Study of Late-Onset Stargardt Type 1 Disease: Characteristics, Genetics, and Progression

PURPOSE

Late-onset Stargardt disease is a subtype of Stargardt disease type 1 (STGD1), defined by an age of onset of 45 years or older. We describe the disease characteristics, underlying genetics, and disease progression of late-onset STGD1 and highlight the differences from geographic atrophy.

DESIGN

Retrospective cohort study.

PARTICIPANTS

Seventy-one patients with late-onset STGD1.

METHODS

Medical files were reviewed for clinical data including age at onset, initial symptoms, and best-corrected visual acuity. A quantitative and qualitative assessment of retinal pigment epithelium (RPE) atrophy was performed on fundus autofluorescence images and OCT scans.

MAIN OUTCOME MEASURES

Age at onset, genotype, visual acuity, atrophy growth rates, and loss of external limiting membrane, ellipsoid zone, and RPE.

RESULTS

Median age at onset was 55.0 years (range, 45-82 years). A combination of a mild and severe variant in ATP-binding cassette subfamily A member 4 (ABCA4) was the most common genotype (n = 49 [69.0%]). The most frequent allele, c.5603A→T (p.Asn1868Ile), was present in 43 of 71 patients (60.6%). No combination of 2 severe variants was found. At first presentation, all patients have flecks. Foveal-sparing atrophy was present in 33.3% of eyes, whereas 21.1% had atrophy with foveal involvement. Extrafoveal atrophy was present in 38.9% of eyes, and no atrophy was evident in 6.7% of eyes. Time-to-event curves showed a median duration of 15.4 years (95% confidence interval, 11.1-19.6 years) from onset to foveal involvement. The median visual acuity decline was -0.03 Snellen decimal per year (interquartile range [IQR], -0.07 to 0.00 Snellen decimal; 0.03 logarithm of the minimum angle of resolution). Median atrophy growth was 0.590 mm2/year (IQR, 0.046-1.641 mm2/year) for definitely decreased autofluorescence and 0.650 mm2/year (IQR, 0.299-1.729 mm2/year) for total decreased autofluorescence.

CONCLUSIONS

Late-onset STGD1 is a subtype of STGD1 with most commonly 1 severe and 1 mild ABCA4 variant. The general patient presents with typical fundus flecks and retinal atrophy in a foveal-sparing pattern with preserved central vision. Misdiagnosis as age-related macular degeneration should be avoided to prevent futile invasive treatments with potential complications. In addition, correct diagnosis lends patients with late-onset STGD1 the opportunity to participate in potentially beneficial therapeutic trials for STGD1.

FINANCIAL DISCLOSURE(S)

The author(s) have no proprietary or commercial interest in any materials discussed in this article.

Multimodal Imaging for the Assessment of Geographic Atrophy in Patients with "Foveal" and "No-Foveal" Sparing

INTRODUCTION

The aim of the study was to evaluate the applicability of optical coherence tomography (OCT) angiography (OCTA) for measuring geographic atrophy (GA) areas in age-related macular degeneration (AMD) patients with "foveal" and "no-foveal" sparing disease and compare it to other imaging modalities.

METHODS

A multimodal imaging protocol was applied, using infrared (IR) imaging, fundus autofluorescence (FAF), OCTA, and en-face OCT in 35 eyes of 23 AMD patients with GA. Patients were classified into 2 groups, with and without foveal sparing disease. GA area measurements for all imaging modalities were compared for each group separately.

RESULTS

The measured GA area was estimated to be 6.68 ± 3.18 mm2 using IR; 6.99 ± 3.09 mm2 using FAF; 6.56 ± 3.11 mm2 using OCTA, and 6.65 ± 3.14 mm2 using en-face OCT. There was no statistically significant difference in the GA area between different modalities (p = 0.977). When separate analysis was conducted for patients with "foveal" and "no-foveal" sparing disease, although GA measurements in FAF imaging displayed higher numerical values than the other modalities, especially in patients with foveal sparing, no statistically significant difference in the GA area was found between the different imaging modalities in either group (p = 0.816 for foveal sparing; p = 0.992 for no-foveal sparing group).

CONCLUSIONS

OCTA can be reliably used in the assessment of GA in AMD patients with and without foveal sparing disease. For both groups, measurements are comparable to IR, en-face OCT, and FAF, despite the fact that the latter recorded larger area of GA, mainly in the foveal sparing cases.