Effect of Branched-Chain Amino Acid Supplementation on Myopia Progression

Axial length (AL) will be measured in both eyes using optical biometry at baseline, 3 months, and 6 months. The primary outcome is the change in axial length from baseline to 6 months, comparing the BCAA supplementation plus spectacle correction group with the spectacle correction only group.

Cycloplegic spherical equivalent (SE) will be measured using autorefractometry under cycloplegia at baseline, 3 months, and 6 months. The primary outcome is the change in spherical equivalent refractive error from baseline to 6 months, comparing the BCAA supplementation group with the control group.

Superficial retinal vessel density will be measured in both eyes using OCTA in foveal, parafoveal, and perifoveal regions. Sectoral measurements (temporal, superior, nasal, and inferior) will be obtained, and the final value will be calculated as the mean of all regions, reported as a percentage (%).

Deep retinal vessel density will be measured in both eyes using OCTA across ETDRS regions. Sectoral measurements will be obtained, and the final value will be calculated as the mean of all regions, reported as a percentage (%).

Choriocapillaris perfusion will be measured in both eyes using OCTA across foveal, parafoveal, and perifoveal regions. Sectoral measurements will be obtained, and the final value will be calculated as the mean of all regions, reported as a percentage (%).

Retinal perfusion density will be measured in both eyes using OCTA across ETDRS regions, including full retinal perfusion and large-vessel-excluded perfusion. Sectoral measurements will be obtained, and the final value will be calculated as the mean of all regions, reported as a percentage (%).

Definition: Baseline refractive status of parents based on self-reported highest degree of myopia in either eye.

Variable type: Categorical Measurement: Self-reported parental myopia status categorized as none, low (≤300°), moderate (300-600°), and high (≥600°).

Definition: Baseline information on participants' use of any nutritional or dietary supplements.

Variable type: Binary (Yes/No) Measurement: Self-reported use of dietary or nutritional supplements (Yes/No).

Definition: Baseline assessment of whether participants have a documented or self-reported history of protein allergy.

Variable type: Binary (Yes/No) Measurement: Self-reported history of protein allergy (Yes/No).

Parental education level at baseline, self-reported via structured questionnaire. Education levels are categorized as: primary school or below, junior/high school, university, and master's degree or above.Variable Type：Categorical

Average daily time spent using electronic devices (including television, mobile phone, computer, and projection screen) over the past week, assessed by questionnaire. Variable type: Categorical.

Definition: Frequency of eye breaks during near work activities. Variable type: Categorical Measurement: Self-reported duration of continuous near work before rest (≤30 min, 30-60 min, 1-2 h, 2-3 h, ≥3 h).

Definition: Average daily sleep duration over the past week. Variable type: Continuous Measurement: Self-reported average sleep time (hours and minutes per day).

Frequency and quantity of staple food intake, including rice, wheat-based products, corn products, mixed beans, tubers, and fried flour-based foods, assessed using a semi-quantitative food frequency questionnaire.

Frequency and quantity of protein-rich food consumption, including soybeans and soy products, meat (pork, beef, lamb, poultry), aquatic products (fish, shrimp, shellfish), eggs, and dairy products, assessed using a semi-quantitative food frequency questionnaire.

Frequency and quantity of vegetable intake, including dark green vegetables, red/orange vegetables, purple vegetables, and light-colored vegetables, assessed using a semi-quantitative food frequency questionnaire.

Frequency and quantity of fruit intake, including pome fruits, citrus fruits, stone fruits, berries, melons, and tropical fruits, assessed using a semi-quantitative food frequency questionnaire.

Frequency and quantity of dairy product consumption, including liquid milk, milk powder, and yogurt, assessed using a semi-quantitative food frequency questionnaire.

Frequency and quantity of intake of snacks and sugary foods, including baked goods, nuts, processed snacks, sweets, and sugar-sweetened beverages, assessed using a semi-quantitative food frequency questionnaire.

Peripapillary retinal nerve fiber layer (RNFL) thickness in the temporal superior (TU) sector measured by optical coherence tomography angiography (OCTA), reported in micrometers (µm).

Peripapillary RNFL thickness in the superior temporal (ST) sector measured by OCTA, reported in micrometers (µm).

Peripapillary RNFL thickness in the superior nasal (SN) sector measured by OCTA, reported in micrometers (µm).

Peripapillary RNFL thickness in the nasal superior (NU) sector measured by OCTA, reported in micrometers (µm).

Peripapillary RNFL thickness in the nasal inferior (NL) sector measured by OCTA, reported in micrometers (µm).

Peripapillary RNFL thickness in the inferior nasal (IN) sector measured by OCTA, reported in micrometers (µm).

Peripapillary RNFL thickness in the inferior temporal (IT) sector measured by OCTA, reported in micrometers (µm).

Peripapillary RNFL thickness in the temporal inferior (TL) sector measured by OCTA, reported in micrometers (µm).

Global average peripapillary retinal nerve fiber layer (RNFL) thickness measured by optical coherence tomography angiography (OCTA), calculated as the mean thickness across all peripapillary regions, and reported in micrometers (µm).

Optic disc area measured in both eyes using optical coherence tomography angiography (OCTA), reported in square millimeters (mm²).

Neuroretinal rim area measured in both eyes using OCTA, reported in square millimeters (mm²).

Optic cup volume measured in both eyes using OCTA, reported in cubic millimeters (mm³).

Cup-to-disc ratio measured in both eyes using OCTA, defined as the ratio of optic cup diameter to optic disc diameter (unitless).

Vertical cup-to-disc ratio measured in both eyes using OCTA (unitless).

Horizontal cup-to-disc ratio measured in both eyes using OCTA (unitless).

Peripapillary microvascular vessel density in the temporal superior (TU) sector measured in both eyes using optical coherence tomography angiography (OCTA), reported as vessel density percentage (%).

OCTA-derived vessel density in the superior temporal (ST) peripapillary sector in both eyes,reported as vessel density percentage (%).

OCTA-derived vessel density in the superior nasal (SN) peripapillary sector in both eyes,reported as vessel density percentage (%).

OCTA-derived vessel density in the nasal superior (NU) peripapillary sector in both eyes,reported as vessel density percentage (%).

OCTA-derived vessel density in the nasal inferior (NL) peripapillary sector in both eyes,

OCTA-derived vessel density in the inferior nasal (IN) peripapillary sector in both eyes,reported as vessel density percentage (%).

OCTA-derived vessel density in the inferior temporal (IT) peripapillary sector in both eyes,reported as vessel density percentage (%).

OCTA-derived vessel density in the temporal inferior (TL) peripapillary sector in both eyes,reported as vessel density percentage (%).

Mean peripapillary microvascular vessel density calculated across all peripapillary sectors in both eyes using OCTA,reported as vessel density percentage (%).

Full retinal thickness in the macular region measured in both eyes using optical coherence tomography angiography (OCTA), including foveal, parafoveal, and perifoveal regions across temporal, superior, nasal, and inferior sectors.

Inner retinal layer thickness in the macular region measured in both eyes using OCTA, assessed at foveal, parafoveal, and perifoveal regions across four quadrants (temporal, superior, nasal, inferior).

Outer retinal layer thickness in the macular region measured in both eyes using OCTA, including foveal, parafoveal, and perifoveal regions across temporal, superior, nasal, and inferior sectors.

Foveal avascular zone (FAZ) area measured in both eyes using optical coherence tomography angiography (OCTA).

Perfusion density in a 300 μm annular region surrounding the FAZ in the superficial capillary plexus measured using OCTA.

Perfusion density in a 300 μm annular region surrounding the FAZ in the deep capillary plexus measured using OCTA.

Perfusion density in a 300 μm annular region surrounding the FAZ across full retinal layers measured using OCTA.

Serum alanine aminotransferase (ALT) measured in fasting venous blood using standard laboratory methods. Values will be analyzed as continuous variables and categorized as normal or abnormal based on clinical reference ranges.

Serum AST measured using standard laboratory methods in fasting venous blood. Values will be analyzed as continuous variables and categorized as normal or abnormal based on clinical reference ranges.

Serum total bilirubin measured in fasting venous blood. Values will be analyzed as continuous variables and categorized as normal or abnormal based on clinical reference ranges.

Serum creatinine measured in fasting venous blood using standard laboratory methods. Values will be analyzed as continuous variables and categorized as normal or abnormal based on clinical reference ranges.

BUN measured in fasting venous blood using standard laboratory methods. Values will be analyzed as continuous variables and categorized as normal or abnormal based on clinical reference ranges.

Serum uric acid measured in fasting venous blood using standard laboratory methods. Values will be analyzed as continuous variables and categorized as normal or abnormal based on clinical reference ranges.

Fasting plasma glucose measured in fasting venous blood using standard laboratory methods. Values will be analyzed as continuous variables and categorized as normal or abnormal based on clinical reference ranges.

Serum total cholesterol measured in fasting venous blood using standard laboratory methods. Values will be analyzed as continuous variables and categorized as normal or abnormal based on clinical reference ranges.

Serum triglycerides measured in fasting venous blood using standard laboratory methods. Values will be analyzed as continuous variables and categorized as normal or abnormal based on clinical reference ranges.

HDL cholesterol measured in fasting venous blood using standard laboratory methods. Values will be analyzed as continuous variables and categorized as normal or abnormal based on clinical reference ranges.

LDL cholesterol measured in fasting venous blood using standard laboratory methods. Values will be analyzed as continuous variables and categorized as normal or abnormal based on clinical reference ranges.

Participant sex recorded at baseline using structured questionnaire.

Age calculated from date of birth at baseline using structured questionnaire.

Ethnicity recorded at baseline using structured questionnaire.

BMI calculated from weight and height measured at baseline.Units：kg/m², Type：Continuous

Household residence (urban/rural) recorded at baseline using structured questionnaire.Type：Categorical

Annual household income recorded at baseline using structured questionnaire.Type : categorical

Self-reported level of study pressure and workload, assessed by questionnaire with four levels ranging from low to high. Variable type: Categorical.

Presence of unhealthy visual habits (e.g., reading under strong sunlight, using screens in dark environments, improper posture during near work), assessed by multiple-choice questionnaire. Variable type: Categorical (multiple response).

Lighting conditions used during near-work activities after dark (e.g., desk lamp, ceiling light), assessed by questionnaire. Variable type: Categorical.

Average daily duration of moderate-to-vigorous physical activity (e.g., brisk walking, running, jumping rope, cycling) over the past week, assessed by questionnaire. Variable type: Categorical.