The capsular bag contracts when we remove the thick cataract (4+ mm thick) and replace it with a thin IOL (1 mm thin). This is normal in all eyes and limited since the strong zonular attachments provide a counterforce to balance the contraction. But what happens when the zonular structures are weak and we have a small capsulorhexis which is more prone to contraction? We can get capsular phimosis, also known as Anterior Capsule Contraction Syndrome. While mild capsular phimosis has little effect on the visual acuity, when it progresses it can result in severe capsular contraction, zonular loss, and distortion and dislocation of the IOL. How can we prevent and treat capsular phimosis?
The risk factors for capsular phimosis include:
- conditions associated with loose zonules
- pseudo-exfoliation syndrome
- retinitis pigmentosa
- uveitis and chronic intra-ocular inflammation
- making a small capsulorhexis of 4 mm in diameter or less
- remember, don’t make a baby rhexis!
- some highly myopic patients
- retained lens material / proliferation of lens epithelial cells
What is the best treatment? Capsular phimosis happens usually within a few months of the initial cataract surgery, but is also noted to happen a few years later. Patients who have evidence of anterior capsular phimosis and contraction of the capsulorhexis should have a YAG laser capsulotomy performed to break the phimotic ring and prevent further issues. Usually one treatment to break the continuity of the contracted capsulorhexis is enough to achieve long-term stability.
In some cases, if the capsular phimosis is severe, it can lead to loss of zonular support and distortion and dislocation of the IOL. This now requires an IOL exchange with a sutured-in lens or an anterior chamber IOL.
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