New · A Digital Optometry Solutions product

How thick, how heavy — before you order.

ThinCheck estimates the centre and edge thickness and the weight of both lenses in the frame your patient has chosen, in CR-39, 1.60, 1.67 and 1.74 side by side, and draws them to scale — from the front, from above and in 3D. The conversation about thinner lenses starts from their own prescription.

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Three sample prescriptions and four sample patients — no sign-up.

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lens materials,
side by side

frame shapes,
to the frame's size

and printed,
for the patient

Right lens · thickness comparison −6.75 / −1.25

CR-39 1.4911.5 mm · 12.1 g

1.60 · 9.0 mm22% thinner

1.67 · 7.8 mm32% thinner

1.74 · 7.0 mm39% thinner

Show the patient →

ThinCheck · lens preview 1.60 MR-8

Watercolour illustration of a spectacle lens showing index markings and cross-section

🔍 CR-39 🔍 1.60 🔍 1.67 🔍 1.74

Select a material to compare

9.0 mm edge

thickest edge vs CR-39 baseline

What it does

The lens they're buying, before it's made

Type the spectacle prescription, set up the frame, and ThinCheck works out every point of both lenses from the curves of their surfaces — so cylinder and axis count, not just the sphere.

Materials

Four materials, one lens

CR-39, 1.60, 1.67 and 1.74 compared on the same prescription and frame — the thickest edge and the weight of each, and how much thinner and lighter each one is than standard plastic.

Frame

The frame they've chosen

Eleven shapes, from rectangle and round to cat-eye, aviator and browline, each filling the frame's own eye size, depth and bridge. Full rim, semi-rimless or rimless.

Fit

Where the optical centre sits

Monocular PDs and heights decentre each lens, for single vision, flat-top bifocals and progressives — so the thick edge lands where it really will.

Plus lenses

Stock, surfaced or knife-edge

For plus lenses, see how much thinner at the centre a lens surfaced to the frame comes out than a stock lens, and what a knife-edge finish does in a full rim.

Blanks

A blank that covers the frame

Set the blank size from 55 to 80 mm. ThinCheck says when a blank doesn't cover the frame at this PD, and gives the smallest one that does.

Your lab

Your lab's figures

Every estimate starts from typical lab minimums, clearly labelled as assumed. Change them to match your own lab, and type the centre thickness from the lab's ticket when you have it.

Straight from the product

The actual drawings, not an artist's impression

Everything below is drawn exactly as ThinCheck draws it, from its demo prescription: R −6.75 / −1.25 × 170, L −6.25 / −1.00 × 8, in a rectangular 52□18 frame, PDs 31 and 31. Teal is the right lens, orange the left.

From the front

The frame to scale. The cross is each lens's optical centre, the dashed circle the blank, and the dot the thickest point of the edge, with its thickness in millimetres.

To scale

From above, cut through the centre

The same pair of lenses in two materials, true to scale. The numbers are the edge and centre thicknesses in millimetres. This is the picture that goes on the patient's printout.

39% thinner in 1.74

Standard CR-39 plastic

1.74 high-index

The right lens in each material

Thickest point and weight, worked out for the same frame and fitting. Tap a material in ThinCheck and every drawing redraws.

CR-39 1.4911.5 mm · 12.1 gthe standard

1.609.0 mm · 9.4 g22% thinner, 23% lighter

1.677.8 mm · 8.6 g32% thinner, 29% lighter

1.747.0 mm · 8.5 g39% thinner, 30% lighter

Estimates from typical lab figures. ThinCheck says so on screen, takes your lab's own figures, and leaves out prescribed prism, the prism thinning labs use on progressives, aspheric designs and coatings — the lab's ticket is the final word.

At the dispensing table

"Will they be thick?" — now you can show them

Tick one box and ThinCheck adds a card written for the patient: their new lenses in plain words, the drawing from above, and a 3D view they can turn. Show it on screen, or print it with your practice's name on it.

An estimate, and it says so

The centre thickness is labelled as assumed until you enter your lab's figure, and every screen and printout calls the figures estimates. Choosing the lens stays with you and your lab.

Nothing about the patient is stored

ThinCheck is a calculator. Prescriptions, frames and PDs stay on the screen and are gone when you close it — only your practice's lab figures are saved.

Works with the Prescription Visualizer

Already on file? Don't type it twice.

The Prescription Visualizer comes free with ThinCheck. When a patient is already in it, open their latest spectacle prescription, or an earlier one, straight into ThinCheck. It shows the prescription on screen and keeps no copy.

See the Visualizer →

Open from the Prescription Visualizer

Johan van der Merwe · V-0381Selected

27 January 2025 (latest)R +4.00 / −0.50 × 90 · add +2.50

9 June 2021R +3.50 / −0.50 × 90 · add +2.25

Use this prescription →

Pricing

One plan. No surprises.

14-day free trial

R199 per practice / month

Free for 14 days, then billed monthly in Rand through PayFast. Cancel any time from your Account page — your lab's figures are kept.

Lens thickness and weight for any spectacle prescription
CR-39, 1.60, 1.67 and 1.74 compared on every lens
Eleven frame shapes; full rim, semi-rimless and rimless
Stock, surfaced and knife-edge plus lenses; blanks from 55 to 80 mm
Drawings to scale, the 3D view and a printable patient card
Your lab's figures, set once for the whole practice
A login for every team member
The Prescription Visualizer — free with any subscription, and ThinCheck opens its prescriptions
Email support from the founder

Start your free trial → Explore the demo

Sample prescriptions and sample patients, no sign-up.

FAQ

Common questions

How close are the estimates?

ThinCheck works from the exact curves of both surfaces, so cylinder and axis are included, with the optical centre placed from the PD and height. It starts from typical lab minimums (or yours), and leaves out prescribed prism, prism thinning, aspheric designs and coatings. Treat the figures as a guide for choosing a lens; your lab's ticket is the final word.

Does it store patient information?

No. ThinCheck is a calculator: the prescription, frame and PDs stay on the screen and are gone when you close it. The only thing saved is your practice's lab figures.

Which lenses does it cover?

Spectacle lenses — plus and minus, with or without cylinder — as single vision, flat-top bifocals or progressives. Contact lens prescriptions don't apply.

Do I need the Prescription Visualizer?

No. Type any prescription and go. The Visualizer comes free with ThinCheck, though, and if a patient is already in it you can open their spectacle prescription instead of retyping it.

My lab works to different minimums. Does that matter?

Change them once, under "Your lab's figures": stock blank sizes, the thinnest centre for each material and the thinnest edge for each mounting. For one lens, type the centre thickness from the lab's ticket and everything else follows from it.

Can I try it before paying?

Yes. Every practice gets 14 days free, and nothing is charged until the trial ends. Or open the demo — three sample prescriptions and four sample patients, every control working — without signing up.