Everything there is to know about femto laser
Femto Laser system uses short-duration pulses lying in the infrared range (10−15 s) with a wavelength of 1053 nm to produce tissue photodisruption. Its use is in ophthalmology for corneal surgeries, including the laser-assisted in-situ keratomileuses (LASIK). The introduction of the Femto Laser in LASIK has revolutionized this procedure. In 2009, over 55% of the performed LASIK procedures were with Femto lasers, with their use now prioritized over the traditional microkeratomes. This high energy technology permits the highly precise bladeless incision of tissues, with those incisions made with numerous patterns and depths. Their use in cataract surgery has also increased immensely. Many of the Femto Laser properties match with the neodymium-doped yttrium aluminum garnet laser (Nd: YAG). Just like neodymium-doped yttrium aluminum garnet laser (Nd: YAG), Femto Lasers utilize the photodisruption or photoionization principle to form an aggregated cloud of free electrons and ionized molecules. This leads to the production of high energy shock waves that can destroy the tissues. The chief benefit of Femto laser, which makes it superior to Nd: YAG, is that it only destroys the target tissues and causes minimum harm to the surrounding tissues. The collateral damage caused by it is 106 times lesser than Nd: YAG. Other advantages of using it are as follows:
- It can focus on the anterior surface, within or behind the surface of the cornea.
- It has minimal chances of depletion of wavelength energy, and it can be useful in cases where the structures of the eye become foggy (e.g., edematous cornea).
- It diminishes the frequency of complications that can occur during cutting. Such as uneven cuts or buttonholes.
- Surgeons prefer its use over other methods because it provides better control over diameter, thickness, angles, and lengths during cutting.
- No risk of moving parts.
- It promises very firm flap attachment, decreased epithelial growth frequency, minimal increase in intraocular pressure, reduced eye dryness, and hemorrhages.
- Better refractive and visual outcomes compared to other methods.
With the improvements in its design, various models with a firing frequency of 150 kHz (compared to the firing frequency of 10 kHz in the older models) are available in the market. The fifth-generation 150-kHz IntraLase system offers flexibility in making cuts with different geometries, depths, diameters, sizes, and separation distances. It works with maximum precision, decreases the time for flap cutting, and minimizes energy requirement.
The earliest models were not as efficient and took a long time to perform the procedure. However, the Femto Lasers prepared today (IntraLase systems) can achieve the same work in just 10 seconds. Although optimum temperature and humidity range is a requirement for its excellent working, modern designs with advanced technology decrease its environmental sensitivity.
The history of the development of laser technology is very ancient. However, the use of Femto laser technology is not too old. In the 1990s, at the University of Michigan, Dr. Juhsaz and Dr. Kurtz made the first-ever Femtosecond laser system, which became readily adopted for use in ophthalmology. The approval for its use in ophthalmology was by the Food and Drug Administration (FDA) in 1999 for refractive errors and various corneal problems. In 2001, the first generation of Intralase femtosecond lasers was introduced, and the FDA approved the first Intralase Pulsion for use in LASIK. Continuous innovations were made in the models. Pulse frequency increased (presently up to 150 kHz), and energy consumption during the procedure was reduced. In 2003 there was the introduction of the second generation with 15 kHz. The third generation's introduction with a 30 kHz frequency was in 2005, and the fifth-generation with 105 kHz frequency was in 2008. Now, many brands with a wide range of specifications manufacture the Femto laser systems.
Indications to use
Here are the applications of the Femto Laser:
- LASIK surgery: During LASIK surgery, the correction of refractive errors is possible, which involves the forming of the anterior lamella and photoablation. The minimal degree of deviation in achieving the required thickness makes the Femto Laser ideal for use. In patients having thin cornea or severe ametropia, it is the ideal system for the surgical procedure as it reduces the chances of tissue damage and ectasia.
- Intrastromal corneal ring segment implantation: this is a surgical procedure proposed for keratoconus. Manual corneal tunneling is also an alternative, but it may pose serious complications such as epithelial damage, extrusion, or perforations. This can be preventable by using Femto laser.
- Presbyopia: the insertion of corneal implants or corneal inlays as a presbyopia treatment is by using these lasers.
- Astigmatism: Femto laser is also useful in creating incisions to improve astigmatism. Astigmatism can occur primarily or due to trauma, cataract surgery, and it reduces the cylinder in the postoperative period compared to the perioperative period.
- Keratoplasty: the level of precision achieved during incision and minimal risk of collateral damage and perforations makes it ideal for procedures like lamellar keratoplasty. With the Femto Laser, angular cuts are precise, leading to earlier recovery after the surgery.
- Small incision lenticule extraction: it is also useful in the small incision lenticule extraction (SMILE) method, a requirement for the intrastromal lenticule cutting and its extraction. The less deep and wide cut leads to minimum stromal tissue utilization, minimal nerve damage, and dry eyes.
- Cataract surgery: nowadays, the shift is towards Femto laser-assisted cataract surgery (FLACS) as it produces a minimum of endothelium cell damage. This method produces more precise incision with reproducible anterior capsulotomy, uniformly shaped, improved focus, and intraocular lens overlap.
- Glaucoma: glaucoma is also treatable with this laser technology as its use is in the performance of sclerotomy to improve the condition.
Complications of using a Femto laser
Although Femto lasers provide an extensive set of advantages, some complications may arise using it.
- Gas bubbles. The formation of gas bubbles at the flap interface is common. Sometimes, these gas bubbles may penetrate the stromal layer, which inhibits the ability of eye tracker to track and register. If a bigger vertical gas bubble passes into the cornea's subepithelial area, it can cause a buttonhole. Sometimes, gas bubbles move towards the anterior part, passing through the trabecular meshwork. But these incidences can be reduced by proper centripetal spiral patterns.
- Increased sensitivity to light. Patients who have LASIK procedure might complain of sensitivity to light after days or weeks. The reason might be an increased inflammatory reaction or biochemical response of keratocytes. The condition resolves with aggressive steroid therapy.
- Rainbow glare. If small irregularities form on the flap's posterior surface, the patient may complain of a complete rainbow pattern emitting from white light. It is called rainbow glare.
- Lamellar keratitis. Tissue damage during the procedure can cause lamellar keratitis, which can progress towards necrosis. However, most of the time, lamellar keratitis resolves without any serious complications.
Other disadvantages include high cost, proper training to master its use, and difficulty picking up the flap if retreatment is indicated.
How does it work?
Here, there is an explanation of the general procedure to be carried out while performing the surgery. However, the skills and techniques specific to each surgical procedure are beyond the scope of this article.
The laser tip is placed and stabilized over the eye, which is possible employing a Patient Interface (PI) and a specially made contact lens. Live optical coherence tomography (OCT) snapshots are shown on the computer screen continuously. The procedure to be performed, such as the key incision, capsular opening, and side port incisions, skillfully line the computer screen. By pressing the function button, the system completes the steps automatically in about 45 seconds. After completing the procedure, the laser gets displaced, and entry into the incisions is possible through the spatula. The aspiration of any fragmented parts and the insertion of the intraocular lens then follows. It does not require suturing because it is self-healing.
There are several designs on the market, with different specifications; however, we will cite the general specifications:
- Sterile Patient Interface technology
- Computer run suction
- Automatic turn off safety feature
- User friendly
- High precision cuts
- Pressure sensors
- Uninterruptible power supply
- Integrated high-quality microscope
- Width: 850 mm
- Length-: 1270 mm
- Height: 1 300 mm
- Wavelength 1,040 nm
- Spot size range (approx. 1µm or >1µm)
- Excellent surface quality
- Operation speed range (8 sec -60 sec)
- 220-230 V power supply
- 18-24 °C room temperature
- 30-50 % humidity level
- Pulse Duration 500 - 800 femtoseconds
There are many brands available in the market that provide very promising and efficient Femto laser systems. Here is a list of the leading brands:
- Abbott Medical Optics Inc
- Perfect Vision AG
- Ziemer Ophthalmic Systems AG
- Carl Zeiss Meditec AG
- Alcon Laboratories, Inc.
- Bausch & Lomb Incorporated
The models currently in greater demand are:
- Femto LDV
Femto laser technology has revolutionized the traditional practice in the field of ophthalmology. The approval of using this technology for correcting refractive errors and other eye pathologies has dramatically increased the efficiency and success rate of the procedures. It has also played a vital role in decreasing postoperative complications. The fifth generation of Femto laser is in wide use by the ophthalmologist. Still, it is in the process of continuous development. LASIK, SMILE, and many other surgical eye procedures are done through Femto Lasers. Some limitations exist, but their advantages outweigh their disadvantages.