Idiopathic Bilateral Profound Hypotony in an Unknown Progressive Neurodegenerative Disorder
We would like to thank Drs. De Bernardo and Rosa for their interest and comments on our paper1 and the editor for the opportunity to respond. Rosa and colleagues have made significant contributions to our understanding of intraocular pressure (IOP) in patients with myotonic dystrophy.
We agree that our patient’s symptomatic vision loss, progressive corneal astigmatism, optic nerve head edema, and macular folds support the presence of severe ocular hypotony. These findings were so severe that any effect of corneal biomechanics on IOP estimation would have been insignificant and not clinically relevant.
In addition, we appreciate their insight into the diagnostic challenges that arise with high-frequency ultrasound examination in hypotony. A thorough anterior segment ultrasound examination (Ellex, Eye Cubed, Minneapolis, MN) was performed by an ultrasonographer with 14+ years of experience. No ciliochoroidal detachment (CCD) was found in our patient. We feel that his shallow anterior chamber was likely due to generalized globe collapse and not CCD.
The relationship between hypotony and CCD is complex. Although they often occur together, a cause and effect relationship is not certain. In many cases, concurrent inflammation is a confounding variable.2 Rosa et al have demonstrated the presence of CCD in myotonic dystrophy.3 They hypothesize that this leads to compromised ciliary body perfusion and decreased aqueous production.2 However, Pederson and colleagues created both serum-induced and silicone oil-induced CCD in monkies, a model with minimal inflammatory response. Silicone oil CCD resulted in an insignificant drop in IOP, whereas serum CCD resulted in a drop of 6 mm Hg that normalized in 3 weeks. Serum CDD did not result in decreased aqueous production despite transient hypotony.4
We maintain that hypotony in this young patient with progressive neurodegenerative decline is most likely due to increased nonconventional (uveoscleral) outflow, which may be related to increased aqueous egress across an atrophic ciliary body face5,6 and/or increased intramuscular space in the ciliary muscle.