Biomedical subjects
Publications and source records attributed to J G Worst.
A description of the author's (J.W.) technique for ICCE using a 'single-handed' freon cryo-extractor is given. Flieringa's ring is used for scleral support. Implantation is performed with an Iris Claw Lens. Stainless steel is used as suturing material.
We present an irrigating microsurgical knife for ocular surgery. Irrigation of balanced salt solution through the knife tip during sectioning removes hemorrhages continuously, allowing uninterrupted sectioning, without cauterization of bleeding vessels. The "zero degree" knife can be bent in any required position.
We present a disposable 21-gauge transparent glass cannula that provides optimal visual control of aspiration-irrigation procedures in cataract surgery. It is especially useful in iris coloboma repair.
We corrected myopia in 62 phakic eyes by fixing a concave intraocular lens to the midperiphery of the iris in the anterior chamber. No inflammation, glaucoma, corneal edema, or intraocular lens induced-cataract has occurred. The lens did not touch the corneal endothelium. The achieved correction was within 10% in 47 of the 62 eyes (76%) and within 20% of the expected correction in all eyes.
In 11 rabbits a comparison was made between the reactions of the cornea to nylon and to stainless steel sutures, macroscopically and by means of scanning electron-microscopy (SEM). Macroscopically, the wounds sutured with steel thread showed much less reaction than the wounds sutured with nylon. Vascularization was never encountered in the wounds sutured with steel thread. SEM examination also showed clear differences, which became noticeable within a short time. Both on the suture and round the opening in the cornea extensive deposits of material are seen within a short time (1 week) in the case of nylon, in the case of stainless steel this reaction is much less marked. A few weeks later deposits also appear on the steel thread, but these have a different composition and contain no material suggestive of an inflammatory reaction.
The corneal stroma is supposed to be a homogeneous structure both from an optical and an anatomical point of view. Intrastromal injection of glutaraldehyde as a fixative causes local swelling and opacification of the corneal tissue. Local injections of small volumes of air superficially and more deeply into the corneal stroma produce similar swellings and formation of opaque areas. SEM investigation of these areas shows the existence of stromal canals, partly pre-existing, partly caused by the internal 'explosions' due to the air-injection. This suggests an anatomically non-homogeneous, although optically homogeneous, cornea.
Lens-capsule material from healthy and cataractous human lenses and from rabbits was collected with specially designed forceps. Subsequently the capsule fragments were fastened, after short pre-fixation, onto a rubber substrate with small stainless steel tacks, to prevent rolling-up of the fragments during the fixation and drying procedure for the SEM. Finally the capsule fragments were studied by SEM. Marked morphological changes, e.g., irregular swelling (like blebs) of the nuclei, formation of deep grooves at the cell borders and complete loss of epithelial cells, were found in the lens capsules obtained from certain cataractous lenses. Differences in capsule thickness were found in pathological capsule material. The imprints (attachment-lines) of the lens-fibres on the epithelial cells were often difficult to visualize.
The SEM-pictures represent a keratoconus in a 59-year-old patient with a Descemet rupture, which had led to a so-called Kammerwassereinbruch, where the failure of the endothelial structure has become manifest in the epithelium. In the Descemet-rupture the onset of stromal pathology is observable, while outside the rupture severe degradation of endothelial cells is seen. This is manifested as cell-membrane perforation, loss of cell contents and oedema formation in general. On the epithelial side the pathology is expressed as cell-membrane degradation and the presence of very irregularly shaped, sometimes swollen and in other cases shrunken, epithelial cells, in particular in the areas of the surface depressions. The topographical correspondence of these pathological phenomena on the endothelial and the epithelial sides is stressed.
A keratoprosthesis (KP) is the last and only surgical resort to regain some visual acuity in eyes with severely damaged corneae. Corneal blindness represents an important percentage of the blind in the economically poor countries. Commercially available KP's, e.g. those made of PMMA, which are difficult to sterilize and vulnerable to surface damage, are too expensive in these countries. To overcome these disadvantages, we developed a new KP, made of a glass core melted into a platinum cylinder with flange. They were implanted unilaterally in eyes of ten Hollander rabbits intralamellarly. They were fixated by two stainless steel traction threads passed around the whole eyeball. We investigated this type of KP in the rabbit cornea, its acceptance by stroma, epi- and endothelium, and its hydro-mechanical dynamics in situ. No signs of infection or extrusion were observed. No epithelial downgrowth, nor adverse tissue reaction could be detected. LM and SEM showed endothelialization of the newly formed stroma around the central column of the KP. We conclude that this type of KP (although optically still to be optimized) has been accepted by the rabbit cornea and a clinical trial on cornea-blind patients is justified.
If a pupil becomes irreversibly miotic during cataract surgery it is helpful to perform an iridotomy to facilitate lens expression. Reconstructing the pupil with one or two iris sutures is advisable in order to prevent coloboma-related problems. We describe a method of iridoplasty that involves using a vanadium steel suture attached to a long, straight needle. This technique can be used in an eye with surgically low pressure as well as in an eye with elevated vitreous pressure.
A biconcave intraocular lens for the correction of myopia is described and preliminary results are presented. An iris claw-type lens is used as a carrier for the biconcave lens. This lens is fixed in front of the natural lens in the mid-periphery of the iris. It maintains a sufficient distance from both the natural lens and the corneal endothelium. The surgical technique is described in detail and the indications and contraindications are discussed. The authors' results so far are encouraging.
The implantation of a concave intraocular lens (IOL) (Worst-Fechner Biconcave Lens) is a new method of correcting myopia. This paper describes how to compute the effective power of an IOL on the basis of corneal curvature and anterior chamber depth, i.e., which lens will neutralize a specific myopia. The authors also discuss the size of the retinal image of an eye corrected by an intraocular lens as compared to an eye corrected by a spectacle glass.
In this study we have demonstrated the formation of an acellular and a cellular membrane on the surface of an explanted intra-ocular lens by scanning electron microscopy. The acellular membrane is considered to be the result of a physiological process, whereas the cellular membrane is looked upon as a pathological endothelial membrane formed as the result of intermittent touch between the implant and the endothelium.
Prolene, perlon, supramid and titanium, either used as sutures, 'Strampelli' sutures or artificial lens loops, were compared after remaining in the human eye for at least one year. For comparison, non-implanted samples of each of the materials were used as blanks. Prolene and Perlon in particular showed severe biodegradation after a given period; Supramid showed much less degradation of its surface. Titanium showed a rather rough outer surface (even in the non-implanted samples), particularly as bends in the lens loop, which facilitated the adherence of cells, fibres and microorganisms.
Intraocular implantation of an iris-bridge or lobster-claw lens was performed on a rabbit eye. The incisions were closed with stainless steel-vanadium sutures. Two months after implantation loosening at one side of the connection between lens and iris was noted, which resulted in long-term intermittent touch of the corneal endothelium. The reaction of the endothelium to the corneal sutures and the contact area of artificial lens and corneal endothelium were studied by SEM.
By means of a new fixation technique keratoprostheses were fixed in the cornea of 'Hollander' rabbits. The fixation is based on the use of corneo-sclerally orientated stainless steel-vanadium traction threads in corneal stroma and scleral tissue. Keratoprostheses placed according to this fixation technique have a follow-up of a maximum of two years. The liquid sealing capacity, the cell behaviour on the surface of the prosthesis and the anchoring of the stainless steel vanadium wire have been investigated in detail with the scanning electronmicroscope (SEM).
Extracapsular surgery was performed on a rabbit eye for implantation of a lobster-claw or iris-bridge type intraocular lens (IOL). The incision was closed with stainless steel-vanadium sutures of 50 micron diameter. Two months after implantation, one pincer of the lens became detached from the iris, causing an intermittent IOL-endothelial touch of four months duration. It resulted in endothelial disruption with localized breaks in Descemet's membrane. Six months after implantation, the IOL and the entire anterior segment were removed and processed for scanning electron microscopy. The lobster-claw lens had been covered partly with a membrane, composed of different types of cells with many microvilli, particularly in the vicinity of the loophole of the intact iris bridge. The sutures were almost completely covered with somewhat irregular endothelial cells and an intact Descemet's membrane. At isolated spots where the covering was incomplete, elongated cells with many microvilli bordered the open areas. At the site of breaks, Descemet's membrane was denuded and in the process of being repopulated with cells. At places of minor disruption, elongated and triangular-shaped endothelial cells, often having many microvilli and interconnections with philopodia-like extensions, were about to cover the "wounded" area.
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