Impact of stromal deposit depth on pneumatic dissection during Dalk for Tgfbi corneal dystrophies

Objectives: To evaluate whether preoperative anterior segment optical coherence tomography (AS-OCT) parameters differ according to Big Bubble (BB) formation during deep anterior lamellar keratoplasty (DALK) in patients with TGFBI-related corneal stromal dystrophies (CSD). Methods: This retrospective cohort study included 17 eyes from 12 patients undergoing DALK with an attempted BB technique. Stromal deposit depth was assessed by AS-OCT using both a categorical depth-based classification (anterior, mid-, and posterior stroma) and continuous measurements of stromal involvement (µm). The ratio between stromal involvement and the thinnest corneal point was calculated. Intraoperative data included BB success, BB type, and complications. Inter-eye correlation was accounted for in comparisons of continuous variables using linear mixed-effects models. Results: BB formation was achieved in 11 of 17 eyes (64.7%), with type 1 BB observed in all successful cases. BB success was observed in all eyes with anterior or mid-stromal involvement and in 33.3% of eyes with posterior stromal involvement. Greater stromal deposit depth and a higher stromal-depth-to-thinnest-point ratio were observed in eyes in which BB formation failed (p < 0.01). No intraoperative perforations or conversions to penetrating keratoplasty occurred. Inter-observer agreement for AS-OCT measurements was high. Conclusions: BB failure was more frequent in eyes with greater absolute and relative stromal deposit depth, as assessed by preoperative AS-OCT during DALK in TGFBI-related CSD. These AS-OCT-derived parameters may support surgical planning and improve patient selection for BB DALK in this clinical setting.