Prof. Dr. Mohamed Wagih El-Deeb Ph.D., FRCS (Ed) lAssociate Professor of Ophthalmology, Cairo University. lFellow of Royal College of Surgeons, Edinburgh. lFellow of Vissum Instituto Oftalmologico d'Alicante, Spain. lMember of European and American Society for Cataract and Refractive Surgery. lConsultant of Ophthalmology and Refractive Surgery, Boushahri Specialized Polyclinic, Kuwait. Baghdad Street – Building 38 same as Boushahri Seema Pharmacy, Opposite Suleiman Al-Luhaib Mosque - Tel : 1888877
www.boushahricp.com
EXCIMER LASER & NEW MODALITIES Boushahri_clinic
IN VISION CORRECTION SURGERIES LASER Surgery is incorporated now in many medical fields, what about LASER in Ophthalmology?
For the last 50 years, LASER has been introduced for most of the surgical specialties. Ophthalmology had a great share of the LASER surgeries. It is well known that LASER has different wave lengths ranging from red to violet and that each color has its own application. For example, Argon green LASER is used for diabetic retinopathy and the barrage treatment of flat retinal breaks. Nd.YAG LASER is used for peripheral iridectomy of glaucoma and posterior capsulotomy after cataract extraction. In the early 1990s, EXCIMER LASER emerged in the field of refractive surgery (vision correction surgeries). It was used before in the manufacturing of computer micro-ships. Dr. Trokel had discovered that the high penetration power can be used in corneal resurfacing and hence, change of curvature and improvement of vision. It was approved by FDA in 1993. Since that time and up until now, LASER has opened a new horizon for refractive surgery. So far, more than 20 million patients have undergone refractive LASER surgeries.
So, what are the different types of LASER vision correction surgeries and what are the indications of each one?
-In the early 1990s, Photo-Refractive Keratectomy (PRK) was the first refractive surgery to be introduced where the superficial layer of the cornea was removed and LASER was applied. -By the mid 1990s, the famous Laser Assisted Insitu Kerato-meleusis (LASIK) emerged and become the most popular refractive procedure. It avoided the side effects of PRK, particularly the pain and long recovery time. -By the late 1990s, another innovation had been prescribed. LASEK is an alcohol-assisted surface treatment which repositions the superficial layer decreasing post-operative pain. -By the early 2000s, FEMTO-LASER technology emerged as one of the greatest breakthrough innovations in refractive surgery. This technology has implemented the FEMTOSECOND THEORY of the famous Egyptian physician Dr. Ahmed Zuwail, who was rewarded the Nobel prize in 1999. Creation of LASIK cut is performed through extremely fast LASER beam. -In 2003, the new technology of EPI-LASIK was added to the upgrade of vision correction surgery using a special fine epithelial separator to create a very thin flap of 50 microns. -Finally, a new surface treatment profile : Trans-Epithelial PRK is available now in New Mowasat hospital. By that technology, even the superficial layer of the cornea is removed by citypageskuwait.com
LASER. So, it is named ONE STEP LASER. All surface treatments (PRK, LASEK and EPILASIK & TRANS-PRK) are used in thin or irregular cornea, severe dry eye or athletic patients who are more predisposed to traumatic eye injuries. People sometimes have wrong information about side effects of LASER vision correction surgery.
So what is the true scientific background?
At first, we have to admit that LASER vision correction surgery is like any other surgeries with side effects. Those drawbacks are much predicted, minimized and managed with well experienced surgeons and good case selection. Most of the common LASER side effects are mild, temporary and case dependent. -Night visual symptoms (glare, haloes and ghost images) are the most common drawbacks due to change of the corneal curvature after refractive surgery and the time lapse for brain re-adaptation for the new corneal shape. Basically, it fades within 2-3 months but it depends also upon other factors. Scotopic pupil diameter (maximum diameter at night) controls the duration and severity of these symptoms in a direct relationship. Recent LASER technologies (WAVE FRONT ABLATION) minimize corneal curvature changes and treat the higher order aberrations to great extent. Subsequently, the night symptoms are much reduced.
-Dry Eye: This is also a very common side effect caused by decrease of the tear film secretion by the main lacrimal gland. It is more
severe with LASIK compared to PRK and EPILASIK. Usually, it disappears within the first few months with avoidance of intense sunlight. -Visual Regression: This is usually one of the most irritating issues for most of the patients. Usually we can say that regression is not properly understood, but may be caused by corneal cells regrowth and proliferation. Actually, about 90-95% of patients don’t need another surgery. The remaining 5-10% (usually high errors patients) may need another re-treatment if they still have enough corneal thickness. Otherwise, they can have glasses but with better (lower) power than before.
It is well know that LASER refractive surgery should be postponed until the visual stability. So what is the condition in case of high and progressive errors in children? Actually, refractive surgery is postponed until the age of visual maturation which is usually between 18-21 years. It is also important to confirm the stability of vision through at least 3 visits of follow up with 6 months interval. But in children with anisomyopia (large difference between two eyes more
than 3-4 diopters), glasses are not a good solution because the visual center cannot do proper fusion with that difference. Also the idea of using contact lenses is not practical in children aged 3-8 years old. Hence performing LASIK for pediatric age group is an exception in such conditions to save the eye from amblyopia. LASIK is done under general anesthesia and followed up closely together with a pediatric Ophthalmologist.
Are all the patients good candidates for LASER surgery and what are the alternative options?
Basically, we have to differentiate between two categories: 1st: Cases with frank LASIK contraindications (frankly clinical, aborted or subclinical keratoconus). 2nd: Cases of high degree of errors which is beyond LASIK correction range (high myopia, hyperopia and astigmatism). With the 1st group, it is forbidden to do LASIK and each case will be properly evaluated to choose the best surgical options - either Corneal Cross Linking (CXL), Intra Corneal Rings (ICR), Lens implants or Keratoplasty (corneal grafting). With the 2nd group, lens implants are implanted and fixed inside the eye and there are many types of lenses; either (Phakic IOLs) which keeps the original lens, Cachet angle supported, Artisan iris fixated and ICL posterior chamber phakic IOL. We can also remove the normal lens and replace it by a new implant. (Pseudo-phakic IOLs). Surgical decision depends mainly on the patient’s data (refraction, corneal topography, thickness, anterior chamber depth etc). All types of implant share in being easy and short surgical procedures (15-20 min). They are also very safe and give effective results without compromising the weak or thin cornea.
Finally, what are the possible side effects of the implants and how do you compare their results with LASIK regarding vision improvement and stability?
As we have mentioned before, there is NO surgery without side effects. But those drawbacks can be avoided or minimized a lot with the precise preoperative evaluation and regular post-operative follow up. Lens implants have excellent visual results as in LASIK from the first day because most of
the patients have a high degree of errors. Implants may be even superior to LASER with less post-operative visual night symptoms, less dryness and more stable long-term visual performance with less possibility of regression or deterioration.