An Intra-ocular lens (IOL) is an artificial aid surgically implanted in the living eye to restore sharpness of vision, frequently after removal of a cataract.
History of IOL
- Casaamata – (1795)- attempted Intraocular implant
- Harold Ridley (1949) — first successful human intraocular lens implant
- During World War II, noticed intraocular foreign bodies of acrylic fragments from airplane canopies were tolerated.
- Performed on November 29, 1949, at St. Thomas Hospital in London.
- High incidence of complication – discontinued his original design
- Pioneering work of Cornelius Binkhorst in Holland and E. Epstein in South Africa – interest in this modality rekindled.
- Charles Kelman – Phacoemulsification – early 1970.
- A major turning point of IOLs acceptance – 1974.
- In 1976, Steven Shearing – first compressible posterior chamber lens
Pseudophakic vs. Aphakic vision
- Enlarged visual field,
- Less magnification,
- Better stereopsis,
- Rapid visual rehabilitation
Types of intraocular lens
- Anterior chamber IOL,
- Iris-fixated IOLs,
- Posterior chamber IOLs,
- Sulcus-fixated IOLs.
Ideal implant material
- High optical quality
- High index of refraction
- Ease of manufacture
- Lack of inflammatory reaction
- Lack of antigenicity
- Lack of carcinogenicity
- Ease of sterilization
- Can be used to create multi-focal lenses
- Surface modification – reduce the immediate postoperative inflammation in high-risk eyes.
- Graft Hydrogel to its surface
- Heparin coating
- Fluorocarbon or Teflon coating of the lens.
- Surface passivation
- PMMA is not totally inert
- Hard, rigid material
- Monomer – toxic to eye
- Nd: YAG laser has potential to damage PMMA optic.
- Hydrophobic – corneal endothelial cells adhere to its surface.
- Larger incision required
2. New Materials:
- Foldable Acrylics
Foldable IOL Advantage
- Less than PMMA lenses.
- Silicone IOL no finishing or polishing is required.
- Have transmissions of >90% in 400-800nm range.
- Excellent surface properties that reduce reflection and glare.
Bio-stability and chemical purity:
- Resistant to hydrolytic and oxidative degradation.
- Harmful chemicals fully extracted during the making.
- Low adhesion – low pigmentary and inflammatory deposits.
Sterilization and laser effects:
- Autoclaved safely avoiding harmful gases or chemicals.
- Exposure of silicone IOL to LASER doesn’t release any harmful chemicals.
Foldable IOL disadvantage:
Biocompatibility of materials other than silicones:
- Silicone has been proved to be biocompatible.Mechanical strength:
Tensile strength considerably lower than that of PMMA
- care must be taken while handling soft IOL.
Loop and Haptic materials�
- One piece with PMMA haptic or soft biomaterials
IOL Suitable for implantation
- Must be within 0.25D of stated power
- Proper shape and configuration within 0.25mm
- Uniform, smooth surfaces, and edges
- Chemically pure without any residual monomer, ethylene oxide, or contaminants
- Clean of surface debris; and be sterile.
- Ethylene oxide most commonly use
- Alternative method Sodium hydroxide
Design characteristics, optic size, and shape
- IOL optic size ranges from 4.5-7.5mm
- Optic size of 6.5-7.0mm is popular among surgeons performing planned ECCE.
- Lenses with round optic of 5.5-6.0mm are currently favored by many phacoemulsification surgeons.
- Some surgeons- prefer oval lens 5mm x 6mm optics.
Large optic size IOL
- Less likelihood of decentration.
- Less optical aberration.
- Reduced likelihood – pupillary capture.
Small optic IOL
- Most popular in phacoemulsification and continuous tear anterior capsulotomy.
- Minimal displacement in a bag- favored by most phaco surgeons.
- Potential for optical aberration from lens edges.
Shape of IOL
The biconvex lens seems to be the soundest design.
Simulates natural lens and provides good optical quality.
Capable of retarding opacification from Elschnig pearls.
IOL Lens Design
- AcrySof® Natural IOL
- Piggy back IOL
- Phakic IOL
- Toric IOL
- Accomodative IOL
- Smart IOL�
- Cataract surgery and complications- Norman F Jaffe (2nd Edition)
- Duane’s ophthalmology- CD ROM -2005
- Albert Jakobeic CD ROM (5th Edition)
- AAO Series- Lens And Cataract (2004-2005)
- Ophthalmology Monographs- Intraocular Lenses(1993)