An Intraocular lens (IOL) is an artificial aid surgically implanted in the living eye to restore the sharpness of vision, frequently after removal of a cataract. A cataract is simply known as It is simply known as Opacification of the crystalline lens. In this topic, we are going to describe details about the history of Intraocular lenses, Types of IOL, Materials, and the manufacturing process.
Table of Contents
History of IOL
- Casaamata – (1795)- attempted an Intraocular implant
- Harold Ridley (1949) — first successful human intraocular lens implant
- During World War II, noticed intraocular foreign bodies of acrylic fragments from aeroplane 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
Pseudophakia is the condition where the Intraocular lens is placed after cataract sugery where as aphakia is the condition of No Intraocular lenses implanted in the eye.
Eyes having an Intraocular lens implanted are optically similar to the phakic condition (having natural crystalline lens).
Compared to the aphakic patient with high plus power lens spectacle correction, the pseudophakic patient has
- Enlarged visual field,
- Less magnification,
- Better stereopsis,
- Rapid visual rehabilitation
Types of intraocular lens (IOL)
Here are the intraocular lens types
- Anterior chamber IOL,
- Iris-fixated IOLs,
- Posterior chamber IOLs,
- Sulcus-fixated IOLs.
Ideal implant material
Properties
- High optical quality
- A high index of refraction
- Lightweight
- Durability
- Ease of manufacture
- Lack of inflammatory reaction
- Lack of antigenicity
- Lack of carcinogenicity
- Ease of sterilization
OPTIC Materials of Intraocular Lens (IOL)
PMMA (polymethyl methacrylate)
- Can be used to create a single vision or 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
The drawback of PMMA IOL
- PMMA is not totally inert
- Hard, rigid material
- Monomer – toxic to the eye
- Nd: YAG laser has the potential to damage PMMA optic.
- Hydrophobic – corneal endothelial cells adhere to their surface.
- Larger incision required
New Materials
Avoiding problems associated with rigid lenses – use softer polymeric materials for lenses.
- Silicone
- Hydrogels
- Foldable Acrylics
Foldable IOL implant pros and cons
Pros
Cellular response
- Less than PMMA lenses.
Optical quality
- Silicone IOL no finishing or polishing is required.
- Have transmissions of >90% in the 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.
Cons
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
Broadly divided into
- One-piece with PMMA haptic or soft biomaterials
Multi-piece consisting of an optic supported by one or more loops (haptics).
- Polymide
- Prolene
- Mersilene
Quality Control of IOL
- 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.
Sterilization For PMMA: Ethylene oxide most commonly uses, Alternative method sterilization using sodium hydroxide. And for acrylic IOL Autoclave is done.
Design characteristics, optic size
- 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 the round optic of 5.5-6.0mm are currently favoured 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- favoured by most phaco surgeons.
- Potential for optical aberration from lens edges.
Shape of IOL
The biconvex lens seems to be the soundest design.
Advantages:
– Simulates natural lens and provides good optical quality.
– Capable of retarding opacification from Elschnig pearls.
IOL Lens Design
- AcrySof® Natural IOL
- Piggyback IOL
- Phakic IOL
Multifocal IOL design
- Toric IOL
- Accommodation IOL
- Smart IOL
Intraocular Lens Production in Nepal
How intraocular lenses are made?
Here is the detailed video related to the intraocular lens manufacturing process of Fred Hollows Laboratory, Kathmandu, Nepal
Intraocular lens manufacturers in Nepal
The Fred Hollows Intraocular Lens Laboratory (FH IOL LAB), Tilganga Institute of Ophthalmology manufactures high-quality low-cost Intra Ocular Lenses of both categories Rigid IOL from PMMA and Foldable IOL.
Products
IOL Manufactured by FH IOL laboratory (Tilganga institute of ophthalmology) Nepal are as follows:
Foldable IOL:
“Flex” Sterile Foldable Acrylic Intraocular lens
- Material: Poly-HEMA Acrylic
- Refractive index=1.461
- Design: Biconvex Optic ‘C’ loop
“Tetra” Sterile Foldable Acrylic Intraocular lens
Tecsoft “Micro” Sterile Foldable Acrylic Intraocular lens
Tecsoft ” Slick ” Sterile Foldable Acrylic Intraocular lens
PMMA and Other Products of FH IOL Laboratory:
- Kelmann Type AC “PMMA” IOLS
- Modified C PMMA IOLS
- Sterile PMMA capsular tension ring
- Hydro-Glide Mini
- Hydro-Glide
- TEC-JECT Injection System
- Hydro-Shooter
How to buy Fred Hollows Intraocular Lens
If you want to purchase Intraocular Lens manufactured by FH IOL, Tilganga Institute of Ophthalmology, you can contact on following contact details:
The Fred Hollows Intraocular lens laboratory
Tilganga Institute of Ophthalmology
Bagmati Bridge, Gaushala
GPO Box 561, Kathmandu, Nepal
Telephone: +977 1 4493775
Fax: +977 1 4474937
Email: [email protected]
References:
- 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)
