Fig. 6.73 Fundus drawing indicating peripheral landmarks. The ora serrata marks the termination of the retina (and the beginning of the pars plana); the equator is the widest part of the eye (represented here by a dotted circle) and is defined by the vortex vein ampullae. Other landmarks in the peripheral fundus include the long posterior ciliary nerves (LPCN) and arteries at the 3 o’clock and 9 o’clock positions of the fundus. The short posterior ciliary nerves (SPCN) are located approximately at the equator and may, like the vortex vein ampullae, be asymmetrical in each hemisphere.

Ora serrata

Equator

LPCN

Vortex vein

SPCN

others that have quite a significant risk to vision if left undetected. Benign ocular findings include peripheral cystoid degeneration, which is present in essentially all patients over the age of 8 years. Disorders such as posterior vitreous detachment, white without pressure, lattice degeneration, vitreoretinal traction tufts, commotio retinae, pars planitis, retinal breaks, retinal detachment and others may be sight threatening and may go undetected without a dilated examination with BIO and possibly scleral indentation. Findings such as malignant melanoma can be life threatening.

6.22.6 Most common errors

1.Lack of practice. The image with the BIO relies on good technique and a stable view. All elements of the optical system must be maintained in alignment to obtain and maintain a steady image of the fundus. Your eyes, the oculars of the instrument, the illumination source, the patient’s pupil, the condensing lens and the part of the patient’s fundus that you wish to view must be synchronously aligned to maintain the ‘full’ lens image.

2.Recording incorrectly. Understanding and drawing the inverted and reversed image seen with BIO must be practised. Both the

anterior-to-posterior location as well as the ‘clock’ or ‘sector’ position of a lesion is important for accurate documentation.

3.Not reducing the intensity of the light source or using a yellow filtered lens to minimise patient photosensitivity.

4.Not adjusting the instrument properly, leading to diplopia, eyestrain or compromised stereopsis.

5.Starting the examination of a sector while already in the bent position. This not only limits the view of the periphery, but will cause you to miss sections of the equatorial fundus.

6.23 SCLERAL INDENTATION WITH HEADBAND BIO ASSESSMENT

Scleral indentation is an auxiliary examination technique used in conjunction with headband binocular indirect ophthalmoscopy. The primary use of scleral indentation is to enable a more detailed assessment of lesions detected with one of the other routine indirect techniques. Usually the detail is related specifically to the need for treatment of a retinal break of some sort. Scleral indentation may also be used to better understand an observed lesion. Examples include the thinning

within and traction alongside lattice degeneration; the traction associated with vitreoretinal tufts; the layer separation in flat or bullous retinoschisis. Rarely, the clinician may elect to perform scleral indentation in all sectors if risk factors warrant a closer look when first examination with BIO noted no breaks. Generally, however, indentation is targeted to a previously identified lesion.

6.23.1 Assessment of the far peripheral retina

The assessment of the far peripheral fundus may be difficult in spite of a dilated pupil. Even when a sympathomimetic dilating agent (e.g. phenylephrine) is used in combination with a parasympatholytic agent (e.g. tropicamide), the ora serrata and pars plana can be limited optically by the orbital anatomy, iris, or crystalline lens. Pupils may dilate less well in patients who are older, diabetic, have darkly pigmented irides, have previously been treated with miotics or those who have had previous ocular surgery. Even when lesions are easily observed with fundus biomicroscopy and/or with BIO, closer examination may be required with higher magnification or with dynamic techniques to facilitate accurate diagnosis and the appropriate management. In addition to the more close examination of lesions detected by other methods, scleral indentation may be indicated in those patients where no break is detected on peripheral assessment, but when one is highly suspected. These situations include:

■New symptoms of photopsia and/or floaters in the presence of highly suspicious signs including tobacco dust (RPE pigment) and/or haemorrhage in the vitreous.

■History of retinal detachment in the fellow eye, especially with new symptoms.

■Highly myopic patients where risk of peripheral retinal tears is greater.

6.23.2 Advantages and disadvantages

Scleral indentation provides a dynamic assessment of the peripheral fundus, allowing tissue separation and facilitating the detection of previously

undetected tears. The technique also allows further examination of lesions detected with other methods, e.g. retinal breaks for the presence of fluid cuffs; lattice degeneration for the presence of breaks; vitreoretinal traction, etc. Disadvantages are that the technique is tricky to master as all of the elements of the optical system need to be aligned with the examiner’s indentor, and these need to be aligned precisely on the lesion to be examined. Patient discomfort can also occur if the technique is not performed correctly.

6.23.3 Procedure

1.Perform binocular indirect ophthalmoscopy or dynamic fundus biomicroscopy of all sectors and determine the area(s) of the periphery requiring indentation. Note both the clock position and the anterior-to- posterior position (relative to the equator and ora serrata).

2.Explain the specific reasons for scleral indentation to the patient. For example: ‘I am now going to apply a slight pressure to the outside of the eye to better view a region of the inside of the eye. You may note mild discomfort or a pressure-like sensation during the procedure.’ Topical anaesthetic may be considered.

3.Recline the patient. Seated examination is not recommended.

4.Ask the patient to look in the opposite direction to the area to be viewed. Place the indentor tip on the fold of the eyelid (just beyond the tarsal plate) at the clock position on the globe where the lesion was localised. The indentor may be placed with the curve following or opposite the globe depending on patient anatomy.

5.Direct the patient fixation back toward the indentor and, as the patient moves their eye, have the indentor follow the globe back into the orbit. The indentor should be placed approximately 7 mm posterior to the limbus to indent the ora serrata, and 13–14 mm to indent the equator. If the orbital anatomy is obstructing the placement of the indentor, tilt

the patient’s head slightly to facilitate manipulation of the instrument. For example, if the brow is prominent and in the way, tilt the head back somewhat. Maintain indentor position without pressure on the globe. Tangential pressure only is required.

6.Introduce the BIO light source. Note that ‘on axis’ indentor positioning can be determined in advance of introducing the condensing lens by noting a shadow in the red reflex in the pupil. When the lens is introduced, the optical system formed by the indented region of the fundus, the patient’s pupil, the condensing lens and your pupils must be perfectly on axis to observe the indented retina. Do not apply pressure but gently roll the indentor laterally and forward and back. If the indentor is not seen, move the lens away in order to re-orient your view. You may need to alter the orientation so that the light is aimed directly at the indentor tip. Also check the anterior to posterior positioning of the indentor. If the elevated area is seen but not in the proper position, move the indentor in the opposite direction expected (away from the centre of the lens) as the view is reversed and inverted. Another way to obtain gross orientation is to remember that when the patient is looking into an extreme position of gaze and you direct your light source directly into their pupil, the equator should be in view. To extend the final 4–5 disc diameters between the equator and the ora serrata, you must bend away from the area being examined and direct the light up under the iris.

7.Observe all areas in question. For the more difficult temporal and nasal areas, the superior eyelid may be drawn downward or the inferior eyelid drawn upward with the indentor. If this is unsuccessful, the indentor may be disinfected and placed directly on the anaesthetised conjunctiva.

6.23.5 Interpretation

There are many changes that can be noted in the peripheral retina, some of which are benign and others that have quite a significant risk to vision if undetected. Scleral indentation helps to identify such lesions. For example, retinal degenerations, breaks and shallow detachments are much more obvious with indentation. The contrast of a break is enhanced as the edge of the torn retina appears more whitened while the tear itself appears to open and become more red. Subtle breaks and traction may be missed without this technique. Fluid cuffs surrounding breaks are representative of subclinical or progressive retinal detachment and observation is facilitated with scleral indentation.

6.23.6 Most common errors

1.Lack of practice. The image with the BIO relies on good technique and a stable hand, and this is even more critical when performing scleral indentation. All elements of the optical system including the indentor must be maintained in alignment to obtain and maintain a steady image of the fundus. Often the indentor is placed too far anteriorly, so it cannot be seen.

2.Moving the indentor in the opposite direction to that which is needed to facilitate the view due to the reversed and inverted image orientation.

3.Inadequate dilation can cause the iris to obstruct the view of the far periphery.

4.Applying too much pressure to the globe or orbital rim, or placing the indentor too far anteriorly near the sensitive limbus or on the tarsal plate. This leads to patient discomfort and subsequent poor cooperation. If the indentor is not in view as expected, note your alignment and try again. Do not attempt to get the view by pressing harder on the indentor.

6.23.4 Recording

6.24 GOLDMANN 3-MIRROR

UNIVERSAL EXAMINATION

See section 6.22.4. Remember that the ora serrata and equator are located approximately 7 mm and 13–14 mm posterior to the limbus respectively.

The 3-mirror Universal contact lens has three mirrors for anterior chamber angle (gonioscopy), equatorial

I

II

III

PP

Fig. 6.74 Diagrammatical representation of the Goldmann 3-mirror contact lens, demonstrating the central lens for examining the posterior pole (PP); the thumbnail-shaped mirror angled at 60º and used for gonioscopic assessment of the anterior chamber angle as well as examination of the far-peripheral fundus in a dilated eye (I); the rectangularshaped mirror angled at 66º and used to assess the peripheral fundus (II) and the trapezoidal-shaped mirror angled at 76º and used for examination of the equatorial fundus (III).

fundus and peripheral fundus examination and a central lens for posterior pole examination. The ‘thumbnail’ mirror (angled 59° to 64° from the horizontal plane) is used for gonioscopy (section 6.13), but can also be used to view the far peripheral fundus through a well-dilated pupil. The rectangular mirror (angled at approximately 66°) is used to examine more posteriorly to the thumbnail, but still in the fundus periphery. The third mirror is trapezoidal in shape (angled at approximately 76°) and is used to examine the equatorial fundus (Figs 6.53 and 6.74). Because of the limited field of view, the 3-mirror lens is not used for general assessment. Instead, it is employed when lesions are detected with other techniques such as BIO or indirect fundus biomicroscopy. This lens allows a stereoscopic view that is different from the indirect techniques. Note also that the central lens is an excellent tool for assessment of the macula (and disc), especially when fine stereopsis detail is critical (e.g. macula oedema).

6.24.1 Stereoscopic examination of the fundus

See section 6.19.1. The Goldmann 3-mirror lens allows for assessment of the macula (central lens) as well as targeted examination of previously located lesions in the periphery and midperiphery.

6.24.2 Advantages and disadvantages

Advantages include:

■The patient can remain at the biomicroscope and does not need to be placed into a supine position.

■The posterior pole, midperiphery and far periphery can be examined with the central lens and varied mirrors. The anterior chamber angle can also be examined with the thumbnail mirror (gonioscopy). This is why it is known as the ‘Universal’ lens.

■Due to the stereoscopic view that is essentially free of reflections, the central lens is very useful for examining for retinal thickening (oedema).

■With established slit-lamp skills, the technique is easier to learn than scleral indentation.

Disadvantages include:

■A dynamic view is not possible, nor is layer separation.

■The field of view is limited due to the size of the mirrors and central lens.

■Corneal anaesthesia is required.

■The patient’s pupil must be widely dilated.

■Lesion localisation can be difficult as sector position as well as anterior-to-posterior positioning is important.

6.24.3 Procedure

1.Explain the specific reasons for using the lens. Inform the patient that it is a contact lens