Excimer laser subepithelial keratomileusis for correction of high myopia
【Abstract】 Objective To evaluate the excimer laser
subepithelial keratomileusis (LASEK) the efficacy of correction of high myopia. Methods 27 cases of patients with
high myopia (54 eyes), preoperative spherical equivalent of myopia as -6.00 -14.00? D, the average (-8.75 ? 1.27) D.
Cornea epithelial recovery time, postoperative visual acuity, corneal subepithelial haze (Haze), corneal topography and refraction number of follow-up period of 6 months. Results All patients had no eye surgery and postoperative severe complications. Corneal epithelial repair time average (3.71 ?
0.26) d. After 3? D, uncorrected visual acuity was ? 0.5 were
48 (88.9%), ? 0.8 were 19 (35.2%), after 7? D, uncorrected
visual acuity was ? 0.5 54 (100.0%), ? 0.8 were 47 eyes
(87.0%), after 6 months, uncorrected visual acuity are reached or exceeded the preoperative best corrected visual acuity. After 1,3,6 months of spherical equivalent were -0.50 +0.50? D
between the Corneal Haze after 1,3,6 months, rates were 13 (24.1%), 7 ( 13.0%), 2 eyes (3.7%), but less than 2, does not affect visual acuity. Conclusion LASEK for high myopia and visual acuity better stability, no obvious corneal subepithelial haze and refractive regression.
Key words Excimer laser subepithelial keratomileusis for myopia and corneal subepithelial haze vision
Abstract: Objective To investigate the effect of laser
assisted subepithelial keratectomy (LASEK) for the correction of high myopia. Methods LASEK was performed on 54 eyes of 27 myopia patients. The preoperative mean spherical (MSE) was -
6.00 -14.00? D, average (-8.75 ? 1.27) D. Postoperative
uncorrected visual acuity (UCVA), refractive power, time of
epithelial healing and corneal haze were all recorded. Patients were followed up for 6 months. Results No serious complications occurred. The epithelium was healed in a mean
(3.71 ? 0.26) d. 3 days after the operations, the UCVA ? 0.5
was found in 88.9% (48/54) and ? 0.8 in 35.2% (19/54). 7 days
after the operations, the UCVA ? 0.5 was found in 100%
(54/54) and ? 0.8 in 87.0% (47/54). 6 months after the
operations the UCVA was equal with or better than the preoperative best corrected visual acuity (BCVA). 1, 3 and 6 months after the operations, corneal haze was found in 13 eyes (24.1%), 7 eyes (13.0%) and 2 eyes (3.7%) respectively but it was below grade 2 and had no effect on visual acuity.
Conclusion LASEK is a safe, effective, stable and predictable surgery for myopia.
Key words: Laser assisted subepithelial
keratomileusis; Myopia; Visual acuity; Corneal haze
1999 Camellin [1,2] proposed and named excimer laser
subepithelial keratomileusis (laser assisted subepithelial
keratomileusis, LASEK), for the excimer laser correction of refractive errors opened a new research direction. LASEK treatment of low to moderate myopia of the efficacy and safety
has been recognized [1 3], we aim to explore the treatment of high myopia LASEK safety, efficacy, stability and predictability.
1 Data and methods
1.1 The clinical data of 18 selected month in 2006, Qingdao University Medical College Hospital Eye Bank LASEK for high myopic patients 27 patients (54), male 11 (22), female 16 cases (32); 18 37 years old, an average of 25 years of age; preoperative myopic spherical equivalent of -6.00 -14.00? D,
the average (-8.75 ? 1.27) D; preoperative best corrected
visual acuity (best corrected visual acuity, BCVA) 48 Yan meet or exceed 0.8,6 Eye 0.6 0.7; myopic refractive stability in two years or more.
1.2 preoperative examination of the request excimer laser treatment of myopia, by asking medical history and pre-
operative examination, including uncorrected visual acuity (uncorrected visual acuity, UCVA), best corrected visual acuity (BCVA), dominant eye, pupil diameter, corneal
topography , IOP, slit-lamp, corneal thickness and fundus
examination. That must be removed in patients with keratoconus, eye inflammation, glaucoma, retinal tears and other eye diseases, mental health, no diabetes, hyperthyroidism, and autoimmune diseases, no pregnancy and lactation are. Those who wear soft contact lenses before
surgery to stop wearing more than 2 weeks.
1.3 surgical methods used, as the cool eagle eye excimer laser system (Lumenis Inc., Germany), LASIK (Wuxi Kangming Medical Devices Co., Ltd.). Conventional cleaning and disinfection of conjunctival sac shop towel. Ao Buka
hydrochloride 0.4% eye drops for eye drops every 5? Min 1 times, a total of 2 times. Will the preparation of a good 20% ethanol solution 0.2? Ml injection of a diameter of 8? Mm epithelial trephine in, 20 25? S after blood-sucking sponge
with alcohol, and dry thoroughly washed with a balanced solution. Hoe with epithelial separation from 1 to 11 on the flap side edge separation of its rolled-up fold at 12 o'clock.
Across the traditional track position PRK laser cutting. Rinse
corneal surface of the needle will be on the flap with the washing reset. Wearing contact lenses. After 15? Min within the Code will give Shu eyedrops (0.3% tobramycin 0.1% dexamethasone) every 5? Min 1 times, a total of 3 times.
1.4 follow-up after the first postoperative day 1, Shu drops drops of iodine must be 4 times / d. Continuous 7 10? D later, changed to 0.1% Eye Drops Long Ai fluoride drops, 4 times / d, to after 1 month. Reduced to once a month after the withdrawal. Postoperative day 1, artificial tears (bFGF, Aili,
or tears contingent) eye drops eye drops, 4 times / d, to 2 weeks after operation, after 3 times / d, to 4 months after operation. Respectively after the first 1,3,7,14? D, 1,2,3,6-
month review, including visual acuity, intraocular pressure,
slit-lamp and so on. After 1,3,6 months follow topography and refraction.
1.5 Statistical analysis using SPSS11.0 statistical software, using t test of the data for statistical analysis.
2 Results
In 27 cases, 54 had no serious intraoperative and
postoperative complications occurred. Multi-emergence of early
postoperative ocular pain, photophobia, tearing, foreign body sensation such as irritation. Corneal epithelium after the repair the above-mentioned symptoms disappeared completely.
2.1 corneal epithelial repair time after 1? D slit-lamp
examination, see corneal epithelial edema, postoperative 3 5? D angle lenses removed membrane epithelial healing. At this point corneal epithelial healing, corneal transparency. Corneal epithelial repair time average (3.71 ? 0.26) d.
2.2 vision after 3? D, uncorrected visual acuity reached or exceeded 0.5 in 88.9% (48/54), 0.8 to 35.2% (19/54); after 7? D, uncorrected visual acuity reached or exceeded 0.5 for the 100 % (54/54), 0.8 to 87.0% (47/54); after 6 months, uncorrected visual acuity are reached or exceeded the preoperative best corrected visual acuity.
2.3 diopter of residual refraction after 1,3,6 months of examination, all patients postoperative spherical equivalent
eyes were -0.50? D +0.50? D between the postoperative
refractive stability, and no refractive regression.
2.4 subepithelial corneal haze (Haze) Corneal Haze grading applications is 5 classification [4], 0: cornea completely transparent, non-turbid; 1: In the slit lamp shines into this method can be found using Mild punctate opacities; 2: In the slit lamp easy to find poor, does not affect the observation of the iris texture; 3: corneal opacity, iris texture affect the observation; 4: corneal opacities obviously
not a glimpse of iris texture. Corneal Haze after 1,3,6-month
rates were 13 (24.1%), 7 eyes (13.0%), 2 eyes (3.7%), but less than 2, does not affect visual acuity.
3 Discussion
3.1 Basic principle and advantages of LASEK is between
PRK (excimer laser photorefractive keratectomy,
photorefractive keratectomy) and LASIK (laser in situ keratomileusis Laser in Situ Keratomileusis) is a new surgical method [ 5,6], is through the application of 20% ethanol soaked corneal epithelium, so that the basal corneal
epithelial cells and corneal elastic layer separation, and then flap flip, conventional PRK on the flap and then will be reset, and wearing contact lenses to protect the flap. The
difference with the LASIK mainly LASEK is the creation of a
corneal flap, while LASIK was the production of a joint part of the corneal epithelial flap (referred to as the corneal flap). The PRK in terms of, LASEK integrity of the cornea flap, can be reduced within a short time after traditional PRK corneal epithelial barrier defect caused by pain, to accelerate the effective recovery of visual acuity and reduce the chances of Haze; the same time, LASEK corneal epithelial barrier in its own exists, for reducing the risk of infection is also valuable. LASIK is relatively speaking, first of all, LASEK surgery is not used microkeratome, to avoid cutting corneal flap in LASIK surgery complications; and secondly, the cornea flap is only 50 70? μm, while the corneal flap in
LASIK surgery is usually need to 130 160? μm, which would
address the past, due to postoperative residual stromal bed thickness can not accept the limitations of surgical problems. Hence its postoperative corneal ectasia, a lower incidence of keratoconus, refractive regression less; In addition, because
of corneal nerve endings cut LASEK surgery less reflex tear secretion on the impact of small, dry eye after a short time. In short, LASEK for small palpebral fissure, small cornea, corneal curvature is too high or too flat, especially the thin
cornea, special professional myopia is a relatively safe procedure preferred method [7,8]. Reposted elsewhere in the paper for free download http://
3.2 Evaluation of the study diopter of myopia of not more than -14.0? D of high myopia. All eyes 6 months after surgery,
corneal Haze occurrence rate was only 3.7% (2 / 54); uncorrected visual acuity are reached or exceeded the preoperative best corrected visual acuity and stable. Namely, LASEK for high myopia also have good safety, efficacy, stability and predictability. Data show a high degree of myopia LASEK Corneal Haze in the incidence rate is still high [9], serious Haze could lead to refractive regression, affecting visual function. Thus a high degree of myopia is still holding a more cautious attitude. Reported in the
literature [10], to prevent and reduce the Haze effective measures include: (1) surgery to save as much as possible the activity of corneal epithelial cells to maintain the flap and the former elastic layer of smooth and complete; (2) after a
reasonable use of steroids. The author believes that strict control of intraoperative concentration of alcohol (no more than 20%) and corneal epithelium soaking time (no more than
30? S), gently peel the cornea flap, to avoid valve rupture, free, debris and limitations of corneal epithelium defects, are key to successful operation. After hormone application and observation of intraocular pressure is also very important. In addition, high-performance excimer laser systems, such as cutting a smooth interface and high-frequency fast-cutting,
but also preventive and effective measures to reduce the Haze one.
3.3 shortcomings First, because individual differences in ethanol response, surgery is necessary to do a complete and dynamic corneal flap is more difficult to require surgical
patients who have a good base [10,11]. Secondly, after 23 eye in the sky there are foreign body sensation, photophobia, tearing, best visual acuity recovery long, medication long cycle, review times, a few cases were corticosteroid
complications such as glaucoma and corneal Haze. Compared with no pain after LASIK, visual acuity and rapid recovery after halting the hormones and so on, there are still many
shortcomings, especially with today's fast, comfortable personalized service concept, its clinical applications are subject to certain restrictions.
In conclusion, LASEK for high myopia treatment is safe, effective, good stability and predictability of high surgical
method, especially for thin flap of corneal and LASIK surgery system, a certain degree of difficulty of a small palpebral fissure, small cornea, corneal curvature is too high or too flat who underwent surgery to reduce the risk of expanding the
scope of myopia treatment, the more secure is the preferred surgical method. Also be pointed out that: (1) The key to successful operation is the production activity of corneal flap; (2), corneal thickness and degree of myopia corrected
within a certain effectiveness, still strictly controlled surgical indication; (3) Relative LASIK is concerned, LASEK postoperative pain, visual recovery long, long period of medication and observation characteristics such as their clinical applications are subject to certain restrictions.
LASEK for myopia for the long-term stability and long-term
corneal changes, it remains to be seen.
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