Ace the COT Challenge 2026 – Shine Bright as a Certified Ophthalmic Technician!

Red-free photography is utilized to enhance the visibility of certain structures of the retina by using a special green filter that reduces the brightness of red blood cells. In this method, hemoglobin in the blood will absorb the green light, causing the veins and arteries to appear dark or black, while the optic nerve head, which contains less vascularization and has a different reflectivity, appears white. This contrast allows for better assessment of the structures, making it particularly effective in identifying abnormalities in the vascular system of the eye.

The other options present distinct methodologies that do not produce this specific visual outcome. While color photography captures images in a wide spectrum of color, including red hues, it does not enhance the contrast between vessels and the optic nerve in the same way. Infrared photography, on the other hand, functions differently by capturing longer wavelengths of light, which can show different vascular patterns but does not give the same clear distinction of black and white as red-free photography does. Additionally, blue filter photography primarily emphasizes blue light reflections and is not designed to provide the same contrast in blood vessel visibility.