Visual Field Changes in TECNIS ZCB00 Monofocal vs. TECNIS Symfony Extended Depth of Focus Intraocular Lens Implantation

Overview

Glaucoma is a leading cause of blindness worldwide. Damage to the optic nerve results in vision loss gradually. This vision loss can be detected by using visual field testing, and is a way of monitoring glaucoma progression. As this population ages, cataracts develop, and patients need to undergo cataract surgery to replace the cloudy crystalline lens with an artificial intraocular lens (IOL). The standard of treatment is implantation of a monofocal IOL, but this limits depth of focus and does not allow clear vision at both distance and near without glasses post-operatively. Multifocal and trifocal lenses split light into multiple distinct foci at near, intermediate and far distances without glasses correction. However, these lenses have been shown to reduce contrast sensitivity and impair visual field testing results, and are not recommended in patients with glaucoma. The TECNIS Symfony IOL has recently been approved by Health Canada and offers an extended range of vision with a single elongated focal point to allow patients to see at both distance and near. The lens is advertised to enhance contrast sensitivity, but it is currently unknown whether the TECNIS Symfony IOL impacts visual field testing. We will study the visual field changes in patients undergoing both TECNIS ZCB00 monofocal and TECNIS Symfony extended depth of focus IOL implantation during cataract surgery. The results of this study will impact the advice cataract surgeons give to patients with glaucoma, regarding whether this population of patients would benefit from a standard monofocal IOL implantation or an extended depth of focus TECNIS Symfony IOL implantation.

Primary open angle glaucoma is a leading cause of blindness worldwide, and is the most common form of glaucoma. This condition involves progressive damage to the optic nerve over time and ultimately vision loss that can be detected using standard automated perimetry visual field testing. As this population ages, patients will eventually develop cataracts and require cataract surgery to replace the cloudy crystalline lens with an artificial intraocular lens. The standard of treatment is implantation of a monofocal intraocular lens (IOL), but this limits depth of focus and does not allow clear vision at both distance and near without spectacle correction post-operatively. To provide a refractive component to cataract surgery, multifocal and trifocal lenses were introduced and split light into multiple distinct foci at near, intermediate and far distances without correction. However, splitting of incoming light has the potential to decrease contrast sensitivity and increase photic phenomena. In addition, multifocal IOLs have been shown to reduce mean deviation on automated perimetry compared to monofocal IOLs and are not recommended in patients where visual field reduction may not be tolerated, such as in patients with glaucoma. The TECNIS Symfony IOL has been recently been approved by Health Canada and offers extended range of vision with a single elongated focal point, corrects for chromatic aberration and results in contrast enhancement. It is unknown whether this new IOL impacts visual field testing in glaucoma patients post cataract surgery. The objective of this study is to compare visual field outcomes in patients choosing to undergo cataract surgery with either a TECNIS ZCB00 monofocal vs TECNIS Symfony extended depth of focus intraocular lens. It is hypothesized that patients who undergo implantation of a TECNIS Symfony extended depth of focus intraocular lens will have impaired visual field testing (a decrease in mean deviation on Humphrey 24-2 standard automated perimetry) compared to those undergoing TECNIS ZCB00 monofocal intraocular lens implantation. This will be a prospective cohort study. Patients undergoing either TECNIS ZCB00 monofocal or TECNIS Symfony extended depth of focus ZXR intraocular lens insertion during cataract surgery will be recruited. Patients will not be approached regarding the study until the patient decides which lens will be inserted during surgery. This study has no impact on a patient's choice of intraocular lens. This study will not be assigning a lens as part of the intervention. There will be no randomization of the groups, given that patients will be choosing which lens will be implanted during surgery pre-operatively, as any other patient undergoing cataract surgery would. There will be no blinding of study participants or of the investigators. As per standard pre-operative assessment, patients will have ocular Biometry performed prior to surgery to assess what prism diopter lens to insert intra-operatively. On the day of this appointment, participants will be asked to perform a 24-2 Humphrey standard automated perimetry visual field test with Swedish Interactive Threshold Algorithm (SITA) standard thresholds. In addition, at the 1-month post-operative appointment, participants will be asked to again complete a 24-2 Humphrey visual field, in addition to the standard post-operative examination.