Many individuals undergoing cataract surgery report seeing various colors or lights during the procedure. This experience, while often surprising, is a normal physiological response and not a cause for concern. Patients are typically awake during cataract surgery, with the eye numbed by local anesthesia, allowing them to perceive these visual phenomena without discomfort. This common occurrence stems from how the eye and brain process non-light stimuli into perceived images.
The Phenomenon of Phosphenes
The visual sensations experienced during cataract surgery are a type of phosphene. A phosphene is the perception of light or colors without actual light entering the eye. This phenomenon occurs when the retina, the light-sensitive tissue at the back of the eye, or the visual pathways in the brain are stimulated by means other than light. These internal stimuli can cause the cells in the retina to activate, sending signals to the brain that are then interpreted as visual impressions.
Phosphenes can be induced through various mechanisms, including mechanical pressure, electrical signals, or even magnetic fields. For instance, rubbing closed eyes can trigger pressure phosphenes, leading to perceptions of swirling colors or bright shapes. The cells of the retina respond to these non-photonic stimuli by generating neural impulses, which the brain’s visual cortex processes as if they were actual light. This explains why colors and patterns are seen even when the eye is covered or closed.
How Surgical Procedures Elicit Visual Sensations
During cataract surgery, specific actions and tools can inadvertently stimulate the eye, leading to phosphenes. Pressure applied to the eye, for example, from the eye speculum used to keep the eyelids open or from the surgeon’s instruments, can mechanically stimulate the retina. This mechanical stimulation activates retinal cells, causing the perception of light or colors. The bright light from the operating microscope, although directed at the eye, can also contribute to these visual experiences.
Even with the eye covered or closed, intense light from the microscope can penetrate the eyelid and stimulate the retina. The movement of fluids, such as balanced salt solution, used for irrigation within the eye during surgery, can also create mechanical stimulation. While less common for vivid colors, minor electrical impulses from certain instruments might also contribute to these perceptions.
Common Visual Experiences During Surgery
Patients undergoing cataract surgery frequently describe seeing a range of colors, including blue, red, pink, yellow, and green. These colors often appear as bright flashes, vague shapes, or swirling patterns. The specific hues and patterns can vary from person to person, influenced by individual retinal sensitivity and the exact nature of the stimulation.
These visual sensations are temporary and typically subside shortly after the procedure is completed. The experience is usually not painful and, for many, can even be described as pleasant or calming.