Every medical and nursing student knows this moment. You open last year's deck, the one your friend swore was gold, and within ten minutes you hit a card that contradicts what the professor just said in lecture. The slides changed. The guidelines changed. Some detail got added, some drug got renamed, and now you are studying cards you cannot fully trust.
Rebuilding the deck from scratch is the honest answer most people avoid. It takes weeks, and you lose all your scheduling progress. But there is a middle path: systematically update the deck you have against the slides you were actually taught from. Here is how to do it, manually first, then the fast way.
Step 1: Diff the slides against your deck
Open the new lecture slides next to your Anki browser. Go slide by slide and ask one question per slide: "Do I have a card that teaches this?" You are looking for three categories:
- New material — slides with facts, tables, or diagrams that have no corresponding card.
- Changed material — slides where the fact is the same but a detail moved: a new cutoff value, a renamed drug, an updated guideline.
- Dead cards — cards testing facts that no longer appear anywhere in the slides. These are the dangerous ones, because Anki will keep scheduling them and you will keep memorizing something untestable.
Most students skip the diff and just add cards for whatever felt unfamiliar in lecture. That works for category 1 but completely misses categories 2 and 3, which is where stale decks actually hurt you.
Step 2: Add cards only for the gaps
For genuinely new material, make cards the way you normally would: one fact per card, cloze deletions for lists and values, image occlusion for diagrams. Tag them with the lecture name and date so you can find them later. Do not re-make cards for material that is already covered. Duplicates are worse than gaps — they double your review load without adding knowledge.
Step 3: Fix or suspend the outdated cards
This is the step everyone skips. For changed material, edit the existing card in place rather than making a new one. Editing preserves your review history and scheduling, which is months of spaced-repetition progress you do not want to throw away. For dead cards — material the professor cut — suspend them, do not delete them. If the topic comes back on a cumulative final, unsuspending is one click.
The fast way: diff the deck automatically
The manual diff is the right process, but it is slow. Going slide by slide through a 200-slide lecture against a 5,000-card deck takes an entire weekend, which is why most students never do it and just study the stale deck.
This is exactly what SlideToAnki's deck improvement was built for. You upload your existing .apkg deck plus the new lecture slides, and it compares the two: it proposes new cards for material the slides cover that your deck does not, and it flags existing cards that conflict with or are missing from the new slides. Every proposal goes through a review queue where you accept, reject, or edit each change, and every card carries a citation back to the source slide so you can verify it. Added cards get tagged so you can find them later.
The key difference from making a fresh deck: your scheduling progress survives. Changed cards are edited in place, not replaced, so the spaced-repetition history you built all semester keeps working.
A workflow that actually sticks
However you do the diff, build it into your routine once per block, not once per year. The longer a deck drifts from the slides, the more painful the update. Thirty minutes of maintenance after each lecture week beats a panicked rebuild during dedicated study period.
Your deck is a living document. Treat it like one and it will stay the highest-yield study tool you own. Let it go stale and it becomes a very efficient way to memorize the wrong things.