Introduction
Microinvasive surgical methods determine the development direction of today’s ophthalmology. Examples of these trends are MIVS (microincision vitrectomy surgery), MIGS (microinvasive glaucoma surgery) and MICS (microincision cataract surgery).
The goal of MICS is to treat cataract using 2.0 or smaller corneal incision with the purpose of reducing surgical invasiveness, improving at the same time surgical outcomes [
1]. MICS is divided into two methods: coaxial MICS (C-MICS) and biaxial MICS (B-MICS). C-MICS gives the possibility to implant the IOL through 1.8 mm incision. The method which reduces this size is B-MICS, which allows 1.4 mm cataract surgery and IOL implantation. B-MICS resulted from the interplay of several factors including microcorneal incisions, bimanuality, improved use of fluids, rapidly progressing instrumentation, and adequate use of low-energy ultrasound phacoemulsificators [
2], including development of new sleeveless tip [
3,
4]. Advantages for this procedure are lower surgically induced astigmatism (SIA), less postoperative higher-order corneal aberrations (HOA) and lower endothelial cell loss [
5‐
7]. Furthermore, it seems reasonable to conclude that smaller incision size has lower impact on corneal biomechanics, shortens recovery time and reduces number of endophthalmitis, although until now there is no clear evidence to support these hypotheses.
The Incise monofocal intraocular lens (IOL, Bausch & Lomb) is the first innovative IOL that can be implanted without a convention tunnel preparation but through 1.4 mm paracentesis. In the available literature, only three promising study results with short follow-up period up to 6 months were published on clinical outcomes of this lens [
5‐
7]. Above-mentioned studies were performed with biaxial technique with IOL implantation from 1.4 mm [
5] and 1.6 mm [
6] clear cornea incision and one with coaxial microincision (C-MICS), where the lens was implanted through 1.8 mm incision [
7].
This is why we decided to assess clinical outcomes after B-MICS with implantation of these lenses in longer follow-up period of 12 months.
Discussion
Microincision cataract surgery develops rapidly. New techniques like B-MICS and C-MICS procedures significantly lowered mean phacoemulsification time, mean phacoemulsification power and surgically induced astigmatism when compared with standard coaxial phacoemulsification [
12]. In B-MICS technique, irrigation and aspiration are performed separately. Through two opposite 1.2–1.4 mm paracentesis, the phacotip without sleeve and the irrigation tip are inserted into the anterior chamber. C-MICS technique requires tunnel and two additional paracentesis and the only difference from traditional coaxial phaco is the use of 21-gauge phacotip. During B-MICS procedure, the tip without sleeve is used and it is possible to damage the cornea around the wound because of possible thermal burn [
13]. It may cause “leaky wound” and in consequences opens the way to bacterial infiltration from conjunctival sac. In the present work, one incident of corneal leakage at first day after the cataract surgery was noticed. It was treated with contact lens, and in day 4 the wound was stable without need for additional treatment. Other authors report anterior chamber instability during the surgery [
5]. In our series of patients, where the Stellaris Phaco System with forced infusion was used, we did not observe above-mentioned problem. During one operation, there was need for wound enlargement and the lens was implanted through 2.0 mm incision. Even though in our study, no sign of intraoperative or postoperative inflammation could be seen, which indicates that this technique seems to be safe.
It is widely known that the smaller the incision the lower SIA [
14,
15]. In comparison with coaxial surgery biaxial surgery shows significantly less SIA [
14,
15]. B-MICS procedure allows sub-1.8 mm incisions, which effectively decrease the induction or changes in corneal SIA during cataract surgery in comparison with C-MICS [
14]. Alio et al. [
16] suspect that “2.0 mm is the limit around which no optical changes are induced by cataract surgery in the human cornea.” In present study SIA was equal 0.29 ± 0.16 D and was very similar to the Jimenez et al. result: 0.31 ± 0.22 D,
p > 0.05 [
8]. There was a statistically significant difference between our and Sonnleithner et al. [
5] and Toygar et al. [
7] results, where SIA was equal 0.45 ± 0.29 and 0.45 ± 0.28, respectively (
p < 0.05). Probable reasons behind these differences might be the wound stretching during IOL implantation [
5] and the incision size, which was equal 1.8 mm in Toygar et al. [
7] study. Cavallini et al. [
17] demonstrated that more posterior wound retraction is observed in 1.8-mm incisions compared to that in 1.4-mm incision (53 vs. 47%). It seems that the limit around which no optical changes are induced by cataract surgery is lower and might be sub-1.8 mm.
In our study, CDVA before surgery improved significantly from 0.58 ± 0.57 to −0.05 ± 0.06 in third month and was stable during 12-month follow-up. These results were significantly better compared with other study results on Incise IOL (
p < 0.05) [
5‐
7]. Jiménez et al. [
6] reported improvement of mean DCVA from 0.57 ± 0.15 to 0.16 ± 0.13 3 months postoperatively, Sonnleithner et al. [
5] from 0.4 ± 0.27 to 0.05 ± 0.07 4 weeks after surgery, Toygar et al. [
7] from 0.52 ± 0.42 to 0.01 ± 0.02 logMAR 6 months postoperatively.
In present study, 1 year after the surgery mild PCO was observed especially in the peripheral part of the capsule, but the center was clear in all eyes. In consequences, no one patient needed YAG-capsulotomy 1 year after surgery. It is reasonable to conclude that lack of significant PCO was connected with design of the IOL: continuous 360 square-edge profile, which prevents PCO formation. According to study results of Nanavaty et al. [
18] who evaluated 3 different IOLs: 2 aspheric microincision hydrophilic IOLs (Acri.Smart 36A and Akreos MI-60) and conventional single piece hydrophobic acrylic spheric IOL (AcrySof SN60AT; Alcon Laboratories), there is a trend in hydrophilic IOLs toward progression over the 2-year follow-up. At 2 years, the mean PCO score was lower than 11% for the conventional AcrySof IOL and 23% for the Akreos MI-60 IOL. Longer observation time is necessary to assess frequency of significant PCO formation.
Incise IOL has high level of predictability and is comparable with other IOLs [
19]. Toygar et al. [
7] reported 6 month after surgery 94% of eyes were within 1.0 D from calculated refraction in comparison with our 90% 1 year after surgery.
Other advantage of microincision is low number of higher-order aberration (HOA). It is commonly known that HOA might be caused of decreased visual acuity and contrast sensitivity [
5]. In study, results by Sonnleithner et al. [
5] outcome in terms of Incise IOL HOA were very satisfying and comparable to other aspheric IOLs (Akreos MI60, Tecnis ZCB00, CT Asphina). In our study, the results of contrast sensitivity for distance were within normal limits of healthy people in the same range of age indicated very good performance of this type of IOL. Our results agree with those in other study [
6] on Incise IOL. Additionally, the follow-up period was 6 months longer in our study.
The patients were highly satisfied with the quality of performed procedures and implanted lenses due to the fact that they received mostly very good, uncorrected visual acuity for distance. None of patients complained about glare. In our experiences with other IOL implanted using B-MICS procedure [
20,
21], glare effect was also not observed.
In summary, the results of presented study suggest that B-MICS with Incise lens implantation is a procedure which provides for the patient very good visual function as well as high patient’s satisfaction. So, we would recommend the B-MICS and this type of IOLs for the cataract surgeons and patients. It seems reasonable to expect that Incise lens might be a good platform for introduction for multifocal IOL.