Clinical Features of Optic Disc Drusen in an Ophthalmic Genetics Cohort

Association of optic disc drusen and small scleral canals - A systematic review and meta-analysis

The pathophysiology of optic disc drusen (ODD) has long been discussed. According to one leading theory, they develop from calcified mitochondria extruded from axons compressed by an unusually small scleral canal. To examine this hypothesis, we conducted a systematic review and meta-analysis evaluating the scleral canal size in patients with ODD (PO) in comparison to healthy subjects (HS). We searched MEDLINE, Cochrane Central, EMBASE and gray literature to identify relevant articles. A subgroup analysis compared patients with buried ODD (POb) and patients with visible ODD (POv). The study was registered with the International Prospective Register of Systematic Reviews on December 9th, 2022 (Registration: CRD42022375110). We included fifteen articles in the review and fourteen in the meta-analysis. The mean diameter of the scleral canal computed using both fundus photography (DF) and spectral-domain with enhanced depth imaging optical coherence tomography (DO-EDI) was significantly smaller in PO compared to HS (standardized mean difference -1.21 [-1.85 to -0.56] and -0.66 [-0.94 to -0.37] respectively). DO-EDI, but not DF, was higher in POv as compared to POb. When including all-generation OCT in the analysis, the difference between POv and POb, but not between PO and HS, remained. Several intertwined hypotheses can explain these subgroup and sensitivity results: an enlargement of the canal as the ODD grow, an enlargement with time, or a measurement bias (artefactual enlargement of the canal due to a posterior shadow on OCT). In conclusion, this review and meta-analysis further supports the role of a small scleral canal in the development of ODD.

Optic Disc Drusen Prevalence in Patients With Retinitis Pigmentosa: A Cross-Sectional Study

BACKGROUND

Studies of patients with retinitis pigmentosa (RP) have reported an increased prevalence of optic disc drusen (ODD) compared with the ODD prevalence in the general population. The diagnostic gold standard method for identifying ODD is enhanced depth imaging optical coherence tomography (EDI-OCT), but this modality has not previously been used systematically for identifying ODD in patients with RP. This study aimed to estimate the prevalence of ODD in patients with RP using EDI-OCT.

METHODS

In this cross-sectional study, 40 patients with clinically diagnosed RP aged 18 years or older were included. All patients underwent an ophthalmic examination, including kinetic perimetry, EDI-OCT of the optic nerve head, and fundus photography. Genetic testing with a next-generation sequencing panel of retinal dystrophy genes was performed on the RP patients without a prior genetic diagnosis.

RESULTS

Twelve patients (30.0%) had at least one ODD. Six patients had bilateral ODD. No significant differences between patients with and without ODD were found according to age, refraction, best-corrected visual acuity, Bruch membrane opening, or visual field. The genetic variation causing RP was found in 11 of 12 cases in the ODD group and in 17 of 28 cases in the group without ODD.

CONCLUSIONS

We found the prevalence of ODD in patients with RP to be 30.0%. This is 15 times higher than in the general population and much higher than previously estimated in most studies, potentially indicating that the 2 conditions might be pathogenically related.

Optic disc drusen and scleral canal size - protocol for a systematic review and meta-analysis

Background

Around one in forty patients are diagnosed with optic disc drusen (ODD) during their lifetime. Complications of these acellular deposits range from asymptomatic visual field deficits to artery occlusion and subsequent cecity. Still, the pathogenesis of their emergence remains controversial. In particular, it was suggested 50 years ago that a narrow disc and scleral canal is one factor leading to axoplasmic flow disturbance, which induces ODD formation. However, this hypothesis is still debated today. To evaluate the basis of this theory, we will conduct a systematic review and meta-analysis of studies evaluating the scleral canal size in patients with ODD and in healthy subjects.

Methods

We will search MEDLINE via PubMed, Cochrane, and EMBASE electronic databases to identify articles published before November 29, 2022 that measure the scleral canal size in patients with ODD and in healthy subjects. In addition, grey literature will be searched. The meta-analysis will include studies that include patients with a clinical or imaging diagnosis of ODD and healthy subjects. Additionally, we will perform a subgroup analysis to compare patients with buried ODD and patients with visible ODD. Extracted data from included studies will be presented descriptively, and effect sizes will be computed based on the recommendations from the Cochrane Collaboration handbook.

Discussion

The hypothesis that a narrow scleral canal is a risk factor of ODD has long been debated and this systematic review and meta-analysis should disentangle the different views. Understanding the underlying factors driving the development of ODD should help us focus on patients at risk and develop strategies to prevent advanced stages of the disease in these patients. Besides, focusing on patients with small scleral canals should help us derive associated factors and provide a better understanding of the pathology.

Systematic review registration

https://www.crd.york.ac.uk/prospero/display_record.php?ID=CRD42022375110.

Natural history and biomarkers of retinal dystrophy caused by the biallelic TULP1 variant c.148delG

PURPOSE

To report clinical features and potential disease markers of inherited retinal dystrophy (IRD) caused by the biallelic c.148delG variant in the tubby-like protein 1 (TULP1) gene.

METHODS

A retrospective observational study of 16 IRD patients carrying a homozygous pathogenic TULP1 c.148delG variant. Clinical data including fundus spectral-domain optical coherence tomography (SD-OCT) were assessed. A meta-analysis of visual acuity of previously reported other pathogenic TULP1 variants was performed for reference.

RESULTS

The biallelic TULP1 variant c.148delG was associated with infantile and early childhood onset IRD. Retinal ophthalmoscopy was primarily normal converting to peripheral pigmentary retinopathy and maculopathy characterized by progressive extra-foveal loss of the ellipsoid zone (EZ), the outer plexiform layer (OPL), and the outer nuclear layer (ONL) bands in the SD-OCT images. The horizontal width of the foveal EZ showed significant regression with the best-corrected visual acuity (BCVA) of the eye (p < 0.0001, R²  = 0.541, F = 26.0), the age of the patient (p < 0.0001, R²  = 0.433, F = 16.8), and mild correlation with the foveal OPL-ONL thickness (p = 0.014, R²  = 0.245, F = 7.2). Modelling of the BCVA data suggested a mean annual loss of logMAR 0.027. The level of visual loss was similar to that previously reported in patients carrying other truncating TULP1 variants.

CONCLUSIONS

This study describes the progression of TULP1 IRD suggesting a potential time window for therapeutic interventions. The width of the foveal EZ and the thickness of the foveal OPL-ONL layers could serve as biomarkers of the disease stage.