Biomedical subjects
Publications and source records attributed to J Stepanik.
Using the probe of the Stepanik Arteriotonograph, the T-forces induced in corneal tissue by indentation and their correlation with various intraocular pressure levels were recorded for the first time. The study was performed on enucleated human eyes. The results indicate that when performing tonometry a corneal indentation of more than 0.6 mm should be avoided.
Using programs 33 and 34 of the Octopus 2000 automated perimeter the field within 30 degrees was examined in 20 normal eyes: The blind spot was rarely missed (2 X), quite often interpreted as a relative scotoma (21 X), less frequently as a small absolute scotoma (7 X) or as an absolute plus relative scotoma (10 X). These findings are also valid for all scotomas of equal or of smaller size located elsewhere within the examined field.
In 10 eyes suffering from glaucoma simplex, trabeculoplasty (TBP) was performed in the lower half of the corneoscleral trabeculum. Using an applanation tonometer, the diurnal pressure was recorded for 8 days and tonography performed daily at 10 a.m. TBP was performed at 9:30 a.m. on the second day. The results of this study revealed a marked elevation of intraocular pressure immediately after the TBP, accompanied by a highly significant increase in the resistance to aqueous outflow (R) and an equally highly significant fall in the minute volume of aqueous flow (F). During the following 6 days the intraocular pressure remained lower, the drop in R was significant for two days but not at the end, and the fluctuations of F were negligible throughout.
The scale-reading of the Goldmann tonometer (1 g mass = 9.81 mN force) corresponds to an intraocular pressure of 10 mm Hg at a corneal applanation diameter of d = 3.06 mm (applanating body 1, x values) and to an intraocular pressure of 1 kPa at a corneal applanation diameter of d = 3.53 mm (applanating body 2, y values). A regression line y, calculated from 100 pairs of measurements with these two applanating bodies, with y = 0.097 + 0.1274x and a standard deviation of the y values of Syx = +/- 0.24, was within the 95% limits of tolerance at all points. Hence, the two applanating bodies are equally acceptable.
The tensile force T evoked by indentation of the cornea was registered for the first time using the pressure-sensitive probe of the Stepanik Arteriotonograph : T increases with the depth of the corneal indentation and, when the indentation is constant, it increases asymptomatically to a higher level for about 2 minutes.
This paper presents a case of glaucoma accompanying unilateral naevus flammeus of the face, in which, for the first time, an increase in the measured extraocular venous pressure was detected and verified as the main factor responsible for the pathological increase in intraocular pressure.
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Comparisons between tonography results confirm an almost identical action of timolol and diamox: With both, the intraocular pressure and the minute volume of aqueous flow are significantly reduced, while the resistance to the aqueous outflow remains unchanged. In a consecutive tonometric study it was proved that timolol, when fully developed, inhibits the pressure-lowering effect of diamox (500 mg i.v.) when applied two hours before the latter. Thus the action of timolol is not additive but rather substitutive to the action of diamox. Its maximal pressure-lowering effect corresponds to the half of the aqueous outflow-pressure gradient.
Resolution no. 30.39 of the WHA, passed in May 1977, recommends the adoption of SI units by the medical community throughout the world, including a change from mmHg to kPa. In Austria this requirement has been law since January 1978. This paper describes how simply the transition can be made and how other results, such as those of tonography and differential tonometry, are numerically altered as a result. Finally a simple modification is described which enables the Goldmann tonometer to indicate intraocular pressure, its kPa being equal to g on the scale.
The log delta P/delta V-relation curve, as established in human eyes in vivo by new clinical procedure, is shallower than when measured on enucleated eyes and, at least in a number of eyes, not linear. Thus the bases of Friedewald's nomogram are no longer valid and, consequently, the Schiötz tonometer--and all other tonometers inducing volume displacements of more tha 1 microliter--are useless.
As a result of an acute pathologic event ophthalmic arterial pressure may fall below a level necessary to supply sufficient blood to the eye and optic nerve, and thus to preserve full visual function. A sudden partial or even total loss of visual function. A sudden partial or even total loss of vision may follow. In such cases an early therapeutic elevation of ophthalmic arterial pressure to a value above this critical level may improve or even normalize visual function within a surprisingly short period of time.
After total excision of an excessively large filtering bleb extending to the cornea, the conjunctiva was dissected from the upper half of the eyeball and fixed by sutures into a step of the corneal periphery obtained by a keratectomy of 1 mm large strip of superficial cornea tissue along the upper half of the limbus. In 10 eyes operated on in this way -- and in seven of them over four years -- the newly developed filtrating bleb is flat and shows a well vascularised wall without any signs of degeneration.
The levator muscle of the upper lid is resected transconjunctivally as described by Wolff in 1896, the procedure is however improved by our present knowledge of more rigorous but controlled shortening of that muscle and by the use of the present most delicate suturing procedure. The sutures remain in situ and the stay in hospital is reduced to one or two days.
A new piece of equipment was developed that records the intraocular pressure at the time of biomicroscopically observed collapse of the central retinal artery on the optic disc. A special contact lens with a properly adjusted pressure-sensitive probe allows exact observation of the optic disc and manual compression of the eye, whereas the foot-plate of the probe perceives the intraocular pressure through the applanated peripheral cornea.
A pressure-sensitive probe, specially developed for this purpose, is built into a contact lens in such a manner that when adjusted to the patient's eye the probe registers the intraocular pressure whilst the observer compresses the eyeball and observes the arterial collapse phenomenon on the disc over the contact lens on the slit-lamp microscope. The standard deviation of a clinical measurement is 1.5 mm Hg. Derived from measurements on 65 eyes of patients without signs of vascular disorder, the correlation of the systolic and diastolic ophthalmic artery-pressure (y) to that of the ipsilateral brachial artery (x) is given by Y =0.79x-1.33 (r=0.96) and the correlation of their median pressure by Y=0.93x-17.2 (r=0.94).
The Mackay-Marg-Tonometer registers continuously the intraocular pressure (Pt) as exactly as an electromanometer connected with the eye provided that the corneal rigidity is eliminitated by a smooth indentation of the cornea by the tip of the probe, the determined deviation of the registered values from linearity is considered and the temperature of the probe is not influenced from outside.
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The coats of the eyeball influence the results of tonometry 1. by their response to changes of intraocular volume and pressure as expressed by the deltaP/deltaV-ratio and 2. by the rigidity of the cornea. None of the clinical methods in use is able to measure the true deltaP/deltaV-ratio in vivo. Therefore this factor has to be either eliminated from tonometry or measured by a rather complicated new procedure as described in this paper. The rigidity of the cornea as measured on enucleated eyes, offers a resistance increasing significantly with the thickness of the cornea, the size of the applanation and the altitude of the intraocular pressure. It might be neglected in applanations up to 3 mm in diameter, in larger applanations however it becomes a remarkable source of error.