Microkeratomes have become an indispensable tool for refractive eye surgeons performing laser vision correction procedures such as LASIK. This precision surgical instrument is used to create a thin flap in the cornea, allowing for minimal corneal tissue removal during surgery.
Workings
A instrument consists of an oscillating blade attached to a handheld device. During surgery, the blade is passed over the center of the cornea in a controlled, gliding motion. This action microscopically slices off the outer corneal layer, known as the epithelium, leaving behind a very thin hinged flap. The flap is then gently folded back to expose the underlying stromal tissue for laser ablation by an excimer laser. After reshaping the cornea, the flap is smoothly returned to its original position, where it naturally re-adheres without sutures.
Advantages of Microkeratome Over Laser Ablation Alone
While laser ablation alone can correct refractive errors, using a instrument first offers several key advantages:
Precise Flap Creation
Microkeratome are specifically designed to produce corneal flaps of consistent thickness - usually between 100-110 microns. This level of precision is critical for achieving the best postoperative vision results and minimizing complications. Reproducible flaps also allow surgeons to perform enhancements or “touch-ups” with laser years after the initial procedure.
Minimal Tissue Removal
By lifting the corneal flap, only 5-10 microns of stromal tissue needs to be removed by the excimer laser for refractive correction, compared to 100 microns or more with laser alone. This results in much less induced corneal haze and faster visual recovery times. It also means less risk of ectasia, a potentially dangerous thinning of the cornea, which has been seen in some laser ablation-only patients.
Reduced Discomfort
The flap acts as a protective barrier between the neural structures in the cornea and the excimer laser. This significantly lessens any pain or sensitivity that may occur during or after surgery compared to cutting directly into the stroma with laser. Patients generally experience rapid relief from glare, halos and less drooping of upper eyelids afterwards.
Types of Microkeratomes
Mechanical Instruments
Initially all instruments were of the “mechanical” variety, utilizing an oscillating steel blade driven by a handheld pneumatic device. Though precise, the blade can occasionally cause irregular flap margins. Advancements allowed controlling the blade oscillation movements and angle.
Automated Mechanical Instruments
Computer-controlled mechanisms were later introduced to precisely guide the mechanical blades, improving consistency. Symmetry and thickness of the flap can be more reliably achieved through automation.
Femtosecond Lasers
The latest innovation is femtosecond lasers which use ultrafast infrared pulses to cut the corneal flap. Flaps can be of complex geometries with sharper margins than blades. However, lasers are more expensive and longer procedures. Studies comparing outcomes have found little significant difference between knives and lasers clinically.
Factors Affecting Flap Quality
Regardless of the type used, several factors influence how well a instrument performs:
Corneal Properties
Thinner, softer corneas are more difficult for the instrument to pass through smoothly and may result in an uneven or incomplete flap.
Surgical Technique
Proper suction ring placement and blade settings matched to the eye are crucial. Surgeons must also move the blade swiftly at a steady rate and avoid multiple passes.
Microkeratome Maintenance
Regularly replacing blades that become dull is necessary. Well-lubricated parts also promote smooth blade oscillations or laser scanning. Minor debris can potentially mar the flap.
Through precisely lifting a hinged corneal flap, instruments enabled revolutionary laser vision correction techniques. Consistently reproducible flaps are key to good LASIK outcomes and ensuring satisfactory uncorrected vision long-term. Ongoing developments aim to make the flap creation process even safer and more comfortable for patients. instruments set the foundation for laser eye surgeons to achieve lifetime vision freedom for millions worldwide.
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Ravina Pandya, Content Writer, has a strong foothold in the market research industry. She specializes in writing well-researched articles from different industries, including food and beverages, information and technology, healthcare, chemical and materials, etc. (https://www.linkedin.com/in/ravina-pandya-1a3984191)