Factors Affecting Formation of Type-1 and Type-2 Big Bubble during Deep Anterior Lamellar Keratoplasty.

Purpose: To determine the factors associated with the formation of different types of big bubble (BB) during DALK. Methods: In this retrospective study, 322 consecutive eyes of 307 patients with corneal stromal disorders who underwent DALK between January 2014 and June 2017 were included. Age, sex, corneal pathology, visual acuity, corneal curvature, corneal thickness, and adverse events were recorded. The main outcome measure was the success of BB formation with respect to the corneal pathology. Results: Type-1 BB was achieved in 147 eyes (45.7%), whereas type-2 BB was formed in 109 eyes (33.9%). The overall success rate of BB formation was 82.9%. Type-1 BB formation in keratoconus patients was significantly higher than type-2 BB (83.8% vs 2.6%, p < 0.001). In contrast, type-2 BB formation was significantly higher than type-1 BB (61.0% vs 15.6%, p < 0.001) in patients with corneal scars. Type-1 BB was more likely to be seen in patients with superficial corneal scarring, granular, and lattice dystrophies, while corneas with deep scarring and macular dystrophy had more type-2 BB. The type of bubble was not associated with age and gender of the patients. Conclusions: The overall success of big-bubble (BB) deep anterior lamellar keratoplasty (DALK) depends on the preoperative corneal pathology. Type -1 BB was more commonly seen in keratoconus patients whereas type-2 BB was observed in patients with deep corneal scars and other corneal pathologies affecting deeper layers of corneal stroma.