Advanced Surface Ablation is one kind of photorefractive keraectomy or PRK procedures. PRK is an older procedure than LASIK procedure, almost with the same outcomes and long term visual results, with only drawback of slower recovery of vision and comparatively more discomfort. ASA possesses all the benefits of the PRK with added benefit of faster timeframe of visual recovery, compared to the basic PRK procedure.
The surface treatments performed for PRK and its variants, such as Epi-LASEK, Epi-LASIK and LASEK, are collectively called as Advanced Surface Ablation. So, ASA is also identified as other laser vision correction procedures, like alcohol-assisted PRK, LASEK or epi-LASEK.
Advanced Surface Ablation technology is next generation PRK or PhotoRefractive Keraectomy procedure. PRK has bee-n developed before 30 years, much earlier than LASIK procedure. Though both of them yield same outcomes and benefits, the only drawback with PRK is that the recovery of vision is a bit slower than the other. ASA, being advanced generation of PRK, it possesses all the advantages of PRK with added advantage of faster recovery of vision compared to the basic PRK procedure. ASA today is very advanced with advanced procedural technologies and wavefront-optimized ASA provides most optimistic results compared to standard LASIK procedures.
How Is It Better?
ASA is one kind of PRK procedure, but has faster recovery, but how is it achieved? The key difference is the improved surgical method, which is much advanced compared to the method available, when the PRK developed for the first time.
How ASA Works?
The standard ASA procedure involves treatment of the surface of cornea and it does not involve the process of making the flap. Excimer laser is used in this procedure and has the capability of tracking the eye and perform reshaping of the cornea’s front surface, through wavefront customized treatment and it plays vital role in this procedure. After the surgery, a soft contact lens is placed over the eye, temporarily to support the process of healing, for a few days.
The procedure is simple, as very advanced technology is used and it lasts in just a few minutes. The procedure involves the following steps.
- Initially, the surgeon starts the procedure with the anaesthetic drops and is applied to the eye to provide enough comfort during the surgery.
- Then the cornea surface or epithelium is removed gently, with the help of automated and soft brush.
- Then reshape of the eye is attempted in the treatment through laser, according to the prescription of the patient.
- After reshaping, rinsing of cornea is performed using a physiologically balanced and chilled solution, immediately.
- At the end of the procedure, a contact lens would be placed with a clear bandage over the eye. This bandage has to be retained until regeneration of the epithelium and it takes a several days.
After the Procedure
Right after the procedure, shielding is placed over the eyes as the vision becomes blurry immediately after the procedure, you need someone to come along with you to drive you back home, from the medical centre and the rest of the day, you need to relax at home. Discomfort from mild to moderate levels is possible and it may continue for 2 to 3 days. The surgeon provides all the necessary guidelines and instructions to get this discomfort managed after completing, after the surgery.
The most interesting part is that the patient can resume day to day and regular activities, in 2 to 3 days. Medicated drops have to be continued for several weeks, post the surgery. For first few months after the surgery fluctuations of vision are possible. The complete vision takes a few months after the treatment of ASA.
Eligibility for ASA
- The candidate must be more than 18 years of age.
- The patient should attain prescription of stable eye for at least last one year.
- Wide pupils are needed.
- One should not have any issues related to health, as they may affect the eyes.
- The patient cannot undergo LASIK technically, because of corneal dystrophy or glaucoma or problems of eye pressure.
- The corneas are too thin to undergo LASIK surgery.
So far ASA has already enhanced numerous lives of people. And still, it is important to understand the expectations in realistic scenario and the decision must be based on them. The first point is the eligibility and it is determined by your doctor, who decides whether you are a good candidate or not based on the results obtained after special tests, through state-of-the-art technology. After successful surgery, the patient can get back to the normal activities, with no dependence over corrective lenses.
Intense complications are extremely rare after the ASA surgery. It is an effective and permanent procedure, performed safely. However, certain risks and complications are possible, based on various factors. Most of these and in fact all these risks and complications can be reduced through careful determination and selection of the procedure through pre-operative testing, protocols followed during the surgery and enough post surgery care.
ASA as Advanced or TransPRK
The technology keeps advancing in the medical industry, like for any other industry in the world. Advanced surface ablation surgery has improved to the next level and is known as Trans advanced surface laser ablation, which is also technically same as TransPRK surgery procedure.
ASA or TransPRK procedure is an improved version of ASA with the key difference in the way corneal surface or epithelium is removed. In basic PRK procedure, corneal epithelium adhesion gets loosened through pressure applied with a sponge over the central cornea, as alcohol is assisted in this procedure. This procedure involves 20% of ethanol to be applied to the cornea for less than a minute, using a BVA sponge. In TransPRK, the basic technical difference is that the excimer laser performs refractive error correction through no-touch and well-controlled procedure. It removes the corneal epithelium and stroma, both in just one step. Removal of tissue of about 60 micro meters from the periphery and 55 micro meter of epithelial tissue from the central cornea is made very easy and simple, compared to mechanical debridement process, which can be more complication ridden and cumbersome two step procedure.
The difference of technology between ASA and advanced ASA is almost the same in terms of outcome, however, the advantage of this advanced procedure is in the postoperative period. This procedure enables the patient to get back to the regular activities earlier than the basic PRK procedure. The degree of comfort is also the same in both these basic and advanced procedures. Many surgeons prefer the TransPRK procedure, as it is advanced technically and it is more beneficial to the patient, with faster recovery period. According to the experts, TransASA is quicker to perform and has faster recovery time. Since less physical pressure is applied in this procedure, the problem of infectious keratitis is less likely to occur.
Technologies Used In Procedure
The procedure of Advanced Surface Ablation involves cornea surface treatment, however, without the need for flap making process. Surgeons make use of excimer laser in the process and wavefront customized treatment to reshape the front surface of the cornea, by tracking the uneven surface of the eye.
The final stage of the procedure involves placing soft contact lens over the eye to support the healing process. The lens are placed temporarily and continued only for a few days.
ASA as TransPRK
As the ASA procedure has transitioned traditional PRK to a much higher level, it is also referred as TransPRK procedure. ASA is further improved and transitioned PRK to a new level. So, what is the difference between PRK and TransPRK?
The key difference between the two is the removal of epithelium or corneal surface. When the basic PRK procedure is consider, only adhesion of corneal epithelium would be loosened, by applying sufficient pressure using a sponge on the central cornea. The procedure makes use of alcohol. The sponge used here is BVA sponge. The total procedure makes use of 20% of ethanol applied for only a few seconds, lesser than a minute to the cornea with this sponge.
An advanced PRK procedure, ASA or TransPRK (Transepithelial PhotoKeratectomy ) attempts refractive error correction through well-controlled and no-touch procedure, with the help of the excimer laser. Just within one step, both stroma and corneal epithelium are removed. It is different from the mechanical debridement process and removal of 55 micrometer of epithelial tissue from central part of the cornea and removal of 60 micrometers tissue from the periphery, both are done in easy and simple way. Transepithelial PhotoKeratectomy involves removing of using excimer laser. It is performed, while monitoring the blue fluorescence disappearance, in parallel, during ablation. The TransPRK procedure involves lesser physical pressure applied and so issues related to the infectious keratitis would be less likely to occur. It is safer and easier compared to the cumbersome two step mechanical debridement process. And TransASA is not only faster and easier to perform, but also quicker in terms of recovery.
When the outcomes are considered, TransPRK gives superior results to LASEK or LASIK and similar to traditional PRK, when myopia is at moderate levels. When myopia is at higher levels, its visual outcomes are superior to not only LASEK and LASIK, but also traditional PRK.
ASA and Advanced ASA
ASA has been further developed and moved to next level and the new level ASA is termed as Advanced ASA. So, what is the difference for the patient? Both ASA and advanced ASA have similar outcomes. The key difference in two procedures is in the postoperative period. The advanced ASA procedure enables the patient to resume to normal and regular activities faster than the standard PRK procedure. the degree of comfort level is almost the same after these two procedures. However, recovery period after Advanced ASA is much quicker than the basic PRK, according to the experts.
Candidates for ASA
There are certain criteria set and should be satisfied, before a patient becomes an eligible candidate to undergo Advanced Surface Ablation procedure.
- The patient has to be at least 18 years old.
- The general and overall health of the patient should be good enough and there one should not be suffering from the chronicle health diseases.
- The patient has to attain stable prescription, at least before one year, going to the surgery.
- The cornea of the patient has to be very thin.
- The pupils of the eye must be wider enough.
- The patient is not eligible technically for LASIK surgery, because of any of the issues, like glaucoma, corneal dystrophy or eye pressure related issues.
The ASA procedure is performed by adapting advanced technology and so it becomes simple and finished in just a few minutes. The procedure is performed as the following stages.
- The surgery procedure is started with applying anaesthetic drops, so that patient feels enough comfort, during the process.
- The actual process starts with removal of epithelium or cornea surface gently, using a soft and automated brush.
- The cornea is attempted for reshape through laser, as per the prescription of the patient.
- After cornea is reshaped, the process of rinsing the cornea is done immediately, with a chilled and physiologically balanced solution. According to different variants, like Epi-LASIK, LASEK or Epi-LASEK, the epithelial sheet is carefully floated and repositioned back into the position using BSS. Surgeons prefer chilled BSS after the procedure, as cooling can reduce formation of haze and pain. In case the BSCL is intolerant by the patient, a pressure patch may be preferred.
- Finally, non-steroidal anti-inflammatory or NSAID eye drops are placed in the eye and surgeon carefully places contact lens and then covers with a clear bandage on the eye. Then a shielding is placed on the eye.
After the Procedure
Since shield is placed over the eyes at the end of the procedure, vision becomes blurry, right after the surgery. So, the patient needs someone to support to drive the car and take to home from the medical centre. Considerable pain is common immediately after the procedure and so surgeons prefer to relieve it by medication of oral narcotic pain. The postoperative pain can be significantly reduced using topical NSAID drops. However, the same drops may also slow the rate of re-epithelialization process.
Take a long nap after reaching home. During nap, the patient feels mild to moderate level of discomfort. All the necessary instructions and guidelines are given clearly by the surgeon. Post operative pain usually includes photophobia, foreign body sensation, tearing and burning sensation. This post operative pain can be managed with postoperative analgesic protocol.
The specified medication is must to follow until the epithelium gets intact and it takes at least three days. At this point, BSCL, NSAID drops and antibiotic must be dropped, if used in these three days. In case these are used, prolonged use must be prevented by the topical anaesthetic drops have to be confiscated. Some surgeons advocate and recommend to use topical steroids after BSCL removal and usage of long-term topical steroids for the higher levels of myopia, typically more than 4.0D. Eventually steroid drops are recommended to continue for 3 to 4 months and the length of the usage depends on multiple factors, like refractive outcome and corneal haze of the patient. Usually healing activity of keratoyte is 1 to 2 months. Steroid drops abrupt termination may trigger an excess reaction of healing with regression of correction and formation of haze.
Complications and Drawbacks
Since ASA is a reliable and safer refractive error correction laser surgery procedure, intense complications are quite rare. This permanent and effective procedure is performed quite safely. As this is a surgery procedure, certain complications and risks are possible.
The major complications, though are very rare, the patient has to be informed about the technically possible complications as the following.
- Optical Aberrations
Certain optical aberrations, such as ghost images, glare and haloes can occur after PRK. This problem is prominent and possible with smaller ablation zones after correction attempted at higher rates. These aberrations are more during nights and prevalent for myopic young patients having larger diameter of papillary, because of smaller optical zone compared the entrance pupil and dim illumination. Ideally, more uniform, larger and optical zone that is well centered provide better vision quality, especially during nights.
Wavefront-guided customized treatment for cornea have been designed well to reduce increased aberrations and existing aberrations, providing better vision, post laser ablation process.
- Central Islands
Central islands are elevation of central cornea and surrounded by flattening area related to the zone of myopic treatment occurred paracentral region. If it occurs, it can be disclosed by computerized videokeratography. If the elevation occurs at can be from 1D to 1mm. This problem is technically possible, when a wide-beam laser system is used, instead of scanning delivery system. It may result in mild ghosting in vision. Other possible cause can be uneven corneal surface hydration. These islands are usually self-healing and get resolved in 6 to 12 months, otherwise they must be retreated using excimer laser, directly.
- Decentered Ablation
Accurate centration has to be achieved ideally during the procedure of PRK for optimal visual potential. However, centration becomes more quite critical for hyperiopic patients than myopic ones. If the eye begins to drift slowly and loses fixation or when the head is positioned improperly, a decentered stomal ablation is possible to occur. Usually decenrations are occurred from greater correction attempted.
Decentration may leave haloes, glare and decreased acuity of vision. Other symptoms are possible if it exceeds 1mm in terms of severity, however become lesser than 0.5mm. larger pupils tend to experience more symptoms even with smaller decentration, as aberrations induced may get worsen in the periphery.
- Corneal Haze
After many weeks of PRK, subepithelial corneal haze appears usually and its intensity is more in between first and second month after surgery and disappear gradually within 6 to 12 months. Severe haze is possible with myopic correction.
Several measures have been advocated and proposed to control haze, such as a most common one, intra-operative MMC, usage of ultraviolet eyewear protection for one year post treatment. One more way to manage it is to use balanced and chilled salt solution.
The primary drawbacks of the Advanced Surface Ablation are the following.
- The degree of discomfort is a bit more, compared to the other procedures.
- Visual recovery expected is a little longer than the other procedures.
- When the ASA is performed to treat higher refractive errors, corneal haze is increased.
- Management of post operative pain is considerably a significant issue.
Management of postoperative pain can be managed with intrastromal techniques implemented using femtosecond laser and it reduces the issue. Pain relief is managed with many approaches. For instance BCL or Bandage Contact Lens is considered as an effective ways to improve comfort post the surgery, as it can prevent the movement of the lid over the abraded cornea and nerve fibers stimulation is reduced. Basically the nerve fibers are sensitive to the mechanical stimulation and prevention of the mechanical movement can reduce the intensity of the problem to some extent. Another approach is direct cold Balanced Saline Solution (BSS) application, over the cornea. This solution can alleviate the pain resulted from nerve endings exposure.
Another important factor is the discomfort, which is usually combination of foreign body sensation, burning, tearing and photophobia. These are well managed with the medicine for 3 days after the surgery.
As contact lens is placed and covered with a bandage on the eye, the bandage has to be retained for some days. The bandage is removed after waiting sufficient days until the regeneration of epithelium. After removing the bandage in a couple of days, the patient can get back to the regular activities, but slowly, one after the other, according to the intensity of the task.
During the recovery period, the patient needs to continue medication, by applying medicated eye drops and these eye drops must be continued to apply for many weeks. Fluctuations of vision are quite possible to continue for a few weeks. Clear and complete vision takes a couple of months after Advanced Surface Ablation procedure. However, these optimistic results of vision are long lasting.
Variations of ASA
There are many variations developed in the technology of ASA and one of them is, Epi-LASEK. It is quite similar to Epi-LASIK. The only difference is that Epi-LASEK makes use of alcohol with the objective of facilitating epithelial flap creation. When alcohol is added, it allows a better flap and creation of hinge, having no addition of haze of pain.
ASA Versus LASIK
ASA is much safer than LASIK surgery, as most of the complaints technically possible with LASIK are not possible with ASA. A partial list of complications with LASIK that are not at all possible with ASA are, buttonhole flap, incomplete flap, decentered flap, irregular flap, free flap, debris under flap, flap straie, DLK, misaligned flap, flap wrinkles, epithelial ingrowth, traumatic flap dehiscence, flap melt and light sensitivity syndrome, post LASIK. Safety is the most preferable incline to ASA. It is safer because flap is not cut.
Another important aspect to consider is the dry eye condition. It is less prominent after ASA, which is one of the most common conditions after LASIK surgery.
ASA Preferred By Eye Surgeons By Themselves
Most of the eye surgeons prefer to go for Advanced Surface Ablation, rather than LASIK. Though LASIK is recommended to the patients by the same surgeons, they prefer to get ASA done for them. It is because though the vision recovery is a bit longer with the ASA, it is much safer than the other procedures.
ASA Techniques – Comparison
Studies and reports have been transitioned and recent investigations are shifted to comparisons from reports extracted from outcomes. When LASEK is compared with PRK, the benefits of LASEK have been subsided. Objective studies indicate lesser benefits from LASEK. When pain is considered, there is no much difference found between PRK and LASEK. However, epithelial defects became larger on the third day with LASEK, which was low on the first day after the surgery. According to another study, there is no difference found in terms of vision recovery, pain or in re-epithelialization, when LASEK and PRK are considered. When low myopia is considered and LASIK and LASEK are compared, improvement of vision is slower after LASEK, significantly, but visual outcomes were close and comparable after three months. The same has been proved for myopia under -6.0D. however, with myopia over -6.0D, the LASIK predictability has been found to be more than that of LASEK.
In terms of accuracy, PRK and LASIK are found to be the same, though LASIK has faster recovery. And LASIK may result down for 2 or more visual acuity lines compared to PRK.
ASA has been performed and made refractive error corrections, successfully and influenced numerous lives of people. ASA is a much advanced procedure and most importantly the patient has to understand the pros and cons of it. The best key advantage of ASA is that it is a quite safe procedure and the results are long lasting. The key problem or drawback with it is that the recovery period is a bit longer than other laser refractive error correction surgeries. However, refractive errors are corrected much safely and effectively.