An optical interface device having an opening for an optical path that can be non-circular and having engagement members having gradually varying angles of engagement. An embodiment of the interface device can be a one size fits all device, providing a configuration that fits in all typical eye openings, including narrow palpebral fissures and small eyes, while providing optical path access to features and structures of the eye. An embodiment of the interface device engages the limbus, cornea and sclera.
