Change in drusen area over time compared using spectral-domain optical coherence tomography and color fundus imaging

Abstract

Purpose: To investigate the relationship between drusen areas measured with color fundus images (CFIs) and those with spectral-domain optical coherence tomography (SDOCT).

Methods: Forty-two eyes from thirty patients with drusen in the absence of geographic atrophy were recruited to a prospective study. Digital color fundus images and SDOCT images were obtained at baseline and at follow-up visits at 3 and 6 months. Registered, matched circles centered on the fovea with diameters of 3 mm and 5 mm were identified on both CFIs and SDOCT images. Spectral-domain OCT drusen measurements were obtained using a commercially available proprietary algorithm. Drusen boundaries on CFIs were traced manually at the Doheny Eye Institute Image Reading Center.

Results: Mean square root drusen area (SQDA) measurements for the 3-mm circles on the SDOCT images were 1.451 mm at baseline and 1.464 mm at week 26, whereas the measurements on CFIs were 1.555 mm at baseline and 1.584 mm at week 26. Mean SQDA measurements from CFIs were larger than those from the SDOCT measurements at all time points (P = 0.004 at baseline, P = 0.003 at 26 weeks). Changes in SQDA over 26 weeks measured with SDOCT were not different from those measured with CFIs (mean difference = 0.014 mm, P = 0.5).

Conclusions: Spectral-domain OCT drusen area measurements were smaller than the measurements obtained from CFIs. However, there were no differences in the change in drusen area over time between the two imaging modalities. Spectral-domain OCT measurements were considerably more sensitive in assessing drusen area changes.

Keywords: age-related macular degeneration; color fundus photography; drusen; optical coherence tomography.

Figure 1

Registration of color and OCT fundus images. (A) Circles with diameters of 3 mm and 5 mm are centered on the fovea and marked on the spectral-domain optical coherence tomography fundus image (OFI), which is registered with the color fundus image (CFI). (B) Circles with diameters of 3-mm and 5-mm circles are transferred from the OFI to the CFI. (C) The CFI area contained within the circles was isolated and sent to the Doheny Image Reading Center for manual grading.

Figure 2

Drusen areas were measured with different imaging modalities. (A) Central 3-mm and 5-mm circles were superimposed on a color fundus image (CFI). (B) Manually outlined drusen on the CFI, as shown in (A). (C) Automated drusen area map was calculated using the spectral-domain optical coherence tomography (SDOCT) algorithm. (D) Composite image shows the manually outlined drusen shown in (B) and the automated drusen map shown in (C).

Figure 3

Comparison of the square root drusen area measurements within the central 3-mm circle obtained using color fundus images (CFI) and spectral-domain optical coherence tomography (SDOCT). Solid line is the bisector.

Figure 4

Changes in square root drusen area (SQDA) measurements within the central 3-mm circle. (A) Square root drusen area at baseline versus SQDA at week 26, obtained using spectral-domain optical coherence tomography (SDOCT). (B) Square root drusen area at baseline versus SQDA at 26 weeks, obtained using color fundus images (CFI). Solid line is the bisector.

Figure 5

Changes in square root drusen area (SQDA) measurements within the central 3-mm circle over 26 weeks. (A) Change in SQDA was obtained using spectral-domain optical coherence tomography (SDOCT) images versus changes in SQDA obtained using color fundus images (CFIs). Solid line is the bisector. (B) Histograms of the changes in SQDA as measured with CFIs (left) and SDOCT (right).