Iris Color and Day-Night Changes in the Sympathovagal Ratio

Status

Completed

Phases

Unknown

Study type

Observational

Source

ClinicalTrials.gov

Registry ID

NCT05759715

Enrollment

621

Registered

2023-03-08

Start date

2016-05-05

Completion date

2022-06-30

Last updated

2023-03-09

For informational purposes only — not medical advice. Sourced from public registries and may not reflect the latest updates. Terms

Conditions

Iris Diseases

Keywords

LF/HF ratio, iris color, melanin

Brief summary

Iris melanocytes are innervated by parasympathetic and sympathetic nerve endings. Light affects autonomic nervous system activity via the retino-hypothalamic pathway. The hypothesis that the day-to-night variations in the sympatovagal ratio (LF/HF) may differ among individuals with different brown iris patterns was tested.

Detailed description

A total of 621 healthy adults, aged between 16 and 50, with brown eyes and not diagnosed with a disease that might affect the autonomous nerve system were included in the study. A digital camera was used to acquire iris photos. Subjects were grouped into iris color groups (2-0 bg, 1-0 bg, 1-1 db, 1-1 lb, 2-0 b, and 1-0 b). Iris photos were analyzed with Picture Color Analyzer RBG software. The Central/Peripheral (R/RGB) ratio was used for objective distinction between the groups. Using 24-h Holter ECG monitoring, the change in the sympathovagal ratio from day (between 07:00 and 23:00 hrs) to night (between 23:00 and 07:00 hrs) was determined with the formula \[(Day - Night) LF/HF)/Day LF/HF\].

Interventions

OTHERIris Color Measurement , LF/HF Measurement

Iris Color Measurement (Photos were taken of the iris with a digital camera ) LF/ HF Measurement (Using the three-channel standard ambulatory Holter recording system)

Study design

Observational model

COHORT

Time perspective

CROSS_SECTIONAL

Eligibility

Sex/Gender

ALL

Age

16 Years to 50 Years

Inclusion criteria

A total of 650 healthy individuals between the ages of 16 and 50 .

Exclusion criteria

Diseases that could affect the autonomic nervous system; Obesity Obstructive sleep apnea syndrome Hypertension Diabetes mellitus Atrial fibrillation Coronary disease Heart failure Goiter, etc.

Design outcomes

Primary

Measure	Time frame	Description
LF/HF ratio	one week	low frequency (LF, 0.04-0.15 Hz) and high frequency (HF, 0.16-0.4 Hz) measurements were taken from day and night changes in the heart rate by using the frequency-domain analysis method.

Outcome results

None listed

Source: ClinicalTrials.gov · Data processed: Feb 4, 2026