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Biomedical subjects

G I Duncker

Publications and source records attributed to G I Duncker.

45 records · Page 3Linked to original sources
PubMedDate not supplied

Delayed suprachoroidal hemorrhage after penetrating keratoplasty.

We report on an aphakic 30 year-old patient who underwent penetrating keratoplasty on his only functioning eye. On the first day after the operation he developed a total choroidal detachment due to suprachoroidal bleeding. The patient had no sense of orientation. Vision decreased to faulty light perception. One week postoperatively a posterior sclerotomy was performed in order to drain the suprachoroidal blood. Via a paracentesis the globe was pressurized with hyaluronic acid. The following day the suprachoroidal blood had almost disappeared. The retina had become reattached. During a follow-up period of 2 years the visual acuity remained 20/30.

Adult↗
PubMedDate not supplied

Intraocular microendoscopy: experiments in pig eyes.

A new microendoscope is introduced for intraocular use. The probe diameter measures 0.96 mm. The resolving power is 360,000 pixels. Initial experiments on porcine eyes show the image quality to be excellent. This new endoscope may be helpful in lacrimal duct surgery, in cases of hazy corneas with intraocular pathology, for removal of intraocular foreign bodies, and in the diagnosis of tumors of the ciliary body or orbit.

Animals↗
PubMedDate not supplied

Refractive changes after phototherapeutic keratectomy.

PURPOSE: To evaluate refractive error changes after phototherapeutic keratectomy (PTK). SETTING: University Eye Hospital, Kiel, and University Eye Hospital, Hulle, Germany. METHODS: The MEL 60 excimer laser (Aesculap Meditec) was used in all cases. To even out the peaks and valleys of irregular surfaces, modulating agents were applied. The study included 45 patients with various preoperative corneal diseases: central scars, recurrent erosions, corneal dystrophies, and surface irregularities. Subjective and objective refraction, keratometry, slitlamp photography, and corneal topography were performed preoperatively and postoperatively. The follow-up was up to 24 months. RESULTS: Twenty-six patients had stable postoperative refractions. Thirteen patients developed a hyperopic shift; the highest observed amount was +4.0 diopters. In seven patients, the astigmatic error increased, although no significant change in axis was measured. Three patients had a myopic shift. CONCLUSION: After PTK, all types of refractive change can occur. The greatest risk is that of a hyperopic shift. We saw a correlation between the degree of hyperopia and the ablation depth. Methods for preventing such changes include (1) a large treatment zone, (2) use of a polishing program involving a low viscosity fluid at the end of the laser procedure, (3) a two-step treatment in selected cases to avoid ablations that are too deep.

Adult↗
PubMedDate not supplied

Retinal toxicity of liposome-incorporated and free ofloxacin after intravitreal injection in rabbit eyes.

BACKGROUND: Ofloxacin (OFLX) is a fluoroquinolone-antibiotic with a broad antimicrobial spectrum that may have a potential role in the treatment of bacterial endophthalmitis. However, its elimination half life after intravitreal injection is short. To prolong the intravitreal antibacterial level OFLX was incorporated into liposomes. This study was performed to investigate the retinal toxicity of liposome-incorporated and free OFLX. MATERIALS AND METHODS: OFLX was incorporated into multilamellar large vesicles. 0.1 ml of this suspension (= 180.2 microg OFLX) was injected into the midvitreous of rabbit eyes (n = 6). Free OFLX in doses of 100 microg, 500 microg and 1,000 microg was injected into the midvitreous of a second group of rabbit eyes (n = 18). The other eye served as a control and received empty liposomes or normal saline solution, respectively. Before injection and at the end of follow-up an ERG was obtained. After a follow-up of 1 day, 14 and 28 days the animals were perfused with glutaraldehyde and the eyes were examined by light- and transmission electron microscopy. RESULTS: The ERG as well as the histologic studies did not reveal any pathological changes after injection of liposome-incorporated OFLX compared to the control eyes. Significant reduction of the ERG was observed after 500 microg free OFLX in 2 out of 6 eyes after 1 and 14 days, respectively, and in 2 eyes 1 day after 1,000 microg free OFLX. Three days after injection of 1,000 microg OFLX the retina showed focal destruction in 1 out of 6 eyes. In another eye with the same dose 14 days after injection the photoreceptor outer segments showed disorganisation. CONCLUSION: This study shows that liposome-incorporated OFLX did not have any retinal toxicity in this animal model. Free OFLX appears to have no retinal toxicity in rabbit eyes at a dose of 100 microg after intravitreal injection. Injection of higher doses resulted in ERG changes and marked retinal damage.

Animals↗
PubMedDate not supplied

Histopathological comparison of photorefractive keratectomy and laser in situ keratomileusis in rabbits.

BACKGROUND: After 193 nm excimer laser photorefractive keratectomy (PRK) for myopia, superficial opacities in the ablation zone and regression of refractive results can occur. Clinical studies have emphasized that corneal clarity and early refractive stability can be achieved with laser in situ keratomileusis (LASIK). We present clinical and histological results that compare PRK and LASIK for the treatment of myopia in rabbits. MATERIALS AND METHODS: We treated 12 New Zealand white rabbits with PRK and 12 with LASIK using a 193-nm excimer laser (Aesculap Meditec). In both techniques, the identical excimer software and ablation parameters of -10 D treatment depth were used. Six months after surgery, all eyes were removed and prepared for light, fluoresence and transmission electron microscopy. RESULTS: At the time of enucleation, nine eyes in the PRK group had a moderate to high degree of haze (grade 2 to 3), whereas after LASIK, all corneas showed an almost clear interface in the ablation zone. Correspondingly, all histological investigations after LASIK showed a regular stromal architecture, in contrast to the obvious anteri or stromal disorganization after PRK. CONCLUSION: The preserved integrity of the superficial corneal layers after LASIK ensures quick wound healing with minimal tissue proliferation, resulting in a transparent corneal interface. This technique appears especially suitable for correcting high myopia.

Animals↗
PubMedDate not supplied

Ultrastructural and immunohistochemical findings after linear excimer laser keratectomy.

BACKGROUND: One human pathology specimen has been studied previously following the use of the excimer laser for the correction of astigmatism. We report histopathologic findings following linear corneal excisions with the excimer laser. METHODS: A 193 nm excimer laser was used to create symmetrical, transverse excisions in a human eye to correct astigmatism. Three months later, a full-thickness corneal transplant was performed due to unsatisfactory refractive results. The excised corneal button was examined with light microscopy, transmission electron microscopy and immunohistochemistry. RESULTS: An area 10 to 20-micron wide was observed between the epithelial cells within the keratectomy and the sharply dissected stromal lamellae. This area stained positive for laminin and pro-collagen type III. Some epithelial cells showed processes reaching into this area. Descemet's membrane, immediately underneath the area of the keratectomy, contained atypically striated collagen fibers. CONCLUSIONS: These findings demonstrate wound healing changes similar to those reported following diamond knife keratotomy and photorefractive keratectomy for myopia. The changes in the posterior cornea are similar to those previously reported when an excimer laser beam approached Descemet's membrane.

Aged↗
PubMedDate not supplied

Cut edges and surface characteristics produced by different microkeratomes.

PURPOSE: To determine the cutting characteristics of seven different microkeratomes and to compare the cut edges and surface characteristics of the corneas with respect to different keratome parameters, ie, blade oscillation frequencies and keratome speed. METHODS: Lamellar keratectomies were performed using each microkeratome on eight freshly enucleated porcine corneas. The freshly cut corneal bed was then examined using scanning electron microscopy. A scoring system was used to evaluate the serration of the cut edge and the regularity of the corneal wound bed. RESULTS: Serrated cut edges were produced by the Microtech microkeratome, the Automatic Corneal Shaper, the Draeger rotor keratome, and the Schwind microkeratome. The other tested cutting devices generally yielded a smooth cut edge. Smooth and regular wound surfaces were obtained with the Schwind microkeratome, the Automatic Corneal Shaper, the Microtech microkeratome, and the MKM set. The specimens cut with the Schwind microkeratome showed particularly regular surface characteristics. CONCLUSION: The relationship between keratome propulsion speed, blade oscillation frequency, and blade material appears crucial for the quality of the microkeratome cut. Our results favor a low advancement/oscillation ratio among automated microkeratomes.

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