Investigations into localized re-treatment of the retina with a 3-nanosecond laser.
Subvisual retinal lasers necessarily cause clinically invisible lesions, hence, they could intentionally or inadvertently be targeted at precisely the same or an overlapping location during repeat laser treatment. Herein, we investigated the structural integrity and cellular responses of localized re-treatment using a nanosecond laser (2RT) currently in trials for early age-related macular degeneration.



Rats were randomly assigned to one of five groups: sham, subvisual 2RT, subvisual 2RT re-treatment, visual effect 2RT, visual effect 2RT re-treatment. Re-treatment groups were lasered on days 0 and 21; single laser groups were only lasered on day 21. All rats were euthanized at day 28 and eyes were then dissected and processed for immunohistochemistry. For re-treatment, the laser was targeted at precisely the same locations on both delivery occasions. Analytical endpoints included monitoring of retinal vascular integrity overlying lesions, investigation into any potential choroidal neovascularization, assessment of the RPE, quantification of collateral injury to photoreceptors or other neuronal classes, and delineation of glial reactivity.



Repeat laser administration to rats caused ostensibly identical retinal-RPE-choroid responses to those obtained in age-matched rats that received only a single application. Specifically, 7 days after treatment, RPE cells were re-populating lesion sites. No obvious consistent differences were evident between the single and repeat laser groups. Moreover, repeat laser caused no (measurable) additive injury to photoreceptors or other retinal neuronal classes from single laser treatment. In re-lasered animals, there was no increase in microglial activity overlying and adjacent to lesion sites relative to single lasered rats. Finally, there was no evidence of choroidal neovascularization after repeat laser treatment.



The overall results provide a measure of confidence that re-treatment of patients with 2RT should not provide any additional risk of developing visual scotomas, choroidal neovascularizations, or inflammatory events. Indeed, the collated results indicate that the metabolic and structural disruption to the RPE-retina caused by short pulse duration laser treatment is resolved within a short time frame such that re-treatment elicits a phenotype indistinguishable from single treatment. Lasers Surg. Med. 48:602-615, 2016. © 2016 Wiley Periodicals, Inc.
Ophthalmic Research Laboratories, Hanson Institute Centre for Neurological Diseases, Frome Rd, Adelaide, SA 5000, Australia.|Discipline of Ophthalmology and Visual Sciences, University of Adelaide, Frome Rd, Adelaide, SA 5005, Australia.
Glyn
G
Chidlow
Ophthalmic Research Laboratories, Hanson Institute Centre for Neurological Diseases, Frome Rd, Adelaide, SA 5000, Australia.
Malcolm
M
Plunkett
Ophthalmic Research Laboratories, Hanson Institute Centre for Neurological Diseases, Frome Rd, Adelaide, SA 5000, Australia.|Discipline of Ophthalmology and Visual Sciences, University of Adelaide, Frome Rd, Adelaide, SA 5005, Australia.
Robert J
RJ
Casson
Ophthalmic Research Laboratories, Hanson Institute Centre for Neurological Diseases, Frome Rd, Adelaide, SA 5000, Australia.|Discipline of Ophthalmology and Visual Sciences, University of Adelaide, Frome Rd, Adelaide, SA 5005, Australia.
John P M
JP
Wood
D000818:Animals; D020256:Choroidal Neovascularization / Q000175:diagnosis / Q000209:etiology / Q000473:pathology; D017075:Laser Coagulation / Q000009:adverse effects* / Q000295:instrumentation / Q000379:methods; D053844:Lasers, Solid-State / Q000009:adverse effects*; D008268:Macular Degeneration / Q000473:pathology / Q000601:surgery*; D011183:Postoperative Complications / Q000175:diagnosis / Q000209:etiology / Q000473:pathology; D011897:Random Allocation; D051381:Rats; D012086:Reoperation / Q000009:adverse effects* / Q000295:instrumentation / Q000379:methods; D012160:Retina / Q000473:pathology* / Q000601:surgery*
age-related macular degeneration; inner retinal neurons; nanosecond laser; photoreceptors; re-treatment; retina; retinal pigment epithelium