Eyeworld

79 EW INTERNATIONAL December 2016 by Stefanie Petrou Binder MD, EyeWorld Contributing Writer effectiveness ratio in patients with macular thickness of less than 400 µm when compared to ranibizumab. From a pharmacoeconomic point of view, subthreshold laser is superior to anti-VEGF drugs in patients with a thinner retinal profile. Subthresh- old laser also has less safety issues as compared with standard laser, as seen in the mETDRS study, and anti-VEGF therapy." The large multicenter, ran- domized Early Treatment Diabetic Retinopathy Study (ETDRS) revealed that laser treatments significantly reduced the risk of moderate visual loss, as demonstrated in more than 3,000 patients affected by DME. 1 With the advent of VEGF inhib- itors, however, several large clinical trials showed definitive evidence that laser therapy, such as macular laser photocoagulation, was inferior to an- ti-VEGF treatment. The RESTORE tri- al presented overwhelming evidence to this end, in its comparison of ran- ibizumab to laser or the combination of the two in treating 345 individuals with diabetic macular edema, with a follow-up of 12 months. 2 Ranibizum- ab either alone or combined with laser was more effective than stan- dard laser alone, achieving superior visual acuity gains in patients with visual impairment due to DME and revealing no difference between the two groups. After 1 year, all RESTORE pa- tients received ranibizumab on an "as-needed" basis. Laser patients re- ceiving ranibizumab from month 12 onward demonstrated gradual im- provements in visual acuity, accord- ing to data of mean change in BCVA Lasers hold fast in the presence of anti-VEGF therapy for DME T he stunning outcomes achieved with anti-vas- cular endothelial growth factor (VEGF) drugs in the treatment of diabetic macular edema (DME) have misled some into thinking that lasers had been made redundant, when in reality their role in the treatment of macular edema is well preserved. New evidence seems to indicate that subthreshold laser treatments resulted in matched or improved efficacy over conventional laser photocoagulation when applied in patients with DME, mirroring visual acuity improvements achieved with anti-VEGF agents. Valentina Sarao, MD, assistant professor, University of Udine, Udine, Italy, presented the results of her findings at the 2016 German Ophthalmological Society (DOG) meeting. DME therapy evolution "The management of DME has changed over time due to the in- troduction of anti-VEGF agents and steroids. Laser treatment, however, is still widely used according to nu- merous reports on laser photocoagu- lation in the published media every year," Dr. Sarao said. The effects of laser therapy may not be as immediate as those of anti-VEGF injections, but studies show that they last longer and cost much less. According to Dr. Sarao, "Laser has a better incremental cost/ Lasers in DME: In or out? Presentation spotlight continued on page 80 from baseline. "The key message of this study is that laser treatment can be followed by ranibizumab therapy with good results. More interesting results, however, can be seen from the subgroup analysis, showing that laser performed equally well as anti-VEGF therapy in patients with thinner retinas, i.e., with lower cen- tral retinal thickness (CRT) values," Dr. Sarao said. "Another important aspect to consider is safety. Complications such as endophthalmitis, retinal detachment, and systemic adverse events should be taken into account when choosing a pharmacologic strategy. Visible end point laser pho- tocoagulation does not carry the risk of systemic adverse events, although it may lead to local complications such as long-term enlargement of retinal pigment epithelium (RPE) atrophy or the development of choroidal neovascularization," she noted. Light lasers Citing a trial that implemented "light laser" photocoagulation for clinically significant macular edema, Dr. Sarao observed that the results matched those of conventional laser. The study was performed with YAG green laser, a less intensive treatment modality, and produced notable results. "Light" differed from "classic" photocoagulation in that the energy employed was the lowest capable to produce barely visible burns at the level of the RPE. 3 In this prospective, randomized, pilot clinical trial, 29 eyes of 24 dia- betic patients with mild to moderate non-proliferative diabetic retinop- athy and clinically significant mac- ular edema were randomized to re- ceive either classic photocoagulation or light Nd:YAG 532 nm (frequency doubled) green laser. A compari- son of reduction or elimination of DME, visual loss, change in contrast sensitivity, and mean deviation in the central 10 degrees showed no statistical difference between the groups at 12 months (p>0.05). "Laser irradiation can still exert some biological effects in the absence of a visible endpoint. Dif- ferent laser technologies have been proposed to perform subthreshold photocoagulation. The ones that are most commonly used are continu- ous wave laser (CWLP) that reduces pulse duration and the energy of laser irradiation and micropulse laser (MLP)." To obtain a sub-visible retinal irradiation, the surgeon must aim to attain therapeutic effects with the use of smaller retinal irradiances and lower retinal temperature rises, limiting retinal damage. Lasers used in this fashion include CWLP, which performs continuous wave laser pho- tocoagulation using a 10–20 msec, single pulse pattern. MLP refers to micropulse laser photocoagulation using 0.2 msec repetitive pulses. SRT is selective retinal therapy with 1.7 microsec repetitive pulses, and 2RT is retinal regeneration therapy using 3 nsec single pulses, Dr. Sarao explained. In a study conducted at the University of Udine, Dr. Sarao and her team used a continuous wave yellow laser with endpoint manage- ment technology in 17 eyes and a micropulse strategy (subthreshold laser) in 11 eyes of patients with DME. The aim of the study was to find an alternative endpoint using multi-modal imaging and compare the immediate and short-term tissue effects of different subthreshold laser treatment modalities for DME. The investigators used the Pascal Synthe- sis 577 nm (Topcon Medical Systems, Oakland, New Jersey) with endpoint management and the Iridex IQ 577 nm (Mountain View, California) with micropulse technology. "The study showed that in a large proportion of cases, laser spots were not detectable with either of the subthreshold laser technologies. Results Spot detection by different imaging techniques µP laser group=11 eyes EpM laser group=17 eyes Spot detection by different imaging techniques

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