Optometry case study: Coats’ disease

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Figure 1. Fundus photo of LE at presentation

By Sam Schneider, Specsavers Mandurah, WA

History

Px: 9-year-old white male
Reason for visit:
 Troubles while reading
GH:
 Normal, no medications
POH:
 Nil, prior visit 3 years prior unremarkable (Figure 2)
FOH:
 Nil

Clinical Assessment

Unaided VA: R: 6/6-3        L: 6/6-2
Unaided phorias:
 Distance: Ortho; Near: 5XP
BCVA:
 R: Pl/-0.25×175, 6/6        L: Pl/-0.50×175, 6/6
Pupils:
 PERRLA, normal reflex

Ocular health:
Anterior:
 Normal as seen, quiet A/C
Vitreous:
 Unremarkable 
Posterior:
 RE unremarkable; LE diffuse exudates, macular star, fine haemorrhages, fibrotic material above ONH, peripheral greying / atrophy (Figure 1)

Diagnosis & Management

Differential diagnosis:

  • Coats’ disease
  • Neuroretinitis
  • Retinoblastoma
  • Eales’ disease

Diagnosis: Coats’ disease

Management: Referral to paediatric ophthalmologist the next day. The patient was then monitored over the next 3 months with consideration of laser photocoagulation / cryotherapy in the near future.

Discussion

The clinical presentation of Coats’ disease demonstrates leakage from abnormal blood vessels, leaving lipid exudates on the retina. The mechanism is thought to be similar to diabetic retinopathy, involving the loss of pericytes, formation of “light bulb” aneurysms, and ultimately vessel leakage. Advanced cases can lead to visual loss worse than 6/60, particularly when there is associated fibrotic macular involvement or retinal detachments.

Coats’ disease most often affects young males between 8 and 10 years of age, and is typically unilateral. There may be no signs prior to this age, as was the case with this patient. However, about one in three of all cases occur after 30 years of age. The incidence of Coats’ disease is quite rare, affecting about 0.05% of the population in the US. The disease itself is idiopathic in nature, but is proposed to arise from a mutation of the Norrie disease pseudoglioma (NDP) gene.

In this case, an urgent referral was warranted based on the patient’s retinal presentation; however, some differential diagnoses should be considered. One such entity is neuroretinitis, in which an infectious agent (often Bartonella spp. from a cat scratch) causes inflammation of the optic disc, subsequent exudative leakage of vessels, and a distinct macular star. The patient noted having a cat at home, but had not received any recent scratches or bites. Another important differential diagnosis is retinoblastoma, which typically shows as an elevated mass in the retina. However, retinoblastoma exists in two growth patterns: exophytic (growing outward beneath the retina) and endophytic (growing forward into the vitreous). An elevated mass is characteristic of an endophytic type retinoblastoma, while the exophytic form can mimic Coats’ disease.

The decision to treat a patient with Coats’ disease is based on the stage of progression. Once exudates are present, treatment options then include laser photocoagulation, cryotherapy, and anti-VEGF injections, though up to 50% of patients at this stage eventually reach acuity worse than 6/60, despite treatment efforts. This patient presented with excellent vision considering the pathology present, though a decline in vision is anticipated as the disease progresses.


REFERENCES
Gerstenblith, A., Rabinowitz, M. 2016, The Will’s Eye Manual 7th Edition, Lippincott, Williams & Wilkins, USA.

Kramer, B., Ricca, A., Binkley, E., Boldt, H., (2016, June 30), Coats Disease. Retrieved from: https://webeye.ophth.uiowa.edu/eyeforum/cases/237-Coats-Disease.htm

Pitcher, J., Regillo, C., (2013, Sep. 5), How to Diagnose and Manage Coats’ Disease. Retrieved from: https://www.reviewofophthalmology.com/article/how-to-diagnose-and-manage-coatsand8217-disease-42782

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