evaluation of parameters influencing bare descemet membrane achievement during deep anterior lamellar keratoplasty in keratoconus

purpose: to assess parameters that had a capability of influencing the rate of big bubble formation during deep anterior lamellar keratoplasty (dalk) in keratoconus. methods: a total of 290 consecutive eyes from 257 patients with keratoconus that underwent dalk using the big-bubble technique were enrolled. the influence of patient age and sex, family history of keratoconus, history of contact lens wear or vernal keratoconjunctivitis, the presence of vogt’s striae or superficial opacities, keratometric readings, central and peripheral corneal thickness, anterior chamber depth, vitreous length, and trephination size on the rate of a bare dm achievement was investigated. results: dalk was performed in 289 of 290 eyes and a bare dm was successfully achieved in 229 (79.2%) eyes. the recipient sex and trephination size had a significant association with the success rate of big-bubble formation. the female sex decreased the odds of bare dm achievement by 0.44 times (p=0.02). for each 0.1-mm increase in the trephination size, the odds of the successful big-bubble formation increased by 1.36 times (p=0.03). other factors failed to demonstrate any significant association with the rate of successful bare dm achievement. conclusion: the rate of successful big-bubble formation was 79.2% in keratoconus. among different factors, female sex predicted a less likelihood of big bubble formation while large trephination size was significantly associated with an increase in the chance of bare dm achievement.