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Are safety concerns regarding MICS lenses and PCO justified?
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MICS technique is further enhanced by new MICS lens implants
 Jeffrey Whitman |
IOLs that can be implanted through sub-2-mm microincisions have rapidly evolved to follow the development of cataract surgery to microincision biaxial and coaxial phacoemulsification. These MICS IOLs, such as the Akreos MI-60 (Bausch + Lomb), are made of hydrophilic acrylic material that is designed to be flexible enough to fold for insertion yet also has excellent material memory, enabling the IOL to return to its original conformation once in the capsular bag. Their lower refractive index helps minimize glare, external and internal reflections, and other dysphotopsias. The material also has clear optics, with negligible vacuoles or glistening, perhaps making them more efficient optically than many non-MICS acrylic IOLs. In addition, insertion through a phaco microincision should aid in decreasing surgically induced astigmatism, which can improve the rate of visual recovery.
Some skeptics have suggested that posterior capsule opacification occurs earlier in the case of MICS hydrophilic acrylic IOL implantation, because the excellent biocompatibility of these IOLs provides a permissive environment for lens epithelial cell growth. The hydrophilic acrylic lens I use, the Akreos MICS, which is the only sub-2-mm IOL currently FDA-approved in the United States, has a 360° continuous posterior square edge designed to minimize PCO. The lens also has a 6-mm optic and comes in three lens diameters for best fit into the capsular bag. A published Nd:YAG rate of 8.8% on eyes implanted with a hydrophilic acrylic IOL with a mean follow-up of 30 months has been reported. This rate is below the national average of Nd:YAG rates, based on data from the Centers for Medicare and Medicaid Services.
In summary, hydrophilic acrylic MICS IOLs are designed to minimize dysphotopsias and glistenings, conditions for which there are no easy solutions. Nd:YAG capsulotomy is a well-proven treatment for PCO with effective results and a good safety profile.
Jeffrey Whitman, MD,is an OSN Cataract Surgery Board Member. Disclosure: Dr. Whitman is a consultant for Alcon, Bausch + Lomb, Inspire and Revision Optics.
References:
- Cleary G, Spalton DJ, Koch DD. Effect of square-edged intraocular lenses on neodymium:YAG laser capsulotomy rates in the United States. J Cataract Refract Surg. 2007;33(11):1899-1906.
- Khandwala MA, Marjanovic B, Kotagiri AK, Teimory, M. Rate of posterior capsule opacification in eyes with the Akreos intraocular lens. J Cataract Refract Surg. 2007;33(8):1409-1413.
MICS technique may achieve close-to-perfect results
 David J. Apple |
The MICS technique, when successfully completed, promises high-quality, clear and precise postoperative vision with minimal astigmatism and aberrations. However, if PCO and postoperative fibrosis occur, the results can be poor. Indeed, it is probably best not to attempt the procedure if the surgeon is not well-trained with small-incision techniques, particularly sound management of the cortex and capsule. Our clinicopathologic studies show that a successful result requires that the surgeon has mastered capsulorrhexis and hydrodissection and, most importantly, is adroit at thorough removal of lens epithelial cells (LECs) from the capsular bag. Less than perfect removal may be acceptable for standard large-incision surgery or even in the case of incisions as small as 2 mm. However, with even smaller incisions, failure to achieve a complete evacuation of LECs may lead to PCO or even fibrosis. Fibrosis is caused by a metaplasia and further proliferation of retained and disrupted LECs.
Most MICS IOLs are thinner and more flexible than conventional IOLs. In the case of such small lenses, the concept of “no space-no cells” leading to no LECs, which is normally helpful in controlling PCO, does not usually apply. Moreover, such lenses are less likely to withstand the distortion caused by postoperative fibrosis and accompanying shrinkage that occurs if retained LECs are left in the capsule. These complications may in turn lead to torsional movements of the bag and even lens decentration.
David J. Apple, MD, is an OSN Cataract Surgery Board Member. Disclosure: Dr. Apple’s research is supported in part by Alcon, Abbott Medical Optics and Bausch + Lomb.