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How do you measure the diameter of contacts?

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Asked By: Ambar Kundera | Last Updated: 22nd January, 2020
Measure the diameter of a contact lens by laying a ruler with millimeters or an optical PD stick over the lens, but not on it, and measuring the widest point across the contact. Diameters of contacts are written in millimeters and average about 14 mm, according to Contact Lens Spectrum.





Likewise, people ask, how do you measure the diameter of contact lenses?

Move toward the convex side of the contact lens with the reticule until the contact lens is in sharp focus. Measure the contact lens and see how close the measurement is to the known diameter. In some situations, a penlight may be necessary to illuminate the cornea through the clear side of reticule.

Also, is the diameter of contact lenses important? Yes, it is quite important. When you are wearing contact lenses with bigger diameter than you need, the contact lenses are so loose that they move around everywhere and out of its own place. This causes discomfort and visual acuity. What’s worse, it may cause corneal damage by tearing or scrape your cornea.

Additionally, what is the normal diameter of contact lenses?

Most patients will fall in the range of 8.5 to 8.7 base curve (median) and 14mm would be averages. Typically its better for soft lenses to fit flatter than steeper. Soft lenses cover the entire cornea and actually extends past the limbal area by a few mm.

What is the difference between 14.2 and 14.5 diameter contacts?

In fact, there is not much difference between these two. Some manufacturers only make 14.2mm diameter contacts, and some others produce 14.0mm diameter contacts. Many 14.0mm contacts users use 14.5mm or 14.8mm contacts to demonstrate dolly effects on their eyes.

Can contacts be too big?

If the base curve of the contact lenses is too big, the contacts won’t sit perfectly om the eyes. It will moves around in your eyes and also make you uncomfortable. This is the reason why you need to take an eye examination for prescription before you buy contact lenses.

Are all contacts the same size?

No, not all contact lenses are the same size and same shape. Just like one shoe size doesn’t fit all, one contact lenses size doesn’t fit for all. Contact lenses are different in curvature.

What is the difference between 8.4 and 8.6 base curve?

The base curve (BC) of a contact lens is a measurement of the concavity of the inner surface – the curve that sits on the cornea. A BC of 8.4 mm of radius is more curved, and therefore a tighter fit, than 8.8 mm base curve. People who have steeper corneas require tighter fitting contacts.

What is the base curve and diameter of contact lenses?

Contact Lenses – Base Curve & Diameter
Contact Lenses Name
1-Day Acuvue
Power Range +6.00 to -10.00
Base Curve(s) 8.6, 8.8
Diameter(s) 14.2

Do different brands of contacts fit differently?

Unfortunately, not. Contact lenses come in different sizes and must be fit to your eye by an Optometrist or Ophthalmologist. If you would like to change the type or brand of lens you are wearing, your eye care professional will need to help you make that choice.

Is there a difference between 8.5 and 8.6 base curve?

The difference between an 8.5 and an 8.6 isn’t the curvature , but the fact that it is a different lens. Contacts are the same as shoes in a sense. Matching the curvature or diameter of a different brand does NOT mean it will fit the same, or even fit close sometimes.

How do you know what your base curve is for contacts?

We assess the Base curve by measuring the curvature of the cornea which you can only do using specialised equipment for that purpose, then selecting a trial lens with the Base curve we think will fit and then assessing the fit. We then can write a prescription for a lens with the correct Base curve, diameter and power.

Who Cannot wear contact lenses?

Unfortunately, not everyone can wear contact lenses. There are many reasons certain individuals are unable to wear contact lenses. It may be due to a health condition such as dry eye syndrome or the shape of their eye just doesn t allow for them to be able to wear contact lenses.

What does diameter mean for contacts?

BC or Base Curve: Every contact lens has a “base curve”. The number indicates the steepness or flatness of the contact lens. DIA or Diameter: Every contact lens has a diameter. The diameter determines how much the lens will cover your cornea. Most contact lenses today come in just one diameter.

How important is base curve in contacts?

Base Curve (BC) is a measure of the curvature of the contact lens. This helps it fit your cornea more comfortably since some corneas are “steeper” or “flatter” than others. The higher the Base Curve number the “flatter” the curvature of the cornea. How do you determine the diameter for contact lenses?

What is the average eye diameter?

24 millimetres

Does base curve affect vision?

If the base curve is flatter than prescribed (ex: 8.8 instead of 8.4), it may not affect vision, but it will affect fit. The lens will most likely move too much, and the edges may tend to curl outward. There is more base curve flexibility with soft lenses as they conform more or less to the cornea.

Can contacts be too small?

If the diameter of the lens and the base curve are incorrect in size, whether it’s too large or too small, it can be very uncomfortable. Keep in mind most people should be able to wear contact lenses for up to 12 hours comfortably if it fits right.

What is the smallest contact lens diameter?

Types Of Scleral Contact Lenses

Scleral contacts are noticeably larger than standard gas permeable (GP) contacts and have a diameter equal to or greater than that of soft contact lenses. The smallest sclerals are approximately 14.5 mm in diameter, and the largest can be up to 24 mm.

Are daily contacts better than monthly?

Monthly Lenses

Replaced either monthly or bi-weekly, these contact lenses are thicker than daily disposables. The thicker composition makes them more durable and long-lasting, and they are usually more resistant to drying out. However, they must be disinfected regularly in order to ensure healthy wearing.

How do you start wearing contacts?

5 Tips for First Time Contact Lens Wearers
  1. Relax. Lots of people worry that they’ll scratch their eyes while putting their lenses in or—worse—that the contact lens will get stuck behind their eye.
  2. Keep lenses clean. Don’t take shortcuts with lens cleaning.
  3. Hydrate.
  4. Follow your doctor’s recommendations.
  5. Adhere to the prescribed wearing and replacement schedule.

What is the difference between 8.4 and 8.5 base curve?

Studies show that a single base curve of 8.4mm managed a “good or better” fit in approximately 90% of individuals,1 and base curves of 8.4mm and 8.6mm together encompassed 98% of individuals.



LENS BASE CURVES AVAILABLE (mm) DIAMETERS AVAILABLE (mm)
4 8.4, 8.6 13.8
5 8.6 14.0
6 8.5, 9.0 14.2
7 8.4, 8.8 14.0

  • 12
  • 39
  • 39
  • 39
  • 24
  • 37
  • 16
  • 36
  • 29
  • 39