Chapter 18: Refractive Surgery Concepts and Procedures

Question 1

Refractive Surgery

Answer 1

A surgical procedures aimed at reducing or eliminating the need for corrective lenses

Question 2

Radial Keratotomy

Answer 2

A refractive surgical procedure that employs anterior radial incisions in the cornea to flatten its curvature and reduce myopia. First introduced in Japan in 1940’s, but is no longer used today because of the possibility of irreversible corneal edema

Question 3

Corneal Edema

Answer 3

Swelling of corneal tissue

Question 4

Bullous Keratopathy

Answer 4

Swelling of the corneal tissue severe enough to create blisters on the surface of the cornea and decreased vision

Question 5

Excimer Laser

Answer 5

An ultraviolet laser instrument that uses fluoride and argon gases to vaporize or ablate tissue

Question 6

Photorefractive Keratectomy

Answer 6

A refractive surgical procedure that employs and excimer laser to reshape the corneal curvature after removing epithelium

Question 7

Indications and Contraindications for Refractive Surgery

Answer 7

Indications:
1) Occupational goals
2) Cosmetic or recreational desires
3) Intolerance of contacts or glasses

Contraindications:
1) Unrealistic expectations
2) Uncontrolled ocular disease (uncontrolled glaucoma, cataract, dry eye), immunosuppressed patients (cancer chemotherapy patients)

Question 8

Refraction Evaluation in Myopic Patients

Answer 8

Myopic eyes have images focused in front of the retina, so we use minus lenses in order to move the image back onto the retina

Question 9

Refraction Evaluation in Hyperopic Patients

Answer 9

Hyperopic eyes have images focused behind the retina, so we use plus lenses in order to bring the image forward onto the retina

Question 10

Refraction Evaluation in Patients with Astigmatism

Answer 10

Astigmatism is caused by a not quite circular curvature of the cornea. Refraction seeks to correct the abnormal curvature of the cornea.
Refractive surgery seeks to correct and balance out the steep and flat meridians.

Question 11

Refractive Evaluation in Presbyopic Patients

Answer 11

Presbyopic patients are beginning to have an increased difficulty with seeing near objects, and refraction seeks to correct this by adding additional reading power to the lower portion of the glasses (multifocal lenses) in order to allow sight up close.
Refractive surgery in these patients means that they are trading dependence on glasses for distance vision, to dependence on glasses for near vision.

Question 12

Wavefront Analysis

Answer 12

The determination of higher order optical aberrations. The procedure measures optical errors other than those that can be detected with routine refraction

Question 13

Corneal Topography

Answer 13

A device that records the surface terrain of the cornea, used to detect aberrations of the contour, as well as regular and irregular astigmatism

Question 14

Aberrometry

Answer 14

The measurement of optical aberrations of the visual system using a device called a wavefront analyzer or an aberrometer
Also called wavefront analysis

Question 15

Phakic IOLs

Answer 15

These are intraocular lenses implanted without removing the natural lens. This is usually done in the cases of high myopic patients

Question 16

Pupil Size Measurements

Answer 16

Keratorefractive surgeries are done at the central point of the pupil, and so pupil measurements both Mesopic (measured in dim lighting) and scotopic (dark-adapted vision).

Question 17

Mesopic

Answer 17

Referring to eyesight under dim lighting conditions

Question 18

Scotopic

Answer 18

Referring to eyesight under dark-adapted conditions

Question 19

Optical Zone

Answer 19

The major or central focusing area of the cornea (or any lens)

Question 20

Pachymetry and Keratometry

Answer 20

Pachymetry is essential to determine if the patient has abnormally thin corneas prior to surgery and Keratometry is essential to identify abnormally steep or fat corneas, which could result in an increased risk of corneal ectasia

Question 21

Laser in situ Keratomileusis (LASIK)

Answer 21

A refractive laser procedure performed after temporary removal of the surface epithelium and basement membrane from the corneal stroma and replacing it after the laser ablations

Question 22

Corneal Ectasia

Answer 22

A group of non-inflammatory eye conditions that cause the cornea to gradually thin and bulge outward, changing its shape

Question 23

Photorefractive Keratectomy (PRK)

Answer 23

A refractive surgical procedure that employs the excimer laser to reshape the corneal curvature after removing epithelium

Question 24

Laser Subepithelial Keratomileusis (LASEK)

Answer 24

A refractive laser procedure using a microkeratome or femtosecond laser keratome to raise a corneal flap followed by ablation of the stromal bed with an excimer laser

Question 25

Epithelial Laser in situ Keratomileusis (Epi-LASIK)

Answer 25

A type of LASIK surgery in with epithelial sheet is created and separated with its basement membrane from the stroma with a device similar to a microkeratome

Question 26

Astigmatic Keratotomy

Answer 26

A surgical technique for correcting astigmatism that employs transverse or arcuate incisions perpendicular to the steepest meridian of the cornea

Question 27

Limbal Relaxing Incisions

Answer 27

A partial-thickness corneal incision made in the periphery of the cornea to treat astigmatism

Question 28

Phototherapeutic Keratectomy (PTK)

Answer 28

An excimer laser is employed to ablate the anterior corneal surface to correct irregular astigmatism, scarring, or other superficial abnormalities

Question 29

Conductive Keratoplasty (CK)

Answer 29

A solid-states infrared laser refractive surgical procedure employed to create heat shrinkage of the peripheral corneal stroma, thereby steepening the central cornea and reducing hyperopia

Question 30

Intrastromal Corneal Ring Segments

Answer 30

A surgical technique of placing thin plastic half-circle ring segments in the mid-peripheral cornea to flatten the curvature of the central cornea and reduce myopia