Focal scleral nodule is characterized by which underlying pathological process?

Granulomatous inflammation of the sclera and/or choroid FSN is a granulomatous inflammatory reaction in the sclera and/or choroid arising in the absence of any underlying systemic inflammatory disease.

Reactive proliferation of retinal pigment epithelium

Metastatic deposit from a distant primary carcinoma

Calcium deposition within the outer scleral lamellae

Focal scleral nodule was previously described in the literature under which names?

Solitary idiopathic choroiditis and unifocal helioid choroiditis The entity now called focal scleral nodule was formerly termed solitary idiopathic choroiditis and unifocal helioid choroiditis.

Punctate inner choroidopathy and MEWDS

Posterior scleritis and scleromalacia perforans

Birdshot and serpiginous choroidopathy

Focal scleral nodule is most commonly found in which patient group?

White females aged 20 to 50 FSN is a rare condition encountered most often in white females between the ages of 20 and 50.

Approximately what proportion of patients with focal scleral nodule are asymptomatic at diagnosis?

About one third Roughly a third of patients with FSN have no symptoms when the lesion is first identified.

What did optical coherence tomography reveal about the anatomic origin of focal scleral nodule?

It arises from the sclera rather than the choroid OCT changed the understanding of this lesion by showing its origin lies in the sclera, not the choroid as previously described.

It arises from the retinal pigment epithelium

It arises from the inner retinal layers

It arises from retrobulbar orbital fat

What is the recommended management of an inactive focal scleral nodule?

Monitoring without treatment Inactive lesions are simply monitored; systemic corticosteroids are reserved as a possible trial for lesions that appear active.

A course of systemic corticosteroids

What accounts for the orange halo seen around a focal scleral nodule on fundoscopy?

Thinning or absence of the overlying choroid The choroid overlying an FSN is usually thinned or absent, and this is the likely cause of the orange halo seen on fundus examination.

Lipofuscin accumulation in the overlying retina

Serous fluid tracking under the sensory retina

Dilated choroidal vessels encircling the lesion

What do OCT angiography and autofluorescence typically show in focal scleral nodule?

An avascular lesion that is hyperautofluorescent OCT angiography shows FSN lesions to be avascular, and most demonstrate hyperautofluorescence.

A vascular lesion that is hypoautofluorescent

A vascular lesion that is hyperautofluorescent

An avascular lesion with no autofluorescence signal

What is the current view on systemic disease associations in focal scleral nodule?

Tuberculosis is a confirmed causative agent

Sarcoidosis is present in most diagnosed patients

Syphilis serology is diagnostic in active lesions

Why must focal scleral nodule be diagnosed with certainty before a patient is discharged from follow-up?

Choroidal metastasis or melanoma can look similar Several dangerous lesions mimic FSN, and mistaking a choroidal metastasis or melanoma for a benign FSN could be disastrous.

Active lesions always need long-term oral steroids

The nodule enlarges predictably without treatment

Scleral perforation follows if monitoring is stopped

Focal Scleral Nodule (FSN): The Eye's Enigmatic Visitor

CASE REPORT

A 45-year-old male presented to an ophthalmology clinic with complaints of discomfort, redness, and a raised lesion on the sclera of his right eye, which had been bothering him for the past six weeks.

His medical history was unremarkable, with no prior ocular or systemic conditions, and he denied any history of trauma to the eye or exposure to irritants.

Initial examination revealed 20/20 visual acuity in both eyes, localized conjunctival injection, and a raised, pinkish-white nodule on the inferonasal quadrant of the right eye’s sclera, while the left eye showed no abnormalities.

Slit-lamp biomicroscopy confirmed the presence of a well-defined, non-mobile nodule on the sclera, with intact overlying conjunctiva and clear cornea and anterior chamber.

Intraocular pressure was within normal limits in both eyes, and fundus examination revealed no signs of pathology. Differential diagnoses included focal scleritis, scleral nodule of unknown origin, scleral tumor, and pterygium.

Further investigations, such as ultrasound biomicroscopy, laboratory tests, and a scleral nodule biopsy, were performed to establish the diagnosis, which confirmed the Focal Scleral Nodule (FSN).

Focal Scleral Nodule (FSN) DISEASE entity

A focal Scleral Nodule (FSN), previously referred to as solitary idiopathic choroiditis (SIC) and unifocal helioid choroiditis, is characterized by an inflammatory granulomatous reaction in the sclera and/or choroid in the absence of an underlying systemic inflammatory disease.

It is a rare condition found more commonly in white females between the ages of 20 and 50 and where approximately a third of patients are asymptomatic at the time of diagnosis. Current management recommendations of FSN suggest monitoring of inactive lesions and either close observation or treatment with systemic corticosteroids for active lesions.

Risk factors remain poorly understood likely due to the poor understanding of the pathogenesis. Several associations have been suggested including associations with systemic diseases such as tuberculosis, syphilis, sarcoidosis, cat scratch disease, and coxsackie virus.

However, this remains unclear and has been challenged in recent literature; no significant relation with these systemic conditions has been found.

Optical coherence tomography (OCT) has led to a new understanding of Focal Scleral Nodule (FSN) including the anatomic origin in the sclera vs. the choroid as previously described. Most lesions have been revealed to have a dome shape, but nodular or volcanic shapes have also been noted.

The overlying choroid usually shows thinning or absence and is the likely cause of the orange halo seen on the fundoscopic exam. OCT angiography will show the lesions to be avascular and most will demonstrate hyperautofluorescence.

Test your knowledge 10 questions from this article

Focal Scleral Nodule (FSN) Differential diagnosis

Many lesions have a somewhat similar presentation to FSN. Some of these are benign while others may indicate a more urgent or dangerous disease.

A thorough exam and imaging are important to differentiate these lesions and many can be ruled out with OCT showing a scleral lesion vs. a lesion arising from the choroid.

The following lesions may present similarly:

Choroidal metastasis
Choroidal melanoma
Choroidal lymphoma
Retinoblastoma
Astrocytic hamartoma
Choroidal nevus
Choroidal granuloma
Choroidal scars
White dot syndromes
Sarcoidosis
Ocular tuberculosis
Ocular syphilis
Fungal chorioretinitis
Sclerchoroidal calcification

Focal Scleral Nodule (FSN) MANAGEMENT

When followed over time most lesions remain stable without changes. Nevertheless, there are reports of lesions that demonstrate growth or resolution with long-term follow-up.

Due to the benign nature and limited functional impact of an FSN, no treatment is indicated in most cases. In the event that a lesion does appear to be active with associated inflammation, systemic steroids have been suggested as a possible trial treatment.

However, there have been no studies evaluating the overall effectiveness of this treatment. Active lesions can respond favorably with or without steroid treatment.

Regardless, due to the potential danger of similar-looking lesions, it is imperative to correctly diagnose an FSN prior to informing a patient that they do not need follow-up care.

The potential erroneous diagnosis of an FSN in place of a choroidal metastasis or melanoma could be disastrous.

REFERENCES

Hong PH, Jampol LM, Dodwell DG, Hrisomalos NF, Lyon AT. Unifocal helioid choroiditis. Arch Ophthalmol. 1997 Aug;115(8):1007-13.
Shields JA, Shields CL, Demirci H, Hanovar S. Solitary Idiopathic Choroiditis: The Richard B. Weaver Lecture. Arch Ophthalmol. 2002;120(3):311–319.
Fung AT, Kaliki S, Shields CL, Mashayekhi A, Shields JA. Solitary idiopathic choroiditis: findings on enhanced depth imaging optical coherence tomography in 10 cases. Ophthalmology. 2013;120:852–858
Fung AT, Waldstein SM, Gal-Or O, Pellegrini M, Preziosa C, Shields JA, Welch RJ, Dolz-Marco R, Sarraf D, Nagiel A, Lalane R, Jung JJ, Ghazi NG, Ramtohul P, Arnold JJ, Sakurada Y, Choudhry N, Balaratnasingam C, Freund KB, Shields CL. Focal Scleral Nodule: A New Name for Solitary Idiopathic Choroiditis and Unifocal Helioid Choroiditis. Ophthalmology. 2020 Nov;127(11):1567-1577.
Goyal S, Ware GT, Petrovic’ V. Coxsackie virus a possible missing link to unifocal helioid choroiditis? Clin Exp Ophthalmol. 2015 May-Jun;43(4):377-9.
Kumar V, Khoo CT, Shields CL. Solitary idiopathic choroiditis in the setting of extensive animal exposure. Retin Cases Brief Rep. 2016 Fall;10(4):386-8.
Feng Y, Conrady CD, Demirci H. The evolution of an active solitary idiopathic choroiditis (focal scleral nodule): a case report of the natural course and a review of the literature. BMC Ophthalmol. 2021;21(1):130. Published 2021 Mar 9. doi:10.1186/s12886-021-01888-5.

Test yourself

A few questions straight from this article.

1 / 10 0 correct

Focal scleral nodule is characterized by which underlying pathological process?
FSN is a granulomatous inflammatory reaction in the sclera and/or choroid arising in the absence of any underlying systemic inflammatory disease.
Focal scleral nodule was previously described in the literature under which names?
The entity now called focal scleral nodule was formerly termed solitary idiopathic choroiditis and unifocal helioid choroiditis.
Focal scleral nodule is most commonly found in which patient group?
FSN is a rare condition encountered most often in white females between the ages of 20 and 50.
Approximately what proportion of patients with focal scleral nodule are asymptomatic at diagnosis?
Roughly a third of patients with FSN have no symptoms when the lesion is first identified.
What did optical coherence tomography reveal about the anatomic origin of focal scleral nodule?
OCT changed the understanding of this lesion by showing its origin lies in the sclera, not the choroid as previously described.
What is the recommended management of an inactive focal scleral nodule?
Inactive lesions are simply monitored; systemic corticosteroids are reserved as a possible trial for lesions that appear active.
What accounts for the orange halo seen around a focal scleral nodule on fundoscopy?
The choroid overlying an FSN is usually thinned or absent, and this is the likely cause of the orange halo seen on fundus examination.
What do OCT angiography and autofluorescence typically show in focal scleral nodule?
OCT angiography shows FSN lesions to be avascular, and most demonstrate hyperautofluorescence.
What is the current view on systemic disease associations in focal scleral nodule?
Associations with tuberculosis, syphilis, sarcoidosis, cat scratch disease and coxsackie virus have been suggested, but recent literature has found no significant relation.
Why must focal scleral nodule be diagnosed with certainty before a patient is discharged from follow-up?
Several dangerous lesions mimic FSN, and mistaking a choroidal metastasis or melanoma for a benign FSN could be disastrous.

Focal Scleral Nodule (FSN): The Eye’s Enigmatic Visitor