Area of the cone interdigitation zone in healthy Chinese adults and its correlation with macular volume

Numerous studies have suggested that the integrity of the cone interdigitation zone (IZ) could be considered to be a marker of photoreceptor damage and its recovery. However, little is known about the IZ in healthy eyes. Our present study was to measure the cone IZ area by optical coherence tomography (OCT), and determine its distribution in healthy adults.

This was a cross-sectional non-interventional study. We involved a group of 158 emmetropic or low myopic (from -3D to + 0.5D) eyes in 97 healthy adult volunteers. All subjects underwent thorough ophthalmologic examinations and the posterior pole was scanned by OCT. The cone IZ area in healthy adults and its correlation with macular volume and other factors was analyzed.

The cone IZ was visible and clear in all 158 eyes, and the IZ area was successfully measured by 6 radical scans centered on the fovea. The mean IZ area was 30.22 ± 12.70 mm², and ranged from 5.91 to 57.47 mm². The IZ area exhibited a normal distribution (P = 0.635) with 95% confidence interval of 28.06-32.29 mm². The IZ area was significantly correlated with the retinal and outer nuclear layer (ONL) volumes within the macula.

The cone IZ area could be measured using a commercially available OCT system. The IZ area showed high variability among healthy adults, and this might be related to the variability in the photoreceptor distribution in healthy adults.