SCIENTIFIC REPORT

The effects of indocyanine green and endoillumination on rabbit retina: an electroretinographic and histological study

A K H Kwok^1,2, T Y Y Lai¹, C-K Yeung¹, Y-S Yeung¹, W W Y Li¹ and S W Chiang¹

¹ Department of Ophthalmology and Visual Sciences, The Chinese University of Hong Kong, Hong Kong Eye Hospital, Hong Kong, People’s Republic of China
² Department of Ophthalmology, Hong Kong Sanatorium and Hospital, Hong Kong, People’s Republic of China

Correspondence to:
Correspondence to:
Dr Timothy Y Y Lai
Department of Ophthalmology and Visual Sciences, The Chinese University of Hong Kong, Hong Kong Eye Hospital, 147K Argyle Street, Kowloon, Hong Kong; tyylai{at}netvigator.com

Aim: To evaluate the functional and morphological retinal toxicity associated with intravitreal injection of indocyanine green (ICG) dye in rabbit eyes during vitrectomy with endoillumination.

Methods: 20 eyes of 10 New Zealand pigmented rabbits were used in the study. All eyes underwent pars plana vitrectomy and removal of posterior vitreous cortex under endoillumination. In one eye of each rabbit, intravitreal injection of 0.1 ml of 2.5 mg/ml ICG was applied for 30 seconds followed by 10 minutes of endoillumination. The control eye had endoillumination only without ICG injection. Dark adapted and light adapted electroretinograms (ERGs) were performed before the surgery and 1 week after surgery for serial comparisons. Rabbits were killed 1 week after surgery and eyes were enucleated for histological examination.

Results: Serial ERG comparisons showed significant reduction in the light adapted a-wave amplitude (p = 0.037) and significant delays in the dark adapted and light adapted b-wave latencies (p = 0.020 and p = 0.038, respectively) in the ICG treated eyes. Histological examinations demonstrated loss of photoreceptor outer segments with focal absence of photoreceptors in some areas in the ICG injected eyes.

Conclusions: Vitrectomy followed by intravitreal injection of 2.5 mg/ml ICG for 30 seconds with endoillumination may result in retinal toxicity causing functional and morphological retinal damages in rabbit eyes. The lowest concentration of ICG should be used if necessary for intraocular use to prevent potential retinal toxicity.

Abbreviations: ERG, electroretinogram; ICG, indocyanine green; ILM, internal limiting membrane; RPE, retinal pigment epithelium

Keywords: indocyanine green; rabbit; retina; electroretinography; histology

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