This study is a multicenter, randomized, double-blind, placebo-controlled, superiority design Phase III clinical trial. The primary objective is to evaluate the efficacy and safety of cyclosporine ophthalmic gel versus placebo in the treatment of moderate to severe dry eye for 84 days.

A total of 360 subjects are planned to be enrolled in this study. This study is divided into two stages. The first stage (double-blind treatment period) is the main efficacy and safety evaluation stage, which lasts for 84 days. During this period, subjects are randomly assigned to receive the experimental drug or control drug in a 1:1 ratio, with the analysis of the first stage as the main analysis. After completing the 84th day visit, the subjects will enter the second stage (open treatment period). The second stage is a safety observation period of 84 days, during which all subjects use the experimental drug.

Inclusion Criteria:

1. aged ≥ 18 years old, males or females.

2. Subjects complained of ocular dryness in both eyes for at least 6 months at Visit 1.

3. Eye dryness score(EDS)(evaluated on a 0-100 VAS score) ≥40 at Visit 1 and Visit 2.

4. Ocular Surface Disease Index (OSDI) score ≥13 at Visit 1 and Visit 2.

5. Total corneal fluorescein staining score (tCFS) ≥2 in either eye and ≥1 in at least one region at Visit 1 and Visit 2.

6. Schirmer I test (without anesthesia) ≤ 5 mm/5 min in either eye at Visit 1 and Visit 2.

7. Subjects with moderate and severe dry eye in both eyes at Visit 1 and Visit 2:

   1. Moderate: ≥1 quadrant and no more than 2 quadrants of corneal damage and/or ≥5 and <30 corneal fluorescein staining spots on slit lamp microscopy;
   2. Severe: ≥2 quadrants of corneal damage and/or ≥30 corneal fluorescence staining spots on slit lamp microscopy.

Exclusion Criteria:

1. Subjects with severe dry eye requiring surgical treatment.
2. Systemic use of retinoids within the 12 months prior to Visit 1.
3. Subjects who have had intraocular surgery within 12 months prior to Visit 1 or who require intraocular surgery during the study; or subjects who have had eyelid surgery within 6 months prior to Visit 1.
4. Subjects treated with permanent lacrimal duct embolization; or subjects treated with temporary lacrimal duct embolization within 6 months prior to Visit 1.
5. Subjects with dry eye correlated with operation；
6. Subjects who had worn corneal contact lens within 3 months prior to Visit 1.
7. Those who have used cyclosporine preparations ocularly or systemically within 1 month prior to visit 1.
8. Those who have used lifitegrast eye drops or tacrolimus eye drops ocularly within 1 month prior to visit 1.
9. Subjects with dry eye secondary to scarring (e.g., radiation exposure, ocular chemical burns, Stevens-Johnson syndrome, keloid pemphigoid, conjunctival scarring) or severe conjunctival cup cells destruction (e.g., vitamin A deficiency).
10. Those with significant eyelid margin inflammation or meibomian gland dysfunction that, in the opinion of the investigator, may affect the outcome of the trial.