Coaxial MICS yields strong visual outcomes despite endothelial cell loss

Michal Wilczynski

Phacoemulsification and foldable IOL implantation performed through a 1.8-mm coaxial microincision is effective in treating hard cataracts, a study found.

Cataract grade was associated with a diminished postoperative corneal endothelial cell density but had no significant correlation with corrected distance visual acuity or surgically induced astigmatism, the study authors said.

“In cases with hard nuclei, the surgery is particularly challenging, as the risk of complications is higher,” Michal Wilczynski, MD, PhD, the corresponding author, said in an email interview. “Nevertheless, if the surgery is performed with adequate care, achieving good postoperative visual acuity is possible. [Coaxial] MICS was known to be a very good technique of removing soft and medium-hard cataracts. We found that [coaxial] MICS is also a safe and effective method of treatment of hard cataracts.”

The coaxial MICS (C-MICS) and biaxial MICS (B-MICS) techniques offer incisional stability, rapid wound healing and visual recovery, and minimal surgically induced astigmatism, he said.

However, the B-MICS technique poses some disadvantages, such as instability of the anterior chamber during surgery because of fluid leakage, potential wound trauma resulting from the insertion of a sleeveless phaco tip through a tight incision and a steep learning curve, Dr. Wilczynski said.

“In contrast, it is thought that coaxial MICS, due to its similarity to conventional phacoemulsification, does not share some of the disadvantages of B-MICS,” he said. “Moreover, the surgeon does not need to employ a new technique. Therefore, the learning curve is shorter.”

The study was published in Ophthalmic Surgery, Lasers & Imaging.

Patients and procedures

The prospective study included 85 eyes of 85 patients. The study group comprised 40 eyes of 40 patients with hard cataracts scored 4 or higher on the Lens Opacities Classification System III (LOCS III). Mean patient age was 72.65 years and mean LOCS III score was 4.03.

A comparator group comprised 45 eyes of 45 patients with non-mature soft cataracts scored 2 or lower on the LOCS III. Mean patient age was 71.04 years and mean LOCS III score was 2.33.

Patients underwent comprehensive ophthalmic examinations preoperatively and 1 month postoperatively.

Mean preoperative Snellen distance corrected visual acuity was 0.16 in the study group and 0.62 in the control group. The between-group difference was statistically significant (P < .05).

Mean preoperative endothelial cell density was 2,496.58 cells/mm² in the study group and 2,526.09 cells/mm² in the control group. The difference was statistically insignificant.

Between-group differences in preoperative and postoperative IOP were statistically insignificant.

All patients underwent C-MICS with injection of an Akreos MI60 IOL (Bausch + Lomb) through a 1.8-mm temporal clear corneal microincision.

Average ultrasound power and effective phaco time were appreciably greater in the study group (P < .05).

“The incision was self-sealing and unsutured,” Dr. Wilczynski said. “In my department, we have a very positive experience with the [Akreos IOL] and we have never had any problems with wound-assisted implantation of this lens. Therefore, it is routinely used during our C-MICS procedures.”

No serious postoperative complications were reported. Minor, transient complications in the early postoperative period included Descemet’s membrane folds and corneal edema.

Optical and anatomic outcomes

Study data showed that mean postoperative Snellen distance corrected visual acuity was 0.92 in the study group and 0.97 in the control group. The increase in distance corrected visual acuity was statistically significant in both groups (P < .001). The between-group difference in postop distance corrected visual acuity was statistically insignificant.

Postoperative Snellen equivalent distance corrected visual acuity of 6/6 was achieved in 72.5% of eyes in the study group and 86.7% of eyes in the control group.

Mean postoperative surgically induced astigmatism was 0.48 D in the study group and 0.53 D in the control group; the difference was statistically insignificant.

Postoperative endothelial cell density was 2,220.18 cells/mm² in the study group and 2,449.40 cells/mm² in the control group; the difference was statistically significant (P < .05).

Endothelial cell loss was 11.37% in the study group and 2.87% in the control group; the difference was statistically significant (P < .05).

“During uncomplicated cataract surgery, endothelial cell loss may result from intraoperative mechanical damage caused by ultrasound vibrations, air bubbles, turbulent flow of irrigating solution and floating lens fragments,” Dr. Wilczynski said. “Other known factors which increase corneal endothelial cell loss are high ultrasound power, long phacoemulsification time, high irrigation volume and postoperative intraocular pressure rise, which results from [ophthalmic viscosurgical device] retention in the anterior chamber.”

Endothelial cell loss is also associated with diabetes, pseudoexfoliation syndrome and corneal dystrophies stemming from previous intraocular surgery or ocular trauma, he said. – by Matt Hasson

Reference:

• Wilczynski M, Supady E, Loba P, Synder A, Omulecki W. Results of coaxial phacoemulsification through a 1.8-mm microincision in hard cataracts. Ophthalmic Surg Lasers Imaging. 2011;42(3):125-131.

• Michal Wilczynski, MD, PhD, can be reached at the Department of Ophthalmology, Medical University of Lodz, University Barlicki Hospital No. 1, ul.Kopcinskiego 22, 90-153, Lodz, Poland; email: michalwilczynski@wp.pl.
• Disclosure: Dr. Wilczynski has no relevant financial disclosures.

Coaxial MICS (sub-1.8 mm incision cataract surgery including IOL implantation) is an effective way to remove cataracts while avoiding the astigmatic changes induced by incisions larger than 2 mm. Hard cataracts are a particular problem for surgeons because they require more surgical work and the distortion of the wound might be influencing the refractive astigmatic outcome of the surgery. No previous papers have been published in this respect. The authors have compared one group with hard cataracts to another with immature cataracts in order to ascertain whether differences happen during the postoperative period. They find that the initial postop period is significantly worse in the hard cataract group (related to surgical work and higher energy levels used for the surgery) than in the immature cataracts. However, astigmatic outcomes are equivalent at 1 month. The authors use vector analysis to avoid the bias that might be caused by simple refractive analysis.

The main consequence of this paper is that the surgeons can be comfortable using coaxial MICS in their practices even in hard cataracts, taking advantage of the astigmatic control that this technology offers postoperatively. This issue is important because correction of astigmatism either with corneal incisional surgery or with toric IOLs is becoming standard practice, and standard incisions still induce astigmatic changes. This paper concludes that coaxial MICS offers the advantages that modern cataract surgeons should have for astigmatic control to feel comfortable using astigmatism-correcting technologies, especially toric IOLs.

– Jorge L. Alió, MD, PhD
OSN Europe Edition Editorial Board Member
Disclosure: Dr. Alió is a consultant for Bausch + Lomb, Hanita and Zeiss.