What is refractive surgery?

Refractive surgery is an eye surgery that reduces dependency on visual aids such as spectacles and contact lenses. It is usually considered cosmetic surgery and is opted for better aesthetics by many.

Who are suitable candidates for laser refractive surgery? 

Refractive surgery is not medically indicated and an individual decides to get it done electively. Here is a list of criteria for an ideal laser refractive surgery candidate.

1. Age between 18-40: The glass number usually stabilizes by the age of 18 years, therefore it is not recommended in individuals less than 18 years who may observe an increase in the power later.

In individuals more than 40 years of age, lens aging starts which may require them to wear reading glasses or undergo surgery in case of cataract. 

2. Stable glass number for 6 months-1 year: If the glass power is fluctuating, then a change in refraction after surgery will affect the postoperative outcome.

3. Refractive error: Usually, an individual with a myopia of -8 to -10D, hypermetropia of +6 D, or astigmatism up to 4D is ideal (depending upon the operating surgeon and technique used).

4. Corneal thickness of more than 500 microns: Laser refractive surgery requires ablating the corneal surface.  Therefore if the corneas are already thin, then ablating it may result in corneal thinning, a condition known as corneal ectasia.

5. No dryness of eyes: This procedure itself can cause dryness. Therefore if the individual is already suffering from dry eyes, then surgery in such patients can cause severe dry eyes, which are more difficult to treat.

6. No history of any recent eye infection:  History of eye infection must be told to the doctor and only after the eyes are fully recovered, the procedure is done to avoid unnecessary post-op complications.

Contraindications of laser refractive surgery

Like any other surgery, refractive surgery has its list too of contraindicated conditions that make a candidate ineligible for the surgery. These are

1. Patients with diseases of cornea (outer transparent layer of the eye) such as infection, ulceration, keratoconus, or cone-like cornea.

2. Thin corneas 

3. Unstable refractive error

4. Pregnant and lactating women

5. Uncontrolled diabetes or hypertension

6. Uncontrolled glaucoma 

7. Collagenopathies 

8. Keloid tendencies

9. Certain eyelid and ocular surface disorder 

10. Degenerative retinal conditions  

What are the different types of refractive surgeries?

The various types of refractive surgeries are:

1. PRK 

2. LASIK

3. Contoura Vision LASIK or customized wavefront-guided LASIK

4. ReLEx SMILE

5. Phakic IOL

6. Refractive lens exchange

1. PRK

Procedure: 

PRK or Photorefractive Keratectomy is done under topical anesthesia or numbing eye drops, the outermost layer or the epithelium of the cornea is scraped off either manually or by using alcohol so that the laser applied has better penetration into the deeper layers of the cornea.

Next, the excimer laser ablates the predetermined amount of corneal tissue depending on the refractive error of the patient, this simply means that the laser applied, reshapes the cornea, making it either flat or steep.

It is usually done in small refractive errors or when the patient is ineligible for LASIK due to lesser corneal thickness or irregular corneal surface. 

Trans PRK is a single-step alternative to traditional PRK wherein instead of using any blade or alcohol, the epithelium is removed by the same excimer laser that is used to ablate the cornea.

Therefore, the surgical time is reduced and the post-op recovery is also faster. 

What to expect post-procedure: 

The superficial layer of the cornea, when scraped off, exposes the nerve endings, which causes pain once the effect of numbing eye drops wears off. A bandage contact lens is placed to relieve this pain but some amount of discomfort is expected. 

The skin grows back in around 3 days and this contact lens is then removed. Visual recovery also takes around 3-4 days.

2. LASIK (Laser-Assisted In situ Keratomileusis) 

Procedure: 

LASIK is the most commonly performed refractive surgery wherein instead of scraping off the outer layer, a flap is created in the cornea, which is retracted, and just like in PRK, the excimer laser is delivered to ablate corneal tissue.  After the procedure, the flap is positioned back.

This is of two types, depending on the flap.

• Microkeratome Lasik or blade Lasik: The flap is made mechanically by the surgeon using a device called a microkeratome.
• Bladeless Lasik: The flap is made by a femtosecond laser. The flap-related complications are comparatively lesser in this type but it is also more expensive

What to expect

Unlike PRK, LASIK is painless even post-procedure and the visual recovery is on the same day or within the next 24 hours. Creating the flap during the procedure cuts some corneal nerves, therefore the corneal sensations are reduced and dryness may ensue post-LASIK.

3. Customized wavefront-guided or Contoura Vision LASIK: 

This ground-breaking technology is based on the fact that each cornea is unique, just like your fingerprints. 

The corneal surface is not smooth and these irregularities at microscopic levels affect the quality of vision.

Procedure: 

In this procedure,  a flap is created first, just like in LASIK. 

This flap can be created by a blade called a microkeratome or by a femtosecond laser. What is different from the conventional LASIK is that this customized LASIK uses a machine to make a map of the irregularities on the cornea. 

The laser is then applied to these imperfections to smoothen them out, resulting in an optically perfect corneal surface so that the patient can enjoy high-quality vision. 

What to expect

This procedure gives excellent results in terms of visual acuity and clarity. Some patients have reported having better color perception and contrast sensitivity too. However, some amount of dryness is to be expected.

4. ReLEx SMILE: (Refractive Lenticule Extraction, Small Incision Lenticule Extraction)

Procedure: 

ReLEx SMILE is a flapless surgery, wherein the femtosecond laser creates a lenticule within the cornea, which is then extracted through a small incision. Hence the corneal tissue is not ablated, like in LASIK and PRK. 

What to expect

Since it is a flapless surgery, there are fewer chances of reduced corneal sensation and dryness. But the visual recovery is usually later than LASIK because of some interface haze in the initial period of the procedure. 

DIFFERENCE BETWEEN PRK, LASIK, AND RELEX SMILE 

5. Phakic IOL/ICL (implantable collamer lens)

Procedure: 

Unlike other refractive surgery where the laser is used to reshape the cornea, in phakic IOL (ICL or IPCL, etc), an intraocular lens or IOL of calculated power is implanted behind the iris, and in front of the normal crystalline lens. 

This procedure can be done in patients who are not suitable for laser refractive procedures such as those who have thin corneas or who have high refractive power or who suffer from severe dryness.

ICL is the only refractive procedure that is reversible because IOL can be extracted if necessary.  

What to expect

One might experience increased sensitivity to light, glare, halos, etc. Vision may be slightly blurry but with time, it will start to stabilize. The eyes take time to get adjusted to another lens. This usually takes around 2 weeks to months. 

The risks are slightly more in this type of refractive procedure. Although rare, the IOL can touch the lens and cause cataract, or it may touch the cornea and cause clouding of the cornea. It may even block the drainage angle and cause raised intraocular pressure, in which case, there will be pain and one should report to their doctor immediately.

6. Refractive lens exchange:

This procedure is rarely done.  In refractive lens exchange, as the name suggests, the natural, clear lens is extracted and replaced by the intraocular lens of calculated power (unlike in phakic IOL, wherein the natural, clear lens is left untouched),. 

Pre laser procedure testing:

Before planning the laser refractive surgery, the following tests are done to see if you are suitable for the laser procedure.

1. Glass number is confirmed by automated testing and manual testing 

2. Lensometer detects the power of your current spectacles. Any major difference between the glass power and the refraction by manual testing requires further assessment.  

3. Automated testing of IOP or the pressure in your eyes. 

4. Slit-lamp examination to see the general eye condition

5. Dry eye testing

6. Corneal topography (Pentacam/orb scan/Sirius scan/Galili): These tests give a detailed picture of the cornea, which gives information about point-to-point thickness, curvature, and elevations on the cornea. 

7. Dilated eye examination: This includes cycloplegic refraction and detailed peripheral retina examination to rule out any weak spots in the retina.

Post-op care:

Like any other surgery, post-op care after a refractive procedure is an important factor to determine its outcome. Therefore, following the doctor’s advice is of utmost importance during this period. The post-op care includes: 

1. Do not rub eyes

2. Do not lift heavy weights for a month  

3. Do not take a head bath, avoid water going in eyes for 7—10 days

4. Use drops diligently and as instructed by your doctor

5. Make sure to turn up for post-op visits which are usually on the next day, 1st week, 1st month, and 3rd month of surgery.

QUICK SUMMARY

There are many surgical options to get rid of glasses and even though these refractive surgeries are usually safe and effective, they also have some associated risks, like any other surgery, such as flap-related problems in LASIK, cornea, and lens-related problems in ICL, etc. 

Everyone has their own needs and it goes for the eyes as well.  Each person’s eye is unique and requires different approaches and treatments.  So it’s best to discuss the pros and cons of each surgery with your doctor, to arrive at the right procedure for your eyes. 

If you have any doubts or queries regarding this topic, please feel free to drop us a message.

Disclaimer: The content on this site is for general information only and should not be used as a substitute for professional medical advice.