Understanding Your Eyeglass Prescription
What Information Appears on Your Eyeglass Prescription
Your prescription contains several key measurements that work together to create lenses perfectly matched to your vision needs. Each value has a specific purpose in helping you see clearly and comfortably.
The sphere value, often written as SPH, shows the main lens power needed to correct your nearsightedness or farsightedness. A minus sign means you are nearsighted and need help seeing things far away, while a plus sign means you are farsighted and need help with close-up vision. This number is measured in diopters, which describe how much the lens bends light to help you see clearly.
The cylinder and axis values work together to correct astigmatism, which happens when your cornea has an irregular shape. The cylinder, or CYL, measures how much astigmatism correction you need, and the axis tells us the direction or angle where that correction should be placed in your lens. Our ophthalmologists at ReFocus Eye Health Penndel use advanced diagnostic equipment to measure these values with great precision during your exam.
Add power, sometimes labeled as ADD, shows the extra magnifying strength needed in the bottom part of bifocal or progressive lenses. This measurement only appears on prescriptions for people who need help with near vision, which is common after age 40 due to a natural condition called presbyopia. The add power is always a positive number and usually ranges from about 0.75 to 3.00 diopters.
We add this value to your distance prescription to create the proper strength for reading and close work. Both eyes typically have the same add power, even if your distance prescriptions are different.
Pupillary distance, or PD, measures the space between the centers of your pupils in millimeters. This measurement helps the optical center of each lens line up with your pupils, which supports clear vision and comfort. Your PD usually stays the same throughout your adult life unless you have certain medical conditions.
- A single PD number applies to both eyes together and typically ranges from 54 to 74 millimeters for adults
- Dual PD measurements give separate numbers for each eye from the bridge of your nose
- Children typically have smaller PD measurements between 43 and 58 millimeters that grow as they age
- Distance PD is larger than near PD, with near PD usually 2 to 4 millimeters smaller in total due to how your eyes converge when focusing up close
- For bifocals, trifocals, and progressives, our optical team also measures segment height or fitting height for each eye to ensure proper lens positioning
Prism correction helps when your eyes do not work together properly, a condition we call eye misalignment. The prism value shows how much the lens needs to shift the image so both eyes can focus on the same spot. Not everyone needs prism in their glasses, and this section may be blank on your prescription if your eyes align normally.
When prism is needed, we record the amount in prism diopters along with the base direction, such as base up, base down, base in, or base out. Prism can address alignment problems that cause double vision or eye strain, conditions that our ophthalmologists can diagnose and treat as part of your comprehensive eye care.
Your prescription includes the date when it was written and an expiration date, which is usually one to two years later depending on your state laws and individual needs. The expiration date exists because your vision can change over time, and we want to make sure you always have the most accurate correction. Using an outdated prescription may mean you are not seeing as clearly as you could, or it might cause headaches and eye fatigue.
Some prescriptions expire sooner if you have certain eye conditions like glaucoma, diabetic eye disease, or macular degeneration. Our ophthalmologists will let you know during your exam if you need more frequent updates to your prescription based on your specific eye health needs.
How to Read the Numbers on Your Prescription
Understanding what each number means helps you see how your prescription corrects your vision. The values on your prescription follow standard formats used throughout the eye care industry.
The plus and minus signs before the numbers tell us whether the lens needs to make things look bigger or smaller. A minus sign indicates a concave lens that helps with nearsightedness by making distant objects clearer. A plus sign means you need a convex lens for farsightedness, which helps you see nearby objects better.
The larger the number after the sign, the stronger your prescription is. For example, a minus 5.00 is a stronger correction for nearsightedness than a minus 2.00, meaning you need more help seeing things at a distance.
If you have astigmatism, you will see numbers in both the cylinder and axis columns of your prescription. The cylinder number can be written as either a minus or plus value, but it always corrects the same problem, which is the uneven curvature of your cornea or lens. Both minus-cylinder and plus-cylinder formats are used and they are mathematically equivalent.
- Cylinder values typically range from 0.25 to 4.00 diopters or higher
- Low astigmatism is usually 1.00 diopter or less
- Moderate astigmatism falls between 1.00 and 2.00 diopters
- High astigmatism is anything above 2.00 diopters and may benefit from specialized lens designs
The axis number can range from 1 to 180 degrees and shows the orientation of your astigmatism. Think of it like the hands on a clock, with the number telling us where to position the astigmatism correction in your lens. This number is very specific because even a small change in the axis can make your vision blurry or uncomfortable.
The axis always pairs with a cylinder measurement. If your prescription shows no cylinder value, then there will be no axis number either, since you do not have astigmatism that needs correction.
The add power appears as a separate number on your prescription when you need extra help for reading and close-up tasks. We measure the add power as a positive number that gets combined with your distance prescription to create the near vision portion of your multifocal lenses. For progressive lenses, this add power is smoothly blended through the lens from distance to near.
Your add power typically increases gradually as you get older because the lens inside your eye becomes less flexible with age. This natural change, called presbyopia, affects almost everyone starting in their early to mid 40s.
Different Types of Vision Prescriptions
At ReFocus Eye Health Penndel, we write prescriptions for different types of lenses based on your vision needs, lifestyle, and the tasks you perform daily. Understanding these options helps you choose the right eyewear.
Single vision prescriptions correct your sight at one distance only, either far away or up close. Most people who need glasses before age 40 have single vision prescriptions because their eyes can still focus naturally at different distances. These prescriptions are the simplest type and work well if you only need help with one specific task, like driving or reading.
- Distance single vision helps you see clearly far away for activities like driving or watching television
- Near single vision is designed only for reading and close work
- Computer single vision can be set for intermediate distances to reduce eye strain during screen time
Bifocal prescriptions combine two different powers in one lens, with the top part for distance vision and a visible segment at the bottom for near vision. The line between these sections is easy to see, and you learn to look through the right part depending on what you are viewing. Trifocal lenses add a third section in the middle for intermediate distances like computer screens.
These traditional multifocal designs work well for many people, though some prefer the seamless appearance of progressive lenses. Bifocals and trifocals are still commonly prescribed when patients want a simple, proven solution or when they have tried progressives without success.
Progressive lens prescriptions provide a smooth transition between distance, intermediate, and near vision without any visible lines. The power gradually changes from top to bottom, letting you see clearly at all distances by simply adjusting where you look through the lens. Many of our patients in Penndel, Levittown, Bensalem, and Bristol prefer progressives because they look like regular single vision glasses and provide more natural vision at all distances.
Your prescription for progressives is the same as for bifocals, but our optical team may recommend specific progressive lens designs based on your lifestyle and how you use your eyes. Learning to use progressives takes a few days to a week as you get used to finding the right spot in the lens for each task.
Contact lens prescriptions include different measurements than eyeglass prescriptions because the lenses sit directly on your eye instead of about 12 millimeters away. We must account for this distance difference, which is called vertex distance, especially for stronger prescriptions. Contact prescriptions also include the base curve and diameter of the lens, which tells us the shape and size that will fit your eye comfortably.
- Contact lens powers may differ from glasses powers due to vertex distance
- Base curve affects how the lens sits on your cornea
- Diameter measurements ensure proper lens coverage and comfort
- Brand specifications matter because different lenses fit differently
- You need a separate fitting appointment even if you know your glasses prescription
Some people only need vision correction for close-up work and have perfect distance vision naturally. For these patients, we write a reading-only prescription that just includes the near power without any distance correction. These glasses are meant to be taken on and off as needed rather than worn all day.
Reading-only prescriptions are common for people in their 40s and early 50s who are just starting to develop presbyopia but do not need any distance correction yet. Over time, you might need a full multifocal prescription as your near vision needs increase or your distance vision changes.
The Eye Exam That Creates Your Prescription
At ReFocus Eye Health Penndel, our comprehensive eye exams go beyond just determining your prescription. We use advanced diagnostic technology to assess your overall eye health while measuring your vision needs with precision.
We start your exam by testing your visual acuity, which means measuring how well you can see at different distances using an eye chart. This gives us a baseline and helps us understand what corrections might improve your vision. The refraction part of the exam is where we determine your exact prescription by having you look through different lenses until we find the combination that gives you the clearest sight.
During refraction, we carefully measure how light bends as it enters your eye and where it focuses. Our ophthalmologists and optometrists adjust lenses until the light focuses precisely on your retina, which creates sharp, clear vision instead of the blur you might experience without correction.
The phoropter is the large instrument that we position in front of your face, and it holds many different lenses that we can quickly switch while you tell us what looks clearer. When we ask which option is better, we are comparing two slightly different lens choices to narrow down your exact prescription. Your answers help us fine-tune each part of your prescription to give you the best possible vision.
- We test each eye separately and then together to assess binocular vision
- The process usually takes 10 to 15 minutes depending on your prescription complexity
- There are no wrong answers during this test, so respond based on what looks clearest to you
- We repeat certain comparisons to confirm accuracy and ensure consistency
Before we start the detailed phoropter testing, we often use an autorefractor machine that quickly estimates your prescription while you look at an image that moves in and out of focus. This automated reading gives us a helpful starting point, though we always refine it with manual testing. Retinoscopy is another technique where we shine a light into your eye and watch how it reflects off your retina to estimate your prescription objectively.
These preliminary measurements are especially useful for young children or anyone who cannot reliably provide subjective responses during the exam. The combination of automated and manual testing helps us achieve an accurate prescription efficiently.
If you want contact lenses, we perform extra measurements beyond the standard eye exam. We measure the curvature of your cornea using a keratometer or corneal topographer, which maps the exact shape of the front surface of your eye. We also evaluate your tear film to make sure you produce enough moisture to wear contacts comfortably and check the health of your cornea under magnification.
After taking these measurements, we select trial lenses for you to try so we can see how they fit and move on your eye. We evaluate the fit, check your vision with the trial lenses, and make any needed adjustments before finalizing your contact lens prescription. Our contact lens services include options for patients with astigmatism, presbyopia, dry eye, and keratoconus.
When You Need a New or Updated Prescription
Knowing when to schedule your next eye exam helps you maintain clear, comfortable vision and protects your long-term eye health. We monitor changes in your vision and overall eye health during every visit.
If you notice that you are squinting more often, having trouble reading street signs, or experiencing frequent headaches, your prescription may no longer be strong enough. Blurry vision that comes on gradually is one of the most common signs that your eyes have changed and need a new correction. Eye strain or fatigue during activities that used to be comfortable also suggests your current lenses are not meeting your needs anymore.
- Words on screens or in books appear fuzzy even with your glasses on
- You hold reading material closer or farther away than before
- Halos or glare around lights seem worse than usual, especially when driving at night
- Your eyes feel tired after normal daily activities like reading or computer work
While most prescription changes happen slowly over months or years, sudden vision changes need immediate medical attention. If you experience a rapid loss of vision, new floaters or flashes of light, a curtain or shadow in your field of view, or sudden double vision, contact ReFocus Eye Health Penndel right away. These symptoms could indicate serious problems like retinal detachment, stroke, or other conditions that need urgent treatment from our ophthalmologists.
Sudden pain combined with vision loss, severe redness, or seeing halos around lights can also signal acute problems such as angle-closure glaucoma. Our ophthalmologists are experienced in diagnosing and managing eye emergencies for patients throughout Bucks County and the Greater Philadelphia Metropolitan Area.
Most adults with healthy eyes should have comprehensive eye exams every one to two years, depending on their age and risk factors. If you wear glasses or contacts, have a family history of eye disease, or have health conditions like diabetes, we recommend annual exams. Children need their first eye exam around six months of age, another at age three, and then before starting school, with regular exams every year or two after that as recommended.
Regular exams catch prescription changes early and also detect eye diseases like glaucoma, cataracts, and macular degeneration before they cause symptoms. Following your recommended exam schedule helps protect your vision and overall eye health throughout your life.
Your vision needs change predictably as you age, which is why we monitor your prescription over time. Most people develop presbyopia between ages 40 and 50, when the lens inside your eye loses flexibility and you need reading help. Your prescription may stabilize during your 20s and 30s, change more rapidly during childhood and teenage years, and require adjustments again after age 60 as the natural aging process affects your eyes.
These age-related changes are completely normal and happen to almost everyone. Updating your prescription as needed helps you maintain clear, comfortable vision at every stage of life.
If you have eye surgery such as cataract removal, our ophthalmologists will write you a new prescription after your eyes heal. The healing period varies depending on the procedure, but we typically wait several weeks to a few months before finalizing your updated prescription. New medical diagnoses like diabetes or neurological conditions can also affect your vision and may require prescription updates or more frequent monitoring.
Always let us know about any surgeries or new health conditions so we can adjust your care plan. Our ophthalmologists coordinate with your other doctors when needed to ensure your prescription supports both your vision and your overall health.
Using Your Prescription to Order Eyewear
Once you receive your prescription, you have several options for ordering glasses or contact lenses. Our optical shop at ReFocus Eye Health Penndel offers personalized service to help you find eyewear that fits your lifestyle and budget.
When you order glasses, our optical team needs your complete prescription including all the numbers we discussed earlier, along with information about how you plan to use your glasses. Your pupillary distance is essential for proper lens alignment, and we also consider your frame choice since different frame sizes and styles work better with certain prescriptions. Let our opticians know about your daily activities, hobbies, and any vision challenges you face so we can recommend the best lens options.
- Your full written prescription with all sphere, cylinder, axis, and add values
- PD measurement, which we provide and keep on file for your convenience
- The frame you have chosen or help selecting frames that suit your face shape and prescription
- Your budget and insurance coverage details so we can maximize your benefits
Federal law requires that we provide you with a copy of your prescription after your exam, and you have the right to use it to order glasses or contacts from any seller you choose. When ordering eyewear online, you must enter your prescription information exactly as written, including all plus and minus signs and axis measurements. Online retailers cannot fill your order without a valid, current prescription, and they may contact our office to verify the information you provided.
Make sure your prescription has not expired before placing an order online. If your PD is not included on your written prescription, contact our office and we will provide this measurement for you.
Your prescription tells us what power you need, but you also get to choose lens materials and coatings that affect how well your glasses work for you. High-index plastic lenses are thinner and lighter than standard plastic, which matters more if you have a strong prescription. Polycarbonate and Trivex materials offer excellent impact resistance and are recommended for children, active adults, and anyone who needs safety glasses.
We recommend anti-reflective coating to reduce glare from screens and oncoming headlights, scratch-resistant coating to protect your lenses, and ultraviolet protection to shield your eyes from sun damage. Blue light filtering coatings are also available for people who spend long hours on digital devices.
Getting a contact lens prescription requires a fitting appointment in addition to your regular eye exam. Even if you already wear glasses successfully, we must evaluate how contacts will fit your specific eye shape and ensure they are safe and comfortable for you. During the fitting, we measure your corneal curvature, assess your tear quality, and have you try sample lenses to confirm the right fit.
If you have worn the same contact lens brand for years, you still need periodic fittings to make sure your eyes remain healthy and the fit is still appropriate. New contact lens technologies become available regularly, and we want to make sure you have access to the most comfortable, healthy options for your eyes.
Frequently Asked Questions
We answer common questions about eyeglass prescriptions to help you feel confident understanding and using your prescription.
Contact lenses sit directly on your cornea while glasses sit about 12 millimeters away from your eyes, so we must adjust the power to account for this difference called vertex distance. The closer the lens is to your eye, the less power is needed for stronger prescriptions, which is why your contact lens prescription may have smaller numbers than your glasses prescription even though they correct the same vision problem.
Most optical shops and online retailers will not fill an expired prescription because laws in many states prohibit it and because your vision may have changed since the prescription was written. Using an outdated prescription can result in eyewear that does not correct your vision properly, leading to eye strain, headaches, and difficulty with daily tasks, so we always recommend getting a current exam and prescription.
Higher numbers on your prescription do mean you need stronger lenses to see clearly, but they do not necessarily indicate disease or poor eye health. The numbers simply describe how much correction you need to focus light properly on your retina, and people with high prescriptions can achieve excellent vision with the right lenses just like those with low prescriptions.
Your prescription may change from year to year, especially during childhood and adolescence when eyes are still growing, or after age 40 when presbyopia develops. However, many adults find their prescriptions stay stable for several years at a time, and prescription changes are not always in the direction of getting stronger, as some people experience shifts in type of correction rather than just increasing strength.
You should never share glasses or use someone else's prescription because even small differences in prescription values can cause eye strain, headaches, and blurred vision. Your prescription is customized to your unique eyes, including measurements like pupillary distance that are specific to you, so glasses made for someone else will not align properly with your eyes even if the powers seem similar.
Regular eye exams do more than just update your prescription, as they also check for eye diseases like glaucoma, cataracts, and macular degeneration that often have no symptoms in their early stages. Many serious eye conditions can be treated more successfully when caught early through comprehensive exams with our ophthalmologists, who evaluate your overall eye health, screen for systemic diseases that show signs in the eyes, and ensure your current prescription is still optimal even if your vision seems unchanged.
Getting Help with Your Prescription at ReFocus Eye Health Penndel
We understand that eyeglass prescriptions can look confusing at first glance, but our team at ReFocus Eye Health Penndel is always here to explain what your numbers mean and answer any questions you have. Whether you visit us in Penndel or travel from nearby communities in Montgomery County or Burlington County, New Jersey, you will receive the same personalized attention and expert care. Your prescription is an important tool for maintaining clear vision and healthy eyes, and we want you to feel confident using it to get the eyewear that works best for your lifestyle.
First visit with Dr. Soll. My doctor of 30 yrs retired, was apprehensive. Everyone was great! Dr. Soll thorough, explained everything. Very pleased with my new doctor.
Susan Deaton
Dr. Amin performed cataract surgery on both my eyes. It was a wonderful experience for me. The entire staff that I met at Refocus Eye were the best.
George Ruoss
Got eye exam at Refocus. Waited a little. Lady at window polite, Dr. Bano polite, courteous, listened. I recommend this place. Thank you.
Jackie Baldridge
Great staff, insurance covered exam. Doctor Bano gave comprehensive exam, recommendations. Thanks for today’s service 😁 Doctor super with cataract surgery. Very pleased with outcome.
Al Mitchell
Dr. Amin is knowledgeable, kind, and sympathetic. She listens carefully and provides excellent care. Truly a wonderful doctor who makes patients feel valued and understood. Highly recommend!
Sarah Magee
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