Understanding Post-Operative Loss of Vision

There are several causes of POVL after non-ocular surgery, including ischemic optic neuropathy, central retinal artery or vein occlusion, and cortical blindness. In fact, any interruption of blood supply to the eyes during surgery--whether caused by pressure to the eye itself or to the blood supply--or an interruption to the patient's blood flow autoregulation system can lead to POVL. One study showed that there was a higher increase of intraocular pressure (IOP) in patients whose heads were supported by pillows versus patients whose heads were supported by pins in the prone position. Another study demonstrated that as time spent in the prone position increased, IOP continued to increase as well. Some authors have suggested that IOP may increase as a result of large amounts of intravenous (IV) fluids given during surgery.

A variety of factors have been identified that contribute to the various causes of POVL, some intrinsic to the patient that can be thought of as predisposing factors, while others are related more directly to surgery and anesthesia. One study concluded that consideration should be given to establishing a minimum systolic blood pressure for each patient as well as staging long procedures and protecting eye position during surgery. Other recommendations include careful preoperative history to identify any preexisting patient risk factors that predispose to POVL; considered use of deliberate hypotension in patients at risk; avoidance of compression of the eyes, abdomen, or chest in patients placed prone; and correction of anemia and/or hypotension as early as is feasible upon identification of these risk factors. The study was published in the October 2008 issue of Neuro-Ophthalmology.

"Determining the actual overall incidence of POVL is difficult since it is not known what percentage of cases is reported,” said lead author, Molly Gilbert, M.D., an assistant professor of ophthalmology at the University of Illinois Eye and Ear Infirmary. "A wide variety of surgical interventions have been associated with POVL, including cardiopulmonary bypass, lumbar spine surgery, neck dissection, abdominal procedures, hip surgery, cholecystectomy, parathyroidectomy, prostate surgery, pleurodesis, and rotator cuff surgery.”

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