What Are Multifocal Contact Lenses?
Multifocal contact lenses are used to provide clear vision at varying distances for people who have vision problems. Multifocal contact lenses are mainly used for people who have presbyopia. Multifocal contact lenses are made with different lens powers, targeting vision at varying distances from the wearer. Basically, they are contact lenses with multiple prescriptions in one lens. This all-in-one lens benefits people with presbyopia by helping to correct age-related vision problems – when their eyes can no longer focus on objects up close.
Multifocals contact lenses are come in soft and GP materials and are also available as hybrid contact lenses. Multifocal lenses are mostly made of silicone hydrogel material to provide more oxygen to the cornea than the other lenses. Multifocal contact lenses have a smooth and gradual transition between the prescription for reading and seeing things close up, the prescription for normal distance, and viewing things far off in the distance – very much like progressive eyeglasses. Bifocals, on the contrary, have an abrupt difference in the line between the near and normal vision prescription areas of the lens.
Different Types of Multifocal Lenses
There are three types of multifocal lenses:
Concentric Multifocal Lenses
This type of multifocal contact lenses has lens power in the center of the lens that is surrounded by concentric rings of near and distance powers, according to your prescription to see objects which are at a distance. These lenses have concentric circles on lens that allow for a gradual transition from one prescription to the next. Much like a bull’s eye pattern, the rings alternate near and distance corrections.
Typically, at least two concentric power rings are within your pupil area in normal lighting, but this varies as your pupil dilates and constricts due to varying light conditions. Some concentric bifocal contacts have a center-distance design (D) for your dominant eye and a center-near design (N) for your non-dominant eye.
These lenses are either made of soft or GP materials. GP bifocals usually have the distance power in the center (called center-distance).
Aspheric Multifocal Lenses
In an aspheric multifocal contact lens, there is a gradual change in the lens power from far to near without visible lines on the lens surface. To wear an aspheric multifocal contact lens your eyes have to accustom themselves to the visual system of what power should be selected for that moment. Aspheric lenses are made similar to progressive lenses for a blended transition between prescriptions. However, one of the prescriptions will be located in the center and gradually shift as you move outward.
Aspheric multifocal contact lenses also have a curvature in order to sit optimally on the eyeball. But their edges are flattened. The flat curvature changes the optical properties of the lens. The latest manufacturing processes make it possible to produce this special shape. The lenses can be better adapted to the curvature required by the eye. They deflect light rays as required by the wearer and avoid image errors. Therefore, an optimal visual result is achieved.
Segmented Bifocal Lenses
Segmented bifocal lenses are similar to bifocal eyeglasses which are made up of rigid GP material and have two power segments divided by a visible line. The distance correction is on the top while the near one is on the bottom. While wearing segmented bifocal lenses your eyes can freely move behind the lens. These are smaller in diameter than other contact lenses. When you shift your gaze downward the lens stays in place.
All bifocal contact lenses are rigid gas permeable lenses. They resemble bifocal eyeglasses lenses with the near prescription located in the bottom half of the lens and the distance prescription in the top half. The lower area of these lenses is flattened to keep it in place on the eye.
How Do Multifocal Lenses Work?
Simultaneous vision contact lenses provide distance, intermediate, and near correction within the world of the ocular pupil. Therefore, light rays from both distance and near targets are simultaneously imaged on the retina. New and better designs of multifocal contact lenses are continuously appearing to enhance visual performance. The working of the multifocal lens can be divided into two ways:
Simultaneous Vision Designs
In this type of multifocal contact lenses, there are different regions for different lens power to provide the sharpest vision to the user which they can use depending on the object they are viewing. Also, in clinical research, this vision is also known as the “near image” and “distance image”. The target and the power of lenses are also similar to “near” or “distant” images.
The optics of the lens can be described as the portion of the lens as well as the object distance of the image. It’s important to remember that regardless of the target viewing distance, the portions of the lens containing a distance refractive and near refractive power will both contribute to the image that is formed.
These are made of GP material with two portions (the top with the distant lens power and the lower with the near lens power) divided by a visible line. One can view objects by moving their eyes freely behind the lens as the lens will stay in place due to its material. These designs are different from some of the multifocal gas permeable lens designs. These design optics are vertically segmented. It is most likely similar to progressive spectacle lenses.
Many translating GP lens designs have lined or blended lens segments dedicated to distance, intermediate, and near working distances, which can be manipulated independently of one another. This unique power layout makes it easy for contact lens practitioners to prescribe precisely based on a patient’s vision demands. Naturally, this precision makes the lens perfect for those patients who demand their very best vision at a number of working distances.
Advantages of Multifocal Lenses
- Offers a better visual acuity range for magnifying and distant vision.
- It has a less abrupt switch between prescriptions.
- It provides the ability to see objects without extra eyewear.
- People who wear corrective lenses are now not in the need of after using multifocal contact lenses.
- They can easily work on a computer without wearing their glasses.
- These multifocal contact lenses help you to see far-away objects.
Disadvantages of Multifocal Lenses
- It will be difficult to adjust to the lens because of the different viewing experiences.
- It is one of the most expensive lenses because of its design.
- It can cause hazy vision during the beginning.
- Multifocal contact lenses help you to see near and far objects but some still feel difficult to see near objects.
- It makes reading in dim light difficult.
Alternatives To Multifocal Lenses
Monovision is another contact lens alternative for presbyopia particularly if you are having difficulty adapting to multifocal contact lenses. Monovision splits your distance and near vision between your eyes, using your dominant eye for distance vision and your non-dominant eye for near vision.
Typically you will use single vision lenses in each eye however sometimes the dominant eye will use a single vision lens while a multifocal contact lens will be used in the other eye for intermediate and near vision. This is called modified monovision. Your eye doctor will perform a test to determine which type of lens is best suited for each eye and optimal vision.
There are many other alternatives to multifocal lenses:
- Bifocal Contact lenses.
- Surgical correction.
- Monovision Contact lenses.
Depending on the look, the performance of those lenses approaches that of spectacle correction in terms of distinction sensitivity and close to sight, the latter being vital to the current population. Each takes a look at lenses established straightforward to suit supported the manufacturer’s recommendations alone.
Though multifocal contact lenses might not be appropriate for folks whose occupations need precise distance sight and stereopsis. Our results counsel that they’ll be an appropriate difference for a considerable proportion of presbyopes United Nations agency need the convenience, performance, and improved cosmesis of contact lenses.
Difference Between Multifocal And Bifocal Lenses
Multifocal lenses have a gradual shift from the different lens powers while Bifocal lenses are divided into two portions, distant and nearby a visible line in the lens.
Bifocal lenses are divided into two distinct segments for different vision powers, the first for distance vision and the second for near vision. This enables you to clearly switch your focus from near to far as needed, but your vision will not necessarily be clear in between. The term multifocal lenses can refer to any lenses with multiple powers including bifocals, trifocals, or progressive lenses. Non-bifocal multifocal lenses have a range of powers that enable you to constantly adjust your focus to see clearly from up close to far and in between.
Multifocal contact lenses are generally designed in one of two ways, as either simultaneous vision lenses or alternating vision lenses.
Many lenses (CL) manufacture simultaneous-image lenses within which power varies either swimmingly or discontinuously with zonal radius. we have a tendency to gift in vitro measurements of some recent CLs and discuss however power profiles may be approximated in terms of nominal distance corrections, close to additions, and on-eye visual performance. The variation in power across the simultaneous-image lenses produces an increased depth of focus.
The through-focus nature of the image, which influences the “best focus” (distance correction) and therefore the reading addition, can vary with many factors, as well as lens centration, the wearer’s pupil diameter, and ocular aberrations, significantly spherical aberration; visual performance with some styles might show larger sensitivity to those factors.
Multifocal contact lenses compared to standard lenses or monovision result in better uncorrected near vision and a higher proportion of patients who achieve spectacle independence, but greater risk of unwanted visual phenomena. Newer diffractive lenses may be better than refractive lenses in near vision and quality of vision outcomes, with less risk of halos than older diffractive lenses and refractive lenses.
If you want your vision at the sharpest, when you are suffering from different refractive errors then contact your ophthalmologist or optometrist.
Contact Eyemantra Care so that you can make an informed decision about selecting your lens. We have experienced and well-trained ophthalmologists to help you.
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