Optometry case study: Normal-tension glaucoma

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Figure 1. 3D wide report of RE showing RNFL and GCL thinning

By Tyson Xu, Specsavers Nowra, NSW

History

Px: 82-year-old Caucasian female
Reason for visit: Noticed her RE wasn’t as clear as her LE, even with optical correction from a year ago
GH: Controlled hypertensive and migraine sufferer
Meds: Multiple, but no steroidal medication
POH: Bilateral pseudophakia for the last 6 years. Was initially diagnosed at the time with glaucoma by the ophthalmologist but was lost to follow up
FOH: No history of glaucoma

Clinical Assessment

BCVA: RE: Plano/-0.75×100 (6/7.5-1)    LE: +0.25/-1.00×80 (6/6)
Pupils: PERRL no RAPD
IOP: RE: 11mmHg           LE: 11mmHg @ 11:10am

Pachymetry: RE: 474µm and LE: 495µm

Anterior eye:

  • Angles open
  • No signs of pigment dispersion or pseudoexfoliation syndrome
  • Intraocular lens clear and central

Dilated fundus examination:

  • Maculae flat with no evidence of epiretinal membrane nor vitreomacular traction
  • Right optic nerve: Focal rim thinning inferiorly (notch) with correlating retinal nerve fibre layer (RNFL) wedge defect and thinning of ganglion cell layer (GCL) inferiorly (Figure 1)
  • Left optic nerve: RNFL and GCL within normal limits (Figure 2)
  • OCT 3D disc analysis showing marked disc asymmetry (Figure 3)

Automated perimetry (Medmont M600 Glaucoma module):

  • Repeatable paracentral visual field defect in the RE in the superior nasal quadrant – this correlates to the inferior temporal thinning of the ganglion cell layer (Figures 4 and 5)

Amsler grid:

  • Absolute scotoma superonasal to fixation in the RE. LE normal

Diagnosis & Management

Differential diagnosis:

  • Normal-tension glaucoma
  • Secondary open-angle glaucoma
  • Angle-closure glaucoma
  • Physiological disc asymmetry
  • Optic atrophy

Diagnosis: Normal-tension glaucoma

Management:

  • Patient was advised that the RE’s central vision wasn’t as good due to the absolute scotoma caused by loss of ganglion cells from glaucoma.
  • Patient was referred to a local glaucoma specialist for management as well as to Glaucoma Australia to help facilitate understanding and encourage compliance with treatment and reviews.
  • She was also advised to encourage her family members to get their eyes checked.

Discussion

Normal-tension glaucoma (NTG) is a form of primary open-angle glaucoma in which IOP is less than 21mmHg and is one of the most common forms of glaucoma in Australia, Japan, Western Europe and the US1-2. Compared to other forms of glaucoma, NTG has a relatively slower average rate of progression with reported mean deviation visual field loss of 0.36dB-0.41dB / year as opposed to 3.13dB / year in pseudoexfoliative glaucoma and 1.31dB / year in hypertensive glaucoma3-4. However, NTG visual field defects tend to be more localised, dense and closer to fixation5-8. In this patient’s case, it has affected her central vision in the RE, and she is now symptomatic.

Risk factors for progression of VF defects include female gender, migraines and disc haemorrhages9. Disc haemorrhages are also very characteristic of NTG as well as inferotemporal rim thinning and notching10.

Since ophthalmological assessment, the patient’s IOP has been controlled with prostaglandin analogue eyedrops (Xalatan, latanoprost 0.005%) and she is being reviewed on a six-monthly basis.


REFERENCES

  1. Weinreb R, Leung C, Crowston J, Medeiros F, Friedman D, Wiggs J et al. Primary open-angle glaucoma. Nature Reviews Disease Primers. 2016;2:16067.
  2. Iwase A, Suzuki Y, Araie M, Yamamoto T, Abe H, Shirato S et al. The prevalence of primary open-angle glaucoma in Japanese The Tajimi Study. Ophthalmology. 2004;111(9):1641-1648.
  3. Heijl A, Bengtsson B, Hyman L, Leske M. Natural History of Open-Angle Glaucoma. Ophthalmology. 2009;116(12):2271-2276.
  4. Anderson D, Drance S, Schulzer M. Natural history of normal-tension glaucoma. Ophthalmology. 2001;108(2):247-253.
  5. Caprioli J, Spaeth G. Comparison of the Optic Nerve Head in High- and Low-Tension Glaucoma. Archives of Ophthalmology. 1985;103(8):1145-1149.
  6. Thonginnetra O, Greenstein V, Chu D, Liebmann J, Ritch R, Hood D. Normal Versus High Tension Glaucoma. Journal of Glaucoma. 2010;19(3):151-157.
  7. Caprioli J, Spaeth G. Comparison of Visual Field Defects in the Low-Tension Glaucomas with Those in the High-Tension Glaucomas. American Journal of Ophthalmology. 1984;97(6):730-737.
  8. Araie M. Pattern of visual field defects in normal-tension and high-tension glaucoma. Current Opinion in Ophthalmology. 1995;6(2):36-45.
  9. Drance S, Anderson D, Schulzer M. Risk factors for progression of visual field abnormalities in normal-tension glaucoma. American Journal of Ophthalmology. 2001;131(6):699-708.
  10. Woo S. Comparison of localised nerve fibre layer defects in normal tension glaucoma and primary open angle glaucoma. British Journal of Ophthalmology. 2003;87(6):695-698.
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