Choroidal thickness and biometric markers for the screening of lacquer cracks in patients with high myopia

Abstract

Objectives: Validation of choroidal thickness and other biometrics measured by spectral domain optical coherence tomography (SD-OCT) in predicting lacquer cracks formation in highly myopic eyes.

Methods: Patients with a refractive error worse than -8 diopters and moderate myopic maculopathy were recruited into two groups based on the presence or absence of lacquer cracks (36 eyes without and 33 eyes with lacquer cracks). Choroidal thickness, refractive error, and axial length were measured and subjected to receiver operating characteristic curve analysis to identify the optimal cutoff values at predicting lacquer crack formation. The width of the retinal pigment epithelium (RPE), RPE to the inner segment/outer segment line, RPE to the external limiting membrane were also measured and compared to the subfoveal choroidal thickness to assess their relationships as potential markers of lacquer crack formation.

Results: Lacquer crack is associated with decreased choroidal thickness, lower best-corrected visual acuity, longer axial length and higher refractive errors. Choroidal thickness has the strongest association with lacquer crack formation versus axial length and refractive error. In eyes with lacquer cracks, stellate lacquer cracks are associated with thinner choroidal thickness compared to eyes with linear lacquer cracks. Subfoveal choroidal thickness less than the width of the retinal pigment epithelium to the inner segment/outer segment line is also associated with lacquer crack formation (sensitivity 78.8%, specificity 88.3%, and accuracy 81.2%).

Conclusions: This study suggests that choroidal thickness and other SD-OCT measurements could be employed clinically to predict the development and severity of lacquer cracks in patients with high myopia.

Figure 1. Examples of indocyanine green angiography (ICGA) and spectral domain optical coherence tomography (SD-OCT) in highly myopic eyes.

ICGA (left) and SD-OCT (right) in highly myopic eyes without lacquer crack (top), with linear lacquer cracks (middle), or with stellate lacquer cracks (bottom). (Top). No lacquer cracks shown on ICGA and SD-OCT reveals a choroidal layer of normal thickness. (Middle). Linear lacquer cracks seen on ICGA and SD-OCT shows a mildly reduced subfoveal choroidal thickness. (Bottom). Stellate lacquer cracks seen on ICGA and SD-OCT reveals a markedly reduced subfoveal choroidal thickness compared to top right and middle right.

Figure 2. Identification of Additional Biometrical Markers of Lacquer Cracks.

Subfoveal choroidal thickness is compared to the width of the RPE, distance between the outer layer of the RPE to the inner segment/outer segment line (RIOS), and the distance between the outer layer of the RPE to the external limiting membrane (REL), at the center of the foveola. The sensitivity, specificity, and accuracy of these relationships at predicting lacquer crack formation were calculated.

Figure 3. Scatterplots of macular choroidal thickness vs subfoveal choroidal thickness in all eyes.

Solid circles show eyes with lacquer cracks and unfilled circles show eyes without lacquer cracks. Subfoveal choroidal thickness correlated significantly with macular choroidal thickness in all eyes (R² = 0.919, P<0.001).

Figure 4. Receiver operating characteristic curves of 4 biometrics at predicting the formation of lacquer cracks.

The areas under the curve from the highest to lowest were macular choroidal thickness (0.926), subfoveal choroidal thickness (0.897), axial length (0.858), and refractive error (0.694).