Ocular hypotony is a relative concept which, at any rate, designates intraocular pressure below normal for the eye in question. The tolerance of the eye for increased intraocular pressure is limited; and sooner or later damage occurs. It appears, however, that subnormal tension can continue for long periods without causing manifest changes in the eye. Nonetheless, in time, even under hypotony diseased changes develop (Heath 1948). As regards the effect of persistent hypotony on glaucomatous eyes, two events are of essential interest: the eye's reaction to bypotony, and the development of the glaucomatous changes after the drastic lowering of pressure. The effectuating surgical intervention is relevant to this development.The present material is intended to illustrate these events, with special reference to the occurrence of lens opacities and papillar changes.
MATERIALIn this study an arbitrary level of 10 mm Hg, measured by applanation tonometry, has been set as the upper limit of ocular hypotony. A number of glaucomatous eyes, with persistent hypotony after fistulization, have been continuously followed up over a period of time varying from 0.5 to 14.8 years, with special attention paid to the condition and function of the eye. Table 1 shows the composition of the material.With regard to the main part of the material, available data were collected from current journals and notes made on patient's visits.
Whereas vascular lesions in the retina and opacities in the lens in diabetes mellitus have been the subject of intensive study, comparatively little notice has been taken of variations in intraocular pressure. Ever since Heine (1903) and Krause (1904) recorded a striking hypotony of the eyeballs during diabetescoma, only scanty information on changes observed in the intraocular pressure during this disease are to be found in the literature. Grafe (1924) and Poos (1930) drew attention to the extreme variations in the blood-sugar level, considering that these reacted on the intraocular pressure when, for instance, conditions for a glaucoma were present. Martin (1951), among others, was nevertheless unable to verify these influence from the blood-sugar level. and Larsen (1960) have all stressed how a changing intraocular tension could, as a mechanical factor, initiate or favour the development of diabetic retinopathy.Glaucoma would appear to occur far too frequently among diabetic patients. Such conclusions are, of course, highly dependent on our criteria for diagnosing glaucoma. But Armstrong, Daily, Dobson and Girard (1960), on the basis of a relatively permanent intraocular pressure of 23.4 mm. Hg or higher (Schiotz tension), have recently found an incidence of glaucoma in diabetes of at least 5.9 O/O. A review of earlier literature gave approximately the same incidence.In the present work a study of the diabetic eye with special reference to intraocular tension has been carried out in a limited clientele. The investigation has been divided into the following parts: applanation tonometry, Schiotz tonometry, tonography and gonioscopy.
MATERIAL AND METHODSThe material consists of 172 persons between 12-50 years of age. Almost all belong to the regularly checked diabetic clientele at the medical clinic, who have been called in without differentiation. A few have been referred to the *) Received Dec. 10th 1960.
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