Better Health 2015 > Eye Health > Femtosecond laser

An Innovative Technique in Treating Refractive Errors and Cataracts

Technologies to correct refractive errors have developed continuously, leading to more efficacious and efficient treatments; one of them is femtosecond laser, which replaces traditional incision-based surgical techniques, including incision-based LASIK vision correction and incision-based cataract surgery.

What is femtosecond laser? What are its unique advantages? Will patients and doctors consider its therapeutic effects successful? Find the answers to these questions in this edition of Better Health. 

Getting to know femtosecond laser 

For the treatment of eye diseases, femtosecond laser emits laser energy at high speed, measured in units of one femtosecond (one quadrillionth of a second). Requiring just one femtosecond, this treatment replaces the scalpel blade in fragmenting corneal layers or in making a corneal incision. The precisely controlled laser beam chooses the target, size, and pattern, as well as disintegrating tissue or other substances at the molecular level – without damaging peripheral healthy tissue or emitting heat.

Two applications of femtosecond laser in eye surgery are femtosecond LASIK, for the treatment of refractive errors from traditional LASIK and femtosecond laser-assisted cataract surgery, for removing cataracts.



Femtosecond LASIK is bladeless LASIK

LASIK corrects innate refractive errors such as nearsightedness, farsightedness, and astigmatism.

LASIK surgery has two steps:

The first step requires the surgeon to create a corneal lamellar flap in the cornea.

The second step has the ophthalmologist fold back the corneal flap to expose the underlying corneal stroma. The doctor then administers an excimer laser beam to the stroma, to adjust the corneal curvature in correcting refractive errors. After that, the flap is repositioned without suture.

Formerly, the ophthalmologist used a blade (or microkeratome) to fragment the corneal layers. In the past several years, however, femtosecond laser technology (also called femtosecond LASIK), fragments the cornea with greater precision, and is less invasive. The process of using an excimer laser to remodel the corneal curvature remains unchanged. 

Minimize complications from flap creation

Dr. Tharinee Kulkamthorn, an ophthalmologist who specializes in refractive surgery, explains the attributes of femtosecond laser, compared to the traditional method to create the corneal flap. She points out that femtosecond laser beams create a thinner corneal flap with uniform corneal thickness, unlike keratome blade-created flaps that are thin in the middle and thick on the edges.

Femtosecond laser reduces the risk of creating an irregular surface on the flap, such as uneven ablation depth or a hole in the middle of the surface. The laser-created flap also provides defined edges, accurately angled to the lower cornea, so that the corneal flap fits back in place precisely – which reduces the chance of its dislocation.

“Fragmenting corneal layers to acquire a perfect flap is the key to successful LASIK surgery,” says Dr. Tharinee. “The doctor must be sure that the corneal flap can be opened and folded back to its closed position, and that it is not too thin, too small, or torn. The doctor will not open a corneal lamellar flap that is not perfect because if it cannot be completely closed, the patient will see light scatter at night.”

Femtosecond laser also helps boost the success rate of LASIK treatment because a perfect corneal flap enables the surgery to proceed. If the flap is torn, pierced, or incomplete, the doctor must stop surgery immediately. Such problems in blade surgery may scar the cornea, which takes approximately three months to heal. After that, the surgeon must try again – this time at a lower depth.

“Femtosecond laser flap creation increases the safety and perfection of the corneal flap, when compared to blade-assisted flap creation. It also increases the chance for patients with thin corneas, to have LASIK refractive surgery,” says Dr. Tharinee. “The laser cut delivers a flap depth of 100 to 110 microns thick, whereas a blade-created flap is 30 microns deeper. In some patients, a microkeratome blade procedure is not possible because there is not enough corneal material to give structural support after the surgery. But femtosecond laser’s thinner flap leaves more tissue under the flap for support.” LASIK surgery is possible in these cases.

Also, doctors observe that corneas treated with femtosecond laser heal faster than traditional methods, reducing post-surgery dry eye symptoms. 

Femtosecond laser-assisted cataract surgery 

Cataract surgery is the most commonly performed surgical procedure in the world. The World Health Organization estimates that each year, there are 19 million operations worldwide, and this number will increase to 32 million in the next five years due to the aging population. 


step of lasik treatment bumrungrad hospital bangkok thailand

  1. Anesthetic drops are applied.
  2. The corneal flap is created and folded aside.
  3. The excimer laser beam reshapes the cornea.
  4. The flap is folded back into place.

When to have cataract surgery?

“Human eyes are like a camera with an internal lens, which after many years of use, can become opaque,” explains Dr. Ekachai Bharksuwana, an ophthalmologist specializing in cataract treatment. “When the opacity is so great that no light can reach the retina, visual acuity worsens. With age, degeneration of the eye is inevitable.”  
A possible cause of cataracts is a concussion or trauma to the eye. Others include genetic disorders. 
Regardless of the cause, the average age of people who undergo cataract extraction is 70 years old.
“When symptoms such as blurred vision, double vision, sensitivity to light, chromatic aberrations, or frequent changes in eyesight (although corrected with glasses or contact lenses), do not improve by themselves, I recommend patients get an eye examination,” says Dr. Ekachai. “Cataracts, left untreated, will result in blindness or acute glaucoma causing pain and vision loss.”


Laser-assisted cataract surgery 

“Traditionally, due to technological limitations, cataract surgery was performed after the lens had become opaque,” says Dr. Ekachai. “Today, we can perform cataract removal surgery at all stages, whether full blown or less developed. When, is wholly dependent on the stage of the individual patient’s condition. Some patients come in for surgery as soon as they can no longer read messages on their mobile phones.”
The traditional method of removing a cataract entails the doctor using a blade to make an incision on the patient’s limbus zone, breaking up the hard cataract material using ultrasonic waves, removing it, and implanting an intraocular lens.
Recently though, femtosecond laser-assisted cataract surgery has replaced the scalpel. It reduces the ultrasound energy required for cataract fragmentation and centration of the intraocular lens during implantation. 

More precise with less trauma

Dr. Ekachai says that using femtosecond laser to makean incision on the cornea and to open the lens capsule offers greater precision. It also ensures that the surgeon inserts the intraocular lens at the right position. Femtosecond laser also reduces the possibility of astigmatism because there is less trauma to the eye, and the patient recovers faster. Moreover, femtosecond laser decreases the risk of infections after surgery, and the increased precision standardizes treatment results.
“The day after surgery, the patient has from 60 to 70 percent clearer vision, and this gradually improves. 
The patient will start seeing clearly within the next three months, and with no chance of recurrent cataract,” says Dr. Ekachai.
Correction of refractive errors using femtosecond laser LASIK and femtosecond laser-assisted cataract surgery provides satisfactory results in most patients. Consult an ophthalmologist to see if this technology is right for you.


Femtosecond LASIK is suitable for patients:

  • With innate nearsightedness, astigmatism, or farsightedness;
  • 20 years of age and older, with static eyesight for at least one year (eyesight change not exceeding 0.5 diopters in one year);
  • at risk of the blade method fragmenting corneal layers, for instance, those having small eyeballs (because femtosecond laser was designed to require less eye area than that of blades), or corneas that are too steep or too flat (because successful femtosecond laser treatment is not contingent on corneal curvature);
  • with no severe corneal diseases or severe eye diseases such as macular degeneration, severe ocular dryness, or systemic diseases that delay healing (e.g. uncontrolled diabetes mellitus, SLE disease, etc.); 
  • who are afraid of traditional surgery, which entails equipment motor noise while creating the corneal flap, and a momentary visual blackout; femtosecond laser is silent, gentler, and requires less compression, making the patient feel more at ease.

Which lens option is right for you? 

Cataract surgery corrects refractive errors with implantation of prescription intraocular lenses to replace the diseased cataract lenses.
At present there are four types of intraocular lens implants available:
  • Monovision Lens, a normal lens suitable for those with nearsightedness or farsightedness (before cataract surgery). This lens enables normal long-distance vision, but reading still requires eyeglasses;  
  • Toric Lens, suitable for pre-cataract surgery patients that have nearsightedness or farsightedness with astigmatism. This lens enables normal long-distance vision, but reading still requires eyeglasses. The price of this lens is slightly higher than that of monovision lenses;
  • Multifocal Lens, a type of lens to correct refractive errors that include nearsightedness, farsightedness, and presbyopia;
  • Multifocal Toric Lens, a type of lens to correct refractive errors, that include nearsightedness, farsightedness, and presbyopia – as well as to correct hypermetropic astigmatism.
Intraocular lens implantation types


What to expect from cataract surgery… it’s not as worrisome as you may think.

  • To avoid pain and anxiety, the patient can choose general anesthesia or ophthetic drops, and remain conscious during the procedure;
  • The surgery only takes about 10 to 15 minutes;
  • The patient can rest after surgery and then leave the hospital on the same day;
  • The patient must wear an eye shield, and visit the doctor for removal of the eye shield the following day;
  • The surgery can be performed on both eyes at the same time depending on the patient’s requirements, but the doctor will recommend operating on one side at a time to reduce the risk of infections; if both eyes are done, the doctor recommends splitting the procedure into two parts with a night in the hospital between them;
  • At the doctor's discretion, golf-playing patients can be back on the course, three days after surgery.

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