Keratotomy refers to eye surgeries that involve making incisions into the cornea, the clear front surface of the eye. This procedure aims to alter the cornea’s shape to correct refractive errors, such as nearsightedness or farsightedness. Historically, keratotomy represented a significant advancement in surgical approaches to vision correction.
Understanding Keratotomy
The term “keratotomy” most commonly refers to Radial Keratotomy (RK), a surgical procedure developed in 1974 by Russian ophthalmologist Svyatoslav Fyodorov. RK was designed to correct nearsightedness, where distant objects appear blurry because light focuses in front of the retina. The procedure reshapes the cornea by creating precise incisions to flatten its curvature, allowing light to focus more directly on the retina and improving vision.
Nearsightedness occurs when the eye is too long or the cornea’s focusing power is too strong, causing light to focus before reaching the retina. RK aimed to reduce this focusing power by altering the cornea’s shape. It was effective for lower levels of myopia, often up to -4.00 diopters.
The Keratotomy Procedure
Radial Keratotomy (RK) was typically performed as an outpatient procedure, often under local anesthesia. Before the surgery, precise measurements of corneal thickness were taken to determine the appropriate depth for the incisions.
A specialized diamond knife was used to create radial incisions on the outer part of the cornea. These incisions extended from the periphery towards the center but did not reach the central optical zone, the area directly in front of the pupil. The number, depth, and length of these incisions were carefully determined based on the patient’s degree of myopia and desired correction. Incisions were made deep, often reaching about 80% to 90% of the corneal depth.
Results and Considerations
Patients who underwent Radial Keratotomy (RK) often experienced improved distance vision. However, the procedure was associated with various side effects and potential complications. Common visual disturbances included glare and starbursts, particularly noticeable in low-light conditions or at night, due to the incisions interfering with light entering the eye.
A significant concern was fluctuating vision, also known as diurnal variation, where vision could change throughout the day, often being more farsighted in the morning and more nearsighted by evening. This fluctuation was attributed to changes in corneal hydration and thickness affecting light refraction. Long-term stability issues also emerged, with many patients experiencing a progressive hyperopic shift, meaning their vision gradually shifted towards farsightedness as the cornea continued to flatten years after the surgery. Other potential complications included the return of nearsightedness (regression), overcorrection leading to farsightedness, and induced astigmatism. The incisions, which often did not fully heal, also presented a lifelong increased risk for corneal infection, inflammation, and traumatic rupture from direct injury.
Evolution of Vision Correction
Radial Keratotomy (RK) largely fell out of favor as a primary vision correction surgery due to the emergence of newer, more advanced techniques. The procedure, while pioneering, was less predictable and carried a higher risk of complications compared to subsequent advancements. The incisions made during RK could also leave permanent scars and weaken the cornea, making future eye surgeries more complex.
Laser-based refractive surgeries, such as Photorefractive Keratectomy (PRK) and Laser-Assisted In Situ Keratomileusis (LASIK), played a significant role in RK’s decline. These laser procedures offered greater precision in reshaping the cornea and generally resulted in more predictable outcomes with fewer complications. While RK was a groundbreaking step in the history of refractive surgery, its limitations led to its supersession by modern laser techniques that offer enhanced safety and efficacy for vision correction.