Resistance to Compression of the Capsular Tension Ring over Time

Abstract

Purpose: To evaluate the resistance to compression of commercially available capsular tension rings (CTRs) when submitted "in vitro" to a constant pressure over a period of time.Setting: Research Unit. CHU Albacete. University of Castilla La Mancha. Spain.Method: Four samples of 3 different CTR manufacturers were evaluated for resistance to compression over time while being exposed to a constant tension. The 13 millimetres CTRs were placed in a round rigid container with an 11 millimetres diameter and submerged in BSS at body temperature (37 degrees Celsius). CTRs were divided into two groups. Two samples of each model were introduced in the containers and removed and evaluated at 1 month, while the other two samples of each model were introduced in the containers and removed and evaluated at three months. Size and shape of the CTRs were measured at baseline, at 1 month and 3 months. Every measurement was repeated 3 times by two different observers. Results:The mean decrease in CTRs diameter of the 1 month compression group was 1, 5 millimetres. The mean decrease in CTRs diameter of the 3 month compression group was 1, 63 millimetres. The differences in diameter between baseline and 1 month, as well as baseline and 3 months were statistically significant. There was no statistical significance when comparing the final size between the 1 month and 3 months groups. Conclusion:All the commercially available CTRs studied have shown a decrease in diameter when exposed to a constant compression at body temperature. This could explain some of the published reports of capsular bag shrinkage or even dislocation of the entire IOL-CTR complex despite the implantation of a CTR.