We appreciate Drs Kaya and Akincioğlu’s interest in our paper, and agree that more needs to be learned about the role of the choroid in glaucoma pathophysiology. While our study provided data on the anatomic relationships between juxtapapillary choroidal thickness and β-zone parapapillary atrophy in eyes with and without glaucomatous optic neuropathy, additional investigations are needed that focus on the dynamic and complex interrelationships between the choroid, intraocular pressure (IOP), sclera, lamina cribosa, and other optic nerve head tissues. Although several research groups are actively investigating optic nerve head biomechanics in glaucoma, the choroid has received relatively little attention within these efforts. In our opinion, the specific role that the choroid serves with regard to optic nerve head vascular support, nutritional support, and biomechanical buffering deserves concentrated study.
In their letter, Drs Kaya and Akincioğlu state that eyes with congenital glaucoma develop abnormal elongation of the globe, resulting in myopic peripapillary atrophy and choroidal thinning. They then suggest that choroidal changes in primary open-angle glaucoma (POAG) may also result from an abnormal IOP/sclera relationship. While the relationship between IOP, sclera, and choroid is somewhat intuitive in congenital glaucoma, the relationship between these parameters in POAG is less clear and likely very complex. It is well known that scleral tissue is more compliant in young vs old eyes, and thus determining how choroidal thinning would occur in the setting of a stiffer, older sclera is uncertain. Additionally, the type of parapapillary atrophy typically demonstrated in myopic eyes (γ-zone parapapillary atrophy) is microstructurally distinct from the β-zone parapapillary atrophy that has been associated with POAG eyes.
Moreover, several studies report that eyes without statistically elevated IOP more commonly exhibit glaucomatous parapapillary atrophy compared to eyes with statistically elevated IOP. Finally, in our study, we did not find a relationship between choroidal volume, IOP, and axial length, though our cross-sectional design severely limits any comments we can make with regard to effect of IOP. Despite these issues, the sclera is known to play an important role in glaucoma and it is possible that it interacts with the choroid in significant ways. Further study is needed to better understand the pathogenesis and implications of choroidal thinning in glaucoma as well as its relationships with IOP and the sclera.