Views: 6 Author: Site Editor Publish Time: 2020-12-15 Origin: Site
A preoperative evaluation of silicone oil viscosity should focus on the key symptoms and causes of visual impairment and/or pain. Preoperative visual acuity was measured in patients with known refractive errors using a pre-operative MRI scan. Preoperative VASOC assessment also included arterial spin labeling and the response to local, topical anesthetics. We report the findings of a study investigating the effect of viscosity change on central vision.
Patients with known refractive error before undergoing silicone oil viscosity measurement had normal or near normal visual acuity (median oculomotor performance index, corrected for age and handedness). Patients with known underlying fundus conditions and those with abnormal or unusual anterior nasal physiology had poorer preoperative visual acuity, but this association was not significant (p>0.15). Patients with normal or near normal visual acuity had similar perfusion patterns and did not have abnormal or unusual fundus characteristics. In patients with known fundus conditions, abnormal perfusion was correlated with abnormal arterial blood flow (p>0.10).
Patients' postoperative and preoperative visual acuity improved with the addition of silicone oil viscosity treatment. The mean change in visual acuity was statistically significant (p =.001), but this improvement did not reach statistical significance in patients with known fundus conditions. This result could be due to a variety of possible factors. One possibility is that there was no significant change in the mean arterial blood flow in the normal population. Another possibility is that abnormal perfusion in the preoperative interventional arteries was associated with poor visual acuity after surgery.
Mean arterial pressure was highest during the recovery phase and lowest during the ICU stay. Thus, the mechanism through which silicone oil viscosity alters the volume changes during the ICU stay is unknown. One study did report that silicone oil supplementation improved early patient survival; however, this was based on a small number of patients. The results of a later study supported the notion that silicone oil treatment did not improve survival in patients with severe comatose and ventilator-dependent breathing due to hypoxemia and respiratory failure. Neither did it improve survival in patients with hemodynamic, pleuritic states or those who underwent bracheconium or peritoneal mesothelioma treatment.
One potential clinically relevant outcome is the effect of silicone oils on the retina. Clinical testing on postoperative eyes showed that, in general, silicone oil produced no significant change in the optical resolution or sharpness; however, it did produce a marked improvement in the retinal thickness. For this reason, we do not recommend the use of silicone oils on the retina under any circumstances.
As noted previously, retinal detachment is a very serious condition that must be treated as soon as possible. This is particularly true for children and newborns, and is why we strongly encourage the hospital staff to follow all of the recommended therapies and procedures for treating retinal detachment. Any potential worsening of the condition should be addressed immediately with qualified staff. Treatment of any underlying condition is always preferable to surgery if feasible, but if surgery is the only option, our recommendation is to use silicone oil for the duration of the patient's hospitalization, until all of the underlying issues have been addressed.
