Visual Outcomes and Rotational Stability of the Acrysof IQ Vivity Toric Extended Vision Intraocular Lens
Visual Outcomes and Rotational Stability of the Acrysof IQ Vivity Toric Extended Vision Intraocular Lens
The main goal of this study is to evaluate real-world visual outcomes, rotational stability, and patient reported visual disturbances with a non-diffractive extended vision presbyopia and astigmatism correcting intraocular lens in patients with significant corneal astigmatism undergoing bilateral cataract surgery. This is important to ensure optimal results for patients who wish to have intraocular lenses that correct presbyopia and astigmatism, thus giving them a greater independence from spectacles and a better quality of life.
It is estimated that cataracts are the cause of 33% of visual impairment and 51% of total blindness worldwide. Indeed, they are the most important cause of total blindness and preventable blindness in the world. To reduce the burden of this disease, many advances have been made in the field of cataract surgery and have resulted in better visual outcomes. With the development of different types of intraocular lenses over the years, it is now possible to not only treat cataracts, but also tackle presbyopia and astigmatism to increase patients' independence from spectacles and thus improving quality of life. Indeed, the desire for independence from corrective lenses is an important motivation for many patients, which explains the increasingly common use of intraocular lenses correcting for presbyopia.
For most uncomplicated cataract surgeries today in Quebec, Canada, monofocal lens are implanted and their cost is covered by the government. Generally, this lens allows patients to be emmetropic, which translates to good distance vision. However, these patients will need reading glasses for intermediate and near vision. A good proportion of patients are unsatisfied with being dependent on corrective lenses, especially if they did not have any before surgery. There is a correction technique for presbyopia called "monovision", which involves making the patient's dominant eye emmetropic and making the other eye more myopic. This way, the patient can use the myopic eye for intermediate and near vision. Intermediate vision is useful for computer work, for example, while near vision is useful for reading. "Monovision" requires good tolerance of anisometropia by the patient and may interfere with stereoacuity, which may limit its use.
Multifocal intraocular lenses were first implanted in 1986, but took several years to become more commonly adopted. The terms "bifocal" or "trifocal" refer to the number of distinct foci in the lens, allowing the patient to see at different distances. The simultaneous perception of these multiple focal points can be initially disturbing for the patient and may require several months of postoperative neuroadaptation. There are two types of multifocal lenses: refractive and diffractive lenses. Refractive lenses have concentric rings centrifugally increasing in dioptric power on their anterior surface. Diffractive lenses, on the other hand, have diffractive rings on their posterior portion. Meta-analyses have shown that multifocal lenses cause visual disturbances, such as halos and glare, that are more bothersome and frequent than in "monovision". However, multifocal lenses show better rates of independence from spectacles than "monovision". Refractive multifocal lenses, compared to diffractive lenses, tend to produce more glare, halos and higher-order aberrations. However, refractive lenses tend to produce better uncorrected distance visual acuity, while diffractive lenses tend to perform better for near vision.
Finally, extended depth of focus (EDOF) lenses are a newer technology that will be discussed in this study. They have an extended continuous focal point as opposed to the fixed focal points of multifocal lenses, which allows for less superimposition of near and far images compared to multifocal lenses. Theoretical interferometry studies also suggest that EDOF lenses produce better images in between intermediate and near vision. A few comparative studies have shown that EDOF lenses show equal or poorer near visual acuity than diffractive lenses, but have equal or better results for intermediate visual acuity. There are also other newer types of intraocular lenses that, due to their novelty, lack enough data at this time. These include accommodative lenses, postoperative non-invasively adjustable lenses and electronic lenses.
Astigmatism is a refractive error caused by an irregularity in the cornea and/or the crystalline lens that prevents the eye from focusing light evenly on the retina. It causes blurred vision at all distances. It is estimated that almost two-thirds of patients undergoing cataract surgery have preoperative corneal astigmatism between 0.25 and 1.25 diopters. 22% of these patients have astigmatism of 1.50 diopters or more. Toric intraocular lens implantation, first introduced in 1992, is the procedure of choice to correct significant corneal astigmatism (1.00 diopter or greater). For optimal correction of astigmatism with the toric lens, precise alignment of the actual lens axis with the calculated preoperative lens axis of placement is required. This is influenced by several factors, a major one being the rotational stability of the lens. Maximum rotational stability has been observed with hydrophobic acrylic lenses. A prospective study with AcrySof Toric lenses showed significant postoperative rotation of more than 10 degrees in only 1.68% of eyes. In fact, the Acrysof IQ Vivity Toric Extended Vision Intraocular Lens is made with the same AcrySof material, which has shown excellent postoperative rotational stability.
To our knowledge, no study to this day has evaluated the refractive visual outcomes of the Acrysof IQ Vivity Toric Extended Vision Intraocular Lens for the correction of presbyopia and corneal astigmatism. This is believed to be the first study of the Acrysof IQ Vivity Toric Extended Vision Intraocular Lens in Canada. Studying the impact of the Acrysof IQ Vivity Toric Extended Vision Intraocular Lens will provide real-world data on visual acuities after bilateral cataract surgery, intraocular lens rotational stability and subjective assessment of postoperative visual disturbances. This is important to ensure optimal results for patients who wish to have intraocular lenses that correct presbyopia and astigmatism, thus giving them a greater independence from spectacles and a better quality of life.
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