Epiretinal membrane formation after vitrectomy

Improvement of horizontal macular contraction after surgical removal of epiretinal membranes

PURPOSE

To determine whether horizontal macular contraction caused by epiretinal membranes (ERMs) improves after surgical removal.

METHODS

In this prospective, single-center, observational study, 63 consecutive patients with unilateral idiopathic ERM in one eye and no retinal disease in the fellow eye underwent pars plana vitrectomy. Fundus photography and optical coherence tomography (OCT) were performed preoperatively and at 3 months postoperatively. The area enclosed by superior and inferior major vessels from the optic disc to the fovea (area under major vessel (AUV)) and the macroscopic diverging angle (MDA) between superior and inferior major vessels were calculated using digital image analysis of fundus photographs and compared pre- and postoperatively.

RESULTS

AUV was significantly smaller in the eyes with ERM compared with the normal fellow eyes (P<0.001). Significant postoperative change in AUV and MDA was demonstrated after ERM removal (P<0.001). However, postoperative AUV of grade 2 and 3 ERM eyes was still significantly smaller than that of normal fellow eyes. Macular thickness differences measured with stratus OCT were positively correlated with AUV differences.

CONCLUSIONS

Retinal topographic changes caused by ERM improved in part after ERM removal. The improvement of topographic changes were correlated with tomographic changes detected with OCT.

Intravitreal injection of therapeutic agents

BACKGROUND

Intravitreal injection (IVI) with administration of various pharmacological agents is a mainstay of treatment in ophthalmology for endopthalmitis, viral retinitis, age-related macular degeneration, cystoid macular edema, diabetic retinopathy, uveitis, vascular occlusions, and retinal detachment. The indications and therapeutic agents are reviewed in this study.

METHODS

A search of the English, German, and Spanish language MEDLINE database was conducted. A total of 654 references spanning the period through early 2008 were individually evaluated.

RESULTS

The advantage of the IVI technique is the ability to maximize intraocular levels of medications and to avoid the toxicities associated with systemic treatment. Intravitreal injection has been used to deliver several types of pharmacological agents into the vitreous cavity: antiinfective and antiinflammatory medications, immunomodulators, anticancer agents, gas, antivascular endothelial growth factor, and several others. The goal of this review is to provide a detailed description of the properties of numerous therapeutic agents that can be delivered through IVI, potential complications of the technique, and recommendations to avoid side effects.

CONCLUSION

The IVI technique is a valuable tool that can be tailored to the disease process of interest based on the pharmacological agent selected. This review provides the reader with a comprehensive summary of the IVI technique and its multitude of uses.

Intravitreal and subretinal proliferation induced by platelet-rich plasma injection in rabbits

We developed an experimental model of proliferative vitreoretinopathy (PVR) in albino rabbits by combining some factors suspected of causing the disease. Sixty nine eyes divided into six groups served as controls (Groups C 1-6). Forty nine eyes were divided into four experimental groups (Groups E 1-4). Group E1 (n = 12) was injected with 0.15 ml of platelet-rich plasma. In addition, Groups E2 (n = 12) and E3 (n = 12) underwent cryotherapy or vitrectomy. Group E4 (n = 13) underwent both procedures. Seven of the 13 Group 4 experimental eyes developed total retinal detachment and giant holes. None of the other groups developed more than two total retinal detachments or giant holes (P < 0.05). Light and electron microscopy showed intravitreal or preretinal proliferation composed of fibroblast-like cells. Retroretinal membranes appeared only in Group E4 eyes, composed of elongated cells with oval nuclei and abundant organelles in the cytoplasm. We believe these lesions mimic human PVR more closely than other models previously developed.

Proliferative vitreoretinopathy--is it anything more than wound healing at the wrong place?

Proliferative vitreoretinopathy (PVR) is a reactive process of the ocular tissue after perforating trauma, retinal detachment, and surgical manipulations. Although several studies, most of them experimental, have focused on the detection of specific etiologic factors in the development of PVR, there is compelling evidence that PVR is nothing more than a physiologic tissue repair process with undesirable consequences for the retina. Important features of PVR involving the role of platelets, mononuclear phagocytes, and fibroblasts parallel the chain of events observed in tissue repair elsewhere in the body. Numerous experimental models for PVR, originally designed to find specific stimuli for the generation of intraocular traction membrane formation, have shown that the process of PVR is the common pathway of the eye's reaction to vitreoretinal trauma of any kind. Accordingly, vitreoretinal surgeons could learn a lot from the work of other disciplines, e.g. surgery and dermatology, on wound healing, and the factors known to modify wound healing elsewhere in the body should be taken into consideration. The well-established impairment of tissue repair processes caused by medical treatment with corticosteroids and cytotoxic agents suggests a combined medical approach to PVR as an adjunct to surgical treatment, using refined methods of application and dosage. Steroids and cytotoxic drugs will influence the course of PVR by suppressing macrophage recruitment and the initial inflammatory reaction as well as the proliferative phase of wound healing with traction retinal detachment, respectively.

Evaluation of radiation therapy for experimental proliferative vitreoretinopathy in rabbits

We evaluated effects of radiation therapy on experimental proliferative vitreoretinopathy (PVR) induced in rabbits by double gas compression of the vitreous followed by homologous dermal-skin fibroblast injection. Electrons were irradiated in two rabbit groups. Group A animals (20 eyes) received 1000 cGy of irradiation immediately after cell injection; group B rabbits (9 eyes), which showed pucker formation 7 days after cell injection, were irradiated on that day at the same dose as was given to group A rabbit. Control animals (14 eyes) were not irradiated. The incidences of traction retinal detachment on day 28 were: control, 86%; group A, 10%; and group B, 22%. There were statistically significant differences between control and group A values and between control and group B values. No significant difference was found between group A and group B. Irradiation of 1000 cGy did not alter the histological picture of experimental PVR. The results showed that radiation suppressed the development of PVR when applied not only immediately after cell injection but also during pucker stages.

Regular silicone and fluorosilicone oil in the prevention of retinal detachment caused by experimental proliferative vitreoretinopathy

The effect of both regular silicone and fluorosilicone in preventing retinal detachment caused by experimental proliferative vitreoretinopathy was studied in rabbit eyes which received 250,000 fibroblasts after vitrectomy and lensectomy. In the control group, 14 out of 20 eyes which received fibroblasts had retinal detachments with disorganization of internal structures. In eyes receiving fibroblast and regular silicone, 4 out of 20 eyes had shallow retinal detachment. In the eyes receiving fibroblasts and fluorosilicone, 5 of 28 eyes had shallow retinal detachment. Our findings indicate that both regular silicone and fluorosilicone were effective in preventing retinal detachments caused by experimental proliferative vitreoretinopathy. There was no statistical difference between the two silicone oils.

Nd-YAG laser treatment in preretinal macular fibrosis

Three eyes with preretinal macular fibrosis (PMF) were treated with the Q-switched Nd-YAG laser. The PMF was idiopathic in two eyes and associated with a vitreous hemorrhage, due to ocular trauma, in the third eye. The three eyes had in common a partial posterior vitreous detachment with vitreous traction on the macula. The Nd-YAG laser beam was focused on the detached posterior hyaloid in front of the macular region. Some holes were made in this membrane or in the adjacent collapsed vitreous cortex. Treatment increased the visual acuity in the three eyes; the vitreous remained partially detached in the two eyes with idiopathic PMF and detached completely in the eye with the secondary PMF. The disentanglement of the fovelar area was revealed by the unfolded appearance of the retinal vessels on fluoangiography.

Classification of the stages of proliferative vitreoretinopathy in a refined experimental model in the rabbit eye

Eighty-four rabbit eyes injected intravitreously with tissue-cultured fibroblasts following gas compression of the vitreous were examined clinically over a period of 1 month. Detailed clinical descriptions of the extent of retinal changes were recorded. Clinical landmarks were determined and arranged into a new classification of this model of proliferative vitreoretinopathy (PVR). The proposed classification will allow easier communication between research groups using this model to study the treatment and prevention of PVR.

Human retinal pigment epithelial cells in the vitreous of the owl monkey

Cultured human retinal pigment epithelium was injected into the vitreous of owl monkeys. The epithelial cells were derived from either a foetal or an adult cell line. The five monkeys which were injected with cultured foetal cells developed substantial vitreal membranes and had retinal detachment by 2 weeks, whereas the five monkeys with cultured adult cells did not develop detachments within the period of investigation, and vitreal membranes were insubstantial. An electron-microscopic, immunohistochemical and autoradiographic study was conducted on these eyes to investigate in detail the behaviour and intraocular effects of the injected cells.

Retinal toxicity of amphotericin B in vitrectomised versus non-vitrectomised eyes

The retinal toxicity of intravitreally administered amphotericin B was compared in non-vitrectomised versus vitrectomised rabbit eyes. Doses of 5 and 10 micrograms in both groups resulted in transient vitritis but had no effect on electroretinograms. Histopathological examination four weeks after injection showed vitreous cells and minimal areas of retinal necrosis in both groups at 5 or 10 micrograms doses. At these doses vitrectomy did not modify the retinotoxic effects of intravitreally administered amphotericin B. At higher doses marked toxicity was found in both vitrectomised and non-vitrectomised groups.

Experimental posterior perforating ocular injury: a controlled study of the gross effects of localised gamma irradiation

A pilot study on the effect of localised irradiation applied to the site of a standard perforating injury in the rabbit eye, showed that gamma rays limited the formation of post-traumatic vitreoretinal membranes. A controlled study was therefore undertaken to confirm this observation. Twenty-four pairs of rabbits underwent a standard perforating injury in the right eye. One rabbit of each pair received a radioactive ophthalmic Cobalt applicator and the other a dummy applicator. Nineteen of 24 non-irradiated eyes developed vitreoretinal membranes, with associated traction retinal detachment. Only four of 24 irradiated eyes developed traction retinal detachment.

The effects of injections of cultured fibroblasts into the rabbit vitreous

A comparison was made between rabbit's eyes which had an intravitreal injection of either 400,000 autologous or homologous skin fibroblasts. The follow-up period was up to 6 months with autologous and 10 weeks with homologous cells. The evaluation involved the clinical assessment of membrane formation, retinal detachment and anterior segment inflammation. In addition, a detailed histological, electron microscopic and autoradiographic study was made of membrane development and changes in the surrounding tissue. Clinical evaluations revealed little difference between the two models. However, on the basis of macroscopic and microscopic examination, homologous cells produced more extensive detachments and more pronounced retinal gliosis. Plasma cells were evident in the choroid 6 weeks after homologous fibroblast injection, but they were not associated to any appreciable extent with the autologous model. Fibrovascular proliferation from around the optic nerve head made a major contribution to the formation of membranes in the experiments with homologous fibroblasts but not those using the autologous cells.

5-fluorouracil: new applications in complicated retinal detachment for an established antimetabolite

Long-term reattachment of the retina following the development of proliferative vitreoretinopathy is often prevented by the occurrence of cellular reproliferation. 5-fluorouracil, a synthetic pyrimidine analog, is a potent inhibitor of fibroblast proliferation in cell culture and an animal model of tractional retinal detachment. Doses of up to 1.0 mg, when administered intravitreally to rabbits, result in no demonstrable retinal toxicity by microscopic and electrophysiologic criteria. The first 22 consecutive patients with advanced forms of proliferative vitreoretinopathy were treated with a combination of periocular and intraocular 5-fluorouracil, in addition to scleral buckling and vitrectomy. Retinal reattachment was achieved in 60% of patients at 6 months postoperatively. No serious systemic or ocular complications were observed although delayed healing of corneal epithelial defects occurred in 18% of cases and subtle subepithelial scarring in 31.8%. In combination with standard vitrectomy techniques, post-operative fluid gas exchange, and photocoagulation, periocular and subconjunctival 5-fluorouracil appears to improve the prognosis for longterm retinal reattachment following the development of proliferative vitreoretinopathy.

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.

Temporary use of silicone oil in the treatment of proliferative vitreoretinopathy. An experimental study with a new animal model

Homologous fibroblasts were injected into vitrectomized rabbit eyes. This injection produced a total retinal detachment in all ten eyes of a control series. In each case the detachment was due to the contraction of a membrane which had grown on the retinal surface as seen in human proliferative vitreoretinopathy (PVR). In another group of ten eyes, silicone oil was injected before the fibroblastic membrane contracted, and removed again a few weeks later. This temporary tamponade of silicone oil reduced the rate of detachment to 50%. Silicone oil did not prevent the preretinal membrane from growing but mechanically decreased its contraction.

Fluorouracil therapy for proliferative vitreoretinopathy after vitrectomy

Fluorouracil effectively inhibits epiretinal membrane formation and traction retinal detachment after vitrectomy surgery. When 0.5 mg of fluorouracil was administered intraocularly every 24 hours for seven days, traction retinal detachment two weeks after the intraocular injection of 200,000 cultured retinal pigment epithelial cells occurred in 12 of 12 control eyes but in only six of 14 eyes treated with fluorouracil (P less than .001). Four weeks after cell injection, eight of 12 eyes treated with fluorouracil had traction retinal detachments whereas 12 of 12 control eyes did (P less than .001). The height of the traction retinal detachment four weeks after intraocular injection of 200,000 cultured retinal pigment epithelial cells was reduced 50% in eyes treated with 0.5 mg of fluorouracil every 24 hours for seven days compared to control eyes (P less than .001). When the number of injected retinal pigment epithelial cells was increased to 400,000 cells and 1.25 mg of fluorouracil was administered intraocularly every 24 hours for seven days, traction retinal detachment two weeks after injection occurred in 15 of 15 eyes in the control group but in none of ten eyes in the treated group. Four weeks after cell injection, eight of eight eyes in the control group and five of five eyes in the fluorouracil-treated group had detachments and the mean height of the detachments in the two groups was equal. Autoradiography of the epiretinal membranes in eyes injected with 200,000 cultured retinal pigment epithelial cells and labeled for two hours with tritiated thymidine showed that 0.8% of the epiretinal cell nuclei were labeled two weeks after cell injection but that no labeled cells were present in the fluorouracil-treated eyes. Tritiated thymidine labeling of epiretinal cells in the fluorouracil-treated eyes was first noted three weeks after the cell injection. The presence of tritiated thymidine labeling in the fluorouracil-treated eyes correlated with an increase in the number of epiretinal cells and an increase in the incidence of traction retinal detachment.

Ocular toxicity of fluorouracil after vitrectomy

The retinal and corneal toxicity of fluorouracil in the rabbit eye after lensectomy and vitrectomy depended on both the dosage and the frequency of intraocular injection and was reversible at certain dosages. All eyes in Group 1 (1.25 mg of fluorouracil every 12 hours for four days and then every 24 hours for three days) had opaque corneas by three days; these did not clear for four weeks. Histologic studies showed loss of photoreceptor outer segments and loss of ribosomes in all the retinal cells examined. The electroretinographic b-wave decreased to 0% of the baseline value (no b-wave), and did not recover after three weeks. In Group 2 eyes (1.25 mg of fluorouracil every 24 hours for seven days), corneal opacification increased to a maximum after two weeks and gradually decreased by four weeks. The electroretinographic b-wave diminished to 9.6% of the baseline value at two weeks but later recovered to 62.5% of the baseline value at three weeks. Histologic studies showed loss of photoreceptor outer segments and ribosomes at nine days; both returned to near normal after five weeks. Clinical, electrophysiologic, and histologic studies showed no toxicity in Group 3 eyes (0.5 mg of fluorouracil every 24 hours for seven days). This dosage of fluorouracil exerts a significant antiproliferative effect on injected retinal pigment epithelial cells and is well tolerated by the rabbit eye.