| Have you been in front of a case with such an irregular cornea/astigmatism that you do not get reliable readings from automated refractors and you do not really know where to start the refraction? | |
| This is frequently happening after keratoplasties, keratoconus, complicated corneal surgeries and any other situation producing severe irregular astigmatism. | |
| To do a meridional refraction use the stenopeic slit. Place it in the 0°-180° meridian and get the best vision using spheres. | |
| Do the same by placing the stenopeic slit at the meridians 90°-270°, 45°-225° and 135°-315°. | |
| Fill the results in the calculator boxes and you will get a refraction to start with. | |
Calculator communicated by Dr César Albarrán from Valencia University (Spain) |