Search

To determine the ocular manifestations of inverting the human body into a head-down vertical position, we evaluated normal volunteers with applanation tonometry, fundus photography, fluorescein angiography, and ophthalmodynamometry. Compared with data obtained in the sitting position, the intraocular pressure more than doubled on inversion (35.6 ±4v14.1±2.8 mm Hg, n=16), increasing to levels well within the glaucomatous range. Pressures in the central retinal artery underwent similar increases, while the caliber of the retinal arterioles decreased substantially. External ocular findings associated with gravity inversion included orbital congestion, conjunctival hyperemia, petechiae of the eyelids, excessive tearing (epiphora), and subconjunctival hemorrhage. We suggest that patients with retinal vascular abnormalities, macular degeneration, ocular hypertension, glaucoma, and similar disorders refrain from inversion altogether. Whether normal individuals will suffer irreversible damage from inversion is uncertain, but it seems prudent to recommend that prolonged periods of inverted posturing be avoided. (JAMA1985;253:1755-1757)

THE VITREOUS is altered pathologically in numerous ocular and systemic diseases. Hence, most physicians will encounter patients whose vision has been impaired by vitreous opacities or by the formation of membranes within the vitreous cavity. Only recently has the successful treatment of vitreous pathology become commonplace, primarily because of the development of specialized microsurgical techniques. To appreciate the importance of vitreous surgery in reducing the prevalence of blindness, a basic understanding of the disease processes affecting the vitreous is necessary. VITREOUS DISORDERS The human vitreous is normally an optically clear gel consisting of 99% water and containing collagen and hyaluronic acid.1The vitreous collagen is firmly attached to the internal limiting membrane of the retina anteriorly near the pars plana; weaker vitreoretinal attachments occur at the macula and at the optic disc. Vitreous Collapse With increasing age, the vitreous gel often collapses and separates from the posterior retinal surface.

• Two eyes were enucleated for angle-closure associated with familial exudative vitreoretinopathy. Characteristic features included total retinal detachment, peripheral retinal vascular proliferation, and a fibrovascular preretinal membrane. Angle-closure glaucoma developed in one case when sudden massive subretinal hemorrhage, associated with abnormal intraretinal vessels, produced anterior displacement of the lens-iris diaphragm; in the second case, angle-closure was associated with the development of rubeosis iridis. Intraretinal inflammatory cells and exudates were also seen in the enucleated eyes.

In Reply.— We agree with Dr Sadun that increases in intracranial arterial and venous pressure undoubtedly occur with inversion and are reflected by the increase in ophthalmic artery pressure as measured by ophthalmodynamometry. As he points out, one of the most important circulatory effects of the inverted posture is elevation of venous pressure. 1 We are alarmed by the close association of a subdural hematoma with gravity inversion and are unaware of any other such reports. Patients with glaucoma and ocular hypertension show elevation of intraocular pressure with gravity inversion as do normal subjects. 2 We share the concerns of Drs O'Connor and Poirier that inverted posturing achieved using gravity-inversion devices or slant boards or by performing head stands may raise intraocular pressures to harmful levels. Their case documents progressive field loss in a patient whose daily exercise routine substantially increased his intraocular pressure. While a direct cause and effect