In the growing field of refractive cataract surgery, it is evident that the trend for microincisional procedures is escalating. Microincisional cataract surgery (MICS) is defined as a procedure performed through a sub-2 mm incision, in either a bi-axial (B-MICS) or coaxial (C-MICS) fashion.

Because a MICS incision is smaller than the incision created by the conventional coaxial technique, one might expect improved outcomes, resulting in improved visual acuity. Previously published studies have established that the MICS technique is truly astigmatically neutral, making it ideal for refractive lens exchange; the technique is also associated with a decreased likelihood of postoperative wound leakage when compared with a larger incision procedure, thereby also reducing the risk of endophthalmitis.

B-MICS and C-MICS

Theoretically, separating irrigation and aspiration (as in B-MICS) can provide several advantages. B-MICS improves manoeuvrability and decreases the risk of fluid misdirection syndrome, although B-MICS also carries risks surrounding wound leakage and inadequate infusion volume. Additionally, the use of sleeveless instruments can raise concerns regarding both protection of the wound architecture and thermal damage.

That is why, nowadays, most surgeons prefer the coaxial surgical technique. My personal preference is a C-MICS procedure performed completely through an unenlarged 1.8 mm incision with the Stellaris system (Bausch & Lomb).

To evacuate the lens material through the smaller bore needle used in this technique, it is necessary to fragment the lens into particles of smaller diameter than is required by the standard diameter ultrasound (US) needle. Theoretically, with the larger diameter phaco needle, one could expect that, to emulsify the lens nucleus, a lower amount of US energy would be necessary.

Comparing C-MICS with SICS

Although there have previously been a number of studies assessing the outcomes of MICS, no studies have, to the best of my knowledge, compared the postoperative outcomes of 1.8 mm C-MICS with the outcomes of 2.8 mm SICS (small incision cataract surgery) when performed with the latest generation of phaco machines.

I conducted a study to assess if the differences in both the incision size and the US needle diameter — when using the same system and the same settings — influence either the utilization of the US energy and irrigating fluid or the clinical outcomes of cataract surgery.

Table 1: Patient characteristics.

Patients with similar preoperative characteristics (Table 1) were selected to undergo either 1.8 mm C-MICS or 2.8 mm SICS surgery with the clear corneal incision technique. There were no statistically significant differences between treatment groups in terms of either baseline best corrected visual acuity (BCVA) or mean grade of lens opacities (LOCS III).

Both groups underwent phacoemulsification using the same surgical settings:

• US phase: max linear US power 30%, 80 PPS, 50% Duty Cycle, dual linear foot pedal control, IV pole height 100 cm, vacuum 400 mmHg;
• I/A phase: vacuum 600 mmHg, IV pole height 100 cm
• Viscoelastic removal: vacuum 300 mmHg, IV pole height 100 cm.