JUN 05, 2009
Researchers retrospectively compared refraction after cataract surgery in 25 patients (27 eyes) who had previously undergone trabeculectomy with 49 controls (patients with glaucoma or glaucoma suspects, but no trabeculectomy history) who underwent cataract surgery. The difference between mean final and predicted refraction was similar in the study and control groups (-0.852 vs.-0.501 D). Lower IOP before cataract surgery correlated weakly with a postsurgical myopic shift.
While these results are unsurprising, this study does provide a good review of potential errors that could affect refractive outcome in cataract extraction after trabeculectomy, such as changes in corneal curvature, anterior chamber depth and IOP, and possible error in measuring the axial length (AL) with A-scan ultrasonography due to the potential deformation of the eye with the probe after trabeculectomy resulting in falsely low readings.
The authors recommend special attention be given to measuring AL with contact methods after trabeculectomy when the IOP is low, as it may result in indentation of the cornea and falsely lower readings. The use of noncontact methods, such as the laser interferometer (IOL master), should be considered in these cases.
Dr.Crandall is a consultant to Alcon Laboratories, Inc, and iScience Interventional. He receives lecture fees from Advanced Medical Optics, Allergan, Inc., Pfizer Ophthalmics, iScience Interventional and Ocular Surgery News