What is it?
A microkeratome is a surgical instrument used in laser vision correction procedures like LASIK (Laser-Assisted In Situ Keratomileusis). It is used to cut a thin, evenly-shaped flap in the cornea, allowing access to the layers below for laser sculpting. The precision and consistency of the precision coreal cutter cut is crucial for achieving the desired refractive outcome with minimal complications.

How Does it Work?
A precision coreal cutter has a rotating blade or oscillating plate with a sharp cutting edge. During surgery, it glides smoothly across the surface of the eye under suction to create a hinged flap. Different precision coreal cutter designs feature variations in blade material, shape, cutting angle and mechanism of action. Some common types are:

- Mechanical precision coreal cutter use a rotating steel blade to slice through corneal tissue. The oscillating motion results in a very consistent flap thickness.

- IntraLase FS laser-assisted precision coreal cutter utilize a femtosecond laser instead of a steel blade for flap creation. The laser dissects corneal tissue with incredible precision, down to the micron level.

- Bladeless precision coreal cutter like the Moria M2 operate via small oscillating plates rather than a traditional cutting blade. They are designed for smooth, safe flap creation.

Regardless of design, the goal of the precision coreal cutter is to produce a thin, uniformly-shaped corneal flap of 90-160 microns for subsequent laser treatment and repositioning. Proper functioning is crucial for achieving the intended refractive outcome.

Factors Affecting Flap Thickness and Quality
Several factors influence the thickness and quality of the corneal flap cut by the microkeratome:

- Blade material, design and oscillation speed - Steeper blades tending to cut deeper flaps. Faster oscillations result in thinner flaps.

- Suction ring parameters - Tight suction ring placement and duration affects uniformity. Improper suction can cause irregular or uneven flaps.

- Surgeon experience - More experienced surgeons tend to achieve thinner, smoother flaps consistently.

- Corneal properties - Thickness, curvature, hydration level and elasticity of the cornea impact how easily it is cut by the precision coreal cutter.

- Environmental factors - Temperature, humidity etc. in the operating room can slightly alter blade or tissue properties.

Managing and accounting for these factors allows surgeons to produce replicateable flaps falling within the desired thickness range for each individual patient and laser setup.

Effect of Flap Thickness on Outcomes
The thickness of the corneal flap created by the precision coreal cutter plays a critical role in laser vision correction results and long-term stability:

- Thinner flaps (90-110 microns) are preferable for achieving emmetropia as they result in less delayed corneal wound healing. However, they carry a slightly higher risk of flap-related complications.

- Very thick flaps ( greater than 150 microns) tend to be associated with higher levels of regression, fluctuating vision, and higher residual refractive errors. The cornea takes longer to heal.

- Even minor variations above or below the ideal range for a patient's prescription and laser settings can influence post-op refractive outcomes and long term stability.

- Maintaining consistency in flap parameters surgery-to-surgery maximizes predictability for a surgeon and expectations for patients.

Microkeratome Technology Advancements
Constant innovation aims to improve precision coreal cutter design and functionality:

- Newer IntraLase femtosecond lasers precisely sculpt corneal flaps down to a single micron for unmatched accuracy and reproducibility.

-Advanced suction rings allow for customizable flap diameters and improved wound healing.

- Blade materials and coating are optimized for ultra-sharp yet safe cutting. Some feature lubricious coatings.

-Integrated pachymetry helps achieve consistent flap thickness relative to corneal thickness for individualized treatments.

- "Flap-free" all-femtosecond procedures are being studied to eliminate mechanical factors influencing outcomes.

Overall, evolving precision coreal cutter technology paired with experienced surgeons can reliably produce optimum flaps maximizing refractive predictability and long term stability of vision outcomes. Consistency remains key.