Microkeratome

Key takeaways

Microkeratome belongs to science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Microkeratome to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Microkeratome from memory before moving on to harder problems.

Reference excerpt

A microkeratome is a precision surgical instrument with an oscillating blade designed for creating the corneal flap in LASIK or ALK surgery. The normal human cornea varies from around 500 to 600 μm in thickness; and in the LASIK procedure, the microkeratome creates an 83 to 200 μm thick flap. The microkeratome uses an oscillating blade system, which has a blade that oscillates horizontally as the blade travels vertically for a precise cut. This piece of equipment is used all around the world to cut the cornea flap. The microkeratome is also used in Descemet's stripping automated endothelial keratoplasty (DSAEK), where it is used to slice a thin layer from the back of the donor cornea, which is then transplanted into the posterior cornea of the recipient. It was invented by Jose Barraquer and Cesar Carlos Carriazo in the 1950s in Colombia. As of 2023, there are two options for cutting into the cornea, the microkeratome and the femtosecond laser. The femtosecond laser emits ultrashort pulses that act as a blade to cut through the eye with precision and accuracy. Many surgeons differ in using a femtosecond laser or a microkeratome for their operations. Most surgeons and patients prefer the bladeless femtosecond laser.

History The microkeratome was created in 1948 by Jose Ignacio Barraquer Moner in Bogota, Colombia. Barraquer was known as the father of refractive surgery due to his lifetime involvement and findings in the field. He developed the microkeratome for his keratomileusis (surgical reshaping of the cornea) procedure to correct the refractive error in the eye, which has evolved into the LASIK surgery of the 21st century. Refractive error is caused by an imperfect cornea that disallows light from correctly refracting and focusing on the retina, which results in blurry images. Correcting refractive error was Barraquer's expertise and as time went on he continued to alter his method to correct refractive error. In 1958, Barraquer performed a lamellar resection in situ(corneal tissue replacement), where he used a prototype microkeratome that moved along a ring without a guide. By 1962, Barraquer created a more accurate microkeratome with a suction ring that would act as a guide. The suction ring suctioned the eye in place to create pressure for a precise cut. Barraquer's surgery required the creation of a free flap, which meant the cornea was completely cut through. In 1991, Ioannis Pallikaris introduced the concept of a corneal hinge, which kept the cornea flap attached and helped with the healing process. During the same year, the motorized microkeratome was released. The motorized microkeratome contained a system of gears that ensured a constant blade velocity for a consistent flap thickness. As the microkeratome gained exposure, surgical instrument corporations such as Moria Surgical, Chiron(bought by Bausch and Lomb Surgical), and Advanced Medical Optics began to create their microkeratomes. Moria Surgical still produces microkeratomes, but Chiron and Advanced Medical Optics have discontinued microkeratomes due to the femtosecond laser's popularity. The Moria Surgical microkeratome was special because they created the first single-use microkeratome in 1999, which led to fewer complications regarding the blade. Chiron created the hansatome microkeratome, which became known as the industry standard for its safety and consistency. The hansatome also created an upper hinge, which lowered the risk of flap displacement from blinking. Advanced Medical Optics created the amadeus microkeratome, which used a single-hand design that lowered the learning curve for new surgeons. As of 2023, the microkeratome is barely being used due to the increased use of the femtosecond laser. A few surgeons use the microkeratome due to lower cost and comfort with a microkeratome[8]. However, most surgeons and patients tend to prefer the bladeless femtosecond laser, due to its precision and safety.

Components

Suction ring During the keratectomy(surgical removal of a layer of the cornea) the suction ring fixates and stiffens the eye. Depending on the required flap diameter and the form of the cornea, different suction rings are employed. The upper part of the suction ring(plate) allocates the cornea with variable diameters. A flexible silicone tubing connects the central section to the ring's suction chamber. On the vertical outer part of the suction ring, there is a skirt that allows hermetic sealing for proper suction. All these parts are used together to create the suction ring. Using the correct suction ring minimizes the risk of complications.

Microkeratome cutting head The microkeratome cutting head consists of a non-vibrating block and an oscillating blade unit. The non-vibrating block is composed of a tracking system, applanation plate, and cavities. The tracking system matches to the suction ring to connect the head to the ring using corresponding grooves. The applanation plate is the part of the block that precedes the oscillating blade and flattens the cornea, to create a constant angle for the blade for a constant flap thickness. The cavities of the block are used to hold the oscillating blade unit in place. The oscillating blade unit has a blade made of stainless steel or chrome-platinum. The standard oscillation speed of the blade is 15,000 rpm with an engagement angle between 24° and 30° depending on the required flap thickness. The direction of the cut determines the type of corneal flaps created on the cornea.

Drive unit The drive unit is attached to the microkeratome head to ensure that the drive axis fits the blade and oscillates correctly. The drive unit uses either a single or dual electric motor for automated translation. For manual head translation, a gas turbine is used for blade oscillation.

Central unit The central unit delivers the energy needed to power the drive unit and creates pressure between the eyeball and the suction ring. One pedal is used to start and stop the pressure for the suction ring. The second pedal controls the blade oscillation of the microkeratome.

… excerpt ends here. Continue reading the full article.

Worked examples

Example 1 — a first encounter with Microkeratome

Start with the simplest possible case. Write down what Microkeratome claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Microkeratome before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Microkeratome ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Microkeratome

In research: Microkeratome appears in science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Microkeratome in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Microkeratome is common in secondary-school and first-year university syllabi. It links to neighbouring topics Ophthalmology, Surgical instruments, so understanding it makes those chapters shorter.
In everyday life: Look for Microkeratome outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

How to study Microkeratome in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Microkeratome means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Microkeratome out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Microkeratome in simple terms?

A microkeratome is a precision surgical instrument with an oscillating blade designed for creating the corneal flap in LASIK or ALK surgery. The normal human cornea varies from around 500 to 600 μm in thickness; and in the LASIK procedure, the microkeratome creates an 83 to 200 μm thick flap.

Why does Microkeratome matter?

Because it connects several science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Microkeratome?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Microkeratome.