If you wear multifocal contact lenses, you may have noticed small letters like “D” or “N” printed on them. These letters actually have an important meaning – they indicate the type of vision correction provided by that part of the lens. Understanding what D and N stand for can help ensure you are getting the proper vision correction from your multifocal contacts.
What is a Multifocal Contact Lens?
A multifocal contact lens has more than one zone of focusing power, allowing the lens to correct both distance and near vision. The central zone corrects for distance vision, while rings around the center provide near and intermediate vision correction. This means you can clearly see objects both up close and far away while wearing multifocal contacts.
| Zone | Vision Correction |
|---|---|
| Central zone | Distance vision |
| Middle ring | Intermediate vision |
| Outer ring | Near vision |
The transition between the zones is gradual, providing a seamless range of vision. Multifocal contact lenses are a popular option for people with presbyopia who want to reduce their dependence on reading glasses.
What Does the “D” Stand For?
On a multifocal contact lens, a “D” indicates a zone that corrects for distance vision. The D zone will be the central portion of the lens. This provides clear focus on objects that are farther away.
Distance vision correction is usually needed for seeing clearly at lengths beyond arm’s reach. This includes activities like:
- Driving
- Watching TV
- Seeing people from across the room
- Playing sports
- Reading signs and menus
The D zone gives you sharp distance vision for all these needs. The D is typically larger on multifocal lenses to provide a wide field of view for distance activities.
What Does the “N” Stand For?
An “N” on a multifocal contact indicates a zone that corrects for near vision. This will be the ring around the D zone. The N zone allows clear focus on close-up objects.
Near vision correction is important for tasks within arm’s reach like:
- Reading
- Using a computer or phone
- Applying makeup
- Seeing dashboard controls while driving
- Cooking or looking at recipes
- Any detailed handiwork
The N zone provides the magnifying power needed for all these up-close activities. Depending on your prescription, you may have one N zone or multiple staggered N zones to optimize near vision at varying distances.
How are the Zones Distributed in Multifocal Contacts?
Here is a typical layout of the zones on a multifocal contact lens:
| Zone | Location | Vision Correction |
|---|---|---|
| D | Center | Distance |
| N1 | Inner ring around D zone | Near, around 16 inches |
| N2 | Outer ring around N1 zone | Near, around 12-14 inches |
However, this can vary depending on the design of the multifocal contact and your specific prescription needs:
- More N zones may be added for enhanced near vision at varying distances.
- The sizes of the D and N zones may be adjusted based on whether you need more help with distance or near vision correction.
- Some lenses have a crescent N zone instead of a full ring to allow more uninterrupted distance vision.
How to Tell if Your Multifocal Contacts are Inside-Out
Because multifocal contact lenses have different zones, it’s important to put them in the correct way. If your contacts get flipped inside-out, the D and N zones will be reversed. This can seriously affect your vision!
Here are some tips for making sure your multifocal lenses are properly oriented each time you insert them:
- Look closely at the edges – the D or N lettering should be readable and facing out, not reversed.
- Pay attention to the sizes of the central and surrounding zones – the D should be larger.
- The outer edge may have additional near power markings that should be visible.
- You may feel slightly more resistance inserting the lens if it’s inside-out.
If you notice any signs of reversed D and N zones, remove the lens immediately and insert it again right-side-out.
Pros and Cons of Multifocal Contact Lenses
Here is a quick overview of the key pros and cons associated with multifocal contact lenses:
| Pros | Cons |
|---|---|
| Provide all-in-one vision correction for distance and near | More expensive than single vision lenses |
| Convenient – reduce need to switch between glasses | Adjustment period to get used to progressive vision |
| Allow clearer vision at all ranges | Vision can be worse if lenses rotate or are inside-out |
| Avoid having to tilt head back to see distance through bifocals | May not provide as sharp vision as single vision lenses |
The D and N lens markings are key to understanding the visual benefits and compromises inherent in multifocal contact lens designs. Having realistic expectations and practicing good lens insertion habits can help maximize the advantages while minimizing the disadvantages.
Conclusion
The D and N printed on multifocal contacts provide simple yet crucial guidance for getting the optimal performance from these specialized lenses. D indicates zones for clear distance vision, while N denotes areas for sharp near vision. Knowing what the letters mean and how the zones are laid out can help you orient your lenses properly and gain great all-around eyesight!
Multifocal contact lenses are an excellent solution for active people needing varying levels of vision correction throughout the day. Just be sure to follow your eye doctor’s recommendations for care and insertion techniques. With practice, multifocal contacts can give you the gift of glasses-free distance, intermediate, and near vision!
