9.Shine the light at the patient’s eye and look for the red retinal reflex. Slowly follow the red reflex toward the patient and into the pupil.

10.The eyecup should be compressed about half its length to maximise the view. At this point, a large view of the entire optic disc and surrounding vessels should be visible.

11.After examining the right eye, repeat the procedure for the left eye.

6.21.4Recording

See section 6.19.4.

6.21.5 Interpretation

See sections 6.4 and 6.5.

6.21.6 Most common errors

1.Assuming that the MIO provides the same view of the peripheral retina as the binocular indirect ophthalmoscope.

2.Assuming that a lesion or anomaly has been evaluated adequately with the indirect ophthalmoscope’s non-stereoscopic view.

3.Not getting close enough to optimise the view.

4.Not matching the aperture stop to the pupil diameter. It is best to have the aperture stop less than wide open to avoid reflection from the edge of the pupil.

5.Moving around the fundus can be difficult as the centre of rotation is around the entrance pupil which is different from other fundus examination techniques.

6.22 HEADBAND BINOCULAR INDIRECT OPHTHALMOSCOPY (BIO)

The recommended technique for quick and thorough assessment of the entire fundus (equatorial, midperipheral and peripheral regions) is with a

headband binocular indirect ophthalmoscope with a20 dioptre aspheric condensing lens through a dilated pupil. Although a general assessment of the posterior pole with this technique is helpful for overall appearance, these structures should be examined with fundus biomicroscopy (section 6.19).

6.22.1 Examination of the peripheral fundus

There are many fundus abnormalities in the peripheral retina that are missed with the traditional assessment of direct or indirect monocular ophthalmoscopy through an undilated or dilated pupil, including but not limited to retinal holes/ tears and retinal detachments, intraretinal haemorrhages, exudates and infarcts, neovascularisation, retinal degenerations, vitreoretinal traction, naevi and tumours (Batchelder et al. 1997, Parisi et al. 1996, Siegel et al. 1990).

6.22.2 Advantages and disadvantages

The advantages of BIO include:

■Quick assessment of the entire fundus periphery and vitreous (Table 6.4).

■Stereoscopic viewing enabling depth perception.

■Simultaneous viewing of approximately eight disc diameters (about 35°) of the fundus. Note that less than two disc diameters can be viewed with the direct ophthalmoscope, although the exact amount is dependent on ametropia and actual disc size.

■Easy localisation of most lesions due to the very large field of view.

■Improved view through media opacities.

■Patient ametropia does not affect the view.

■Different lenses can be used to create different magnifications. The 20 D or 22 D aspheric lenses are recommended for routine use. Lower-powered lenses ( 14 D or 15 D) provide higher magnification and

may be used if the patient is bedridden or in a reclined wheelchair such that fundus biomicroscopy is not an option. They are somewhat more difficult to manipulate as they must be raised farther from the patient’s eye to get an image and of course have a smaller field of view. Smaller, higherpowered lenses ( 28 D or 30 D) provide a larger field of view but are rarely used because of their low magnification. They may be considered by a clinician who has small hands and difficulty manipulating the larger 20 D lenses, during scleral indentation due to easier lens manipulation around the scleral indentor (section 6.23) and when the patient has small pupils.

■Scleral indentation can be used in conjunction with BIO to further evaluate peripheral areas of the fundus such as the ora serrata in a dynamic manner (section 6.23).

■A very quick assessment is possible. This is especially useful when examining the fundus in cyclopleged children and special populations.

The main disadvantages of BIO are:

■The image is reversed and inverted, making interpretation and recording a challenge to learn initially.

■Mydriasis is usually required.

■Lower magnification is provided

( 3 compared to 9 to 18 with fundus biomicroscopy and 16 slit-lamp magnification, and 15 with direct ophthalmoscopy). For a more magnified three-dimensional view of a lesion identified with BIO, a lower-powered condensing lens may be used ( 14 D or 15 D), but it is probably best to use indirect fundus biomicroscopy to perform a detailed evaluation of lesions (section 6.19).

■It is recommended that the patient be placed in a supine position for the examination.

■The potential exists for light toxicity with prolonged exposure (Bradnam et al. 1995).

Box 6.3 Summary of headband BIO procedure

1.Dilate the patient’s eyes.

2.Recline the patient to approximately hip level.

3.Adjust the headband.

4.Adjust the eyepieces and mirror vertically so the spot of light is in the upper half of the field of view.

5.Adjust the illumination intensity.

6.Dim or turn off the room lights.

7.Ask the patient to look straight up to the ceiling.

8.Align the two reflections from the condensing lens with middle of the pupil.

9.Gradually pull the lens directly toward you until the fundus detail fills the entire lens.

10.Examine the fundus in a systematic, predetermined order (usually clockwise), filling the condensing lens as much as possible.

Yellow condensing lenses or yellow filters attached to clear lenses may be used and are recommended for students. They can also reduce patient glare and discomfort.

6.22.3 Procedure

A concise summary of the procedure is provided in Box 6.3.

1.Explain the test to the patient. For example: ‘I am going to examine the health of the inside of your eyes with light from the head unit and a lens held close to your eye.’ Obtain informed consent and instil an appropriate mydriatic (section 6.17).

2.Adjust the back and top of the headband of the instrument to allow for a comfortable fit. The fit may need to be readjusted as the eyepieces are adjusted.

3.Plug the instrument into the battery pack and turn it on. Release the lock on the headset and swing the housing unit down in front of your eyes until the eyepieces are as close as possible and approximately perpendicular to your line of sight

Fig. 6.71 Side view of the headband binocular indirect ophthalmoscope.

(Fig. 6.71). The closer the eyepieces are to the eyes, the larger the field of view.

4.Direct the ophthalmoscope light at your thumb or at a wall at arm’s length, and adjust the eyepieces for your interpupillary distance so that the spot of light is exactly centred in the field of view for each eye. Adjust the mirror vertically until the spot of light is situated in the upper half of the field of view ( 4° adjustment arm). This allows the

illumination beam to pass above the observation beam to minimise reflections during patient examination. Most instruments possess this adjustment.

5.Adjust the illumination intensity to low to medium low and the illumination beam to the largest spot size that can be used for the patient’s pupil size. For a dilated pupil, use the largest spot size. A smaller spot size may be considered if the pupils are not fully dilated.

6.Ask the patient to remove any spectacles, and explain that you are going to recline the chair as at a visit to the dentist. Adjust the chair to the reclining position, so that the patient is at approximately hip level. The supine position allows you to stand approximately opposite the area of the fundus being viewed, optimising stereopsis

and the extent of viewing area while minimising back strain. Examination with the patient seated upright can also be performed if reclining is not possible. The inferior and superior fundi are more difficult to examine with a seated patient as the light source must be well above the patient’s head to view the inferior peripheral fundus, and towards the patient’s lap to see the superior peripheral fundus.

7.Dim or turn off the room lights.

8.Pick up the aspheric condensing lens with the white or silver edge of the lens casing toward the patient to minimise reflections and optical aberrations. Hold the lens between the index finger and the thumb. The little (or the third) finger can be used to retract the upper eyelid and allow for stable extension of the lens away from the patient’s eye, while at the same time acting as a pivot, enabling the observer to tilt the lens in all planes merely by rocking the lens system. The other eyelid may be retracted with the thumb of the opposite hand. Alternatively, the little (or the third) finger of the opposite hand may be employed so that this second index finger can also be used to help stabilise the lens. The lens can be moved with critical control closer or further from the eye by increasing or decreasing the extension of the little finger stabilising on the patient’s eyelids. Ambidexterity should be practised and is required for scleral indentation.

9.Novices will want to view the recognisable posterior pole first, so should ask the patient to look straight up to the ceiling if in supine position or over your shoulder if seated upright.

10.Direct the BIO light source so that it is centred on the patient’s pupil. Introduce the condensing lens close to the patient’s eye (2 to 4 cm) such that the external eye can be seen through the lens and with slight magnification. Centre the pupil in the condensing lens (observe the red reflex), and align the two reflections from the 20 D

lens surfaces with each other and in the middle of the pupil. Gradually move the lens away from the patient’s eye (towards you) and fundus detail will become progressively magnified until the red reflex fills the entire area of the lens.

11.Keep the pupil centred in the lens at all times or the fundus view will be lost. Only slight misalignment of any part of the optical system will cause shadows, distortion, or complete loss of the view. Stabilisation of the lens with a finger from the second hand helps to minimise this fluctuation. When loss of the image occurs, move the lens towards the eye again, until the pupil can be recognised and centred, and pull the lens back towards you again to maximise the image in the lens.

12.Keep the headband unit at arm’s length to the lens. When the examiner moves closer to the lens, difficulties with accommodation, convergence or loss of binocularity may occur, as will a smaller field of view.

13.If reflections from the condensing lens block visualisation of the fundus, displace the reflections by tilting the lens slightly. Excessive tilting, however, induces astigmatism and will distort the fundus image.

14.To view the different regions of the fundus, change position around the patient and tilt the lens so that the optical system formed by the patient’s pupil and fundus, the condensing lens, and your pupils remain aligned along the widest part of the patient’s pupil. To examine the superior fundus, for example, ask the patient to look upwards while you direct the illuminating beam toward the superior fundus. A ‘full’ lens image in this position will show approximately 8 DD of the fundus near the superior equator. Examine farther into the peripheral fundus by moving the light source anteriorly (toward the ora serrata), making sure the elements of the optical system remain in alignment so that the image continues to fill the lens as much as possible. To do this, you must bend along

the line of sight but in the opposite direction (i.e. towards the patient’s feet). Because the image is reversed and inverted, attempting to shift the field of view in one direction will cause the image to move in the opposite direction. It helps to remember here that only the lens view is reversed and inverted; that is, if you wish to see more temporally, direct the light in that direction; more superiorly, direct the light towards the superior fundus and so on.

15.Stereopsis is achieved by imaging both of the examiner’s pupils within the patient’s pupil. This is facilitated by a large patient pupil with maximum dilation. During the examination of the patient’s periphery, the patient’s fixation is directed towards the sector that is to be examined. The pupil relative to the examiner’s perspective is oval, with the long axis of this pupil perpendicular to the patient’s line of sight. To maximise stereopsis in these situations, keep your two pupils aligned with this long axis. If the patient’s pupil is very large or they are not looking too far off axis, stereopsis is still possible without this alignment with the long axis, but it is less likely and less consistently achieved.

16.It is advised that you examine the fundus in a systematic, predetermined order. Some clinicians elect to examine the regions of the equatorial and peripheral fundus before the posterior pole to allow the light-sensitive patient time to adapt (unless the posterior pole has just been examined with fundus biomicroscopy anyway). Direct the patient gaze towards each individual sector until all eight sectors of the fundus have been examined (plus the posterior pole). Moving clockwise in each eye is a good initial method.

6.22.4 Recording

The fundus image viewed through the condensing lens is a real image created between the patient and the examiner and the image is reversed and inverted. Therefore, when viewing the posterior

10

9

8

AB

8

9

10

Fig. 6.72 Demonstration of recording methods for BIO and other indirect techniques. The top portion of the figure demonstrates the patient’s position of gaze and diagrammatic representations of the view in the binocular indirect lens ( 20 D). Option A represents mentally reversing and inverting the image seen and recording on the patient’s chart. Asymmetric and complicated lesions are more difficult to interpret and document properly in this manner. Option B demonstrates how the examiner may draw the lesion exactly as it was seen and in the proper clock position, but with the recording paper turned upside down.

pole, what is seen to be superior in the view is actually inferior, nasal is temporal and temporal is nasal. When viewing the peripheral fundus, the area of the image that appears closest to you in the condensing lens (i.e. towards your thumb) is actually more anterior (peripheral) in the fundus. For example, when the patient is looking up above their head, the more peripheral retina will be seen at the bottom of the lens, and whatever appears to be located to your right within the lens is actually located to the left on the fundus. However, although the view of the superior fundus will be inverted and reversed, if you direct the light towards the superior fundus with the patient looking upwards, you will be looking at the superior fundus.

The most useful way to record fundus findings is with a sketch accompanied by brief explanatory notes. By convention, fundus details are recorded with two circles, one within the other. The inner circle represents the equator and the larger one surrounding it represents the ora serrata (Fig. 6.72). Note that although the outside circle is larger, the circumference of the ora serrata is actually less than

the equator, the widest part of the globe. To draw a lesion, some examiners mentally reverse and invert the image as seen in the lens and then draw it in the correct location. Others place the examination form upside down to compensate for the reversed inverted image, and draw exactly what they see in the lens (while considering where the patient was looking and therefore the proper clock position; Fig. 6.72). Both methods take some practice to master. Determining the appropriate anterior-to-posterior location in the fundus can be facilitated by certain normal landmarks in the fundus (Fig. 6.73).

6.22.5 Interpretation

See sections 6.4 and 6.5. The various landmarks of the peripheral retina (Fig. 6.73) are rarely included in a fundus drawing but assist in identifying and documenting the location of any noted findings. There are many changes that can be noted in the peripheral retina, some of which are benign and