Citation: Sampson DM, Gong P, An D, et al. Axial length variation impacts on superficial retinal vessel density and foveal avascular zone area measurements using optical coherence tomography angiography. Invest Ophthalmol Vis Sci. 2017;58:3065-3072. DOI:10.1167/iovs.17-21551 PURPOSE. To evaluate the impact of image magnification correction on superficial retinal vessel density (SRVD) and foveal avascular zone area (FAZA) measurements using optical coherence tomography angiography (OCTA). METHODS.Participants with healthy retinas were recruited for ocular biometry, refraction, and RTVue XR Avanti OCTA imaging with the 3 3 3-mm protocol. The foveal and parafoveal SRVD and FAZA were quantified with custom software before and after correction for magnification error using the Littman and the modified Bennett formulae. Relative changes between corrected and uncorrected SRVD and FAZA were calculated.RESULTS. Forty subjects were enrolled and the median (range) age of the participants was 30 (18-74) years. The mean (range) spherical equivalent refractive error was À1.65 (À8.00 to þ4.88) diopters and mean (range) axial length was 24.42 mm (21.27-28.85). Images from 13 eyes were excluded due to poor image quality leaving 67 for analysis. Relative changes in foveal and parafoveal SRVD and FAZA after correction ranged from À20% to þ10%, À3% to þ2%, and À20% to þ51%, respectively. Image size correction in measurements of foveal SRVD and FAZA was greater than 5% in 51% and 74% of eyes, respectively. In contrast, 100% of eyes had less than 5% correction in measurements of parafoveal SRVD.CONCLUSIONS. Ocular biometry should be performed with OCTA to correct image magnification error induced by axial length variation. We advise caution when interpreting interocular and interindividual comparisons of SRVD and FAZA derived from OCTA without image size correction.

Genetic predisposition may account for the variability in response to anti-VEGF treatment.

Adaptive optics scanning laser ophthalmoscopy provides adequate resolution for quantitative measurement of cone spacing at the margin of GA and over drusen in eyes with AMD. Although cone spacing was often normal at baseline and remained normal over time, these regions showed focal areas of decreased cone reflectivity. These findings may provide insight into the pathophysiology of AMD progression. (ClinicalTrials.gov number, NCT00254605).

The ONL thickness and cone density were correlated in normal eyes and eyes with RP, but both were strongly correlated with retinal eccentricity, precluding estimation of cone density from ONL thickness. (ClinicalTrials.gov number, NCT00254605.).

PurposeTo measure intrasession repeatability and interocular symmetry of the foveal avascular zone area (FAZA) and superficial retinal vessel density (SRVD) using AngioVue Analytics optical coherence tomography angiography (OCTA).MethodsFifty healthy individuals were prospectively enrolled. OCTA scans (3 × 3 and 6 × 6 mm) were acquired twice in right and once in left eyes. FAZA (with and without rescaling) and SRVD for 18 regions (whole, fovea, parafovea, six parafoveal subregions, and nine square zones) were compared between two scans in right eyes (repeatability) and between both eyes (symmetry). Coefficients of repeatability (CRs) and limits of agreement (LAs) were calculated.ResultsAxial length–based image size rescaling had negligible impact on the intrasession CR of FAZA in both 3 × 3- and 6 × 6-mm images. The intrasession CRs for the foveal SRVD were 3.3% and 6.1% in the 3 × 3- and 6 × 6-mm OCTA images, respectively. Age and axial length did not influence test–retest variability of FAZA or SRVD. The interocular LAs in FAZA (0.039–0.059 mm2) was comparable to its CR. However, the interocular LAs in foveal SRVD were −4.5% to +3.8%, with 13% of the cohort showing an interocular difference greater than the CR.ConclusionsFAZA repeatability is not influenced by image size correction, and foveal SRVD is more variable in 6 × 6- than 3 × 3-mm OCTA images. Low image quality may contribute to interocular SRVD asymmetry.Translational RelevanceCRs and LAs can be used to set a threshold for true changes in FAZA and SRVD in longitudinal studies of healthy individuals.