Intraocular lens

CURRENT TIME’S IOL

VASIUR RAHMANR.P. Centre for ophthalmic science

All India Institute of Medical Science

New Delhi.

BIRTH OF IOL

First Person-

Sir Harold Ridley

Royal Air force pilots who

sustained eye injury during

world war second involving

PMMA as wind shield material

did not show any rejection or

foreign body reaction.

First IOL

Generations of IOLs

8 generations till now.

Rigid posterior chamber belongs to Vth generation.

Foldable IOL- VIth generation

Multifocal IOL- VIIth genration

Phakic refractive IOLs &

accomodative IOLs- VIIIth generation

Material for IOL

• Poly methyl Methacrylate (PMMA) -

Rigid, chemically stable compound.

• Silicon hydrogel & Acrylic-

– foldable material

– Phacoemulsification & MICS

PMMA material

Structure of IOL

ACIOL PCIOL

Traditional IOLs

• Traditional IOLs are

monofocal, meaning they offer

vision at one distance only (far,

intermediate or near).

• patient must wear eyeglasses

or contact lenses in order to

read, use a computer or view

objects at arm's length.

Premium IOLs:

• Aspheric IOLs

• Toric IOLs

• Multifocal IOLs

• Accomodating IOLs

Aspheric IOL

• slightly flatter in the periphery and are

designed to provide better contrast

sensitivity

• Reduce the abrassions

• Gives better visual aquiety

Chromatic Aberration

• Uneven focusing of an optical system which causes wavelengths of light to have different focal points thus decreasing optical performance

• Chromatic aberration from IOLs may negatively impact:

– Visual acuity

– Contrast sensitivity

– Functional vision

• The chromatic aberration of optical materials can be expressed by their

Abbe numbers

• The higher the Abbe number the lower the chromatic aberration and the

higher the retinal image quality

Abbe number

• The Abbe number, also known as

the V-number or constringence of

a transparent material, is a

measure of the

material's dispersion (variation of

refractive index with wavelength) in

relation to the refractive index, with

high values of V indicating low

dispersion (low chromatic

aberration). It is named after Ernst

Abbe (1840–1905), the German

physicist who defined it

Multifocal IOLsA multifocal lens implant focuses light from distance and near

simultaneously. This feature addresses both distant and

near vision and makes the recipient less dependent on

glasses or contact lenses

• Currently available MF use either Diffractive or Refractive

optics

refractive multifocal IOL

• Two zone lens

• Central near vision segment

surrounded by distant vision

segment

• Disadvantage in bright sunlight

• Annulus type-

• Central portion contain distant

vision refraction

• Refractive provides excellent

intermediate and distance vision

diffractive multifocal IOL

• Near and distant correction is put in each of concentric ring

• Utilize the principle of wave optics

• Step height is in the range of wavelength of light

• 82% focus on 2 major foci

• 41% for near vision

• 41% for distant vision

• 18 % scattered & lost

Disadvantage of MF

• Light intensity

• Contrast sensitivity

• Off axis aberrations

• glare and haloes around lights at night, a

feature that is inherent to multifocal lenses

• most patients find that they get used to this

phenomenon with time and the glare and

haloes become less obvious

Toric IOLs

• designed to correct

astigmatism at corneal

plane.

• Correct astigmatism at

corneal plane only.

• Only one vision is corrected.

Vision with

cataractVision with

normal IOLVision with Toric

IOL

IOL for Refractive Error

• . This type of IOL is also

called Phakic intraocular

lens (PIOL) and the

crystalline lens is not

removed.

• alternative to LASIK

• (PIOLs) can be either

spheric or toric—the latter

is used for astigmatic eyes

Accommodating IOLs• Accommodating IOLs interact with ciliary

muscles and zonules using hinges at both ends

to ―latch on‖ and move forward and backward

inside the eye.

• provide excellent vision at all distances (far,

intermediate, and near)

• same quality of distant vision as in monofocal

lens

• No loss of contrast sensitivity

• No halos at night

• So Advantage over MF

Fact• Patients should expect to achieve "social" near vision with the

accommodative IOL.

• For example-watch faces, cell phones, price tags, grocery labels,

computer screen text and magazine size print under average

lighting conditions.

• Patients whose main goal is to sit and read small print in dim

lighting conditions for prolonged periods of time or do other very

precise near work are likely to be disappointed with the unaided

near vision available from the accommodative IOLs.

• Of course, reading glasses may be worn to improve the near

vision for precise or prolonged near tasks

• healing mechanism nay interfare.

For your kind attention