An intraocular lens (IOL) replaces the original crystalline lens when a cataract is removed, and provides the light focusing function originally undertaken by the crystalline lens. When a cataractous or cloudy crystalline lens is removed during cataract surgery, the outer layer of the lens is left in place to support the IOL. If you imagine that a cataract is like a peanut M and M but that the candy coating is transparent, like plastic wrap, then during cataract surgery a hole is cut in the front surface of the candy coating of the M and M and the insides are scooped out. This leaves the lens capsule in place. The new lens is placed where the old lens was, inside of the lens capsule through the opening that was made in the front of the lens capsule (to remove the cataract). Intraocular lenses can be made of several different materials and come in a wide variety of designs.
There are two ways that an intraocular lens can dislocate. One is when there is a defect or tear in the capsular bag holding the lens and the lens slips out of the capsular bag. (That is shown in the accompanying image) Another way the IOL can dislocate is if it stays in the capsular bag and the entire capsular bag destabilizes and looses its support and shifts. The first way is the most common. In-the-bag dislocation of an intraocular lens is less common and a little more difficult to address surgically. Posterior chamber intraocular lenses (IOLs) are exquisitely engineered to provide excellent vision when implanted into a stable capsule following extracapsular cataract extraction. If the lens capsule or the supporting lens zonules fail, and the IOL dislocates, vision usually deteriorates. Unfortunately, just as cars are not designed to be easily fixed after crashing, IOLs are not designed to be easily repositioned after dislocating.
If the intraocular lens is only slightly decentered, a change in prescription glasses can compensate for the problem. Interestingly, if the intraocular lens is totally out of position and settled in the vitreous of the eye, sometimes it can be left in the eye and a seconday lens can be placed without removing the lens. Both of these options avoid the risk of removing or manipulating the dislocated lens. The risk of surgery (like an eye surgery) include infection, bleeding, retinal detachment and corneal damage.
Probably the most common procedure done for a dislocated intraocular lens is a lens exchange. The offending IOL is removed from the eye and a new lens is placed in the eye. If there is some capsule left in the eye that will support a larger IOL then a posterior chamber lens can be placed in the eye. If their is not capsular support adequate for a posterior chamber lens, then an anterior chamber IOL like the one in this photo can always be placed in front of the iris. In addition, there are a few useful techniques where a posterior chamber IOL can be placed into an eye without capsular support. A posterior chamber IOL can be clipped to the iris, sutured to the iris, sutured to the sclera or the haptics of the IOL can be tunnelled into the sclera. All of these options are reasonable depending on the state of the cornea, iris, and capsule.
The Akreos AO60 posterior chamber intraocular lens has holes in the four haptics which can be used to suture fixate the lens. The procedure is populare because it allows for four point fixation of the lens with an 8-0 gortex suture. The four point fixation reduces the chance of lens tilt which can happen with two point fixation. Also, the 8-0 gortex suture is very well tolerated.
This video was featured at the American Academy of Ophthlamology website in 2019 and shows fixation of a posterior chamber intraocular lens.
If the dislocated IOL is in good shape and free of surrounding capsular debris, it can be captured in the pupil and sutured to the iris. This technique is demonstrated in one of the video’s below. This technique only works well for dislocated IOLs that have haptics. There are other types of IOLs, like the crystalens IOL, that do not have haptics and cannot be sutured to the iris. The sutures holding the haptics of the IOL to the iris in the accompanying photograph are blue and can be seen where the arrows are pointing. The optic of the IOL is perfectly centered and not visible.
This patient had cataract surgery and some of the fragments from the surgery dropped into the vitreous. They are removed and then the intra-ocular lens, which is not stable, is sutured to the iris for stability.
When there is inadequate capsular support to allow simple repositioning of a dislocated IOL, sutures can be used to secure the IOL in the visual axis. The IOL can be sutured to the iris or the sclera. In cases of an in-the-bag dislocated IOL or a plate-haptic dislocated IOL, a transscleral 9-0 polypropylene fixation technique is preferable. The knots used to tie the transscleral sutures securing the IOL present a vexing problem. If they are covered with only conjunctiva and Tenon capsule, they usually erode through the covering. Once exposed, the knots irritate the eye and pose an increased risk of endophthalmitis. The technique presented in this article and the accompanying video obviates the need to make a scleral flap or tunnel by using the needle on the 9-0 polypropylene suture to bury the suture in the sclera. The knot can then be rotated into the eye through a preplaced 23-gauge sclerotomy.