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K. T. Chang, P. A. Keane, S. Joeres, F. M. Heussen, S. C. Ongchin, A. C. Walsh, S. R. Sadda; Analysis of a Putative Tachyphylaxis in Response to Treatment of Neovascular Age-Related Macular Degeneration With Intravitreal Ranibizumab. Invest. Ophthalmol. Vis. Sci. 2008;49(13):341.
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To determine the characteristics of patients with neovascular age-related macular degeneration (AMD) who show initial anatomic improvements on optical coherence tomography (OCT) in response to treatment with ranibizumab, but who subsequently regress toward their anatomic baseline.
49 consecutive patients, receiving intravitreal injections of ranibizumab for neovascular AMD had StratusOCT data available at baseline, and months 1,3, and 6 after beginning therapy. During follow-up, patients were re-treated at the discretion of the physician applying a OCT-guided protocol similar to that described in the PrONTO study. Raw exported StratusOCT images were analyzed using publicly available custom software (OCTOR). OCTOR allowed the graders to calculate the volume of neurosensory retina, subretinal fluid (SRF), subretinal tissue (SRT) and pigment epithelial detachment (PED) at baseline, month 1,3, and 6. Patients were divided into those that maintained a reduction in retinal volume over time, and those that regressed towards their baseline level. Baseline characteristics between the groups were compared.
41 patients (84%) showed a reduction in total retinal volume by 1 month after initial treatment with ranibizumab. Of the patients who initially responded, 16 (39%) showed continued reduction through to the final examination at month 6, while 25 patients (61%) had regressed towards baseline measurements between month 1 and month 6. The patients who continued to respond, received 3.69±1.25 injections of ranibizumab versus 2.88±1.30 injections for the patients who did not (P=0.0562). No statistically significant difference was found between the groups in terms of age (P=0.7608), baseline visual acuity (P=0.7533), baseline retinal volume (P=0.2901), or angiographic classification of CNV at baseline (P=0.170). Additional analysis with OCTOR software found no statistically significant difference between the groups in terms of baseline SRF volume (P=0.6018), SRT volume (P=0.2215), or PED volume (P=0.2244).
Preliminary results provide some evidence to suggest that patients who receive a greater number of retreatments with intravitreal ranibizumab, may obtain greater and sustained reductions in retinal volume. These observations may be consistent with the findings from the PIER study.
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