Dr. Masket firmly believes the post-RK eye "is such a moving target, a multifocal lens should not be considered—it will fail unless we achieve absolute or near emmetropia." He noted that the refraction can change from morning until evening and there may be progressive hyperopic shift over time.
Barbara Bowers, MD, in private practice, Innovative Ophthalmology, Paducah, Ky., disagrees—she'll bring these patients in at several different times throughout a day "and if the vision is fluctuating a little bit, I'll consider a multifocal. If they're fluctuating drastically between the morning and afternoon readings, I'll tell them point-blank a multifocal lens will make them miserable." Dr. Masket uses four or five devices to find the flattest Ks, and those are the readings he'll use for IOL calculation.
Astigmatism is an essential component to evaluate in these eyes, said Barry Schechter, MD, in practice, Florida Eye Microsurgical Institute, Boynton Beach, Fla. "We've had some very nice results with toric IOLs in RK patients who have varying amounts of regular astigmatism," he said. "You want to look for wound gaping. If the wounds have healed nice and tight, you're more likely to get a very stable postop refraction after time, but if you see some gaping, you've got the potential for refractive surprises."
If there's "very irregular astigmatism," Dr. Schechter advises against a toric—"you just have to go with a plain monofocal aspheric lens. I've been surprised with the results obtained and with the range of vision possible due to the spherical equivalent."
Dr. Masket avoids toric lenses in some post-RK patients "for fear they may someday need a corneal transplant" and because it's rare to have regular astigmatism in these eyes.
In general, he advises adding "about a half diopter" of measured IOL power for a patient with four incisions, between 1-1.5 D for those with eight incisions, and 2 D for those with 12 or more incisions. While intraoperative aberrometry may be very useful in eyes having prior laser vision correction, it is less accurate in the post-RK eye, as corneal curvature changes during cataract surgery in these eyes, he added.
The VERION™ Image Guided System: Precise Surgical Planning and Procedures
Joining other advanced technologies from Alcon, the VERION™ Image Guided System is designed to offer improved precision, consistency and control in cataract refractive surgery.
The VERION™ Image Guided System Can help:
Minimize data transcription errors
Improve clinical efficiency
Increase toric and multifocal IOL confidence
Ensure surgical consistency
Optimize visual outcomes
Intraoperative floppy iris syndrome associated with tamsulosin
Tamsulosin, an α1-adrenergic blocking agent, is prescribed for symptoms of benign prostatic hypertrophy. In 2005 over 1.6 million prescription items of tamsulosin were dispensed in England. Intraoperative floppy iris syndrome was first described in the medical literature in April 2005, and there have been 16 subsequent related peer-reviewed publications. There is, however, no mention of the association in the current edition of the British National Formulary. Intraoperative floppy iris syndrome occurs in approximately 2% of all cataract-surgery patients and is characterized by billowing and prolapse of the iris through the corneal incisions and progressive pupillary constriction. This leads to a more complex surgery and a higher rate of complications. Many eye units now advise patients to discontinue tamsulosin for 2 weeks before cataract surgery and to start taking it again immediately after surgery, though the syndrome can occur in patients who stopped therapy 1 year before surgery. The condition is associated with all the α1-adrenergic blocking agents but is much more commonly seen with tamsulosin, which is highly selective for the α1A receptor. These particular receptors are present in bladder-neck smooth muscle and in the iris dilator muscle. Blockage of this latter muscle allows unopposed action of the parasympathetically innervated iris constrictor muscle and loss of iris tone, resulting in the clinical syndrome. Intraoperative strategies for reducing the risks during surgery have been described and include the use of iris hooks and intracameral phenylephrine.
We would like to raise awareness about this condition among primary care physicians and to advise that the use of α1-adrenergic blocking agents should be documented on referrals for cataract surgery. Such patients are at higher risk of problems both from cataract surgery and from the urologic effects of the temporary cessation of treatment.
The VERION™ Image Guided System: Precise Surgical Planning and Procedures
Joining other advanced technologies from Alcon, the VERION™ Image Guided System is designed to offer improved precision, consistency and control in cataract refractive surgery.
