Intra ocular lens

INTRA-OCULAR LENSVISHNU NARAYANAN

What is intraocular lens?

• An artificial lens implanted in the eyes• Replaces the crystalline lens• To correct the optical power of the eyes

following:-

Lens being clouded by

cataractRefractive surgery

Primary vs secondary implantation

• Primary implantation – use of IOLs during surgery for cataract

• Secondary implantation – implantation of IOL to correct aphakia in a previosly operated eye

Parts of an IOL• OPTIC Part of the lens that focuses light on the retina.

• HAPTIC Small filaments connected to the optic that hold the lens in place in the eye

HAPTENOPTIC

HISTORY OF IOL

• K

THE FIRST IOL!!• PMMA made lens – 45 year

old female after performing extracapsular cataract extraction

• Disc shaped bi-convex design• Site- posterior chamber• First generation IOL

EVOLUTION OF IOLs1. First generation IOLs• Ridley lenses• Disadvantages – posterior dislocation poor surgical technique2. Second generation IOLs• Rigid and semi-rigid anterior chamber IOLs• Advantages – reduce posterior dislocation• Disadvantage – corneal decompensation UGH syndrome

3. Third generation IOLs

• Iris supported lens• Advantages- less corneal decompensation• Disadvantages – iris chaffing pupillary distortion c/c inflammation cystoid macular edema

4. Fourth generation IOLs

• Modern anterior chamber lens• Flexible loops and multiple point fixation• Advantages – more stable, better design, less

complications• Disadvantages – anterior chamber is not the

physiological site for IOL

5. Fifth generation IOLs

• PMMA lenses• Foldable and small incision lenses

MATERIALS USED FOR INTRAOCULAR LENSES

Optic materials

1.Non-foldable-rigid IOL• Polymethyl

methacrylate(PMMA)

2.Foldable IOL• Silicone• Hydrophobic acrylic• Hydrophilic acrylic

3.Rollable/Ultra-thin IOL• hydrogel

Haptic materials

• Polypropylene• PMMA• Acrylic

POSITIONING OF IOL

1. Posterior chamber implantation

• Ciliary sulcus fixation

• In the bag fixation

• Scleral fixation

Eg:- modified C loop type IOL

Ciliary sulcus fixation

In-the-bag fixation

Scleral IOL

2. Anterior chamber implantation

• angle supported IOLs

• Kelman multiflex type IOL

3. Iris- fixated lens

• Fixed on the iris with claws,loops or sutures

• Eg- Singh and Worst’s iris claw lens

Different types of haptic angulation relative to the plane of optic:-

For posterior chamber lens:-• 100 anterior angulation to keep the optic

part away from the pupil.

For anterior chamber lens:-• Posteriorly angulated lens to vault the

intraocular lens away from the pupil

FOCUSSING ABILITY OF IOLs

1. Unifocal intraocular lens

• Lens with unifocal power• Can have problem with near vision

2.Multifocal IOLs

• Simultaneous vision lenses

• Based on either refractive or diffractive optics

• Psuedoaccomodation lens

3.Accomodative IOLs

• Exhibit anterior movement of optic to improve near vision

Special function IOLs

TORIC IOLs• Correct any associated astigmatism

ASPHERIC IOLs• Reduce spherical aberration

ANIRIDIA IOLs• Cover the defects of aniridia or

partial iris loss as in trauma• Has a black diaphragm over the

optic

PIGGYBACK IOLs• An IOL piggybacking onto an

existing IOL or simultaneous implantation of 2 IOLs

BLUE LIGHT FILTERING IOLs• Lenses are yellow colored to screen out UV

Light and blue spectrum• Reduced risk of age related macular

degeneration

PHOTOCHROMATIC IOLs• UV absorbing photo chromes

IMPLANTABLE MINIATURE TELESCOPE• Miniature implantable Galilean

telescope• Implanted in posterior chamber• Contains number of micro lenses

in the optic which gives a magnification of about 3 at the central visual field

• Used to treat macular degeneration

TELESCOPIC IOLs

• New generation miniature telescopes which uses 2 mirrors instead of lens to provide magnification with minimum loss of peripheral vision

Phakic IOLs

• IOLs used to correct myopia with the eye’s natural lens being untouched

• Implantable contact lenses1. Angle supported lens2. Iris – fixated lens3. Sulcus supported lens

BIOMETRY

THEORETICAL FORMULAE• Binkhorst formula• Colenbrander’s formula• Gull strand’s formula• Hoffer’s formula

EMPERICAL FORMULAE• Modified Sanders-Retzlaff-Kraff formula• SRK II• SRK III• SRK T• Haigis formula

Binkhorst formula

• E= [N/(L-C)] – NK/(N-KC)]

E• Emmetropic IOL power

L• Axial length of the eye

K• Corneal dioptric power

C

N

• Psuedophakic length of anterior chamber

• Refractive index of aqueous and vitreous humor

Modified Sanders-Retzlaff-Kraff formula

• Based on the statistical correlation between calculated and observed refractive error after ocular implantation.

Modified SRK Formula• E=A - 2.5L - 0.9K• Parameters used in the formula are

estimated by• A-scan ultrasonographic sonometry and

keratometry• Instrument - biometer

E=A - 2.5L - 0.9K

E:Emmetropic power of eye

A:Predetermined constant of IOL

L: Axial length in mm

K:Average of keratometry readings

• Power ( I )required to produce Required post operative refraction ( R ) ,

I = E – cr R

• cr – empirical constant cr = 1 if E < 14 cr = 1.25 if E > 14

Complications of IOL implantation

• Mechanical damage to the IOL• Dislocation• Bullous keratopathy• Posterior capsule rupture• Anterior capsule opacification• Posterior capsule opacification• Calcium deposits within the optic of hydrophilic intraocular

lens• Adherence• UGH syndrome• Sunset syndrome

Sunset syndrome

“Lens of the future”-liquid injectable IOLs

• A new IOL concept that combines an acrylicIOL with a liquid, injectable IOL may somedayallow patients to retain accommodation.

• Following IOL implantation, liquid IOL is injected and capsular bag is inflated fully and IOL kept in place

• Mechanism- forward movement and thickening of lens

THANK YOU….