Advanced monofocal lenses provides high vision acuity at only one, fixed distance without use of glasses, but range of good visual acuity is larger than with standard monofocal lens. Normally, advanced monofocal lenses are delivering good far and improved intermediate vision acuity, while for near tasks glasses will be needed.
key Monofocal IOL features
Quality of vision with monofocal lens depends on method to elongate fixed focus range, material type and quality, optics asphericity type and visible light filter.
Focus range extension techniques: Advanced monofocal lenses most commonly use sophisticated higher-order optical aberration techniques to expand the focus range, however diffraction rings are rarely used, although the latter method creates a question about classification of such lenses as a monofocal type. Usually aberration techniques increase the depth of focus and decrease the contrast sensitivity, so the correct balance of material quality and focus elongation method is the key to optimal image quality with this type of lens.
Lens materials: might be either hydrophilic or hydrophobic. Both materials are good, but has basic differences.
Hydrophilic lenses might be injected via smaller incision, but have more tendency for secondary cataract.
Hyprophobic materials have less secondary cataract probability, but generally need slightly larger incision.
However, both lenses types are injected via small and safe incision of less than 2.4mm.
Material quality: normally is described in terms of chromatic aberration and represented via so called ABBE number. The higher ABBE number is, the smaller amount of chromatic aberration lens produces and thus creates better image quality.
Optics type: lens type might have positive spherical aberrations, zero shperical aberrations and negative spherical aberration.
Positive spherical aberration of the lens reduces image quality in dim light conditions.
Zero spherical aberration of the lens provides better image quality.
Negative spherical aberration of the lens provides maximum image quality.
Zero and Negative type of lenses are called "aspherical", however particular asphericity type may influence image quality in different way, based on patient cornea aberrations or anatomical eye specific.
Light filters: any intraocular lens has UV (ultra violet) light filter built in.
Some IOLs have visible light filters. Different light filters has different intensity and color, but generally they are yellow and that type of lenses might be not suitable for peoples, who need maximum amount of light available during night-time or precise color reproduction.
Vision quality with advanced monofocal lens may vary in dim light conditions, depending on particular IOL optics technology, while at bright light such as sunny day all lenses will perform in a similar way.