Asbjorg Geirsdottir

Retinal vessel oxygen saturation in healthy individuals.

PURPOSE We measured oxygen saturation in retinal vessels of healthy eyes to determine the effects of age, sex, and cardiovascular parameters, as well as the reliability of the measurements and topographic differences. METHODS The Oxymap T1 retinal oximeter is based on a fundus camera. It simultaneously captures retinal images at two different wavelengths and estimates retinal vessel oxygen saturation. Mean saturation of main retinal arterioles and venules was measured in 120 healthy individuals aged 18-80 years (median 47 years). Of the 120 participants 44 (37%) were male (49 years) and 76 (63%) female (44 years). RESULTS Oxygen saturation was 92.2 ± 3.7% (mean ± SD) in retinal arterioles and 55.6 ± 6.3% in venules. No significant difference in oxygen saturation was found between left and right eyes. The inferotemporal quadrant had lower oxygen saturation in arterioles and venules (P < 0.0001). Arteriolar oxygen saturation was stable with age. Venular oxygen saturation in males decreased by 1.9 ± 0.6% (mean ± SEM) per 10 years of age (P = 0.003) and by 0.7 ± 0.4% in females (P = 0.068). Arteriovenous (AV) difference increased by 1.5 ± 0.5% per 10 years in males (P = 0.004) and 1.0 ± 0.4% (P = 0.007) in females. For every 10 mm Hg increase in ocular perfusion pressure, oxygen saturation in arterioles increased by 0.9 ± 0.4% (P = 0.024) and in venules by 1.2 ± 0.7% (P = 0.075). CONCLUSIONS Retinal arteriolar oxygen saturation is stable in healthy individuals, while there is a significant decrease in venular oxygen saturation with age in males and a similar trend in females. AV difference increases significantly with age for both sexes. Our study provided normative data for spectrophotometric retinal oximetry in the Caucasian population.

A rare nonsynonymous sequence variant in C3 is associated with high risk of age-related macular degeneration

Through whole-genome sequencing of 2,230 Icelanders, we detected a rare nonsynonymous SNP (minor allele frequency = 0.55%) in the C3 gene encoding a p.Lys155Gln substitution in complement factor 3, which, following imputation into a set of Icelandic cases with age-related macular degeneration (AMD) and controls, associated with disease (odds ratio (OR) = 3.45; P = 1.1 × 10−7). This signal is independent of the previously reported common SNPs in C3 encoding p.Pro314Leu and p.Arg102Gly that associate with AMD. The association of p.Lys155Gln was replicated in AMD case-control samples of European ancestry with OR = 4.22 and P = 1.6 × 10−10, resulting in OR = 3.65 and P = 8.8 × 10−16 for all studies combined. In vitro studies have suggested that the p.Lys155Gln substitution reduces C3b binding to complement factor H, potentially creating resistance to inhibition by this factor. This resistance to inhibition in turn is predicted to result in enhanced complement activation.

Retinal oxygen metabolism in healthy subjects and glaucoma patients

Background To test whether retinal oxygen metabolism is different in glaucoma patients compared with healthy subjects. Methods This was a two-centre study where retinal vessel oxygen saturation was measured in glaucoma patients and healthy individuals with a non-invasive spectrophotometric retinal oximeter. Visual fields were obtained in the glaucoma patients. Results No statistical difference was found in retinal oxygen saturation in arterioles (p=0.16), venules (p=0.16) and arteriovenous difference (p=0.24) when all glaucoma patients (n=74) were compared with healthy individuals (n=89). When patients with advanced glaucoma (visual field mean defect (MD ≥ 10 dB, n=21)) were compared with healthy individuals, the oxygen saturation in venules was higher in glaucoma patients (58.2%±5.4% vs 53.8%±6.4%; p=0.0054, mean±SD) and the arteriovenous difference was lower in glaucoma patients (36.4%±4.7% vs 39.5%±5.7%; p=0.021). In glaucoma patients with mild glaucoma (visual field MD ≤ 5 dB, n=33), no statistical differences were found in retinal oxygen saturation compared with healthy individuals. Conclusions Glaucoma patients with advanced glaucoma have higher oxygen saturation in venules and lower arteriovenous difference in oxygen saturation compared with healthy individuals. The decreased arteriovenous difference in severe glaucoma may be related to lower oxygen consumption secondary to neuropathy.

Retinal oxygen metabolism in exudative age-related macular degeneration.

To determine whether retinal vessel oxygen saturation in patients with exudative age‐related macular degeneration (AMD) is different from that of a healthy population.

Population-based incidence of exudative age-related macular degeneration and ranibizumab treatment load.

Background/aims The use of intravitreal vascular endothelial growth factor antibodies for exudative age-related macular degeneration (AMD) has stressed ophthalmology services and drug budgets throughout the world. The authors study the population-based incidence of exudative AMD in Iceland and the use of intravitreal ranibizumab in a defined population. Methods This is a prospective study of 439 consecutive patients aged 60 years and older with exudative AMD starting intravitreal ranibizumab for exudative AMD in Iceland from March 2007 to December 2009. All patients initially received three consecutive ranibizumab injections, with regular follow-up visits and re-treatment as needed. Results In total, 517 eyes from 439 patients received treatment for exudative AMD (mean age 79 years). The annual incidence of exudative AMD in the population 60 years and older is 0.29%. The incidence increased with advancing age, double for patients 85 years and older compared with those 75–79 years. Approximately 2400 ranibizumab injections per 100 000 persons aged 60 years and older were given each year for exudative AMD. Conclusions These data allow an estimation of the incidence of exudative AMD in a Caucasian population and the treatment load with ranibizumab, which may help plan anti-vascular endothelial growth factor treatment programmes and estimate costs.

Enucleation in Iceland 1992-2004: study in a defined population.

Purpose:  To determine the incidence rate as well as causative diagnoses and surgical indications of enucleation in Iceland during the years 1992–2004.

Oxygen metabolism in age related macular degeneration

Purpose To determine whether oxygen saturation in retinal vessels of patients with age‐related macular degeneration (AMD) is different from that of a healthy population.

Geographic atrophy and choroidal melanoma located 3 mm apart

Editor, G eographic atrophy (GA) in agerelated macular degeneration (AMD) is rare in individuals under the age of 70 years. The prevalence in those aged 60–69 years has been estimated to be 1% in the USA (Friedman et al. 2004) and 1.2% in Iceland (Jonasson et al. 2003). The risk of malignant transformation of a choroidal nevus in the White population is low, with an annual incidence in the 60–69-year-old age group of 0.02% (Singh et al. 2005). We report a case of malignant melanoma developing from a pigmented lesion, judged to be a choroidal nevus located only 3 mm from an area of GA in a 66-year-old man. At 61 years of age, the subject’s vision deteriorated rapidly in both eyes over the course of 6 months. Visual acuity (VA) was 6 ⁄ 24 OD and 6 ⁄ 9 OS. Geographic atrophy was present in both eyes, but was more prominent in the right eye. A choroidal nevus was seen superior to the optic disc (Fig. 1A). With time the atrophic lesions increased in size concurrently with a slow decrease in VA. When the subject reached 64 years of age, fluorescein angiography confirmed that exudative AMD had developed in his left eye. Two years later, his VA had decreased to 2 ⁄ 60 OD and 6 ⁄ 60 OS and the atrophic area in his right eye was approximately 3000 lm in diameter. However, over the course of < 22 months the pigmented lesion had increased in size and formed a solid homogenous, 2.5-mm thick tumour (Fig. 1B). Features predictive of a developing malignant melanoma include male gender, presence of symptoms, increased tumour thickness ‡ 2.0 mm, proximity of tumour to foveola of < 3.0 mm, tumour margin adjacent to the optic disc and the presence of orange pigment and subretinal fluid (Shields et al. 2000; Singh et al. 2006). Moreover, tumour growth over a short period is one of the main characteristics of choroidal melanoma (Singh et al. 2006). Our patient was male and had apparent symptoms and the tumour possessed all the aforementioned features. Therefore, the tumour was considered to be a malignant melanoma of the choroid and was treated as such with a 20-mm notch Ruthenium 106 applicator, to a dose of 80 Gy, at a depth of 3.5 mm to include the thickness of the sclera. After the treatment the tumour showed slow, constant regression over the next few years. It is remarkable that in the same fundus, only 3 mm apart, one group of cells undergoes atrophy while another multiplies rapidly.