Corneal thickness measurements are often taken using a pachymeter. Corneal thickness varies among individuals, and thicker corneas may cause a measurement artifact with a higher reading being found. Likewise, thinner corneas are associated with falsely low readings. Also, thin corneas have been found to be an independent risk factor for the development and progression of glaucomatous damage.
Gonioscopy is a test in which a small lens is placed on the eye to allow the sides of the anterior chamber to be visualized. The anterior chamber angle is where fluid exits the eye, and it is important to determine if there are any secondary mechanisms such as trauma, pigment or pseudoexfoliative material obstructing this exit channel causing the eye pressure to be elevated.
Optic nerve photographs are often taken using a retinal camera. By documenting the appearance of the optic nerve and retinal nerve fiber layer at a particular moment, such pictures can establish an initial baseline for future evaluation and can then help recognize progressive damage by allowing a comparison of the current optic nerve appearance to a prior photograph. Special imaging devices such as an Optical Coherence Tomograph (OCT), Heidelberg Retinal Tomograph (HRT), or a scanning laser polarimeter (GDx) may also be used to help assess the health of the optic nerve and retinal nerve fiber layer. These instruments take images of the optic nerve and retina similar to a photographic camera. The images quantify the amount of cupping, size of the optic nerve’s rim and thickness of the fibers that make up the nerve fiber layer. Research has shown that damage to the nerve fiber layer and optic nerve often occurs before visual field changes are recognized. While these devices are not essential for making an initial diagnosis of glaucoma, they can provide important findings for the clinician.