Difficulty in inserting 25-and 23-gauge trocar cannula during vitrectomy

Purpose: To determine the incidence of difficulty in inserting a 25-and 23-gauge trocar cannula (DITC) during 25-or 23-gauge micro-incision vitrectomy surgery (MIVS). Methods: Retrospective, consecutive, interventional case series performed by a single surgeon at a single centre. We defined a DITC as the condition where at least 1 trocar cannula could not be inserted into the vitreous at the beginning of MIVS. The incidence of DITC was calculated from 1,525 eyes, and the pre-operative demographics of the DITC cases were compared to those of the non-DITC cases. Results: The incidence of DITC for all cases was 0.6% (9 of 1,525 eyes). Overall, there were 242 eyes with a retinal detachment (RD), and 8 of the 9 eyes with DITC had an RD with an incidence of 3.3% (8 of 242 RD eyes). Seven of these 8 eyes had a total RD, 4 also had a choroidal detachment, 4 eyes were also myopic (>-8.0 dpt, high myopia), and 6 of the 8 eyes were hypotonic (<8 mm Hg). The DITC cases had larger RDs (p < 0.0001), a higher incidence of choroidal detachment (p < 0.0001), higher myopia (p = 0.0204) and hypotony (p = 0.0003) than the non-DITC eyes with an RD. Conclusions: A large RD, a choroidal detachment, high myopia and hypotony are significant risk factors for DITC. We recommend that MIVS should be performed cautiously for eyes with these risk factors.