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Editors Selection IGR 16-4
Prognostic Factors: IOP fluctuations and Visual Field Progression in Normal-Tension Glaucoma
Comment by Kaweh Mansouri & Julien Torbey on:
96190 Impact of intraocular pressure fluctuations on progression of normal tension glaucoma, Hopf S; Schwantuschke D; Schmidtmann I et al., International Journal of Ophthalmology, 2021; 14: 1553-1559
This article tackles the controversial topic of IOP fluctuations in normal tension glaucoma. While IOP variability has been described as a risk factor in several glaucoma subsets, its association remains unclear in Normal Tension Glaucoma.
Based on a long-term retrospective study, the authors concluded that short term and long term IOP fluctuations do not result in progression of NTG. The role of IOP remains highly debated, with authors arguing that the atypical presentation of NTG falls within the optic neuropathy spectrum, being independent of eye-pressure. On the other hand, the collaborative normal tension glaucoma study demonstrated a clear benefit of lowering IOP on disease progression.1,2
By omitting measurements from 12am to 8am in the study protocol, valuable data have been missed, potentially underestimating true IOP range, hence fluctuation3
Numerous studies demonstrated IOP to peak early in the morning. By omitting measurements from 12am to 8am in the study protocol, valuable data have been missed, potentially underestimating true IOP range, hence fluctuation.3 Goldmann applanation devices, despite being the gold standard and widely used, have inter-user variability measurements which could affects the accuracy and repeatability of the results. Furthermore, spot 48-hours IOP profiles carried infrequently are hardly representative of true short and long-term fluctuations.4 It is also unclear exactly how many IOP profiles have been carried on each subject and the time frame between them (minimum 6 months between 48 hours according to the authors). Such key limitations could be overcome by using telemetric measuring devices. The ARGOS-2 Trial study using the eyemate sensor have already demonstrated significant short and long term fluctuations, demonstrating the need for continuous IOP measurements in glaucoma management and research.5
It is worth noting that the study's recommendation to rely mostly on visual fields to monitor NTG patients is sound and corroborates previous studies. Atypical visual field defects closer to the center of fixation are considered a hallmark of the disease and a good marker of progression.
The lack of clear association to progression in NTG in addition to a lack of consensus between studies is a testament to the complex pathophysiology of this disease that is yet to be fully understood.
References
- The effectiveness of intraocular pressure reduction in the treatment of normaltension glaucoma. Am J Ophthalmol.. 1998;126(4):498-505. doi:10.1016/S0002-9394(98)00272-4
- Leung DYL, Tham CC. Normal‐tension glaucoma: Current concepts and approaches‐A review. Clin Exp Ophthalmol. Published online February 7, 2022. doi:10.1111/ceo.14043
- Sood V, Ramanathan US. Self-monitoring of intraocular pressure outside of normal office hours using rebound tonometry: Initial clinical experience in patients with normal tension glaucoma. J Glaucoma. 2016;25(10):807-811. doi:10.1097/IJG.0000000000000424
- Realini T, Weinreb RN, Wisniewski SR. Diurnal intraocular pressure patterns are not repeatable in the short term in healthy individuals. Ophthalmol. 2010;117(9):1700-1704. doi:10.1016/j.ophtha.2010.01.044
- Choritz L, Mansouri K, van den Bosch J, et al. Telemetric measurement of intraocular pressure via an implantable pressure sensor‐12-month results from the ARGOS-02 trial. Am J Ophthalmol. 2020;209:187-196. doi:10.1016/j.ajo.2019.09.011
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