Abstract
Purpose :
Choroideremia (CHM) is a disorder affecting the retinal pigment epithelium (RPE), photoreceptors (PR), and the outermost vascular layer, choroid (more specifically the choriocapillaris CC) [1]. OCTA technology uses laser light reflectance of the surface of moving red blood cells to depict vessels through different segmented areas of the eye, allowing non-invasive detailed imaging of the retina microvasculature that is not possible with conventional angiography [2]. We recently showed that micropulse laser of 1% and 3% duty cycle (DC) damages the RPE of Yucatan minipigs [3]. Here we extend this work to evaluate the effect of micropulse laser on pig CC and larger choroidal vessels using OCTA with conventional angiography, to develop an induced choroidal degeneration (choroideremia) pig model
Methods :
A micropulse laser of 532 nm with 330 msec pulses was used with different DC (1, 1.5, 2, and 3%) in 8 eyes of Yucatan minipigs. Animals were evaluated every week for up to 12 weeks with Optical Coherence Tomography OCT, OCTA and conventional angiography (fluorescein angiography FA and indocyanine green-angiography ICGA)
Results :
Data acquired with the different techniques are consistent and show that CC degeneration is visible 7 days post laser treatment for all DC, and the severity of degeneration is directly proportional to the laser power. The CC appear to progressively recover from the edges of the lesion for lower DC laser (1, 1.5, and 2%), leading to almost complete recovery in 1% DC in 12 weeks. Laser power of 1 and 1.5% DC leaves INL intact and ONL partially preserved; 2% DC laser more severely damaged the ONL, and mildly the INL; 3% DC leads to complete degeneration of ONL and INL. Our results indicate that lower power laser (1, 1.5, and 2% DC) induces CC and PR degeneration likely as a secondary effect of RPE loss. In comparison, higher power laser (3% DC) severely damages retinal and choroid structure causing complete CC, RPE, ONL, and INL loss
Conclusions :
Our data suggest that laser power of 1.5% and 2% DC leads to RPE, PR, and CC damage in the Yucatan minipig retina comparable to late stage of CHM. The OCTA, combined with other imaging techniques (OCT, FA, and ICGA) allows for an accurate in vivo follow-up of the CC and the retinal layers and therefore a direct translation of the efficacy of potential therapy from the pig model to the patients
This is a 2021 ARVO Annual Meeting abstract.