Atropine has a ciliary muscle-paralysing effect and causes hyperopic drift. Besides, atropine has been proven to slow the progression of myopia. Many studies have suggested that atropine can increase the thickness of the choroid. However, few studies have discussed changes in the ciliary muscle after treatment with atropine or other cycloplegic agents.

This study aimed to assess the difference in ciliary muscle morphology before and after two different cycloplegic agents and to analyze the correlation between the changes of ciliary muscle biological parameters and the changes of eye axis, spherical equivalent, lens diopter, choroidal thickness, etc. One hundred and forty-four children would be randomly assigned 1:1 to the 1% atropine group and the tropicamide group. This study might provide clinical evidence for the role of regulatory factors in the occurrence and development of myopia.

The ciliary muscle exhibited an inward-forward contraction during accommodation, resulting in a significant thickening of the anterior area of the ciliary muscle. In addition to ultrasound biomicroscope (UBM), anterior segment optical coherence tomography (AS-OCT) is also commonly used to study morphological changes in the ciliary muscle. Studies using AS-OCT revealed that the posterior area of the ciliary muscle thinned during accommodation.

The morphology of the ciliary muscles differs in individuals with refractive errors. Many researchers found that the ciliary muscle became thicker with an increase of axial length (AL) Some studies suggested that myopia primarily affected the posterior area of the ciliary muscle.

Atropine has a ciliary muscle-paralysing effect and causes hyperopic drift. Besides, atropine has been proven to slow the progression of myopia. Many studies have suggested that atropine can increase the thickness of the choroid. However, few studies have discussed changes in the ciliary muscle after treatment with atropine or other cycloplegic agents.

This study aimed to assess the difference in ciliary muscle morphology before and after two different cycloplegic agents and to analyze the correlation between the changes of ciliary muscle biological parameters and the changes of eye axis, spherical equivalent, lens diopter, choroidal thickness, etc. One hundred and forty-four children would be randomly assigned 1:1 to the 1% atropine group and the tropicamide group. This study might provide clinical evidence for the role of regulatory factors in the occurrence and development of myopia.

Inclusion Criteria:

• ①Age 3 to 12 years old;

  • Astigmatism <2.00D, binocular anisometropia <3.00D, and the best corrected distance visual acuity is at least 0.8, near vision at least 0.8;

    • A clear anterior segment image can be obtained through anterior segment OCT;

      • Have normal thinking and language communication skills, and can actively cooperate with the inspection process; ⑤ No contraindications to atropine treatment such as acute eye inflammation, dry eye, keratoconus, diabetes, etc.; ⑥Written informed consent of the guardian and the child himself

Exclusion Criteria:

• ① Combined with neurological diseases and have allergies or contraindications to cycloplegic drugs or other drugs;

  • Intraocular pressure ≥21mmHg; history of photosensitivity, glaucoma, blue eye syndrome, ocular hypertension, and retinal macular lesions or damage;

    • Patients with chronic eye diseases such as ocular trauma and allergic conjunctivitis;

      • Those who wear contact lenses and those who use myopia control-related drugs within 1 month; ⑤ Patients with previous varus trichiasis, severe horn, conjunctiva infection and other eye diseases;

        • Insufficient image quality, such as inconsistent field of view, poor image exposure, inaccurate image focus, stains, shadows or crescent shadows, etc.;

          • There are systemic diseases; ⑧ Epilepsy, mental disorders unable to communicate normally; ⑨ Other circumstances judged by the investigator to be unsuitable to participate in the research