Side structures, which hold the IOL in place within the capsular bag

 

LOOP HAPTIC DESIGN

 

Current IOLs can exist as 3-piece or 1-piece (single-piece), where the haptic insertions differ.

 

3-PIECE IOLS

• Create a ‘C’ shape, thus are known as C-loop IOLs

• Insert into the optic edge through two holes.

• This IOL enables the round capsular bag shape to be retained

• The loops occur at an angle of around 5-10º, preventing pigment dispersion

      via iris disruption 

• Used less, but are useful for when posterior capsule rupture occurs and are                                 required for implanting to the sulcus

• C-loops require large corneal incisions

• The loops produced are large and unmanageable, hence cannot be injected during surgery

 

1-PIECE

• Single-piece IOLs have a slightly shorter structure compared to that of a 3-piece IOL

• They have C-loops made for both capsular and ciliary sulcus insertion

• Modified C-loop with either 2, 3, 4 or 6 haptics in order to counteract posterior                               pressure and capsular bag contraction without dislocation of the IOL.

 

 

 

PLATE HAPTIC DESIGN

 

• Used for toric IOLs due to their capability of clockwise and anticlockwise rotation

• These lenses, via capsular bag contraction, are inserted into the vitreous chamber

• Squeezing action is made easier due to the silicone material that they are made of

 

 

 

HAPTIC MATERIALS 

 

• In order for a haptic to effectively carry out its function, its design needs to be of an increased strength and flexibility

 

• Originally, polypropylene met these requirements and was used as a material to construct haptics.

  • However, later it was found to degrade inside the eye and was no longer used. 

 

• PMMA (polymethyl methacrylate) is a material used in developing countries due to its low cost, however is known to be fragile unless compression moulding is implemented.

  • There have been cases where the haptics become bent during implantation along with decentring

 

• A chemical compound known as PVDF has shown to have good retentive memory, flexibility and adhesion to the capsule compared to PMMA.

  • However, despite this materials strength and stability, once attached, removal is virtually impossible

 

• Another common material used for haptics is Polyamide, a flexible material which is tolerant to degradation in the eye when positioned behind the iris