Why this case matters
For people with Leber congenital amaurosis type 2 (LCA2) caused by disease-causing changes in both copies of the RPE65 gene, difficulty seeing in dim light—also called nyctalopia or night blindness—can be a major part of daily life. Voretigene neparvovec (VN; Luxturna) is an AAV2-mediated gene therapy and remains the only approved treatment for inherited retinal disease associated with biallelic RPE65 variants.
A 2026 case report in Frontiers in Pharmacology describes the first patient in mainland China with compound heterozygous RPE65-associated LCA2 to receive this treatment. The report follows a Han Chinese child for up to 22 months after sequential injections beneath the retina in each eye. While this is only one patient, the study provides an important long-term look at how treatment may affect dark-adapted vision, visual acuity, and retinal findings in a population that has been underrepresented in published VN reports.
Measuring the vision that matters in low light
Standard eye charts assess best-corrected visual acuity (BCVA): the ability to resolve fine detail under well-lit testing conditions. But acuity does not fully capture the challenges faced by people with LCA2, especially when moving through dark rooms, outdoors at dusk, or in other low-light settings.
The researchers therefore used full-field stimulus threshold (FST) testing. FST measures how dim a flash of light can be before a person can detect it after adapting to darkness. Better sensitivity means the person can detect dimmer light.
The patient showed improvement in binocular FST results at 3, 6, and 22 months after treatment. The improvement persisted at the longest follow-up visit, indicating a sustained gain in dark-adapted visual function over nearly two years.
The team also used chromatic threshold difference analysis, which compares responses to lights of different colors. This analysis supported the conclusion that the improvement was predominantly rod-mediated. Rod photoreceptors are especially important for vision in very low light, making this finding particularly relevant to the night-vision difficulties commonly associated with RPE65-related LCA2.
Improved dark adaptation, but not visual acuity
A central finding of the case is that better dark-adapted sensitivity did not translate into improved BCVA. At 22 months, the patient continued to show persistent improvement in dark-adapted function, but not in best-corrected visual acuity.
This distinction is valuable for families and clinicians considering how treatment outcomes are assessed. A person may notice meaningful changes in their ability to function in dim environments even if their letter-chart score does not change. In this child, the authors reported an obvious improvement in nyctalopia after early gene therapy, consistent with the objective FST findings.
The report therefore reinforces the importance of measuring more than visual acuity in LCA2 studies and clinical care. Tests that evaluate light sensitivity and dark-adapted vision may be better able to detect treatment-related changes that matter in everyday life.
Retinal changes require continued study
The patient had no treatment-related adverse events noted at the 3-month visit. However, at 6 months, clinicians detected chorioretinal atrophic lesions in both eyes. These were classified as treatment-emergent ocular findings, meaning they appeared after treatment. The lesions had enlarged by the 22-month follow-up.
Importantly, the report states that their causal relationship to the gene therapy was undetermined. The case cannot establish whether the lesions were caused by VN, related to the underlying retinal disease, or reflected another factor. Still, their appearance and progression underscore why detailed retinal imaging and long-term follow-up are essential after subretinal gene therapy.
What this means for treatment research
This report adds evidence that VN can produce sustained improvement in dark-adapted, rod-dominant visual function in a Han Chinese child with biallelic RPE65-associated LCA2. It also highlights the potential value of intervention early in life, since the authors observed improved nyctalopia after early treatment.
At the same time, the study has important boundaries. It is a single case, and its FST measurements were binocular, integrated results. Because both eyes were tested together, the researchers could not separate the contribution of each eye or directly assess monocular function. The findings also cannot determine how consistently similar benefits or retinal changes may occur across other patients.
Future controlled cohort studies that include more Han Chinese participants will be needed to examine whether early treatment more reliably provides substantial relief from nyctalopia, how long low-light benefits persist, and how treatment-emergent retinal findings should be interpreted.
Looking ahead
This case offers a hopeful but careful picture of gene therapy in LCA2. It shows that success may be reflected in a child’s ability to detect light and navigate darkness—not only in visual-acuity measurements. As longer-term studies expand to include more genetically and geographically diverse participants, researchers will be better positioned to define who benefits most, which outcomes best reflect meaningful vision, and how to monitor retinal health after treatment.