1. Structure: Fly eyes are compound eyes, while human eyes are simple eyes. Compound eyes consist of numerous tiny individual units called ommatidia, each of which functions as a separate receptor for light. In contrast, human eyes have a single lens that focuses light onto a retina containing specialized photoreceptor cells.
2. Number of photoreceptors: Fly eyes have a much larger number of photoreceptors compared to human eyes. While humans have about 6-7 million cones (color-detecting cells) and 120 million rods (low-light-sensitive cells) in each retina, flies can have several thousand ommatidia in each compound eye. This difference gives flies a wider field of view, greater sensitivity to movement, and the ability to detect objects from a greater distance.
3. Image formation: Human eyes form a detailed, high-resolution image of the visual world on the retina, which is then transmitted to the brain for processing. In contrast, compound eyes produce mosaic-like images, with each ommatidium contributing a small piece of the overall visual field. This results in a lower-resolution image, but it allows flies to process visual information more rapidly and efficiently, particularly for detecting motion.
4. Motion detection: Fly compound eyes are highly specialized for detecting and tracking moving objects. The arrangement of the ommatidia in the eye allows flies to perceive rapid changes in the visual environment, making them excellent at navigating and catching prey in flight. In comparison, human eyes have specialized neurons in the retina that process motion information, but their visual acuity for motion is not as refined as that of flies.
5. Color perception: Human eyes can perceive a wide range of colors due to the presence of specialized cone cells that are sensitive to different wavelengths of light. In contrast, fly compound eyes typically have a limited number of photoreceptor types (usually three to five), which restricts their color perception. However, some fly species have color vision capabilities that allow them to differentiate between certain colors, such as red, green, and ultraviolet light.
Despite these differences, both fly eyes and human eyes serve the essential purpose of converting light into electrical signals that can be processed by the brain to provide a sense of vision and interact with the environment.