Choosing Contact Lenses for High Corneal Curvature: A Guide

Q: Choosing Contact Lenses for High Corneal Curvature: A Guide

Hello, A： If wearing them feels uncomfortable, then they are not suitable contact lenses. <br>The values 43.5 and 40.75 refer to the refractive power, with 40.75 being flatter and having a lower refractive power. <br>The curvature of the eyeball can be measured during the refract

If the curvature of your eyeball is too steep (and even a daily disposable lens with a curvature of 9.0 mm is not suitable), how should you choose contact lenses?

Doctor, I apologize for the interruption.
I have never worn contact lenses before, but recently I went to an optical store to try them on.
They said that the fit was still quite poor, so I later ordered daily disposable lenses with a base curve of 9.0.
I wore them two or three times over different days, for about five to six hours each time, and the last time for approximately 12 hours.
I really felt quite uncomfortable.
When I moved my right eye, there was a sensation of something foreign in the upper part, and in my left eye, I felt a tightness, a heavy foreign body sensation, and sometimes a stinging pain.
I was hesitant to wear them again, and even after not wearing them for two or three days, I still occasionally experienced some stinging.

I would like to ask what level of discomfort is considered normal when wearing disposable contact lenses? (Could it just be dryness? Should there be no foreign body sensation?) I also visited an ophthalmologist and mentioned these issues.
He told me that I might not be suitable for wearing contact lenses.
He measured something, which I believe was the curvature of my cornea, referred to as K value.
He wrote down a number that seemed to indicate that the average person has a value of 43.5, while mine is 40.75.
He said there is indeed a difference (indicating a flatter cornea).
I am unsure what the unit of this number is.
I read online that the typical base curve for contact lenses ranges from 8.5 to 8.7, and that 9.0 is considered a larger, flatter curve.
I want to know if I need to convert this data (my 40.75) to understand my actual corneal curvature (perhaps my corneal curvature is around 9.5 or something similar)? Does this mean that a daily disposable lens with a base curve of 9.0 is still too small for me to wear? I sincerely apologize for the lengthy message, and I truly appreciate your patience in reading it.
The responses and the significance of the numbers provided by the ophthalmologist were quite vague and did not adequately address my concerns.
Thank you again, Doctor.

A, 10~19 year old female. Ask Date: 2022/03/16

Dr. Gao Pilin reply Ophthalmology

Hello, A: If wearing them feels uncomfortable, then they are not suitable contact lenses.
The values 43.5 and 40.75 refer to the refractive power, with 40.75 being flatter and having a lower refractive power.
The curvature of the eyeball can be measured during the refraction test, which should also assess the corneal curvature radius - base curve (BC) (e.g., 9.0mm) and refractive power (e.g., 40.75D).
If the cornea is too flat, it is not suitable to wear contact lenses, and there is no need to force yourself to wear them.

Reply Date: 2022/03/16

More Info

When it comes to choosing contact lenses for individuals with high corneal curvature, particularly those who have never worn contact lenses before, there are several important factors to consider. Your experience with discomfort while wearing daily disposable lenses indicates that the fit of the lenses may not be optimal for your eye shape.
Firstly, let's clarify some terminology. The "K value" that your eye doctor mentioned refers to the keratometry measurement, which assesses the curvature of the cornea. A typical K value for a normal cornea is around 43.5 diopters, while your measurement of 40.75 indicates that your cornea is flatter than average. This difference in curvature can significantly affect how contact lenses fit and feel on your eyes.

Contact lenses are designed with specific base curves (BC), which correspond to the curvature of the cornea. Most standard contact lenses have a base curve ranging from 8.5 to 8.7. Since you mentioned that you were prescribed a base curve of 9.0, it suggests that the lenses are designed for a flatter cornea. However, if your cornea is indeed flatter than the average, a base curve of 9.0 might not provide the best fit, leading to the discomfort you experienced, such as the sensation of having something in your eye or tightness.

The discomfort you described, particularly the feeling of tightness and foreign body sensation, is not typical for well-fitting contact lenses. Ideally, contact lenses should feel comfortable and should not cause any irritation or pain. If you experience persistent discomfort, it could be due to several factors, including:
1. Lens Fit: If the lens is too tight or too loose, it can cause discomfort. A lens that is too tight may restrict the natural movement of the eyelid, while a loose lens may not stay centered on the cornea.

2. Lens Material: Different contact lens materials have varying levels of oxygen permeability and moisture retention. If your lenses are not breathable or do not retain moisture well, they can lead to dryness and discomfort.

3. Dry Eyes: If you have underlying dry eye syndrome, wearing contact lenses can exacerbate the symptoms. It’s essential to ensure that your eyes are adequately lubricated before and during lens wear.

4. Wearing Time: Gradually increasing the wearing time of contact lenses is crucial, especially for new users. If you jumped from a few hours to 12 hours in a single day, your eyes may not have had enough time to adjust.

Given your situation, it may be beneficial to consult with your eye care professional about trying different lens options. You might consider:
- Custom Fitting: Some practitioners offer custom fitting services for contact lenses, which can provide a better fit for individuals with unique corneal shapes.

- Different Base Curves: Exploring lenses with a different base curve that better matches your corneal curvature could enhance comfort.

- Lens Types: There are various types of contact lenses available, including rigid gas permeable (RGP) lenses, which may provide better vision and comfort for individuals with high corneal curvature.

- Moisture-Rich Lenses: Consider lenses designed for dry eyes or those that retain moisture better, which can alleviate discomfort.

In summary, the discomfort you are experiencing is a signal that your current lenses may not be suitable for your eye shape. It is crucial to communicate these issues with your eye care provider, who can help you find the right lenses tailored to your specific needs. Regular follow-ups and adjustments are key to achieving a comfortable and effective contact lens experience.

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