Level of vision, not gain in letters seen, marks success of AMD treatment

Oct 1 2012

By Sarah Guy, medwireNews Reporter

The number of patients with a particular level of vision may be a better mark of the success of treatment for neovascular age-related macular degeneration (AMD) than the gain or loss of letters able to be seen in logMAR chart testing, suggest researchers.

A score of 6/18 on the Snellen visual acuity (VA) or the ability to see more than 60 letters on the logMAR chart could better reflect the quality of treatment and follow up of AMD patients, since gaining or losing letters may not correlate with good vision, adds the team.

The revised method of assessing AMD treatment also takes into account "starting vision, amount of treatment and follow-up, as well as the effectiveness of the treatment," say S James Talks (The Royal Victoria Infirmary, Newcastle upon Tyne, UK) and colleagues, who report that 50% of patients in their study had a Snellen VA of 6/18 over 4 years of follow up.

The study cohort included 1017 patients (mean age=75 years; 666=female) who began treatment with intravitreal ranibizumab between August 2007 and September 2009 and had a minimum of 2 years' follow-up data available. Patients received three loading doses of ranibizumab before follow up began.

In all, 88%, 72%, 64%, and 51% of patients were followed up at 12, 24, 36, and 48 months after treatment initiation.

Reasons for loss to follow up included that patients had health problems preventing them from attending, that they were living in a nursing home, were hospitalized, or deceased, or that they had transferred care elsewhere. The authors analyzed data for all these patients (n=76) and found that 64% of them had 6/18 Snellen VA when they were last seen.

"So it seems likely that failure of treatment was not the main cause for them not continuing follow up," note Talks and co-workers in the British Journal of Ophthalmology.

Overall, just 4.15%, 5.21%, and 6.62% of the cohort had vision of 3/60 - equivalent to fewer than 25 letters - and were thus considered eligible for visual impairment registration, after 12, 24, and 36 months of follow up, respectively, report Talks et al.

Not surprisingly, they remark, the maximum gains in VA were seen among patients with the poorest pretreatment VA (<35 logMAR letters; n=91), with 41% and 83% of these patients gaining more than 15 logMAR letters at 36 and 48 months, respectively.

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