Findings from a study published in Ophthalmology Science assessed the macular and peripheral retinal volume (RV) in eyes without retinal disease using widefield swept-source optical coherence tomography (SS-OCT).
Give me some background.
Studies have shown that monitoring changes to macular RV (MRV) with spectral-domain OCT (SD-OCT) has the potential to fill a “diagnostic gap” and act as a biomarker for conditions like neovascular age-related macular degeneration (nAMD).
However, in contrast to the diode laser used in SD-OCT, SS-OCT utilizes a tunable wavelength light source that improves the penetration of the signal and allows for the capture of large fields of view at higher scan speeds.
Which brings us to …
Investigators sought to elucidate whether widefield SS-OCT could be used to evaluate the possible association between RV in the macula and peripheral retina and demographic/ocular anatomical characteristics in healthy eyes.
Now the study.
In this observational cross-sectional study, researchers included a total of 332 eyes from 166 healthy participants (101 women, mean age 43 years).
The eyes were imaged with OCT-S1 (Canon) using a protocol centered on the fovea cube scans (20 x 23 mm) of SS-OCT images.
A multivariate analysis was used to evaluate retinal volume (6-mm circle and 6- to 12-mm ring) and various parameters.
Note: Each quadrant of the macular—except for the fovea (1-6 mm in diameter) and peripheral ring (6-20 mm in diameter)—was also evaluated.
Findings?
The temporal area was significantly smaller than all other areas in the macula, while the inferior area was significantly smaller than all other areas in the peripheral retina.
In the macula (1-6 mm), the RVs were as follows:
- Nasal quadrant: 2.233mm3
- Superior quadrant: 2.137mm3
- Inferior quadrant: 2.057mm3
- Temporal quadrant: 2.034mm3
In the peripheral retina (6-20 mm), the RVs were:
- Nasal quadrant: 18.4mm3
- Superior quadrant: 16.4mm3
- Temporal quadrant: 15.5mm3
- Inferior quadrant: 15.2mm3
Anything else?
The multivariate analysis demonstrated that older age and longer axial length were associated with smaller macular RV.
Conversely, older age and left eye were associated with smaller peripheral retinal volume.
Expert opinion?
The study authors noted that the finding that the peripheral retina was significantly smaller in the left eye should be interpreted with caution because they examined the right eye first—which may have impacted the results.
Limitations?
Notable limitations in the study included:
- The incident light on the retina was not perpendicular to the retina as it moved toward the periphery—potentially causing measurement errors
- Images from long axial eye lengths cover more peripheral regions compared to those acquired from short axial eyes, resulting in a possible overestimation of the statistical significance between peripheral RV and axial eye lengths
- The male/female ratio was inconsistent for each age group, and the study population comprised only Japanese participants
Take home.
These findings indicate that in widefield SS-OCT images, age and left eye were negatively correlated with peripheral retinal volume.
In addition, the researchers confirmed that the inferior retina is the thinnest part of the peripheral retina.