IOLs can be described by the material the IOL is made of. One group is called ICLs or intraocular collamer lenses. Collamer is a particular material used for making a particular type of IOL inserted like an intraocular permanent contact lens to correct blurred vision. However most IOLs are made of silicon or acrylic. All IOL materials are biocompatible, ie they do not incite immune rejection of the IOL by the eye. All are inert, that is they do not degrade with time and last as best is known for your entire life in your eye.
IOLs can be described by their use. Phakic IOLs are placed into the eye in addition to the eye's natural crystalline lens, which is not removed. Pseudophakic IOLs are placed after removal of the eye's natural crystalline lens for vision correction or cataract removal reasons.
IOLs can also be described by where in the eye they are put.
Anterior chamber IOLs (AC IOLs) are placed between the cornea, the clear front window of the eye, and the coloured part of the eye, the iris. Posterior chamber IOLs (PC IOLs), or sulcus based IOLs, are placed behind the iris, but in front of the crystalline lens, unless the crystalline lens has been removed. Then the PC IOL is usually placed within the capsular bag component of the crystalline lens that is usually left behind to secure the IOL after modern cataract surgery.
Finally IOLs can be described by the way they bend light. Monofocal IOLs focus light from one image location only.Objects in the real world can be considered to be located in front of a person either far away, at an intermediate distance (like a computer monitor) or near (like a book). A monofocal lens will allow vision in an eye without am accomodating crystalline lens (one that changes shape to focus in from distance to near) at just one of these three locations. Patients these IOLs will usually require spectacles or contacts for other distances.