Evaluation of Intraocular Lens Decentration with Scheimpflug Imaging

Modern cataract surgery is the one of the commonly surgery in this era, it small wound size cause little astigmatism after surgery, but the decentration of intraocular lens (IOL) also can impair the visual outcomes, so the position of the IOL has become the most important issue in ophthalmology. This study try to quantify the IOL position with scheimpflug imaging and try to find the factor that cause the IOL decentration and tilt after surgery. The influence of IOL decentration and tilt on visual outcomes also discuss in this paper.
We enrolled 30 eyes of 30 patients who underwent cataract surgery with IOL insertion and 23 eyes of 13 patients has crystalline lens at Far Eastern Memorial Hospital in this study. The patients averaged were 67±10, 53±23 years old respectively. All of the patients provided informed consent before this study. Corneal curvatures were measured by Topcon KR 8900 auto-refractor and capture the anterior segment image by Pentacam HR. Each eye has 25 scheimpflug image and the quality of image have to over than 95% valid data of cornea. The code written by Matlab use to measure the position of the lens. Lenticualr astigmatism was calculated by Alpin’s vector analysis method. Correlations were analyzed between IOL decentration, IOL tilt, age, axial length, BCVA, lenticular astigmatism.
The mean decentration of IOL group is 0.20±0.07 (0.08 to 0.33)mm, mean tilt of IOL group is 2.24±0.93 (0.65 to 3.93)degree, mean lenticular astigmatism of IOL group is -0.50±0.34 (0 to -1.33)D. The mean decentration of crystalline lens group is 0.081±0.034 (0.032 to 0.17)mm, mean tilt of crystalline lens group is 1.76±0.49 (0.08 to 3.08), mean lenticular astigmatism of crystalline lens group is -1.00±0.50 (0 to -1.78)D. The correlation between IOL decentration and patient’s age was significant (r=0.552, p=0.002), but there was no correlation between IOL tilt and patient’s age(r=0.033, p=0.863). The correlation between axial length and patient’s age was significant (r=-0.515, p=0.008), but there was no correlation between axial length and IOL tilt (r=0.066, p=0.758) and decentration (r=0.122, p=0.570). The correlation between IOL decentration and the BCVA and lenticular astigmatism was not significant (p>0.05), nor was the correlation between IOL tilt and BCVA and lenticular astigmatism (p>0.05).
The aging process may play an important role in IOL decentration. Major changes that occur in the lens with age, such as changes in the lens thickness, weakening of the zonular and capsular bag also cause the IOL decentration to increase with age. The tools used to quantify the IOL position present by this research and Pentacam HR can measure the IOL position easily and quickly, and hope the IOL position can be an important parameters to help the doctor in clinically.