contact with the retinal surface becomes much lower because it is diluted and washed out earlier by the fluid in the vitreous cavity. The disadvantage to this technique is the dispersion of biological stain leading to unwanted staining of the retina elsewhere. A further concern after dye administration may be the incubation time of the dye on the retinal surface. There is a recent trend toward washing out the dye no later than a few seconds after its injection.4

A novel painting brush to avoid unnecessary and nonselective staining of the entire retina during chromovitrectomy has recently been introduced. The commercially available applicator instrument called VINCE (Vitreoretinal INternal limiting membrane Color Enhancer, Dutch Ophthalmic, The Netherlands) consists of a modified backflush needle, containing an adjustable silicone tube surrounded by a metal cannula. The tube is connected to a reservoir in the handpiece filled with vital dye. The customized cartridge loading system contains the already prepared and diluted vital dye. This new device may provide a better visualization of fine, delicate, semitransparent preretinal tissues during chromovitrectomy.

MACULAR HOLE PROTECTION

There are some alternatives to avoid dye injection directly through the MH: slow injection of the dye, selective painting instrument (VINCE), or some substances over the MH, such as perfluorocarbon liquid (PFCL), autologous whole blood, or sodium hyaluronate. A known complication of their use, however, is liquid entering the subretinal space via a retinal break which can compress and disorganize the retina. In chromovitrectomy, PFCL has been used as a protective agent for the macular hole to avoid the direct contact of ICG with the subretinal space. Besides the apparent safety of this technique, the use of PFCL increases the costs and operative time while the meticulous use of a small-tip fluted needle is essential to prevent residual PFCL which could lead to retinal toxicity.

Some authors have described the use of autologous blood as a protective agent for the retina during ICG-assisted macular hole surgery.22 Clinically, small noncomparative case series showed that whole blood used in ICG-assisted vitrectomy for macular hole surgery is apparently safe, with no signs of retinal damage or residual ICG detected after 1 month.23 Whole blood could protect against physical contact of ICG with the macular hole/RPE and also could reduce the ICG retention time, thereby diminishing the risk of toxicity.

Viscoelastic in ICG-assisted vitrectomy can be used to control where the dye settles on the retinal surface to avoid staining outside the macular region. Although good visual and anatomic outcomes could be achieved with this technique, it requires more surgical time to perform fluid–air exchange and could potentially be more toxic because no additional ICG dilution occurs, as is seen with fluid-filled globe.

SUMMARY AND KEY POINTS

For vitreoretinal surgery, vital dyes enable easier identification of the semitransparent preretinal membranes. Current recommendations for the application of dyes during vitreoretinal surgery indicate that ICG, IfCG, BriB, and BroB may be the best stains for the ILM, while TB and PB may be preferred for staining the glial ERM. The highly aqueous composition of the vitreous implies that most hydrophilic vital dyes such as TB, ICG, and PB may stain the vitreous well. In addition, an excellent staining agent for vitreous visualization is the white steroid TA.

In regard to the toxicity issues in chromovitrectomy, a large number of experimental and clinical investigations in this challenging field with

vital dyes have yielded many controversial results, but nonetheless, some preliminary conclusions may be drawn at this time. First, every vital dye injected intravitreally poses a rather dose-dependent toxicity to the retinal tissue. In addition, there is strong evidence that light exposure, osmolarity, and the presence of ions such as Na+ and iodine may exert further damage to the retina. Therefore, some recommendations include very low amount of dye injection on to the preretinal membrane, avoidance of long macular exposure to endoillumination, and removal of sodium and iodine from staining solutions.

REFERENCES

1.Rodrigues EB, Meyer CH, Kroll P. Chromovitrectomy: a new field in vitreoretinal surgery. Graefes Arch Clin Exp Ophthalmol 2005;243: 291–293.

2.Rodrigues EB, Maia M, Meyer CH, et al. Vital dyes for chromovitrectomy. Curr Opin Ophthalmol 2007;18:179–187.

3.Karacorlu M, Karacorlu S, Ozdemir H. Iatrogenic punctate chorioretinopathy after internal limiting membrane peeling. Am J Ophthalmol 2003;135:178–182.

4.Rodrigues EB, Meyer CH, Farah ME, et al. Intravitreal staining of the internal limiting membrane using indocyanine green in the treatment of macular holes. Ophthalmologica 2005;219:251–262.

5.Haritoglou C, Gass CA, Schaumberger M, et al. Long-term follow-up after macular hole surgery with internal limiting membrane peeling. Am J Ophthalmol 2002;134:661–666.

6.Gandorfer A, Haritoglou C, Kampik A. Staining of the ILM in macular surgery. Br J Ophthalmol 2003;87:1530.

7.Penha FM, Maia M, Farah ME, et al. Effects of subretinal injections of indocyanine green, trypan blue, and glucose in rabbit eyes. Ophthalmology 2007;114:899–908.

8.Maia M, Kellner L, de Juan Jr E, et al. Effects of indocyanine green injection on the retinal surface and into the subretinal space in rabbits. Retina 2004;24:80–91.

9.Narayanan R, Kenney MC, Kamjoo S, et al. Toxicity of indocyanine green (ICG) in combination with light on retinal pigment epithelial cells and neurosensory retinal cells. Curr Eye Res 2005;30:471–478.

10.Penha FM, Maia M, Farah ME, et al. Morphologic and clinical effects of subretinal injection of indocyanine green and infracyanine green in rabbits. J Ocul Pharmacol Ther 2008; in press.

11.Vote BJ, Russell MK, Joondeph BC. Trypan blue-assisted vitrectomy. Retina 2004;24:736–738.

12.Guo S, Tutela AC, Wagner R, et al. A comparison of the effectiveness of four biostains in enhancing visualization of the vitreous. J Pediatr Ophthalmol Strabismus 2006;43:281–284.

13.Grisanti S, Szurman P, Tatar O, et al. Histopathological analysis in experimental macular surgery with trypan blue. Br J Ophthalmol 2004;88:1206–1208.

14.Farah ME, Maia M, Furlani B, et al. Current concepts of trypan blue in chromovitrectomy. Dev Ophthalmol 2008;42:91–100.

15.Maia M, Penha F, Rodrigues EB, et al. Effects of subretinal injection of patent blue and trypan blue in rabbits. Curr Eye Res 2007;32:309–317.

16.Mennel S, Meyer CH, Tietjen A, et al. Patent blue: a novel vital dye in vitreoretinal surgery. Ophthalmologica 2006;220:190–193.

17.Cervera E, Diaz-Llopis M, Salom D, et al. Internal limiting membrane staining using intravitreal brilliant blue G: good help for vitreo-retinal surgeon in training. Arch Soc Esp Oftalmol 2007;82:71–72.

18.Enaida H, Hisatomi T, Hata Y, et al. Brilliant blue G selectively stains the internal limiting membrane/brilliant blue G-assisted membrane peeling. Retina 2006;26:631–636.

19.Yamakiri K, Sakamoto T, Noda Y, et al. Reduced incidence of intraoperative complications in a multicenter controlled clinical trial of triamcinolone in vitrectomy. Ophthalmology 2007;114:289–296.

20.Takasu I, Shiraga F, Otsuki H. Triamcinolone acetonide-assisted internal limiting membrane peeling in macular hole surgery. Retina 2004;24: 620–622.

21.Maia M, Farah ME, Belfort Neto R, et al. Effects of intravitreal triamcinolone acetonide injection with and without preservatives. Br J Ophthalmol 2007;91(9):1122–1124.

22.Maia M, Penha FM, Farah ME, et al. Subretinal injection of preservativefree triamcinolone acetonide and supernatant vehicle in rabbits: an electron microscopy study. Graefes Arch Clin Exp Ophthalmol 2008;246:379–388.

23.Lai CC, Wu WC, Chuang LH, et al. Prevention of indocyanine green toxicity on retinal pigment epithelium with whole blood in stain-assisted macular hole surgery. Ophthalmology 2005;112:1409–1414.

Surgery and Pharmacotherapy • 5 section

●Radiation is a local, targeted therapy designed to kill cancer cells or abnormal tissues such as neovascularization. Radiation therapy can be effectively used to treat several types of tumors.

●Treatment planning and strategy are paramount to obtain positive clinical results. For each case there is a specific preferred treatment plan.

●The total amount of radiation dosage is based on the type and size of tumor.

●Radiotherapy is continuously evolving and newer techniques are allowing for greater energy control, broadening its clinical use.

●Combined therapy using vascular endothelial growth factor (VEGF) inhibition and radiation is emerging as a potential new treatment modality for eyes with exudative age-related macular degeneration.

●Many radiation side-effects are long-term and have an impact on clinical results.

INTRODUCTION AND HISTORY

The use of radiation to treat eye diseases was pioneered by Verhoeff and Reese in the early 1900s.1 In 1930, Moore described the use of radon seeds to treat choroidal sarcoma.2 Since these early reports, several forms of radiation have been developed to treat eye tumors and, despite the significant complications from various sources of radiation, it remains a reasonable alternative to enucleation. Although ocular radiotherapy is mostly used for the treatment of melanomas, it has also been used to treat other ocular tumors.

Radiation therapy to treat subfoveal choroidal neovascularization (CNV) secondary to age-related macular degeneration was first described in 1993 by Chakravathy et al. reporting the preliminary results of a series of 19 patients treated with external beam radiation.3 Since then, there have been numerous studies evaluating the effects of radiation for the treatment of age-related macular degeneration but its use remains controversial. Studies using an anti-VEGF drug combined with radiotherapy were published by Mauceri et al. in 1998 and 1999 for the treatment of tumors.4–6 These studies demonstrated that the efficacy of radiation therapy may be potentiated by brief concomitant exposure of anti-VEGF drugs. Recently, this new treatment paradigm combining angiogenesis inhibitors and radiotherapy is showing promise for the treatment of eyes with exudative age-related macular degeneration. One new strategy involves the intravitreal administration of two injections of the anti-VEGF antibody (Lucentis or bevacizumab) combined with a single treatment with 24-Gy beta-radiation (stron- tium-90 (Sr-90)).7

The radiation effects on tumors include necrosis, tumor blood vessel damage, inflammation, and fibrosis. Tumor irradiation lowers the mitotic rate,8 the proliferative activity,9 and the microvascular density.10 Irradiation causes blood vessel damage, necrosis, and hypoxia, resulting in tumor shrinkage.11

Histopathologic studies in eyes with melanoma enucleated after plaque therapy include tumor cell necrosis, vascular obstruction, fibrosis, inflammatory cells (macrophages), vacuolization, and balloon cell degeneration.11 Radiation changes in other ocular structures have also been reported and include subretinal gliosis, chorioretinal atrophy, scleral necrosis, and iris neovascularization.12

In a study by Maureci et al., the authors combined radiation with angiostatin to target tumor vasculature that is genetically stable.4 Their results showed an antitumor interaction between ionizing radiation and angiostatin for four distinct tumor types, at doses of radiation that are used in radiotherapy. Importantly, the combination produced no increase in toxicity towards normal tissue. In vitro studies showed that radiation and angiostatin have combined cytotoxic effects on endothelial cells, but not tumor cells. In vivo studies showed that these agents, in combination, target the tumor vasculature. These results provided support for combining ionizing radiation with anti-VEGF drugs to improve the cytotoxic effects of tumor endothelial cell without increasing deleterious effects.

Another study by Gorski et al. in 1999 showed in four separate tumor model experiments a more significant tumor growth delay with combined therapy compared to either anti-VEGF therapy or radiotherapy alone.6 This group concluded that radiation up-regulates endothelial cell production of VEGF, which in turn acts as a survival factor, and that VEGF inhibition counters this survival effect.

Lee et al. were able to demonstrate a significant reduction in tumor microvessel density (36–60%) and interstitial fluid pressure (approximately 75%), and an increase in po2 with anti-VEGF therapy compared to controls. The increase in po2 may have been due to an improvement in the quality of oxygen delivery, partly owing to a decreased interstitial fluid pressure. They hypothesized that anti-VEGF therapy should decrease interstitial fluid pressure, resulting in radiosensitization.13

In a study by Geng et al. it was demonstrated that VEGF receptor may be a therapeutic target to improve susceptibility to radiotherapy. The authors concluded that anti-VEGF drugs, in certain conditions, act synergistically with radiotherapy.14

Additional work by Griffin et al.15 and Ning et al.16 found a greater than additive effect on tumor growth delay with combined therapy using SU6668, a broader tyrosine kinase antagonist of VEGF, and one group confirmed an increase in po2 after treatment with SU6668.15,16 Furthermore, SU6668 was found to have a greater therapeutic effect than SU5416 by almost doubling the tumor growth delay from 6.5 to 11.9 days. Griffin et al. concluded that SU6668 increased the radiosensitivity of tumor blood vessels.15 Ning et al concluded that inhibition of VEGF, fibroblast growth factor, and platelet-derived growth factor