Head Band Indirect Ophthalmoscopy

by S.Barnard. BSc(Hons).FCOptom.DCLP.FAAO.and A.Field..MSc.FCOptom.DCLP.FAAO.


In recent years head-band indirect ophthalmoscopes have been developed that enable the practitioner to converge the entrance and exit pupils. This very important improvement means that the optometrist can examine every patient using this technique until he/she has gained enough experience. Like SLM, dilation will then provide a technique that will become a easy task for the optometrist.

The advantages of this method includes the provision of (a) an excellent field of view (approximately 40°), (b) the ability to move around the patient and therefore enlarge upon the field of view, (c) a stereoscopic view, (d) excellent illumination and (e) scleral indentation.

These characteristics lend head-band indirect ophthalmoscopy to be secondary to SLM indirect ophthalmoscopy for the routine examination of the fundi of patients in shared care or co-management programmes involving glaucoma and diabetes. However, the head-band indirect is particularly useful for examining fine variations in the fundus colour that may be caused by tumours for example, and for viewing the more peripheral areas of the retina. Useful for suspected detachments, floaters associated with photopsia, and high myopes. This facility may well be useful in co-management programmes monitoring post-operative detachment surgery, or the monitoring of peripheral lesions that may have a predisposition to detachment.

The head-band indirect technique produces a real, inverted and laterally reversed fundus image. Presently available lens powers range from +14D to +30 D. Lower power lenses provide higher magnification but offer a smaller field of view, and below about +20D, the lens needs to be held further from the patient's eye and may not be comfortable for steady positioning. Lenses above +20D may give less magnification than is desirable.

General procedure for head-band binocular indirect ophthalmoscopy.

Preparation


Fig 1

Fig 2

Alignment of the head-band ophthalmoscope.


Procedure.

Having obtained an image filling the BIO lens, the fundus may then be examined by moving around the patient if reclining, or by redirecting the patient's fixation if seated. It is at this point that it becomes obvious that it is definitely preferable to have the patient reclining if possible.

Fine tuning the fundus view


Hints and tips for successful Head-band BIO.

  1. Practitioners should practise on non-dilated eyes. Practical only with ophthalmoscopes that have converging systems.
  2. It is essential to have a steady hand, and the practitioner must rest part of his hand on the patient's head. This is particularly so with non-dilated pupils.
  3. Remember the Imaginary Convex Eye technique.
  4. A better peripheral view will be obtained using a +28D or +30D lens and scleral indentation. However, a higher power lens will reduce magnification. Conversely, a better view of the optic disc will be obtained with lenses of a power in the +15D range.
  5. Fundus drawing should either be done from behind the patient if reclined, or with the record card inverted if seated.

Scleral Indentation

To take full advantage of head-band binocular indirect ophthalmoscopy, the practitioner should learn to perform scleral indentation.
The procedure is not as difficult or as uncomfortable for the patient as may be imagined. Neither will indentation worsen or cause retinal detachments. It is however relatively time consuming, and therefore special arrangements for appointments will generally be necessary.

Preparation

Fig 3

Alignment of the head-band ophthalmoscope.

Procedure.

Hints and tips for successful scleral indentation.

  1. Practitioners should practise on non-dilated eyes, pupils above about 4 mm will be usable. Practical only with ophthalmoscopes that have converging systems.

Yes, it is possible.

  1. It is essential to have a steady hand, consequently the practitioner must rest both hands on the patient's head.
  2. The 3o/c and 9o/c positions can be indented by placing the depressor slightly above on the upper lid (2o/c and 10o/c), and sliding the probe downwards to move it into the inner or outer canthal positions. If this is difficult, indentation can be done applying the probe to the sclera without the intervening lid, but topical anaesthesia should be used to make your patient comfortable.
  3. Remember the Imaginary Convex Eye technique.
  4. A better peripheral view will be obtained using +28D or +30D lenses.
  5. Fundus drawing should be done from behind the patient.


Pupil dilation

To obtain an adequate view when not practising, ophthalmoscopy should be carried out under mydriasis.

Choice of drug

The drug of choice is tropicamide 0.5% or 1% ( Minims Tropicamide, Mydriacyl) because it is both fast acting and of short duration as compared to cyclopentolate hydrochloride. It will abolish the pupil light reflex which is advantageous when carrying out BIO and fundus photography. Post-examination visual needs of the younger patient need to be considered since tropicamide has the potential for causing significant, albeit short-lived, cycloplegia.

Phenylephrine is available in 2.5% and 10% concentrations. Minims Phenylephrine are available in both percentages. The 2.5% is generally adequate for most patients and the 10% concentration is rarely indicated in optometric practice. Neither the light reflex nor accommodation is abolished with sympathomimetics. Sphygmomanometry should be carried out on all diabetic patients of 40 years of age and older before the use of phenylephrine is considered.

To obtain optimal mydriasis a combination of both drugs is indicated whenever possible, for example a drop of phenylephrine 2.5% in each eye followed a few minutes later by a drop of tropicamide 1%.

Precautions

The use of phenylephrine is contraindicated in the presence of vascular hypertension, a history of cardiac disorders, stroke or aneurysms and when the patient is using certain medications including monoamine oxidase inhibitors (e.g. phenelzine, Nardil), alpha-2 adrenergic agonists (e.g. clonidine hydrochloride, Catapres, Dixarit), adrenergic neurone blockers (guanethidine monosulphate, Ismelin).

The use of sympathomimetics should be avoided in optometric practice with long-standing diabetics particularly those with known marked background, pre-proliferative or proliferative retinopathy. Such patients are more likely to manifest a peripheral neuropathy which may include sympathetic denervation. These patients may show "super-sensitivity" to phenylephrine, the instillation of which may have an unwanted and exacerbated effect on the cardiovascular system.

Guidelines for dilating patients with narrow angles

  1. Care must be taken in the presence of a very narrow or shallow angle which has not been dilated previously. If the practitioner is confident that mydriasis will provoke angle closure, then an ophthalmological opinion should be sought.
    (Van Herick, W., Shaffer, R.N., and Schwartz)
  2. If the patient has been dilated previously, with no induced rise in ocular tension, the practitioner can dilate again.
  3. In all cases of angle grades 1 and 2, the patient's ocular tensions should be checked before instillation of the drug(s) and again 30 minutes after completing the examination. It should be noted however that there can be rises in pressure some hours later.
  4. The practitioner should always bear in mind that failure to examine the fundus properly under mydriasis may lead to serious retinal changes being missed. The risk of provoking angle closure must be weighed against this in the knowledge that, in due course, a predisposed patient is, in any event, very likely to experience a sub-acute or acute glaucoma attack.

Post mydriatic management

  1. The use of a parasympathomimetic such as pilocarpine to routinely reverse mydriasis is probably not indicated for most patients. The visual effects of tropicamide and phenylephrine are either very short in duration or insignificant and for most patients there is little to be gained by the instillation of a miotic. It should also be noted that pilocarpine may cause anterior displacement and steepening of the lens in some eyes. Thus there may be a very slight risk of provoking pupillary block glaucoma in predisposed eyes. Hyperopic eyes and/or eyes with shallow anterior chambers are considered to be more at risk (Doughty, 1995).
  2. In the very unlikely and rare event of a significant rise (> 8 mm Hg) in ocular tensions due to angle closure following tropicamide and/or phenylephrine mydriasis, the practitioner should be aware of management strategies for the patient. Ophthalmologists differ in their philosophies and individual optometrists should discuss with their local consultant ophthalmologist what intervention should be employed in these circumstances. One treatment strategy would be to instil 1 drop of pilocarpine 1% or 2%. After 15 minutes (q 15 min) the pressures and angle should be checked again and another drop instilled if necessary. This procedure may be repeated until the attack is broken For some patients 1 or 2 drops may be sufficient to break the attack; in others, 4 to 6 drops might be required (Doughty, 1995). One should proceed cautiously with aggressive use of pilocarpine drops (q 15 min) if tonometry indicates excessively high intraocular pressures (i.e. > 50 mm Hg) since it has been suggested that such a use could exacerbate a pupil block; lowering the intraocular pressure with an oral carbonic anhydrase inhibitor should be the initial goal in such patients prior to the aggressive use of the miotic.

Alternatively, the local ophthalmologist may prefer the optometrist to instil one drop of pilocarpine before referring the patient (preferably under escort) to the hospital Accident and Emergency Department or even send the patient directly to A & E with no pharmacological intervention. The optometrist should ensure that there is a practitioner available to receive the patient.

References and further reading

Doughty, M. J. Drugs, Medication and the Eye, Chapter 9, Glasgow-Caledonian University, 1995

Field.A and Barnard N.A.S., Imaginary convex eye. An aid to indirect ophthalmoscopy. Optometry Today, May 31, 22, 1993

Fingeret, M., Casser L., Woodcombe, H.T. Atlas of Primary Care Procedures, Appleton & Lang, Norwalk, 1990

Prokopich, C..L., and Flanagan, J.G. Indirect fundus biomicroscopy. Ophthal. Physiol. Opt. Vol 15 (Suppl 2), S38-S41, 1995

Van Herick, W., Shaffer, R.N., and Schwartz, A. Estimation of width of anterior chamber. Am J Ophthalmol., 68, 626-629, 1969