Applanation tonometry is a crucial diagnostic tool in the field of ophthalmology, playing a key role in the measurement of intraocular pressure (IOP). This non-invasive technique is widely used for the detection and management of glaucoma, a serious eye condition that can lead to vision loss if left untreated. In this comprehensive guide, we'll delve into the principles, procedure, and significance of applanation tonometry. Applanation tonometry is based on the principle of flattening a specific area of the cornea to measure the force required to do so. The Goldmann applanation tonometer is one of the most commonly used devices for this purpose. It consists of a prism that contacts the cornea and determines the amount of force necessary to flatten a small area. Applanation tonometry is a fundamental procedure in ophthalmology, providing valuable insights into intraocular pressure and aiding in the early detection and management of glaucoma. As technology continues to advance, it is essential for eye care professionals to stay abreast of the latest developments in tonometry techniques, ensuring optimal patient care and vision preservation.