Toric Intraocular Lens
Toric intraocular lens is a type of intraocular lens that is implanted inside the patient eye during cataracts surgery especially phacoemulsification surgery. This lens is specially designed to correct the astigmatism.
Usually patients who have astigmatism and underwent cataract surgery with regular Intraocular lens implant will wear glasses or contact lenses to correct his astigmatism. Instead of that, patient who has astigmatism and was planned for cataract surgery can use toric IOL implantation instead of regular intraocular lens to correct the astigmatism.
Once the Intraocular Lens inside the capsular bag, the Intraocular Lens’s axis should be oriented with the axis of corneal astigmatism. Toric Intraocular Lenses will correct only regular corneal astigmatism that ranges from 1.5D to 3.5D and will not correct irregular corneal astigmatism such as in patients with keratoconus.
There are two FDA approved toric Intraocular Lenses and these are STAAR Intraocular Lens and acrysof IQ Intraocular Lens.
STAAR Toric Intraocular Lens
It is a one piece foldable IOL that is made from Silicon. One piece means that the haptics (IOL arms) and the optic plate are made from one material. Three pieces IOL are built from haptics that attached to the optic plate.
The optical plat is biconvex in shape and the back surface of it is spherical while the front surface of the lens is spherocylinder. The spherical powers of these IOLs can correct from 10.0 D to 28.0 D.
According to cylinder correction powers, these IOLs come in two versions, one that correct astigmatism of 2 D and the other corrects astigmatism of 3.5D. For IOL stabilization inside the capsular bag, there are small holes at the end of each haptic which by time the fibrous tissue will grow around them and stabilize them.
Acrysof IQ Intraocular lens
It is hydrophobic acrylic one piece foldable IOL with biconvex shape but the front and back surface of the lens is aspherical to reduce the spherical aberrations.
Its spherical powers range from 6.0 D to 30.0 D and they come in three versions for astigmatism correction, 1.5D, 2,25D and 3.0 D. The flexible haptics design help to stabilize the IOL inside the capsular bag. Read more about Acrysof IQ Lens.
enVista, the new Toric IOL from Bausch & Lomb
Read more about enVista Lens
Pre-operation Evaluation of Toric Intraocular Lens implantation
In addition for the regular patient evaluation for cataract surgery, astigmatism power and its axis should be determined by keratometer and corneal topography and the axis should be marked in the cornea in upright position before the surgery because when the patient is in supine position, there might be mild eye rotation and in this case the axis will be different.
Complications of Toric IOL implantation
There are complications that can be associated with cataract surgery itself. The main complication of toric intraocular lens implantation is the rotation of the IOL inside the bag which can cause under correction of astigmatism and sometimes, if there is too much rotation from the main axis, the astigmatism power may increase and in this case your eye doctor might take you back to the operation room to repositioning of intraocular lens.
