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Editors Selection IGR 25-1
Risk Factors: Unaffeceted eyes of unilateral NTG patients: Beware!
Comment by Hitomi Saito on:
121632 Rapid Retinal Nerve Fiber Layer Thinning in the Unaffected Contralateral Eyes of Patients with Unilateral Normal-Tension Glaucoma: A Retrospective Observational Study, Song JE; Song JE; Song JE; Lee EJ; Kim TW, Ophthalmology. Glaucoma, 2024; 7: 431-439
This study by Song JE et al. compared the rates of retinal nerve fiber layer (RNFL) thinning over a four-year period among eyes with unilateral normal tension glaucoma (NTG), their contralateral unaffected eyes, and healthy control eyes. The findings revealed that the untreated contralateral eyes exhibited a faster rate of RNFL thinning compared to the healthy controls, while their thinning rate was comparable to that of the medically treated NTG eyes. Additionally, a worse baseline visual field mean deviation (VF-MD) and a thicker baseline RNFL were associated with more rapid RNFL thinning in the contralateral unaffected eyes.
“….healthy contralateral eyes in patients with unilateral NTG are at significant risk of structural progression. As such, prophylactic treatment should be considered for these eyes”
These results highlight that the seemingly healthy contralateral eyes in patients with unilateral NTG are at significant risk of structural progression. As such, prophylactic treatment should be considered for these eyes. Notably, although worse baseline VF-MD in the NTG eye correlated with faster progression in the contralateral eye, the average VF-MD in NTG eyes whose contralateral eye progressed to glaucoma during the study period was -5.58 dB. This suggests that prophylactic treatment should not be dismissed solely based on the NTG eye not appearing to be in an advanced stage.
While the study provides valuable insights into the management of unilateral NTG, certain limitations should be acknowledged. First, only the NTG eyes received medical treatment, while the contralateral eyes did not. This treatment disparity may have obscured differences in natural disease progression between the NTG and contralateral eyes. Nevertheless, the contralateral eyes still showed faster RNFL thinning than the healthy controls, indicating an intrinsic susceptibility of the contralateral eyes to progression.
Second, the observed association between thicker baseline RNFL and faster thinning should be interpreted with caution. The study population largely comprised early-stage NTG eyes (mean MD of -2.92 dB), in which structural changes are typically more detectable than functional ones. RNFL thinning may have been more easily observed in eyes with initially thicker RNFL, and this characteristic alone may not necessarily predict future progression.
Third, given that NTG progression is generally slow, a longer follow-up period and a more comprehensive assessment—including factors such as disc hemorrhage, deep optic nerve head morphology, and systemic conditions—are required to fully understand the true risk factors for progression in the contralateral, clinically unaffected eyes of unilateral NTG patients.
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