General information and terminology

The lens of the eye is analogous to the camera lens. The retina is the “film;” the iris-pupillary complex the “aperture.” The cavity behind the lens that fills the posterior 2/3 of the eye is called the vitreous or vitreous gel. You will hear more about this gel later.

A cataract is a clouding of the natural lens of the eye. As a rule, we recommend waiting until the vision is degraded to 20/40 or worse. If visually disabling, however, the surgery can be done at an earlier stage.

An artificial lens commonly referred to as an implant or intraocular lens (IOL) replaces the cataract. An eye with an artificial lens is called pseudophakic. Most commonly, posterior chamber IOLs are placed. These are behind the pupil, into the “capsular bag” or the “ciliary sulcus.”

Of all procedures covered by Medicare, cataract surgery ranks 6th in terms of intensity. Each surgeon has multiple techniques in their toolbox depending upon the cataract type and any factors to the eye that can make the surgery more difficult (small pupil, pseudo-exfoliation, prior eye surgery, shallow anterior chamber and so forth).

SURGICAL COMPLICATIONS

The rate of complications is commonly cited as 2%. Because the eye is accessible to direct examination, complications are readily manifested. While most can be handled by the operating surgeon, retained lens fragments, endophthalmitis and dislocated implants require intervention by a subspecialist.

A complication is unplanned occurrence which can affect the outcome of the procedure. Prevention and treatment of complications is the priority for all cataract surgeons. There may be delayed recovery time, a return to the OR, or a referral to an outside specialist. Most surgical mishaps—if properly managed– can still achieve a reasonable outcome.

During the surgery

When the cataract is removed, if the posterior capsule or zonular complex is breached penetration into the vitreous cavity often occurs. The vitreous is no longer separated from the anterior portion of the eye and will move towards the wound. The term vitreous loss is used since some of this jelly-like material must be removed (and is lost) from the anterior portion of the eye. The eye replaces the vitreous with clear fluid. Most serious eye complications have vitreous loss as the common pathway.

A dropped nucleus refers to loss of lens material into the vitreal cavity. The management of these problems can be touch and go as the surgeon is working under considerable stress. If improperly handled, a medical malpractice claim can result.

Zonular weakness or stripping of the zonules with or without with vitreous loss is another undesirable intraocular event. It can be managed with capsular hooks or capsular tension rings. An untreated break in the zonules can lead to decentered placement of the IOL. This is called a dislocated IOL.

INTRAOCULAR LENSES COMPLICATIONS

IOL’s come in different powers called diopters. Great care must be taken to ensure that the chosen power Is the one that is implanted. Human error can occur anywhere down the chain of command from incorrect entries on the surgical reservation form to an inexperienced nurse handing off the wrong lens. An incorrect power is very hard to defend against. This is different from a “refractive surprise” where the implant power was off due to the vicissitudes of eye anatomy.

Intraocular lenses are available in monofocal or multifocal versions. The monofocal lens has a focal point for either distance or near. The multifocal has two more focal points. Multifocal lenses require more precision in attaining the desired post-operative refractive target to optimize performance and minimize side effects. (dysphotopsia).

There are two main styles of IOL’s: one-piece and three-piece. The one-piece lens is designed to be placed “within the bag” and three-piece lens is to be placed the ciliary sulcus. Improper placement of a one-piece lens is a standard of care deviation that often leads to a poor outcome or need for a lens exchange surgery.