Laser Refractive Surgery

Introduction

In recent years there are number of surgical techniques have been used to correct eyesight and diminish the need of glasses. Most often the surgery involves reshaping the cornea (transparent surface at the front of the eye) using a type of laser known as an excimer laser. We use different techniques to correct short sight (myopia), long sight (hypermetropia) and astigmatism. Some of them are PRK (photorefractive keratectomy), LASIK (laser in situ keratomileusis), LASEK (laser epithelial keratomileusis), Wavefront-guided LASIK . PRK has been used since the late 1980s but since the development of LASIK and LASEK is now mainly used for correcting low prescriptions. LASIK has been used since the mid-1990s and it is commonest method presently accessible in the UK, but it may not be offering high prescriptions. LASEK is alike to PRK but the outside layer (epithelium) of the cornea is retained as a flap. Retaining the epithelium is thought to prevent complications and speed up curing. Wavefront-guided LASIK is a technique used to diminish the natural irregularities of the eye. Mostly it is suitable for treatment, it is very useful for age 21 years or over, Healthy eyes, Good general health etc. but unsuitable for treatment under 21 years of age, Pregnancy / breast feeding, Patients on certain prescription drugs, such as oral steroids.

Accuracy with High Contrast

Laser Refractive Surgery is able to most high contrast acuity levels of myopia (nearsightedness), hyperopia (farsightedness), and astigmatism. Corrective lenses are the traditional method of treating refractive errors. Myopia is treated with concave lenses with minus or divergent power to focus light rays on the retina. Convex lenses with plus or convergent power help correct vision in the hyperopic eye, and cylindrical lenses are used to reduce the effect astigmatism. A loss of 1-2 Snellen line of visual acuity occurred in 13% of cases at one year, and 3% of eyes at the 10 year follow up. A common complication is a diurnal fluctuation in refractive error and hence visual acuity due to the structurally weakened cornea. The PERK researches encountered an increase in myopia greater than 0.50D in 30% of eyes. A study of a group of firefighter applicants who had undergone radial keratotomy, found a myopia shift occurring between morning and afternoon of -0.41 +/-0.33D compared to +0.06 +/- 0.42D in the control group.

Haze and Scarring

All patients build up at least a mild degree of corneal haze. During the first two to three months it has to away from haze and scarring because at that time it’s become dangerous and in most cases will disappear within six to twelve months. It is a bad for the Laser Refractive Surgery. Scientific publications indicate that the percentage of patients with haze and the degree of haze after laser treatment are related to the preoperative degree of myopia.

Accuracy with High Contrast Vs Haze and Scarring

Laser Refractive Surgery is able to most high contrast acuity levels of the same diseases and majority of surgeon is measure the only assessment of visual quality is high contrast acuity. A loss of two or more lines of best corrected visual acuity is considered significant. But on the other hand haze and scarring problem is very dangerous. The haze is not as good as during the first two to three months and in most cases also not as good as within six to twelve months it may cause will disappear. Haze and scarring are affect the vision of patients of short sight (myopia), long sight (hypermetropia) and astigmatism, but still this problem is occurred few of the cases like 1-3% of patients with low to moderate myopia and 5% or more patients with high or extreme myopia. That’s why we can take this risk and use this method as precious as possible.

Fast and Painless

The procedure is fast, and is generally painless. It is general to protect the eye at night time for the first week or so with a plastic shield. Antibiotic, anti-inflammatory (steroid) eye drops are given for use after surgery. The dosage and duration varies with patients and technique. Often up to six months in patients with dry eyes after Laser Refractive Surgery. Most patients have a reasonably comfortable period after surgery and are back at work within a few days. Depending on the vision alteration attempted, driving may be unsafe for 1-2 weeks. Tinted glasses with ultraviolet protection are needed when out in the sun for the first three months. There are significant variations in the way patients recover from the three (PRK, LASIK & LASEK) laser techniques. The following table highlights these variations in cases where the surgery has been uneventful and free of complications.

Laser Technique	PRK	LASIK	LASEK
Pain	Moderate to severe with significant patient variability	Minimal if any	Mild for the first 24 hours or so Light sensitivity
Recovery of useful vision	2-4 weeks	1-2 days	3-6 days
Stability of Vision	Usually 1-3 months, can take 6 months to a year in some cases	Usually 1 week to 1 month, in some complicated cases can take 3 to 9 months	1 week to 1 month, in some complicated cases can take 3 to 9 months
Contact lens	First 4-7 days	Usually not required. Used in cases where the surface epithelium is scratched.	Used for the first 3-4 days.
Return to work	Usually a week, can take longer	2-3 days	3-6 days

Instability of the Cornea

Ectasia is the forward full to bursting of the centre of the cornea resulting in abnormality of the optical surface and poor quality vision are found. It results from thinning and weakening of the cornea due to removal of too much tissue. It is consideration that 250 microns of untouched deep corneal tissue must remain to avoid ectasia following laser treatment. A Laser Refractive Surgery procedure will create a corneal flap (usually between 160 and 180 microns depth) and the laser treatment is then carried out on the remaining corneal tissue. The untouched deep corneal tissue is, therefore, thinner following a Laser Refractive Surgery procedure than a surface based laser dealing. Although the figure of 250 microns of untouched corneal tissue is generally taken as a safe level following LASIK treatment, there is relatively little scientific data to confirm this figure, which is tentative, and still the subject of debate. Also some of them patients complain of dry eye symptoms after LASIK because the surface nerves have been cut. Surface nerves usually take six months to regrow. The use of artificial tears (lubricant drops) alleviates the consciousness of irritation. Occasionally a temporary punctal plug is placed in the opening of the tear duct to slow the tear drainage from the eye.

Fast and painless Vs Instability of the cornea

Laser Refractive Surgery process is a very useful process than others. We can give many reason to support this like its take comparatively fast than the traditional method of surgery, All three method of Laser Refractive Surgery process (PRK, LASIK & LASEK) usually takes 1-6 days for recovery of useful visions, This method is also painful mostly first 24 hours or so light sensitivity, There are good stability of vision of 1 week to1 month sometimes its maybe increase till 3-6 months, it’s not necessary to use contact lens but sometimes its use for 3-7 days only, and finally we can return on the work in just 3-6 days. On the other hands we also have to consider the Instability of the cornea one of the measure problems in the Laser Refractive Surgery process. . The untouched deep corneal tissue is, therefore, thinner and weaker that is dangerous for us. The long term stability of refractive result has been drift towards hyperopia in up to the one thirds of patients after 4 years.

Conclusion

Laser Refractive Surgery is the main process. Safe and predictable, best results are obtained when using the most moderns methods: new lasers (femtosecond and customized excimer laser) with new algorithms served by a skilled surgeon in an outstanding center. The main purpose of this method is to review the characteristics required to perform accurate and precise laser refractive surgery relative to the current state of the art and the technology improvements needed in the future. From the above discussion we can say this is very suitable method for age 21 years or over, Healthy eyes ,Good general health ,People with reasonable expectations and Unsuitable for under 21 years of age, Pregnancy / breast feeding, Significant keratoconus and cataract or glaucoma and herpes eye infection. Besides its we use its easily because advantages of this method is comparatively more than its disadvantages.

Reference:

Laser Refractive Surgery, http://www.college-optometrists.org/