What is the recommended distance for an ophthalmoscope lens during eye examinations?

The recommended distance for using an ophthalmoscope during eye examinations is 40 cm. This distance allows for an optimal view of the retina and other internal structures of the eye. When the examiner maintains a consistent distance of approximately 40 centimeters, it helps ensure that the image seen through the ophthalmoscope is clear and well-focused.

At this distance, the optics of the ophthalmoscope are designed to provide sufficient magnification while still allowing for a detailed examination of the fundus. Using a shorter or longer distance can lead to distorted images or difficulty in viewing certain areas of the retina, thus compromising the examination's efficacy. The 40 cm distance is a well-established guideline in clinical practice, providing a balance between clarity and comfort for both the patient and the examiner.