Cannula DALK versus needle DALK for keratoconus

Purpose: To evaluate outcomes and possible advantages of 2 different techniques of deep anterior lamellar keratoplasty (DALK) in patients with keratoconus: cannula big-bubble DALK and needle big-bubble DALK (Anwar technique). Methods: This is a retrospective, nonconsecutive, comparative study of 507 eyes affected by keratoconus that underwent DALK between 2002 and 2012. Needle DALK and cannula DALK techniques were performed in 266 eyes and 241 eyes, respectively. When big bubble (BB) failed, air viscobubble (AVB) was used as a rescue bubble technique. When AVB failed, manual dissection was performed. Main outcomes analyzed were the frequency of descemetic deep anterior lamellar keratoplasty (dDALK) and predescemetic deep anterior lamellar keratoplasty (pdDALK), BB and AVB formation, Descemet membrane rupture, and penetrating keratoplasty conversion. Results: The rate of dDALK achieved was higher (P < 0.01) in the cannula DALK group (94%; 198 BB and 28 AVB) than in the needle group (78%; 161 BB and 46 AVB). The remainder of cases involved pdDALK: 59 cases (22%) and 15 cases (6%) of the needle DALK group and cannula DALK group, respectively. Microperforation occurred in 18 cases spread between both groups. Macroperforation occurred in 5 cases in the needle DALK group. A double chamber occurred in seven cases, between both groups. No penetrating keratoplasty conversion was needed. Conclusions: The use of a smooth cannula during the DALK procedure yields a statistically higher percentage of dDALK and makes the maneuver more manageable compared with air injection with a needle. When BB fails, AVB seems to be a good rescue technique to achieve dDALK