PubMed Health⌕ Search

Biomedical subjects

F Jonasson

Publications and source records attributed to F Jonasson.

At least 19 recordsLinked to original sources
PubMed2005

The time pattern of bilateral exudative age-related macular degeneration.

PURPOSE: To study time patterns in bilateral exudative age-related macular degeneration (AMD) and the pattern of drusen before and after the onset of exudative AMD. MATERIAL AND METHODS: Out of 2220 individuals in the Icelandic genetic study of AMD, 151 had bilateral exudative AMD. We searched for previous records in the Icelandic University Retina Unit. For the 65 patients with a fluorescein angiography record of both eyes, we established the time between the onset of disease in each eye. For the 53 patients with colour fundus photographs of the latter eye taken prior to the occurrence of exudative disease, we graded the drusen before and after the onset of exudative AMD in the second eye. RESULTS: The time interval between the onset of exudative AMD in the first and second eyes was 2.5 years (95% CI: 1.8-3.2; n = 65) and the median was 1.8 years. In 82% of cases the second eye was affected within 4 years. Soft drusen in the macula were found in 95% of eyes that later developed exudative disease (n = 53). Soft and hard drusen decreased in number in the central macula following the development of exudative disease. CONCLUSIONS: Bilateral exudative AMD develops within a few years in both eyes. Drusen are less visible following the onset of exudative AMD in the second eye.

Aged↗
PubMed2005

Epidemiology of the optic nerve grey crescent in the Reykjavik Eye Study.

AIM: To establish the epidemiology of the grey crescent in a white population within the age range most susceptible to glaucoma. METHODS: Bruce Shields was first to use this term to describe a localised, physiological pigmentation of the optic nerve neuroretinal rim tissue that is distinct from peripapillary pigmentation. An experienced glaucomatologist (KFD) evaluated stereofundus photographs of the participants of the Reykjavik Eye Study (RES)-a random sample from the national population census including people 50 years and older. 1012 right eyes could be evaluated for grey crescent. RESULTS: The prevalence of grey crescent in the right eyes was 22.0% (95% CI 10 to 25). It was more commonly found in women (27.0%: 95% CI 23 to 30) than in men (17.0%: 95% CI 14 to 21), and was most often located temporally (36.9%), 360 degrees (15.9%), or nasally (15.4%). The spherical equivalent was +1.30 dioptres (D) for those with and +0.80 D for those without grey crescent (p = 0.002), respectively. Vertical optic disc diameters were 0.203 v 0.195 units (p<0.001). There was no difference in the prevalence of grey crescent in glaucomatous or non-glaucomatous eyes (OR = 1.05, 95% CI 0.49 to 2.26). The prevalence of a grey crescent was inversely related to the prevalence of peripapillary atrophy (p = 0.001). CONCLUSIONS: The grey crescent needs to be recognised as a physiological variant in order to avoid falsely labelling eyes as having glaucomatous optic nerve damage.

Aged↗
PubMed2003

Prevalence of open-angle glaucoma in Iceland: Reykjavik Eye Study.

PURPOSE: To establish the age- and sex-specific prevalence of open-angle glaucoma (OAG) subsuming pseudoexfoliation (PEX) in the city of Reykjavik. METHODS: Participants 50 years of age and older who were part of the Reykjavik Eye Study and classified as having glaucoma were divided into three categories:Category 1: two or more of the following based on optic nerve stereophotograph reading: vertical cup to disc ratio (VCDR) 97.5th percentile (>0.7), focal glaucomatous disc change, C/D asymmetry of 97.5th percentile difference between eyes (>0.2) as well as glaucomatous visual field defect (GVFD). Category 2: 99.5th percentile of VCDR (>0.8) and 99.5% percentile difference between eyes (>/=0.3), without a GVFD. Category 3: VA<3/60 and IOP>99.5th percentile or VA <3/60 and evidence of filtering surgery. For a glaucoma suspect, one of the following was present: VCDR>99.5th percentile (>0.8), focal glaucomatous disc change, C/D asymmetry of 99.5th percentile (> or =0.3), GVFD only, IOP> or =23 mmHg (97.5 percentile). PEX was diagnosed by the presence of a central shield and/or a peripheral band on the anterior lens capsule. RESULTS: Of 42 persons (22 males and 20 females) with OAG, 13 (31.0%) had PEX. The minimum prevalence of OAG was 4.0% (42/1045) (95% CI 2.8-5.2) for those 50 years and older and 10.3% (95% CI 8.5-12.2) for PEX. The prevalence of OAG increases with age (OR=1.10/year, 95% CI 1.07-1.13, P=0.000) and the same applies for the prevalence of PEX, OR=1.10 (95% CI 1.07-1.12, P=0.000). CONCLUSION: There is a 10% annual increase for both OAG and PEX in persons 50 years and older.

Age Distribution↗
PubMed2001

Cortical lens opacification in Iceland. Risk factor analysis -- Reykjavik Eye Study.

PURPOSE: Cortical lens opacification has been associated with outdoor exposure and UV radiation more than other types of lens opacification. We studied risk factors for cortical lens opacification only, the most common as well as the earliest age related change we observe in the lens. METHODS: 1,045 persons, 583 females and 462 males, 50 years and older, underwent a detailed eye examination and answered a questionnaire. Participants with cortical lens opacification grade I, totalling 374 persons, were assigned to case-control study I, and to case-control study II those with cortical lens opacification grades II and III, totalling 82 subjects. 378 age and sex matched persons served as controls. RESULTS: Those who spent more than 4 hours/day outside on weekdays, in their 20's--30's and 40's--50's respectively, were found to have increased risk of moderate to severe cortical lens opacification. Thus the relative risk for grades II & III, was 2.80 (95% CI 1.01--7.80) and 2.91 (95% CI 1.13--9.62) respectively. Ageing and systemic cortical steroids use were also found to be risk factors. CONCLUSION: Outdoor exposure appears to be associated with increased risk of moderate to severe cortical lens opacification. Ageing is, however, the main risk factor.

Aged↗
PubMed2001

[Characteristics and frequency of cortical cataracts at an early stage (Reykjavik Eye Study in Iceland)].

BACKGROUND: The frequency and characteristics of cortical cataract localization within a dilated pupillary area were investigated in a population-based cataract epidemiological survey performed in the city of Reykjavik in Iceland. MATERIALS AND METHODS: Among 1045 randomly selected individuals, the right eyes of 277 persons with mild cortical lens opacification (Grade I) were selected for our study. The localization of cortical cataracts was examined using retroillumination images, which were divided into 56 circular and radial sections, and calculations were made of the percentages for each opacified area. A questionnaire was used to record the number of hours spent outdoors during week days, the time of the day and whether the subjects wore spectacles, sunglasses or hats when outside. RESULTS: The percentage of cortical opacification was significantly higher in the lower nasal quadrant than in all other quadrants (p < 0.05). Furthermore, the percentage of opacification localized in the lower nasal quadrant was higher in individuals with a longer history of outdoor activity than those without (p < 0.05). The percentage of opacification in individuals, who have had the habit of wearing sunglasses for outdoor activities lasting longer than half an hour during weekdays in their 20's and 30's was lower in all quadrants and statistically significantly lower in the upper temporal quadrant (p < 0.05) compared to those not wearing sunglasses. CONCLUSION: This suggests that wearing sunglasses is effective in preventing the development and/or progression of cortical cataracts.

Aged↗
PubMed2001

Pseudoexfoliation syndrome in Icelandic families.

AIM: To examine the distribution and clinical ophthalmic characteristics of pseudoexfoliation syndrome (pseudoexfoliation) and glaucoma in Icelandic families. METHODS: Icelandic families containing three or more members aged 70 or older with at least one member with pseudoexfoliation were identified. All family members over age 45 were invited to participate. Visual acuity, Goldmann applanation tonometry, gonioscopy, slit lamp examination before and after dilatation, and dilated fundus examination were performed on all available family members. Pertinent data were obtained from medical records, including ophthalmic history and a medical history of cardiovascular disease, cerebrovascular disease, systemic hypertension, and diabetes mellitus. Participants were classified according to affected status for pseudoexfoliation, glaucoma, and age related macular degeneration. RESULTS: Six families were identified who met the criteria for entry into the study. Of 94 family members who were invited to participate 82 were enrolled (87%). Of these 25 (30%) had pseudoexfoliation syndrome, 51 (62%) were unaffected, and six (7%) were suspects. At least one individual with pseudoexfoliation was identified in the second generation of every family. A parent with pseudoexfoliation was identified in all cases either by examination (4/6) or a review of ophthalmic records (2/6). In all cases the mother was the affected parent. The prevalence of glaucoma was significantly greater in the group with pseudoexfoliation (p <0.0001). Although the presence of age related macular degeneration (ARMD) was highly associated with the presence of pseudoexfoliation, the significance was lost after correction for age (p = 0.69). Although the sample size was small, no association between pseudoexfoliation affected status and cardiovascular disease, cerebrovascular disease, systemic hypertension, or diabetes mellitus was found. CONCLUSIONS: Multiple Icelandic families with pseudoexfoliation in two generations were identified. In all cases where determination was possible, transmission to the second generation was through an affected parent. In each case the affected parent was the mother. Pseudoexfoliation was strongly associated with the presence of glaucoma, but was not associated with either ARMD or systemic disease in this study. These data clearly indicate that pseudoexfoliation is a familial condition and although not conclusive, supports the hypothesis that pseudoexfoliation syndrome is genetically inherited.

Aged↗
PubMed2000

Mutations in corneal carbohydrate sulfotransferase 6 gene (CHST6) cause macular corneal dystrophy in Iceland.

PURPOSE: Macular corneal dystrophy (MCD) is subdivided into three immunophenotypes (MCD types I, IA and II). Recently, mutations in the carbohydrate sulfotransferase 6 gene (CHST6) were identified to cause MCD. The purpose of this study was to examine CHST6 for mutations in Icelandic patients with MCD type I. METHODS: Genomic DNA was extracted from leukocytes in the peripheral blood and the coding region of CHST6 was examined for mutations by polymerase chain reaction (PCR) and direct sequencing. RESULTS: Mutation analysis of the CHST6 coding region identified three different mutations in sixteen Icelandic patients with MCD type I. Eleven patients with MCD type I were homozygous for a C1075T mutation. One patient with MCD type I was found to be a compound heterozygous for C1075T and G1189C mutations. One family with MCD type I contained a 10 base pair insertion (ATGCTGTGCG) between nucleotides 707 and 708. In this family, two affected siblings had a homozygous insertion while both their affected mother and their affected maternal aunt had a heterozygous insertion and a heterozygous C1075T mutation. CONCLUSIONS: Three different nucleotide changes were identified in the coding region of CHST6 in sixteen Icelandic patients with MCD type I. All three of these alterations are predicted to affect the translated protein and each of them corresponded to a particular disease haplotype that we had previously reported in this population.

Base Sequence↗
PubMed2000

Physical and genetic mapping of the macular corneal dystrophy locus on chromosome 16q and exclusion of TAT and LCAT as candidate genes.

PURPOSE: Macular corneal dystrophy (MCD) is an inherited autosomal recessive disorder that has been subdivided into three immunophenotypes, MCD types I, IA and II. We previously mapped the MCD type I gene to chromosome 16q22 and suggested that the MCD type II gene was linked to the same region. The purpose of this study was to construct a genomic contig spanning the MCD region and to narrow the MCD critical interval by haplotype analysis. The TAT and LCAT genes were mapped to determine if they might be the MCD gene. METHODS: The MCD contig was constructed by screening YAC, PAC, and BAC libraries with microsatellite, STS and EST markers, employing a systematic "DNA walking" technique. Polymorphic markers mapped and ordered on the contig were used to screen the MCD affected individuals and their family members for haplotype analysis. RESULTS: Twenty-two YAC, 30 PAC, and 17 BAC clones were mapped to form the MCD contig. Markers mapped on the contig include 19 microsatellite, 14 STS, and 15 EST markers. Moreover, 18 novel STS markers were generated. Using the mapped and ordered microsatellite markers, haplotype analysis on 21 individuals with MCD type I or type II and their family members from Iceland narrowed the MCD interval to 3 overlapping PAC clones. In addition, the TAT and LCAT genes were mapped outside the MCD region. CONCLUSIONS: We established a genomic contig for the MCD region and dramatically narrowed the MCD critical interval. Mapping data show that the TAT and LCAT genes are not the cause of MCD.

Contig Mapping↗
PubMed2000

"With the rule" astigmatism is not the rule in the elderly. Reykjavik Eye Study: a population based study of refraction and visual acuity in citizens of Reykjavik 50 years and older. Iceland-Japan Co-Working Study Groups.

PURPOSE: To study refractive state and visual acuity in citizens of Reykjavik 50 years and older. METHODS: 1700 persons were randomly selected from the national population census. 1379 could be located and qualified whereof 1045 participated. Evaluation of refraction was performed using Nidek ARK 900 autorefracto-keratometer. Visual acuity was tested on a Snellen chart. RESULTS: The prevalence of hypermetropia increases with age by 0.3 D in five years. The prevalence of "against the rule" astigmatism increased on average 5.3% and oblique 3.9% in five years. Analysis of corneal astigmatism measured by keratometer shows an "against the rule" change with age. CONCLUSIONS: Hypermetropia increases by age. The prevalence of astigmatism increases and the axis turns to "against the rule". The changes in total astigmatism and corneal astigmatism is almost parallel which might indicate that the "against the rule" change is related to changes in the cornea.

Aged↗
PubMed2000

The Reykjavik Eye Study--prevalence of lens opacification with reference to identical Japanese studies.

PURPOSE: A population-based cataract epidemiological study, the Reykjavik Eye Study, was conducted to determine the prevalence and characteristics of lens opacities in Iceland. The results were compared with those from previous surveys in Japan to determine the influence of race and environmental factors. METHODS: 1,635 randomly selected residents of Reykjavik, Iceland, were enrolled, and among them, 1,045 responded and took part in the study. The subjects received ophthalmological examination of both the anterior and the posterior segments. Changes in the crystalline lens were examined and photographed under maximal pupillary dilation. Classification of the opacity types and grading of the extent of lens opacificiation were done using a standardized scheme, and the data were analyzed with Student's test, the chi(2) test and the Mantel-Haenszel test. RESULTS: The prevalence of lens opacities in subjects in their 50s, 60s, 70s and in those 80 years and older was 42.7, 61.0, 85.3 and 100%, respectively. Grade II and III lens opacities were found in 2. 2% of subjects in their 50s and in 10.5, 35.9 and 62.3% in their 60s, 70s, and over 80 years, respectively. Cortical opacities predominated in all age groups followed by nuclear opacities; subcapsular opacities, on the other hand, were quite rare. A unique type of opacity, i.e., granular opacity, seldom seen among the Japanese, was found in 6.6% of the Icelandic subjects. CONCLUSIONS: Our results show that cortical opacity is the major type of opacity in Icelandic subjects, although its prevalence was lower than that in the Japanese subjects. Interestingly, the first appearance of lens opacities of grades II and III in Icelanders was delayed by 10 years compared to the Japanese suggesting fewer or less severe risk factors for cataract formation in Iceland.

Aged↗
PubMed1999

Epidemiological studies on UV-related cataract in climatically different countries.

Cataract epidemiological surveys applying objective judgement through lens images in the climatically different places of Noto and Amami, Japan, Singapore and Reykjavik, Iceland yielded several significant results about the influence of solar UV. 1) The percentage of transparent and of lens opacification was significantly higher in the Reykjavik subjects than in the Singaporeans. 2) The percentages including early changes were higher in Amami and Singapore than in Noto and Reykjavik. 3) Progressed lens opacification was highest in Singapore. While the main type of lens opacification was cortical in Noto and Reykjavik, that of Singapore was nuclear. 4) A significant correlation between cortical opacification and the history of time spent outdoors was noticed. The UV risk for formation and/or progression of cortical opacification should be acceptable from the epidemiological standpoint.

Age Distribution↗
PubMed1998

Is pseudoexfoliation syndrome inherited? A review of genetic and nongenetic factors and a new observation.

Pseudoexfoliation (PEX) syndrome is the commonest identifiable cause of open-angle glaucoma worldwide. PEX is characterized clinically by small whitish deposits of fibrillar-granular material in the anterior segment of the eye. Despite its prevalence and potential for ophthalmic morbidity, surprisingly little is known about the etiology and pathogenesis of PEX. This article reviews the literature and presents evidence regarding genetic and nongenetic arguments for the etiology of pseudoexfoliation. Lines of evidence that support a genetic basis for PEX include transmission in two-generation families, twin studies, an increased risk of PEX in relatives of affected patients, and HLA studies. Nearly all pedigrees in the literature, and our own experience with PEX families in Iceland and Canada, suggest maternal transmission, raising the possibilities of mitochondrial inheritance, X-linked inheritance, and autosomal inheritance with genomic imprinting. A number of nongenetic factors have also been evaluated for their possible implication in the development of PEX. These include ultraviolet light, autoimmunity, slow virus infection, and trauma. It is possible that a combination of genetic and nongenetic factors may be involved in the etiology and pathogenesis of PEX, i.e. it may be a multifactorial disorder. Further studies with larger numbers of patients are needed to delineate more clearly the contribution of genetic (nuclear DNA, mitochondrial DNA or both) and nongenetic factors to the development of pseudoexfoliation syndrome and pseudoexfoliation glaucoma.

Autoimmunity↗
PubMed1996

Macular corneal dystrophy in Iceland. A clinical, genealogic, and immunohistochemical study of 28 patients.

BACKGROUND: The frequency of different types of macular corneal dystrophy (MCD) was determined in Iceland where MCD accounts for one third of every penetrating keratoplasty. METHODS: The authors determined the serum levels of antigenic keratan sulfate (aKS) in 27 patients with MCD and 53 unaffected family members by an enzyme-linked immunosorbent assay that uses an anti-KS monoclonal antibody (5-D-4). The authors also stained sections from 37 corneal buttons (including 2 regrafts) from 23 patients with MCD by the avidin-biotin complex method using the same anti-KS monoclonal antibody. RESULTS: Based on the serum analyses, 22 patients had MCD type I and 5 had MCD type II. The corneas from patients without detectable KS in the serum lacked immunohistochemical reactivity to the anti-KS antibody. Every MCD cornea examined from individuals with normal serum KS levels showed KS reactivity. All 53 unaffected siblings and parents carrying the recessive gene had normal serum KS levels. CONCLUSIONS: Macular corneal dystrophy types I (78.6%) and II (21.4%) both occur in Iceland. Members of affected sibships had only one of these types, not both. Nine patients with MCD type I and four persons with MCD type II belonged to a large pedigree in which individuals have been traced as far back as the beginning of the 16th century. The linking of patients with MCD types I and II in an inbred pedigree suggests that both types may be manifestations of the same abnormal gene rather than independent entities. The serum KS levels were not helpful in detecting heterozygous MCD carriers.

Adolescent↗
PubMed1996

Linkage of a gene for macular corneal dystrophy to chromosome 16.

Autosomal recessive macular corneal dystrophy (MCD) is a heterogeneous disorder leading to visual impairment. Sixteen American and Icelandic families (11 type I and 5 type II) were analyzed for linkage, by use of 208 polymorphic microsatellite markers. A significant maximum LOD score Zmax of 7.82 at a maximum recombination fraction (thetamax) of .06 was found with the 16q22 locus D16S518 for MCD type I. In addition, a peak LOD score of 2.50 at a recombination fraction of .00 was obtained for the MCD type II families, by use of the identical marker. These findings raise the possibility that MCD type II may be due to the same genetic locus that is involved in MCD type I.

Americas↗
PubMed1989

Macular corneal dystrophy in Iceland.

This study includes the fourteen Icelanders who had penetrating keratoplasty for macular corneal dystrophy during 1974 through 1988, and a further five patients whose deterioration of vision has so far not led to surgery. The clinical presentation, mode of inheritance and the course of the disease were similar to those seen in other studies. The genealogical part of this study indicates that the gene responsible for the disease was already present in Iceland in the 18th century. Though consanguinity, as usually defined, was found to be uncommon, the relatively small pool of genes in the Icelandic population which numbers at present about 250,000 has led to higher prevalence of macular corneal dystrophy than elsewhere. The histopathological findings concur with the conventional description of macular corneal dystrophy, with the exception of two patients with unusually severe photophobia. In these two cases, electron microscopy revealed that the most anteriorly situated deposits were sometimes associated with increased electron-density of small clusters of basal epithelial cells in the overlying epithelium, such cells also being reduced in size and exhibiting few organelles other than swollen mitochondria.

Adolescent↗
PubMed1987

Prevalence of ocular disease and blindness in a rural area in the eastern region of Iceland during 1980 through 1984.

The main emphasis in this study is on the three most common potentially blinding diseases in the age group 43 years and older, i.e. cataract, age related macular degeneration and open angle glaucoma. The prevalence of all three diseases increases with advancing age (P less than 0.001, corr. greater than 0.8). In the age group 63 years and older there is a statistically significant difference in the occurrence of cataracts between females and males (P less than 0.02). Females outnumber males and the former appear to develop cataract at an earlier age than men. Among persons 73 years of age and older there is a statistically significant difference in the occurrence of open angle glaucoma between males and females (P less than 0.05), whereby males outnumbered females. Persons with age related macular degeneration were divided into an exudative group and an atrophic group. There was no sex difference in the atrophic group, whereas females outnumber males by 2:1 in the exudative group, which is mainly accounted for by overrepresentation of females 83 years and older. Persons 83 years and older who had age related macular degeneration also had cataracts in all instances and open angle glaucoma in 23.8% of cases. Sixteen persons were legally blind i.e. had visual acuity less than or equal to 6/60 in the better eye or visual field less than 10 degrees in the better eye. Eight persons thereof, were greater than or equal to 83 years of age.

Adolescent↗