The task of diagnosing normal-tension glaucoma can be challenging and illusive. I have debated (and ultimately argued for) its very existence in lecture presentations.
To me, the most challenging aspect of making this diagnosis is separating it from two significant differential diagnoses: primary open-angle glaucoma (sometimes referred to for the sake of comparison as “high-tension” glaucoma) and prior insult to the optic nerve, which is non-progressive.
As far as its distinction from “high-tension” glaucoma is concerned, my diagnostic capabilities are precluded by my office hours.
Previously by Dr. Casella: Maintain open communication with primary-care physicians
Simply put, there is a great deal of time between the hours of 5 p.m. and 9 a.m. for intraocular pressure (IOP) to spike, and I am sure that I am missing a number of my patients’ highest IOPs.
If I never record an IOP outside of so-called “normal” ranges on a glaucoma patient prior to the initiation of treatment—and subsequently make a diagnosis of normal-tension glaucoma—I am technically wrong if the patient’s IOPs are in the mid-20s three hours before his appointment time.
Although this really does not affect my plan—which is typically to initiate treatment with a prostaglandin analog—the semantics of the whole thing bother me.
On the other hand, all ODs learned in optometry school that glaucoma is progressive by nature and by definition. Couple that with the fact that non-progressive conditions may likely not require treatment, and it becomes readily apparent that the prudent course of action in a glaucoma suspect without ocular hypertension may be to check for progression before treating.
If I am unsure, then I may decide to obtain a few sequential visual studies and optical coherence tomography (OCT) studies before initiating treatment.
Related: Blog: 4 uses for OCT in OD practices
1. Bron A. Ocular hypertension and glaucoma: the contribution of large studies to daily practice. J Fr Ophtalmol. 2002 Jun;25(6):641-54.
2. Baek SU, Ha A, Kim DW, Jeoung JW, Park KH, Kim YK. Risk factors for disease progression in low-teens normal-tension glaucoma. Br J Ophthalmol. 2019 May 4. doi: 10.1136/bjophthalmol-2018-313375.