Complete Guide
Optical Terms Explained
The terms on your optometry report and the jargon of lens specifications — this page explains them one by one in plain language. Once you understand them, you can ask the right questions when choosing lenses.
- ✦The everyday Taiwanese "100 degrees" equals the "1.00 D (Diopter)" on an optometry report — the same thing written two ways.
- ✦Common fields on a report: SPH (sphere power), CYL (cylinder power), AXIS (cylinder axis), ADD (near add power), PD (pupillary distance).
- ✦You don't need to memorise all of these; understand the three keys — power, PD, refractive index — and you can ask the right questions when choosing lenses.
- ✦Refractive index, aspheric, coatings, blue light, polarized and photochromic are common lens-spec terms, each corresponding to a different optical principle and use.
Exam and Power Terms
Understanding your optometry report and what the optometrist is saying starts with these terms.
How Is Prescription "Power" Calculated? What 100 Degrees / 1.00D Actually Means
Why does Taiwan talk in "degrees" while a prescription slip reads "D"? What does 100 degrees = 1.00D actually mean? For anyone in Xinzhuang or Banqiao trying to read their own prescription, here's power explained in plain language.
Myopia vs. Astigmatism: What's the Difference? Causes and Terms Explained
Myopia and astigmatism are often lumped together, but they're two completely different refractive conditions. Many people in Xinzhuang and Banqiao assume astigmatism is just "worse myopia"—here's a clear breakdown of both.
Hyperopia vs. Presbyopia: What's the Difference? An Optometrist Explains Two Things People Often Confuse | Beyond Visual Optometry
Hyperopia and presbyopia both show up as a '+' on a prescription, and both make near vision harder — so a lot of people mix them up. But their causes are completely different. The team at Beyond Visual Optometry in Xinzhuang and Banqiao breaks it down in plain terms.
What Is Addition Power (ADD)? How to Read Your Presbyopia Prescription | Beyond Visual Optometry
The ADD on your prescription is the extra plus power added on top of your distance prescription, specifically for near vision. Beyond Visual Optometry (Xinzhuang and Banqiao) explains addition power in plain terms, and how to work out your near-vision prescription.
What Is 'Binocular Vision'? An Optometrist Explains How Your Two Eyes Team Up
We have two eyes, yet we see one single world with depth and dimension — that's binocular vision. Optometrists at Beyond Visual Optometry in Xinzhuang and Banqiao break down, in plain language, how your two eyes coordinate and the three levels behind it.
What Is Pupillary Distance (PD)? What Happens If It's Measured Wrong
Pupillary distance (PD) is the distance between the centers of your two pupils, and it determines where a lens's optical center needs to sit. Plenty of people in Xinzhuang and Banqiao focus only on the prescription and overlook it—here's PD explained clearly.
What Is Vertex Distance? Why It Matters for High Prescriptions
Vertex distance is that small gap between the lens and your eye, and the higher your prescription, the more it matters. High-prescription wearers in Xinzhuang and Banqiao often overlook this detail—here's a full explanation.
Vision Exam vs. Dispensing: What's the Difference? An Optometrist Explains Two Separate Steps
Getting a pair of glasses actually involves two distinct professional stages: the vision exam and dispensing. Getting the prescription right doesn't guarantee the glasses will feel right. Our optometrists at Beyond Visual Optometry (Xinzhuang and Banqiao) break down the difference.
Lens and Coating Terms
Refractive index, aspheric, coatings, blue light, polarized, photochromic — the principles behind the lens specs.
What Is Lens Refractive Index? What's the Difference Between 1.60, 1.67, and 1.74? | Beyond Visual Optometry
Refractive index determines how thick or thin a lens is — the higher the number, the thinner the lens. Here's a clear breakdown of everything from 1.50 to 1.74, so you understand this key term before your next fitting at our Xinzhuang or Banqiao store.
What Is an "Aspheric" Lens? How Is It Different From Spherical?
An aspheric lens has a surface curve that changes gradually, which makes the lens flatter and keeps peripheral vision more stable. Here's the plain-language difference between spherical, aspheric, and double-aspheric — worth understanding before you order glasses in Xinzhuang or Banqiao.
What Is the 'Corridor' in Progressive Multifocal Lenses?
The zone that connects "distance" and "near" vision on a progressive multifocal lens is called the corridor. Beyond Visual Optometry (Xinzhuang and Banqiao) breaks down the corridor's optical structure and why blur appears on either side of it.
How Anti-Reflective Coating Works: Why a Thin Film Stops Glare
Anti-reflective coating uses "light interference" to cancel out reflected light, which is what makes a lens look clear instead of glassy. A plain-language breakdown of the optics — worth understanding before you order lenses in Xinzhuang or Banqiao.
What Does a Blue Light Filter Lens Actually Filter? (Wavelength and Principle)
Blue light is the segment of visible light with a wavelength of roughly 400–500 nanometers. Blue light filter lenses reduce that segment through either "absorption" or "reflection." This article sticks strictly to the optics — worth knowing before you order glasses in Xinzhuang or Banqiao.
Why Do Photochromic Lenses Change Color? The Chemistry Behind Photochromic Molecules
Photochromic lenses darken outdoors and fade back to clear indoors, thanks to molecules that change structure when they hit UV light. Beyond Visual Optometry (Xinzhuang and Banqiao) breaks down this reversible chemical reaction in plain language.
The Physics of Polarized Lenses: How Do They Filter Out Glare From Water?
Polarized lenses cut glare off water not because they're "darker," but because of a film that selectively blocks light based on its direction of vibration. Beyond Visual Optometry (Xinzhuang and Banqiao) breaks down the physics in plain language.
Frequently Asked Questions
Q: Is it normal not to understand all the letters and numbers on an optometry report?
Completely normal. SPH, CYL, AXIS, ADD and PD on the report each stand for a different measurement, and most people were never taught them. This glossary breaks each term down in plain language — understanding them lets you ask the right questions when choosing lenses and know exactly what you're getting. For anything still unclear, you're welcome to have an optometrist explain it in person at the store.
Q: Is the "degree" people talk about in Taiwan the same as the "D" on an optometry report?
They're the same thing written two ways. In everyday Taiwanese speech people say "100 degrees," while the international optometry unit is written "1.00 D (Diopter)" — 100 degrees equals 1.00 D. For the detailed conversion and what the plus/minus signs mean, see the article "How diopter power is calculated."
Q: Do I really have to understand all of these terms?
No. This glossary is a reference for those who want to know more — it's not a test. When you actually get glasses, the optometrist will do a full measurement and explanation based on your situation; reading a few key terms first (power, PD, refractive index) simply makes the conversation smoother.
Still have a term to ask about?
For any optometry report you can't read or term you don't follow, you're welcome to book a vision consultation and have Optometrist YoYo explain it in person. Appointments available at the Xinzhuang and Banqiao stores.
Book a Vision Consultation →