Contact lenses are used for those with low vision when there is:
- High refractive error (otherwise, a thick eyeglass prescription),
- therapeutic reasons: such as sensitivity to light and glare, and nystagmus,
- concerns about appearance: to create a more normal look for increased self-esteem, and
- a need for either magnification or field enhancement.
1.) Using contact lenses for high refractive error
How contact lenses are beneficial, compare to spectacle lenses:
- wider field of view,
- wider field of fixation, because contacts move with the eye,
- fewer oblique aberrations,
- increased magnification for myopes (those who are nearsighted), and
- contacts can help with eye discomfort relief when using low vision devices, which can be held close to the eye to increase the usable field of view.
While distance visual acuity may not be substantially improved by correcting vision with contact lenses, especially for those with central vision loss, contacts do have the potential for increasing the vision in the peripheral areas of the retina. These other areas of the retina may be enhanced with a sharper image.
Contact lenses work best for those low vision patients with high myopia, such as those who have pathological myopia. That is because eyeglasses for those with high myopic correction , minifiy the visual field. In other words, the thickness of the eyeglass lenses makes the world appear smaller. Contact lenses, which rest up against the eye, do not create this high level of minification . (Minification: the opposite of magnification.) In some cases, the use of the very thick eyeglasses may contribute to decreased visual acuity.
The caveat is those nearsighted individuals with near focusing problems or those that do a lot of close work, may fair better with eyeglass correction.
2. Therapeutic uses of contact lenses for those with low vision and eye disease
- Tinted lenses reduce photosensitivity, glare, and
- reduce eye movements (nystagmus).
Therapeutic Tinted Contact Lenses
Photosensitivity can be reduced or eliminated especially for those with albinism, cone dystrophies, aniridia (those that lack an iris), and achromotopsia.
A small study reported that patients with retinal dystrophies benefited from a red-tinted contact lenses for the reduction of glare and an increase in contrast sensitivity. (CS is the ability to discriminate objects in an environment.) (Ref: : Red Tinted Contact Lenses )
For example: A child born with achromotopsia(Congenital disease resulting in a severe lack of color discrimination) lacks the ability to see color, is light sensitive, and has poor visual acuity. These children benefited from a red/brown filtered lens which had the result of a slight increase in visual acuity and more comfort, even indoors.
For more information, here is an excellent article at Achromatopsia.info
Albinism and Therapeutic Contact Lenses
Those with oculocutaneous albinism may benefit by using contact lenses three ways:
- Tinted or opaque design lenses helps with glare and sensitivity,
- Contact lenses are available in high prescriptions. (Reference to the above section on high refractive errors.)
- Contact lenses can also reduce the disruption of vision from the nystagmus, because the contact moves with the eye.
The most common type of specialty contacts prescribed for those with oculocutaneous albinism is a lens with an iris printed on and a clear pupillary center . This lens design cuts down glare entering their very lightly pigmented eye. Case studies have shown that this contact lens with a printed-on iris can decrease light sensitivity. This type of lens is referred to as a prosthetic contact lens.
This printed-on iris also serves to give a more normal look to their eyes.
For nystagmus, contact lenses are the preferred type of correction. Some studies have shown that contact lenses can reduce the frequency and amplitude of nystagmus. This is controversial and may be attributed to correction of the high refractive error. In some patients, rigid lenses are more effective than soft lenses.
Contact Lenses to Reduce the Risk for Macular Degeneration and Cataracts
It is not news that eye care professionals recommend tinted eyeglasses for their older patients to reduce UV exposure in an effort to decrease central retinal damage (macular degeneration) and cataract formation. There are clear soft contact lenses that incorporate UV protection into the lens material.
Commercially available lenses with UV protection:
All ACUVUE® Brand Contact Lenses have Class 1 or Class 2 UV–blocking
Biotrue One Day (Bausch + Lomb)
ClearSight 1 day and Avaira(Class 1) (Coopervision)
Each one of these manufacturer’s are careful to point out that there is no scientific data to prove that UVA/UVB contact lens protection will prevent macular degeneration or cataracts, and that wearing sunglasses outdoors is advised.
|FDA Class 1 absorber. Recommended for high exposure environments such as mountains or beaches. The lenses in this classification must absorb more than:||90% of UVA (316-380 nm wavelengths) and99% of UVB (280 – 315 nm)|
|FDA Class 2 absorber. Recommended for general purposes. These lenses must absorb more than:||50% of UVA and95% of UVB|
Contact Lenses that Adjust to Different Light Levels for Light Sensitivity
Transitions® eyeglass lenses are the photosensitive plastic eyeglass lenses that change color to a darker ‘sunglass’ tint when exposed to UV light outdoors, and lighten up when entering a space without UV light. This technology has now been incorporated into Acuvue Oasys with Transitions® (Johnson & Johnson Vision Care) contact lenses. Like the eyeglass lenses, these contact lenses adapt to changes in UV light intensity, filter blue light and provide UV protection.
They are also a useful option for computer and digital device users, because the lenses adjust during use of technology that may be throwing off UV and high energy blue light. The long term effects of chronic blue light generating technology on the health of our eyes is not yet known.
Acuvue Oasys with Transitions® contact lenses meet the FDA’s Class I standard by blocking 99.9 percent of UVB and 99 percent of UVA. Additionally, these lenses filter up to 15% of light in the blue light range indoors and 55% outdoors. It is thought that this high energy blue light that has the potential , with long term exposure, to cause damage to eye tissues.
It is a good option for those with eye disease looking to reduce light sensitivity. Keep in mind, while this is an easy option for mitigating some UV exposure, sunglasses should still be worn outdoors.
Contact Lenses that Deliver Medications
In development , but not yet available, are contacts that can be infused with medications that are delivered gradually while worn for a period of days or weeks. No more eyedrops. It releases the burden and inaccuracy of daily eye drop instillation.
The medication is in a thin film that coats the outer rim of the contact lens and therefore, does not interfere with vision in the central area of the lens. The lenses were originally studied using a nighttime glaucoma medication called latanoprost.
This delivery system of medication could have implications for other eye diseases like macular degeneration, diabetic retinopathy, allergy management, and post-surgical treatments.
Contact Lenses that Monitor Health
Recently approved here in the US is the Triggerfish® CLS (contact lens sensor) (Sensimed AG, Lausanne, Switzerland.) This ‘smart’ contact lens is designed to detect eye pressure changes from the front surface of the eye over a 24 hour period. It is designed to detect relative changes in eye pressure to help predict progression of damage due to glaucoma and determine affectivity of glaucoma treatments.
Interestingly, this small 14.1 mm contact lens has two gauges, a microprocessor and an antenna. The eye pressure changes are relayed by the antenna to a portable recorder carried by the patient.
To read more click here: Sensimed’s Triggerfish
Contact Lenses that Monitor Body Fluids
InWith Corporation along with contact lens manufacturer Bausch + Lomb have created a prototype of a soft contact lens with microelectronics embedded in it to keep tabs on body chemistry, like blood sugar levels or to monitor other electronic body parts. It will derive its energy from the natural blinking cycle of the eye and will send alerts and notifications to a smartphone.
See photos and video on InWith Corp. Facebook page
3. How Contact Lenses Enhance Appearance and Self-esteem
Often the visually impaired require thick , heavy eyeglasses that make their eyes look really big or really small behind the frames. Those with thick eyeglass prescriptions may feel more self confident without a pair of coke-bottles sitting on their nose. While their vision may still be poor, even with the contacts, they may feel less different and less burdened by their disability.
Contact lenses, although they may not improve vision any better than the glasses, can offer comfort and the freedom to participate in activities without the annoyance of an unusually thick eyeglass prescription.
Those who suffer with light and glare sensitivity will find relief wearing dark tinted sunglasses both indoors and out. Wearing sunglasses indoors is conspicuous and may draw attention and questions. Those who would like to avoid unwanted attention will find tinted contact lenses comforting indoors (and wearing sunglasses over the contact lenses outdoors), without attracting unwanted questions and comments.
The option to wear contact lenses can make a difference, especially for the young visually disabled to feel more normal and socially accepted by not standing out as different.
4. How Contact Lenses are Used for Magnification and Field Enhancement
Telescopic contact lenses
This discussion is not about the head mounted or hand-held type of telescopes. The two telescopic systems described here are contact lens plus eyeglasses systems. These are usually calculated and set-up by an optometrists/low vision specialists.
The first system designed for magnification combines a high minus contact lens worn with a magnifying eyeglass lens. This creates a ‘telescope’ lenses arrangement that can give up to 2X magnification. This is a Galilean-style telescope for the optical geeks out there. This contact lens/eyeglass system is best tolerated by younger persons with low vision. It can create some disorientation on head movement vs visual field movement.
How to increase the visual field for those with restricted visual fields; telescopic system:
Reverse contact/spectacle lenses telescopes to increase visual field for those who have severely narrow visual fields, like those with retinitis pigmentosa. In order to increase the visual field, the contact lens is the magnifier(plus lens) and the spectacle glasses (minus lenses) minifies the field so more can be seen.
These solutions utilizing telescopic systems to increase distance acuity or increase distance visual field can be disruptive to vision and will take time to adapt to. As it is one eye that is set up for the telescopic vision and consequently disrupts binocular vision.
At this time, these are the only contact lens-style magnification or field enhancing techniques.
But…there is new technology on the horizon:
Not yet available , researchers in California are developing a contact lens that can zoom in to magnify and out to normal by using blinks.
Another international group is developing a magnifying contact lens that has incorporated fitted mirror surfaces into a telescope a millimeter thick that fits within the contact lens. This contact lens is combined with a set of polarized eyeglass lenses.
Both of these proposed technologies will benefit those who need magnification, especially those with central vision loss, like macular degeneration.
MoJo Vision’s MoJo Lens is a contact lens designed as a tiny screen that provides heads up information, i.e. you don’t have to look down at a smartphone screen. The lens has a micro-LED display, which is the smallest and densest display developed. While this technology has been developed for use by the normally sighted, the potential for those with low vision is in its other functions for vision enhancement: contrast, lighting, and zoom. This technology is still under development .
To Read more click here: MoJo Lens.
Why Contact Lenses are not Always the Best Solution
Low vision wearers of contact lenses have all the same responsibilities as those sighted wearers of contact lenses. Chief among the responsibilities are keeping them clean, proper handling, and avoiding contact lens over-wear.
Another consideration for the visually impaired is the insertion and removal of the contact lenses. The capability to get the lenses in to the eye can be a limiting factor.
While I know that contact lenses can be inserted and removed by feel, consider the difficulty in finding a dropped lens. It can be difficult to find, even for the sighted. There is also the care of cleaning and handling of the small, thin contact lens. This can be daunting for someone with low vision.
The process of getting the lenses in and out and caring for them will be a time consuming exercise, but if sufficiently motivated, can be learned by touch.
Contact lenses prescribed to correct high refractive errors, like high prescription eyeglasses lenses, tend to be thicker than average contact lenses. Because of the thickness the lens maybe uncomfortable to wear for long periods of time.
Specialty lenses that have the printed iris ring need to be fit well to insure that there is no interference by the edge of the tinted ring. This requires fitting by a specialist and most likely will be special order and not an off-the-shelf purchase.
Tinted lenses have the disadvantage of decreased visual acuity and contrast sensitivity in dim and low light settings. Unlike glasses, which can be removed, the light sensitive person may find themselves more visually impaired in these low light situations.
Finally, the issue of contact lens over-wear. This is common among sighted contact lens wearers. Over-wear is when contact lenses are left in too long. There are many reasons: forgetting, laziness, love-them-so-much-you-don’t-want- to-take-them out, and “I hate my glasses. “
Problems and complications are sure to eventually arise if not properly worn and cared for. Patients find they develop infections, red irritated eyes, allergic responses, and an intolerance to any contact lens wear. When dispensing contact lenses, the prescribing doctor will give you a wear schedule.
Interested in learning more…Why those with low vision refused low vision aid
In the end…
Those with vision impairment should not assume they will get better visual acuity with contact lenses. Wearing contact lenses most likely will be for the other reasons outlined in this article: light sensitivity and glare, comfort vs thick eyeglasses, appearance, or specialty lenses for magnification or field enhancement.