Every eye has a lens that sits directly behind the pupil. It is made out of a thick, transparent, viscous fluid, surrounded by an extremely thin equally transparent capsule. The lens is held in proper position by microscopic fibers called lens zonules. Normally, the lens of the eye is crystal clear and sharply focuses the light that comes into the eye. This allows us to see clear and sharp images. In many people, as a result of the aging process -- usually over the age of 60 to 70 -- the lens of the eye becomes cloudy, hazy and sometimes dark yellow or brown in color. This process is called cataract formation. When a cataract develops, images seen by the eye appear cloudy, distorted and less bright, as if they are seen through tinted frosted glass instead of a clear windowpane.
In eyes with pseudoexfoliation, the tiny, flaky particles of this material deposit on the front surface of the cataract (lens) known as the anterior capsule, and on the lens zonules.
When a cataract worsens to the point where the vision is significantly reduced and can’t be corrected adequately with glasses or contact lenses, cataract surgery is an option that can restore the vision. Modern, state of the art cataract surgery is done through a tiny incision (1/8 of an inch) in the eye using a procedure known as phacoemulsification – high frequency ultrasound that dissolves the cataract and vacuums it out of the eye. During phacoemulsification a tiny remnant of the cataract is left behind; a transparent membrane known as the posterior capsule. Since cataract surgery removes the focusing lens of the eye, a new lens must be placed inside the eye where the cataract used to be. This is called an intraocular lens implant or IOL. The IOL is made out of a clear, transparent plastic and is very well tolerated by the eye, often restoring perfect or near perfect vision if the rest of the eye is normal. The IOL sits inside the capsular bag and posterior capsule of the original lens (cataract) of the eye that is left behind during the cataract surgery. The capsular bag and posterior capsule is like a microscopic pocket or envelope that keeps the IOL in perfect position and centered behind the pupil, thereby providing excellent vision.
Cataract surgery has a very high success rate of nearly 98-99%. As a result, over 3 million cataract operations are done in the USA every year. As people live longer this number is expected to increase in years to come.
A pseudoexfoliation eye with a cataract is typically much more difficult to operate on than a routine cataract (see details in paragraphs below). Therefore, one of the most important things about doing cataract surgery in a pseudoexfoliation eye is for the surgeon to be prepared for sudden, unusual circumstances that arise and must be dealt with immediately by performing various intricate, technically demanding surgical maneuvers. The diagnosis of pseudoexfoliation must therefore be made prior to surgery, so that the surgeon is well prepared with non-routine equipment and surgical steps for any unusual difficulties that may occur. If the cataract is not examined with a slit lamp through a DILATED pupil preoperatively, then the surgeon may miss the diagnosis of pseudoexfoliation and will not be prepared for the sudden, unusual difficulties that can occur during surgery. This dramatically increases the risks and complications of the surgery and may result in requiring additional operations and permanent reduction or loss of vision.
The first step of the cataract surgery is to dilate the pupil with several different eye drops in order to allow the phacoemulsification instrument to have easy access to the cataract. In eyes with pseudoexfoliation, the pupil often does not dilate well because the flaky deposits on the pupil and iris damage the dilating muscles of the iris, preventing adequate dilation. Experienced pseudoexfoliation cataract surgeons will often insert “pupil rings” or “iris hooks” into the eye in order to fully dilate the pupil. Attempting phacoemulsification without adequate pupil dilation can result in many sight-threatening complications such as iris and pupil damage, dislocation of the cataract during surgery and vitreous fluid compartment disruption with vitreous loss. These complications can cause cloudy vision, glare, inflammation, retinal detachments, glaucoma (or worsening of pseudoexfoliation glaucoma) and other serious complications that may require additional surgeries to attempt to repair the problems.
The second step of cataract surgery, capsulorhexis, requires making a round incision into the front part (anterior capsule) of the cataract. In eyes with pseudoexfoliation this incision has to be performed extremely carefully and gently since any excess tugging, pulling or pushing of the anterior lens capsule can cause an imperfect capsulorhexis incision, making the rest of the surgery more difficult, hazardous and complicated. Experienced pseudoexfoliation cataract surgeons have experience with delicately creating an appropriately sized and shaped capsulorhexis incision in order to avoid problems with the remainder of the surgery.
The third step of cataract surgery is hydrodissection. This requires injecting a specially formulated saline solution (BSS) into the cataract in order to separate the bulk of the cataract from the posterior capsule and capsular bag. In eyes with pseudoexfoliation, the lens capsule is more fragile and prone to tears or ruptures caused by excessive pressure from injection of the BSS. Experienced pseudoexfoliation cataract surgeons can carefully gauge how much BSS injection pressure to exert to prevent a tear or rupture of the capsule and its subsequent complications.
The fourth major step of cataract surgery is removal of the bulk of the cataract using the phacoemulsification probe that is inserted into the eye through the tiny incision. In eyes with pseudoexfoliation, this part of the surgery has the highest risk of problems and serious complications. Pseudoexfoliation flakes damage and weaken the microscopic lens zonules that hold the cataract in position during the surgery. Excessive pressure, pulling or pushing of the lens zonules during the phacoemulsification step of cataract surgery may result in the cataract falling into the back of the eye on the retina or optic nerve. This serious problem significantly increases the risk of multiple complications occurring after the surgery, and almost always requires a second operation to retrieve the fallen, dislocated cataract. Experienced pseudoexfoliation cataract surgeons can often modify their phacoemulsification surgical techniques and maneuvers on the fly to avoid this serious complication.
The fifth step of cataract surgery is to place the IOL inside the cataract’s residual capsular bag, directly in front of the posterior capsule and centered behind the pupil. This requires very delicate surgical maneuvers inside the eye, which experienced pseudoexfoliation cataract surgeons have mastered. Any miss-steps in this part of the cataract surgery can cause the intraocular lens implant to rip the lens capsule and fall into the back of the eye on the retina and optic nerve. This can cause numerous serious postoperative complications and problems, and most likely will require an additional operation to remove the dislocated IOL and replace it with a different one that will no longer be positioned in an ideal location inside the eye.
It should be noted that pseudoexfoliation eyes can have IOL dislocations even years after successful cataract surgery because of progressive weakening of the lens zonules. If this occurs, then surgery is usually needed to retrieve the dislocated IOL and either suture it into the eye or replace it with another IOL positioned in another part of the eye.
Many pseudoexfoliation eyes that undergo cataract surgery also have pseudoexfoliation glaucoma preoperatively. Any complication from the cataract surgery carries a high risk of aggravating and worsening the glaucoma (see Glaucoma & Pseudoexfoliation section).
Additionally, timing of the cataract surgery in a pseudoexfoliation eye is critical. The surgery should not be done on a “mild” cataract since it’s not wise to take on significant risk with minimal gain in an eye that has only mild blurring caused by the cataract. However, it is also not advisable to delay surgery in a pseudoexfoliation eye till the cataract is very advanced, since the worse the cataract gets the more difficult it is to remove without complications. An experienced phacoemulsification cataract surgeon can determine the opportune time to perform the cataract surgery in order to minimize the risks and reduce surgical complexity, thereby improving the prognosis and results.
Clearly, cataract surgery in an eye with pseudoexfoliation is significantly more hazardous and risky than in an eye with a routine cataract. Although pseudoexfoliation complications can occur in even the most experienced surgeon’s hands, in general, the more pseudoexfoliation cases a surgeon has done the less chance there will be complications, and if they occur, the more likely the surgeon will be able to deal with them and reduce their severity and threat to vision.
Robert Cykiert, M.D.
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