Proptosis assessment using Hertel exophthalmometry is an essential part of the ophthalmic examination, but normal reference values vary among different populations. This observational study aims to establish normative Hertel exophthalmometry values in Mexican adults and to evaluate their association with demographic characteristics (such as age and sex) and systemic diseases. Healthy adult participants and adults with selected systemic conditions will undergo standardized Hertel exophthalmometry measurements. The findings are expected to provide population-specific reference values that may improve the clinical assessment of orbital diseases in the Mexican population.

Background: Hertel exophthalmometry is the most commonly used method for measuring globe protrusion in clinical practice. Normal exophthalmometric values vary according to ethnicity, sex, age, and craniofacial anatomy; therefore, population-specific reference values are necessary for accurate clinical interpretation. Currently, normative data for Mexican adults are limited.

Objective: To establish normative Hertel exophthalmometry values in Mexican adults and to evaluate their association with demographic characteristics and systemic diseases.

Methods: This is a prospective observational study. Adult participants attending the Ophthalmology Department will be consecutively recruited after providing written informed consent. Hertel exophthalmometry measurements will be obtained using a standardized technique by trained examiners. Demographic information, including age and sex, as well as relevant medical history and systemic diseases, will be recorded. The primary outcome is the distribution of Hertel exophthalmometry values in the study population. Secondary analyses will assess associations between exophthalmometric measurements and demographic or systemic variables.

Expected Significance: The study will provide normative Hertel exophthalmometry values for the Mexican adult population and identify factors associated with physiological variations in globe protrusion. These findings may improve the clinical evaluation of patients with suspected orbital disease and facilitate interpretation of Hertel exophthalmometry measurements in routine ophthalmic practice.

Inclusion Criteria:

• Adults aged 18 years or older.
• Mexican participants or individuals who self-identify as Mexican.
• Ability to understand the study procedures and provide written informed consent.
• Ability to undergo bilateral Hertel exophthalmometry.
• Participants with or without previously diagnosed systemic diseases.

Exclusion Criteria:

• Active thyroid eye disease
• History of orbital trauma or orbital fracture.
• Previous orbital surgery, orbital decompression, or surgery that may alter globe position.
• Presence or history of an orbital tumor, orbital inflammation, or orbital infection.
• Craniofacial abnormalities or facial asymmetry that may interfere with Hertel exophthalmometry.
• Ocular or eyelid conditions that prevent accurate positioning or measurement with the Hertel exophthalmometer.
• Inability to cooperate with the examination or obtain a reliable exophthalmometry measurement.

Adult Mexican participants (≥18 years) recruited from the Ophthalmology Department who meet the eligibility criteria. Participants with and without systemic diseases will be included to establish normative Hertel exophthalmometry values and evaluate their association with demographic characteristics and systemic conditions.