The patient has a surprise for you…

You have scheduled a patient for cataract surgery and the case seems relatively routine. The biometry was good and the IOL calculations seemed reasonable. The patient’s refraction prior to cataract surgery was about plano. You calculated that a +17.5 D single-piece acrylic IOL (A-constant of 119.2) will give a post-op refraction of plano.

You look carefully at the eye and even before the first incision, you can tell that there is a LASIK flap. Now you look again at the biometry and see that the axial length was 26mm and the corneal power is about 39-40 diopters. This patient must have had myopic LASIK.

What do you do now? Cancel the case and get other measurements? Or do you adjust the IOL power on the spot and do the surgery? Let’s say that you do not have any devices in the operating room which can help (no ability to do aphakic auto-refraction or aberrometry).

Click below to see the video and learn what I chose to do:


  1. Dr. Devgan.. Buenos días .. una pregunta .. el poder del LIO nuevo fue -1.5 ?? Si lo dejaba afáquico cree usted que quedaba muy hipocorregido ?? La refracción postqx quedó excelente !!

    1. Siempre es mejor dejar al paciente con un poco de miopía. Nunca deje al paciente afáquico, use siempre LIO incluso si la potencia es cero.

  2. Another option is to get on the ASCRS website and run the post myopic LASIK calculation. Yes this would prolong your case by 5 min and may require you to leave the room, but better to have the right IOL power.

    1. Good thoughts and thanks for the helpful comments. In the video we specifically address situations where access to this equipment is not available. Remember that our audience is international and not all have access to a corneal topographer, dual scheimpflug tomographer, OCT corneal imaging, etc. Without data to plug into the online calculator, what do you do?

  3. Great teaching point. How did arrive at changing IOL power by 2.5D, if you surmised there was a 6-7D myopic LASIK?

    1. A simple rule of thumb is that the IOL power is changed by about 1/3 of the excimer laser treatment (spherical equivalent) in the opposite direction. -6 D of LASIK means add about 2D to IOL power. -7.5 D of LASIK means add +2.5 D. And we want to err on the side of myopia. Also +3 of LASIK means subtract 1 D from IOL power. these are just estimates based on the work of Dr Sam Masket 20 years ago.

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