Comparison of Visual Acuity Loss in Patients with Different Stages of Stargardt’s Disease

Inherited retinal diseases are the most common cause of blindness in the working-age population in Australia

Background: This study examined the frequency of inherited retinal diseases (IRDs) as the reason for blindness registrations over the last two decades and the demographic and clinical phenotypes of inherited retinal disease (IRD)-related registrations.

Materials and methods: Retrospective, observational study of individuals registered with a state-wide blind and vision-impaired registry. Low-vision or blindness-only (≤20/200 or ≤20°) certificates issued to children (0-15 years), working-age (16-64 years) and older-age (65 and older) adults were assessed. Sex and age distributions were examined for the top 20 reasons for certification. Demographic and clinical features of specific phenotypes of IRDs listed in the registry were examined.

Results: Amongst 11824 low-vision certificates issued between July 1995 and January 2017, 679 (5.7%) listed an IRD as the reason for registration. In individuals with blindness-only certification (N=4919), IRDs was the second most common diagnosis (8.3%), overtaking glaucoma (8.1%) and diabetic retinopathy (5.4%). IRD was the second most common reason for low-vision certification amongst children (11.6%) and the most common reason amongst working-age population (23.3%). The mean±SD age for IRD-related blindness-only certification was 46±20 years. The top three phenotypes of IRD-related low-vision certification were non-syndromic retinitis pigmentosa (54%), Stargardt disease (12%) and macular dystrophy (8%).

Conclusion: Our findings of IRDs as a common cause of blindness in all ages justify continued funding for providing low-vision services and developing treatments for these conditions.

An optometrist's guide to the top candidate inherited retinal diseases for gene therapy

This review presents the phenotypic and genotypic profiles of a select group of inherited retinal diseases (IRDs) that are currently the focus of retinal gene therapy trials globally. Research progress in IRD treatment trials may soon lead to their availability in Australia and New Zealand, as either approved treatment or a clinical trial. The salient clinical characteristics of retinitis pigmentosa-the largest IRD category-are highlighted, with specific reference to RPE65-associated Leber congenital amaurosis, followed by other specific IRDs, namely choroideremia and ABCA4-associated Stargardt disease. These IRDs are selected based on their candidacy for gene therapy. Guidance on the clinical diagnostic tests that support each of these diagnoses will be presented. More broadly, the most useful structure and function measures to monitor IRD progression is discussed, along with the key assessments that offer differential diagnostic insight. This review is intended to be a clinical guide for optometrists, to assist in assessment and management of individuals who may be eligible for current and future gene therapies. A companion article in this issue will provide an overview of the basic principles of gene therapy and its development as a new treatment for inherited retinal diseases.

Clinical and genetic analysis of the ABCA4 gene associated retinal dystrophy in a large Chinese cohort

ABCA4 gene associated retinal dystrophies (ABCA4-RD) are a group of inherited eye diseases caused by ABCA4 gene mutations, including Stargardt disease, cone-rod dystrophy and retinitis pigmentosa. With the development of next-generation sequencing (NGS), numerous clinical and genetic studies on ABCA4-RD have been performed, and the genotype and phenotype spectra have been elucidated. However, most of the studies focused on the Caucasian population and limited studies of large Chinese ABCA4-RD cohorts were reported. In this study, we summarized the phenotypic and genotypic characteristics of 129 Chinese patients with ABCA4-RD. We found a mutation spectrum of Chinese patients which is considerably different from that of the Caucasian population and identified 35 novel ABCA4 mutations. We also reported some rare and special cases, such as, pedigrees with patients in two generations, patients diagnosed with cone-rod dystrophy or retinitis pigmentosa, patients with subretinal fibrosis and patients with preserved foveal structure. At the same time, we focused on the correlation between the genotypes and phenotypes. By the comprehensive analysis of multiple clinical examinations and the application of multiple regression analysis, we proved that patients with two "null" variants had a younger onset age and reached legal blindness earlier than patients with two "none-null" variants. Patients with one or more "none-null" variants tended to have better visual acuity and presented with milder fundus autofluorescence changes and more preserved rod functions on the full-field electroretinography than patients with two "null" variants. Furthermore, most patients with the p.(Phe2188Ser) variant shared a mild phenotype with a low fundus autofluorescence signal limited to the fovea and with normal full-field electroretinography responses. Our findings expand the variant spectrum of the ABCA4 gene and enhance the knowledge of Chinese patients with ABCA4-RD.

Saccadic movements assessment in eccentric fixation: A study in patients with Stargardt disease

PURPOSE

To investigate saccadic movements in subjects with eccentric fixation due to a deep central scotoma in Stargardt disease (STGD).

METHODS

We studied 10 patients with STGD and 10 healthy subjects (control group). Saccadic movements of all the 20 subjects were assessed by using the eye tracker technique Tobii Glasses Pro 2. Standard measurements of reading ability (MNREAD charts), visual acuity (ETDRS charts), contrast sensitivity (Pelli-Robson charts), reading contrast threshold and speed (REX charts), retinal sensitivity and stability and localization of the fixation (MP1 fundus perimetry) were obtained in all subjects.

RESULTS

The saccadic movements time was significantly slower in STGD than in healthy subjects (699 ± 193 ms vs 299 ± 40 ms, p < 0.001). When STGD patients moved fixation to the target localized in retinal scotomatous areas, the movement was significantly slower compared to non scotomatous areas in the retina (1103 ± 798 ms vs 524 ± 187 ms, p = 0.039). There was a trend toward a correlation between slow saccadic movements in STGD subjects and the reading performance indices, although statistical significance was not achieved.

CONCLUSION

Ocular saccades guided by eccentric fixation in STGD patients are significantly slower than in the control group, especially when the target corresponds to retinal areas with a deep scotoma. These results can explain the worse reading performance in STGD subjects, in particular when a non-viewing area on the right part of the text is present.

Biofeedback Rehabilitation and Visual Cortex Response in Stargardt's Disease: A Randomized Controlled Trial

Purpose

to evaluate the effect of biofeedback (BF) rehabilitation on the visual function and on the activity of primary visual cortex (PVC) in patients with Stargardt's disease owing to mutations in the ABCA4 gene (STGD1).

Methods

This was a single-center, controlled, randomized study. Twenty-four patients with STGD1 were randomized into two groups: a treatment group (TG) undergoing BF rehabilitation and a control group (CG). Treatment with BF consisted of a 10-minute session per eye performed weekly for 12 weeks. The subjects underwent a baseline and 3-month follow-up visits, including best-corrected visual acuity (BCVA), reading test, microperimetry, and functional magnetic resonance imaging (fMRI). The fMRI studies were acquired sequentially using a passive viewing condition and an active reading task. The primary outcomes were the change in the fMRI activation of primary visual cortex and the change in reading ability.

Results

After treatment, the patients in the TG were able to read smaller characters (P = 0.002) with a greater reading speed (P = 0.014) compared with patients in the CG. The fMRI studies showed a significant effect (P < 0.001) of BF on primary visual cortex activation in the TG compared with the CG. Finally, we observed significant (P < 0.05) improvements of best-corrected visual acuity, macular sensitivity, and fixation stability parameters in the TG compared with the CG.

Conclusions

Our study showed that visual rehabilitation using BF improved the usage of residual visual function in patients with STGD1.

Translational Relevance

Our findings show that the BF treatment compared with no treatment at all resulted in benefits. The specificity of the treatment could be examined to determine whether BF can be included in clinical practice.

Case report of instantaneous resolution of juvenile macular degeneration blindness after proximal intercessory prayer

An 18-year-old female lost the majority of her central vision over the course of three months in 1959. Medical records from 1960 indicate visual acuities (VA) of less than 20/400 for both eyes corresponding to legal blindness. On fundus examination of the eye there were dense yellowish-white areas of atrophy in each fovea and the individual was diagnosed with juvenile macular degeneration (JMD). In 1971, another examination recorded her uncorrected VA as finger counting on the right and hand motion on the left. She was diagnosed with macular degeneration (MD) and declared legally blind. In 1972, having been blind for over 12 years, the individual reportedly regained her vision instantaneously after receiving proximal-intercessory-prayer (PIP). Subsequent medical records document repeated substantial improvement; including uncorrected VA of 20/100 in each eye in 1974 and corrected VAs of 20/30 to 20/40 were recorded from 2001 to 2017. To date, her eyesight has remained intact for forty-seven years.

Correlating the Expression and Functional Activity of ABCA4 Disease Variants With the Phenotype of Patients With Stargardt Disease

Purpose

Stargardt disease (STGD1), the most common early-onset recessive macular degeneration, is caused by mutations in the gene encoding the ATP-binding cassette transporter ABCA4. Although extensive genetic studies have identified more than 1000 mutations that cause STGD1 and related ABCA4-associated diseases, few studies have investigated the extent to which mutations affect the biochemical properties of ABCA4. The purpose of this study was to correlate the expression and functional activities of missense mutations in ABCA4 identified in a cohort of Canadian patients with their clinical phenotype.

Methods

Eleven patients from British Columbia were diagnosed with STGD1. The exons and exon-intron boundaries were sequenced to identify potential pathologic mutations in ABCA4. Missense mutations were expressed in HEK293T cells and their level of expression, retinoid substrate binding properties, and ATPase activities were measured and correlated with the phenotype of the STGD1 patients.

Results

Of the 11 STGD1 patients analyzed, 7 patients had two mutations in ABCA4, 3 patients had one detected mutation, and 1 patient had no mutations in the exons and flanking regions. Included in this cohort of patients was a severely affected 11-year-old child who was homozygous for the novel p.Ala1794Pro mutation. Expression and functional analysis of this variant and other disease-associated variants compared favorably with the phenotypes of this cohort of STGD1 patients.

Conclusions

Although many factors contribute to the phenotype of STGD1 patients, the expression and residual activity of ABCA4 mutants play a major role in determining the disease severity of STGD1 patients.

Visual Acuity Change Over 24 Months and Its Association With Foveal Phenotype and Genotype in Individuals With Stargardt Disease: ProgStar Study Report No. 10

Importance

Limited data from prospective studies are available to understand the natural history of ABCA4-related Stargardt disease (STGD1). Such data are important for determining appropriate outcome measures for future STGD1 trials.

Objective

To estimate the rate of loss of best-corrected visual acuity (BCVA) during 2 years and to estimate the associations of BCVA loss with foveal phenotype and genotype in patients with STGD1.

Design, Setting, and Participants

This multicenter prospective cohort study included 259 participants (489 study eyes) with molecularly confirmed STGD1 who were 6 years or older. The participants were enrolled at 9 centers in the United States and Europe and were followed up every 6 months for 2 years.

Exposures

Baseline BCVA and presence and type of foveal lesion (determined via fundus autofluorescence images) and genotype (classified into 4 groups based on the number and pathogenicity of ABCA4 mutations).

Main Outcomes and Measures

Rate of BCVA change per year.

Results

The mean (SD) age was 33 (15) years. Of 259 the participants, 141 (54%) were female, and 222 (85%) were white. The overall rate of BCVA loss was 0.55 (95% CI, 0.20-0.90) letters per year during the 2 years. Eyes with baseline BCVA worse than 20/200 showed an improvement of 0.65 (95% CI, 0.1-1.2) letters per year. At baseline, the mean BCVA for eyes without foveal lesion was 20/32, and their BCVA change rate over time was 0.1 (95% CI, -1.2 to 1.35) letters per year (P = .89). Eyes with a foveal lesion but having BCVA of 20/70 or better at baseline lost BCVA at a rate of 3 (95% CI, 1.5-4.4) letters per year (P < .001). Genotype was neither associated with baseline BCVA nor with the rate of BCVA change during the follow-up.

Conclusions and Relevance

A clinically small BCVA loss was observed during 2 years, and the change rate varied depending on baseline BCVA. Eyes without lesion in the fovea had better BCVA at baseline and showed minimal change of BCVA throughout 2 years. Eyes with no or modest acuity impairment but with a foveal lesion at baseline had the fastest loss rate. For trials of STGD1 with 2 years of duration, it may be difficult to show efficacy using BCVA as an end point owing to its slow rate of change over this time.

Visual Acuity Change over 12 Months in the Prospective Progression of Atrophy Secondary to Stargardt Disease (ProgStar) Study: ProgStar Report Number 6

PURPOSE

To estimate the yearly rate of change of best-corrected visual acuity (BCVA) and the risk of loss 1 line or more over 1 year and to identify risk factors for BCVA loss in patients with Stargardt disease (STGD1).

DESIGN

Multicenter, prospective cohort study.

PARTICIPANTS

Two hundred fifty-nine patients (489 eyes) with molecularly confirmed STGD1 enrolled at 9 centers in the United States and Europe.

METHODS

Participants were followed up every 6 months, and data at the baseline and 6- and 12-month visits were analyzed. Best-corrected visual acuity was measured using the Early Treatment Diabetic Retinopathy Study (ETDRS) protocol. Standardized reporting forms were used to collect participants' characteristics and clinical observations. Linear mixed effects models were used to estimate the rate of BCVA loss. Linear models with generalized estimating equations were used to identify risk factors for BCVA loss of 1 line or more over 1 year.

MAIN OUTCOME MEASURES

Change in BCVA over 1 year.

RESULTS

Cross-sectional analysis at baseline showed that earlier symptom onset and longer duration since onset was associated with worse BCVA. Longitudinal analysis showed no overall significant change of BCVA within 12 months, but the rate of BCVA change was significantly different by baseline BCVA (P < 0.001). The BCVA of eyes with baseline BCVA of 20/25 or better declined at a rate of 2.8 ETDRS letters per year (P = 0.10), eyes with baseline BCVA between 20/25 and 20/70 declined at a rate of 2.3 ETDRS letters per year (P = 0.002), eyes with baseline BCVA between 20/70 and 20/200 declined at a rate of 0.8 ETDRS letters per year (P = 0.08), and eyes with baseline BCVA worse than 20/200 showed a significant improvement of 2.3 ETDRS letters per year (P < 0.001). Overall, 12.9% of eyes lost 1 line or more, and the risk of such BCVA loss was different by baseline BCVA level (P = 0.016). Smoking and vitamin A use was not associated significantly with baseline BCVA, nor with rate of BCVA loss over 1 year.

CONCLUSIONS

Change in BCVA in STGD1 patients over a 12-month period was small, but varied depending on baseline BCVA. Given the slow change during 1 year, BCVA is unlikely to be a sensitive outcome measure for STGD1 treatment trials with 1 year's duration.

Visual Acuity Loss and Associated Risk Factors in the Retrospective Progression of Stargardt Disease Study (ProgStar Report No. 2)

PURPOSE

To examine the association between characteristics of Stargardt disease and visual acuity (VA), to estimate the longitudinal rate of VA loss, and to identify risk factors for VA loss.

DESIGN

Retrospective, multicenter cohort study.

PARTICIPANTS

A total of 176 patients (332 eyes) with molecularly and clinically confirmed Stargardt disease enrolled from the United States and Europe.

METHODS

Standardized data report forms were used to collect retrospective data on participants' characteristics and best-corrected or presenting VA from medical charts. Linear models with generalized estimating equations were used to estimate the cross-sectional associations, and linear mixed effects models were used to estimate the longitudinal VA loss.

MAIN OUTCOME MEASURES

Yearly change in VA.

RESULTS

The median duration of observation was 3.6 years. At baseline, older age of symptom onset was associated with better VA, and a longer duration of symptoms was associated with worse VA. Longitudinal analysis estimated an average of 0.3 lines loss (P < 0.0001) per year overall, but the rate varied according to baseline VA: (1) eyes with baseline VA ≥20/25 (N = 53) declined at a rate of approximately 1.0 line per year; (2) eyes with VA between 20/25 and 20/70 (N = 65) declined at a rate of approximately 0.9 lines per year; (3) eyes with VA between 20/70 and 20/200 (N = 163) declined at a rate of 0.2 lines per year; and (4) eyes with VA worse than 20/200 (n = 49) improved at a rate of 0.5 lines per year. Older age of onset was associated with slower VA loss: Patients with onset age >30 years showed 0.4 lines slower change of VA per year (P = 0.01) compared with patients with onset age ≤14 years.

CONCLUSIONS

Given the overall slow rate of VA loss, VA is unlikely to be a sensitive outcome measure for treatment trials of Stargardt disease. However, given the faster decline in younger patients and those with no or mild visual impairment, VA may be a potential outcome measure for trials targeting such subgroups of patients. These observations will need to be assessed in a prospective study bearing in mind the inherent limitations of retrospective datasets.

Fixation Improvement through Biofeedback Rehabilitation in Stargardt Disease

Stargardt disease is the most common hereditary macular degeneration in juveniles. It is characterized by macular dystrophy associated with loss of central vision in the first or second decade of life, a "beaten-metal" appearance in the fovea or parafoveal region, yellowish flecks around the macula or in posterior area of the retina, progressive atrophy of the bilateral foveal retinal pigment epithelium, and the "dark choroid" sign on fundus fluorescein angiography in most cases. We report a case of Stargardt disease in a 26-year-old Caucasian female submitted to rehabilitative training with microperimetry MP-1 to find a new preferred retinal locus (PRL) and to train her to better her quality of life. Best corrected visual acuity, mean retinal sensitivity, fixation, bivariate contour ellipse area, and speed reading were evaluated before and after the training and results were discussed.

Psychophysical measurement of rod and cone thresholds in stargardt disease with full-field stimuli

PURPOSE

To investigate psychophysical thresholds in Stargardt disease with the full-field stimulus test (FST).

METHODS

Visual acuity, spectral domain optical coherence tomography, full-field electroretinogram, and FST measurements were made in 1 eye of 24 patients with Stargardt disease. Dark-adapted rod FST thresholds were measured with short-wavelength stimuli, and cone FST thresholds were obtained from the cone plateau phase of dark adaptation using long-wavelength stimuli. Correlation coefficients were calculated for FST thresholds versus macular thickness, visual acuity, and electroretinogram amplitudes.

RESULTS

The Stargardt disease patients' FST cone thresholds correlated significantly with visual acuity, macular thickness, and electroretinogram cone response amplitudes (all P < 0.01). The patients' FST rod thresholds correlated with electroretinogram rod response amplitudes (P < 0.01) but not macular thickness (P = 0.05). All patients with Stargardt disease with flecks confined to the macula, and most of the patients with flecks extending outside of the macula had normal FST thresholds. All patients with extramacular atrophic changes had elevated FST cone thresholds and most had elevated FST rod thresholds.

CONCLUSION

Full-field stimulus test rod and cone threshold elevation in patients with Stargardt disease correlated well with measures of structure and function, as well as ophthalmoscopic retinal appearance. The Full-field stimulus test appears to be a useful tool for assessing rod and cone function in Stargardt disease.

Macular function and morphologic features in juvenile stargardt disease: longitudinal study

PURPOSE

To evaluate disease progression in a cohort of patients with a clinical and genetic diagnosis of Stargardt disease.

DESIGN

Longitudinal cohort study.

PARTICIPANTS

A total of 56 selected patients with a clinical and molecular diagnosis of Stargardt disease, an early age of onset, and a median follow-up length of 2 years.

METHODS

Patients underwent routine examination, including full-field electroretinography, microperimetry, and optical coherence tomography.

MAIN OUTCOME MEASURES

Best-corrected visual acuity (BCVA), mean retinal sensitivity, fixation stability, preferred retinal locus, inner segment/outer segment (IS/OS) junction loss, and atrophic lesion area.

RESULTS

A total of 56 patients with a mean age at disease onset of 15.3 years (range, 3-28 years), a mean disease duration of 12.1 years, and a mean age at baseline of 27.4 years were analyzed. The median BCVA was 20/200 in both eyes. Optical coherence tomography parameters (IS/OS alteration and retinal pigment epithelium lesion area) were obtained in only 49 patients because the signal quality was poor in the remaining 7 patients. Optical coherence tomography revealed a mean retinal pigment epithelium lesion area of 2.6 mm(2), preserved foveal IS/OS in 4.1% of patients, loss of foveal IS/OS in 59.2% of patients, and extensive loss of macular IS/OS in 36.7% of patients. Microperimetric findings showed a reduced macular sensitivity (mean, 10 decibels [dB]) and an unstable fixation in half of the patient cohort. The longitudinal analysis showed a significant progressive reduction of BCVA and macular sensitivity (at an estimated rate of 0.04 decimals and 1.19 dB/year, respectively) associated with a significant enlargement of retinal pigment epithelium lesion area (0.282 mm(2)/year). No significant changes in ophthalmoscopic findings and electroretinographic responses were detected.

CONCLUSIONS

This study highlights the importance of microperimetry and optical coherence tomography in monitoring patients with Stargardt disease. Quantifying the decline of visual functionality and detecting morphologic macular changes prove useful in evaluating disease progression over a short-term follow-up and should be taken into account for the design of future clinical trials of gene therapy to treat retinal dystrophy.

WITHDRAWN: Ultrastructure of the human retina in aging and various pathological states

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Natural history of phenotypic changes in Stargardt macular dystrophy

Stargardt macular dystrophy is the most common form of juvenile onset macular degeneration. This article reviews the four stages through which this dystrophy may progress. Also, reviewed here are the variations that may be observed in the visual acuity of patients with Stargardt disease.