Myopia, also known as near-sightedness is a very common vision condition seen in patients across all ages, genders, ethnic, and socioeconomic groups. This condition causes objects far away to appear blurry or out of focus. It can also cause squinting and headaches due to eye strain if left uncorrected. The cause of myopia is largely genetics, but can also be a result of environment such as frequent and prolonged near point work, for example reading or working on computers and tablets - factors that our ancestors did not have working against them. Hunter/gatherer societies spent little time in the 12 -16 inch range. Myopia is being diagnosed at an alarming rate and is much more prevalent than it was generations ago. Myopia has reached epidemic proportions in parts of Asia with nearly 80% of urban Asian children needing corrective lenses, according to Paragon Vision Sciences, one of the leading manufacturers of orthokeratology contact lenses. The National Eye Institute warns that myopia could impact 39 million Americans by 2020 and 44.5 million Americans by 2050.
So what’s the big deal, right? So more kids and adults may need to wear glasses. The impact is not only financial with the costs of eye care and eyewear over a lifetime, but can also affect quality of life, social, and academic development in children and adolescents. High myopia can develop into pathological myopia, which can have devastating and sight-threatening effects on the retina. Myopia increases the risk of glaucoma, choroidal neovascularization and later myopic macular degeneration, as well as retinal detachment. So it makes sense that we would want to control this condition as much as possible and care for our patients in a way that would slow down or even halt the progression of myopia. Controlling myopic prescriptions within lower parameters has become a public health concern the subject of a World Health Organization(WHO) joint consultation and global scientific meeting on myopia held at the University of New South Wales in 2015
There are multiple forms of myopia control that we can use in the office and we will discuss each of them here along with the pros and cons of each option.
1. Orthokeratology
2. Low dosage atropine drops
3. Multifocal contact lenses
4. Bifocal glasses
Orthokeratology, also known as ortho-k and corneal refractive therapy (CRT), involves reshaping the front surface of the eye - the cornea, using a hard contact lens that is designed to be worn overnight and be removed in the morning. The cornea is temporarily reshaped to bring the refractive error close to zero and therefore the patient would not have the need for glasses or contact lenses during waking hours. It is a non-surgical approach to correcting nearsightedness. Research has shown that the use of orthokeratology may permanently reduce the amount of the myopia that a young patient might naturally develop.
Ortho-K uses oxygen permeable contact lenses to gently change the curvature of the cornea overnight, thus reducing the amount of myopic prescription for most of all of the patient’s waking hours. Advancements in lens material and design, as well as optical instrumentation and the development of topography allows doctors to effectively observe and monitor corneal and refractive changes for the best results.
Patients that may be potential candidates for ortho-k therapy are those that lead an active busy lifestyle and would prefer to be lens free during the day. Patient that find soft lenses irritating and are constantly aware of their presence may find lenses worn while they sleep a perfect solution and fall in love with the freedom it provides. Those that are too young for lasik and other forms of refractive surgery or who are not a good candidate for surgical intervention could also benefit. Prescriptions of less than -4.00 diopters are ideal, but other prescriptions, including those with astigmatism, may not be automatically excluded. This kind of treatment is available for both young children and adults, but best for those under 40.
Reshaping the cornea only affects the outermost layer of the eye - the epithelium. The epithelial layer is compressed by the hard contact lenses overnight causing fluid of the tissue to move to other areas of the eye. The cells of the eye are not moved, redistributed, or destroyed. The intracellular fluid moves through channels called gap junctions. If a patient stops wearing the reshaping lens overnight, the fluids move back and the epithelium returns to its original shape. The patient would then experience their natural prescription once again.
Orthokeratology is considered a very safe option. As mentioned before, the mechanism of action is simply an epithelial phenomenon. Epithelial cells are not destroyed and the natural turn-over rate of these cells (about 7 days) would completely reverse the effect of the reshaping lenses. Ortho-K is slightly more invasive than wearing a soft contact lens during the day or a simple glasses prescription, however there are no permanent changes to corneal shape or physiology. Although you will find anecdotal evidence of permanent change to cornea, this is usually a result of a poorly fitting reshaping lens or non-compliance on the part of the patient.
THE PROS
- Non-surgical.
- Painless and comfortable process.
- Patients get the benefit of wearing no correction at all during the day and having their vision corrected while they sleep.
- Can be very convenient for those with an active lifestyle and athletes or with careers where safety is a concern such as law enforcement, military personnel, lifeguards, etc.
THE CONS:
- It is possible to see contact lens complications such as microbial keratitis. The prevalence is similar to those patients who sleep in a soft contact lens.
- More expensive option than other choices. Fees range from $1500 to $2500 depending on your area and provider.
- Many followups and office visits could be necessary, especially in the initial fitting stages.
Low dosage atropine drops (0.01%) has emerged as an effective way to reduce the progression of myopia and has been used and studied in Asian countries for many years. Atropine was first used in the 19th century as an agent to dilate the pupil for ophthalmological examination or surgery. Its use in myopia control in the United States has lagged somewhat because of a lack of formal guidelines for practitioners to use for a treatment model. However, as more studies are completed, it is quickly gaining in popularity by many doctors, both for its effectiveness and ease of use. This treatment option involves administering one drop of 0.01% atropine once daily to both eyes and wearing their current prescription glasses or contact lenses. The exact mechanism of how atropine therapy works is still unknown. It has been suggested that regulation of the receptors in the scleral and retinal cells is influenced by atropine. Because myopic eyes generally have a longer than average axial length, atropine is thought to be beneficial by reducing this axial length.
THE PROS:
- Seems to be effective in many studies, but research is ongoing.
- Prices for a month’s supply can be affordable, ranging anywhere from $55 to $85.
- Easy to use for parents and young patients.
- With lose dosage, there are minimal effects on pupil size, the focusing system, and near point vision.
- No noticeable problems or side effects for the majority of patients.
THE CONS:
- Considered an off-label use of the drug, which may turn off some parents.
- Always a minimal risk of systemic side effects with any medication.
- Possibility of an allergy to atropine.
- Can be forgotten to use daily.
- Side effects are greater at higher concentrations, which are rarely used. But they include rapid heart rate, altered mental state, flushed skin, constipation, urinary retention, and dry mouth.
Distance centered multifocal (bifocal) contact lenses are also an option in controlling myopia. This means the center portion of the contact lenses is design for clear, sharp distance vision (distance centered), with peripheral rings of near power to help with up-close focusing. We traditionally used these contact lenses to correct for presbyopia in patients that need a different reading prescription than that of their distance prescription. We now know that these lenses can also help to slow or even halt the progression of myopia in patients that wear them daily. A multifocal contact lens essentially mimics the treatment zone of orthokeratology on the cornea.
THE PROS
- With the lens in place and properly fit, we know the patient is looking through the prescription the doctor ordered, not avoiding it as is possible when wearing the same prescription in frames.
- Easy treatment option and efficient. No different from wearing a typical soft contact lens in either comfort or care routine.
THE CONS:
- Young children may not be comfortable with the insertion and removal process of contact lenses.
- May need a lot of parental support.
- Some patients notice a mild blurriness to their close range vision, for some can be intolerable.
This option works off the theory of peripheral myopic defocus. This can be a bit of a hard concept to understand. Remember that the eyeball is just that - a sphere. But in myopia, that sphere is horizontally elongated a bit. So think egg shaped, instead of golf ball shaped. Therefore, the eye does not have complete focus across the entire back surface of the retina at any one time. The peripheral retina may be slightly out of focus, while your central field of view is nice, sharp, and crisp and completely in focus. In the central back wall of the eye, light is perfectly in focus, but in the periphery, light rays fall behind the retina. This elicits a change in the body to make the eye increase its length because the eye naturally wants those peripheral light rays to fall in front of the retina, where they would be in an eye that needs no prescription. This vicious growth cycle and feedback loop makes the eye even longer and makes the myopic prescription even stronger over time. This is where a bifocal prescription (which is simply more power used at near point) comes in. It moves the lights rays forward.
The best option for a young person using bifocal glasses as myopia control is an executive bifocal. This is in sharp contrast to the no-line bifocals you may be familiar with and some would say the least attractive option. However, an executive bifocal is very easy for a young patient to understand how to use. You look above the line to see far away and below the line to see up close. The line dividing distance and near point goes all the way across the lens and there is no blending as to this differentiation in power. However, there is virtually no image jump when looking back and forth at different focal points.
THE PROS:
- Easy to wear especially for young patients.
- Cost effective compared to some other options.
- Non-invasive compared to contact lenses.
THE CONS:
- Patient may not care to wear glasses.
- We don’t know if a young child will really use the bifocal for reading consistently.
- It is hard for some parents to grasp the fact that their young child is wearing glasses that look like grandpa’s.
- Executive lenses are less readily available as most people opt for newer technology (i.e. progressive bifocals).
- Some vision plans refuse to cover this kind of prescription for a young person.
If you are concerned about the rate your child’s prescription is progressing over his or her recent checkups, schedule an appointment to discuss the options available to you. Just like orthodontic care, it is an investment in your child’s future. Even if we cannot halt myopic progression completely, it may be the difference in quality of life. A -2.00 diopter myope is much more comfortable and functional uncorrected than a -8.00 diopter myope, not to mention the risks of certain ocular diseases associated with higher prescriptions. We would love the opportunity to help you and your family. Call or visit us today.