Knowledge of the basic principles related to the effects and side effects of cataract extraction in patients with glaucoma is essential of the surgeon is to choose a course that is most appropriate for each individual case. Some of these principles are known by all, and many are established but not known by all, and many are established but not well appreciated. Some of the principles that follow are neither well known nor well established but are based on our personal experience or the experiences of those whose clinical judgment appears to us to be sound. Principles not given a supporting reference usually fall into this category. Damage Short-term, moderate elevation of intraocular pressure is not likely to affect a healthy optic nerve.
Optic nerves vary in their ability to resist the damaging effects of intraocular pressure.
The exceptions patients with sickle-cell disease. All optic nerves are damaged permanently by intraocular pressures greater than systolic retinal artery blood pressure when such an elevation persists for more than a few minutes. Glaucomatous optic nerves are likely to be damaged by elevated intraocular pressure. The visually damaging pressure level of intraocular pressure can be estimated. The pressure at which a patient has developed a hemorrhage of the optic disc or at which progressive disc damage or visual field loss has been noted to occur prior to cataract extraction gives a rough estimate of the level of IOP the optic nerve is able to tolerate.