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A directory of major international and Indian IOL manufacturers, for professional reference. A genuinely important note first, before the list itself.
The A-constant is a lens-specific value used in IOL power calculation formulas (originally SRK, still used in SRK/T) to help predict the correct lens power for a given eye. It was first developed in 1980 and remains the most familiar lens constant to ophthalmic surgeons and manufacturers.
This is worth being direct about. The A-constant isn't simply one fixed number per brand — it varies by the specific lens model, by the biometry device used (optical biometers like the IOLMaster give a different reference constant than ultrasound), and is routinely personalised by individual surgeons based on their own outcomes for genuinely optimal results. Even ULIB, historically the standard shared reference, hasn't been consistently updated in recent years according to current literature.
Publishing a static table of specific numbers on a website carries a real risk: if a value becomes outdated or doesn't match your specific lens model or biometer, using it directly in a power calculation could contribute to a genuine refractive surprise for a patient. That's not a risk worth taking for the sake of a convenient table.
Instead, here's a directory of the major manufacturers and their well-known lens families, so you know where to look — paired with a reminder to always pull the current, model-specific constant from IOLCon.org (an actively maintained public database), the manufacturer's current package insert, or your own optimised value, before any real calculation.
For the current, lens-specific A-constant, visit IOLCon.org or check the manufacturer's current documentation directly.
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