Effect of high myopia on glaucoma diagnostic parameters measured with optical coherence tomography

We examined the influence of high myopia on conventional spectral-domain optical coherence tomographic parameters and assessed the macular ganglion cell complex thickness to macular outer retinal thickness ratio as a new optical coherence tomography parameter.

Prospective cross-sectional study.

Sixty normal and 30 highly myopic eyes (refractive error more than -6 D).

We used the RTVue-100 to measure macular ganglion cell complex and circumpapillary retinal nerve fibre layer thickness, global loss volume, and focal loss volume and then calculated the ganglion cell complex thickness to macular outer retinal thickness ratio.

Each parameter was compared between the two groups. Using the area under receiver operating characteristics curve, the classification abilities of optical coherence tomography parameters were examined in highly myopic eyes.

Between normal and highly myopic eyes, we found significant differences in ganglion cell complex and retinal nerve fibre layer thickness, global loss volume and focal loss volume. The new ratio parameter was not significantly different between groups (55.74% vs. 54.50%). The area under receiver operating characteristics curve was 0.775 (P < 0.01) for retinal nerve fibre layer thickness, 0.721 (P < 0.01) for ganglion cell complex thickness and 0.588 (P > 0.05) for the new ratio parameter.

Although refractive status significantly affected conventional optical coherence tomography parameters, the new ratio parameter may not be influenced by refractive error. Therefore, a normative database for healthy highly myopic eyes may not be necessary if ratio parameter is used.