Experimental investigation of retinal injury following endocryocoagulation in a rabbit model

The aim of this study is to evaluate the effects of varying endocryocoagulation parameters on retinal function and histological integrity in a rabbit model and to assess the feasibility of intraocular foreign body (IOFB) removal using a 20G cryoprobe. Twenty-seven adult New Zealand white rabbits were randomly assigned to three experimental groups (n = 9 per group). Endocryocoagulation was administered with a 20G cryoprobe under different conditions: Group An underwent vitreous cavity freezing for 5 s; Group B underwent retinal surface freezing for 5 s; and Group C underwent vitreous cavity freezing for 10 s. Flash electroretinography (F-ERG) was conducted preoperatively and at 1, 2, and 3 weeks postoperatively. Hematoxylin and eosin staining for light microscopy (LM) was performed at 1 and 3 weeks postoperatively, and transmission electron microscopy (TEM) was conducted at 3 weeks. F-ERG measurements indicated significant differences among the three groups in the latency (Group A vs. B: p = 0.011; Group A vs. C: p = 0.008) and amplitude (Group A vs. B: p = 0.007) of the dark-adapted b-wave, and the total amplitude of dark-adapted OPs (Group A vs. B: p = 0.001; Group A vs. C: p = 0.002). No significant differences were observed in the latency or amplitude of the dark-adapted a-wave (p > 0.05). Comparison of preoperative and 1-week postoperative F-ERG results indicated significant changes in the latency and amplitude of both a- and b-waves, as well as in the total amplitude of OPs (p < 0.05, p(a) = 0.007, p(b) = 0.022, p(ops) = 0.000). LM findings at 1 week postoperatively demonstrated full-thickness retinal damage in Group B, moderate damage in Group A, and red-stained exudates in the vitreous body in Group C. By 3 weeks, varying degrees of recovery were noted across all groups, with Group A exhibiting near-complete restoration of normal retinal architecture. TEM analysis at 3 weeks demonstrated the least ultrastructural damage in Group A, followed by Group C, while Group B presented with the most severe damage.The extent of retinal injury resulting from endocryocoagulation was associated with the freezing duration and site of application. Short-duration cryocoagulation targeting the vitreous cavity exerted minimal impact on visual function. The use of a 20G intraocular cryoprobe for IOFB removal was supported as a feasible approach.