Refractive Eye Surgery
Excimer laser ablation is done under a partial-thickness lamellar corneal flap.
- Automated lamellar keratoplasty (ALK): The surgeon uses an instrument called a microkeratome to cut a thin flap of the corneal tissue. The flap is lifted like a hinged door, targeted tissue is removed from the corneal stroma, again with the microkeratome, and then the flap is replaced.
- Laser-assisted in situ Keratomileusis (LASIK): While performing the LASIK eye surgery in Pune at MSEH, our surgeon uses either a microkeratome or a femtosecond laser to cut a flap of the corneal tissue (usually with a thickness of 100–180 micrometers). The flap is lifted like a hinged door, but in contrast to ALK, the targeted tissue is removed from the corneal stroma with an excimer laser. The flap is subsequently replaced. When the flap is created using an IntraLase brand femtosecond laser, the method is called IntraLASIK; other femtosecond lasers such as the Ziemer create a flap similarly. Proponents of this method assert its superiority over "traditional" LASIK, but there have been no conclusive independent studies to prove that this is a true statement. One supposed criticism of the use of the microkeratome is the deposition of microscopic metal fragments from the blade into the surgical site.
- ReLEx: In ReLEx flex, a femtosecond laser cuts a lenticule within the corneal stroma. Afterwards, a LASIK-like flap is cut, which can be lifted to access the lenticule. This is removed through manual dissection using a blunt spatula and forceps. The newer "ReLEx smile" technique is without a flap, and uses only a small peripheral incision, from which the refractive lenticule can be removed, leaving the anterior lamellae of the cornea intact. No excimer laser is used in the "ReLEx-procedures".
The excimer laser is used by the best retina specialist in Pune at MSEH to ablate the most anterior portion of the corneal stroma. These procedures do not require a partial thickness cut into the stroma. Surface ablation methods differ only in the way the epithelial layer is handled.
- Photorefractive keratectomy (PRK) is an outpatient procedure generally performed with local anesthetic eye drops (as with LASIK/LASEK) . It is a type of refractive surgery which reshapes the cornea by removing microscopic amounts of tissue from the corneal stroma, using a computer-controlled beam of light (excimer laser). The difference from LASIK is that the top layer of the epithelium is removed (and a bandage contact lens is used), so no flap is created. Recovery time is longer with PRK than with LASIK, though the final outcome (after 3 months) is about the same (very good). More recently, customized ablation has been performed with LASIK, LASEK, and PRK.
- Laser Assisted Sub-Epithelium Keratomileusis (LASEK) is a procedure that also changes the shape of the cornea using an excimer laser to ablate the tissue from the corneal stroma, under the corneal epithelium, which is kept mostly intact to act as a natural bandage. The surgeon uses an alcohol solution to loosen then lift a thin layer of the epithelium with a trephine blade (usually with a thickness of 50 micrometers). During the weeks following LASEK, the epithelium heals, leaving no permanent flap in the cornea. This healing process can involve discomfort comparable to that with PRK.
- EPI-LASIK is a new technique similar to LASEK that uses an epi-keratome (rather than a trephine blade and alcohol), to remove the top layer of the epithelium (usually with thickness of 50 micrometers), which is subsequently replaced. For some people it can provide better results than regular LASEK in that it avoids the possibility of negative effects from the alcohol, and recovery may involve less discomfort.
- Customized Transepithelial No-touch (C-TEN) is an innovative strategy for corneal surgery that avoids any corneal manipulation via a complete laser-assisted trans-epithelial approach. Since C-TEN is planned on the morphology of each individual eye, it can treat a large variety of corneal pathologies from refractive to therapeutic
- Radial keratotomy (RK), developed by Russian ophthalmologist Svyatoslav Fyodorov in 1974, uses spoke-shaped incisions, always made with a diamond knife, to alter the shape of the cornea and reduce myopia or astigmatism; this technique is, in medium to high diopters, usually replaced by other refractive methods.
- Mini Asymmetric Radial Keratotomy (MARK), developed by Italian ophthalmologist Marco Abbondanza in 1993 and improved in 2005. It consists of a series of micro incisions, always made with a diamond knife, designed to cause a controlled cicatrisation of the cornea, which changes its thickness and shape. This procedure, if done properly, is able to cure the astigmatism and the first and second stage of the keratoconus, avoiding the cornea transplant.
- Arcuate keratotomy (AK) is similar to radial keratotomy, but the incisions on the cornea are done at the periphery of the cornea. Arcuate keratotomy is used to correct astigmatism. Although most incisional procedures are replaced nowadays by Lasik, AK is still used in some special cases (correction of residual astigmatism after a keratoplasty procedure or during cataract surgery).
- Limbal relaxing incisions (LRI) are incisions near the outer edge of the iris, used to correct minor astigmatism (typically less than 2 diopters). This is often performed in conjunction with an Intraocular Lens implantation.
Intermediate uveitis normally only affects one eye. Less common is the presence of pain and photophobia.
- Radial Keratocoagulation, also known as Radial Thermokeratoplasty, was invented in 1985 by Svyatoslav Fyodorov and is used to correct hyperopia by putting a ring of 8 or 16 small burns surrounding the pupil, and steepen the cornea with a ring of collagen constriction. It can also be used to treat selected types of astigmatism. It is now generally replaced by laser thermal keratoplasty/laser thermokeratoplasty.
- Laser thermal keratoplasty (LTK) is a non-touch thermal keratoplasty performed with a Holmium laser, while conductive keratoplasty (CK) is thermal keratoplasty performed with a high-frequency electric probe. Thermal keratoplasty can also be used to improve presbyopia or reading vision after age 40. Intrastromal corneal ring segments (Intacs) are approved by FDA for treatment of low degrees of myopia.
- Phakic intraocular lens (PIOL) implantation inside the eye can also be used to change refractive errors. The newest type of intervention is a type of PIOL called the implantable collamer lens (ICL) which uses a biocompatible flexible lens which can be inserted in the eye via a 2mm incision. The ICL is used to correct myopia ranging from −3 to −20 diopters.
- Generally refractive surgery can be broadly divided into : corneal surgery, scleral surgery, lens related surgery (including phakic IOL implantation, clear lens extraction, photophacoreduction and photophacomodulation for correction of pesbyopia)
- For presbyopia correction, a corneal inlay consisting of a porous black ring surrounding a small clear aperture was originally developed by D. Miller and a group at Acufocus. The inlay is placed under a lasik flap or in a stromal pocket
Using mid-IR and UV lasers for the treatment of presbyopia by scleral tissue ablation was first proposed and patented by J.T. Lin, PhD in US patents #6,258,082 (in 2001)and #6,824,540 (in 2004).
- Research conducted by the Magill Research Center for Vision Correction, Medical University of South Carolina, showed that the overall patient satisfaction rate after primary LASIK surgery was 95.4%. They further differentiated between myopic LASIK (95.3%) and hyperopic LASIK (96.3%). They concluded that the vast majority (95.4%) of patients were satisfied with their outcome after LASIK surgery.
- Ophthalmologists specialized in laser eye surgery in Pune at our hospital use various approaches to analyze the results of refractive surgery, and alter their techniques to provide better results in the future. Some of these approaches are programmed into the devices ophthalmologists use to measure the refraction of the eye and the shape of the cornea, such as corneal topography.
- While refractive surgery in Pune at MSEH is becoming more affordable and safe, it may not be recommended for everybody. People with certain eye diseases involving the cornea or retina, pregnant women, and patients who have medical conditions such as glaucoma, diabetes, uncontrolled vascular disease, or autoimmune disease are not good candidates for refractive surgery.
- Keratoconus, a progressive thinning of the cornea, is a common corneal disorder. Keratoconus occurring after refractive surgery is called Corneal Ectasia. It is believed that additional thinning of the cornea via refractive surgery may contribute to advancement of the disease that may lead to the need for a corneal transplant. Therefore, keratoconus is a contraindication to refractive surgery. Corneal topography and pachymetry are used to screen for abnormal corneas. Furthermore, some people's eye shape may not permit effective refractive surgery without removing excessive amounts of corneal tissue. Hence patients considering laser eye surgery in Pune at MSEH are always suggested for a full eye examination.
- Although the risk of complications is decreasing compared to the early days of refractive surgery, there is still a small chance for serious problems. These include vision problems such as ghosting, halos, starbursts, double-vision, and dry-eye syndrome. With procedures that create a permanent flap in the cornea (such as LASIK), there is also the possibility of accidental traumatic flap displacement years after the surgery, with potentially disastrous results if not given prompt medical attention.
- For patients with strabismus, risks of complications such as diplopia and/or increased strabismus angle need to be evaluated carefully. In case both refractive surgery and strabismus surgery are to be performed, it is recommended that the refractive surgery be done first.
- Pediatric refractive surgery involves other risks than refractive surgery on adults, yet it may be indicated especially for children whose cognitive or visual development is failing due to refractive error, in particular in cases of bilateral high refractive error, anisometropia, anisometric amblyopia or accommodative esotropia.
- Interventions on young children may require general anesthesia in order to avoid risks due to involuntary movement, and children have a higher risk of rubbing or manipulating their eyes post-surgically. Changes to refractive error occurring during normal age development need to be accounted for, and children have a higher risk of developing postoperative corneal haze. This risk is particularly relevant with relation to myopic children
- One study evaluated the outcome of LASEK interventions on 53 children aged 10 months to 16 years who had anisometropic amblyopia. The choice of LASEK was made as it was felt it would give fewer complications than LASIK and less post-operative pain than PRK. In the intervention, which was performed under general anesthesia, the refractive error in the weaker eye was corrected to balance the refractive error of the other eye. Strabismus surgery was performed later if required. After one year, over 60 % had improved in best corrected visual acuity (BCVA) in the weaker eye. Notably, over 80 % showed stereopsis post-operatively whereas less than 40 % had showed stereopsis before.
- Aside corneal refractive procedures (LASIK, PRK and LASEK), also introcular refractive procedures (phakic intraocular lenses, refractive lens exchange and clear lens extraction) are performed on children
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