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LASEK, A New Procedure?
L-A-S-E-K, pronounced lay-SEK, and also known as epi-LASIK, is a variant of the original excimer laser vision correction procedure called photo-refractive keratectomy (PRK); the procedure first approved for simple myopia by the FDA in 1995. It differs from LASIK in that no flap is created and that the sculpting of the corneal tissue which results in visual improvement is delivered in its more superficial layers. Visual recovery is similar to PRK and is not as rapid as that which occurs with LASIK, taking 3-7 days in comparison with the typical 24 hour recovery with LASIK.
Because of the rich innervation of the cornea, marked discomfort occurs whenever the cornea has a break in its surface layer (abrasion). However, since the protective surface layer of the cornea, called the epithelium, grows back when disrupted, it must be removed to deliver the corrective laser treatment. It then takes anywhere between two and four days for this re-growth of the epithelium to occur. The typical post-op regimen for PRK includes the use of analgesic, antibiotic, and anti-inflammatory drops in conjunction with a bandage contact lens, ice, and oral pain relievers. Though this regimen makes the first 24-48 hours post-operative course in PRK relatively comfortable for most individuals, it was at least in part due to the stark contrast of 2-3 hours of minor irritation that most LASIK patients experience that most surgeons largely abandoned PRK as the laser vision correction procedure of choice by 1999.
One measure that many laser surgeons never discovered to narrow this comfort gap, however, is the practice of sending their patients home with anesthetic eye drop to use hourly for the first 24 hours. This will almost entire eliminate most patient complaints of discomfort following PRK.
For some patients who have thinner corneas LASIK is not an option. As mentioned previously, the sculpting of the cornea in LASIK takes place following the creation of a corneal flap. If the cornea is not thick enough to make this flap, remove the requisite amount of tissue and still leave enough tissue behind to maintain the structural integrity of the cornea, the patient must seek alternative means of vision correction.
LASEK differs from PRK only in its handling of the epithelium. In PRK, the epithelium is typically removed with the laser (laser-scrape), a rotary brush, or manually with a scalpel: In LASEK, an attempt is made to preserve the epithelium. Perhaps a better acronym would be ESPRK for epithelial-sparing PRK. To perform LASEK a metallic ring with a semi-sharp edge for 300¡ is used to cookie cut a "hinged flap" of epithelium while simultaneously creating a well for a dilute alcohol preparation that softens the epithelium's attachment to the underlying tissue. A hoe-shaped instrument is then used to peel back the epithelium, the laser treatment is delivered, and the epithelium in replaced. A bandage contact is inserted to protect the loose tissue and it heals back in place and smoothes out over a period of days to weeks.
PRK (Photo Refractive Keratectomy)
The surgeon first removes the surface cells of the cornea. The laser is then used to sculpt the underlying tissue. The surface cells regenerate over the course of 48-72 hours under a contact bandage lens. To use the analogy of the cornea as a 400-page book with a fifty-page thick cover on either side, the cover is discarded and the first pages of the book are removed. The cover then grows back after the procedure.
There is no discomfort at all during this procedure. Following the procedure, expect a gritty sensation with some mild to moderate discomfort in the first few days, which will improve with time. Not all patients experience significant discomfort since topical analgesics (advil-like drops) and a contact lens are used as a bandage for the first few days as the surface layer fills in to cover over the exposed corneal nerve endings. Anesthesia is provided during the first 24 hours in the event of severe discomfort. All discomfort should be completely resolved within 2-3 days except in the rarest of cases.
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