Spectacles wear is the oldest and still the most popular method of correcting myopia in children. Parents are naturally concerned if glasses should be prescribed for their young children and if so, how strong and how often should they be worn? There is also the fear that constant wearing of spectacles will cause myopia to worsen faster.
A search of the ophthalmic and optometric literature will find that there are no hard and fast rules with respect to spectacles wear in myopia.
A rational and individualised approach to spectacles wear is proposed here. The plan will take into consideration the severity of myopia, the rate of myopia progression, the child’s vision demands and the child’s visual comfort with his existing glasses. The plan will also incorporate our knowledge of factors affecting myopia onset and development. By following the guidelines outlined here, you will be able to help tailor the most appropriate spectacles wear strategy for your child.
SPECTACLES MANAGEMENT PLAN: SOME DEFININTION
Low Myopia is myopia of less than –2.50 dioptres
Moderate Myopia is myopia of between –2.50 to –6.00 dioptres
High Myopia is myopia of more than –6.00 dioptres
“Distance wear” is spectacles wear for activities that require clear distance vision. Examples of such activities include copying notes from the board up front in the classroom, attending lessons in a large lecture hall, watching movies when seated at the back and participating in sports require precise hand-eye coordination like badminton, squash or archery.
“Normal wear” is spectacle for activities where there are minimal visual demands made on the eyes for clear distance vision. Examples of such activities include readiing, studying, computing, doing school homework, playing indoors, most hobby activities and physical sports like jogging, swimming or weight training.
SPECTACLES WEAR PLAN: FOR CHILD WITH LOW MYOPIA
The child with low myopia sees well for close distance and hence does not need to wear spectacles for reading and other near vision activities. However, because distance vision is blurry, a pair of spectacles is prescribed to be worn for “distance wear” activities.
Spectacles are also worn when going out at dusk or at night. This is because myopia worsens under conditions of dim illumination. This optical phenomenon is explained by the “dark focus of accommodation” and the “myopic-shift” effect.
Spectacles wear is optional for “normal wear” activities as the child with low myopia is less dependent on glasses. If the child is comfortable and happy vision-wise not using glasses for “normal wear” activities, he can be left alone and spectacles wear need not be enforced here.
On the other hand, some children with low myopia will prefer to wear their glasses all the time i.e. for both “normal wear” and “distance wear” activities. They can do so but they are still be encouraged to remove them when reading or doing other close vision work such as studying and working on the computer.
The exception to these guidelines will be the young child of 6 years or less who also suffers from lazy eye (amblyopia) or significant astigmatism. In these cases, the child is advised to wear his spectacles all the time.
In most cases, spectacles are preferably prescribed with slight under-correction. The exact amount of under-correction is best determined by the child’s visual response and preference during the subjective refraction test. Usually an under-correction of –0.25 to -0.50 dioptres suffices.
SPECTACLES WEAR PLAN: FOR CHILD WITH MODERATE MYOPIA
The child with moderate myopia is very much more dependent on glasses and will therefore need to wear his glasses for both “distance wear” and “normal wear” activities including reading. If glasses are not worn for reading, the child will need to hold reading materials at an uncomfortably close distance of 33cm (13 inches) or less to read, resulting in eye strain and fatigue.
If Child Has Not Worn Glasses Before
Spectacles are preferably prescribed with slight under-correction. The amount of under-correction is best determined by the child’s visual response and preference during the subjective refraction test. In most cases, glasses are prescribed with a slight under-correction of –0.50 dioptres.
If Child Already Has Glasses
If the child is already wearing glasses, it is important to firstly ascertain that the existing glasses are not over-correcting the myopia. Bear in mind that there is higher risk of prescribing over-corrected glasses in children due to their strong and active focusing muscles. This is especially likely to occur in young and uncooperative children. Whenever the refraction findings are in doubt, the child should be referred to an eye doctor for a Cycloplegic Eye Examination.
If the existing spectacles are found to be over-corrected, they must not be worn and should be replaced immediately as wearing them will strain the eyes and aggravate the myopia.
If the existing glasses is found to correct the myopia fully or within –0.50 dioptres of under-correction, they can be kept.
If the existing spectacles are under-correcting the child’s myopia by –0.75 dioptres or more, they should not be immediately replaced with a stronger prescription. Instead consider the “two spectacles” or the “progressive spectacles” management strategy.
THE “TWO SPECTACLES” WEAR STRATEGY
This strategy is considered for the child suffering from moderate to severe myopia when significant myopia progression has occurred and the exiting spectacles that the child is wearing have thus become significantly under-corrected. Instead of immediately and routinely prescribing a stronger pair of glasses, the child is first asked about his vision comfort with his existing glasses for “normal wear” activities. If the reply is that he is comfortable, happy and ha no problems vision-wise with his spectacles for “normal wear” activities, then the current prescription can be left alone.
However, the child is still prescribed a second pair of full correction glasses to be worn for “distance wear” activities and when going out at night. It is important to instruct the child properly on the circumstances of wear for the two spectacles and to supervise wear for the initial few weeks. To avoid confusion, the under-corrected glasses the “strong” pair. The child goes to school wearing the weak pair but brings along the strong pair in the school bag for use when needed. When at home, he should be wearing the weak pair for “normal wear” activities. For studying and computer work, he wears the weak pair. When attending lectures or activities in the school hall or when going out at night to watch movies, he should be using the strong pair.
The “two spectacles” wear strategy is also considered for the child who complains of spectacles intolerance with full correction spectacles. Here, an under-corrected pair is prescribed for “normal wear” with the full correction spectacles reserved to be worn only occasionally for “distance wear” activities.
“PROGRESSIVE SPECTACLES” WEAR STRATEGY
It has been theorized that the myopic child suffers from defective focusing ability. This causes a chronic blur o the retina, which in turn induces myopia development. Others have theorized that by reducing the level of accommodation or amount of near focusing work that the eye’s ciliary muscles have to do, myopia progression can be retarded. Upon these theories lies the rationale for advising progressive spectacles wear in children for myopia control.
Progressive spectacles are essentially glasses that are prescribed with full correction in the upper segment for distance vision and reduce power in the bottom segment for near vision work. Hence the level of accommodation needed for near work is significantly reduced. They are closely related to the bifocal glasses prescribed for middle-age farsightedness. However, unlike bifocal glasses where the change between the distance and near segments is abrupt (seen as a line across the lenses), progressive lenses have a seamless transition corridor from distance power to near thus allowing uninterrupted clear vision for distance and near.
Although the myopia control benefits of wearing progressive spectacles has yet to be conclusively proven, the rationale appears sound and is probably harmless. Indeed, research studies are presently underway at the Singapore Eye Research Institute and the National Institute of Health, USA to determine conclusively if wearing progressive lenses help in myopia control.
The “progressive spectacles” wear strategy is perhaps best considered for the child with moderate too high myopia who suffers from rapidly worsening myopia. It can also be recommended in place of the “two spectacles” wear strategy. Progressive spectacles can also be prescribed for children using atropine eye drops for myopia control where accommodation (focusing) power is diminished by the eye drops.
Progressive glasses are prescribed with full or close to full myopic correction for distance in the upper segment and reduced correction (usually less by –1.00 to –1.50 dioptres) for the lower “reading” segment.
The child of course needs to be instructed to look through the bottom segment of the lens when reading or doing near vision work. Another advantage of progressive lens, not often touted but especially helpful when myopia power is high, is the reduced overall thickness and weight of the lenses.
Not all children adapt well to wearing progressive glasses initially. Younger children tend to adapt better. The usual complaints are of dizziness and a swimming sensation. This is due to optical aberrations induced when looking outside of the narrow transition corridors. Hence the child should be instructed to turn his face when looking sideways. Adjustment is also slow if there is high astigmatism. However, with persistence and frequent reminder to the child to direct his gaze appropriately, most will adapt quite well after a few weeks.
SPECTACLES MANAGEMENT PLAN: FOR CHILD WITH HIGH MYOPIA
The spectacles management plan for the child with high myopia follows that for the child with moderate myopia. However, other more aggressive myopia management strategies also considered here. These include:
- The early introduction of child to contact lens wear
- The use of atropine eye drops
- More frequent Optometric Reviews
- Regular comprehensive eye care counseling.
Each of these will be discussed in greater detail in the chapters that follow.
It is important to seek the help and advice of a good optometrist to minimize the disadvantages of wearing high-power myopic spectacles. These spectacles come with significant optical, physical and cosmetic disadvantages as follow:
Optical disadvantages: Objects viewed will appear smaller by 10% or more depending on the strength of the lens. Prismatic optical distortions induced when looking sideways or when the glasses are not well aligned frequently give rise to complaints of spectacles intolerance.
Physical disadvantages: The spectacles lenses tend to be thick and heavy. They weigh and slide down the nose frequently and leave pressure dents at the nose bridge and temples. The back of the ears often gets chaffed. In our local humid weather, they get foggy easily with environment changes.
Cosmetic disadvantages: The magnification effect of the lenses makes the eyes look unflatteringly small. The lenses are thick with unsightly refraction rigs at the sides. Compounded, they often make the wearer look unattractive and introverted.
All these can have significant negative psychological effects on the child. A good optometrist can help offset these disadvantages by selecting frames that are light, sit close too the eyes and have smaller frame fronts that fit smaller lenses. Higher index lightweight plastic lenses can be used. The lenses can also be tinted at the sides and the thick edges rounded off. It is also crucial to ensure that the optical centers of the lenses are correctly aligned with patients’ pupils.