This document summarizes different types of corneal refractive surgery procedures. It describes the anatomy and physiology of the cornea, including its layers and shape. It then discusses various laser eye surgery procedures like LASIK, PRK, LASEK, Epi-LASIK, and intrastromal corneal ring implants. For each procedure, it provides a brief overview and lists the advantages and disadvantages. The goal of these surgeries is to correct refractive errors like myopia, hyperopia, and astigmatism by reshaping the cornea through ablation or incisions.

1. CORNEAL
REFRACTIVE
SURGERY

2. Corneal Physiology
 Transparent, dome shaped, outermost layer that covers the front of the eye.
 Provides greatest amount refractive power to the eye.
 Avascular, relies on atmosphere for oxygen and aqueous humor for its
nutritional needs.
 Corneal surface is kept smooth by
constant moistening action of tears.

3. Layers of Cornea
Epithelium (55µm).
 It evenly distributes the nutrients to other layers.
 It maintains stromal dehydration.
Stroma (470µm)
 Collagen fibers arrangement are responsible
for corneal strength, optical characters.
Endothelium (5µm).
 It stretches to cover the dead cells,
which reduces the cell density and impact
on fluid regulation.
 It pumps the excess fluid from stroma.

4. Shape of Cornea
 Slightly oval
 Horizontal & vertical dimensions are 11mm & 12 mm app.
 Pupil diameter ranges from 2mm to 6mm, which reduces optical zone of
cornea to its central 6mm.
 Peripheral cornea is thicker than central cornea.

5. Pachymetry
 It is the process of measuring the thickness of the cornea.
 Corneal Pachymetry is essential prior to a LASIK procedure for ensuring
sufficient corneal thickness to prevent abnormal bulging of the cornea, a
side effect known as ectasia.
 Ultrasonic & Optical pachymetry.
 It also helps in finding the development of glaucoma when combined with
standard measurement of IOP .
 Corneal thickness is 560 microns.

6. Corneal Topography
 It is a process of mapping the surface curvature of the cornea.
 It is to produce a detailed description of the shape and power of
the cornea because shape determines the visual ability.

7. Refractive Laser Surgery

8. LASIK
Advantages:
 Pain free recovery.
 Quick restoration of eyesight.
 Better result for severe
short sight.
Disadvantages:
 Dry eyes.
 Halos, starburst.
 Loss of contrast sensitivity.
 Thick corneal flap (100-180 microns).

9. Femto LASIK

10. Photorefractive Keratectomy
Used to correct mild to moderate
 Myopia.
 Hyperopia.
 Astigmatism.
Advantages:
 Highly accurate for myopia.
 80% patients have 20/20 vision
Disadvantages:
 Mild discomfort including minor
eye irritation.
 Dry eyes.

11. LASEK
Advantages:
 No flap complications.
 Causes less dry eyes than
LASIK.
 Finer trephine blade is used
instead of microkeratome.
 Good for patient with
thin cornea.
Disadvantages:
 May cause more pain and
discomfort than LASIK.
 Dry eyes.
 Longer recovery time than
LASIK.

12. Epi-Lasik
Advantages:
 Less complications to corneal nerves.
Disadvantages:
 Dry eyes.
 Poor night vision.

13. Intrastromal Corneal Implants
Used to treat
 Myopia.
 Keratoconus.
 It has two semicircular rings made of PMMA.
Advantages:
 Easily removable.
 Small incision.
Disadvantages:
 Vision disorder.
 Problem with night vision.

14. Thank You
Prepared by
Ghose Mohamed
Medicals International
Riyadh
KSA