In Optician 22.09.17, optometrist Ceri Probert wrote about the clinical signs of choroidal melanised lesions and focused particularly on the difference in signs and symptoms between malignant choroidal melanoma and the less life-threatening, though still important, lesions such as naevi. In the coming months we will be running a follow up CET article looking at the latest adaptation to the guidelines for management of these various lesions in optometric practice. In the meantime, this week we offer a CET exercise which offers the opportunity to analyse a variety of fundus lesions and decide upon their nature.

In most cases, a definitive diagnosis is not possible from ophthalmoscopy alone without other information, such as from OCT scans, autofluorescence and angiography, but in some but in some ways that is not the point of this exercise. The images shown in this exercise are for interpretation and the questions are aimed at encouraging a balanced decision based upon information rather than a definitive diagnosis. This is meant to underline the basic fact that anything of suspicion needs accurate and prompt assessment while a whole host of innocuous conditions need not be referred.

Background Information on Melanoma of the Choroid

Here are a few key points from the Probert article. The full transcript is available here and should be reviewed before attempting the questions.


Prevalence and Risk

  • Choroidal melanomas are the most common intraocular neoplasms in adults, but thankfully are still relatively rare. The occurrence of uveal melanoma overall is low, with an estimated worldwide incidence of 7,095 new cases per year, with over 80% of these being choroidal melanomas.
  • Light skin colour, light coloured irides (blue or grey) and a tendency to sunburn or an inability to tan are major risk factors. This is of particular relevance for some areas of the UK and explains some of the variation in prevalence within different health authority areas.
  • Ocular or oculodermal melanocytosis is also a risk factor.
  • One in 8,845 Caucasian patients with a choroidal naevus will develop a choroidal melanoma.
  • Environmental risk factors including arc welding and chronic UV exposure have been reported as increasing the risk of choroidal melanoma

Symptoms

Early diagnosis of choroidal melanoma is critical, as size is the most important prognostic factor for mortality. While some patients are asymptomatic, symptoms that may present include:


Commonest

  • Photopsia (often described as a ball of light or fireball travelling across the vision).
  • Floaters.
  • Visual field loss.
  • Reduced visual acuity.


Less common

  • Occasionally, uveal melanomas may cause secondary glaucoma, inflammation or necrosis, and in these instances, patients may experience pain.
  • Extrascleral extension has been reported in up to 15% of cases, and in these instances patients may present with an externally visible lesion and concomitant symptoms linked with this.

Signs of Choroidal Melanoma

  • Usually seen as raised (thicker than 2mm) and pigmented fundus lesions.
  • They are amelanotic in 15% of cases.
  • Margins are often unclear
  • Usually dome shaped (75%), but can be mushroom/‘collar stud’ shaped (20%) or diffuse/flat (5%).
  • May also be overlying sub-retinal fluid and/or orange lipofuscin pigment.

Melanoma should be considered in any growing pigmented fundus lesions, particularly in those growing rapidly. Monitoring is important therefore, even for less concerning lesions, as changes in size are an essential indicator of suspicion to look for.

The MELANOMA Mnemonic

The ‘MELANOMA’ mnemonic has been developed to aid the practitioner in detecting features suggestive of choroidal melanoma. If a tumour has none of these features there is a 4% chance of growth in five years, one feature gives a 38% chance of growth and two or more features leads to a 50% chance of growth and the diagnosis is likely to be choroidal melanoma.

  • Melanoma visible externally (extrascleral extension).
  • Eccentric visual phenomena (eg photopsia, floaters and/or scotoma).
  • Lens abnormality (eg cataract and/or new or increasing astigmatic refraction).
  • Afferent pupillary defect (usually caused by retinal detachment).
  • No improvement with optical correction (ie blurring or metamorphopsia with optical correction).
  • Ocular hypertension (especially unilateral hypertension).
  • Melanocytosis.
  • Asymmetrical episcleral vessels.

Table 1 offers a useful summary of the differences between choroidal naevi and choroidal melanoma. The images on these pages have all been taken from patients in community practice settings. These are reproduced online along with a question relating to the interpretation of the images.