A comparison of fundus autofluorescence and retinal structure in patients with Stargardt disease

Abstract

Purpose: To improve the understanding of Stargardt disease by comparing structural changes seen on spectral domain optical coherence tomography (SD-OCT) to those visible on fundus autofluorescence (FAF).

Methods: FAF and SD-OCT were performed on 22 eyes of 11 patients with Stargardt disease. SD-OCT images were obtained at the fovea and at the eccentric preferred retinal locus (PRL). The diameters of absent (hypoautofluorescence) and abnormal FAF areas were measured. The extent of the transverse defect of the junction between the inner and outer segments of the photoreceptors (IS-OS) was measured in the foveal area. The PRL was evaluated with fundus photography and microperimetry.

Results: Twenty-one of 22 eyes showed defective FAF. In 17 eyes, FAF was absent in the fovea and in four eyes, FAF was abnormal. All eyes showed disorganization and/or loss of the IS-OS junction in the foveal area on SD-OCT. The diameter of the absent FAF area was smaller than the measurement of the IS-OS junction loss; the latter was closer to the diameter of the abnormal FAF area. Seventeen eyes had an eccentric PRL associated with a retinal area with no defects on FAF.

Conclusions: In the majority of eyes, changes shown by SD-OCT correlated well with changes in FAF. However, in three patients, photoreceptor abnormalities were seen in the fovea on SD-OCT without an equivalent abnormality on FAF. This result suggests that in these patients, the structural integrity of the photoreceptors may be affected earlier than changes in the RPE at least as detected by FAF.

Figures

Figure 1

A-D: A: FAF image demonstrating the two measurements. The diameter of the central area of absent FAF corresponding to geographic atrophy and the diameter of abnormal FAF. B. SD-OCT image through the fovea of a normal control. C. SD-OCT image showing the extent of the transverse loss of the inner segment outer segment (IS-OS) junction of the photoreceptors in the foveal region (Patient 7) D. A comparison of the measurements obtained from FAF shown in A to those from SD-OCT for Patient 7.

Figure 2

A-F: Examples of FAF images A. Absence of FAF in the fovea, corresponding to areas of RPE atrophy visible on fundus examination (Patient 3). B. Areas of hypo- and hyper-autofluorescence limited to the perifoveal area (Patient 8). C. Areas of focally increased autofluorescence (focal FAF) extending up to the vascular arcades (Patient 4). D. Areas of focal FAF extending past the arcades (Patient 2). E. Mottling on the foveal center without any other visible areas of hypo or hyperautofluorescence in the posterior pole (Patient 11) F. An apparently normal FAF examination (Patient 10).

Figure 3

A: FAF image and SD-OCT image through the fovea for patient 3. The white line shows the location of the SD-OCT scan. B. FAF image and SD-OCT image through the eccentric PRL for the same patient. The white line shows the location of the SD-OCT scan.

Figure 4

A-D: FAF and SD-OCT images for 3 patients and a normal control A. Images obtained from a control subject. B. The FAF shows an area of central atrophy and the SD-OCT image shows the loss of the IS-OS junction (Patient 6). C. The FAF shows only minimal changes and the SD-OCT image shows an area of localized loss of the photoreceptors (Patient 11) D. The FAF examination appears to be normal but disorganization of the outer retinal layers is visible on SD-OCT (Patient 10).

Figure 5

A: A comparison between the extent of the IS-OS junction loss on SD-OCT and the diameter of the hypoautofluorescent/absent FAF area. B. A comparison between the transverse IS-OS junction loss on SD-OCT and the diameter of the area of abnormal FAF.