Cataract surgeons were much relieved when they discovered what was causing a complication called intraoperative floppy iris syndrome (IFIS). In 2005, researchers from California, David Chang and John Campbell reported that the drug tamsulosin, an alpha-adrenergic blocking agent, and other alpha blockers can cause this syndrome during a cataract surgery.
A Canadian study of 100,000 men undergoing cataract surgery, found that patients taking the drug tamsulosin had 2.3 times the risk of severe postoperative complications. The postoperative complications ranged from severe iris defects such as pupil deformity, photophobia, and glare to retinal detachment and lost lens fragments.
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Dr. Chang and his team have been conducting researches on alpha-adregenic blockers and IFIS since their discovery of the cause of complication. Their newest research indicated that severe IFIS was more likely with tamsulosin than alfuzosin. So, they recommended cataract patients to try alfuzosin first to avoid this eye syndrome.
What is intraoperative floppy iris syndrome?
Intraoperative floppy iris syndrome is a condition that results in loss of iris (colored part of the eye) muscle tone that occurs during cataract surgery. It is characterized by the following:
• A floppy or flaccid iris that billows when the eye is irrigated during cataract surgery.
• Prolapse of iris at the main point or side port of incision (where the surgeon makes the incision to break down the cloudy lens).
• Progressive pupil constriction that makes it difficult for the surgeon to proceed with the extraction of cataract.
How the cataract surgery is performed
During a cataract surgery, surgeons use an ultrasonic device to break up (emulsify) and then remove the cloudy lens (cataract) from the eye to improve vision. This process is known as phacoemulsification.
Before making the incision, the surgeon anesthetizes the area behind the eyeball. Then they apply pressure on the eyeball to check if there is any bleeding. This pressure also decreases intraocular pressure thus lowering the chances of complications.
The surgeon then makes a tiny circular incision in the membrane that surrounds the cataract. A water stream or irrigation that contains hormone norepinephrine is then done to free the cataract from the cortex of the eye. The ultrasonic device then breaks down the cataract and then it is removed by suction.
What causes intraoperative floppy iris syndrome
To understand what causes IFIS, we should know what adrenergic receptors are and how they function. Adrenergic receptors are specialized proteins attached to the cell membrane that communicate between the cell and the 'outside world'. Hormones, epinephrine and norepinephrine in this case, attach to these receptors (binding sites) and bring about a change in the way the cells in the sympathetic nervous system functions. One of the functions of sympathetic nervous system is the fight-or-flight response that helps you respond to dangerous situation. This response is characterized by body changes such as dilating pupil, mobilizing energy, and diverting blood flow to the skeletal muscles so that you can run or fight. Adrenergic receptors can be alpha or beta depending on their function. Here we are concerned about alpha adrenergic receptors in which the hormone norepinephrine attaches.
Now, alpha adrenergic blocking agents are chemicals that bind to and inhibit adrenergic receptors from functioning, that is, they do the opposite of what alpha adrenergic receptors do.
Alpha blockers relax certain muscles by preventing the hormone norepinephrine from tightening the walls of the arteries and veins, thus keeping small blood vessels to remain open. This is the reason why it is commonly used in hypertension. These drugs are also used in prostate problems to help improve urine flow by relaxing the concerned muscles. Unfortunately, the same drugs, especially tamsulosin and alfuzosin, increase the risk of complications such as IFIS in the cataract surgery. This is how:
1. Alpha blockers relax the smooth dilatory muscles of the iris thus preventing the pupils from dilating. Unfortunately, this is sort of a permanent drug damage.
2. The relaxing of the muscles also causes the iris to billow and prolapse (fall out of place).
3. Muscle relaxing is again responsible for vitreous prolapse. Vitreous is the jelly-like substance that makes up the bulk of the eye and this is the area through which light passes.
Why tamsulosin? That's because this drug is highly selective for the alpha-1 receptor subtype, the blocking of which causes IFIS.
The saving grace is now that ophthalmologists can now anticipate IFIS by finding out the past or current use of alpha blockers by the patients and then decide on alternative surgical strategies.
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