Poster Vesta Cheuk Ki Chan

Purpose:

To measure choroidal thickness in myopic eyes using enhanced depth imaging in a cross-sectional study.

Methods:

Fifty-six consecutive patients with spherical equivalent refractive error of at least 6 dioptres were evaluated using enhanced depth imaging optical coherence tomography images that were obtained by positioning the spectral-domain optical coherence tomography (OCT) device close enough to the eye to acquire an enhanced signal of the choroidal layer. The choroidal depth was measured as the distance between the outer reflective retinal pigment epithelium layer and the inner sclera border. Measurements were made at horizontal fashion across the fovea at 500µm intervals of sections. Choroidal thickness (CT) was measured at the subfoveal region, 3mm temporal to fovea and 3 mm nasal to fovea respectively in a horizontal fashion.

Main outcome measures:

Correlations between choroidal thickness with age, refractive error in dioptres (D), visual acuity in logarithm of the minimum angle of resolution (log MAR) respectively were analysed with linear mixed models.

Results & Effectiveness:

The mean age of the 56 patients was 50.4 years ( +/- 2.03 years standard deviation SD; interquartile range IQR: 42 years to 62 years) , and the mean refractive error was – 8.7 D (IQR; -6.1D to -11D) . The mean subfoveal CT was 118µm ( +/- 68μm ) and was correlated negatively with age (P=0.032) and refractive error (P=0.011). Regression analysis suggested that subfoveal CT decreased by 11.9µm per each decades of life and by 6.205µm for each dioptre of myopia. The subfoveal choroidal thickness was inversely correlated with logarithm of the minimum angle of resolution visual acuity (P=0.008) and visual acuity improved by 0.02 (log MAR) by 10µm increase in choroidal thickness.

Conclusion & Take home message:

Choroidal thickness decreases with age and severity of myopia. Visual acuity drops in line with decreasing subfoveal choroidal thickness. Reduction in choroidal thickness is related to aging and severity of myopia, while visual acuity depends on subfoveal choroidal thickness. Our study supports the theory that choroidal abnormality may play a key role in pathogenesis of myopic degeneration.