When you order contact lenses, you’ll see measurements listed on your prescription and packaging — most commonly BC (base curve) and DIA (diameter).

These numbers determine how your contact lenses fit on your eye. A correct fit helps ensure:

• Clear, stable vision
• Comfortable wear throughout the day
• Healthy contact lens movement
• Proper oxygen flow to the cornea

Even small differences in these measurements can affect how your lenses feel and perform.

Often admired for their light appearance, grey eyes stand out for their complexity and distinctiveness. They differ from other light-coloured eyes not just in hue, but in structure, melanin concentration, and how light interacts with the iris.

The subtle interplay of light gives them a unique depth, often shifting slightly in tone depending on the environment. These characteristics make grey eye colour both rare and fascinating to explore.

Hazel eyes: colour, rarity and what makes them unique

Updated February 2026

Often described as a striking mix of green, brown and gold, hazel eyes are known for their ability to appear different depending on lighting and surroundings.

In this guide, we’ll explore:

Green eyes hold a special spot on the human eye colour spectrum. This attention-grabbing hue can range from a light, smoky sage to a deep emerald green. Some green-eyed people even have specks of blue, brown, or gold on their irises.

But appearance isn't the only thing that's captivating about green eyes. Here's a closer look at this unique colour.

There are a few kinds of brown eyes — light, dark, and everything in between — and each shade has a striking appearance. Though the eye colour is common in people around the globe, brown eyes are unique to each individual who has them. Read on to learn what makes brown eyes special, what causes a person to have them, and what benefits they can provide.

People with amber eyes have irises that combine brown with a yellow or golden hue. The iris is the tinted ring around the pupil that gives each eye its colour. Amber eyes sometimes resemble light brown eyes, but they're set apart by a warmer, honey-tinted tone.

How rare is amber eye colour?

Amber eyes are quite rare. It’s estimated that only 5% of people globally (1 in 20) have an amber eye colour.

Contact lenses offer a level of convenience that makes them a popular choice for many people who need vision correction. They allow for greater freedom of movement, making them ideal for active lifestyles. Plus, advancements in technology have made contact lenses more comfortable and easier to use.

When it comes to contact lenses, wearing the right lens shape for the curvature of your eye is essential for achieving your clearest vision. Standard contact lenses have a spherical shape, meaning the curvature is consistent throughout the lens. But if you have an uneven cornea or irregular eye shape, aspheric contacts may be a better choice for your vision correction.

Scleral lenses are a type of contact lens used to treat a variety of eye and vision conditions. These lenses are larger than regular contacts, allowing them to rest on the sclera (the white part of the eye) and conjunctiva (the clear tissue lining the front of the eye and inner eyelids). They arch over the cornea (the clear front layer of the eye), creating a smooth, even surface that enhances vision correction.