity after perforating injuries. A histopathological study

Histologic specimens from 32 human eyes that had been enucleated at different intervals after servere injuries were studied. Following the rules of general wound repair, intraocular proliferations start two to four days after the injury and may be massively developed within one week after injury. Their cell composition and extent are related to the site and extent of tissue damage and the amount of hemorrhage. The findings support the recommendation of a primary vitreous repair in severely injured eyes.

Pigment epithelial proliferation in human retinal detachment with massive periretinal proliferation

Biopsy specimens from vitreous and preretinal membranes, obtained during vitreous surgery from 39 human eyes suffering from massive periretinal proliferation, were examined electron-microscopically. Analysis of the cellular membranes demonstrated mostly cells with epithelial characteristics: polarization of the cells, basal lamina formation, specialized cellular junctions, and microvilli formation. These epithelioid cells contained prominent rough endoplasmic reticulum, glycogen deposits, a multitude of cytoplasmic filaments, some resembling myofilaments, and nonmembrane bound, sometimes wedge-shaped pigment granules. Macrophages were interspersed in the membranes. There was a striking similarity of these findings to those of an experimental model of retinal detachment in owl monkeys, We concluded that most likely the described cells derived from cells of pigment epithelial origin.

The incidence of macular pucker after retinal detachment surgery

In a study of 63 cases of macular pucker among 857 patients who underwent retinal detachment repair, we isolated several statistically significant risk factors: preoperative vision of less than 6/15 (20/50); preoperative presence of rolled edges, starfolds, or equatorial ridges; re-operations; choroidal hemorrhage; and age past 30 years. We were unable to confirm the risk associated with vitreous loss, vitreous hemorrhage, and degeneration. Results suggested that macular pucker after detachment surgery is produced by a membrane similar in origin to those causing other forms of periretinal proliferation.

The ultrastructure of preretinal macular fibrosis

A case of preretinal macular fibrosis, following long-standing central vein occlusion and hemorrhagic glaucoma, was examined macroscopically and electron-microscopically. Pretreatment with cyclodiathermy puncture was performed twice before enucleation. The following morphologic results were observed: 1. Epiretinal cell layers in the peripapillar and foveolar regions which caused no 'puckering' of the retinal surface. These cell layers were mainly composed of glial cells. Some Müller cell processes and macrophages were also present. The epiretinal glial cells stem from the surface of the papilla and of the retina. They leave the retina through breaks of the basal lamina (especially where the latter is only a thin layer). 2. Folding (puckering) of the retinal surface was exclusively observed under condensed masses of fibrous tissue. The epiretinal fibrous tissue is composed of immature collagen fibrils of various diameters, of acid glycosaminoglycans, and of granular deposits of long-spacing collagen. The fibrillar material is firmly attached to the basal lamina of the retina. Shrinkage of the epiretinal fibrous tissue similar to the shrinkage of scar tissue is assumed to be the reason for the development of traction to the retinal surface. The epiretinal glial cells are assumed to be the sites of synthesis of the preretinal fibrous masses and glycosaminoglycans.

The association of retinitis pigmentosa with preretinal macular gliosis

A retrospective study of the histopathological features of retinitis pigmentosa was undertaken. A consistent finding in 10 out of 10 eyes from 6 patients with retinitis pigmentosa was the presence of a preretinal membrane. The frequency of this finding has not been noted previously. Preretinal gliosis may well be responsible for the production of the abnormal glinting fundus reflex seen at the posterior pole in retinitis pigmentosa.

Retinal mobility and retinal detachment surgery

A series of 200 consecutive retinal detachments was examined prospectively to consider the physical sign of mobility of the detached retina. Retinal mobility was found to be absent in 28 cases, and this immobility is caused by periretinal membrane formation. The importance of retinal mobility when considering the case for non-drainage retinal surgery has been examined with particular emphasis on the tear/buckle relationship at the end of the operation. It was found that there was an excellent prognosis (92% success rate) for cases in which the retina was found to be mobile in the vicinity of the retinal tear, and a high proportion of these cases (71%) can be successfully treated with a non-drainage operation.

Ultrastructure of epiretinal membrane removed by pars plana vitreoretinal surgery

Electron microscopic study of an epiretinal membrane obtained from a 69-year-old black woman during pars plana vitreoretinal surgery with vitreous hemorrhage complicating a retinal vein obstruction revealed extensive proliferations of fibrous astrocytes that had secreted fibrillar and basement-membrane collagens. Hemosiderin-containing macrophages were also found. Neovascular elements were present and appeared identical to normal retinal capillaries.

Pigmented preretinal membranes

Continuous growth and an increase in pigmentation of a preretinal membrane occurred in a 46-year-old woman after a scleral buckling procedure for rhegmatogenous retinal detachment. Ten additional patients had pigmented preretinal membranes in eyes treated for rhegmatogenous retinal detachment. Although we made no attempts to determine the incidence of pigmented preretinal membrane formation in eyes with retinal detachments, these 11 cases, in a consecutive series of 500 eyes treated for rhegmatogenous retinal detachment, indicated that the development of pigmented preretinal membranes is not uncommon. Our clinical observations supported recent experimental findings implicating retinal pigment epithelial cells as a cause of preretinal membrane formation.

Spontaneous separation of preretinal macular fibrosis

A dart entered the eye of a 6-year-old boy causing a retinal hole located inferotemporal to the macula. The retinal hole was treated with an argon laser, and two months after the injury, tissue organization in the vitreous track created by the dart caused a limited retinal separation and stress lines. A preretinal fibrosis developed above and temporal to the macula, and visual acuity decreased to 6/60 (20/200). Four months after the injury, the preretinal membrane spontaneously separated from the macula to an extramacular nidus, and visual acuity subsequently improved to 6/9 (20/30).

[Findings on retinal surface by scanning electron microscopy. I. Retinal holes (author's transl)]

The findings by scanning electron microscopy on three retinal holes are described. An outgrow of a glial membrane with microvilli from the holes to the retinal surface can be seen. This epiretinal cell membrane grows on a felt of collagen fibres of the vitreoretinal borderlayer. Rudiments of visual receptors project from the deep walls into the holes. The layer of the pigment epithelial cells beneath the holes is remarkable by the abundance of microvilli.

Contraction of a perifoveal epiretinal membrane simulating a macular hole

Four patients observed for a three- to four-year period had a hole in an epiretinal membrane overlying the macula that mimicked a macular hole. In two patients the clinical appearance remained essentially constant. In one, the epiretinal membrane contracted further, reducing the apparent macular hole to a slit and causing the typical appearance of a macular pucker. In the fourth patient, the epiretinal membrane peeled spontaneously causing the apparent hole to disappear. None of the patients had static perimetric findings that suggested a true macular hole. All of the patients had normal or nearly normal visual acuity when first seen. This was maintained except in the patient who suffered further membrane contraction. Fluorescein angiography demonstrated a slight fluorescence in the base of the hole in three of the four patients; however, it was not as pronounced as one sees in true macular holes. Lamellar macular holes characteristically show no fluorescence in the area of the hole.

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.

[On the ultrastructure of proliferative changes (cell metaplasia) in the retinal pigment epithelium over malignant melanomas of the choroid (author's transl)]

Proliferations of the retinal pigment epithelium over malignant melanomas of the choroid from three human eyes were examined at various locations: 1. at the posterior pole, 2. in the equator region, 3. at the ora serrata. The observation was made that in each proliferation one cell type dominates which could be distinguished by its shape and cytoplasm from those of the other proliferations. Only the cells of the proliferation at the posterior pole correspond with the normal pigment epithelium. Most of the cells in the equator region show several properties of glia cells whereas these of the ora resemble fibroblasts. Our findings suggest that the proliferated pigment epithelium over malignant melanomas of the choroid is capable of undergoing metaplastic changes.

Clinical-pathological correlation in massive periretinal proliferation

In the owl monkey, proliferation of pigment epithelial and glial cells occurred in varying degrees in nearly all eyes with retinal detachments. These cells grew and formed membranes on all available intraocular structures in the posterior part of the eye, such as vitreous structures and inner and outer retinal surfaces. Clinically, this process covered a wide variety of lesions, including fixed retinal folds. Depending on the location, size, and extent of the pigment epithelial or glial membrane, different types of fixed folds occurred. In an exaggerated end stage of this proliferative process, a clinical picture may develop identical to what has been called massive vitreous retraction or massive preretinal retraction in humans. To emphasize the importance and ubiquity of cellular proliferations, we called this entity massive periretinal proliferation.