En face SD-OCT and SW-AF imaging were compared for tracking Stargardt disease progression; en face SD-OCT is a valuable tool for measuring retinal changes.
As more clinical trials pursue treatment of Stargardt disease, there is a greater need for accurate outcome measurement tools. For example, ellipsoid zone (EZ) and retinal pigment epithelium (RPE) loss, which are signs of disease progression, can be measured using en face spectral domain-optical coherence tomography (SD-OCT). Monitoring alterations in the hypoautofluorescent (hypoAF) and hyperautofluorescent (hyperAF) areas also provides insight into disease progression and can be identified with short-wavelength (SW)-AF in ABCA4-associated retinopathy. Variants in the ABCA4 gene cause Stargardt disease, the most common form of inherited macular dystrophy.
Anatomic Markers of Disease Progression
Most studies focusing on Stargardt disease have examined RPE loss and changes in hypoSW-AF to gauge disease progression; few studies have examined the loss of the EZ using SD-OCT. Both SD-OCT and SW-AF imaging can contribute to a better understanding of the manifestation and progression of Stargardt disease, and there is value in comparing the two. To that end, Vivienne C. Greenstein, PhD, and colleagues conducted a retrospective observational study to compare disease progression using these different markers, the results of which were published in Translational Vision Science & Technology.
Twenty patient participants with recessive Stargardt disease (20 eyes; 10 male; 10 female) were included. Genetic, clinical, and demographic information was gathered from all patients. The researchers collected scans of the patients’ eyes over a period of 1 to 5 years.
Measuring EZ Loss & Abnormal AF Areas
The SW-AF images obtained at the beginning of the study for 10 out of the 20 eyes exhibited a centralized area of hypoAF of changing size surrounded by a distinct outline of hyperAF and nearby hyperAF flecks. In eight of the 20 eyes, extensive hypoAF and hyperAF alterations that reached outside of the arcades were observed. The abnormal AF area at the beginning of the study was significantly more pronounced than the hypoAF area (median, 8.3 mm2 [first quartile (Q1), 4.6; third quartile (Q3), 16.5 mm2] vs median, 3.5 mm2 [Q1, 2.1; Q3, 8.2 mm2]; Wilcoxon matched-pairs signed rank test, P<0.0001). Upon completion of follow-up, the hypoAF and abnormal AF areas were increased for all eyes.
The subRPE slab images of the central hyperreflective areas were similar in size and shape to the central hypoAF areas on SW-AF. The en face EZ loss area was significantly larger at the beginning of the study than the subRPE area showing RPE atrophy (median, 8.3 mm2 [Q1, 5.4 mm2; Q3, 11.8 mm2] vs median, 3.4 mm2 [Q1, 2.1 mm2; Q3, 7.8 mm2]; Wilcoxon signed rank test, P<0.0001). By the end of the study, all eyes showed increases in the subRPE and EZ loss areas. Lesion enlargement was noted to be significantly greater for the EZ area than for the subRPE area (median, 1.2 mm2/year [Q1, 0.7 mm2; Q3, 1.8 mm2/year] vs median, 0.5 mm2/year [Q1, 0.3 mm2, Q3, 1.5 mm2/year]; Wilcoxon matched-pairs signed rank test P<0.0001).
En Face SD-OCT Complements SW-AF Imaging
The study showed that the two techniques used to measure changes in the eyes were comparable and provided reliable results.
“We have demonstrated that the en face SD-OCT technique can be used to quantify changes in RPE atrophy and photoreceptor integrity,” Dr. Greenstein and colleagues wrote. “It not only can be used as a complementary test to SW-AF for measuring changes in RPE atrophy but also more importantly measurements of the area of EZ loss provide valuable information in terms of photoreceptor loss.”
Key Takeaways
- Few studies have examined the loss of the ellipsoid zone using en face spectral domain-optical coherence tomography (SD-OCT).
- En face SD-OCT was found to accurately quantify changes in retinal pigment epithelium (RPE) atrophy and photoreceptor integrity.
- This imaging technique can be used as a compliment to short-wavelength autoflorescent for measuring changes in RPE atrophy.
