Myopia Measurements: Hard vs. Soft Contact Lenses

Measurement of Myopia Degree

I would like to ask a question...
Today I went to get my glasses prescription.
I visited two different places, and since I wear rigid gas permeable contact lenses, the first place advised me to temporarily switch to daily disposable lenses and come back for a measurement in a week for more accurate results.
However, the second place told me that wearing rigid lenses wouldn’t affect the measurement, only soft lenses would.
Can someone tell me who is correct? I’m concerned that my prescription might not be accurate.

Additionally, I wear rigid gas permeable contact lenses for about 4.5 hours a day, and I notice blood vessels appearing in my eyes after that time.
Why does this happen? A friend mentioned it could be neovascularization.
What does that mean? Thank you for your help.

Hou, 10~19 year old female. Ask Date: 2005/10/27

Dr. Zhang Yanrui reply Ophthalmology

Rigid contact lenses can affect the curvature of the cornea due to their compressive effect; however, improper use of soft contact lenses can lead to corneal edema, which also impacts the accuracy of measurements.
Wearing rigid lenses is less likely to cause neovascularization because they have excellent oxygen permeability.
However, many people experience conjunctival hyperemia after wearing them for a few hours due to dryness.
It's important to note that the visible blood vessels are not neovascularization; true neovascularization can only be observed with a microscope in an ophthalmology setting.

Reply Date: 2005/10/27

More Info

When it comes to understanding myopia measurements and the differences between hard and soft contact lenses, it's essential to clarify a few key points regarding how these lenses interact with your eye's measurements and overall health.

Firstly, the advice you received from the two different optical shops reflects a common debate in the field of optometry. Generally, wearing hard contact lenses (also known as rigid gas permeable lenses) does not significantly affect the measurements of your eyes for soft lenses. However, it is often recommended to avoid wearing hard lenses for a short period before an eye exam to allow your cornea to return to its natural shape. This is particularly true if you have been wearing hard lenses for an extended period. The cornea can become slightly altered due to the pressure and shape of the hard lenses, which might lead to inaccurate measurements for soft lenses. Therefore, the first shop's advice to wait a week after removing hard lenses before measuring for soft lenses is sound.

On the other hand, the second shop's assertion that wearing hard lenses does not affect the measurements for soft lenses may hold some truth, but it is not universally applicable. The best practice is to follow the recommendation of the first shop, especially if you are transitioning from hard to soft lenses. This will ensure that the measurements taken are as accurate as possible.

Regarding your second concern about experiencing bloodshot eyes after wearing hard contact lenses for about 4.5 hours, this is a common issue among contact lens wearers. Bloodshot eyes can occur for several reasons, including dryness, irritation, or insufficient oxygen reaching the cornea. Hard lenses, while allowing for better oxygen permeability than some soft lenses, can still cause discomfort if worn for too long or if they do not fit properly.

The term "blood vessel proliferation" that your friend mentioned refers to a condition known as neovascularization. This occurs when the cornea is deprived of oxygen, leading to the growth of new blood vessels to supply the necessary oxygen. This can happen if contact lenses are worn for extended periods, especially if they are not designed for long-term wear. If you are experiencing bloodshot eyes consistently, it may be a sign that your lenses are not fitting correctly, or you may need to adjust the wearing schedule or switch to a different type of lens.

To address these issues, consider the following steps:
1. Consult Your Eye Care Professional: If you are experiencing discomfort or bloodshot eyes, it is crucial to consult with your optometrist or ophthalmologist. They can assess your eye health and determine whether your lenses are suitable for your needs.

2. Follow Recommended Wearing Times: Adhere to the recommended wearing schedule for your hard lenses. If you find that your eyes become uncomfortable after a certain duration, consider reducing the wearing time.

3. Consider Lens Options: If you continue to experience issues, discuss with your eye care provider the possibility of switching to a different type of lens, such as daily disposable soft lenses or a different brand of hard lenses that may offer better comfort.

4. Maintain Proper Lens Hygiene: Ensure that you are cleaning and storing your lenses correctly to prevent irritation and infection.

In conclusion, while both optical shops provided valid points, the recommendation to avoid hard lenses before measuring for soft lenses is generally the safer approach. Additionally, if you are experiencing bloodshot eyes, it is essential to address this with your eye care professional to prevent potential complications. Your eye health is paramount, and proper lens care and fitting are crucial for maintaining clear and comfortable vision.

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