Refraction and Eyeglasses Prescription

Why is accurate refraction necessary?

Eyeglasses and contact lenses correct how light is focused on the retina. An inaccurate prescription leads to fatigue, headaches, blurring, double vision and similar problems.

A medical prescription differs from a simple measurement at an optician's shop: it includes a clinical assessment of eye health, suitability for age and habits, and forms the basis for safe driving or work whenever certification is required. It is often included in the comprehensive eye examination (check-up).

The main refractive errors

These typically include:

• Myopia — difficulty seeing at a distance
• Hyperopia — fatigue or blurring, especially with prolonged near work or when not fully corrected
• Astigmatism — distortion due to a non-spherical cornea, often coexisting with myopia or hyperopia
• Presbyopia — a normal change after around 40–45 years of age, causing difficulty focusing up close (phone, newspaper)
• Anisometropia — a difference in correction between the two eyes, requiring a tailored prescription and correct lens centring

The final prescription combines spherical and cylindrical power (astigmatism axis), additional near power (add) where needed, and guidance on the intended viewing distance (desk work, driving).

For presbyopia, options include separate lenses for distance and near, multifocal lenses for multiple distances, or ergonomic desk solutions when work is fixed at a specific distance.

How is the examination performed at the practice?

An automated refractometer is used first for an objective estimate, followed by subjective refraction ("better or worse?") to optimise visual quality and comfort.

Visual acuity with and without correction is checked, balance between the eyes is assessed, and near tasks (reading, screen use) may be tested depending on your needs. When the cornea raises concerns for contact lens wear, or before certain procedures, corneal topography / Pentacam may be recommended as a complement.

The length of the visit depends on your previous prescription, whether dilation is needed when combined with a check-up, and any additional questions (night driving, sport, discomfort with old glasses).

Prescriptions for eyeglasses and contact lenses

An eyeglasses prescription refers to the distances at which the lenses are used (near, intermediate, distance, multifocal or single-vision lenses as appropriate).

Contact lenses require additional parameters and a healthy eye surface — with dryness or blepharitis, wear can be uncomfortable until the surface is treated; see dry eye syndrome & IPL and blepharitis treatment.

Multifocal or single-vision contact lenses for presbyopia are discussed when needs and tolerance allow; fitting may require a trial period and follow-up.

When is reassessment needed?

Vision and visual needs change over time (presbyopia, myopia in younger people, changes after pregnancy or medication).

After cataract surgery and placement of an intraocular lens, a new eyeglasses prescription or a review of near-vision correction is often needed; measurement is coordinated with the postoperative plan.

For a driving licence, vision requirements are covered as part of the electronic medical certificate when the request is combined with an examination.

Even without new symptoms, periodic review every 1–2 years (or more often if indicated) helps detect changes before they affect safety or quality of life, especially when there is a family history of glaucoma or diabetes; the link to a comprehensive check-up remains important.

Children and teenagers

In children, refraction varies (hyperopia, myopia, astigmatism) and may be linked to strabismus or amblyopia; the frequency of examination is determined by the ophthalmologist and is usually accompanied by a comprehensive check-up.

Early correction supports visual development and comfort at school; parents are informed about signs that call for re-examination (head tilt, difficulty seeing the board).

A child's prescription is reviewed when working distance changes (a new desk), while teenagers with heavy screen use may need a discussion of fatigue and ergonomics alongside the measurement.

Practical guidance

Bring your current glasses or old prescription, a list of medications, and describe your working distances (screen, driving, theatre work).

If you use contact lenses, mention the type and frequency of use so that the prescription and surface examination can be properly coordinated.

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