Andreas Frohn

Implantation of a toric poly(methyl methacrylate) intraocular lens to correct high astigmatism

A 57-year-old man experienced a decrease in visual function because of cataract formation. Corneal astigmatism was 13.4 diopters (D) because he had had a penetrating keratoplasty 27 years before. Cataract surgery was planned, and biometric data for toric intraocular lens (IOL) implantation were collected for the manufacture of a custom IOL. After phacoemulsification, a toric poly(methyl methacrylate) (PMMA) IOL of +19.0 D spherical and +12.0 D cylindrical power was implanted via a sclerocorneal tunnel incision. Three months postoperatively, corneal astigmatism was 14.3 D and best corrected visual acuity (BCVA), 20/25. Postoperative refraction (+1.5 -3.0 x 90) and BCVA remained stable for 7 months. No significant IOL rotation was observed. Implantation of a toric PMMA IOL corrected high corneal astigmatism. Toric IOL technology with high cylindrical power allows enhancement of IOL surgery.

Ultrasonic transmission in viscoelastic substances.

PURPOSE To study the propagation of ultrasonic shock waves in viscoelastic agents and the resulting corneal load. SETTING University Siegen, Institute for Mechanics and Control Engineering, Siegen, Germany. METHODS The anterior chamber of a manufactured artificial eye was constructed according to anatomic dimensions. Three openings were drilled--for the phaco tip, for the exchange of a viscoelastic agent or water, and for the shock-wave sensor. The sensor was fixed to the area corresponding to the corneal apex. The sensor signal was analyzed using a direct oscilloscope that measured the amplitude reaching the corneal apex. Shock-wave propagation in several viscoelastic agents was compared with that in balanced salt solution. RESULTS In hydroxypropyl methylcellulose, the shock wave was amplified or influenced slightly. In hyaluronic-acid preparations, acoustic dampening occurred. CONCLUSION Removal of hyaluronic-acid derivatives prior to phacoemulsification is not necessary.

Corneal impact of ultrasound and bevel position in phacoemulsification

Purpose: To investigate the amplitude of ultrasound waves that reach the cornea with the phacoemulsification tip at different angles. Setting: Institute for Applied Mechanics and Control Engineering, University of Siegen, Siegen, Germany. Methods: A model eye was constructed with an ultrasound tip (angle 45 degrees) in the typical position during the procedure and a sensor mounted in the apex of the artificial cornea. The sensor measured the incoming ultrasound waves. Thirty bursts of ultrasound energy were set at 100% power with the bevel of the tip facing up toward the cornea, and 30 bursts were set with the bevel facing down toward the lens. Results: There was no statistically significant difference in the measurements with the tips bevel up and bevel down. Conclusion: There was no significant difference in the corneal load from ultrasound waves with the phacoemulsification tip in a bevel‐up or bevel‐down position.

Beam-deflection method of diagnosing impaired vision

&NA; We describe a simple method to assign a diagnosis of cataract to patients with obscurely impaired vision as well as to those with mild lens opacities. When the narrowest slit is used in a slitlamp examination, a small beam of light appears on the macula. Routine fundoscopy with the 78.0 diopter lens or a 3‐mirror glass is appropriate. If a cataract is present, the beam of light is scattered into several straight lines, distorted lines, or both. This has proved a useful diagnostic tool when the lens appears clear but the patients vision is impaired, and extensive examinations such as computer tomography or nuclear magnetic resonance tomography for impaired vision may be avoided. The beam‐deflection method uses devices that are generally available and can detect cataract in the early stages of development.

Ultraschallausbreitung in Viskoelastika

Um Informationen uber die Ultraschallausbreitung innerhalb eines Viskoelastikums wahrend der Phakoemulsifikation zu gewinnen, wurde ein Kunstauge aus Plexiglas gefrast. Durch Offnungen konnten Viskoelastika oder Wasser in die kunstliche Vorderkammer eingebracht werden. Der Tip eines Phakohandstuckes wurde eingesetzt und ein Druckwellensensor an der korrespondierenden Stelle des Hornhautapex angebracht. Das Signal des Druckwellensensors wurde mittels eines Speicheroszillografen ausgewertet. Schallfortleitung in verschiedenen Viskoelastika wurden durchgefuhrt.

Diode array as fixation light to reduce unwanted globe movements.

In ocular surgery complications can occur from eye movements during topical anesthesia or insufficient retrobulbar anesthesia. To minimize eye movements during surgery a fixation light was designed consisting of a diode array embedded in an eye patch, and a keyboard, which will be positioned on the patient’s thorax. The patient focuses with the unoperated eye at a flashing diode which is part of the diode array. The operated eye is guided by conjugated eye movements. With the keyboard, the surgeon can change the diode signal all over the array. As a result, the eye is kept still or moved in the appropriate direction to facilitate the surgical process. The flat and lightweight design of the device enables its use under sterile surgical covers or in an upright position of the patient during laser applications.

Strahldeflektionsmethode bei der Diagnostik unklarer Sehstörungen

Wenn bei der Spaltlampe der schmalste einstellbare Strahl verwendet wird, zeigt sich bei einer klaren Linse wahrend einer Fundoskopie, die mit einer 78-dpt-Lupe oder mit einem Kontaktglas ausgefuhrt wird, im Bereich der Makula ein entsprechender feiner Strich. Wenn eine Linsentrubung vorliegt, wird dieser Strich als ein Bundel mehrerer Linien abgebildet. Dieses Phanomen zeigt sich nur bei leicht defokussierter Einstellung. Da aufgrund physiologischer Linsenfehler in der Peripherie auch bei klarer Linse Strahldeflektionen auftreten, darf nur der Bereich der Makula fur die Diagnostik herangezogen werden. Wenn aufgrund einer scheinbar klaren Linse zunachst nicht die Diagnose einer Katarakt gestellt wird, kann mit dieser Methode die Sehstorung diagnostisch zugeordnet werden, ohne das die ublichen weiteren Abklarungen wie Gesichtsfeld, CT oder NMR notwendig werden.

Vogelspinnenhaare als Hornhautfremdkörper

A 22 year-old-man and owner of several tarantulas visited his ophthalmologist because of red itchy eyes. Additionally to kerato-conjunctivitis epidemica, uncommon hairs were found especially in his left cornea. Corrected visual acuity was 0.8. According to literature these spider hairs can induce granulomas in the meaning of ophthalmia nodosa, and even migrate inside the eye. Therefore we removed as many hairs as possible, but we left two, not to cause iatrogen perforation. The penetration depth was measured by laser tomography. Local steroids successfully prevented further granuloma formation. Regular ophthalmological controls are important to early detect possible changes, and if necessary to remove these hairs even from deeper corneal layers, in case by keratectomy. Language: de