Radial Keratotomy (RK) is a type of refractive eye surgery designed to correct vision. It emerged as an early form of surgical intervention aimed at reducing a person’s dependence on glasses or contact lenses. The procedure’s primary purpose was to reshape the cornea, the clear front surface of the eye, to improve how light focused on the retina. It offered a surgical alternative when other modern procedures were not yet available.
Understanding the Surgical Technique
Radial Keratotomy involved making precise incisions in the cornea to alter its curvature. These incisions were radial, resembling the spokes of a wheel, and did not extend into the central optical zone. A specialized diamond knife created these cuts.
The number and depth of these incisions varied depending on the individual’s prescription and the desired amount of vision correction. Typically, between 4 and 24 radial incisions were made, often reaching a depth of 80% to 90% of the corneal thickness. These cuts weakened the corneal structure, causing the central cornea to flatten. This flattening effect was intended to correct the eye’s focusing power.
Why RK Was Performed
RK was developed to address myopia, commonly known as nearsightedness. In myopic eyes, the cornea is typically too steeply curved, or the eyeball is slightly too long, causing light rays to focus in front of the retina, resulting in blurred distance vision. By flattening the central cornea, RK aimed to shift this focal point directly onto the retina, thereby sharpening distant vision.
Before the widespread availability of laser-based vision correction, RK offered a surgical solution for those seeking to reduce their reliance on corrective eyewear. It was a significant development in ophthalmology during the 1980s and early 1990s.
Reasons for Its Reduced Use
Despite its initial promise, Radial Keratotomy is rarely performed today due to several long-term limitations and the emergence of more advanced procedures. A notable issue was the unpredictability of outcomes, with patients often experiencing overcorrection, undercorrection, or the development of irregular astigmatism. This variability made consistent visual correction challenging.
Many individuals who underwent RK also experienced diurnal fluctuation in their vision. This occurred because the cornea’s structural integrity was altered, making it less rigid and more susceptible to subtle changes in shape with daily activities. Additionally, patients frequently reported visual disturbances such as glare, halos, and starburst patterns, especially at night or in low light.
A significant long-term complication was the progressive hyperopic shift, where the cornea continued to flatten over time, leading to farsightedness years after the initial surgery. Furthermore, the corneal incisions often did not heal completely, leaving the cornea permanently weakened and susceptible to ectasia, infection, and rupture from even minor trauma. The advent of more precise laser-based procedures, such as LASIK and PRK, offering greater safety, faster recovery times, and more stable results, led to RK’s decline.