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….