Researchers found a positive correlation between central corneal thinning and the optic nerve exposure rate (ONSR) and orbital fat exposure rate (OFSR), according to a study published in International Ophthalmology.
The investigation concentrated on determining the influence of glaucoma and the central corneal thickness (CCT) on the biomechanics of the optic nerve head. Neither glaucomatous damage nor CCT could be directly associated with changes in the biomechanics of the optic nerve head. Hence, the usefulness of biomechanical studies of the optic nerve head requires further research.
“This was the first study to examine the relationship between CCT and optic nerve elasticity.” the study says. Through a prospective study of patients in Turkey, the researchers wanted to investigate how glaucoma and changes in CCT, a known risk factor for glaucoma, changes can affect the biomechanics of the optic nerve head. The researchers performed a record review of patients with primary open-angle glaucoma and patients with a CCT of less than 510 µm and greater than 570 µm. Volunteers who applied to the clinic but had no eye disorders were included as a control group.
All participants underwent grayscale sonography and real-time elastography. The optic nerve load rate and the orbital adipose tissue were assessed after 10 to 12 measurement cycles. The patients were divided into 1 of 4 groups based on CCT measurements and glaucoma presence: Group 1 comprised those without glaucoma but with thin corneas (n = 32), Group 2 comprised those with glaucoma and thin corneas (n = 34), group 3 included those without glaucoma with thick corneas (n = 34) and group 4 included those with glaucoma and with thick corneas (n = 10).
Neither a statistically significant difference in the load rate of the optic nerve and in the orbital fat was found among all groups, nor were differences in the load ratio of orbital fat to the optic nerve head (SROFON), the load ratio of orbital fat to the medial part of the optic nerve (SROFMON) and the stretch ratio of orbital fat to lateral part of the optic nerve (SROFLON). Real-time elastography results showed a “positive but not strong” correlation between optic nerve exposure rate, orbital fat exposure rate, and mean CCT in participants with a CCT of 510 μm or less. Regardless of the mean CCT, no statistical difference was found between participants with and without glaucoma with regard to the load on the optic nerve and SROFON.
Study limitations include differences in the mean age of each group, as well as the use of stem elastography techniques that are not eye specific and can produce variable results. In addition, the researchers found that the CCT may not be sensitive enough to measure the mechanical properties of optic nerves.
“The usefulness of [optic nerve head] Elastography techniques for understanding glaucoma and its risk factors should be explored [a] larger and more homogeneous patient series, ”according to the study.
Aksoy Lower Austria, Çakir B, Aksoy YE et al. Effects of glaucoma and the thickness of the central cornea on the biomechanics of the optic nerve head. Int Ophthalmol. Published online January 2, 2021. doi: 10.1007 / s10792-020-01686
This article originally appeared on Ophthalmology Advisor