Changes in Endothelial Cell Count Up to Three Years After Implantation of Toric Implantable Collamer Lenses

Purpose: To determine the temporal effect of toric implantable collamer lens (TICL) implantation and location on corneal endothelial cell density (ECD) over a period of 36 months after surgery. Methods: ECD [number of cells per square millimeter estimated using the Specular Microscope SP-1P (Topcon Europe Medical B. V., Netherlands)] data were collected from cases deemed suitable for the TICL (VTICMO, VTICM5; STAAR Surgical, Nidau, Switzerland). The preoperative refractive error (sphere and cylinder) ranged from -1.00 to -22.25 diopter sphere and from 20.50 to -5.50 diopter cylinder. ECD was evaluated at preoperative and all postoperative sessions. Results: Key findings were as follows: the mean ECD (6SD, 95% confidence interval) was 2720 cells/mm(2) (6272, 2620-2820 cells/mm(2)) preoperatively, which was reduced to 2372 cells/mm(2) (+/-325, 2250-2490 cells/mm(2)) at 36 months postoperatively (P, 0.001). Linear regression revealed the following significant correlations between the (1) log of the change in ECD (y(1)) and log of preoperative ECD (x(1)) at 2 years postoperatively, y(1) =2.513x(1)-6.2816 (n=62, r=0.3503, P =0.005); (2) mean ECD (y(2)) and log time (in months, x(2)), y(2)=2543.7-36.997x(2)-38.99x(2) 2 (r=20.9654, n =7, P = 0.0004); and (3) mean axial distance between the front surface of the crystalline lens and the TICL back surface (y3) and time postoperatively (in months, x(3)), y(3) =0.1035x3 225.2808x(3) + 473.18 (r =0.8512, n =7, P =0.015). Conclusions: Expected ECD loss after TICL implantation by 2 years postoperatively is predictable. On average, over 3 years after implantation, there is (1) an initial rapid decline in ECD, followed by a gradual fall in the rate of cell loss, and (2) a gradual fall in the distance between the TICL and the crystalline lens by 2 years postoperatively, followed by a reversal by the third year.