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In three eyes with a retained intraocular metallic foreign body, the neural retina and retinal pigment epithelial (RPE) integrity were evaluated by means of ERG (a-wave, b-wave, oscillatory potentials) and non-photic EOG responses from the RPE (hyperosmolarity response, Diamox response, bicarbonate response). All three cases were judged in an early stage of retinal impairment on the basis of a well-preserved or supernormal b-wave amplitude and showed good postoperative prognosis. Out of three non-photic responses from the RPE, only the bicarbonate response was preoperatively reduced in two out of the three eyes.

The hyperosmolarity-induced changes of the apical (Vap) and basal (Vba) membrane potentials of the retinal pigment epithelium (RPE) were studied in an in-vitro RPE-choroid preparation of the frog. Both Vap and Vba were simultaneously hyperpolarized by hyperosmolarity at either the apical or basal side of the RPE. Hyperosmolarity at the apical side hyperpolarized Vap greater than Vba, and increased the trans-epithelial potential (TEP) across the RPE. Hyperosmolarity at the basal side hyperpolarized Vba, simultaneously hyperpolarized Vap by a smaller amount, and reduced the TEP. The hyperosmolarity response (a decrease of the ocular standing potential induced by an intravenous hypertonicity) is due mainly to a hyperpolarization of Vba.

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