OCT-Based Screening for Early Retinal Changes in Asymptomatic Diabetic Patients

Diabetic retinopathy is a leading cause of vision impairment worldwide. Even in the absence of visual symptoms, patients with diabetes may already have early structural retinal changes that can be detected only with advanced imaging. Identifying these changes at an early stage is essential to prevent progression to vision-threatening complications.

This observational cross-sectional study aims to evaluate the role of Optical Coherence Tomography (OCT) and fundus examination in detecting early retinal changes among diabetic patients with no visual complaints. The study will be conducted at the Ophthalmology Department, Assiut University Hospitals, Egypt.

Eligible participants will include individuals with a confirmed diagnosis of type 1 or type 2 diabetes mellitus for at least six months, best-corrected visual acuity of 6/6, clear ocular media, and no clinical evidence of retinal disease. A control group of healthy subjects with normal ocular findings will also be included for comparison.

All participants will undergo a complete ophthalmic assessment that includes:

Medical and ocular history, including diabetes duration and systemic status.

Visual acuity measurement (uncorrected and best-corrected) using the Snellen chart.

Anterior segment evaluation by slit-lamp biomicroscopy.

Fundus examination using slit-lamp biomicroscopy.

Spectral-domain OCT macular scanning (NIDEK RS-330, Japan) for assessment of macular thickness and retinal layer structure.

Data will be analyzed using SPSS software (Version 16). Quantitative variables will be expressed as mean ± standard deviation and compared using appropriate statistical tests. Correlations between OCT parameters, disease duration, and HbA1c levels will be evaluated.

The study is non-interventional and poses no significant risk to participants, as it involves only routine, non-invasive ophthalmic imaging. The findings are expected to improve early detection strategies for diabetic retinal changes and support the use of OCT and fundus examination as effective screening tools in routine diabetic eye care.

The estimated sample size will include approximately 112 participants (56 diabetic patients and 56 healthy controls).

Inclusion criteria

• Confirmed diagnosis of type 1 or type 2 diabetes mellitus for at least 6 months
• Best-corrected visual acuity (BCVA) of 6/6 using Snellen chart
• No visual symptoms (no blurred vision or metamorphopsia)
• Clear ocular media allowing high-quality OCT imaging
• No significant abnormalities on fundus examination
• Intraocular pressure (IOP) below 21 mmHg
• Willing and able to provide written informed consent

Exclusion criteria

• History of previous macular disease or treatment (laser photocoagulation or intravitreal injection)
• Media opacity that prevents adequate OCT imaging (e.g., dense cataract, corneal opacity)
• Presence of other retinal diseases (e.g., age-related macular degeneration, retinal vein occlusion)
• Systemic or neurological diseases that affect the retina or visual pathway
• Uncooperative participants or those who decline to give consent