Dr. Brian Abert was recently contacted by a local high school to answer some questions for a report on myopia. The student had clearly done some good research on the subject and asked some very good questions. We agreed that these questions would probably be useful to other folks as well, so I publish them here for everyone to see:
Do you believe that the frequency of myopia is increasing? If so, why is it increasing and what can be done to stop the progression of myopia?
The frequency of myopia is increasing, and that increase is likely due to our evolving culture of device use. Many professions and hobbies now involve more near work, that is, staring at computer screens, tablet screens, and phone screens. The increased near work is thought to increase nearsightedness. Relaxing a patient’s focus through frequent breaks from their near work, or wearing proper glasses prescriptions (for example, computer glasses for those patients that work frequently at computers) can help reduce this effect.
How often do you think people should get their eyes checked for myopia? Is age a determinant in how often someone should get their eyes checked?
We recommend yearly eye exams for all patients. While myopia can result in challenging vision, it often times is not harmful to the development of the eyes. For uneven amounts of myopia (that is, a larger amount in one eye than the other), a young child might develop amblyopia, or “lazy eye.” In this way, myopia can result in long-term vision problems. Amblyopia prevention is an important reason that children should be seen early in life for their first eye exam. Along with the American Optometric Association, we recommend that children be seen for their first comprehensive eye and vision examination at 6-12 months of age. This exam, called an InfantSEE examination is provided by our office at no cost in an effort to build awareness of the need for children’s eye care.
What type of technology and tests do you use at your office in order to officially diagnose myopia?
Myopia is measured through a combination of objective and subjective testing. Objective testing includes retinoscopy, corneal topography, and auto-refraction. We use retinoscopy to determine the glasses prescription of young children (usually under 10 years of age) or patients that can’t respond to subjective testing questions. Corneal topography measures the curvatures of the front of the eye. We utilize an auto-refractor to estimate the patient’s glasses prescription (of which myopia may be a component). Subjective refractive involves asking the patient a series of questions and using those responses to arrive at a glasses prescription. Our office utilizes state-of-the-art automated phoropters for precise, comfortable refractions. Subjective refractive involves distance, intermediate, and near vision testing.
I understand that myopia is measured on a scale and that individuals may have a specific severity of myopia that is recorded as a number. What does this number mean and how is it derived?
Myopia, like astigmatism, presbyopia, and hyperopia, is measured using the unit of diopters. A diopter is defined as the inverse of the focal length. For example, an eye (or a lens) with a power of -2.00 diopters has a focal point of 50cm (1/2.00m). Myopia (also commonly referred to as nearsightedness) is when the eye is focused closer than ideal for distance viewing. Someone with a high prescription for example, -10.00 diopters , has a focal point 10cm in front of their eye. Anything further than 10cm from that eye will be out of focus.
As an optometrist, which form of treatment do you think is the best for myopia, and what pros and cons do these different treatments have. In other words, do you recommend a patient gets contact lenses, glasses, or surgery? What is your take on corneal ring implants and lens implants? What would be the reason for choosing one of these treatments over the other?
There are a variety of ways to treat myopia, and a large number of factors go into determining the best course of correction. Let’s consider each option one by one: Glasses – Useful for all ages and most glasses prescriptions. Depending on the patient’s occupation and hobbies, glasses are a great option for good binocular vision. Glasses also allow for binocular correction of presbyopia with progressive addition lenses. Contact Lenses – Good for patient with uneven (anisometropic, or a large difference between the left and right eye prescriptions). Specialty-fit contact lenses are good for post-surgical eyes (post-LASIK, post-RK, post-PKP, post-PRK, etc), or eyes with corneal diseases such as keratoconus and pellucid marginal degeneration. Some occupations and hobbies don’t allow for glasses wear so contact lenses are a good option. Some very high amounts of myopia (or other refractive error) make glasses too thick or heavy to be useful, and contact lenses are a much better option. Refractive Surgery – a great option for mild to moderate amounts of myopia in those patients who prefer not to wear contact lenses. Refractive surgery is best utilized by patients who have a stable glasses prescription (Generally, mid-20’s is a good age to consider LASIK and PRK). Intraocular Lenses – useful in cataract surgery and for those patients unable to undergo corneal refractive surgery. While the limitations of power correction (as limited by the cornea) are largely lifted by use of intraocular lenses, their placement in the eye requires preventative surgeries to prevent glaucoma. Ring implants are sometimes utilized to stabilize keratoconic eyes for contact lens wear and shouldn’t generally be considered for myopia treatment.
Do RGP (Rigid Glass Permeable) contact lenses slow or control myopia as they are said to? Are they better than most other “soft contacts?”
This is an ongoing debate in eye care, and I’ll tell you that historically, wearing GP lenses has been shown to reduce myopia. However, while this reduction may be statistically significant, it isn’t often practically significant. Hypothetically, if a patient wore GP lenses and slowed their myopia progression slightly as a result, they may (in their mid 20’s) by a -6.00 instead of a -6.50. While that is a statistically significant reduction, it isn’t much of a difference practically as in both scenarios, the patient would need to wear vision correction. Ortho-K or CRT lenses offer temporary reduction in myopia when the patient wears the lenses overnight and experiences a temporary re-shaping of their corneal epithelium.
It is often said that myopia correlates with headaches, and that frequent headaches may be a sign of myopia. Why is this?
Myopia itself results in blurred vision. To counteract the blur, patients often squint for better clarity (creating a pinhole-effect with their lids). The act of squinting can tire out the muscles around the eyes causing a headache. Many patients with myopia also have astigmatism which can also contribute to eyestrain.
What severity of Myopia do you usually see in your patients? Is it more common to see mild myopia, moderate myopia, or high myopia?
I’m not sure about the bell curve of power distribution as fare is mild, moderate, and high myopia. Generally, we think of myopia as a development over time. Kids generally start out farsighted which acts as a buffer as the eyes generally get more nearsighted (myopic) over time. A typical glasses prescription in a 1-year-old might be +2.00 (which is not prescribed as glasses, but just monitored over time). Around 6 or 7 years of age a child is likely right around 0.00 (neither near nor farsighted). From that point, any further myopic shift would result in a significant amount of myopia. If a young child (4 or 5 years of age) has myopia, then it is likely that their myopia will continue to develop. I would say that mild to moderate myopia is pretty common, and that high myopia, while certainly not rare, is a bit less uncommon.
What is the average age of your patients (diagnosed with myopia)? Do you think this says anything about how the human eye functions in correlation to age?
Oh shoot, I think I answered this mostly above already! Myopia typically starts being apparent in children’s eyes right around 7 or 8 years old. Sometimes even if myopia is diagnosed at that age, we will still continue to monitor it without prescribing glasses. Usually with younger kids I want to put off prescribing glasses until the myopia would be expected to start affecting their useful vision. I also try to correlate the patient’s complaints with their myopia when trying to treat it. Even a patient with a smaller prescription may need glasses if their vision bothers them, and likewise some patients don’t seem to notice amounts of myopia that we would usually expect would interfere with their vision. This often depends on personality, age, and interests.
Can you tell me more about computer glasses? What is special about computer glasses? Are they something worn to prevent myopia, or something worn to correct it?
This just gets back to the section on what a diopter is. Let’s say there is a patient that views a computer monitor at 50cm. That’s a little bit of a close viewing distance for a screen, but let’s use that in this example. Assume this patient doesn’t have a glasses prescription (or, if they do, they are wearing contact lenses. Remember that the point of wearing a glasses prescription is to put their eyes’ focal length far away (infinity to be precise) so the effective power of their eyes is 0.00 diopters. If they are viewing a screen at 50 cm, their eye has to focus by 1/50cm = 2.00 diopters of power. If you spend the day working at a computer screen, and your eye has to focus by 2.00 diopters all day, your eyes will get tired, and if you are young, you will have a stimulus for possible development of myopia. When I refer to “computer” glasses, I refer to a prescription that includes that 2.00 diopters. Now, even though this theoretical patient needs no glasses for distance, wearing a +2.00 diopter computer lens will place the focal length of their vision exactly at the distance they are working at (50cm) allowing their eyes to relax completely. Of course, when they are not working at 50cm, they will need to remove those glasses in order to see distance again. Of course, there are some great innovations in lens technology nowadays including blue light-blocking lenses (to help prevent macular degeneration when the patient gets older) and anti-glare coatings to improve vision and reduce eye fatigue which can be added to those computer lenses, but the magic of those lenses is just that we can customize their focal length to whatever distance the patient is working at.
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