Advances in Cataract Surgery

Majed Alkharashi; Walter J Stark; Yassine J Daoud


Expert Rev Ophthalmol. 2013;8(5):447-456. 

In This Article

Zonules-Supporting Devices

The anterior approach of removing a cataract with significant zonular weakness used to be ICCE until endocapsular devices were introduced in 1991.[52,53] The capsular tension ring (CTR) is made of polymethyl-methacrylate (PMMA) material and has an oval-shaped cross section with eyelets at both free ends. The diameter of CTR is larger than that of the capsular bag and comes in different sizes. The CTR expands the capsular bag and redistributes the forces, providing equal distribution of support over the remaining zonules.[54] At minimum, overlap of the end terminals is needed to provide complete circumferential support. CTR is indicated when there is evidence of severe, but localized zonular dialysis (<4 h) or mild degree of generalized zonular weakness.[54] The CTR can be inserted manually with forceps or with injectors into the capsule bag before or after lens extraction.

The CTR has intra- as well as post-operative advantages. By expanding the bag, it reduces the risk of further zonular damage. Also, it minimizes the risk of potentially aspirating the bag during the surgery. Post-operatively, CTR reduces the risk of IOL decentration and tilting.[55] It offers the advantage of preventing capsule wrinkling and facilitate recentering a mildly subluxed capsular bag. Further, it may decrease the prevalence of posterior capsule opacification or the incidence of capsular phimosis.[56]

When there is a profound zonular insufficiency and a severely subluxed capsular bag, a standard CTR may not supply enough intraoperative and postoperative support to maintain the desired orientation of the capsular bag. To deal with these problems, scleral-fixated devices such as the modified CTR (M-CTR) or the capsular tension segment (CTS) must be used.[57] Iris chafing from the fixation eyelet and chronic uveitis could occur with small capsulorhexis, thus an adequate size capsulorhexis (5.5 mm) should be performed.[54]