Comparison of the tissue response of selective retina therapy with or without real-time feedback-controlled dosimetry

The purpose of this study is to evaluate the retinal tissue response upon selective retina therapy (SRT) with or without real-time feedback-controlled dosimetry (RFD) in rabbits.

Eighteen eyes of nine Chinchilla Bastard rabbits were treated by SRT with or without RFD (Q-switched Nd:YLF, wavelength 527 nm, pulse duration 1.7 μs). RFD operated by optoacoustic and reflectometric methods detects the microbubbles from retinal pigment epithelium (RPE) damage in real time. After SRT, light microscopy (LM) and scanning electron microscopy (SEM) were performed at 1 h, 1 day, 3 days, 7 days, and 1 month. The RPE-damaged area on SEM was measured by ImageJ 1 h after SRT.

Without RFD, the RPE-damaged area of 76 SRT-treated spots showed a strong positive correlation with ramping pulse energy (Pearson's correlation coefficient, 0.706; P < 0.001). With RFD, there was a weak positive correlation between the RPE-damaged area of 92 spots and ramping pulse energy (Pearson's correlation coefficient, 0.211; P = 0.044). The detection rate of RFD was 91.8% by evaluating 563 SRT spots. Histology revealed that SRT with RFD produced a selectively disrupted RPE monolayer while sparing the photoreceptor layer inner segment.

RFD can be useful to titrate the pulse energy of visually undetectable SRT treatment.