Yan's Optometric Centre

The refractive state of the eye changes with age, ocular health and visual habits. Even without blurred vision, adults are advised to have a comprehensive eye examination once a year; children every 6–12 months, to track myopia progression and start myopia control early. A full examination can also detect early glaucoma, macular disease, retinal disease, squint and amblyopia.

Why you should not just buy glasses casually at street shops or online?

Fast street refractions only measure a rough prescription and ignore clinical assessments such as corneal shape, tear film, binocular coordination, pupillary distance and ocular health — the glasses produced may not suit your eyes.

Consequences of glasses with the wrong prescription

Adults: eye fatigue, headaches, brow pain, distorted vision, dizziness, nausea and reduced concentration.
Children (under 8, a key period of visual development): inaccurate correction can accelerate myopia progression and, in severe cases, cause amblyopia with permanent visual impairment.
Even if the spherical power is correct, wrong pupillary distance or astigmatic axis can keep the eye's focusing muscles overworked with long-term wear.

Note: Long-term wear of wrongly prescribed glasses in adults generally does not cause permanent structural damage to the eyeball, but it can cause persistent visual fatigue; in children, whose eyes are still developing, the impact is far more serious. All spectacle dispensing should be based on a prescription made by a registered optometrist after a full examination.

Multifocal progressive lenses have continuously changing powers across a single lens — the top for distance and the bottom for near vision. The adult version is used for presbyopia; children's myopia-control multifocal lenses work by creating peripheral myopic defocus signals to slow axial length growth.

✅ Benefits

• Adult presbyopia: one pair of glasses for distance, intermediate and near, without swapping between two pairs
• Children's myopia-control multifocal lenses: compared with ordinary single-vision lenses, they can gently slow myopia progression, suitable for children who cannot or will not wear Ortho-K or contact lenses
• Non-contact, no corneal infection risk

⚠️ Limitations

• There are distortion zones at the sides of the lens and peripheral vision may appear distorted, requiring an adaptation period; some people cannot adapt
• Traditional progressive multifocal lenses give weaker myopia control than the newer defocus lenses, and the effect diminishes over time, declining after about a year
• Very demanding on pupil height and frame position; inaccurate dispensing can cause headaches and visual fatigue
• More expensive than ordinary single-vision lenses

Photochromic lenses contain light-sensitive molecules that darken automatically when exposed to UV and return to clear indoors when there is no UV. High-quality photochromic lenses block 100% of UVA and UVB. Long-term UV exposure increases the risk of cataract, pterygium and macular degeneration.

✅ Benefits

• Two lenses in one: ordinary glasses indoors, automatically turning into sunglasses outdoors, no need to carry a second pair
• Newer photochromic lenses filter some indoor blue-violet light, reducing screen glare

⚠️ Limitations

• Limited effect in the car: car windows block most UV, so the lenses darken less while driving
• High temperatures can affect the speed of darkening and fading
• After several years, the maximum depth of darkening gradually reduces
• Not suitable for people who are extremely light-sensitive or need consistently dark sunglasses

New-generation lenses such as DIMS, HALT and diffused optics (DOT) use defocus or contrast-modulation technology to maintain clear central vision while creating peripheral retinal myopic defocus signals that restrain excessive axial length growth.

✅ Benefits

• Large randomised controlled studies: DIMS lenses slow myopia progression and reduce axial length growth; compared with ordinary single-vision lenses, some children had no myopia increase over two years
• No contact lens wear and no corneal infection risk, suitable for children who cannot accept Ortho-K
• Simple to wear and simple to care for

⚠️ Limitations

• Individual variation is large: some children respond weakly and need monitoring of axial length and prescription every 6 months
• Peripheral vision is slightly reduced and some children need time to adapt
• Higher cost
• Cannot reverse myopia that has already developed, only slow further progression