Bad Glasses - 8 Hidden Flaws Draining Your Focus Reserve

(And the Fastest One You Can Fix Today)

Your screen is in focus. So why does it still feel like work to look at it?

If you're a designer, engineer, or anyone who spends 6+ hours a day locked onto a monitor, there's a good chance your glasses are quietly draining your mental energy.

We call it Focus Reserve: the visual "battery" that powers crisp, comfortable screen vision. When glasses are tuned for the wrong task — or built with tiny errors — that battery drains faster than it should.

Some flaws empty it in hours. Others chip away over time. But most of them are fixable once you know where to look.

Below, we’ll walk through eight hidden flaws that quietly wear down your screen stamina. They’re ordered by how aggressively they deplete your Focus Reserve. The first one is the biggest (and easiest to test today).

1. Your Glasses Are Missing a TaskAdd™ (Biggest Drain)

Most prescription glasses are tuned for distance vision — about 20 feet or more. But your screen sits much closer, typically 50–80 cm away.

That gap matters. Your eyes have to work to bridge it, even if you don’t consciously notice.

TaskAdd is our name for a small boost in lens power (+0.50 to +1.25 diopters) that shifts your glasses into the "computer zone."

Think of it like downshifting a bike when climbing a hill: less force, smoother motion.

Wait—what's a diopter?

A diopter (D) is how lens power is measured. Higher numbers mean stronger correction. Reading glasses usually add +1.00 to +2.50 D. Task-tuned lenses for screens typically need just +0.50 to +1.25 D.

Why this boost matters

Generic computer prescriptions often use age-based tables to assign this small boost (often called the "Add" in your Rx). But these methods miss the mark for many users. Research shows they can be off by up to ±0.75 D for real-world comfort (Goss 2016) — which can be the difference between all day comfort and eye strain.

And it's not just about clarity. Even a 0.50 D mismatch can increase the convergence demand on your eye muscles, leading to fatigue over the course of a day (Ciuffreda 2006).

Try it right now

• If you're nearsighted: Slide your glasses about 1 cm down your nose. This mimics a small TaskAdd.

• If you're farsighted or don’t wear glasses: Slide a +1.00 D reader over your normal glasses (you can get one at the drugstore).

If your monitor feels instantly easier to look at, you've found a likely leak.

The easiest fix

Our TaskAdd™ Trial Kit includes four lightweight test frames with small boosts. Try each one during your real workdays. Choose the one that makes your eyes feel calm. We'll turn it into a custom, optometrist-signed screen prescription.

Reserve Your Trial Kit

2. Your Pupillary Distance (PD) Is Off

Pupillary distance is the space between your pupils, measured in millimeters. It tells the lab where to center each lens. If it’s even 1 mm off, your eyes can start working against tiny amounts of unintended distortion.

This shows up as prismatic error: light no longer passes through the exact optical center of the lens, which can subtly shift the image your brain sees.

A 1 mm PD error in a ±4.00 D lens can introduce 0.67 prism diopters of unwanted deviation (Prentice Rule) — enough to cause low-grade blur, strain, and even headaches.

A better DIY check

Download the Warby Parker iOS app. It uses the front camera to estimate your PD and has been shown to achieve mean absolute error under 0.51 mm in recent testing (Han 2023).

If the number differs meaningfully from what’s listed on your last glasses order, that’s a likely source of strain.

3. Your Optical Center Height Was Never Set

Every lens has a vertical sweet spot too: the optical center height. That’s the point where light travels straight through without bending.

If your pupil doesn't line up vertically with that center, you get small shifts in how the lens behaves. That’s especially important for taller frames and for progressive lenses (which change power from top to bottom).

The catch

Most online glasses don't ask for this measurement. Unless you or your optician specified optical center height at order time, the lab probably just defaulted to placing it in the vertical middle of the lens.

That works for some faces and frame shapes—but not most.

DIY mirror check

Put on your glasses and stand in front of a mirror. Look straight ahead. Now look closely:

• Are your pupils sitting near the vertical center of the lens?

• Or noticeably above/below?

If you're not aligned, there's likely untapped clarity waiting for you. A properly adjusted OC can make a big difference in both single vision and progressive setups.

4. Your Frame Fit Shifts the Lens Too Far

The vertex distance is the gap between your eye and the lens surface. Even small shifts in this distance change how the lens power behaves—especially for higher prescriptions.

Every 2 mm increase in vertex distance reduces effective lens power by about 0.12 D at −4.00 D (Smith & Atchison 1997).

That might not sound like much. But combine it with a TaskAdd miss, and you’re now double-dipping into strain.

Common frame fit problems

• Slides down your nose: You lose optical center alignment and increase vertex distance

• Sits too far out: Power and angle of view change subtly

• Tilts too much: Causes localized blur or edge distortion

Easy home tweaks

Not a permanent solution, but can help restore alignment until you dial in a better fit.

5. You're Using Progressives for Desk Work

Progressive lenses combine multiple prescriptions in one lens, transitioning from distance at the top to reading at the bottom. They’re great for everyday life. But not for 8-hour desk work.

Why? Because the intermediate zone—where screens live—is tiny. Only about 15% of the lens corridor supports this range.

The result? Neck craning, chin lifting, or weird angles just to keep things sharp.

• One study found that progressive users doubled their neck flexion compared to single vision intermediate lenses during computer tasks (Weidling 2015).

Smarter alternatives

• Single vision screen lenses: One prescription, optimized for your desk distance.

• Occupational progressives: Wider midrange corridor, tuned for up-close and screen tasks, not driving.

Ask for them explicitly. Most opticians won’t bring it up unless you do.

6. Your Lenses Were Made Just a Bit Wrong

You might assume that if your Rx is right, your glasses will be too. But manufacturing tolerances exist—and cheap labs often blow past them.

ANSI Z80.1 allows a margin of error up to:

• ±0.12 D for spherical power

• ±0.13 D for cylinder power

In one study, 44.8% of online eyewear orders failed to meet even these modest thresholds (AOA/Vision Council 2011).

Translation

If your lenses are off by 0.25 D, they may still pass inspection—but you'll feel it.

7. Your Coatings and Lens Materials Aren't Doing Their Job

Not all lenses are created equal. The base material and the coatings determine how sharp, durable, and color-true your view is.

What to look for

• Abbe value ≥42: Lower values = more chromatic aberration (color fringing)

• Luminous transmission ≥95%: Lets most light through

• Durable hardcoat: Rated for 800+ Taber cycles

Be wary of blue-light coatings that prioritize color over clarity. They often tint the world without meaningfully improving comfort.

8. Your Lighting and Ergonomics Are Making Things Worse

Sometimes the problem isn’t your glasses — it’s everything around them.

Poor lighting and posture can take an already-strained system and push it over the edge.

Simple screen hygiene

• Top of your monitor = level with your eyebrows

• Ambient light: 500–700 lux, no overhead glare

• Follow the 20-20-20 rule: Every 20 minutes, look 20 feet away for 20 seconds (Rosenfield 2022).

Individually, these tweaks may seem minor. Together, they help you hold onto more Focus Reserve throughout the day.

5-Minute Focus Reserve Debug

Want to run a quick self-check? Try this:

1. TaskAdd feel test: Slide your glasses down / clip on +1.00 D

2. PD check: Use the Warby Parker app

3. OC alignment: Are your pupils vertically centered in the lens?

4. Frame fit: Is the lens distance and tilt optimal?

5. Monitor position: Top bezel at brow line

Ready to Find The Perfect Computer Prescription?

Reserve your TaskAdd™ Trial Kit. Test it during real workdays. Discover the small boost that unlocks all day comfort at the screen.

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