Visual field loss is the most specific sign of the condition, though it occurs later in the course of the disease.As all methods of tonometry are sensitive to corneal thickness, methods such as Goldmann tonometry may be augmented with pachymetry to measure the central corneal thickness (CCT). A thicker cornea can result in a pressure reading higher than the true pressure but a thinner cornea can produce a pressure reading lower than the true pressure.Because pressure-measurement error can be caused by more than just CCT (such as by corneal hydration or elastic properties), it is impossible to adjust pressure measurements based only on CCT measurements. The frequency-doubling illusion can also be used to detect glaucoma with the use of a frequency-doubling technology perimeter.Examination for glaucoma is assessed with attention given to gender, race, history of drug use, refraction, inheritance and family history. Glaucoma has been classified into specific types:

Primary glaucoma and its variants
Primary glaucoma (H40.1-H40.2)

Primary open-angle glaucoma, also known as chronic open-angle glaucoma, chronic simple glaucoma, glaucoma simplexHigh-tension glaucoma
Low-tension glaucomaPrimary angle closure glaucoma, also known as primary closed-angle glaucoma, narrow-angle glaucoma, pupil-block glaucoma, acute congestive glaucomaAcute angle closure glaucoma (aka AACG)
Chronic angle closure glaucoma
Intermittent angle closure glaucoma
Superimposed on chronic open-angle closure glaucoma ("combined mechanism" – uncommon)Variants of primary glaucoma

Pigmentary glaucoma
Exfoliation glaucoma, also known as pseudoexfoliative glaucoma or glaucoma capsulare
Primary juvenile glaucomaPrimary angle closure glaucoma is caused by contact between the iris and trabecular meshwork, which in turn obstructs outflow of the aqueous humor from the eye.
The first-generation Molteno and other nonvalved implants sometimes require the ligation of the tube until the bleb formed is mildly fibrosed and water-tight. This is done to reduce postoperative hypotony—sudden drops in postoperative intraocular pressure. Valved implants, such as the Ahmed glaucoma valve, attempt to control postoperative hypotony by using a mechanical valve. Ab interno implants, such as the Xen Gel Stent, are transscleral implants by an ab interno procedure to channel aqueous humor into the non-dissected Tenons space, creating a subconjunctival drainage area similar to a bleb. The implants are transscleral and different from other ab interno implants that do not create a transscleral drainage, such as iStent, CyPass, or Hydrus.The ongoing scarring over the conjunctival dissipation segment of the shunt may become too thick for the aqueous humor to filter through. This may require preventive measures using antifibrotic medications, such as 5-fluorouracil or mitomycin-C (during the procedure), or other nonantifibrotic medication methods, such as collagen matrix implant, or biodegradable spacer, or later on create a necessity for revision surgery with the sole or combinative use of donor patch grafts or collagen matrix implant. And for glaucomatous painful blind eye and some cases of glaucoma, cyclocryotherapy for ciliary body ablation could be considered to be performed. Laser-assisted nonpenetrating deep sclerectomy
The most common surgical approach currently used for the treatment of glaucoma is trabeculectomy, in which the sclera is punctured to alleviate intraocular pressure.