Refractive surgery for undergraduate simply

REFRACTIVE SURGERY
Amr Abdelrahman
Associate professor of Ophthalmology,
Faculty of Medicine, Minia University, Egypt
Clinical research fellow in Vissum
Corporación Alicante, Universidad Miguel
Hernández, Alicante, Spain

 Refractive surgery is the term used to
describe surgical procedures that correct
common vision problems:
 Myopia.
 Hyperopia.
 Astigmatism.
 Presbyopia.
*** TO reduce your dependence on
prescription eyeglasses and/or contact lenses.

MYOPIA:
 Light rays focus at a
point in front of
the retina.
 Difficulty reading road
signs and seeing
distant objects clearly.
 see well for close-up
tasks such as reading
and computer use.

HYPEROPIA
 Light rays entering the
eye focus behind
the retina.
 Can see distant objects
very well.
 Difficulty focusing on
objects that are up
close.

ASTIGMATISM
 Light focus in front of
and beyond the
retina.
 Causing both close
and distant objects to
appear blurry.

PRESPYOBIA
 The lens in the eye
loses flexibility.
 Cannot focus on
nearby objects.

GOAL OF REFRACTIVE SURGERY
 Optimal visual acuity.
 Optimal refraction (usually emmetropia).
 No complications.
NB: Complications during and after surgery
are of distinct concern as the eyes
undergoing refractive surgery are usually
healthy eyes.

TYPES OF REFRACTIVE SURGERY
 Subtractive procedures
with ablation of corneal
tissue (Laser refractive
surgery).
 Additive procedures
with implantation of
phakic IOL.

CORNEAL REFRACTIVE SURGERY
 LASIK.
 PRK.
 INCISIONAL REFRACTIVE PROCEDURES.
 INTRACORNEAL INLAYS.
 INTRACORNEAL RINGS.

 For myopia
 Refractive surgery techniques will reduce the curvature of a cornea
that is too steep so that the eye's focusing power is lessened.
 Images that are focused in front of the retina, due to a longer eye or
steep corneal curve, are pushed closer to or directly onto the retina
following surgery.
 For hyperopia
 Refractive surgery procedures that achieve a steeper cornea to
increase the eye's focusing power.
 Images that are focused beyond the retina, due to a short eye or flat
cornea, will be pulled closer to or directly onto the retina after
surgery.
 For astigmatism
 Refractive surgery techniques that selectively reshape portions of
an irregular cornea to make it smooth and symmetrical.
 The result is that images focus clearly on the retina.

LASER REFRACTIVE
SURGERY ( LASIK & PRK )
The latest generation of excimer laser platforms
 Smaller spot size.
 High speed tracker.
 Pupil monitoring.
 Online pachymetry.
- All of which provided superior treatment with
significant improvement of induced post-operative high
order aberrations (HOA) and control of thermal damage.
- Patient Satisfaction 98.5% after 7 months.

Safety limitations for LASIK
 Age <18 ( except if anisometropia).
 Error (stable refraction).
 Myopia up to -12 D.
 Hyperopia up to +6 D.
 Astigmatism up to 5 D.
 Pachymetry < 480 microns.
 Residual stromal bed 300 microns.

COMPLICATIONS OF LASIK
 Refractive Imprecision.
 Infectious keratitis.
 Ocular surface syndrome.
 Interface complications:
 Diffuse lamellar keratitis.
 Pressure-Induced Stromal
Keratopathy.
 Central Toxic Keratopathy.
 Epithelial Ingrowth.

COMPLICATIONS OF LASIK
 Flap complications:
 Bowman strip and button hole in
LASIK flaps.
 Early flap displacement after
LASIK.
 Keratectasia.
 High order aberrations after
LASIK.
 Retinal complications.

Photo refractive keratectomy
PRK
small error (> 6 D) small pachymetry

COMPLICATIONS OF PRK
 Refractive Imprecision.
 Infectious keratitis.
 Haze.
 Keratectasia.

Incisional refractive procedures
Relax steep corneal meridian
 Astigmatic keratotomy
(correct 4- 6 D).
 Limbal relaxing
incisions (correct 1-2
D).

Surgical correction of prespyobia
 LASIK (Supracor)
 Intracorneal inlays
- The Presbia Flexivue Microlens
- The Kamra Inlay
- The Raindrop Near Vision Inlay
 Multifocal IOL
 Monovision

Intracorneal inlays
For prespyobia correction
 The Presbia Flexivue Microlens
- Hydrogel implant works by changing
the refractive index of the cornea.
- The central zone of the implant is
neutral or plano, and has no refractive
power. It allows light rays from distant
source to focus on the retina,
preserving distance vision.
- The central neutral zone is surrounded
by one circular zone of additional
positive power, which focus light rays
from near objects on the retina, and
improve near vision. Their design is
similar to multifocal contact lens or
intraocular lens.

Intracorneal inlays
 The Kamra Inlay
- Opaque, ring shaped with a
central aperture.
- Based on the principle of pinhole
optics.
- It improves near vision by
increasing the depth of focus.
- The ring blocks the peripheral
light rays and allows only the
central rays to pass unhindered.

Intracorneal inlays
 The Raindrop Near Vision Inlay
- Designed to change the curvature of the
anterior corneal surface.
- They are placed anteriorly in the cornea,
either under a 130-150 microns flap, or
in a stromal pocket, to create a
hyperprolate anterior corneal surface.
- They correct presbyopia by increasing
the curvature of the central part of the
anterior corneal surface.
- Paracentral light rays ,travel through the
thinner portion of the inlay and enable
viewing distant objects while near
objects can be viewed clearly through
the central curved part of the cornea.

Intracorneal rings
 Indications
- Keratoconus
- Post LASIK keratectasia
 Prerequisite
- Clear cornea
- Pachymetry < 400 microns

PHAKIC INTRAOCULAR LENSES
 Two available phakic IOLs now:
- Iris-fixated (Artisan, Artiflex).
- posterior chamber implantable Collamer lens
(ICL).
 Range of correction :
- Myopia up to 23D.
- Hyperopia up to 21D.
- Astigmatism up to 7.00D (toric).
 Fast visual recovery.
 preservation of accommodation.
 Reversibility.

PHAKIC INTRAOCULAR LENSES
 Safety limitations:
- Flat iris
- Endothelial cell count (ECC) of ≥2,100 cell/mm²
- Scotopic pupil diameter <6.0mm
- AC depth of ≥2.8mm

Complications of phakic IOL
 Pupil ovalization.
 Endothelial cell loss.
 Infection.
 Glaucoma.
 Cataract.
 Uveitis.
 IOL Dislocation.
 Retinal complications.

Correction of high errors
 Phakic IOL (young age).
 Clear lens extraction (refractive lens exchange):
- Myopia (< 50 years).
- Hyperopia (< 40 years).
 LASIK
- Myopia up to -12.

Correction of Astigmatism
 LASIK.
 Incisional refractive procedures.
 Toric phakic IOL.
 Toric IOL.

TAKE A HOME MESSAGE
 Refractive surgery provides a variety of
elective procedures to be performed in
otherwise healthy eyes.
 The knowledge of their possible
complications is mandatory to select the best
surgical option with successful outcomes.

TAKE A HOME MESSAGE
 In Refractive Surgery there is no risk-free surgical procedure.
 The evaluation of the risk/benefit ratio should be part of a
continuous process of excellence in the practice of Refractive
Surgery
 Refractive surgery risks and benefits should be evaluated
individually in order to choose the surgical approach properly
 Not only incidence, but also morbidity of each possible
complication should be considered in this choice
 Decision making in refractive procedure is an individualized
process that should be based on scientific knowledge, patient’s
characteristics and surgeon experience.

Refractive surgery for undergraduate simply

Refractive surgery for undergraduate simply

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