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Understanding Your Contact Lens Prescription

  • 20 Jul 2022

In Singapore, having a prescription is required by the health authorities even when buying contact lenses online . Therefore, having an updated prescription can be handy. It is also beneficial as it can help you acquire contact lenses that accurately fix your vision and comfortably fit in your eyes.

But contact lens prescriptions can get a little confusing if you don’t know how to properly read them. That is why we at Clearlabs have put together this article, such that you can better understand what the items on your prescription mean and put the information to better use when buying contact lenses in Singapore.

Base Curve and Diameter

The figure reflected under “BC” - Base Curve simply reflects what type of fit is required for a contact lens to meet the natural curve of your eye. It is usually measured in millimeters, though some prescriptions utilise general categories such as flat, median or steep.

Whereas “DIA” - Diameter simply refers to the diameter that the daily or monthly contact lenses you buy should feature, such that their width best fits your eye. Similarly, it is often measured in millimeters and should be presented to your optometrist or optics shop regardless of whether you’re buying in-store or online in Singapore.


The figure reflected under “Power” or “Sphere” indicates whether you’re short- or long-sighted and the degree of correction required to fix your blurry vision. If you have short-sightedness, your figure will begin with a minus sign; if you suffer from long-sightedness, your figure will begin with a plus sign instead.

The number goes up from 0 in measurements of 0.25. The higher the number, the more visual correction is required from the contact lenses you buy.

Cylinder and Axis

These figures are for astigmatism correction, and are relevant for toric lenses in particular.

The “Cyl” - Cylinder figure can either be a positive or negative number that increases in measurements of 0.25. This number denotes any extra visual correction requirements needed for astigmatism and how severe your astigmatism (if any) is.

The “Axis” figure determines the angle of correction required to fix blurry vision caused by astigmatism. Astigmatism results from irregular curvature of the eye, and this figure indicates the angle which your toric contact lenses have to feature in order to facilitate vision correction. The number should be between 0 and 180 degrees.

Addition and Dominant

These figures are for presbyopia, and are relevant for bifocal and multifocal contact lenses in particular.

The “Addition” figure determines what level of correction is required for you to see clearly at closer distances such as reading, working on a computer or using mobile devices. The number should range between 0.50 and 3.00, though some contact lens brands in Singapore use categorical terms such as high, medium or low.

The “Dominant” marking indicates the dominant and non-dominant eye, which is crucial in determining accurate visual correction with regards to bifocal or multifocal contact lenses.

Get a Free Prescription with Clearlab

Clearlab offers free eye examfree eye exams and prescriptions that can be easily accessed for contact lens purchase. Book a free eye exam with Clearlab today, and enjoy the convenience of buying your contact lenses online with Clearlab for your subsequent purchases.

Shop Clearlab for the best daily disposables and monthly contact lenses in Singapore today.



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Contact Xchange 2 years ago

Contact Xchange 2 years ago

A well versed briefing about adreesing the importance of contact lens prescription for the care of the eyes.