You have probably sat through a supplier pitch that went something like this: “Our lenses are 14.2mm diameter, 8.6mm base curve, 38% water content, CE certified, premium quality.”

Technically, that sentence tells you everything. Practically, it tells you almost nothing.

If you are buying contact lenses for your brand or distribution business, you need to know what those numbers actually mean. Not for a test. For making decisions that affect your customers, your returns rate, and your reputation.

Let me walk you through the specs that matter, why they matter, and what to watch out for.

Diameter — the number everyone quotes

Diameter is the first thing buyers ask about. It is the total width of the lens, measured in millimeters.

For clear corrective lenses, standard diameter sits around 14.0 to 14.5mm. Color contacts tend to run slightly larger, typically 14.2 to 14.5mm. Some “big eye” designs push to 14.8mm or even 15.0mm.

The thing most buyers do not realize: diameter does not work in isolation. It interacts with base curve to determine how the lens actually sits on the eye. A 14.2mm lens with an 8.4mm base curve will fit differently than a 14.2mm lens with an 8.8mm base curve, even though the diameter is identical.

For your product line, diameter choice should match your target market. Southeast Asian and East Asian consumers generally prefer the 14.2 to 14.5mm range. Western markets tend toward 14.0 to 14.2mm for color lenses. If you are selling a single SKU across multiple regions, 14.2mm is usually the safest middle ground.

Base curve — the most overlooked spec

Base curve (BC) measures the curvature of the back surface of the lens. It is expressed in millimeters, with lower numbers meaning a steeper curve and higher numbers meaning a flatter curve.

Standard BC for soft contact lenses is 8.4 to 8.8mm. Some manufacturers offer 8.3 or 8.9 as well.

Here is why this matters more than most buyers think: base curve is the primary determinant of lens fit. A BC that is too steep (lower number) means the lens grips the eye too tightly, reducing oxygen flow and causing discomfort after a few hours. A BC that is too flat (higher number) means the lens moves too much, which can cause blurred vision, irritation, and a higher chance of the lens falling out.

Most Asian eye shapes work well with 8.6mm BC, which is why it is the industry default for color contacts aimed at Southeast Asian and East Asian markets. For Western markets, 8.6 to 8.8mm is more common.

As a brand owner, you should be offering at least two base curve options if your target market has diverse eye shapes. If you are starting with one, 8.6mm covers the widest range of users globally.

Water content — higher is not always better

Water content is the percentage of the lens that is water. It is one of the most misunderstood specs in the industry.

The common assumption is that higher water content means more comfort. That is true, but only up to a point.

Here is the catch: lenses with higher water content also tend to absorb more deposits from the tear film. They also dehydrate faster, pulling moisture from the eye to maintain their own water balance. So a 58% water content lens might feel amazing for the first few hours, then start to feel dry by hour six or seven.

Lower water content lenses, typically 32 to 38%, hold their shape better and do not dehydrate as quickly. They are actually more comfortable for all-day wear, even though the initial “wet” feeling is less dramatic.

For color contact lenses specifically, lower water content is often the better choice. The pigment layer already reduces oxygen permeability somewhat, and a low-water lens compensates by being more dimensionally stable and less prone to dehydration.

Practical guidance: for daily disposables, 38 to 42% water content is the sweet spot. For monthly or yearly lenses, 32 to 38% tends to perform better over the longer wear period.

Material — what the lens is actually made of

The material determines how oxygen reaches the eye, how the lens handles, and what kind of manufacturing process is required.

Traditional hydrogel lenses are made from HEMA-based polymers. They have been around since the 1970s and remain the most common material for color contacts. Dk values for standard hydrogels typically range from 10 to 30, depending on water content. They are affordable and widely available.

Silicone hydrogel lenses are the newer generation. They use silicone to allow significantly more oxygen to reach the eye, with Dk values ranging from 60 to over 150. They are more expensive to manufacture and the printing process for colored designs is more complex. Not every factory can produce high-quality color silicone hydrogels consistently.

For a wholesale or OEM buyer, the material choice has real cost implications. Standard hydrogel color contacts are the entry-level option, suitable for price-sensitive markets and promotional products. Silicone hydrogel color contacts position your brand in the premium segment and appeal to consumers who prioritize eye health.

Oxygen permeability — the number behind the comfort

Dk is the oxygen permeability of the material itself. Dk/t is the oxygen transmissibility, which accounts for lens thickness. This is the number that actually matters for eye health, since it tells you how much oxygen reaches the cornea.

The FDA recommends a minimum Dk/t of 24 for daily wear lenses. For extended wear, the number jumps to 87 or higher.

Standard hydrogel color contacts typically achieve Dk/t values in the range of 15 to 25. Silicone hydrogel color contacts can reach 30 to 80, depending on design and thickness.

If you are building a brand that positions itself around quality and eye health, Dk/t is one spec you should put front and center in your marketing. It is measurable, it matters to consumers who do their research, and it is a clear differentiator between budget and premium products.

Edge design — the invisible comfort factor

Edge design refers to the profile of the lens periphery. It is rarely listed on spec sheets, but it affects comfort significantly.

A well-designed edge follows the contour of the eye smoothly, reducing the sensation of the lens edge against the eyelid. Poor edge design causes awareness of the lens, especially during blinking, and can lead to redness and irritation.

Manufacturers keep their edge designs proprietary, so you will not find detailed specs here. But you can evaluate edge quality through wearing trials. Ask your supplier for samples and have multiple people test them for at least six hours. If anyone reports edge awareness or irritation, that is a red flag.

Certifications — your legal passport

Certifications are not just marketing checkboxes. They determine where you can legally sell your product.

For Europe, the CE mark under the Medical Device Regulation (MDR) is mandatory. The manufacturer needs to have technical documentation, clinical evaluation, and quality management systems in place. CE certification typically takes 6 to 12 months from application.

For the United States, FDA clearance is required. The process involves a 510(k) submission with premarket notification. FDA clearance generally takes 90 days for standard contact lenses, but the preparation can take 6 to 12 months.

For South Korea, KFDA (now MFDS) approval is needed. Other markets have their own requirements. Southeast Asian countries like Indonesia, Thailand, and the Philippines require local registration, often based on CE or FDA documentation.

When selecting a manufacturer, verify their certifications directly with the issuing body. A PDF certificate means nothing if you cannot confirm it is valid and current.

What to ask your manufacturer

Before committing to any supplier, here is a practical checklist of questions to ask:

• Can you provide a detailed spec sheet for each SKU, including diameter tolerance, BC tolerance, water content tolerance, and Dk/t test results?
• What certifications do you hold, and for which markets? Can I see the actual certificates?
• Do you have ISO 13485 certification for your quality management system? This is not legally required everywhere, but it signals a serious operation.
• Can you provide pre-production samples for fitting trials?
• What is your standard lead time for stock items versus custom orders?
• What is your defect rate, and what is your policy on defective products?

The answers to these questions will tell you more about a manufacturer than any spec sheet ever could.

MIOMI approach

At MIOMI, we handle OEM/ODM projects across all certification markets. We provide full specification transparency, pre-production samples for testing, and guidance on which specs make sense for your target market. If you are building a brand from scratch or expanding an existing product line, we can help you choose the right combination of parameters for your specific audience.

Ready to explore what custom contact lenses could look like for your brand? Reach out and let us talk specs.