Cataract surgery is the most common eye surgery in the world. If the patient with cataract uses spectacles and both patient and surgeon find it beneficial, it is possible to compensate for the spectacles during surgery and thereby obtain a spectacle-free distance vision or spectacle-free near vision. Becoming spectacle free increases quality of life substantially and is one of the primary wishes in cataract patients. Socioeconomically, spectacle free life is beneficial as it reduces fall tendency in the elderly population. Multifocal lenses warrant the possibility of obtaining a spectacle free vision at near, intermediate and distance. It is also possible to obtain spectacle free distance and near vision or distance and intermediate vision by using traditional artificial monofocal lenses but making one eye spectacle free for distance and the other eye spectacle free for near or intermediate vision. Currently, it is not know which procedure is most beneficial for cataract patients.

In a recent PhD, the investigators developed a method, Aniseikonia Tolerance Range (ATR), that can assess how much refractive change a patient can endure without impairing stereopsis. The results demonstrated large variation in the tolerance of image difference. This method can be a future tool to assess whether a patient can tolerate the refraction that is considered most beneficial to the patient. The knowledge is important as it can help avoid improper lens choice in cataract surgery and thereby avoid stereopsis problems.

Background This randomized clinical trial aims to improve visual outcomes in cataract surgery by examining which intraocular lenses (IOL)/operation methods that provide highest patient satisfaction, visual function and spectacle free vision. Furthermore, the tolerance of surgical induced refractive difference (anisometropia) will be examined and a screening method to assess how much anisometropia a patient can endure will be validated. The investigators will examine if the tolerance of anisometropia > 3 diopters is better than previously described and examine if ATR can predict which patients will experience binocular problems if exposed to surgical induced aniseikonia.These results will lead to higher patient satisfaction, better visual outcomes with elimination of patients with mediocre refractive results and visual problems due to anisometropia.

In addition the investigators will examine whether ATR is reproducible by examining the variation in the multiple measurements and in a prospective study the investigators will investigate the inter and intra person reproducibility of ATR.

100 refractive patients with healthy eyes except myopia > 3 diopters and < 6 diopters, who will have a Small Incision Lenticule Extraction (SMILE) surgery will have all investigations done. The patients will have a bilateral SMILE with a interval of seven weeks and will in between the two procedures have a surgically introduced anisometropia that will provide further knowledge on anisometropia and ATR.

Inclusion Criteria:

• Bilateral cataract
• Axial length: 20-27 mm
• ACD > 2.3 mm
• Pupil size: ≥ 5.0 mm in dilatation
• Pupil siza: ≥ 2.5 mm in photo topic condition
• Stereoacuity ≤ 480 seconds of arch

Exclusion Criteria:

• Former intraocular surgery
• Other eye disease (amblyopia, strabismus, corneal pathology, glaucoma, uveitis, age related maculopathy
• Other retinal diseases
• Risk of weak zonules due to PEX or former trauma
• Astigmatism ≥ 1.0 diopter
• Diabetes
• Axial length difference between the two eyes > 0.3 mm
• Dementia
• Lack of cooperation kooperation
• Stereoacuity > 480 seconds of arc
• Complicated cataract surgery or postoperative complications (intraocular infection, retinal detachment, macular edema
• Business driving
• Night driving