Comparison of Aspheric Toric Intraocular Lenses for Micro-monovision

Cataract is a condition caused by progressive clouding of the natural crystalline lens inside the eye. This leads to impairment of visual performance. This condition represents a huge disease burden and is a leading cause of reversible blindness worldwide. In the UK and the developed world, the incidence of cataract induced blindness continues to increase, secondary to an aging population and increasingly common risk factors such as diabetes. In 1950, Harold Ridley inserted an intraocular lens following cataract extraction at St Thomas' Hospital. This was the first recorded surgery of its kind, and heralded the development of modern cataract surgery, which is comprised of extraction of a cataract by phacoemulsification (ultrasonic micro-fragmentation) followed by insertion of a foldable intraocular lens. Cataract surgery (CS) is the most common elective surgical procedure in the developed world, and the most common in the EU, with 4 million procedures performed in 2016. CS continues to evolve, as do intraocular lenses (IOLs).

Currently, only mono-focal (one point of focus) IOLs are available during cataract surgery in the NHS. These are designed to give excellent vision for one fixed point of focus (either distance, intermediate or near vision), with most patients opting for good distance vision, and requiring glasses for intermediate vision or near vision. Accordingly, these lenses do not treat presbyopia, the loss of the ability focus on near objects, that most people develop in their 50's. In addition, the standard monofocal lens does not treat astigmatism, a common condition characterized by a non-spherically shaped cornea (the clear tissue at the front of the eye) which results in blurred unaided distance and near vision and the need for both reading and distance glasses following surgery.

In this trial patients will be randomly assigned to receive two TECNIS Eyhance Toric lenses or two Alcon Acrysof IQ Toric II lenses (one for each eye). Prior to surgery the 'power' of each patients intraocular lens is chosen. This is similar to choosing the power of lenses in spectacles at an opticians. By choosing the power of one eye to be targeted for distance and the other offset for a small myopic (short-sighted) correction to allow unaided intermediate (computer) and some unaided near vision, the investigators can then investigate the efficacy of these lenses not only to improve vision after cataract surgery but also their ability to treat astigmatism and reduce the dependence on spectacles following NHS CS. As such the investigators hope to offer cost benefits to NHS patients as well as quality of life improvements. In addition to efficacy, quality of life and cost benefits to patients, the investigators will also explore patient acceptability of such "premium" IOLs and look at models to investigate their affordability with the NHS setting.

This study is a clinical trial, designed to compare visual outcomes after cataract surgery with two different intraocular lenses. As previously described, modern day cataract surgery is composed of two main components: removal of the cataract, and insertion of an intraocular lens (IOL). The role of the intraocular lens is to replace the focusing power of the natural crystalline lens inside the eye. It is this lens that becomes a cataract. Removing a cataract alone helps light enter the eye, but does not focus it well. Prior to the invention of intraocular lenses, patients required extremely thick and strong glasses for both distance vision.

Currently only monofocal intraocular lenses are available on the NHS. Different strengths of lens can be chosen to give the patient good distance, intermediate or near vision. That means the ability to focus on objects in the distance, middle distance or near. Most patients opt for good distance vision, enabling them to mobilise easily, watch TV and drive, and require glasses for reading.

As described above, most patients over the age of 50, have some element of presbyopia, which is the inability to focus on near objects, resulting in the need for reading glasses. Inserting extended depth of focus (EDoF IOLs) intraocular lenses during cataract surgery, can help improve their reading vision without reading glasses.

Astigmatism is an abnormality of the cornea, which requires special distance and reading glasses to give clear distance and near vision. Toric IOLs correct astigmatism and reduce or prevent the need for astigmatism correcting glasses after surgery.

The TECNIS Eyhance Toric II IOL is a new IOL which corrects astigmatism and has an enhanced depth of focus through its novel 'enhanced aspheric' design. This will help treat presbyopia. The Alcon Acrysof IQ Toric IOL is an established Toric IOL corrects astigmatism alone.

This trial will investigate the effect of a new Extended depth of focus (enhanced aspheric) toric lens on vision and compare it to a commonly used Toric IOL. The investigators will recruit patients who have bilateral cataracts with astigmatism. These patients will have otherwise healthy eyes. Patients who have been referred to St Thomas' Hospital for assessment for cataracts will be considered for the trial. If they fulfil the criteria for acceptance to the trial, the consulting doctor will discuss this with the patient. If the patient expresses interest, they will be referred to the Research department. The cataract research fellow will review them and consider them for admission to the trial. This review will happen on the day of the original appointment, or the patient will be given an another appointment time and date for further assessment. If a patient would like further information about the study, but cannot speak to the Cataract Research Fellow that same day, they will be asked to fill in a Consent to Contact form, which will allow the research department to contact the patient for consideration for entry to the study.

The investigators will recruit 2 groups of patients, with 70 patients in each group. The investigators will randomly assign them to either the TECNIS Eyhance Toric II group or the Alcon Acrysof IQ Toric IOL group. All patients will cataract surgery on one eye, appointments to review their progress, and then the second cataract operation. The patients in the TECNIS Eyhance group will have TECNIS Eyhance Toric II lenses inserted into both eyes. The patients in the Alcon Acrysof IQ Toric group will have Alcon Acrysof Toric IQ lenses inserted into both eyes. Patients who fulfil the inclusion/exclusion criteria will be fully informed of the investigative nature of the study and consented. Neither the TECNIS Eyhance Toric II IOL or the Alcon Acrysof IQ Toric IOL are used in the NHS, but are used in private practice in the UK

Once patients are consented, they will have a pre-operative assessment which will include a full eye examination (including biomicroscopy and tonometry), refraction (a glasses similar to a visit to an opticians), have their vision tested at near, intermediate and distance with and without glasses. They will also have contrast sensitivity (previously described), pentacam scanning (mapping of the front of the eye) and an intraocular pressure check. The investigators will perform a biometry (measurement of the eye) to calculate the lens power required for surgery. Intraocular lenses are available in different powers, in the same way spectacle lenses are available in different powers.

Cataract surgery will be performed during National Health Service (United Kingdom) cataract lists at St Thomas' Hospital. Surgery will be performed by senior cataract surgeons, and standard protocols will be followed. Patients will be reviewed at 2 weeks, 6 weeks and 6 months after surgery.

The 2 weeks post operative review will be collect the same data as the pre-operative assessment as described above. Patients reviewed at 6 week and 6 months post operation will have all of the above, plus digital imaging (photography), stereoacuity (3d vision) and ScheimpflugTomography (3d scanning) to assess IOL tilt and decentration. The digital photography will be compared with a digital photograph taken on the day of surgery, to assess rotational lens stability. The 6 month digital image will be used to assess posterior capsular opacification and glistenings (problems with the lens or behind the lens). Anonymised digital images may be shared with Prof Chris Hull at City University to help us assess glistening of the IOLs. At pre-operative assessment and 6 week assessment a scan of the macula (macula OCT) will take place. This is a noninvasive test done in the eye department.

Participants in the study at the 6 weeks-, 6-month visits should expect to take around an extra 120 minutes in total for these extra, non-invasive tests to be performed. Patients will be asked to complete questionnaires, namely EQ-5D-3L, Catquest-9SF and Cat-PROM, before surgery- and at 6 week and 6 months post-operatively. At 6 months, the need for, type of and expenditure cost of spectacles required by patients will be recorded and compared between groups. Finally patients will be monitored for adverse events at every appointment after surgery.

Interim data will be reviewed at 20% completion of treatment and 6 month followup (following second eye surgery). The study completion date will be when Patient 140 has completed their 6 month visit (following second eye surgery) plus 14 days for data entry and database lock.

The investigators will be using a strategy called micro-monovision. Most people have a dominant eye, in the same way that they have a dominant hand. In micro-monovision the investigators choose an intraocular lens power that will give the dominant eye good distance vision (emmetropia), and a intraocular lens power that will give the non-dominant eye good intermediate distance vision. The investigators will be using this strategy in both the TECNIS Eyhance Toric II group and the Alcon IQ Toric group.

The investigators are testing the following hypotheses (theories)

1. That the TECNIS Eyhance Toric IOL, when implanted in both eyes, will give better middle distance and near vision, than the Alcon IQ Toric lens, whilst maintaining a similarly good quality of good distance vision. The investigators will also compare contrast sensitivity and stereoacuity (described previously). The investigators will also record complaints of 'flashing lights' or 'halos' in a patients vision, which can be caused by the implantation of the intraocular lens. These are considered to be a rare side effect.
2. That the TECNIS Eyhance Toric II IOL, when implanted in both eyes, will give better middle distance and near vision, than the Alcon Acrysof IQ Toric lens, resulting in improved patient satisfaction scores on the CatPROM and CatQUEST trial.
3. That the TECNIS Eyhance Toric II IOL, when implanted in both eyes, will give better middle distance and near vision, than the Alcon Acrysof IQ Toric lens, thus resulting in reduced costs for the patient, as they will not need to buy reading or intermediate vision glasses.
4. That the TECNIS Eyhance Toric II IOL, when implanted in both eyes, will give better middle distance and near vision, than the Alcon Acrysof IQ Toric lens, has similar stability, and does not rotate.