BIO Home Optics of BIO Patient Preparation BIO Observation
Cleaning the Condensing Lens 
Clean the lens on a regular basis.
Don't clean the lens with a dry cloth. Excessive rubbing with a dry cloth will scratch the AR coating on your lens and will smear finger and nose prints.
First wet the lens with warm water and then use an unscented, mild detergent, a contact lens surfactant cleaning solution, or a photographic lens cleaning solution.
After rinsing under warm water, shake the excess water from the lens and remove the remaining water with a soft lint-free cloth.
Oculars can be cleaned in the same manner as any ophthalmic lens.
The mirror that directs the light from the headset is a front-surface mirror and should be very carefully cleaned according to the manufacturer's recommendations.
Steps for Adjusting the Instrument for Use
1) Headband crown adjusted.
2) Comfortable circumference.
3) Proper elevation.
4) Close to eyes/spectacle lenses.
5) Vertical adjustment of oculars.
6) Pupillary Distance (PD) adjustment.
7) Illumination intensity correct.
8) Light in the upper half of field through oculars.
9) Filter in place if desired.
All BIOs consist of a light-source housing mounted in a headset, oculars containing plus-powered lenses, and prisms to reduce the effective PD allowing the examiner to sight through the narrow aperture of the pupil.
The crown strap should be set so that the headband is snug without encroaching on the eyebrows or sliding above the frontal hairline. The rear portion should comfortably straddle the ridge at the back of the skull.
The headband should fit like a visor or the rim of a baseball cap, approximately one finger's width above the eyebrow. Once the headband has settled to its position as determined by the crown strap, it can be tightened, but just to the extent that its movement around the head is prevented.
Next align the light tower oculars assembly. Loosening the appropriate set screw will allow this unit to pivot. It should be swung so that the oculars are as close to the examiner's pupils as possible and at eye level.
The BIO housing should be horizontally centered before the examiner's eyes. While looking through the BIO, this can be checked by alternately closing one eye at a time to see whether the dark border formed by the bottom of the BIO housing window is level. If this is not the case, then the BIO is tilted.
Next, set each ocular to correspond to the PD in order to optimize stereoscopic ability. By looking at your thumb held at arm's length (18 to 20 inches), alternately close each eye to determine whether the extent of each separate visual field is identical. Make any necessary correction if it is not.
Now turn on the light source, put your thumb in the center of the field seen through the oculars, and adjust the vertical position of the light source so that it is projected into the upper half of the binocular field (towards the top of your thumb). This will allow the light from the BIO to enter the patient's pupil higher than the images of the examiner's visual axes. The lower half of the lens is used for viewing, thus reducing unwanted reflections. It's necessary for the ophthalmoscope and the images of each ocular to fit within the pupil of the patient.
Nearly all complaints of blurry vision arise from either being too close to the patient or are secondary to uncompensated distance refractive errors.
Most of the complaints of diplopia are from inexperienced examiners who fail to make the adjustments properly. Vertical diplopia is almost universally caused by a tilted ophthalmoscope housing and can be easily remedied. Adjusting the PD incorrectly, or being too close to the patient frequently causes horizontal diplopia. It can also occur if the examiner has reduced fusional vergences.
Grasp the condensing lens with the tip of your first finger and the pad of your thumb diametrically opposite to each other. The more-convex side of the lens should be facing the examiner (i.e., the white ring should be facing away from you). Your second (middle) finger can then act as a pivot and lid retractor.
Place the condensing lens close to the patient's eye. Center the pupil and then slowly move the lens away from the eye by extending your pivot finger. The image of the pupil will get larger. When the lens is at its focal length, the lens will be filled with the image of the fundus. If you lose the image, drop down closer to the eye, re-center the pupil, and slowly pull back until the lens is filled again.
During practice, you should imagine that the fundus under examination, the center of the patient's pupil, the center of the condensing lens, and the examiner's visual axis are all connected by a rigid rod. Movement to an adjacent portion of the fundus should be performed with this concept in mind. Move your entire torso from side-to-side to get out further on the fundus and to scan the retina.
Only shine the light into the eye long enough for adequate evaluation. Start with the light at about the half-scale setting (or lower). At the half-scale voltage setting, the recommendation is that no more that 40 seconds should be spent looking at any one area of the fundus.
The pupil should be dilated to its maximum possible diameter. The most satisfactory dilation for routine examination for adults is achieved by using 1.0% tropicamide plus 2.5% phenylephrine drops after a topical anesthetic drop. Before administering the drops, assess the appropriateness of drug use.
a. Rule out drug sensitivity.
b. Rule out risk for angle closure by standard slit lamp assessment (van Herick method).
c. Rule out any other contraindications including systemic disease and other ocular considerations such as an iris-fixed IOL.
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