Prescription Records: 68% of Our Customers Were Overdue and We Could Not See It

I ran a query against our own shop's records expecting a mildly interesting number. What came back was uncomfortable.

2,132 people have had a prescription recorded at our own shop. 1,453 of them — 68% — have not had one in over 18 months. A third of those have not been back in three years.

Those are not lost customers in the usual sense. Most of them are still wearing glasses we made. They simply have not been asked to come back, because until I ran the query, nobody knew who they were.

The number, in full

Grouped by how long since each person's most recent prescription:

The standard interval for an adult eye test is around two years, sooner if the power is changing. Take 18 months as the point where a message is reasonable rather than pushy, and 1,453 people are past it.

Even a low response rate on that list is a meaningful number of appointments, and every one of them already knows the shop. The cost of asking is one WhatsApp message.

None of this needs new customers, new advertising, or a discount. It needs a list — and the list only exists if the records do.

What a record has to hold

There is no legally prescribed format. What follows is what turns out to matter, in rough order of how much it costs you when it is missing.

Phone number. Obvious, and we do it — 2,949 of 2,951 records have one, 99.9%. Without it none of the rest matters, because you cannot act on any of it.

Date. The record is worthless for recall without it, and worthless clinically without it too, because you cannot tell what changed.

Sphere, cylinder, axis per eye. The prescription itself.

Add. 36.9% of the eyes in our data carry one. It also tells you the customer is presbyopic, which means their power is more likely to move — they are the people most worth recalling.

PD — pupillary distance. And here is where I have to be honest: we recorded PD on 19 records out of 2,951. Nought point six percent.

That is the one to fix, and I would guess most shops reading this are no better. PD is what lets you remake a lens without the customer coming in to be measured again. A customer who phones to say they sat on their glasses is, without PD on file, a customer who has to take an afternoon off work. With it, you order the lens the same day.

It costs three seconds at the counter and it is the difference between a service you can perform remotely and one you cannot.

Age. We have it on 96%. It matters more than it looks — it drives the recall interval. A 55-year-old's power moves faster than a 30-year-old's, and treating both as "two years" is lazy.

The GST reason to keep records

Separate from any of the above, the prescription record is a tax document in effect if not in name.

A corrective spectacle is taxed at 5%. A non-corrective one — plano sunglasses, zero-power blue-light glasses — is 18%. But heading 9004 has no sub-code separating the two. The rate is decided by the fact of whether the article corrects vision, and the only evidence of that fact on your paperwork is the invoice description and the prescription record behind it.

An invoice line reading "Spectacle — ₹6,500" at 5% claims a concession it cannot support. A line reading "Prescription spectacle — Rx: R −1.75 / L −2.00", with a dated record behind it, can. (Full rate reference.)

Why registers fail at this

Nothing above is impossible on paper. The failure is not storage, it is retrieval.

A register answers what did we give this person if you can find the page. It cannot answer who has not been back in eighteen months — that question requires reading every page and sorting, which nobody does, which is why the question is never asked.

That is the actual difference. Not that records are digital, but that a digital record can be queried backwards.

Three questions worth asking of your own system:

1. Can I retrieve a returning customer's last prescription in under thirty seconds, at the counter, while they wait?
2. Can I list everyone whose last prescription is older than eighteen months?
3. Can I see what changed between their last two prescriptions?

If the answer to the second one is no, you have the same blind spot we had.

Doing something with the list

A caution, because this can go wrong. 1,453 people is not a broadcast list. Messaging all of them at once is how a WhatsApp number gets reported and a quality rating collapses.

What is defensible:

• A reason, not an offer. "Your last eye test was in March 2024 — it may be worth checking the power" is a service message. "50% OFF THIS WEEK" to 1,453 people is spam, and will be treated as such.
• The record makes it specific. You know the date and roughly what they bought. Use it.
• Once, not repeatedly. If they do not respond, they have answered.
• Consent and opt-out. Utility-category messaging to your own customers is normal practice; blasting a purchased list is not. Keep a record of consent and honour opt-outs immediately.
• Spread it out. A few dozen a day, not fifteen hundred at once — for deliverability and because you cannot serve fifteen hundred appointments anyway.

Done properly this is the cheapest revenue in the shop. Done as a blast, it costs you the channel.

FAQ

How long should an optical shop keep prescription records? Indefinitely, if the system allows it — the value is in the history. Ours goes back four years and the older records are the ones that produced the recall list.

What should be on a prescription record? Phone, date, sphere, cylinder, axis and add per eye, PD, and age. PD is the one most shops skip and the one that costs most when missing, because without it a remake requires the customer to come in.

When should I recall an optical customer? Around 18–24 months for most adults, sooner for presbyopes and anyone whose power moved at the last visit. Age on the record is what lets you vary it instead of treating everyone the same.

Why does the prescription matter for GST? Heading 9004 has no separate code for corrective versus non-corrective, so the 5% rate rests on the fact that the article corrects vision. Your invoice description and the prescription record behind it are the evidence.

Is a register good enough? For storing, yes. For retrieval, no — a register cannot answer "who is overdue", which is where the money is.

Aggregate counts from 2,951 prescriptions recorded at one Indian optical shop, September 2022 to September 2026. Recall bands calculated on distinct phone numbers. No customer information is published.