Optometry case study: A swirly case of bilateral X-linked retinoschisis

349
Figure 1. RE OCT fundus photography

By Jerome Vongsaphay, Specsavers Nowra, NSW

History

Px: 18-year-old male who works as an electrician
Reason for visit: 
Symptoms of increased asthenopia with spectacles and new onset nystagmus. No nyctalopia, hemeralopia or photophobia
GH: 
No health issues 
POH: 
History of mildly impaired vision of unknown aetiology. Eight years prior to presentation, corneal topography was arranged to investigate this issue, however the patient was lost to follow-up
FOH: 
No relevant issues

Clinical Assessment

Unaided vision: RE: 6/120             LE: 6/120
Pupils:
 PERRLA
Ocular motilities:
 Horizontal jerk nystagmus exacerbated on temporal gaze
Visual field:
 Within normal limits 
Colour vision (Ishihara 24 plate 1993 ed.):
 No errors

Refraction:
Vision with spectacles two years prior to presentation:
RE: +2.25/-3.75×95 (6/18)             LE: +2.50/-4.00×90 (6/12-2)

Cyclopentolate refraction:
RE: +2.50/-3.50×90 (6/18+2)        LE: +2.25/-3.75×88 (6/12+2), PHNI

Anterior eye: No abnormalities detected

Posterior eye: Large, swirly, radial striations at the macula, more prominent in the RE than in the LE (Figures 1 and 2). OCT scans revealed signs of inner retinal cystic spaces and marked foveal contour line disorganisation (Figures 3 and 4). Optic nerves and peripheral retinas were normal.

Diagnosis

Differential diagnosis:

  • X-linked retinoschisis
  • Cystoid macular oedema
  • Retinitis pigmentosa
  • Bilateral amblyopia

Discussion

X-linked retinoschisis (XLRS) is the leading cause of juvenile macular degeneration in males and is characterised by inner retinal schisis. Population-based studies have reported the prevalence of XLRS as ranging from 1 in 15,000 to 1 in 30,000, predominantly affecting males earlier in life1,2.

Pathogenically, XLRS is understood to be due to mutations in the RS1 gene, a gene that provides instructions for making a protein called retinoschisin. This gene mutation causes disorganisation of functional retinoschisin (i.e. schisis)2.

Clinical presentation usually involves young males for evaluation of bilaterally reduced VAs without acute vision loss2. Hyperopia is a frequent finding, and other possible findings include strabismus, nystagmus, vitreous haemorrhage and retinal detachment1-3.

The hallmark clinical finding is the presence of spoke-wheel striae radiating from the macula seen on high-magnification funduscopic examination. The striae pattern varies in severity and is challenging to detect in younger patients with limited cooperation.

As shown in this case, OCT has changed the diagnostic approach for XLRS. A single scan of the foveal area is sufficient to detect signs of XLRS, even in uncooperative patients3. Fundus autofluorescence, fluorescein angiography and electroretinogram are used less frequently in the diagnosis of XLRS due to the variability in their results, but are still useful in ruling out differential diagnoses3.

Management

Given the sensitive nature of the diagnosis of retinal degenerative eye conditions, it was deemed appropriate to refer the patient to an ophthalmologist for diagnosis, treatment and counselling. The role of the optometrist in ongoing management is to provide optimum refractive correction, assess low-vision services and address suitability to drive. Examination of family members is recommended.

The ophthalmologist initiated empirical treatment with topical carbonic anhydrase inhibitor (Trusopt, dorzolamide hydrochloride, 2% 5mL), which has been shown to aid resolution of the cystic spaces seen on OCT4,5.

This case highlights the importance of funduscopic examination and applicable OCT utilisation for the diagnosis and management of XLRS.


REFERENCES

  1. Sikkink SK, Biswas S, Parry NRA, Stanga PE, Trump D. X-linked retinoschisis: an update. Journal of medical genetics. 2007;44(4):225-32.
  2. Molday RS, Kellner U, Weber BHF. X-linked juvenile retinoschisis: Clinical diagnosis, genetic analysis, and molecular mechanisms. JPRR Progress in Retinal and Eye Research. 2012;31(3):195-212.
  3. Dhingra S, Patel CK. Diagnosis and Pathogenesis of Congenital X-Linked Retinoschisis with Optical Coherence Tomography. J Pediatr Ophthalmol Strabismus Journal of Pediatric Ophthalmology & Strabismus. 2010;47(2):105-7.
  4. Apushkin MA, Fishman GA. Use of dorzolamide for patients with X-linked retinoschisis. Retina Retina. 2006;26(7):741-5.
  5. Zhang L, Reyes R, Lee W, Chen C-L, Chan L, Sujirakul T, et al. Rapid resolution of retinoschisis with acetazolamide. Doc Ophthalmol Documenta Ophthalmologica : The Journal of Clinical Electrophysiology and Vision – The Official Journal of the International Society for Clinical Electrophysiology and Vision. 2015;131(1):63-70.
Print