Automated Retinal Layer Segmentation in CLN2-Associated Disease: Commercially Available Software Characterizing a Progressive Maculopathy

Peripapillary Retinal Nerve Fiber Layer (pRNFL) Thickness - A Novel Biomarker of Neurodegeneration in Late-Infantile CLN2 Disease

Purpose

To investigate the presence of peripapillary retinal nerve fiber layer (pRNFL) degeneration in patients with late-infantile neuronal ceroid lipofuscinosis type 2 (CLN2) disease and to evaluate the role of optical coherence tomography (OCT) assessed pRNFL thickness as a biomarker for CLN2 disease progression.

Patients and Methods

Forty eyes of 20 patients with genetically and enzymatically confirmed diagnosis of late-infantile CLN2 disease were included in this retrospective cohort study. All patients received 300 mg of intracerebroventricular enzyme replacement treatment (cerliponase alfa) once every two weeks. OCT imaging was performed under general anesthesia using spectral domain OCT (Heidelberg Engineering, Heidelberg, Germany). PRNFL thickness and central retinal thickness (CRT) values were manually confirmed with the Heidelberg Eye Explorer software. Corresponding pediatric data were extracted from the DEM-CHILD database. Spearman correlation coefficient values (rs) were calculated between pRNFL and CRT values, age at examination, the Weill Cornell Late Infantile Neuronal Ceroid Lipofuscinosis (Weill Cornell LINCL) Scale and the Hamburg Motor and Language (HML) Scale.

Results

Fourteen of 20 patients underwent serial examinations resulting in a total of 84 OCT Scans and 42 Weill Cornell LINCL and HML Scale scores. Mean age was 6.90 years and mean follow-up time was 1.38 years. Mean global pRNFL (G-pRNFL) thickness was 77.02 μm presenting a significant decrease compared to normative values from healthy children (106.45 μm; p < 0.0001). G-pRNFL displayed significant correlations towards age at examination (rs = - 0.557, p < 0.01), the Weill Cornell LINCL Scale (rs = 0.849, p < 0.01), and the HML Scale (rs = 0.833, p < 0.01). Repeated measurements indicated decreases in pRNFL thickness over time in most patients.

Conclusion

Patients with late-infantile CLN2 disease exhibit early onset progressive pRNFL loss regardless of outer retinal degeneration, highlighting the potential of pRNFL as an independent ocular biomarker for retinal pathology in late-infantile CLN2 disease.

OCT Biomarkers in Ocular CLN2 Disease in Patients Treated With Intraventricular Enzyme Replacement Therapy

Purpose

Bilateral progressive, symmetrical loss of central retinal thickness (CRT) has been described in neuronal ceroid lipofuscinosis type 2 (CLN2) disease. This study details the pattern of morphological changes underlying CRT loss and disease progression in patients receiving intracerebroventricular (ICV) enzyme replacement therapy (ERT) with cerliponase alfa.

Methods

Spectral-domain optical coherence tomography macular cube scans were collected from 16 patients with classic CLN2 disease receiving ICV ERT. Detailed retinal structure analyses were performed on manually segmented horizontal B-scans through the fovea to determine the thickness of six retinal parameters and the extent of ellipsoid zone (EZ) loss.

Results

Anatomical changes primarily occurred in photoreceptor (PR)-related retinal parameters and correlated with ocular disease severity. Retinal degeneration began with initial focal parafoveal EZ discontinuities signaling the onset of rapid PR degeneration in a predictable pattern: parafoveal PR involvement with foveal sparing followed by profound parafoveal and foveal PR loss with additional thinning beyond the central retina. PR degeneration began with outer segment loss and progressed to outer nuclear layer (ONL) involvement. Longitudinal analyses confirmed these observations. The rate of PR loss was fastest at the fovea at ∼58 mm per year and became slower at locations farther away from the fovea.

Conclusions

Retinal degeneration in CLN2 disease is primarily associated with PR loss in a predictable pattern, with EZ disruption signaling early PR stress. CRT, ONL thickness, and PR layer thickness are useful anatomical biomarkers for understanding disease progression and treatment efficacy in CLN2. Studies using en face images will further clarify CLN2-related retinal degeneration.

Optical coherence tomography in children with inherited retinal disease

Recent advances have led to therapeutic options becoming available for people with inherited retinal disease. In particular, gene therapy has been shown to hold great promise for slowing vision loss from inherited retinal disease. Recent studies suggest that gene therapy is likely to be most effective when implemented early in the disease process, making consideration of paediatric populations important. It is therefore necessary to have a comprehensive understanding of retinal imaging in children with inherited retinal diseases, in order to monitor disease progression and to determine which early retinal biomarkers may be used as outcome measures in future clinical trials. In addition, as many optometrists will review children with an inherited retinal disease, an understanding of the expected imaging outcomes can improve clinical care. This review focuses on the most common imaging modality used in research assessment of paediatric inherited retinal diseases: optical coherence tomography. Optical coherence tomography findings can be used in both the clinical and research setting. In particular, the review discusses current knowledge of optical coherence tomography findings in eight paediatric inherited retinal diseases - Stargardt disease, Bests disease, Leber's congenital amaurosis, choroideremia, RPGR related retinitis pigmentosa, Usher syndrome, X-linked retinoschisis and, Batten disease.

Ongoing retinal degeneration despite intraventricular enzyme replacement therapy with cerliponase alfa in late-infantile neuronal ceroid lipofuscinosis type 2 (CLN2 disease)

BACKGROUND/AIMS

Late-infantile neuronal ceroid lipofuscinosis type 2 (CLN2) is a neurodegenerative, blinding lysosomal storage disorder. The purpose of the current study was to characterise the progression of CLN2-associated retinal degeneration in patients under intraventricular enzyme replacement therapy (ERT) with cerliponase alfa.

METHODS

We analysed visual function, retinal morphology and neuropaediatric data using preferential looking test (PLT), Weill Cornell Batten Scale (WCBS), optical coherence tomography (OCT) imaging and the Hamburg Motor-Language late-infantile neuronal ceroid lipofuscinosis (LINCL) Scale (M-L scale).

RESULTS

Fifty-six eyes of 28 patients had baseline PLT, WCBS and OCT. 15 patients underwent serial examinations, resulting in a total of 132 OCT scans and WCBS results, 66 Hamburg M-L scores and 49 PLT results during a mean follow-up time of 18.2 months (range 5-40). A negative correlation (r=-0.69, p<0.001) was found between central retinal thickness (CRT) values and age at examination with a maximal annual decrease of 23 µm between 56 and 80 months of age. A significant correlation was observed between PLT results and the age at examination (r=0.46, p=0.001), the WCBS scores (r=0.62; p<0.001) and CRT values (r=-0.64; p<0.001). The M-L score correlated with the ocular measurements (CRT: r=0.58, p<0.001; WCBS r=-0.64, p<0.001; PLT score: r=-0.57, p<0.001).

CONCLUSION

Despite intraventricular ERT, retinal degeneration progressed in patients with CLN2 and was particularly pronounced between 56 and 80 months of age. Retina-directed therapies should therefore be initiated before or as early as possible during the phase of rapid retinal degeneration. PLT and WCBS were identified as valuable outcome measures to monitor disease progression.

TRIAL REGISTRATION NUMBER

NCT04613089.