The Diaton pen is a tonometer that measures intraocular pressure (IOP) through the upper eyelid at the limbus, avoiding direct contact with the cornea. It provides an alternative for measuring IOP in patients with conditions that make reliable corneal tonometry difficult, such as corneal scarring, edema, trauma or keratoprosthesis. It may also be better tolerated than corneal tonometry in pediatric patients. Studies show the Diaton provides IOP measurements that are accurate to within 2.4 mm Hg, similar to the gold standard Goldmann applanation tonometry which is accurate to 1.9 mm Hg. The Diaton represents a low-cost and less invasive option that does not require sterilization or