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Biomedical subjects

O O Pedersen

Publications and source records attributed to O O Pedersen.

At least 19 recordsLinked to original sources
PubMed1997

Reoperations after photorefractive keratectomy for moderate and high myopia.

PURPOSE: To contribute data regarding results of reoperation with excimer laser for the treatment of residual myopia, and to improve corneal clarity following previous photorefractive keratectomy for 'moderate' (< -9 D) and 'high' (> -9 D) myopia. METHODS: Surface reablations with excimer laser (5 mm treatment diameter) were performed to correct residual myopia and remove subepithelial scars. Refraction, visual acuity, and corneal clarity were recorded with average follow-up of one and two years after reoperation. RESULTS: In 27 eyes with 'moderate' myopia before the first operation, significant improvement was obtained regarding refraction (changed from -2.3 +/- 1.56 D before retreatment to -0.58 +/- 1.31 D after retreatment (p < 10[-3])), and uncorrected visual acuity (improved to > or = 0.8 in 51.8% of the cases). All cases (6 eyes) with corneal scars improved. Six eyes with 'high' myopia showed no improvement of refraction following reoperation. Effects on corneal clarity were mixed in that group. CONCLUSION: We were able to improve the results of photorefractive keratectomy for 'moderate' myopia with a second excimer laser ablation. The risks involved in retreatments of such eyes are small. In 'high' myopia, reablations with a 5 mm treatment zone did not improve the refractive outcome on a long-term basis.

Adult↗
PubMed1990

Comparison of the protective effects of methylcellulose and sodium hyaluronate on corneal swelling following phacoemulsification of senile cataracts.

The protective effects of two viscoelastic substances (hydroxypropyl methylcellulose and sodium hyaluronate) on the cornea during phacoemulsification of senile cataracts were investigated in a prospective, randomized, clinical study. The viscoelastic substances were placed in the anterior chamber before and during phacoemulsification. The mean increase in central corneal thickness (measured by ultrasonic pachymetry) on the first postoperative day was statistically significantly higher (P less than .05) in the methylcellulose group (35 eyes) than in the sodium hyaluronate group (35 eyes). Five weeks postoperatively the difference in mean central corneal thickness between the two groups was not statistically significant. However, one eye in the methylcellulose group developed bullous keratopathy. The present study indicates that methylcellulose does not protect the corneal endothelium as effectively as sodium hyaluronate during phacoemulsification procedures.

Aged↗
PubMed1990

Phacoemulsification and intraocular lens implantation in patients with cataract. Experiences of a beginning 'phacoemulsification surgeon'.

Phacoemulsification was performed in 125 eyes (123 patients) selected from 145 eyes (143 patients) referred for planned extracapsular cataract extractions and intended posterior chamber intraocular lens implantations. These procedures were the first clinical phacoemulsification operations performed by the author. In the total material, lesion of the posterior capsule or zonules occurred in 7 eyes (4.9%). Vitreous loss occurred in 3 of these eyes (2.1%). In cases with vitreous loss the operative strategy was changed to implantations of anterior chamber lenses. Five of the 7 eyes that experienced intraoperative complications, had preoperative complicating conditions other than cataract. Visual acuity 6 to 12 weeks postoperatively was 6/12 or better in 87% (126/145) of the eyes. Excluding preoperative posterior segment pathology, 98.4% (126/128) achieved this visual acuity. This study demonstrates that it is possible to include phacoemulsification as the main treatment modality in planned ECCE operations without significant increase in complication rates even for a 'beginning phacoemulsification surgeon'.

Adult↗
PubMed1989

Anterior mesenchymal dysgenesis of the eye. Congenital hereditary endothelial dystrophy and congenital glaucoma.

The present report describes a patient with congenital glaucoma and iris hypoplasia who underwent repeated surgery to control the glaucoma. Despite these procedures, the patient's corneas opacified progressively, and bilateral penetrating keratoplasties were performed. Histopathological studies, including transmission and scanning electro microscopy of the corneal buttons, demonstrated specific changes of Descemet's membrane and the endothelium typical of congenital hereditary endothelial dystrophy (CHED). CHED has usually been considered to be a specific clinical entity that is not combined with congenital glaucoma or other significant abnormalities of the anterior segment of the eye. The present case indicates that these conditions may be combined, which is of importance when dealing with infants with congenital glaucoma and corneal opacities.

Anterior Chamber↗
PubMed1988

Chronic bacterial endophthalmitis in pseudophakia.

The present report describes a case of bacterial endophthalmitis which was suppressed with topical and systemic corticosteroids for 3 1/2 months in the belief that the uveitis was a sterile reaction. Subsequent pars plana vitrectomy and microbiological work-up disclosed an infection with coagulase-negative staphylococci. The patient was treated with intraocular and systemic antibiotics, and the inflammation settled rapidly. It is concluded that infectious endophthalmitis should be suspected after intraocular surgery when the intraocular inflammation is unexpectedly exaggerated. A diagnosis of sterile uveitis should be made only after careful evaluation which includes a proper microbiological work-up.

Adrenal Cortex Hormones↗
PubMed1987

Combined corneal transplantation, extracapsular cataract extraction, and artificial lens implantation (triple procedure).

The treatment of eyes with significant opacities of the cornea as well as cataract is a major challenge for the ophthalmic surgeon. Recent data indicate that these problems may be dealt with safely in a single combined operation which includes penetrating corneal transplantation, extracapsular cataract extraction, and implantation of an artificial lens (triple procedure). In the present report the author's initial experience with the triple procedure is presented. In four patients with a minimum of 6 months follow-up, clear media and marked visual improvement were achieved in all cases. The corneal pathology included two cases of Fuchs' dystrophy, and two cases of central scarring following interstitial keratitis. No complications occurred. The visual rehabilitation time was short, and comparable to ordinary phakic grafting. The triple procedure should be considered in selected cases where there are no specific contraindications to corneal grafting, cataract extraction, or lens implantation.

Cataract↗
PubMed1983

Management of complications after cataract surgery by the pars plana approach.

Various ocular complications following cataract surgery were treated using vitrectomy instruments by the pars plana approach. A total of 11 eyes were operated. Eight of these eyes had various anterior segment problems: Secondary cataract (2 eyes), cyclitic pupillary membranes (2 eyes), up-drawn pupils (3 eyes), and occluding pupillary membrane following haemorrhage (1 eye). In 2 of these eyes opacities in the posterior vitreous were present as well. In addition, pars plana vitrectomy was performed in 3 eyes with presumed bacterial endophthalmitis. In one of these eyes, the vitreous was sterile at the time of the vitrectomy. The vitreous of the 2 other eyes contained Staphylococcus epidermidis, and Staphylococcus aureus, respectively. In the eyes with anterior segment problems, clear optical media were obtained in all cases. The visual outcome in these patients was determined by the condition of the retina at the time of surgery. Two of the eyes with endophthalmitis were saved with some preservation of vision. The third of these eyes which suffered from endopthalmitis caused by penicillinase-producing Staphylococcus aureus, was lost. In this case vitrectomy and adequate antibiotic therapy was delayed. The modern vitrectomy instruments designed for pars plana vitrectomies are highly suitable for management of anterior segment problems following cataract surgery. When these problems are combined with pathology of the posterior vitreous, both kinds of problems may be dealt with at the same operation. In cases of presumed bacterial endophthalmitis, early vitrectomy should be considered to remove infective organisms, to obtain a definite diagnosis, and at the same time the eye may be perfused with antibiotics.

Aged↗
PubMed1981

Antibodies against Toxoplasma gondii in the aqueous humour of patients with active retinochoroiditis.

In active cases of ocular toxoplasmosis, antibodies against the parasite are produced locally in the eye. This antibody production may be revealed by examination of the aqueous humour, and comparing the antibody titer with that of serum. We examined the dye test titer as well as the total IgG concentration of the aqueous humour and serum in 10 patients with active retinochoroiditis. Six of the 10 patients had a significantly higher antibody titer in the aqueous humour than in serum, in relation to their contents of total IgG, proving that the retinochoroiditis was caused by infection with Toxoplasma gondii. Negative results do not exclude the possibility that the inflammation is caused by this parasite. False negative results may occur when the total IgG concentration is either very low, or very high. The time at which the test is performed, in relation to the onset of the inflammation, is also of importance. Our results also suggest that the larger the size of the active lesions is, the higher is the chance of obtaining a definite diagnosis. It is concluded that aqueous humour analysis for antibodies against Toxoplasma gondii should be considered in cases of active retinochoroiditis of unclear or suspected toxoplasmic etiology.

Adult↗
PubMed1980

Increased vascular permeability in the rabbit iris induced by prostaglandin E1. An electron microscopic study using lanthanum as a tracer in vivo.

Prostaglandin E1 (PGE1) (25 micrograms) was applied topically to the eyes of albino rabbits, and lanthanum was used as an electron microscopic tracer to study possible vascular permeability changes in the iris of these eyes. Lanthanum was injected directly into the blood circulation 15 min after application of the PG, and the eyes were enucleated 30 to 60 min later. PGE1 was found to induce increased vascular permeability. Heavy deposits of the tracer were found in the walls of iridial venules, especially between the endothelium and its basement lamina. The highest concentration of lanthanum was found in close relation to the interendothelial clefts. Occasionally, gaps between neighbouring endothelial cells were observed. In control eyes, not treated with PG, no extravasation of the tracer was found. The study indicates that the iridial blood vessels contribute to the production of the plasmoid aqueous humour induced by PGE1 in the rabbit eye.

Animals↗
PubMed1980

Electron microscopy of lanthanum in plasma.

Aqueous solutions of lanthanum nitrate may be used as electron microscopic tracers in vivo to study vascular permeability in the experimental animal. However, with this technique the size of the tracer articles is not known. To gain information about the tracer size, we injected lanthanum nitrate into the blood circulation of living rabbits. The plasma obtained from such animals 30 min later, was studied with the electron microscope. The plasma contained an electron-dense material, readily visible in the electron microscope. A precipitate obtained after centrifugation of the whole blood to separate the cells, also contained the tracer. Lanthanum was found in large amounts in the fibrin clot obtained after treating the plasma with thrombin. The tracer was not detected in the "serum" (i.e. thrombin-treated plasma). The study indicates that ionic lanthanum injected into the blood circulation of living rabbits, is to a great extent bound to fibrinogen, and that the smallest possible size of the tracer is that of the fibrinogen molecule (m.w. 330,000). Larger particles are present as well.

Animals↗
PubMed1978

The ciliary body and the suspension of the lens in rabbits. A scanning electron microscopy study.

The ciliary body in rabbits is dominated by the ciliary processes, which number about 165. Most of them are straight, regularly spaced and uniformly shaped, and they have an even surface when seen at low magnification. They are separated by deep valleys with almost vertical sides. Anteriorly, the ciliary processes end abruptly, and about every second process leads into an iridial process which run radially along the posterior surface of the iris. At higher magnification, the individual cells can be seen to be demarcated by furrows, with a pattern which is specific for the different parts of the surfaces studied. The lens is suspended in innumerable zonular fibers, forming a rather thick mat. They attach in one continuous belt at the anterior end of the ciliary processes, and directly on the lens equator. The anatomy of this part the rabbit eye differs in many respects from that found in primates.

Animals↗