The objective of this study is to evaluate the safety, tolerability, and efficacy of subretinal injection of NGGT001 in patients with Bietti Crystalline Corneoretinal Dystrophy (BCD) and to recommend the optimal dosage for future clinical administration.

1. Age ≥ 18 years old.
2. Male or female.
3. Confirmed diagnosis of BCD.
4. Molecular diagnosis confirmed cytochrome P450 family 4 subfamily v member 2 (CYP4V2) mutation.
5. AAV2 neutralizing antibody titer ≤1:5120.
6. 0.05 ≤ Best Corrected Visual Acuity (BCVA) ≤ 0.3.
7. -6.00D ≤ Refractive error ≤ +3.00D.
8. Agree to take contraceptive measures from the start of the study until one year after medication administration.
9. Volunteer to participate in the study and sign informed consent.

Exclusion Criteria:

1. There are choroidal neovascularization or other ocular diseases caused by BCD, which are considered to affect the operation or interfere with the interpretation of clinical endpoint.
2. Patients with evidence of neovascularization or suspected neovascularization, and the presence of tubular reflectivity in the neuroepithelial layer as shown by OCT.
3. Those who had used any of the treatment drugs within 6 months before enrollment, such as Lucentis, Avastin, Conbercept, Triamcinolone acetonide, etc. These may affect the experimental observation.
4. The treated eyes have undergone intraocular surgery, such as photodynamic therapy (PDT), vitrectomy, periocular vascular bypass surgery, etc., or need intraocular surgery in the process of clinical research, such as cataract surgery, retinal laser therapy, etc.
5. Have used or may use systemic drugs that may cause eye damage, such as psoralen, tamoxifen, etc.
6. Highly sensitive or allergic to ingredients in the test drug (with allergic history of two or more drugs or food).
7. Physical examination, vital signs, and laboratory examination (such as blood routine, urine routine, blood biochemistry, coagulation function, immunology examination, etc.) are abnormal and clinically significant, or the investigators believe that the abnormal indicators have clinical significance.
8. There are diseases or medical histories that may affect drug safety or in vivo processes, especially cardiovascular, liver, kidney, endocrine, digestive tract, lung, nerve, blood, tumor, immune or metabolic disorders considered by investigators to be of clinical significance.
9. Participated in clinical trials of other drugs or medical devices within three months before enrollment.
10. Female patients who are pregnant or lactating.
11. Any other conditions which lead the investigator to determine the participant is unsuitable for this study.