May 20 2015
By Lucy Piper, Senior medwireNews Reporter
Age-related macular degeneration (AMD) in one eye tracks the severity of it in the fellow eye at all stages of the disease, findings from the Beaver Dam Eye study show.
The study researchers used 30° colour fundus photographs to grade the severity of AMD according to the Wisconsin Age-Related Maculopathy Grading System in the primary eye of 4379 patients.
The five grades ranged from no AMD (level 1) to late AMD (level 5), characterised as pure geographic atrophy in the absence of exudative macular degeneration, or exudative macular degeneration with or without geographic atrophy.
Participants were then classified as being in one of 26 AMD states, based on whether severity in each eye stayed the same, improved, worsened or the patient died, over a total of 12,640 follow-up visits, with up to four per participant. These multistate models allowed the likelihood of disease progression to be calculated at the eye level rather than the participant level, the team explains.
The results, published in JAMA Ophthalmology, showed that in a given eye progression was more common and regression less common. And if AMD was more severe in one eye then the risk of AMD and accelerated progression was significantly increased in the fellow eye. The risk of transition up a level was increased 4.9-fold for level 1 to 2, 2.09-fold for level 2 to 3, 2.38-fold for level 3 to 4 and 2.46-fold for transition from level 4 to 5.
By contrast, less severe AMD in one eye was associated with a lesser incidence of AMD progression in the fellow eye, with odds ratios of 0.42 for transitioning from level 2 to 3 and 0.50 for transitioning from level 3 to 4.
The researchers, Ronald Klein (University of Wisconsin School of Medicine and Public Health, Madison, USA) and colleagues, were also able to calculate 5-year transition probabilities according to age and AMD severity, after taking into account gender and complement factor H genotype status.
The probability of a patient aged 50 years with AMD in one eye developing AMD in the fellow eye within the next 5 years was 7% versus 2% if they did not already have AMD in one eye. Similar effects were seen in older patients. Also, the probability of transitioning to a worse level of severity increased as severity in the fellow eye progressed.
The researchers estimated the degree to which AMD severity in one eye tracks that of the fellow eye by simulating realisations of AMD history for 1000 participants free of AMD at 45 years of age from the multistate models.
They found that 51% of participants who developed any AMD always maintained AMD severity states in both eyes that were within one level of each other, while severity states stayed within two levels for 90% of participants.
“This information may be helpful to clinicians in assessing the prognosis of the better eye”, the researchers say.
They note that their modelling approach can be extended to include additional determinates of AMD to provide greater insight into the effect of genetic and environmental factors on the course of AMD.
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