Does size matter?
The techniques and materials employed for cataract surgery have improved significantly over recent years, resulting in enhanced functional surgical outcomes, smaller incision sizes and reduced incidences of astigmatism and endophthalmitis. Consequently, cataract surgery has become the most frequently performed surgery in Germany, with around 600,000 conducted each year.
The plethora of options now available to today's cataract surgeon, particularly when considering the number of intraocular lenses (IOLs) available and variations in incision size, forces us to raise certain questions. For example, is a smaller incision a better incision? Are there benefits of making a sub 1.0 mm incision? If so, what are they? Does it make sense to compromise IOL material and design in order to achieve small incision surgery?
In the end, having attended the meetings, read the evidence, viewed the live surgery demonstrations, it comes down to personal choice and what a cataract surgeon believes is the best option for their patient.
Previous studies have found bimanual phacoemulsification, using a one-piece IOL implanted through a 1.8 mm paracentesis, to be associated with a lower incidence of corneal astigmatism. Specifically, one report found induced astigmatism attributable to this technique to be 0.32 ± 0.18 D, in comparison to 0.55 ± 0.12 D seen in the conventional phaco group with a standard clear corneal incision of 2.75 mm.
So which size do we choose?
A prospective, non-randomized clinical trial was conducted in 42 patients (28 female, 14 male), aged 72 ± 15.8 years, who were scheduled for standard cataract surgery. Preoperative visual acuity was 0.38 ± 0.18, whilst preoperative intraocular pressure (IOP) was recorded at 14.8 ± 2.12 mmHg. Cataract surgery was performed, making a clear corneal incision under topical anaesthesia and then implanting the AR40e IOL in all patients using the Unfolder Emerald through an incision of 2.0, 2.2, 2.4 or 2.6 mm. The same surgeon performed all surgeries.
Table 1 shows the observations made with the varying incision sizes.
We found that it was possible to implant a 6.0 mm three-piece IOL without complications through an incision of more than 2.2 mm.
Taking these results into account as well as those reported by others, I feel that microincision cataract surgery using the bimanual phaco technique is associated with a significantly lower incidence of surgically-induced astigmatism, in comparison with conventional phaco. Hence, it offers a viable alternative to routine phaco, even when implanting a 6.0 mm three-piece IOL.
Gangolf Sauder works at the University Eye Hospital Mannheim, Germany and in the faculty for clinical medicine of the Ruprecht Karls University Heidelberg, Germany. He may be contacted by email: gangolf.sauder@augen.ma.uni-heidelberg.de
