Effects of Differences in Body Composition on Retina and Choroid

The goal of this observational study is to examine the effects of body composition differences on retinal and choroidal structures. The study aims to investigate how variations in fat distribution and body composition parameters influence ocular microvascular structures.

The main questions it aims to answer are:

* How do differences in body composition (BMI, waist circumference, bioelectrical impedance parameters) affect retinal and choroidal microvascular structures?
* Are there significant structural changes in the retina and choroid among individuals with different body composition profiles?

Participants will:

* Be classified into five groups based on their Body Mass Index (BMI) (underweight, normal weight, overweight, obese, and severely/morbidly obese).
* Undergo detailed body composition analysis using bioelectrical impedance analysis (BIA) to assess fat mass, muscle mass, visceral fat index, and metabolic age.
* Receive comprehensive ophthalmologic evaluations, including Optical Coherence Tomography (OCT) and Optical Coherence Tomography Angiography (OCTA), to measure retinal thickness, choroidal thickness, and microvascular parameters.
* OCTA images will be analyzed using the OCTAVA software to compute vascular parameters.

This study does not involve any new treatments, drugs, or interventional procedures. The findings aim to provide insights into the relationship between body composition and ocular microvascular health, contributing to early detection and prevention strategies for obesity-related ocular complications.

Study Overview

This study is a prospective observational research planned to be conducted at Düzce University between July 1, 2024, and October 1, 2024. The aim of this study is to evaluate the potential effects of body composition differences on retinal and choroidal microvascular structures using non-invasive imaging techniques. The study is designed to investigate how obesity-related changes in fat distribution, metabolic parameters, and vascular structures may influence ocular health.

A total of 200 participants are planned to be enrolled, consisting of individuals who will visit the ophthalmology clinic for routine eye examinations and will be confirmed to have no pre-existing ocular pathologies. Participants will be classified into five groups based on Body Mass Index (BMI):

* Group 1: Underweight (BMI \<18.5)
* Group 2: Normal weight (BMI 18.5-24.9)
* Group 3: Overweight (BMI 25-29.9)
* Group 4: Obese (BMI 30-34.9)
* Group 5: Severely/Morbidly Obese (BMI \>35)

Each group is expected to include 40 participants.

Planned Study Procedures and Measurements Ophthalmologic Evaluations

All participants will undergo a comprehensive ophthalmologic examination, including:

* Autorefractometry to assess refractive errors
* Intraocular pressure (IOP) measurement using a non-contact tonometer
* Detailed slit-lamp biomicroscopy to examine anterior and posterior segment structures Body Composition Analysis
* Bioelectrical Impedance Analysis (BIA) will be performed to assess:
* Total body fat percentage, visceral fat index, muscle mass, and metabolic age
* Segmental body composition (fat and muscle mass in arms, legs, and trunk)
* Extracellular and intracellular water distribution
* Waist circumference, waist-to-hip ratio, waist-to-height ratio OCT and OCTA Imaging
* Optical Coherence Tomography (OCT) and Enhanced Depth Imaging-OCT (EDI-OCT) will be used to obtain:
* Macular and peripapillary retinal thickness measurements
* Retinal nerve fiber layer (RNFL) thickness
* Optic disc and cup-to-disc ratio analysis
* Choroidal thickness at the subfoveal region and 500 µm intervals
* Optical Coherence Tomography Angiography (OCTA) will be performed to analyze:
* Superficial and deep retinal capillary plexus vascular density
* Foveal avascular zone (FAZ) area, perimeter, and circularity
* Vascular tortuosity and branchpoint density Image Processing and Analysis
* OCTA images will be analyzed using the OCTAVA software, where:
* Vessel area density, vessel length density, total vessel length, mean vessel diameter, median vessel diameter, branchpoint density, fractal dimension, and vessel tortuosity will be calculated.
* FAZ metrics (FAZ area, perimeter, and circularity) and vascular density values will be evaluated using ETDRS grid segmentation and FD-300 analysis.
* Choroidal Vascularity Index (CVI) will be calculated from EDI-OCT images using ImageJ software.

Study Objectives and Clinical Significance

This study aims to determine the relationship between body composition differences and retinal/choroidal microvascular changes to better understand how systemic metabolic alterations influence ocular structures. The results are expected to contribute to:

* Identifying early ocular biomarkers associated with obesity
* Developing preventive strategies for obesity-related retinal and choroidal complications
* Enhancing the clinical use of non-invasive imaging techniques in metabolic disease monitoring No new treatment, drug, or interventional procedure is planned to be applied in this study, and no life-threatening risks are anticipated.

Eligibility Criteria:
Inclusion Criteria:

* Age between 18 and 65 years,
* No detected pathology in routine ophthalmologic examination,
* Providing written informed consent for participation.

Exclusion Criteria:

* Presence of ocular diseases such as glaucoma, uveitis, diabetic retinopathy, amblyopia, or retinal vein occlusion,
* History of previous ocular surgery,
* Refractive error exceeding ±4 diopters,
* Use of medications that may affect choroidal or retinal vascular structures,
* Pregnancy or breastfeeding,
* Presence of metallic prostheses, pacemakers, or other implants that could interfere with body composition analysis.