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Measuring of cutting pressure in ophthalmic microsurgery
ABSTRACTS
179
The Mackay Marg Tonometer: Clinical and Experimental Studies J. STEI~ASIK,
v’ienna
Cornea plus sclera was mounted over the window of a transparent pressure-chamber on the slitlamp. Applanations produced by footplate of Mackay Marg-tonometer probe (MMT) from the outside were observed through the cornea from the inside of the chamber. The trough in the ascending part of the tonogram (z)was correlated to the applanation of the cornea by the whole of the foot alate. The tonoerams were mternretable as long as MMT was annlied to or displaced for less than 6.8 mm from thee top of applanated cornea1 a;a. The standarddeviation of xwas kO.27 mmHg. In patients MMT produces higher values than Goldmann’s tonometer, the differences corresponding to pressure-increase produced by cornea1 applanation of an area 4.8 mm in diameter. The probe fixed on the slit-lamp wit,h a plexiglass plate around its footplate allows the probe to be centred precisely against the patient’s cornea so that well-formed tonograms or pulsatory variat’ions of intraocular pressure (V) can then be recorded. The standard deviation of the applitude of the first trough was highly correlated to the amplitude of V. The probe of MMT adjusted to a contact lens permits the increase of intraocular pressure caused by compression of the eyeball to be recorded and also the observation of collapse phenomena on the central ret.inal artery as known by dynamometry (see J. Stepanik, aon Oraefea Arch. Ophthul. 1970-1972).
Measuring of Cutting Pressure in Ophthalmic Microsurgery J. DRAEGEE.
Bremen
Too little emphasis has been given to the importance of mechanical conditions in microsurgical cutting techniques. The lower the pressure which is exerted, the more precisely the wound edges are cut and with this aim. a new motor-driven cutting device has been especially developed for use under the microscope. Not only better optical control is achieved but also cutting pressure is minimized. The cutting pressure in any tissue depends on the ratio distance/time of the cutting instrument which means t,hat there is an almost linear correlation between the speed of cutting edge and the resulting extension of the incision. This has been proved in a series of experiments using this new remote controlled rotor instrument.
Lipid-containing Substances in the Basement Membrane Network Epithelium J. ~~sn~xm.
of the Human Ciliary
&fainz
The basemmt membrane network at the internal surface of the adult human ciliary epithelium contains osmiophilic deposits. The lamellar structure of t.he particles shows a periodicity of 46 and 40 A; on rare occasions of 33 d (mean values). These laminar structures resemble the myelin figures made from phospholipids of the brain, surrounding chylomicrons, or occurring at the surface of lipid droplets. It is therefore suggested t,hat the osmiophilic deposits in the basement membrane network also are lipids or lipoproteins respectirely. The origin of the particles might be lipofuscins of the aged nonpigmented ciliary epithelium, degenerating cell processes of the nonpigmented ciliary epithelium, degenerating fibroblasts of t,he zonular apparatus, or the basement membrane material itself.
Experimental Occlusion of the Vortex Veins S. S. HAYI~EH
and J. A. BAINES,
Edinburgh
In 34 e;ves of rhesus monkeys, the various vortex veins (VV) were cauterized outside the eyeball close to their exit in various combinations, i.e. 1 , 2, 3 or all the veins. Fourteen eves were followed for periods up to 3 months. In rhesus monkeys, the W did not communicate freely with one another but had a well-defined segmental distribution in the entire length of the uveal tract, each vein usually draining a quadrant of the uvea. Because of this segmental distribution, and the segmental distribution of the posterior ciliary arteries and of the choriocapillaris, occlusion of a VV produced marked venous congestion and the sluggish circulation in the affected segment of the uveal tract. Chorio-retinal degenerative lesions were seen on follow-up near the equator in the region of the occluded VV, even if only one VV was otcluded.
179
The Mackay Marg Tonometer: Clinical and Experimental Studies J. STEI~ASIK,
v’ienna
Cornea plus sclera was mounted over the window of a transparent pressure-chamber on the slitlamp. Applanations produced by footplate of Mackay Marg-tonometer probe (MMT) from the outside were observed through the cornea from the inside of the chamber. The trough in the ascending part of the tonogram (z)was correlated to the applanation of the cornea by the whole of the foot alate. The tonoerams were mternretable as long as MMT was annlied to or displaced for less than 6.8 mm from thee top of applanated cornea1 a;a. The standarddeviation of xwas kO.27 mmHg. In patients MMT produces higher values than Goldmann’s tonometer, the differences corresponding to pressure-increase produced by cornea1 applanation of an area 4.8 mm in diameter. The probe fixed on the slit-lamp wit,h a plexiglass plate around its footplate allows the probe to be centred precisely against the patient’s cornea so that well-formed tonograms or pulsatory variat’ions of intraocular pressure (V) can then be recorded. The standard deviation of the applitude of the first trough was highly correlated to the amplitude of V. The probe of MMT adjusted to a contact lens permits the increase of intraocular pressure caused by compression of the eyeball to be recorded and also the observation of collapse phenomena on the central ret.inal artery as known by dynamometry (see J. Stepanik, aon Oraefea Arch. Ophthul. 1970-1972).
Measuring of Cutting Pressure in Ophthalmic Microsurgery J. DRAEGEE.
Bremen
Too little emphasis has been given to the importance of mechanical conditions in microsurgical cutting techniques. The lower the pressure which is exerted, the more precisely the wound edges are cut and with this aim. a new motor-driven cutting device has been especially developed for use under the microscope. Not only better optical control is achieved but also cutting pressure is minimized. The cutting pressure in any tissue depends on the ratio distance/time of the cutting instrument which means t,hat there is an almost linear correlation between the speed of cutting edge and the resulting extension of the incision. This has been proved in a series of experiments using this new remote controlled rotor instrument.
Lipid-containing Substances in the Basement Membrane Network Epithelium J. ~~sn~xm.
of the Human Ciliary
&fainz
The basemmt membrane network at the internal surface of the adult human ciliary epithelium contains osmiophilic deposits. The lamellar structure of t.he particles shows a periodicity of 46 and 40 A; on rare occasions of 33 d (mean values). These laminar structures resemble the myelin figures made from phospholipids of the brain, surrounding chylomicrons, or occurring at the surface of lipid droplets. It is therefore suggested t,hat the osmiophilic deposits in the basement membrane network also are lipids or lipoproteins respectirely. The origin of the particles might be lipofuscins of the aged nonpigmented ciliary epithelium, degenerating cell processes of the nonpigmented ciliary epithelium, degenerating fibroblasts of t,he zonular apparatus, or the basement membrane material itself.
Experimental Occlusion of the Vortex Veins S. S. HAYI~EH
and J. A. BAINES,
Edinburgh
In 34 e;ves of rhesus monkeys, the various vortex veins (VV) were cauterized outside the eyeball close to their exit in various combinations, i.e. 1 , 2, 3 or all the veins. Fourteen eves were followed for periods up to 3 months. In rhesus monkeys, the W did not communicate freely with one another but had a well-defined segmental distribution in the entire length of the uveal tract, each vein usually draining a quadrant of the uvea. Because of this segmental distribution, and the segmental distribution of the posterior ciliary arteries and of the choriocapillaris, occlusion of a VV produced marked venous congestion and the sluggish circulation in the affected segment of the uveal tract. Chorio-retinal degenerative lesions were seen on follow-up near the equator in the region of the occluded VV, even if only one VV was otcluded.