Why Does My Contact Lens Prescription Look Different from My Glasses?


When you receive a prescription for contact lenses and glasses, you may notice that the numbers don’t match. This often leads to confusion and concern—are you being prescribed the correct power? Will you see as clearly in your contacts as you do in your glasses?

At Harmony Vision Optometry and Vision Therapy Clinic, we get this question frequently. The answer lies in the fundamental differences between how glasses and contact lenses work. While both aim to correct your vision, the way they interact with your eyes leads to differences in prescription values.

In this blog, we’ll break down why your prescriptions differ and help you understand how your optometrist ensures you get the best vision possible—whether you wear glasses, contact lenses, or both.

Different Numbers, Same Outcome

To illustrate this, let’s look at an example:

Imagine you have a high minus prescription of -6.50 diopters in glasses. When you switch to contact lenses, your prescription might change to -6.00 diopters. This discrepancy might seem alarming, but rest assured—it’s completely normal. The numbers may be different, but the effective correction remains the same.

Understanding Vertex Distance

One of the main reasons for this difference is vertex distance—the space between the back of your glasses lens and the front of your eye.

  • Glasses sit in front of your eyes (typically 8-14mm away), which means light bends slightly differently before reaching your eye.
  • Contact lenses sit directly on your eye, eliminating this distance.

For higher prescriptions (usually above ±3.50 diopters), this vertex distance significantly affects the effective power of the lens. Optometrists make adjustments to account for this, ensuring that the prescription you receive in contacts provides the same level of clarity as your glasses.

Other Differences in Contact Lens Prescriptions

Beyond the numbers, contact lens prescriptions contain other critical specifications that don’t appear in glasses prescriptions:

  • Lens Diameter & Base Curve: These measurements ensure the lens fits properly on your cornea.
  • Lens Material & Brand: Different brands have different oxygen permeability, comfort levels, and moisture retention.
  • Astigmatism Adjustments: If you have astigmatism, toric contact lenses have specific axis measurements that may slightly differ from your glasses.

Presbyopia: Glasses vs. Contact Lenses

If you’re over 40, you may be dealing with presbyopia, where near vision starts to decline.

  • Glasses often include a "near addition" power, increasing in strength as you look down through progressive lenses.
  • Multifocal contact lenses work differently—they incorporate both distance and near prescriptions within the same lens, requiring your brain to adapt to selectively focusing at different distances.

Because of this, contact lens prescriptions may not specify a precise "add power" like glasses do. Instead, they are categorized as Low, Medium, or High Add depending on your vision needs.

Astigmatism & Toric Contact Lenses

Astigmatism occurs when the eye is shaped more like a rugby ball rather than a soccer ball, leading to different curvatures that need correction.

  • In glasses, astigmatism is corrected using cylinder power and axis—precise numbers down to a single degree.
  • In contact lenses, manufacturers offer fewer options (typically in 10-degree steps) and limited cylinder powers. If your exact prescription isn’t available, optometrists adjust your lens power to provide the best possible clarity.
  • Additionally, toric contact lenses can rotate on the eye, requiring adjustments to ensure stability and proper vision correction.

These small changes might make your contact lens prescription look different, but they are carefully calculated to give you the best vision possible.

Trust Your Optometrist

At the end of the day, the differences between your glasses and contact lens prescriptions are just optical adjustments to ensure that your vision is as sharp and comfortable as possible.

✔️ The numbers may look different, but the visual outcome remains the same.
✔️ Contact lenses require additional fitting considerations that glasses don’t.
✔️ Adjustments for vertex distance, astigmatism, and presbyopia explain why your prescriptions aren’t identical.

If you have any further questions or need personalized advice about your prescription, feel free to contact us at Harmony Vision Optometry. Our team is happy to help you achieve clear, comfortable vision—whether you wear glasses, contacts, or both!

What is Binocular Vision Dysfunction?

Understanding Binocular Vision Dysfunction: What You Need to Know

 In this article, we'll shed light on what binocular vision dysfunction is, its symptoms, and how our experienced optometrists can help you overcome it for clearer, more comfortable vision.

What is Binocular Vision Dysfunction?

Binocular vision dysfunction, often referred to as BVD, is a condition where both eyes don't work together as a team as they should. Our eyes are designed to work in harmony, allowing us to see a single, clear image. When this coordination breaks down, it can lead to a range of visual discomfort and challenges.

Common Symptoms of Binocular Vision Dysfunction:

  1. Eye Strain and Fatigue: Individuals with BVD often experience eye strain, headaches, and fatigue, particularly when reading or performing close-up tasks for extended periods.
  2. Depth Perception Problems: Reduced depth perception can lead to difficulties with judging distances, making activities like catching a ball or parking a car more challenging.
  3. Poor Concentration: BVD can impact concentration and the ability to maintain attention, especially during tasks that demand visual focus.
  4. Frequent Loss of Place While Reading: Reading can become frustrating when the eyes don't work together, causing words to appear to jump around or lose their place on the page.
  5. Light Sensitivity: Some people with BVD may also experience increased sensitivity to light, known as photophobia.

How Can We Help?

Our experienced optometrists are highly trained to diagnose and treat binocular vision dysfunction. Through a comprehensive eye examination, we can identify the underlying issues causing your discomfort. Treatment options may include:

  1. Prescription Lenses: In some cases, specially designed eyeglasses or contact lenses can help improve binocular vision and reduce symptoms.
  2. Vision Therapy: Vision therapy exercises and activities can be tailored to retrain and strengthen neuro-muscular function, enhancing binocular vision and visual comfort.
  3. Lifestyle Adjustments: Our optometrists can also provide guidance on ergonomic changes and habits that can reduce eye strain and discomfort in your daily life.

Conclusion:

If you're experiencing any of the symptoms mentioned above, it's essential to schedule an appointment with our skilled optometrists. We are dedicated to improving your vision and overall eye health, helping you enjoy clear, comfortable, and seamless binocular vision once again. Don't let binocular vision dysfunction hold you back from living life to the fullest. Contact us today to schedule a consultation and take the first step toward better vision.

Myopia Awareness Week 22-26 May 2023

Myopia control is important because it allows parents to take proactive steps in managing and slowing down the progression of their child's shortsight. By working with the Optometrists at Harmony Vision to implement myopia control measures, parents can be assured that they are helping to take control of their child's eye health journey.

Why is this important?

Well, by actively addressing and controlling myopia, we can potentially reduce the risk of future eye problems for children, such as retinal detachment, cataracts, and glaucoma. It's our responsibility to safeguard our child's eyes for a healthier future.

Furthermore, myopia control has a significant impact on children’s daily life. By managing the progression of myopia, we can help our children maintain clearer vision without constantly needing stronger glasses or contact lenses. This empowers them to fully engage in activities, excel academically, and enjoy hobbies with improved visual clarity.

To achieve myopia control for your child, you can work with the Optometrists at Harmony Vision who will guide you in choosing the right strategies. This may involve specific glasses or contact lenses, eye drops, encouraging outdoor activities, and managing screen time effectively.

As parents, we have the opportunity to be the driving force in our child's eye health journey. By embracing myopia control, we actively shape the outcome of our child's vision and overall well-being. This requires a dedicated and proactive approach together with Harmony Vision to contribute to a brighter future for your child's eyes.

How Do You Get Myopia Management?

We assess your child's vision and axial length and consider other risk factors like age, family history, current level of myopia and lifestyle to develop an individual plan for managing your child's myopia.

To find out more call 07 5520 5900 or book online.




Children’s Vision – Chat to Your Teacher

The importance of talking with teachers to identify vision issues

A child’s ability to learn is intimately related to their vision. At school, 80% percent of what your child will learn is obtained visually. Think about it, most of their learning happens in front of a whiteboard, computer or book. How the brain and eyes work together has a tremendous impact on the learning process.

Why is vision so essential to learning?

In school, your child will be using a wide range of visual skills including:

  • Distance vision: being able to see the board
  • Near vision: being able to look at the words in a book without effort
  • Focusing flexibility: being able to maintain clear vision while shifting focus from a distant object to a near one
  • Tracking/eye movement skills: being able to aim both eyes accurately and move smoothly across a line of print or from object to object with ease
  • Eye-hand coordination: being able to use their eyes to guide the hands
  • Eye teaming: being able to coordinate the two eyes together so that they are precisely directed at the same object at the same time
  • Eye focusing: maintaining, for long periods of time, completely clear vision while looking at near or distant objects

Common symptoms that get overlooked

Many children suffer hidden vision problems because there is a misunderstanding that good vision is the same as clear sight. But it’s not.  Children won’t necessarily know or tell you if something is wrong with their eyesight, so don’t assume everything is normal.

Some of the most common signs that are often overlooked are:

 

  • Headaches or sore eyes
  • Slow reading
  • Blurred vision
  • Rereading a lot or forgetting what you’ve read
  • Poor comprehension
  • Tired, itchy or watery eyes
  • Concentration problems
  • Tiredness after computer work or reading
  • Poor depth judgment
  • Difficulties with 3D vision
  • Behavioural changes

While it’s recommended that a child’s eyes be checked at least every two years, if your child is showing these signs they should be tested immediately.

The need for regularly communicating with teachers

Given teachers see your children day after day, during extended periods of work, they are most likely to recognise symptoms before you would. With this in mind, it is vital as a parent to maintain regular communication with your child’s teacher to make sure issues are picked up sooner rather than later.

Don’t feel you need to wait for school parent-teacher nights though, here is a list of questions you can choose from to ask your child’s teacher during brief chats at school drop off or pick-up times.

  • How is my child performing at school?
  • Do you find he/she loses concentration or gets easily distracted?
  • Is he/she picking up the information as fast as he/she should? Or is he/she falling behind?
  • How is his/her comprehension?
  • Does he/she rub his/her eyes a lot through class?
  • Does he/she skip words, squint or close one eye when he/she is reading?
  • Does he/she play up at school when there is work to be done?
  • Does he/she try to avoid doing work?
  • Does he/she complain of headaches, aches around their eyes, dizziness or nausea?
  • Does he/she complain of itching or burning sensations in their eyes or excessive tearing?
  • Does he/she look overly tired, or get red or irritated eyes?

Often just by initiating these types of questions, you might spark a teacher to realise they have been seeing these signs or symptoms but not recognised it could be something more.

Concerned in any way? Arrange a time to come in so we can help you rule our or identify vision problems that might be affecting your child’s learning. Call 07 5520 5900

How much do you know about children's vision? Test your knowledge !

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