Intraocular beta-radiation for proliferative vitreo-retinopathy.

Proliferative vitreoretinopathy (PVR) is the most common cause of failure in retinal detachment surgery. PVR is a result of an enhanced healing process. Various surgical and pharmacological methods have failed to provide a definite solution to the problem. Radiation has since long been shown to be effective in similar situations like keloids, pterygia, and post trabeculectomy. Externally delivered radiation has also been tried in PVR, but with limited success. We propose that treatment with intraocularly delivered beta-radiation is a viable method to try and reduce the incidence of PVR after retinal detachment. This can improve the safety of the treatment, reduce potential side effects to surrounding tissues and help achieve a targeted treatment. However, the treatment was limited by the absence of a practical method for intraocular delivery of radiation. This is now possible, as we now have a method which has been shown to be safe in the CABERNET trial. If this can be proved, then it will be an important step towards treating PVR and hence reducing blindness after retinal detachment.

Experimental posterior perforating ocular injury in rabbit eyes: effects of radiotherapy with or without intravitreal cyclosporin on vitreous proliferation.

Double perforating ocular injuries were made in 30 rabbits and the effects of radiotherapy (RT) alone or in combination with cyclosporin (CS) on vitreous proliferation investigated. Thirteen rabbits in group 1 received RT alone (600 cGy), and 13 rabbits in group 2 received RT combined with 100 microg of intravitreal CS. No treatment was given to 4 rabbits in the control group (group 3). All animals were ophthalmologically examined on the 1st, 3rd, 7th, 14th and 28th days following the injury and the clinical findings scored; they were sacrificed on the 28th day, and histopathological scoring was made. The median histopathological score of the RT group (4.0; range: 0-8) was significantly higher than that of the CS + RT group (1.0; range: 0-5; p = 0.018). We conclude that intravitreal CS may be used as an adjunctive agent to RT to inhibit intraocular proliferation following penetrating ocular injury in rabbits.

[Low dosage radiotherapy of subfoveal neovascularizations in age related macular degeneration. Results after 6 weeks and 6 months]. / Niedrig dosierte Radiotherapie der subfoveolären Neovaskularisationen bei altersabhängiger Makuladegeneration. Resultate nach 6 Wochen und 6 Monaten.

AIM OF THE STUDY: The aim of this pilot study is to test the effect of low dose radiation on classic and occult subfoveal neovascular membranes (SNVM) in age-related macular degeneration. METHODS AND PATIENTS: From November 1993 through to May 1995 the macula of the affected eye was irradiated with 5 Gy for 12 patients and with 8 Gy for 34 patients. The radiotherapy was done ambulatorily by a linear accelerator 6 MeV during 4 consecutive days with daily 1.25 Gy and 2 Gy respectively. A "half beam technic" was used to protect the lens. Before the treatment, 6 weeks and 6 months later different parameters of the visual acuity were measured and a simultaneous Fluo- and ICG-angiography was done. RESULTS: In the 5 Gy group, all the planned controls were done for 11 patients. 9 membranes were classic and 2 occult. After 6 months the vision in the distance remained the same in 7 cases, was better in 2 cases and worse in 2 cases. The size of the membrane increased in 10 cases and remained unchanged in 1 case. In the 8 Gy group, all the planned controls were done for 29 patients. 12 membranes were classic and 17 occult. The vision in the distance remained the same in 17 cases, was better in 4 cases and worse in 8 cases. The size of the membrane increased in 12 cases and there was no change in 17 cases. DISCUSSION AND CONCLUSION: Exact comparisons between the 5 Gy and 8 Gy group are not possible because of the different composition of these groups. In no case were we able to note a reduction of the size of the membrane. Concerning the visual acuity, our results are better than the spontaneous evolutions described in the literature. Meanwhile, affirmations about possible stabilisation of the visual acuity are too early. A further study which is being done in our hospital may possibly bring new information.

Experimental perforating injury with high energy electrons to inhibit intraocular proliferation.

Since 1980, the fibroblast model creating experimental proliferative vitreoretinopathy has been used to evaluate the antiproliferative effect of various drugs. In previous studies radiation therapy was found to reduce effectively intraocular proliferation in this model. We therefore investigated the effect of high energy electrons in a standard perforating injury model creating a traumatic proliferative vitreoretinopathy. In 36 eyes we performed a 8 mm pars plana incision and injected 0.4 ml of 80% fibronectin solution intravitreally. Ten rabbits (20 eyes) received radiation therapy with a Betatron accelerator in a total dosage of 3000 cGy to each eye divided into 10 single fractions starting on the first post-operative day. Maximum concentration of the dose was focused to the posterior vitreous. The other 9 rabbits, 18 eyes, served as control. In our perforating injury model we observed a reduction of retinal detachment rate of 72% in the controls to 55% in the treated group. The effect of radiation therapy with high energy electrons and total dosage of 3000 cGy was not statistically significant in experimental traumatic proliferative vitreoretinopathy.

The antiproliferative effect of fractionized radiation therapy: optimization of dosage.

Fractionized radiation therapy with high-energy electrons have proven to reduce retinal detachment rate from 85% to 5% in the fibroblast model using a dosage of 3000 rad, starting from the first postoperative day. The purpose of this study is to gain more information about the therapeutic range of fractionized radiation therapy in experimental PVR. We therefore investigated the efficacy of this therapy when the total dose is reduced to 2000 rad. Irradiation treatment started on the first postoperative day. Eight weeks after cell implantation 5 of 14 eyes (35%) in the irradiated group and 15 of 16 eyes of the control group (93%) showed traction detachment. The statistically significant result proves a broad therapeutic range of fractionized radiation therapy in experimental PVR. We believe that a combination with antiinflammatory drugs could lead to a dose reduction in both therapies in patients.