3. Forster-Fuchs' Retinal Spot

Forster-Fuchs' Retinal Spot

This PatientPlus article is written for healthcare professionals so the language may be more technical than the condition leaflets. You may find the abbreviations list helpful.

Synonyms: Forster-Fuchs spot, Fuchs' retinal spot, disciform degeneration in myopia and choroidal neovascularisation in myopia.

Myopia ('short-sightedness') arises as a result of a high axial length of the globe (ie a long globe as measured from front to back) - see our record on Refraction and Refractive Errors for more details. In some highly myopic patients, the axial length never stabilises, a condition known as progressive myopia.

High myopia (6 dioptres or more) or progressive myopia are conditions prone to degenerative changes characterised by pale, well circumscribed, tessellated patches of chorioretinal atrophy both centrally and peripherally. These areas are prone to breaks in one of the retinal layers - the Bruch's membrane - resulting in cracks appearing throughout these lesions (like lacquer cracks). Subsequent neovascularisation and macular haemorrhage lead to a pigmented scar known as the Forster-Fuch spot. This raised, pigmented, circular lesion develops after the macular haemorrhage has been absorbed.[2]

Other changes include a tilted disc with associated atrophy, early age posterior vitreous detachment, zonular dehiscence (ie the zonules holding taut the capsular bag containing the crystalline lens) and pigment dispersion syndrome.

Forster described subretinal neovascularisation in severely myopic eyes in 1862 and Fuchs described a pigmented lesion at or near the fovea in 1901. They are both part of the same process.

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  • The prevalence of progressive myopia shows geographical variation (eg it is high in Spain and in Japan) but generally, it is thought to occur in 1-10% of myopic eyes.[1]
  • Up to one third of severely myopic eyes can show degenerative changes.[3]
  • It can strike at any age but it is a very significant cause of blindness in young people in developed countries. A study in Australia found the spots in 3 of 3654 elderly people, giving a prevalence of 0.1% in this age group.[4]

This is a condition seen in high myopia. There may be genetic and environmental influences (excessive near work) contributing to the myopia. Other associations with myopia include:[1]

Symptoms[5]

  • Presentation is with deteriorating vision (increasing myopia).
  • There may also be complaints of visual distortion with wavy lines (metamorphopsia).
  • Central or paracentral scotoma.
  • Impaired colour vision.
  • Prolonged recovery from light stress.

Signs

  • Ability to read the Snellen chart may deteriorate by 2 lines or more in a fairly short space of time.
  • The Forster-Fuchs spot may be seen near the fovea but there are wide variations in the appearance.

Fluorescein angiography shows subretinal neovascularisation from the choroid as the basic underlying disease in most cases.[6]

Drugs

Pharmacological treatment is a new area with studies just emerging now. Intravitreal bevacizumab is the most recent candidate drug.[7] This needs to be given every three months (the invasive nature of intravitreal injections means there are risks of complications) but a recent 12-month prospective study has shown some promising results so far - all be it on a very small number of eyes.[8]

Surgical

Conventional treatments of laser photocoagulation or surgical extraction of the area of neovascularisation have had limited effectiveness, partly due to the limitations of not being able to laser over the foveal area (this destroys it and the sight it imparts). Newly developed treatments such as foveal translocation or photodynamic therapy have had favourable results in the short-term,[9] particularly in the younger patient presenting with larger lesions but with a better initial visual acuity.[10] More RCTs are needed.

A vitrectomy may be carried out to prevent a particular type of PVD which affects these eyes, from leading to a traction maculopathy.[11] Surgical excision of subfoveal choroidal neovascular membranes in high myopia in a study brought improvement of visual acuity of at least 2 lines in 45% and no change in 37%.[12] Another trial had similar results[13] with the visual acuity improved by 2 or more Snellen lines in 39%, decreased in 35% and remained unchanged in 26%.

Without treatment atrophy occurs around the area and prognosis is very poor.[9] The new vessels cause traction on the retina which can lead to a retinal detachment. These patients are also at greater risk of developing macular holes.[11][14]

A study from Moorfields in 1983[15] showed a generally poor prognosis without intervention with 43% of the patients losing 2 or more lines of vision, while 60% were less than or equal to 6/60 at last follow-up. There was a direct relationship between visual acuity and the distance of the neovascular tissue from the fovea, and an inverse relationship between acuity and the size of the lesion. There seems to be a short neovascular growth phase, with early visual loss.

Older patients tend to have a poorer outcome than younger ones.[16]

Optical coherence tomography[3] can detect this at its early stages so that intervention may take place.

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Further reading & references

  1. Denniston AKO, Murray PI. Oxford Handbook of Ophthalmology (OUP), 2009.
  2. Kanski J. Clinical Ophthalmology; A Systematic Approach (5th Ed) Butterworth Heinemann (2003)
  3. Panozzo G, Mercanti A; Optical coherence tomography findings in myopic traction maculopathy. Arch Ophthalmol. 2004 Oct;122(10):1455-60.
  4. Vongphanit J, Mitchell P, Wang JJ; Prevalence and progression of myopic retinopathy in an older population. Ophthalmology. 2002 Apr;109(4):704-11.
  5. Charles S; Neovascular Membranes, Subretinal. eMedicine, December 2006.
  6. Levy JH, Pollock HM, Curtin BJ; The Fuchs' spot: an ophthalmoscopic and fluorescein angiographic study. Ann Ophthalmol. 1977 Nov;9(11):1433-43.
  7. Chang LK, Spaide RF, Brue C, et al; Bevacizumab treatment for subfoveal choroidal neovascularization from causes other than age-related macular degeneration. Arch Ophthalmol. 2008 Jul;126(7):941-5.
  8. Gharbiya M, Allievi F, Mazzeo L, et al; Intravitreal bevacizumab treatment for choroidal neovascularization in pathologic myopia: 12-month results. Am J Ophthalmol. 2009 Jan;147(1):84-93.e1. Epub 2008 Sep 6.
  9. Ohno-Matsui K, Yoshida T; Myopic choroidal neovascularization: natural course and treatment. Curr Opin Ophthalmol. 2004 Jun;15(3):197-202.
  10. Ruiz-Moreno JM, Amat P, Montero JA, et al; Photodynamic therapy to treat choroidal neovascularisation in highly myopic patients: 4 years' outcome. Br J Ophthalmol. 2008 Jun;92(6):792-4.
  11. Panozzo G, Mercanti A; Vitrectomy for myopic traction maculopathy. Arch Ophthalmol. 2007 Jun;125(6):767-72.
  12. Bottoni F, Perego E, Airaghi P, et al; Surgical removal of subfoveal choroidal neovascular membranes in high myopia. Graefes Arch Clin Exp Ophthalmol. 1999 Jul;237(7):573-82.
  13. Uemura A, Thomas MA; Subretinal surgery for choroidal neovascularization in patients with high myopia. Arch Ophthalmol. 2000 Mar;118(3):344-50.
  14. Shimada N, Ohno-Matsui K, Yoshida T, et al; Development of macular hole and macular retinoschisis in eyes with myopic choroidal neovascularization. Am J Ophthalmol. 2008 Jan;145(1):155-161. Epub 2007 Nov 7.
  15. Hampton GR, Kohen D, Bird AC; Visual prognosis of disciform degeneration in myopia. Ophthalmology. 1983 Aug;90(8):923-6.
  16. Tabandeh H, Flynn HW Jr, Scott IU, et al; Visual acuity outcomes of patients 50 years of age and older with high myopia and untreated choroidal neovascularization. Ophthalmology. 1999 Nov;106(11):2063-7.
Original Author: Dr Olivia Scott Current Version:
Last Checked: 23/05/2011 Document ID: 2166  Version: 22 © EMIS

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