Vision Therapy for Straatsma Syndrome

Indira Rengarajan, B. Optom

M.Optom, The Sankara Nethralaya Academy, Chennai, India

 

Introduction:

Clinically Straatsma syndrome is a triad of Myelinated Retinal Nerve Fiber (MRNF), Myopia, and amblyopia, which can have additional associations such as strabismus, nystagmus, hypoplastic optic nerve, and heterochromia iridum.

There is another variant of this rare condition in which myopia is replaced by hyperopia and it is termed reverse Straatsma syndrome. Initially, it was described by Straatsma et al. in the year 1979.⁽¹⁾

MRNF:

MRNF is often congenital and consists of white or grey-white well-defined patches on the outermost surface of the retina that obscure the underlying retinal vessels. They are rare lesions that occur in approximately 1% of the population and can have associated ocular and systemic abnormalities.⁽²⁾

A Visual function can be affected depending on its location, extent of myelination, and coexisting visual pathology.⁽²⁾

Studies state that myelination starts during the 5^th month of pregnancy and ends before birth, where Lamina cribrosa serves as a barrier for myelination. Disruption of this lamina is responsible for the presence of myelin fibres.^(3,4)

Among all populations with myelin fibres, Straatsma is responsible for only 0.3-10% of cases.⁽³⁾

Pathogenesis:

There are controversial reports for the mechanism of development of myopia where Moradian states that an eye with long axial length will have a slow development of the lamina cribrosa which could generate an anomalous functional barrier, allowing for myelination whereas Straatsma suggests that the presence of myelin fibres in crucial phase on ocular development that interferes in image acquisition, generating a visual privation and consequently an increased axial length.⁽³⁾

Amblyopia occurs because of either of the mechanism which includes structural defect due to myelin fibres, a refractive defect due to anisometropia or may be due to strabismus component.⁽³⁾

Treatment:

• Ametropic correction – Early detection and treatment of the condition and its associated ocular pathology. Spectacles or contact lenses will be beneficial.
• Amblyopia treatment – Challenging part in the management of Straatsma in treating amblyopia. A Higher degree of anisometropia will result in poor post treatment visual acuity outcomes. The Gold standard treatment option is occlusion of the sound eye, which is beneficial in low degrees of anisometropia.
• Vision therapy (VT) – VT plays a vital role in improving Visual Acuity (VA). Along with patching, exercises that stimulate the amblyopic eye will enhance the VA.
  • – Haidinger’s brushes that are based on entopic phenomenon can be performed during patching for stimulation.
  • – Amblyopia INet is a home-based software therapy to treat amblyopia patients.
  • – Sanet Vision Integrator (SVI) is an office-based vision software that includes various tasks to improve visual abilities such as pursuits, saccades, fixation disparity, eye-hand coordination, visual reaction time, speed, and span of recognition, etc… This allows us to change parameters such as stimulus size, speed, and contrast.

Conclusion:

Aggressive amblyopia therapy and ametropic correction during the early stage will have good results.

 

References:

1. Sevik, M. O., Aykut, A., Karaman, N. F., & Şahin, Ö. (2021). Straatsma Syndrome: Should Visual Prognostic Factors Be Taken into Account? A Case Report. Turkish Journal of Ophthalmology, 51(6), 398.
2. Ramkumar, H. L., Verma, R., Ferreyra, H. A., & Robbins, S. L. (2018). Myelinated retinal nerve fiber layer (RNFL): a comprehensive review. International ophthalmology clinics, 58(4), 147-156.
3. Gameiro, A. R., Gameiro, R. R., & Medina, F. M. C. (2020). Straatsma syndrome. Revista Brasileira de Oftalmologia, 79, 66-68.
4. Jain, M., Sharon, J. M., Anjanamurthy, R., & Wijesinghe, H. K. (2021). Straatsma syndrome: unilateral myelinated retinal nerve fibre layer, high myopia, strabismus and amblyopia. BMJ Case Reports CP, 14(6), e244362.