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No nocturnal IOP elevation found in young OAG patients with moderate to severe myopia
In a study designed to evaluate the circadian pattern of intraocular pressure fluctuations in young myopic patients with open-angle glaucoma, Jeong and colleagues found that IOP increases at night in patients with emmetropia or mild myopia.
The Investigative Ophthalmology & Visual Science study also discovered that, in patients with moderate or severe myopia, there was no nocturnal elevation.
Researchers recorded the IOP of 108 18- to 50-year-old OAG patients with moderate to severe myopia and 67 age-matched OAG patients with emmetropia or mild myopia 11 times over a 24-hour period.
Results showed that, of the OAG patients with emmetropia or mild myopia, 20.8% had a diurnal acrophase, 44.8% had a nocturnal acrophase, and 34.4% had no acrophase. Of OAG patients with moderate to severe myopia, 40.7% had a diurnal acrophase, 15.7% had a nocturnal acrophase and 43.6% had no evident acrophase.
Researchers reported that the mean IOP of the group with moderate to severe myopia was significantly higher than the group with emmetropia or mild myopia in a sitting position during the day. The mean IOP of the group with moderate to severe myopia was lower than the group with emmetropia or mild myopia in a recumbent position at night.
"The present study showed no overall nocturnal mean IOP elevation in a large proportion of young OAG patients with moderate to severe myopia when IOP was measured in patients' habitual positions," the authors said. "This is in contrast to the control group, which showed significant nocturnal habitual-position IOP elevation. In addition, individual analysis revealed three distinct acrophase patterns among the myopia subjects that differed from those of the control group. The 24-hour IOP range and nocturnal habitual IOP elevation were negatively correlated with axial length in our young OAG cohorts.
"Further studies are needed to identify ocular factors that can influence the 24-hour IOP pattern, as this may provide clinicians with a better understanding of the mechanisms of glaucoma and aid in determining an optimal individualized IOP-lowering treatment strategy," they concluded.
Perspective
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The literature on nocturnal IOP variation in normals and glaucoma patients is extensive, yet offers no clear understanding of how IOP varies through the 24-hour period or the significance of IOP variation on glaucoma. Jeong and colleagues shed some light on the topic of circadian IOP fluctuation for two important subsets of our patient population: untreated young myopic glaucoma patients and untreated young near emmetropic glaucoma patients. Interestingly, the myopic group was found to have little circadian IOP fluctuation compared with the near emmetropic group. It would have been interesting to see circadian blood pressure measurements given the largely normotensive subject profile in both groups, but these data were not acquired.
For those of us serving a largely Asian population, these data may be particularly helpful because all study subjects were ethnically Korean. After reading this study it is tempting to lower concern about nocturnal IOP spikes in myopic glaucoma patients. However, this is a murky and complex area of study, and further clarification is needed. For now, I agree with the author’s conclusion that these data may assist us in glaucoma treatment of an interesting and challenging patient subset.
Quaranta L, et al. Survey of Ophthalmol. 2013;58:26-41.
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Invest Ophthalmol Vis Sci. 2014;doi: 10.1167/iovs.13-13607.