Special glasses for slowing short-sightedness: how defocus spectacle lenses work and what the numbers show
The optician says these lenses slow short-sightedness. What the tiny segments or rings do, what the two-year trials measured, and what wearing them every day involves.
- Ordinary single-vision glasses correct blur but do not slow the eye's growth: the ordinary-lens groups in both trials still progressed 0.85 D and 1.46 D over two years.
- Defocus lenses keep the centre clear for distance and add focusing power in small segments or rings around it. The trials tested the result, not the theory.
- In two-year trials in Chinese children aged 8 to 13, segment lenses slowed progression by 52% and eye growth by 62%, and highly aspherical lenslet lenses slowed it by 0.80 D and 0.35 mm.
- Longer daily wear gave a bigger effect: children wearing the lenslet lenses at least 12 hours a day slowed by 0.99 D. A lens left in the school bag does the job of an ordinary lens.
- Cochrane rates the evidence for these lenses as very low certainty and says there is limited evidence on stopping, so a slower rate is the goal, and the eye doctor decides the plan.
The optician says these lenses slow short-sightedness. The lens looks almost like any other, perhaps with a faint pattern of dots or rings when the light catches it. A fair question follows: what is that pattern doing, and does it work?
This page is about spectacle lenses only. It sets out why ordinary glasses do not slow the eye's growth, how the two main designs work, what the two-year trials measured, how long the effect has been followed, and what wearing them involves. The overall picture of drops, lenses and honest numbers is in slowing myopia down: drops, lenses and honest numbers, so this page goes deeper on lenses and does not repeat it.
Why do ordinary glasses not slow short-sightedness?
Ordinary single-vision glasses correct the blur but do not change how fast the eye grows. A short-sighted (rabun jauh) eye is longer than it should be, and in a growing child it keeps lengthening. The glasses put the picture in focus on the retina, the light-sensing layer at the back of the eye. They do nothing to the length.
The trials show this in their comparison groups. Children given ordinary lenses in the Hong Kong trial progressed 0.85 D (dioptres, the unit of the power) and their eyes grew 0.55 mm over two years. In the Wenzhou trial the ordinary-lens group progressed 1.46 D with 0.69 mm of growth. Wearing the right power is still essential for seeing; it is simply a different job. Leaving the power under-corrected does not help either, as the page on wearing glasses all the time explains.
How do defocus spectacle lenses work?
They give the child clear distance vision through the centre of the lens while small zones around it add extra focusing power. The aim is a constant, gentle blur of that kind in the eye's outer field, together with sharp central vision. The Hong Kong team described the idea in one line: clear vision with constant myopic defocus can slow myopia progression.
Two design types have randomised trials. In the first, a clear central zone is surrounded by many small segments, in a honeycomb pattern, each adding +3.50 D of power. In the second, tiny lenslets with a special curved (aspherical) shape sit in concentric rings, and the Wenzhou trial compared a highly aspherical version with a slightly aspherical one.
The lenslets can be visible under some lighting, so a parent may notice a pattern. I describe designs and not brands here, because the evidence is about the design, and I will not tell you one maker is better than another.
What do the trials actually show?
Both designs slowed progression compared with ordinary lenses over two years. In the Hong Kong trial of 183 children aged 8 to 13, the segment lens group progressed 0.41 D against 0.85 D, and eye growth was 0.21 mm against 0.55 mm. That is 52% slower for refraction and 62% less eye growth. In that trial 21.5% of children in the treated lenses had no progression, against 7.4% in ordinary lenses.
Put that in everyday terms. Prescriptions are written in steps of 0.25 D, so a gap of 0.44 D over two years is under two steps in the child's favour. That is a slower climb, not a halt, and most children in the treated group still progressed. The number you take home is a rate, and the eye doctor tracks it.
In the Wenzhou trial of 157 children who finished, aged 8 to 13, the highly aspherical lenslet lenses slowed refraction by 0.80 D and eye growth by 0.35 mm against ordinary lenses. The slightly aspherical version managed 0.42 D and 0.18 mm. Both trials were in Chinese children, which matters when you read the numbers in Malaysia.
Cochrane's 2025 living review, which pooled 104 trials in 17,509 children aged 4 to 18, rated the spectacle lens evidence as very low certainty for peripheral plus lenses and low for multifocal lenses, and said results were often heterogeneous. Very low certainty does not mean they fail. It means the size of the benefit may move as better trials arrive.
Does the effect last, and what happens if the lenses are stopped?
In the Hong Kong follow-up, the effect held in a third year. Children who kept the segment lenses changed no faster in year three than in the years before. Children who switched from ordinary lenses to the segment design in year three progressed far less that year than in their first two years. Both groups did better than historical controls of the same age.
What happens after the lenses are stopped is less clear. Cochrane found limited evidence on whether stopping myopia control speeds progression beyond the rate expected for a child's age, and the Hong Kong team said it planned to follow children who stopped. So the evidence does not yet show whether anything happens when the lenses stop. When myopia treatment can stop covers how a stop is planned. The decision belongs to the eye doctor who knows your child's numbers.
Who suits these lenses, and how many hours must they be worn?
The trials enrolled children aged 8 to 13 with mild to moderate short-sightedness, and the lenses need to be worn all waking hours. In the Hong Kong trial the average wear was about 15 hours a day. In Wenzhou, children who wore the highly aspherical lenses at least 12 hours a day slowed by 0.99 D and 0.41 mm, against 0.80 D and 0.35 mm for the whole group. The authors state that longer wearing hours gave better control.
So the lens that spends the afternoon in a school bag is an ordinary lens. For a younger or older child, or a stronger prescription, no trial here answers the question, and the eye doctor will weigh it. Fussy about glasses? What to do when a child needs glasses helps with the habit first.
Comfort is usually manageable. In the Hong Kong trial some children noticed slight blurriness in the outer field at first and adapted within a few days. Ghost images, dizziness and headache were rarely reported, and no treatment-related adverse event occurred. The Wenzhou trial recorded no severe adverse events. If your child is still unhappy after a couple of weeks, say so.
How do they sit beside drops, overnight lenses and red light?
They are one of four families of treatment, and none replaces the eye doctor's judgement. Low-dose atropine drops are a daily medicine with their own trade-offs. Overnight lenses reshape the front of the eye and bring a hygiene routine. Red light therapy is a newer device-based option with its own questions. A spectacle lens asks the least of the eye itself, because it is glasses.
Whether to combine a lens with another treatment is a decision for your child's doctor. Cochrane notes that better studies of treatments alone and in combination are still needed. For the questions to ask before you spend money, see ten questions to ask before you pay for myopia control.
What are the practical points: fit, review and the first weeks?
Ask how the fit was checked, wear the glasses full-time, and keep the review visits. The design has a clear centre with treatment zones around it, so the lens needs to sit properly for your child's eyes and frame. Ask who checked that, and what to do if the frame bends or the lens scratches.
The IMI clinical management report advises review at least every six months for a child whose short-sightedness is progressing. At each visit the doctor can see whether the number and the eye's length are changing as hoped, and whether a different plan is needed. The aim is a slower rate, not a stop. If the number is still climbing fast, ask about changing or adding to the plan, and see how fast is too fast for yearly change by age.
- Is not wearing the lenses for most of the day, or keeps taking them off.
- Still has blurred vision, dizziness or headaches after the first two weeks in the new glasses.
- Has a prescription that keeps climbing fast between reviews.
- Has a bent frame or scratched lens, or glasses that no longer sit properly.
- Suddenly sees flashes of light, a curtain over the vision or double vision: go the same day.
Common questions
Do special glasses really slow short-sightedness?
How do defocus lenses work?
Why can't my child just wear ordinary glasses?
How many hours a day must they be worn?
Is it uncomfortable at first?
Does the effect last, and what if we stop?
Can defocus lenses be used with atropine drops, overnight lenses or red light?
the reference pages Myopia control in Malaysia →
- British Journal of Ophthalmology · Defocus Incorporated Multiple Segments (DIMS) spectacle lenses slow myopia progression: a 2-year randomised clinical trial (Lam et al., 2020) · pubmed.ncbi.nlm.nih.gov
- British Journal of Ophthalmology · Myopia control effect of defocus incorporated multiple segments (DIMS) spectacle lens in Chinese children: results of a 3-year follow-up study (Lam et al., 2022) · pubmed.ncbi.nlm.nih.gov
- JAMA Ophthalmology · Spectacle Lenses With Aspherical Lenslets for Myopia Control vs Single-Vision Spectacle Lenses: A Randomized Clinical Trial (Bao et al., 2022) · pubmed.ncbi.nlm.nih.gov
- Cochrane Database of Systematic Reviews · Interventions for myopia control in children: a living systematic review and network meta-analysis (Lawrenson et al., 2025) · pubmed.ncbi.nlm.nih.gov
- Investigative Ophthalmology & Visual Science · IMI Clinical Management Guidelines Report (Gifford et al., 2019) · pubmed.ncbi.nlm.nih.gov