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Consultation section

refractive surgical problem

Mietz, Holger MD

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Journal of Cataract & Refractive Surgery: March 2004 - Volume 30 - Issue 3 - p 538-539
doi: 10.1016/j.jcrs.2004.02.008
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▪ In this challenging case, there are 2 reasons for the patient's complicated glaucoma: He is black and he has uveitis. Therefore, one can anticipate that controlling the glaucoma will be difficult. The patient has a history of 2 trabeculectomies with MMC. No information on the exact concentration and location of the first trabeculectomy and MMC application is given. This information might be important. The second application of MMC was excessive, with a high concentration (0.5 mg/mL) and 2 areas of application.

The current problem is not the IOP but rather increasing astigmatism in this eye. First we must determine whether this is a corneal or scleral problem. We have Orbscan results from the right eye but not the left eye. It would be helpful to know whether there is a hint of corneal thinning or irregularity in the peripheral cornea, likely adjacent to the first or second trabeculectomy site.

A second consideration is IOP. When the eye becomes soft, corneal irregularity may develop and will subside once IOP returns to within normal limits. We are told central corneal thickness is normal and the patient uses a topical β-blocker, so I would rule this out.

The main cause of the increased astigmatism is probably scleral. Given the plus astigmatism at the 65-degree axis or at the 155-degree axis (minus astigmatism), we can assume there is increased traction at the 65-degree axis (superotemporally) or instability of the sclera at the 155-degree axis (superonasally). Increased traction superotemporally seems unlikely because releasable sutures were used; however, there is no information on what happened to them. These sutures have probably not been tightened recently. This leaves the possibility of a scleral melt superonasally related to the first trabeculectomy with MMC. Scleral melts, especially those occuring several years after the use of MMC, have been reported in the literature. I would like to obtain more information on this issue. Perhaps the most useful examination would be ultrasound biomicroscopy. Recently, the use of an anterior segment optical coherence tomography was described. Both methods demonstrate irregularities of the sclera, which are most likely close to the limbus.

If these examinations show a pathologic situation, I would recommend surgical exploration of the first filtering bleb coming from the limbus. I would make sure to have a scleral patch on hand.

© 2004 by Lippincott Williams & Wilkins, Inc.