Comparative study of visual results obtained with two Trifocal lens models in cataract surgery

Whether refractive surgery of clear lens or cataract surgery, when the implanted Intraocular Lens (IOL) is monofocal it usually provides excellent vision for a single focus [2]. To avoid the inconvenience of needing glasses after surgery, so-called Multifocal Intraocular Lenses (MIOL) were designed to divide the incoming rays of light into the eye in different foci. These MIOL can present a refractive or diffractive optics design [3]. Diffractive MIOL are characterized by optical platforms with a multitude of concentric rings with a specifi c separation and height which results in steps that favor and cause the diffraction of the wave front, which allows to focus at different distances [4]. Abstract

Several clinical studies confi rm the signifi cant visual improvement of bifocal IOL for near vision compared to obtained with monofocal lenses and without signifi cant affectation of uncorrected distant vision [3,5,6]. The disadvantage of bifocal LIOMs is that by having one focal point for near distance and another one for far distance, they offer a good vision only in these two distances and not in an intermediate vision thus affecting tasks such as the use of computers or musical scores among others [7][8][9][10][11]. Bifocal [11][12][13].
Among the current trifocal MIOL, FineVision model (PhysIOL, Liège, Belgium) due to its particular diffractive design 12 is widely used in our environment. Using a stepped optical topography [14], offers an improvement in intermediate vision between 60 and 80 cm without detriment to near or far vision [13,15].
Even with the most advanced designs, after implantation of MIOL, visual alterations can occur, such as a decrease in contrast sensitivity, glare, blurred vision or nocturnal halos [6,[16][17][18]. In addition, it is necessary to obtain very precise results, avoiding as much as possible any refractive deviation, that is to avoid the need of postoperative glasses, in order to achieve optimal functioning of MIOL and thus reduce the likelihood of adverse postoperative visual phenomena [17,18].
In 2018, a new trifocal MIOL was introduced with a novel design that, according to the manufacturer, could improve the visual quality that is obtained with the trifocal lenses. This is the Acriva Trinova MIOL, designed by sinusoidal functions that produces signifi cantly softer lens surface profi les than the diffraction pattern superimposed with sharp edges of the rest of the trifocal lenses. The Acriva Trinova profi le seems to provide better contrast sensitivity and visual dynamics at all distances with a signifi cant reduction in the appearance of postoperative adverse visual effects (A). The objective of this prospective study, carried out in a single center was to evaluate and compare the visual results, contrast sensitivity and patient satisfaction obtained with FineVision and Acriva Trinova trifocal. The study was conducted in accordance with the principles of the Declaration of Helsinki and all patients signed a written informed consent before beginning the study.

Material and methods
The study was approved by the local ethics committee.
We included patients, aged between 50 and 79 years, with no ocular pathology other than cataract and with normal visual acuity. Exclusion criteria included amblyopia, axial length greater than 25 mm, previous ocular surgery, including corneal or refractive surgery, keratoconus, endothelial alteration, chronic or recurrent uveitis, acute internal or external infectious ocular pathology, glaucoma, diabetic retinopathy, intraocular pressure higher than 24 mmHg, pseudoexfoliation, pathological miosis, alterations of the macula or optic nerve, active infl ammation, alteration of the cognitive level that could affect the measurement of visual acuity, interval of more than three months between the date of surgery of the fi rst and second eye and not reaching corrected visual acuity for far (CDVA, Corrected Distance Visual Acuity) postoperatively equal to 20/20 or higher. Patients were informed of possible need for postoperative optical correction, possible loss of contrast in scotopic conditions and optimization of ambient light to optimize postoperative visual performance.

Clinical protocol
Before surgery, all patients underwent a general ophthalmological examination that included the measurement of mono and binocular Visual Acuity (VA) in mesopic conditions (luminances between 0.25-3 cd/m 2 ), Uncorrected Distance Visual Acuity (UDVA,) and best Corrected Distance Visual Acuity (CDVA), without pupillary dilatation and having verifi ed the absence of postoperative circumstances that could limit CDVA. As optotypes those from EDTRS (Early Treatment Diabetic Retinopathy Study) were used. Photopic and mesopic pupilometry, optical biometry (Lenstar 9000 Haag Streit, AG. Koenig, Switzerland), subjective and objective refraction, biomicroscopy, Goldmann applanation tonometry were performed and corneal topography (Sirius, CSO, Italy).
The power of IOL and the prediction of refraction were based on data measured with Lenstar 9000 (Haag Streit, AG. Koenig, Switzerland) biometer and were calculated using Haigis formula. The IOL power closest to the postoperative emmetropic prediction was selected. Each MIOL model was assigned to each patient based on the outcome of the preoperative interview. Acriva Trinova was assigned to patients with preferred visual activity for intermediate vision and to the rest, FineVision.
In the postoperative period patients were examined at 24 hours, at one month and at 3 months. At the last visit, in addition to the biomicroscopic evaluation with slit lamp and tonometer, the absence of postoperative circumstances that could limit the  rise to a unique diffractive pattern [12], with an asymmetric distribution of light between the three resulting foci; for an IOL of 20 D and with a pupil diameter of 3 mm, the distribution of light and energy for far, near and intermediate vision is 42%, 29% and 15% respectively. Approximately 14% of the light energy is lost because it is reached with high diffraction orders, compared with 18% that is lost with an IOL with typical bifocal refractive design [19]. As the pupil diameter increases, the fi ne-tuned optics of FineVision increase the percentage of light directed at far vision.

Acriva trinova model
The newly introduced Acriva Trinova (VSY Biotechnology, The Nederlands) lens (2018) is a one-piece MIOL, with a plate haptic, aspheric and achromatic, diffractive, trifocal, hydrophobic surface design. The maximum diameter is 11.00 mm and that of its optics is 6.00 mm. Available in powers from 0.00 to +32.00 D in steps of 0.

Statistic analysis
To study the possible differences in visual acuity and contrast sensitivity obtained with both lenses. The quantitative variables were described by the mean, standard deviation and range.
To analyze the results we used the statistical program SPSS.
The results with normal parametric tests measured according to the signifi cance (p> 0.05) of the shapiro-wilk formula for that variable were analyzed by measuring the means and the standard deviation. To calculate the p value, we compared both means with a Student's T-test for independent samples.

Results
A total of 40 eyes of 20 patients with an age range between 48 and 68 years were evaluated in our study. Each of the two groups was made up of 20 eyes in which the same MIOL model was implanted bilaterally. In both groups the average age was 59.60 ± 7.32 (50/68).

Visual results
In postoperative refraction the mean postoperative spherical equivalent was different between both groups. In FineVision group -0.05D ± 0.24 (-0.88 / +0.51) and in Acriva Trinova it was 0.2D ± 0.6 (-0.50 / + 1.50) (p = 0.02).    The self-assessment questionnaires were carried out on uncorrected patients. In regard to halos and glare, the degree of satisfaction was approximately equal in both groups. From 20% to 30% did not perceived halos or glare, between 20% and 40% complained from mild to moderate diffi culties. And 20% to 30% had high diffi culty. In no group very high or unacceptable diffi culty were appreciated (Figures 2,3).   In order to evaluate far vision without glasses, 80% of both groups referred having no diffi culty whatsoever (Figures 2,3).
Finally, in terms of the degree of general satisfaction, with Finevision no patient was totally satisfi ed, as there were 80% that referred some degree of dissatisfaction. In one case the degree of dissatisfaction was maximum ( Figure 2). For Acriva Trinova 60% was fully satisfi ed while 40% oscillated between varying degrees of dissatisfaction ( Figure 3).

Defocus curve
Defocus curve results, performed with the best correction for far, showed a higher tolerance to hypermetropic refraction with Acriva Trinova. In emetropized patients, visual performance in terms of visual acuity for distance was similar in both MIOLs. In intermediate vision AcrivaTrinova had a slightly superior performance to FineVision. For near distance FineVision showed the best performance in the defocus curve ( Figure 4).
In our cases, a large majority of patients at three months of surgery had achieved a degree of complete visual adaptation with both trifocal lenses as refl ected in the satisfaction tests ( Figures 2 and 3 Figure 4). It is desirable and future studies are expected to provide new defocus curves with Acriva Trinova.
Regarding contrast sensitivity, both lenses were within the range of normality considered for normal population [25], at all spatial frequencies. There were no signifi cant differences in contrast sensitivity obtained with both MIOLs. It seems that at least in regard contrast sensitivity, the unique sinusoidal design that according to the manufacturer softens the optic of Acriva Trinova, is not more effi cient than the design of the FineVision.