Optical Coherence Tomography in Ophthalmology: Physical Principles, Image Formation, Resolution and Clinical Applications

Optical coherence tomography (OCT) enables depth-resolved imaging of tissue microstructure by measuring low-coherence interferometric signals and reconstructing their depth-dependent reflectivity. This review provides a comprehensive examination of the physical principles governing OCT and their translation into ophthalmic clinical practice. The analysis traces the modality’s evolution from time-domain detection to Fourier-domain architectures, including spectral-domain and swept-source implementations. By parallelizing depth acquisition, Fourier-domain detection provides a substantial sensitivity advantage that permits high-speed volumetric imaging and minimizes motion artifacts. We detail how the decoupling of axial and transverse resolution, governed respectively by source coherence length and numerical aperture, allows micrometer-scale axial sectioning through the low numerical aperture of the human eye. The manuscript maps these physical foundations to image formation, explaining how backscattering properties define retinal microanatomy and enable quantitative thickness measurements. We survey the clinical utility of OCT in diagnosing and managing macular disease, diabetic retinopathy, age-related macular degeneration, and glaucoma. Finally, we address inherent physical limitations, such as tissue attenuation, sensitivity roll-off, and the fundamental trade-off between transverse resolution and depth of focus. Emerging directions, including OCT angiography, enhanced depth imaging, and adaptive optics, are evaluated in the context of their underlying physics and their potential to further refine in vivo microstructural assessment. Note: All OCT images presented in this manuscript are synthetic illustrations created for educational purposes and are not derived from patient data or clinical examinations.