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PURPOSE To evaluate the effect of ultraviolet A radiation on retinal function and structure after the corneal collagen crosslinking procedure. METHODS In the present prospective, single-center cohort study 17 eyes of 17 patients who underwent collagen crosslinking (Dresden protocol) for the treatment of corneal ectasia were examined preoperatively and at 2 and 6 weeks postoperatively with multifocal electroretinogram and optical coherence tomography. The P1 amplitude density (P1-AD) of the central retinal response was documented in 5 concentric rings, with ring 1 (R1) representing the foveal response and rings 2 to 5 (R2-R5) corresponding to successive annuli of stimulation. Visual acuity, corneal densitometry at the 0 to 2 mm zone and at the 2 to 6 mm annulus, and macular thickness (MT; central, 1 mm, 3 mm, and 5 mm zones) were recorded. RESULTS The preoperative values of P1-AD were R1 = 109.96 ± 28.96, R2 = 49.8 ± 14.46, R3 = 29.85 ± 8.9, R4 = 19.33 ± 6.3, and R5 = 16.39 ± 5.48 nV/deg. At 2 weeks, these values were R1 = 77.54 ± 24.47, R2 = 36.55 ± 12.53, R3 = 21.53 ± 7.71, R4 = 15.3 ± 6.13, and R5 = 13.32 ± 5.48, showing a significant reduction for R1-R4 (P ≤ 0.026). The 6-week P1-AD was R1 = 99.8 ± 31.23, R2 = 40.67 ± 16.39, R3 = 24.98 ± 7.13, R4 = 16.35 ± 4.84, and R5 = 13.76 ± 3.98, showing no significant differences compared with preoperative values (P ≥ 0.054). Corneal densitometry increased significantly at 2 weeks (P < 0.001) and remained increased at 6 weeks (P < 0.001), showing statistically insignificant correlations with 2-week P1-AD (P ≥ 0.553). The central MT increased (P = 0.787), whereas MT at 1 mm (P = 0.444), 3 mm (P = 0.039), and 5 mm (P < 0.001) zones decreased. CONCLUSIONS The return of P1-AD to preoperative (physiologic) values at 6 weeks confirms the safety standards of the duration and intensity of ultraviolet A radiation, as proposed by the Dresden protocol. However, temporary postoperative retinal dysfunction cannot be excluded.

PURPOSE To compare the rebubbling rate and clinical outcomes of Descemet membrane endothelial keratoplasty (DMEK) with 5% sulfur hexafluoride (SF6) gas versus 100% air as a tamponade for graft attachment. METHODS Retrospective, comparative, interventional case series including 368 consecutive pseudophakic eyes with Fuchs endothelial dystrophy or pseudophakic bullous keratopathy that underwent DMEK in a tertiary referral center between October 2010 and August 2015 using either air (group 1, 191 eyes) or 5% SF6 (group 2, 177 eyes) as a tamponade. The rebubbling rate, complications, best-corrected distance visual acuity (BCVA), manifest refraction, and endothelial cell density were analyzed before and at 1 week, 1, 3, 6, 12, 24, and 36 months after surgery. RESULTS The rebubbling rate was 20.4% (39/191, group 1) versus 6.8% (12/177, group 2; P < 0.001). Complications included cystoid macular edema (n = 5, group 1, and n = 10, group 2; P = 0.14) and 1 case of presumed allograft rejection (n = 1, group 2). The follow-up period was 12 ± 8 months for group 1 and 6 ± 4 months for group 2. BCVA (logarithm of the minimum angle of resolution) had improved after 12 months from 1.43 ± 0.63 to 0.18 ± 0.26 (group 1, P < 0.001) and from 1.8 ± 0.63 to 0.18 ± 0.17 (group 2, P < 0.001). The percentage of eyes with BCVA ≥0.2 logarithm of the minimum angle of resolution at 12 months was 70.9% (90/127, group 1) and 78.4% (40/51, group 2; P = 0.3). Endothelial cell loss at 12 months after DMEK was 44 ± 18% (group 1) versus 33 ± 15% (group 2, P = 0.07). CONCLUSIONS The use of a tamponade with 5% SF6 yielded a significantly lower incidence of graft detachment requiring surgical reintervention with no detrimental effect on graft endothelial cells. Thus, routine use of 5% SF6 for a graft tamponade in DMEK is recommended.