Spectral domain OCT commonly uses which wavelength?

Spectral domain OCT commonly uses which wavelength?

• A. 550 nm
• B. 840 nm
• C. 1064 nm
• D. 1310 nm

Answer: (B)

Spectral-domain OCT uses a broadband near-infrared light source, and 840 nm sits in the sweet spot for retinal imaging. This wavelength balances how light interacts with tissue: it penetrates the ocular media well enough to resolve retinal layers with good contrast, while keeping scattering and absorption at manageable levels so images stay sharp. Shorter visible wavelengths (like 550 nm) scatter a lot in tissue and don’t reach deeper structures effectively, whereas longer wavelengths (around 1064 or 1310 nm) are used in other OCT platforms or for deeper or different tissue applications but aren’t the standard in most ophthalmic spectral-domain systems. The 840 nm range is a common, practical choice that works well with the detectors and spectrometers used in SD-OCT, producing good axial resolution and image quality.

Spectral-domain OCT uses a broadband near-infrared light source, and 840 nm sits in the sweet spot for retinal imaging. This wavelength balances how light interacts with tissue: it penetrates the ocular media well enough to resolve retinal layers with good contrast, while keeping scattering and absorption at manageable levels so images stay sharp. Shorter visible wavelengths (like 550 nm) scatter a lot in tissue and don’t reach deeper structures effectively, whereas longer wavelengths (around 1064 or 1310 nm) are used in other OCT platforms or for deeper or different tissue applications but aren’t the standard in most ophthalmic spectral-domain systems. The 840 nm range is a common, practical choice that works well with the detectors and spectrometers used in SD-OCT, producing good axial resolution and image quality.