Use of Optical Coherence Tomography Over MRI Can Increase Eyecare Efficacy

A new study published in PLoS One is the first of its kind to systematically describe and quantify the difference between measured curvature and actual retinal contour of the eye using optical coherence tomography (OCT).

Researchers determined effective use of OCT is faster and cheaper than using MRI and can be instrumental in diagnosing myopia, or short/near sightedness.

Myopia is the world’s most common vision problem and can cause vision loss and sometimes blindness. It is previously recorded that highly myopic eyes tend to be more irregular in shape than non-myopic eyes. For example, staphyloma at the posterior pole is a common feature of high myopia.

Researchers at Flinders University in Australia utilized images taken from 70 volunteers using OCT, which is already available in all ophthalmic practices. Participants were included if their eyes had no abnormalities on examination.

Stewart Lake, MBCHB, a lead author of the study, said, “Our work uses the OCT and finds irregularities at this scale that correlate with the size of the eye, and therefore the degree of myopia…This may help monitor, measure, and explore the effects of myopia and how it leads to vision loss.”

Although MRI can be used to image the entire eye, it has a limited resolution of 0.5 mm. In comparison, “OCT resolution approaches 2 μm in the axial direction, and up to 10 μm laterally,” authors said.

Measurements by Fourier transformation showed the following retinal shape irregularities all correlated with axial length:

• all-of-eye median and IQR sumdiff (P = .66 and P = .60 respectively)
• median and IQR rmse (P = .67 and P = .48),
• median MaxE (P = .61), and IQR K (P = .61)

“Correlation with axial length was also seen in these parameters for 11 of 17 regions. Retinal irregularity was greatest at the macula and in inferior regions,” researchers said.

This identification of greater irregularities in inferior retinal regions, regardless of axial length, was a novel finding. Although it relates to alterations in choroidal thickness, “the irregular contour seen in dome-shaped maculopathy has been reported to be due to variations in scleral thickness leading to alterations in scleral rigidity.”

This new method of determining retinal shape using OCT can be used to more effectively describe myopic eye disease “and to examine the retinal shape in other eye conditions,” authors concluded.

Reference

Lake S, Bottema M, Williams K, Reynolds K. The correlations between optical coherence tomography retinal shape irregularity and axial length [published online December 30, 2019]. PLoS One. doi: 10.1371/journal.pone.0227207.