Intraocular Lenses
(IOLs)
Small, artificial implants for cataract
removal surgeries
What exactly are the intraocular lenses (IOLs)?
An intraocular lens (IOL) is used in cataract surgery, immediately after the phacoemulsification stage, to replace the cloudy – cataractous, natural crystalline lens of the eye (located behind the iris and within the capsular bag).
An intraocular lens (IOL) is in fact a small, artificial disk (usually made of acrylic, silicone, or PMMA) that is implanted (serving as a prosthetic material) into the eye through a special injector. The intraocular lens (IOL) is flexible and foldable during insertion. It can be introduced through a microscopic incision of a few millimeters and remains permanently inside the eye post – operatively, appropriately affecting the refractive power of the eye to restore vision. The most common type of implantable intraocular lenses is the monofocal IOL.
What are the main types of intraocular lenses (IOLs)?
The technology of intraocular lenses (IOLs) has made a tremendous progress. The types of IOLs used in cataract surgery are the following:
Monofocal IOLs: Provide a single focal point for qualitative distance vision (for near vision the patient will need glasses post – operatively, if he/she faces presbyopia)
Monofocal Toric IOLs: Provide a single focal point for qualitative distance vision and correct corneal astigmatism
Multifocal or Trifocal IOLs: Provide multiple focal points for qualitative near, intermediate, and distance vision. They address presbyopia via concentric rings (circles)
Multifocal – Trifocal Toric IOLs: Provide multiple focal points for qualitative near, intermediate, and distance vision. They address presbyopia via concentric rings (circles) and simultaneously correct corneal astigmatism
Extended Depth of Focus (EDoF) IOLs: Premium intraocular lenses that allow for distance vision (e.g. driving), intermediate vision (e.g. reading items on a supermarket shelf), and near vision up to a certain point (usually 40 – 50 cm, e.g. sewing) under good lighting conditions. While multifocal IOLs create multiple focal points, which can be challenging for the human brain to adapt to in a number of candidates, an Extended Depth of Focus (EDoF) lens creates a single elongated focal point to achieve this broad range of focal distances (without issues during night driving, and without reflections or halos)
What is the importance of preoperative biometric examination for selecting an intraocular lens (IOL)?
Biometry is the measurement of various anatomical elements of the eye (e.g. axial length, corneal curvature, anterior chamber depth, etc). Those metrics are crucial for selecting the refractive power of an IOL to be used in cataract surgery, to ensure a successful post – operative outcome. Biometry determines the type and the diopters of the intraocular lens (IOL). Nowadays, there are 3 types of biometry:
Ultrasound biometry (contact)
Optical biometry (non – contact)
OCT biometry (with Optical Coherence Tomography of the anterior segment)
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