If the mires are too wide the readings will not be accurate. Pull the slit lamp back dry off the end of the probe. Removing the probe from the patients eye then putting it back on until you have proper alignment will result in drying and staining of the cornea. Fluorescein will be absorbed into the soft lens turning it yellow. Patients who wear hard lenses should be advised not to wear their lenses as long as they would normally.
Topical anesthetics soften the cornea's epithelium making an abrasion more likely.
All patients should have has much of the fluorescein dye cleaned off as possible. If the corneal astigmatism is greater than 3.00 Diopters the measurement is made 43 degrees from the meridian of the lower power. It has been found that on very toric corneas placing the probe offset by 43 degrees gives an area of applanation closest to 7.35 mm 2 . The red line and the white line on the probe carrier are separated by 43 degrees. However, there is recent evidence that known glaucoma patient's highest pressure findings are in the afternoon.