I often recall fondly how one of my mentors, Mitch Dul, OD, FAAO, told me that patients can have “as many diseases as they pleases.” We know this to be the case because we see it every day. We go to continuing education conferences where we see nice tidy cases and think, “I got this! This is easy!” Then, we get back to the office on Monday morning and are inundated with a slew of patients with lurking variables in their eyes and visual systems.
Go beyond the optic nerve
I take comfort in the fact that I know I’m not alone, and a paper published in the Korean Journal of Ophthalmology in October 2019 does well to hammer home the fact that, with respect to glaucoma, clinicians must take into account the rest of the eyeball and not just the optic nerve head.1
This is especially true with retinal nerve fiber layer (RNFL) thickness values as measured by spectral domain optical coherence tomography (SD-OCT).
This retrospective study consisted of a cohort of established glaucoma patients with newly diagnosed epiretinal membranes (ERM): 28 eyes of 28 patients (16 males, 12 females). Of this cohort, 22 patients had primary open-angle glaucoma, three had pseudoexfoliative glaucoma, two had uveitic glaucoma, and one had chronic angle-closure glaucoma. Ages ranged from 44 to 73 years with a mean age of 61 years.
Subjects had SD-OCT studies before and after the onset of ERMs. Humphrey visual fields had also been obtained prior to and after ERM onset. Axial length and central corneal thickness values were also taken into consideration, with a mean axial length of 23.5 mm and a mean central corneal thickness of 542.9 μm. Mean spherical equivalent refractive error was 1.40 D of myopia.
The onset of an ERM lead to a mean increase in the average RNFL thickness of 4 μm. The temporal RNFL sector (as one may expect) demonstrated the most significant increase (a mean of 14.4 μm). Such an expectation would be due to the location of the ERM, typically situated temporal to the optic nerve head. The central macular thickness values increased at an average of just over 33 μm after the onset of ERM as compared to before. There was a slight but significant decrease in mean deviation of just under 1 dB in the visual fields.
1. Kim JM, Kim KN, Kim WJ, Kim CS. Influence of epiretinal membranes on the retinal nerve fiber layer thickness measured by spectral domain optical coherence tomography in glaucoma. Korean J Ophthalmol. 2019 Oct;33(5):422-429.