Options for correction of refractive error

for the students of optometry and other eye care professionals.

1. Other options for correction of Refractive Error By- ABHISHEK YADAV Optometrist Community ophthalmology

2. Most refractive errors can be corrected with eyeglasses, contact lenses, or surgery. Several factors are considered when choosing a corrective option : Age Cost Individual preference Lifestyle Occupation Other health conditions Severity and type of refractive error

3. A thin plastic lens placed directly on the anterior surface of the eye to correct visual defects. Types of contact lenses:  hard lenses ,  soft lenses ,  extended-wear lenses , and  disposable lenses . Contact lenses are available in soft materials and hard gas-permeable varieties. All types of contact lenses, including bifocals and those for astigmatism, are available as disposable and frequent replacement lenses. Contact lens

4. Is it still very new... Barraquar pioneered surgery in 1960 Invented by- JOSH BARRAQUAR Method- Keratomileusis HISTORY OF REFRACTIVE Sx

5. Several surgical procedures can correct refractive errors. The type and degree of refractive error determines whether or not a patient is a good candidate for surgery. There are risks involved and favorable outcomes are not guaranteed. Refractive Surgeries Types of surgery to correct refractive errors include: Radial keratotomy (RK) Photorefractive keratectomy (PRK) Astigmatic keratotomy (AK) Automated lamellar keratoplasty (ALK) Laser thermal keratoplasty (LTK) Conductive keratoplasty (CK) Intracorneal ring ( Intacs )  Laser in-situ keratomileusis (LASIK)

6. CRITERIA Age more than 20 years Stable refractive power for at least 6 months Last contact lens used 2 weeks in case of soft CL & 4 weeks in case of hard CL before the work up Corneal thickness more than 500 µ Intraocular pressure less than 20 mm of Hg HISTORY Type of correction used- spectacle/contact lens Need for surgery- cosmetic/professional/ any other H/O previous surgery- RK/ AK/ any other H/O previous ocular disease/ systemic disease/pregnancy/ ocular drug Systemic drugs-

7. Investigation to be done Visual acuity assessment UCVA, BCVA Snelle’s chart Routine eye examination Slit lamp examination Keratometry Manual Keratometry , VKG Pachymetry Ultrasonic Pachymeter Contrast sensitivity FACT Glare acuity Humphery auto-ref. Color vision Ishihara Topography Corneal curvature, Corneal thickness, Posterior elevation, Belin / Ambrosio display Orbscan , Pentacam Pupil size Mesopic , Photopic Corneal sensation Aesthesiometer Corneal diameter Orbscan II Tear film evaluation Schirmer’s test, BUT Auto refraction Refraction under proper cycloplegic Final PMT Dilated fundus examination Direct ophthalmoscope, Indirect ophthalmoscope Axial length Lenstar , IOL Master Applanation tonometry NCT, Goldman applanation tonometer

8. Radial keratotomy (RK) is a procedure used to correct mild myopia. Tiny spoke-like (radial) incisions called keratotomies are cut in the cornea with a diamond scalpel. The incisions cause the center of the cornea (optical zone) to flatten and changes the curve of the cornea. This reduces refraction. Because the cornea is cut, it takes several weeks to heal. This surgery was very common, but has been nearly replaced by LASIK.  Possible complications include: Changing vision during the first few months Infection Discomfort A weakened cornea that can rupture Trouble fitting contact lenses Glare around lights Clouding of the lens (cataract) Loss of vision  Radial keratotomy (RK )

9. Photorefractive keratectomy (PRK) is done with the same kind of excimer laser used for LASIK surgery. PRK is done to reshape the cornea to correct mild to moderate nearsightedness (myopia).  The excimer laser beam reshapes the cornea by removing tiny amounts of tissue from the outer surface. The procedure uses a computer to map the eye's surface and calculate how much tissue to remove. This surgery generally takes a few minutes. Because the cornea surface is cut, it takes several weeks to heal.  The most common side effects include: Eye pain that may last for several weeks Mild corneal haze right after surgery Glare or halos around lights for months after surgery  Photorefractive keratectomy (PRK) 

10. Astigmatic keratotomy (AK) is similar to radial keratotomy (RK). This surgery is used to correct astigmatism. Instead of making radial incisions, the eye surgeon makes cuts in the cornea in a curved pattern. Astigmatic keratotomy (AK)

11. Automated lamellar keratoplasty (ALK) is used for hyperopia and severe cases of myopia. For myopia, the eye surgeon cuts a flap across the front of the cornea with a tool called a microkeratome . The flap is folded to the side. A thin slice of tissue is removed from the surface of the cornea. This flattens the central cornea (optical zone) and reduces refraction. The flap is then put back in place. The flap reattaches itself without stitches.  During ALK for hyperopia , the eye surgeon makes a deeper incision into the cornea with the microkeratome to create a flap. The pressure in the eye causes the corneal surface to stretch and bulge. The bulging cornea improves the optical power. This corrects the hyperopia . The flap is then put back in place, where it reattaches without stitches.  Possible complications of ALK surgery include: Overcorrected or undercorrected vision Astigmatism Inability to wear contact lenses Loss of the corneal flap and need for a corneal graft Scarring Infection Vision loss Glare  Automated lamellar keratoplasty (ALK)   

12. Laser thermal keratoplasty (LTK) applies heat from a laser to the edges of the cornea. This shrinks the collagen fibers and reshapes the cornea. You must be age 40 or older to have this surgery. Laser thermal keratoplasty (LTK)

13. Conductive keratoplasty (CK) is used to correct mild to moderate hyperopia . It uses heat from low-level radio waves to shrink the collagen and change the shape of the cornea. A probe smaller than a strand of hair is used to apply the radio waves around the outer cornea. This creates a tight band that increases the curve of the cornea and improves vision. You must be age 40 or older to have this surgery.   Conductive keratoplasty (CK)

14. Intracorneal rings ( Intacs ) are used to treat mild myopia. They are microthin rings that are implanted into the cornea. Intacs shape of the curve of the cornea and improve vision. Intracorneal rings ( Intacs )

15. Laser in-situ keratomileusis (LASIK) is surgery to correct myopia, hyperopia , or astigmatism. The procedure reshapes the cornea with an excimer laser . LASIK surgery is done using a computer-controlled excimer cold laser, and a tool called a microkeratome or a femtosecond laser. With these tools, the surgeon cuts a flap in the center of the cornea to remove a thin layer of tissue. This causes the cornea to flatten. The flap is replaced without stitches and reattaches to the cornea within minutes.  In most cases, recovery from LASIK surgery is fast and involves minimal discomfort. Mild pain medicine and eye drops can help common after-effects of surgery such as: Dry eyes during healing Eye discomfort in the first 24 hours after surgery  Possible complications include: Overcorrected or under corrected vision Irregular astigmatism Corneal haze or glare Sensitivity to light Inability to wear contact lenses Loss of the corneal flap and need for a corneal graft Scarring Infection Blurry vision or vision loss  Laser in-situ keratomileusis (LASIK) 

16. Small incision lenticule extraction (SMILE) is a relatively new refractive procedure designed to treat a multitude of refractive errors such as myopia, hyperopia , presbyopia , and astigmatism. The procedure involves using a femtosecond laser to create a corneal lenticule which is extracted whole through a small incision without the use of an excimer laser. It is reported to achieve effects similar to laser-assisted in situ keratomileusis (LASIK) with excellent post-operative outcomes . SMILE laser eye surgery can correct up to -10.00 diopters (D) of nearsightedness. Small Incision Lenticule Extraction (SMILE )

17. SMILE can only correct nearsightedness, whereas LASIK and PRK can also correct significant amounts of farsightedness and astigmatism.  LASIK and PRK can treat  higher-order aberrations  (HOAs) that can affect night vision, whereas SMILE cannot. In fact, SMILE might increase HOAs to some degree .  if you have residual  refractive error  after a SMILE procedure and require additional vision correction, typically PRK would be the preferred enhancement procedure for best results. Limitations Of SMILE Laser Eye Surgery

18. During the ICL procedure, no corneal tissue is removed. The lens is inserted through a 3 mm self-sealing incision where no stitches are needed. An ICL is an artificial lens, similar in function to a contact lens, which is implanted in front of the eye’s natural lens but behind the iris so that it is practically invisible to outside observers. The ICL procedure corrects moderate to severe myopia (nearsightedness ). Widest power correction range from +10D to -20D with cylinder upto 6D Implantable Collamer Lens (ICL )

19. Advantages of ICL Preserves accommodation No corneal tissue removed Retains corneal asphericity Possibly retains contrast sensitivity Removable How does the ICL work? Similar to a contact lens Designed to remain inside the eye Doesn't get dirty and needs no maintenance unlike a contact lens Once-a-year visit to hospital recommended for examination

20. Superficial procedures PRK Range of applicability Myopia(–6D to -8D) Astigmatism (5D to 6D) Hyperopia up to +4D LASIK Range of applicability Myopia(–8D to -10D) Astigmatism(5D to 6D) Hyperopia (+3D to +4D) Phakic IOL Range of applicability Myopia of –8D or more Hyperopia of +4D or more Astigmatism upto 6D CCT AMOUNT OF REFRACTIVE ERROE 15µ=1D Flap size= 100µ Residual bed thickness should not be less than 280µ I CCT=500µ, -5D 5*15= 75µ + 100µ=175µ 500µ-175µ=325µ II CCT=500µ, -8D 8*15=120µ + 100µ=220µ 500µ-220µ=280µ SAFE CHOOSE OTHER OPTION

21. Most refractive eye surgeries are done on an outpatient basis. This means you go home the same day and don’t stay overnight in a hospital. Most surgeries last less than 1 hour. Before surgery: Arrange for someone to drop you off and pick you up after surgery. Don’t wear your contact lenses for as long as advised. This is to prevent any effect on the shape of the cornea. Don’t wear eye makeup for 2 days before surgery . Getting ready for surgery 

22. Refractive eye surgery involves minimal discomfort. The eye is usually numbed with eye drops before surgery. You may be awake during the surgery. Your eye may be kept open with an eye speculum. This is a spring-like device put between the eyelids.  After surgery, you may take pain medicine and use eye drops to ease discomfort. Your eye surgeon will give you more information. The most common after-effects of surgery include: Sensitivity to light Blurry vision Minor discomfort Dry eyes  Recovery time from surgery varies depending on the surgery. Full recovery may take days, weeks, or months. What to expect during and after surgery 

23. LASIK is the most common type of refractive eye surgery. Benefits of LASIK include: Less pain and faster recovery It can correct a wide range of myopia It can be repeated to correct vision further The eye is not weakened, because only one flap is cut into the cornea Little or no scarring of the cornea  But other types of surgery may be more suitable for your needs. And refractive eye surgery is not an option for everyone. Talk with your healthcare provider about your type of vision problem, and if surgery may be right for you.   Choosing a procedure

24. Orthokeratology is a process that uses specially designed  contact lens to temporarily reshape the contour of the  cornea  to reduce myopia (nearsightedness). Ortho-K( Orthoketratology )

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