Issue 4: Optic Nerve Head Drusen (November 2011)

Welcome

Professor Michael Kalloniatis, Director

The Centre for Eye Health (CFEH) team has hit the road recently, visiting optometrists to hear first-hand about their experiences with examining for early signs of eye disease.

Optometrists from suburbs such as Liverpool, Blacktown, Fairfield, Maroubra, Wentworthville and Penrith have talked to us about the issues they face in helping to ensure that patients who are at risk, or show early signs of eye disease are diagnosed as soon as possible.

For some, the pressure of time is a challenge, and the routine scheduling of shorter consultations can make it difficult to properly assess a patient for risk, and test for early signs of eye disease.

For others, the costs of acquiring and maintaining the latest imaging instruments is prohibitive, especially when patients are unable to pay extra to cover the investment in such services.

We were told by some optometrists that they are not always confident interpreting a patient’s results, especially when symptoms and clinical findings do not correlate.

CFEH is here to help you manage these issues. We support the optometric profession by improving access to clinical expertise, sophisticated technology and practical continuing professional development (CPD).

We haven’t been able to visit everyone yet, so we encourage you to contact us directly with any suggestions or feedback you may have.

Prof. Michael Kalloniatis

Centre Director
 

CENTRE UPDATE

  • More than 7,800 referrals have been received to date.
  • Over 35,000 occasions of service (individual tests) have been performed.
  • CFEH consultant ophthalmologists reviewed the results of 16% of clients assessed over the last three months.
  • 26% of clients were from Western Sydney in the last quarter.
  • 10% of clients were from regional areas in the last quarter.
 

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Case Report

  

Optic Nerve Head Drusen

Peter, a 51-year-old male, was referred to CFEH by his optometrist who suspected optic nerve head drusen because of some irregularities at the margin of both optic discs.

Issues to consider

1. Which tests can provide optometrists with more information about the suspected optic nerve head drusen?

2. Will visual function be affected as a result of the irregularities?

  
 

Results and Discussion

Peter presented at CFEH wearing spectacles for low myopia and astigmatism, with visual acuities of 6/6 in both eyes. He was in good health, although a smoker, and was not using any medications.

The definitive test for ONH drusen is B-scan ultrasonography. However, additional tests are included here to illustrate the presentation of ONH drusen with various imaging modalities.

Figures 1A (right eye) and 1B (left eye): Photographs of optic nerve heads.
  
Figures 1A (right eye) and 1B (left eye): Photographs of optic nerve heads.
Figures 1A (right eye) and 1B (left eye): Photographs of optic nerve heads.

Stereoscopic assessment of the optic nerve heads (ONHs) indicated that the optic disc margins were raised superiorly and nasally in each eye (Figures 1A and 1B).

Figures 2A (right eye) and 2B (left eye): Autofluorescence of the optic ner ve heads.
  
Figures 2A (right eye) and 2B (left eye): Autofluorescence of the optic ner ve heads.
Figures 2A (right eye) and 2B (left eye): Autofluorescence of the optic ner ve heads.

Retinal photography, using a blue filter for autofluorescence, revealed drusen in both ONHs at the superior, inferior and nasal locations (Figures 2A and 2B).

Figures 3A (right eye) and 3B (left eye): Vertical B-Scan ultrasound image of the optic nerve heads (drusen circled).
  
Figure 2: Left macula at baseline (A) and at follow-up (B) showing a slight increase in the number of intraretinal haemorrhages within the macula.
Figures 3A (right eye) and 3B (left eye): Vertical B-Scan ultrasound image of the optic nerve heads (drusen circled).

Hyper-reflective spots at the head, as shown with B-scan ultrasonography, were consistent with the presence of ONH drusen in each eye (Figures 3A and 3B).

Figure 4: GDxPRO Symmetry Analysis show a general thinning of the RNFL in both eyes, especially the left eye.
  
Figure 5: Cirrus OCT results show a thinning of the RNFL in the superior quadrant of the left eye.
Figure 4: GDxPRO Symmetry Analysis show a general thinning of the RNFL in both eyes, especially the left eye.
  
Figure 5: Cirrus OCT results show a thinning of the RNFL in the superior quadrant of the left eye.

GDx imaging suggested a general thinning of the Retinal Nerve Fibre Layer (RNFL) in both eyes, most particularly in the left eye (Figure 4). Cirrus Optical Coherence Tomography (OCT) results also suggested a thinning of the RNFL in the superior quadrant of the left eye (Figure 5).

Figure 6A (right eye) and 6B (left eye): Spectralis OCT results indicate elevated optic nerve heads.
  
Figure 6A (right eye) and 6B (left eye): Spectralis OCT results indicate elevated optic nerve heads.
 
Figure 6A (right eye) and 6B (left eye): Spectralis OCT results indicate elevated optic nerve heads.
  
Figure 6A (right eye) and 6B (left eye): Spectralis OCT results indicate elevated optic nerve heads.
Figure 6A (right eye) and 6B (left eye): Spectralis OCT results indicate elevated optic nerve heads.

Spectralis OCT imaging showed ONH elevation (Figures 6A and 6B) and the Heidelberg HRT3 also confirmed the elevated nature of the ONHs, providing a 3D view of each eye.

In addition to the above anatomical assessments, Peter was also functionally assessed for colour vision, contrast sensitivity and visual fields.

Figures 7A (right eye) and 7B (left eye): L’Anthony Desaturated D15 results.
  
Figures 7A (right eye) and 7B (left eye): L’Anthony Desaturated D15 results.
Figures 7A (right eye) and 7B (left eye): L’Anthony Desaturated D15 results.

During examination, he failed a monocular colour vision test, with the L’Anthony Desaturated D-15 result showing three crossings in the right eye and two in the left eye (Figures 7A and 7B).

The MARS test revealed normal monocular contrast sensitivity in each eye. Intraocular pressures, measured by the iCare tonometer, were 16mmHg in the right eye and 14mmHg in the left eye.

Figures 8A (right eye) and 8B (left eye): Visual Field Examination with the Humphrey Visual Field Analyzer Central 30-2 Threshold Test showed an arcuate scotoma in the right eye and a ring scotoma in the left eye.
  
Figures 8A (right eye) and 8B (left eye): Visual Field Examination with the Humphrey Visual Field Analyzer Central 30-2 Threshold Test showed an arcuate scotoma in the right eye and a ring scotoma in the left eye.
Figures 8A (right eye) and 8B (left eye): Visual Field Examination with the Humphrey Visual Field Analyzer Central 30-2 Threshold Test showed an arcuate scotoma in the right eye and a ring scotoma in the left eye.

Visual fields were examined with the Humphrey Visual Field Analyzer Central 30-2 Threshold Test and a ring scotoma was found in the left eye, with an arcuate scotoma in the right eye (see Figures 8A and 8B).

A diagnosis of optic nerve head drusen was made for each eye, with the recommendation that the patient be reviewed annually for progressive field loss which can occur in such cases. It was also pointed out to the referring practitioner that, should the patient develop glaucoma, it may be difficult to detect in view of the ONH and visual field appearance, and the opinion of a glaucoma specialist or neuro-ophthalmologist may be of benefit.
 

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REFERRAL GUIDE

Optic Nerve Head Drusen

Optic nerve head (ONH) drusen are typically congential and developmental anomalies of the ONH in which a form of calcified deposits occurs in some axons of the optic nerve (Figure 1). In 75% of cases they are bilateral(1).

The prevalence of ONH drusen is reported as being between 0.4% and 3.7% of the population(2).

Family members appear to have a higher risk of developing the condition, with an early study(3) finding a ten-fold risk in relatives. Inheritance of ONH drusen is considered autosomal dominant, and most likely related to the inheritance of a small optic disc and scleral foramen.

ONH drusen are most frequently located in the prelaminar portion of the ONH, and are 5 to 1,000 microns in size. They have been found to contain mucopolysaccharides, amino acids, RNA, DNA, calcium and iron(2).

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References

  1. Davis PL and Jay WM (2003). Optic nerve head drusen. Seminars in Ophthalmology 18(4) 222-242.
  2. Auw-Haedrich C, Staubach F and Witschel H (2002). Optic Disk Drusen. Survey of Ophthalmology 47 (6) 515-532.
  3. Lorentzen SE (1966). Drusen of the optic disc. Acta Ophthalmologica 90 (Suppl) 1-180.
  4. Sarkies NJ and Sanders MD (1987). Optic disc drusen and episodic visual loss. BR J Ophthalmol 71:537-539.
  5. Gittinger JW Jr, Lessell S, Bondar RL (1984). Ischemic optic neuropathy associated with optic disc drusen. J Clin Neuroophthalmol. 4(2):79-84.
  6. Gregory-Evans K, Rai P, Patterson J (2009) Successful Treatment of Subretinal Neovascularization with Intravitreal Ranibizumab in a Child with Optic Nerve Head Drusen. J Pediatr Ophthalmol Strabismus. 21:1-4.
  7. Knape RM, Zavaleta EM, Clark CL 3rd, Khuddus N, Peden MC (2011). Intravitreal bevacizumab treatment of bilateral peripapillary choroidal neovascularization from optic nerve head drusen. J AAPOS 15(1):87-90.

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Disclaimer: This newsletter is not intended to provide or substitute advice through the appropriate health service providers. Although every care is taken by CFEH to ensure that this newsletter is free from any error or inaccuracy, CFEH does not make any representation or warranty regarding the currency, accuracy or completeness of this newsletter.

Copyright: © 2011, Centre for Eye Health Limited. All images and content in this letter are the property of Centre for Eye Health Limited and cannot be reproduced without prior written permission of the Director, Centre for Eye Health Limited.

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