medwireNews: Progressive choroidal thinning, as measured by swept-source optical coherence tomography (OCT) “plays a key role” in the evolution of myopic maculopathy in patients with high myopia, say researchers.
The retrospective analysis, conducted by Kyoko Ohno-Matsui (Tokyo Medical and Dental University, Japan) and colleagues, showed that the mean subfoveal choroidal thickness (CT) of 1487 eyes (from 884 patients) with high myopia at a single clinic in Japan was “extremely thin”, at 72.7 μm.
But the researchers note that the mean thickness varied markedly depending on the location measured, ranging from 30.1 μm at the nasal location to 98.2 μm at the superior location. This indicates that “[c]horoidal thinning starts nasal to the fovea and then enlarges toward […] the fovea”, they remark.
In addition, the team found that CT decreased with an increasing severity of the myopic maculopathy, particularly at the subfovea.
At this location, the mean CT in eyes with normal fundus was 274.5 μm, decreasing to 129.1 μm in those with tessellation and further still to 84.6 μm and 50.2 μm in eyes with peripapillary diffuse choroidal atrophy (PDCA) and macular diffuse choroidal atrophy (MDCA), respectively.
For eyes with patchy atrophy mean subfoveal CT was 48.6 μm, it was 27.3 μm in those with choroidal neovascularization (CNV)-related MA and just 3.5 μm in eyes with patchy atrophy-related MA.
Using receiver operating characteristic curves, Ohno-Matsui and co-investigators determined that the optimal CT cutoff for the differentiation between tessellation and PDCA was 56.5 μm nasally, with a sensitivity and specificity of 79% and 63%, respectively.
For differentiating between PDCA and MDCA the optimal CT cutoff was 62 μm subfoveally, which gave a sensitivity and specificity of 71% and 72%, respectively.
However, the authors found that there was no significant difference in subfoveal CT between eyes with MDCA and patchy atrophy. Therefore, “[f]or the progression from MDCA to patchy atrophy, factors other than further choroidal thinning such as a development of [Bruch membrane] holes may play an important role”, they say.
The study findings are published in Ophthalmology, where the researchers also describe patterns of choroidal thickness for each type of myopic maculopathy overall and when stratified according to patient age.
Briefly, they found that the distribution pattern of the CT differed markedly between the eyes with tessellation and those with no maculopathy, with the pattern in eyes with tessellation similar to that of eyes with other lesions of myopic maculopathy.
“This suggested that the tessellation might be the first sign for myopic eyes to become pathologic”, Ohno-Matsui et al remark.
By Laura Cowen
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