Dear Editors

We read with interest the study from Moutray et al[1] that found Optical Coherence Tomography (OCT) measures are not robust markers for visual function. We have looked at 20 patients with wet age related macular degeneration (AMD) and compared visual function and OCT measures using the new generation of Fourier Domain 3D OCT. We also find no significant correlation between OCT measurements of central foveal thickness, maximum retinal thickness and distance LogMar acuity, near vision and contrast sensitivity. We believe that this data is relevant to the use of ranibizumab in the UK.

The licence for the use of ranibizumab (Lucentis) in the UK is for a loading phase of one injection per month for three consecutive months, followed by a maintenance phase in which patients should be monitored for visual acuity every month. If the patient experiences a loss of greater than 5 letters in visual acuity (EDTRS) or one Snellen line equivalent, ranibizumab should be administered.

The PrONTO[2] study however, used visual and OCT criteria to make retreatment decisions. Retreatment was carried out if there was a loss of 5 letters in conjunction with fluid in the macula as detected by OCT, or an increase in OCT central retinal thickness of at least 100 microns along with other non- OCT guided criteria. More than a quarter of the study participants did not lose 5 letters of vision but had an increase in OCT central retinal thickness of at least 100 microns. Results from this study still showed a comparable proportion of patients (35% vs 33%) gaining 15 letters or more compared to the MARINA[3] trial where monthly dosing was carried out regardless of vision or OCT findings.

These studies suggest that visual function alone does not relate to the presence or absence of intraretinal and/or subretinal fluid in a significant proportion of patients which may signify the recurrence of the CNV. We therefore believe that Moutray et al’s study adds weight to the argument that visual function and OCT measurements should jointly be considered as criteria for retreatment with ranibizumab in order to maintain the level of vision achieved after the loading phase.

References

1. Moutray T, Alarbi M, Mahon G, et al. Relationships between clinical measures of visual function, fluorescein angiographic and optical coherence tomography features in patients with subfoveal choroidal neovascularisation. British Journal of Ophthalmology 2008;92(3):361-364.
2. Fung AE, Lalwani GA, Rosenfeld PJ, et al. An optical coherence tomography-guided, variable dosing regimen with intravitreal ranibizumab (Lucentis) for neovascular age-related macular degeneration. American Journal of Ophthalmology 2007;143(4):566-583.
3. Rosenfeld PJ, Brown DM, Heier JS, et al. Ranibizumab for neovascular age-related macular degeneration. New England Journal of Medicine 2006;355(14):1419-1431.