Ophthalmoscopy is a routine exam done by ophthalmologists to examine the inside of the back of the eye, also known as the fundus or posterior segment. Although there are several types of ophthalmoscopy, we will focus on Binocular Indirect Ophthalmoscopy or BIO, for short, in this article. BIO is one of the ways used to view the retina, with a wide field of the retina and stereoscopic view. BIO also allows dynamic observation of the retina by moving the BIO device, lens, and applying scleral depression. The process is “indirect” because the fundus is viewed through a hand held condensing lens.
The examiner looks through the pupil to view the posterior segment of the eye. However, the undilated pupil restricts the view field of view dramatically, specifically the bright light of BIO usually makes the pupil very small. Doctors will generally decide to administer dilating drops. Mydriatics are dropped into the eye.
A technique commonly used with BIO is scleral depression. This complements the dynamic viewing of the retina and vitreous. The forward and inward curvature of the globe in the anterior portion of the eye obscures and prevents far peripheral viewing Therefore, scleral depression (or special contact lenses such at Goldman 3-Mirror contact lens) is needed to indent the scleral and bring the peripheral retina into view.. To depress the sclera, a scleral depressor is placed against the sclera (either on the globe or on the eyelid overlying the globe) and gentle firm pressure is applied. This pushes the sclera and the retina into the examiner’s field of view during the BIO exam.