Search PubMed⌕ Search

Biomedical subjects

Einar Stefánsson

Publications and source records attributed to Einar Stefánsson.

At least 19 recordsLinked to original sources
PubMed2006

Risk factors for five-year incident age-related macular degeneration: the Reykjavik Eye Study.

PURPOSE: To establish risk factors for five-year incidence of age-related macular degeneration (AMD). DESIGN: Population-based, prospective cohort study, and risk analysis. METHODS: A random sample from the Reykjavik Population Census for individuals 50 years and older was selected. We took fundus stereo color photographs and used standard grading system to study the five-year incidence of drusen, pigmentary abnormalities, and AMD and to examine possible risk factors. A questionnaire including information on disease, medication, diet, and lifestyle from the Reykjavik Eye Study database provided additional information. RESULTS: Current alcohol consumption decreased the risk for drusen. Being married rather than divorced or widowed decreased the risk for soft drusen; being single decreased the risk of hypopigmentation as compared with being divorced or married. Both consuming dietary fiber-rich vegetables and meat and meat products once a week or less frequently was a risk factor for developing soft drusen and decreased the risk of pigmentary abnormalities. Those who had smoked 20 pack-years or more as compared with nonsmokers had decreased survival rate over the five years (odds ratio (OR) 0.46, 95% confidence interval (CI) 0.27 to 0.80; P = .006). CONCLUSIONS: Risk factors for drusen appear to differ from risk factors for pigmentary abnormalities. The effect of smoking on developing AMD is partly masked by selective mortality.

Aged↗
PubMed2006

Ocular powder: dry topical formulations of timolol are well tolerated in rabbits.

PURPOSE: Although eye drops are the most common form of ocular drugs, they have several limitations. Drug absorption into the eye is, in general, less than 5%, addition of preservatives is often necessary, and many drugs cannot be formulated as eye drops. Formulating ocular drugs as powder may solve these problems. The aim of this study was to investigate ocular irritation in rabbits following powder administration. METHODS: Timolol maleate (TM) powder was administered to pigmented lop rabbits. Both pure TM powder and freeze-dried with PVP-polymer (2.4% of mass) were tested in 1.0- and 0.1-mg doses. Additionally, 4 rabbits received 0.1 mg of the pure powder 3 times a day for 8 d. Redness of the bulbar conjunctiva and the amount of discharge was rated from photographs (0-3 points, randomized and masked evaluation). The 8-d experiment additionally included examination with a slit lamp and examination of hematoxylin-eosin stained sections of eyes with light microscopy. RESULTS: No serious or irreversible signs of irritation were noted. Doses of 1.0 mg were more irritating than 0.1-mg doses. There was no detectable difference in irritation between pure or freeze-dried powder. Slit-lamp examination, surface photographs and histology showed a negligible difference between drug and control eyes following the 8-d experiment. CONCLUSIONS: The results suggest that 0.1 mg of timolol powder does not irritate the eye and that testing topical timolol powder in humans is feasible.

Animals↗
PubMed2006

Optic nerve pH and PO2: the effects of carbonic anhydrase inhibition, and metabolic and respiratory acidosis.

PURPOSE: Earlier studies have demonstrated that carbonic anhydrase inhibitors (CAIs) increase optic nerve oxygen tension (ONPO(2)) in pigs. We hypothesized that the mechanism of this effect was either a CO(2) increase or a pH decrease in tissue and blood. To test this hypothesis we investigated and compared how optic nerve pH (ONpH) and ONPO(2) are affected by: (1) carbonic anhydrase inhibition; (2) respiratory acidosis, and (3) metabolic acidosis. We measured ONpH with a glass pH electrode and ONPO(2) with a polarographic oxygen electrode. One of the electrodes was placed in the vitreous cavity 0.5 mm over the optic nerve in the eyes of domestic pigs. METHODS: We measured ONpH during carbonic anhydrase inhibition and ONpH or ONPO(2) during NH(4)Cl-induced metabolic acidosis and during CO(2) breathing (respiratory acidosis). RESULTS: Baseline ONpH was 0.12 +/- 0.06 lower than arterial pH (mean +/- SD, n = 10, p < 0.001). Optic nerve pH decreased with arterial pH during carbonic anhydrase inhibition, metabolic and respiratory acidosis. Optic nerve oxygen tension was not affected by metabolic acidosis but increased during CO(2) breathing, as it has been shown to do during carbonic anhydrase inhibition. CONCLUSIONS: There is a close correlation between arterial blood pH and intraocular pH. Isolated ONpH changes do not affect ONPO(2), thus the ONPO(2) increase seen with carbonic anhydrase inhibition is probably not only due to pH changes in the blood and optic nerve. Accumulation of CO(2), either alone or in combination with a pH change, is likely to cause the ONPO(2) increase, but a direct vascular effect should also be considered.

Acidosis, Respiratory↗
PubMed2006

Automatic retinal oximetry.

PURPOSE: To measure hemoglobin oxygen saturation (SO(2)) in retinal vessels and to test the reproducibility and sensitivity of an automatic spectrophotometric oximeter. METHODS: Specialized software automatically identifies the retinal blood vessels on fundus images, which are obtained with four different wavelengths of light. The software calculates optical density ratios (ODRs) for each vessel. The reproducibility was evaluated by analyzing five repeated measurements of the same vessels. A linear relationship between SO(2) and ODR was assumed and a linear model derived. After calibration, reproducibility and sensitivity were calculated in terms of SO(2). Systemic hyperoxia (n = 16) was induced in healthy volunteers by changing the O(2) concentration in inhaled air from 21% to 100%. RESULTS: The automatic software enhanced reproducibility, and the mean SD for repeated measurements was 3.7% for arterioles and 5.3% venules, in terms of percentage of SO(2) (five repeats, 10 individuals). The model derived for calibration was SO(2) = 125 - 142 . ODR. The arterial SO(2) measured 96% +/- 9% (mean +/- SD) during normoxia and 101% +/- 8% during hyperoxia (n = 16). The difference between normoxia and hyperoxia was significant (P = 0.0027, paired t-test). Corresponding numbers for venules were 55% +/- 14% and 78% +/- 15% (P < 0.0001). SO(2) is displayed as a pseudocolor map drawn on fundus images. CONCLUSIONS: The retinal oximeter is reliable, easy to use, and sensitive to changes in SO(2) when concentration of O(2) in inhaled air is changed.

Humans↗
PubMed2006

Changes in muscle compartment pressure after cardiopulmonary bypass.

PURPOSE: Hemodilution and inflammation lead to edema and increased muscle compartment pressure after cardiac surgery. The aim of this study was to find whether muscle compartment pressure was affected by the addition of albumin and mannitol to the pump prime, heparin coating or leukocyte depletion. Additionally, we studied the relationship between intraocular pressure and lower leg muscle compartment pressure. Edema during and following cardiac surgery is due to hemodynamic, osmotic and inflammatory changes, according to Starling's Law. We attempted to influence the osmotic balance and reduce the inflammatory response in order to reduce the edema. METHODS: Thirty-six patients who underwent cardiac surgery were randomly allocated into four groups. Group A received albumin and mannitol into the pump prime. Group B had an, heparin-coated perfusion system, Group C had a leukocyte-depletion arterial line filter and Group D was the control group, where intraocular pressure was also measured. RESULTS: Lower leg muscle compartment pressure increased significantly during and after cardiac surgery in all groups, but this increase was significantly less in Group A than in the control group 24 h after surgery. No correlation was found between muscular compartment pressure and intraocular pressure. The intraocular pressure profile is different from the muscular compartment pressure and recovers much faster. CONCLUSION: Lower leg muscle compartment pressure and intraocular pressure behave differently during and after cardiac surgery. Albumin and mannitol added to the pump prime decreases muscle compartment pressure after cardiac surgery.

Aged↗
PubMed2006

[Age related macular degeneration].

Age-related macular degeneration (AMD) is the main reason for blindness today in the western hemisphere. According to Björn Olafsson, who was the first ophthalmologist in Iceland a century ago, this disease was not found in Iceland. In the blindness-registry of 1950 6% blindness was due to this disease. Today, AMD is responsible for 54% of legal blindness in Iceland. The incidence of the disease increases with age. Heredity and environmental factors are thought to influence its etiology. Indirect methods, including twin studies and increased frequency of this disease in some families, have demonstrated that hereditary factors may be important. This has been confirmed recently by demonstrating that genes on chromosome 1 and chromosome10 play a role. This disease is classified as early stage, with drusen and pigmentary changes and insignificant visual loss. Treatment options for this stage are limited. The use of vitamin E and C and Zinc has, however, been shown to delay its progress. The second and end stage involves visual loss, either as a dry form with pigment epithelial atrophy or wet form, with new vessel formation. Treatment options for the dry form are limited. The second form is more common in Iceland than in other countries. Treatment options for the wet form have increased. Localised laser and drug treatment to neovascular membranes, either alone or as a combination treatment with drugs that have anti-proliferate effect on new vessels (anti-VEGF) are increasingly used. New treatment methods are also used in assisting those that are already visually handicapped. The use of computers is increasing as are the patients' computer skills. As the number of the elderly increases, AMD will be an increasing health problem in Iceland as in other Western countries. It is therefore important to improve the treatment options and the service and counselling of patients.

Aged↗
PubMed2006

[Macular oedema and intravitreal triamcinolone injections].

PURPOSE: To evaluate the efficacy of intravitreal triamcinolone injections for macular oedema in Iceland 2004-2006. METHODS: We reviewed hospital records of 28 patients who underwent intravitreal injection with triamcinolone acetonide 2004-2006. Most patients were treated with 8 mg of triamcinolone acetonide. Patients were categorized according to the cause of macular oedema (diabetes (n=10), phacoemulsification (n=7), branch retinal vein occlusion (BRVO) (n=7) and uveitis (n=4)). Best corrected visual acuity was determined before treatment and 1, 3 and 6 months postoperatively. Intraocular pressure and foveal thickness were measured before and after treatment. RESULTS: Visual acuity improved in 4 patients with diabetic macular oedema while 5 had unchanged vision. The effect lasted 6 months in 8 out of 9 cases. Seven were treated for macular oedema after phacoemulsification. Two had improved visual acuity after the injection and 5 had unchanged eye sight. The effect lasted for 6 months in every case except for one who lost vision. Out of 7 who were treated for macular oedema after BRVO, 3 had improved visual acuity and 4 remained unchanged for 6 months. Four patients with uveitis got triamcinolone injections and a month after treatment 2 had better vision and 2 had unchanged visual acuity. The effect lasted for 6 months in all cases but one. In the diabetes and BRVO groups OCT showed a significant reduction of foveal thickness. In 4 cases intraocular pressure increased, all of them were successfully treated with topical treatment. CONCLUSION: Intravitreal triamcinolone improves visual acuity in about 40% of patients with macular oedema, about 10% lose vision and about 50% remain unchanged. OCT reveal improved anatomic results with significant reduction of foveal thickness and macular oedema. No serious complications were noted.

Adult↗
PubMed2005

Comparison of topical 0.7% dexamethasone-cyclodextrin with 0.1% dexamethasone sodium phosphate for postcataract inflammation.

BACKGROUND: To compare 0.7% dexamethasone-cyclodextrin aqueous eye drop solution applied once daily with 0.1% dexamethasone sodium phosphate eye drops applied three times a day for the control of postoperative inflammation after cataract surgery. METHODS: Twenty cataract patients who underwent phacoemulsification and intraocular lens implantation were randomly divided into two postoperative treatment groups. Postoperative medication in group I included 0.1% dexamethasone sodium phosphate eye drops three times daily and in group II 0.7% dexamethasone-cyclodextrin eye drop solution once daily. Testing of visual acuity, biomicroscopic examination, applanation tonometry and laser flare cell meter (LFCM) examination were carried out before operation and days 1, 3, 7 and 21 after surgery. RESULTS: Preoperative and postoperative visual acuity, aqueous flare and cells in biomicroscopic examination, and the mean intraocular pressure did not show any statistically significant differences between the treatment groups. LFCM examination showed that the mean postoperative photon count values (P=0.032) and the median cell count values on the 1st (P=0.014), 3rd (P=0.031), 7th (P=0.034), and 21st (P=0.0097) postoperative days in group I were more elevated than in group II. CONCLUSIONS: 0.7% dexamethasone-cyclodextrin eye drops applied once daily is a more effective postoperative anti-inflammatory medication than 0.1% dexamethasone sodium phosphate applied three times a day. In both groups, 3 weeks after the operation the mean visual acuity was normal and intraocular pressure significantly lower than before operation. The use of 0.7% dexamethasone-cyclodextrin eye drops may be useful especially in elderly people who cannot apply themselves the eye drops onto the eye.

Administration, Topical↗
PubMed2005

Cyclodextrin formulation of dorzolamide and its distribution in the eye after topical administration.

Due to limited aqueous solubility of dorzolamide at physiologic pH, the pH of Trusopt eye drops (cont. 2% dorzolamide) has to be kept at about 5.65, and to increase the topical bioavailability of the drug from Trusopt the contact time of the drug with the eye surface is increased by increasing the viscosity of the eye drops to 100 cps. This low pH and high viscosity can lead to local irritation. In this study, dorzolamide hydrochloride was formulated as 2% and 4% low viscosity solutions (viscosity 3 to 5 cps) containing randomly methylated beta-cyclodextrin at pH 7.45. These formulations were evaluated in rabbits. The animals were sacrificed at various time points after topical administration of the drug and the dorzolamide concentration determined in the different parts of the eye. Trusopt was used as a reference standard. The topical availability of dorzolamide from the cyclodextrin-containing eye drops appeared to be comparable to that from Trusopt and the drug reached retina and optic nerve to give measurable concentrations for at least 8 h after administration of the eye drops.

Administration, Topical↗
PubMed2005

Nordic research in ophthalmology.

Nordic ophthalmologists and vision scientists are active in many fields of eye research. This is most evident at the biannual Nordic Congress of Ophthalmology, most recently held in Malmö in June 2004. The authors here review some of the research in vision and ophthalmology presented at this meeting or published recently by Nordic scientists. This paper does not represent a comprehensive review of all Nordic research in the field, but attempts to give an overview of some of the activities underway in eye research in this part of the world.

Animals↗