What is the classic triad of Straatsma syndrome?

Myelinated nerve fibres, axial myopia and amblyopia Straatsma syndrome is characterised by the traditional triad of unilateral myelinated retinal nerve fibres, axial myopia and amblyopia.

Optic disc drusen, hyperopia and strabismus

Retinal coloboma, cataract and nystagmus

Macular scar, astigmatism and ptosis

Which additional feature was part of the original description of Straatsma syndrome?

Strabismus The original description of the condition also included strabismus alongside the myelinated fibres, myopia and amblyopia.

What defines the variant known as reverse Straatsma syndrome?

Hyperopia instead of myopia In reverse Straatsma syndrome patients show hyperopia rather than the myopia of the traditional triad.

Bilateral rather than unilateral disease

Myelination that spares the optic disc

What is the typical laterality of Straatsma syndrome?

Always strictly bilateral in reported cases

Alternating between the two eyes over time

Confined to the non-dominant eye only

How do myelinated retinal nerve fibres typically appear on fundus examination?

A pigmented patch with sharp scalloped edges

A yellow subretinal deposit with overlying fluid

An orange elevated mass flecked with lipofuscin

Which anatomical boundary do myelinated retinal nerve fibres respect?

The horizontal raphe Myelinated retinal nerve fibres follow the nerve fibre layer and do not cross the horizontal raphe, although they may lie separate from the disc or in the periphery.

The vertical midline of the disc

What does management of Straatsma syndrome consist of?

Refractive correction and ruling out systemic associations Management centres on providing proper refractive correction and on ruling out systemic associations, rather than on any retinal intervention.

Laser ablation of the myelinated fibres

Long-term topical atropine to the fellow eye

Vitrectomy with internal limiting membrane peel

How does amblyopia in Straatsma syndrome compare with anisometropic amblyopia without myelination?

It has a poorer prognosis and resists occlusion therapy Amblyopia associated with myelinated nerve fibres and anisometropia carries a poorer prognosis and is refractory to occlusive therapy, though rehabilitation should still be attempted.

It responds faster to patching of the fellow eye

It carries an essentially identical visual prognosis

It improves without any refractive correction

Straatsma Syndrome: Key Signs and Management

DISEASE

Straatsma syndrome is a rare disease entity characterized by the traditional triad of unilateral myelinated retinal nerve fibers (MNRF), axial myopia, and amblyopia.

The original description of the condition also included strabismus. Variations of the triad include a “reverse Straatsma syndrome ”, in which patients exhibit hyperopia instead of myopia.

Even though nystagmus and strabismus have not been prominently associated with Stratsma syndrome, either may be present as complimentary findings without precluding one from the diagnosis.

Even though Straatsma syndrome has traditionally been considered a unilateral disorder, cases of bilateral Straatsma syndrome and bilateral reverse Straatsma syndrome have also been reported.

Diagnosis

MRNF appears as a white lesion usually contiguous with the optic nerve head. The distribution is along the retinal nerve fiber layer and typically feather-like appearance is noted at the margin.

The MRNF does not cross the horizontal raphe. MRNF may be separate from the optic disc and may be present in the peripheral retina.

Despite some controversy in its diagnostic features, it should be included in the differential diagnosis of leukocoria and must be suspected in the presence of refractive errors with anisometropia.

Test your knowledge 9 questions from this article

Clinical Features of Straatsma Syndrome

Normally, myelination of the optic nerve stops at the lamina cribrosa. In myelinated retinal nerve fibers, however, the oligodendrocytes continue past the lamina and coat part of the nerve fiber layer. The change is present in well under 1% of eyes, and most affected people never notice it. Straatsma syndrome is the less common situation in which the patches coexist with refractive and amblyopic disease in the same eye.

The affected eye is usually the more myopic one, and the myopia is axial. Therefore, the child often comes to attention through a failed vision screening or a lazy eye rather than any complaint. Because the myelinated patch blocks light, a small scotoma may be present, but it rarely explains the full loss of acuity. In most children, the anisometropia drives the amblyopia (see anisometropia and amblyopia).

Differential Diagnosis of a White Retinal Patch

A white lesion near the disc raises several questions, and the feathery edge is the best clue. Cotton wool spots look similar but have soft margins and fade within weeks. A retinal astrocytic hamartoma is more nodular and may appear in tuberous sclerosis, and a dense patch in a young child can raise concern for retinoblastoma or other causes of leukocoria. In contrast, myelinated fibers follow the arcuate fiber pattern, hide the retinal vessels beneath them, and stay stable over time. A broader overview is given in the article on myelinated retinal nerve fibers.

Imaging helps to document the lesion. Optical coherence tomography shows a thickened, hyperreflective nerve fiber layer with shadowing of the tissue beneath it, and a fundus photograph gives a baseline for later comparison. In addition, a visual field test can map the scotoma and confirm that it is small.

MANAGEMENT

The management includes providing proper refractive correction and ruling out systemic associations.

Start with a cycloplegic refraction and prescribe the full correction, since uncorrected anisometropia is the main modifiable cause of the amblyopia. Then add occlusion or atropine penalization of the better eye according to the usual amblyopia protocols. The response is often slower than in simple anisometropic amblyopia, yet some children improve well, as in the small series cited below.

Also, examine the child for systemic associations. Myelinated fibers have been reported with basal cell nevus (Gorlin) syndrome and neurofibromatosis type 1, so a family history and a skin and craniofacial check are reasonable. Finally, no treatment removes the myelination itself, and follow-up is usually yearly, with earlier review if the patch seems to change.

Prognosis

The visual prognosis of amblyopia associated with myelination of retinal nerve fibers and anisometropia is poorer than anisometropic amblyopia without myelination.

Straatsma syndrome

It is well known that the former is refractory to occlusive therapy. Despite having a poor prognosis, visual rehabilitation should be attempted.

REFERENCES

Juhn, A. T., Houston, S. K., & Mehta, S. (2015). BILATERAL STRAATSMA SYNDROME WITH NYSTAGMUS. Retinal Cases & Brief Reports, 9(3), 198–200. doi:10.1097/icb.0000000000000137
Straatsma BR, Heckenlively JR, Foos RY, Shahinian JK. Myelinated retinal nerve fibers associated with ipsilateral myopia, amblyopia, and strabismus. Am J Ophthalmol. 1979 Sep;88(3 Pt 1):506-10. doi: 10.1016/0002-9394(79)90655-x. PMID: 484678.
Shenoy R, Bialasiewicz AA, Al Barwani B. Bilateral hypermetropia, myelinated retinal nerve fibers, and amblyopia. Middle East Afr J Ophthalmol 2011;18:65–66
Levy NS, Ernest JT. Retinal medullated nerve fibers. Arch Ophthalmol 1974;91:330–331
Congenital optic disk anomalies [Internet]. W.B. Saunders; 2013 [cited 2021 May 19]. Available from: https://www.sciencedirect.com/science/article/pii/B9780702046919000510
Rosen B, Barry C, Constable IJ. Progression of myelinated retinal nerve fibers. Am J Ophthalmol. 1999 Apr;127(4):471-3. doi: 10.1016/s0002-9394(98)00377-8. PMID: 10218709.
Quezada-Del Cid NC, Zimmermann-Paiz MA, Ordoñez-Rivas AM, Burgos-Elías VY, Marroquin-Sarti MJ. Straatsma syndrome: Satisfactory amblyopia treatment. Report of two cases. Arch Soc Esp Oftalmol. 2018 Jun;93(6):300-302. English, Spanish. doi: 10.1016/j.oftal.2017.12.010. Epub 2018 Feb 15. PMID: 29398227.

Test yourself

A few questions straight from this article.

1 / 9 0 correct

What is the classic triad of Straatsma syndrome?
Straatsma syndrome is characterised by the traditional triad of unilateral myelinated retinal nerve fibres, axial myopia and amblyopia.
Which additional feature was part of the original description of Straatsma syndrome?
The original description of the condition also included strabismus alongside the myelinated fibres, myopia and amblyopia.
What defines the variant known as reverse Straatsma syndrome?
In reverse Straatsma syndrome patients show hyperopia rather than the myopia of the traditional triad.
What is the typical laterality of Straatsma syndrome?
Straatsma syndrome has traditionally been considered a unilateral disorder, though bilateral cases and bilateral reverse cases have been reported.
How do myelinated retinal nerve fibres typically appear on fundus examination?
Myelinated fibres appear as a white lesion usually contiguous with the optic nerve head, distributed along the nerve fibre layer with a feather-like margin.
Which anatomical boundary do myelinated retinal nerve fibres respect?
Myelinated retinal nerve fibres follow the nerve fibre layer and do not cross the horizontal raphe, although they may lie separate from the disc or in the periphery.
Straatsma syndrome should be included in the differential diagnosis of which clinical sign?
Despite controversy over its diagnostic features, Straatsma syndrome belongs in the differential diagnosis of leukocoria and should be suspected with anisometropic refractive error.
What does management of Straatsma syndrome consist of?
Management centres on providing proper refractive correction and on ruling out systemic associations, rather than on any retinal intervention.
How does amblyopia in Straatsma syndrome compare with anisometropic amblyopia without myelination?
Amblyopia associated with myelinated nerve fibres and anisometropia carries a poorer prognosis and is refractory to occlusive therapy, though rehabilitation should still be attempted.