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Catherine Baril, Lesya Shuba, Paul E Rafuse, Jayme R Vianna, Balwantray C Chauhan, Marcelo T Nicolela; Rates of Visual Field Change after Trabeculectomy. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):2721. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
Several recent retrospective studies have evaluated the effect of trabeculectomy on rates of visual field progression before and after surgery. These studies, however, are difficult to interpret as the decision to operate can be triggered by a variety of factors, including a poor visual field test which can cause a regression to the mean and an apparently slower rate of change post-trabeculectomy. We focused on the rate of visual field progression post-trabeculectomy by pairwise matching patients by Mean Deviation (MD) to those who were medically treated.
The medical records of all patients who underwent trabeculectomy with mitomycin C by one of two glaucoma specialists (MTN, LMS) were reviewed. We selected patients with ≥ 5 SITA Standard 24-2 visual fields post-trabeculectomy. Eyes with subsequent glaucoma surgery during the follow-up period were excluded. If both eyes were eligible, only one eye was randomly selected. The rate of MD change was calculated for each patient with robust regression with the first post-trabeculectomy field defined as baseline. These patients were then matched by baseline MD with patients treated only medically and followed with ≥5 visual field tests.
There were 94 patients with median (IQR) age at surgery of 67 (61, 75) years and 8 (6, 9) visual field tests over 5.6 (4.0, 6.8) years post-trabeculectomy. The 94 medically treated matched patients had median age of 69 (61, 77) years and 7 (5, 11) visual field tests over 5.7 (3.9, 9.6) years. The unsigned pairwise difference in baseline median (IQR) MD in the surgically and medically treated groups was 0.01 (0.00, 0.02) dB with a baseline MD of -7.00 (-11.04, -4.30) dB in the surgical group. The median MD slopes were comparable (p = 0.13) between the groups: -0.15 (-0.51, 0.06) dB/y in the surgically treated patients, and -0.07 (-0.42, 0.24) dB/y in the paired medically treated controls.
Our findings suggest that most patients who undergo trabeculectomy with mitomycin C have relatively slow rates of visual field progression post-operatively. Presumably patients who were treated surgically had a higher risk profile or more progressive disease prior to surgery, but their post-trabeculectomy rate of progression was similar to the rate observed in patients with comparable disease severity who were medically treated.
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