The prism head of Goldmann-type tonometers should be cleaned immediately after use. The prism should either be soaked in a 1:10 sodium hypochlorite solution (household bleach), 3% hydrogen peroxide, or 70% isopropyl alcohol for 10 minutes. If a soaking solution is used, the prism should be rinsed and dried before reuse. If isopropyl alcohol is employed, it should be allowed to evaporate, or the prism head should be dried before reuse. Although the use of alcohol is a recognized and well-established method of disinfection, its use may cause tension cracks in the tonometer tips. Haag-Streit strongly discourages the use of isopropyl alcohol 70%.