Regulation of retinal oxygen metabolism in humans during graded hypoxia.

Animal experiments indicate that the inner retina keeps its oxygen extraction constant despite systemic hypoxia. For the human retina no such data exist. In the present study we hypothesized that systemic hypoxia does not alter inner retinal oxygen extraction. To test this hypothesis we included 30 healthy male and female subjects aged between 18 and 35 years. All subjects were studied at baseline and during breathing 12% O2 in 88% N2 as well as breathing 15% O2 in 85% N2. Oxygen saturation in a retinal artery (SO2art) and an adjacent retinal vein (SO2vein) were measured using spectroscopic fundus reflectometry. Measurements of retinal venous blood velocity using bidirectional laser Doppler velocimetry and retinal venous diameters using a Retinal Vessel Analyzer (RVA) were combined to calculate retinal blood flow. Oxygen and carbon dioxide partial pressure were measured from earlobe arterialized capillary blood. Retinal blood flow was increased by 43.0 ± 23.2% (P < 0.001) and 30.0 ± 20.9% (P < 0.001) during 12% and 15% O2 breathing, respectively. SO2art as well as SO2vein decreased during both 12% O2 breathing (SO2art: -11.2 ± 4.3%, P < 0.001; SO2vein: -3.9 ± 8.5%, P = 0.012) and 15% O2 breathing (SO2art: -7.9 ± 3.6%, P < 0.001; SO2vein: -4.0 ± 7.0%, P = 0.010). The arteriovenous oxygen difference decreased during both breathing periods (12% O2: -28.9 ± 18.7%; 15% O2: -19.1 ± 16.7%, P < 0.001 each). Calculated oxygen extraction did, however, not change during our experiments (12% O2: -2.8 ± 18.9%, P = 0.65; 15% O2: 2.4 ± 15.8%, P = 0.26). Our results indicate that in healthy humans, oxygen extraction of the inner retina remains constant during systemic hypoxia.

[Clinical characteristics of penetrating ocular injuries with intraocular foreign body. Part I. Pathogenesis and clinical features]. / Charakterystyka kliniczna urazów penetrujacych narzadu wzroku z obecnoscia ciala obcego wewnatrz galki ocznej. Czesc I. Patogeneza i obraz kliniczny.

Intraocular foreign bodies (IOFBs), are the major cause of penetrating ocular trauma and the most serious problem is the resulting impairment of visual function. In this paper, based on published reports and their clinical experience, authors discuss questions of pathogenesis, epidemiology and clinical features of IOFB injuries. Special attention was paid on primary and secondary complications, which include mechanical lesions of the ocular tissues, metallosis and endophthalmitis.

[Clinical characteristics of penetrating ocular injuries with intraocular foreign body. Part II. Diagnostics and treatment]. / Charakterystyka kliniczna urazów penetrujacych narzadu wzroku z obecnoscia ciala obcego wewnatrz galki ocznej. Czesc II. Diagnostyka i leczenie.

Ocular trauma remains a major cause of blindness, particularly in the working-age population. Intraocular foreign bodies (IOFBs ), frequently accompany penetrating ocular injuries and can lead to increased ocular morbidity. In this paper, based on published reports and their authors clinical experience, we discuss questions of advantages and disadvantages of three imaging methods (radiology, ultrasound and tomography), and evaluate the value of these methods in the diagnosis of IOFBs. Authors discuss also management options in patients with IOFB injuries and describe techniques of primary surgical repair and foreign body removal, especially pars plana vitrectomy.

[Intraocular and intraorbital foreign bodies characteristics in patients with penetrating ocular injury]. / Charakterystyka cial obcych wnikajacych do wnetrza galki i oczodolu powodujacych u pacjenta przenikajacy uraz narzadu wzroku.

PURPOSE: To determine clinical features of intraocular and intraorbital foreign body (IOFB) injuries. MATERIAL AND METHODS: 62 patients with IOFB injury were retrospectively reviewed. Data on age, sex, activity at the time of injury, initial visual acuity and presenting clinical features were recorded. Special attention was paid on foreign bodies characteristics. Factors analyzed included: material, quantity and size of IOFB, site of entrance wound and final IOFB location. RESULTS: The mean patient age was 38.1 years. All but one patient were male. Hammering and chiselling were the most common activities at the time of injury. 93.5% of patients had single IOFB. Metallic foreign body comprised 85.5% of all cases. The average IOFB size was 3.9 x 15.1 mm. 83.9% of IOFBs were located inside the globe, among them: 46.1% in the anterior segment; 44.2% in the vitreous and the rest in the posterior part of globe. The most frequent entrance wound site was cornea (59.7%). Initial visual acuity was worse or equal 5/50 in 50% of the cases. Patients with greater size of IOFB had worse initial visual acuity. The most common clinical features, presenting at the time of injury, were corneal wound (64.5%), lens lesion (33.9%), endophthalmitis (29%) and vitreous hemorrhage (25.8%). CONCLUSIONS: The majority of patients with IOFB injury were young male. Tool-related activities, particularly hammering, were more likely to cause of IOFB injuries. Single metallic foreign body occurred much more frequently. Cornea was the most frequent site of entrance wound. The vitreous and the anterior segment were the most common final location of IOFB. Increasing IOFB size was associated with worse initial visual acuity. IOFB injury has been found to be associated with a lot number of the ocular tissues lesions.

[Late complications after penetrating ocular injuries caused by intraocular and intraorbital foreign bodies]. / Pózne powiklania po urazach przenikajacych narzadu wzroku spowodowanych wniknieciem cial obcych do wnetrza galki i oczodolu.

PURPOSE: To evaluate late complications in patients with penetrating ocular injuries caused by intraocular or intraorbital foreign bodies (IOFBs). MATERIAL AND METHODS: We reviewed 58 posttraumatic patients with IOFBs removed by external electromagnet or intraocular forceps. The patients underwent a follow-up examinations at 1 to 7 years after trauma. We noted final visual acuity, frequency and type of complications and following surgical treatment. RESULTS: Final visual acuity of 5/50 or more was obtained in 65.5% of patients. Ocular complications were found in 50 patients (86.2%). The most frequent consequence of past trauma was corneal scar (58.6%), cataract (44.8%), and retinal detachment (20.7%). 37 patients (63.7%), required the next surgical interventions. 23 patients 139.6%), underwent posttraumatic cataract extraction, 9 (15.5%)--pars plana vitrectomy for retinal detachment or vitreoretinal proliferations, 5 (8.6%)--scleral buckling procedure, 3 (5.2%)--antiglaucoma surgery, and 2 (3.4%)--enucleation. CONCLUSIONS: Penetrating ocular injuries caused by IOFBs were often complicated with corneal scar, cataract and retinal detachment. More than 2/3rd of patients required subsequent surgical interventions.

[Modern neurosurgical techniques to remove intraorbital foreign bodies--report of two cases]. / Zastosowanie nowoczesnych technik neurochirurgicznych podczas usuwania cial obcych z oczodolu--opis dwøch przypadków.

PURPOSE: To indicate the usefulness of modern neurosurgical techniques to remove intraorbital foreign bodies, not removed during primary ophthalmological surgical intervention. PATIENT 1: A 29-year-old man, struck with a bottle, with a piece of glass located at the top of the right orbit. During the primary ophthalmological intervention--orbitotomy accessed through the conjunctiva of the fornix of the upper eyelid and the second cut through the wound in the eyelid--the foreign body was not removed. The patient was moved to the Department of Neurosurgery, where 3 days after the injury the 30 mm x 7 mm piece of glass was successfully removed with the aid of neuronavigation system. The surgical approach was through a cut in the right eyebrow and the foreign body was found to be located in the back-top part of the orbit. PATIENT 2: A 30-year-old man, hit with a piece of wood, with an organic foreign body (wood), located in the mid-lower and medial part of the right orbit. During the primary ophthalmological operation--orbitotomy accessed through the conjunctiva of the fornix of the lower eyelid--the foreign body was not removed. The patient was moved to the Department of Neurosurgery, where the surgeon unsuccesfuly attempted to remove the foreign body through the wound in the conjunctiva of the fornix of the lower eyelid with the aid of neuronavigation. In this situation the endoscopic technique with access through the nose was used. The mid part of the medial orbit wall was removed and partially fragmented piece of wood was located with the use of the neuronavigation. The foreign body was located in the middle part of the orbit, near the medial wall. It was removed in four pieces measuring: 8 mm x 3 mm, 8 mm x 4 mm, 15 mm x 5 mm, 18 mm x 6 mm.

[Giant cell arteritis--case report]. / Olbrzymiokomórkowe zapalenie tetnic--opis przypadku.

Giant cell arteritis is a systemic disease of unknown origin. Vasculitis involves large and medium-sized vessels. Frequent clinical manifestations include characteristic headache in the temporal area, jaw or tongue claudication, apathy, fatigue, weight loss. The incidence of ocular involvement is reported in up to 70% patients. The most common and serious ophthalmic presentation is arteritic anterior ischemic optic neuropathy, which can lead to irreversible visual loss. Only early and aggressive steroid therapy may prevent this dangerous complication. The authors presented a case of a 68-years-old woman with giant cell arteritis. The main visual manifestation of this disease was anterior ischemic optic neuropathy.

[The influence of the pseudoexfoliation syndrome on cataract development]. / Wplyw zespolu pseudoeksfoliacji na rozwój zacmy.

Pseudoexfoliation syndrome (PEX) is a chronic, systemic, connective tissue disease. Its hallmark is the accumulation of an abnormal, amyloid-like material in the anterior segment tissues of the eye. PEX is one of the risk factors in the development of lens opacification. The aim of the paper is a presentation of the current knowledge on the relationship between pseudoexfoliation syndrome and cataract. Special attention is paid to pathogenetic and epidemiologic factors.

Retinal hemodynamic effects of antioxidant supplementation in an endotoxin-induced model of oxidative stress in humans.

PURPOSE: The Age-Related Eye Disease Study 1 (AREDS 1) has shown that nutritional supplementation with antioxidants and zinc modifies the natural course of AMD. It is presumed that the supplements exert their beneficial effects by ameliorating oxidative stress due to the scavenging of reactive oxygen species (ROS). We have shown in a human model that under oxidative stress induced by administration of lipopolysaccharide (LPS) the vasoconstrictor response of retinal vessels to oxygen breathing is diminished. This reduced vascular response to hyperoxia was previously shown to be normalized by the AREDS 1 supplements. In the present study, we tested the hypothesis that the response can also be restored by a different antioxidant formulation. METHODS: This randomized, double-masked, placebo-controlled parallel group study included 40 healthy volunteers. On each study day, retinal red blood cell (RBC) flow and the reactivity of retinal RBC flow to hyperoxia were investigated in the absence and presence of 2 ng/kg LPS. Between the two study days, subjects received either the supplement or placebo for 14 days. RESULTS: Before supplementation LPS reduced retinal arterial vasoconstriction (P < 0.001) and reactivity of retinal RBC flow (P = 0.03) in response to 100% oxygen breathing. Two weeks of supplementation did not affect baseline retinal RBC flow, but normalized the LPS-induced change in the response to hyperoxia. The arterial vasoconstrictor response during LPS and 100% oxygen breathing was 4.1 ± 1.0% after administration of placebo and 10.6 ± 0.9% after supplementation (P = 0.005). The response of RBC flow to 100% oxygen breathing during LPS was 52.2 ± 2.1% after administration of placebo and 59.5 ± 2.0% after supplementation (P = 0.033). CONCLUSIONS: Our data show that the supplement used in the present study can normalize the response of retinal RBC flow to hyperoxia under LPS administration. This indicates that supplementation can prevent endothelial dysfunction induced by oxidative stress, which is assumed to play a role in the pathophysiology of AMD. (ClinicalTrials.gov number, NCT00914576.).

Flicker-induced retinal vasodilatation is not dependent on complement factor H polymorphism in healthy young subjects.

PURPOSE: The complement factor H (CFH) tyrosine 402 histidine (Y402H, rs1061170) variant is known to be significantly associated with age-related macular degeneration (AMD). Whether this genetic variant may impact retinal blood flow regulation is largely unknown. This study investigated whether flicker-induced vasodilation, an indicator for the coupling between neural activity and blood flow, is altered in subjects carrying the rs1061170 risk allele. METHODS: One hundred healthy subjects (aged between 18 and 45 years) were included in this study. Retinal blood flow regulation was tested by assessing retinal vessel calibres in response to stimulation with diffuse flicker light. Retinal vascular flicker responses were determined with a Dynamic Vessel Analyzer (DVA). In addition, genotyping for rs1061170 was performed. RESULTS: Eighteen subjects were homozygous for the risk allele C, 50 were homozygous for the ancestral allele T, and 31 subjects were heterozygous (CT). One subject had to be excluded from data evaluation, as no genetic analysis could be performed due to technical difficulties. Baseline diameters of retinal arteries (p = 0.39) and veins (p = 0.64) were comparable between the three groups. Flicker-induced vasodilation in both retinal arteries (p = 0.38) and retinal veins (p = 0.62) was also comparable between the three studied groups. CONCLUSIONS: Our data indicate that homozygous healthy young carriers of the C risk allele at rs1061170 do not show abnormal flicker-induced vasodilation in the retina. This suggests that the high-risk genetic variant of CFH polymorphism does not impact neuro-vascular coupling in healthy subjects.

Retinal oxygen metabolism during normoxia and hyperoxia in healthy subjects.

PURPOSE: To characterize retinal metabolism during normoxia and hyperoxia in healthy subjects. METHODS: Forty-six healthy subjects were included in the present study, and data of 41 subjects could be evaluated. Retinal vessel diameters, as well as oxygen saturation in arteries and veins, were measured using the Dynamic Vessel Analyzer. In addition, retinal venous blood velocity was measured using bidirectional laser Doppler velocimetry, retinal blood flow was calculated, and oxygen and carbon dioxide partial pressures were measured from arterialized capillary blood from the earlobe. Measurements were done during normoxia and during 100% oxygen breathing. RESULTS: Systemic hyperoxia caused a significant decrease in retinal venous diameter (-13.0% ± 4.5%) and arterial diameter (-12.1% ± 4.0%), in retinal blood velocity (-43.4% ± 7.7%), and in retinal blood flow (-57.0% ± 5.7%) (P < 0.001 for all). Oxygen saturation increased in retinal arteries (+4.4% ± 2.3%) and in retinal veins (+19.6% ± 6.2%), but the arteriovenous oxygen content difference significantly decreased (-29.4% ± 19.5%) (P < 0.001 for all). Blood oxygen tension in arterialized blood showed a pronounced increase from 90.2 ± 7.7 to 371.3 ± 92.7 mm Hg (P < 0.001). Calculated oxygen extraction in the eye decreased by as much as 62.5% ± 9.5% (P < 0.001). CONCLUSIONS: Our data are compatible with the hypothesis that during 100% oxygen breathing a large amount of oxygen, consumed by the inner retina, comes from the choroid, which is supported by previous animal data. Interpretation of oxygen saturation data in retinal arteries and veins without quantifying blood flow is difficult. (ClinicalTrials.gov number, NCT01692821.).

Optic nerve head blood flow autoregulation during changes in arterial blood pressure in healthy young subjects.

AIM: In the present study the response of optic nerve head blood flow to an increase in ocular perfusion pressure during isometric exercise was studied. Based on our previous studies we hypothesized that subjects with an abnormal blood flow response, defined as a decrease in blood flow of more than 10% during or after isometric exercise, could be identified. METHODS: A total of 40 healthy subjects were included in this study. Three periods of isometric exercise were scheduled, each consisting of 2 minutes of handgripping. Optic nerve head blood flow was measured continuously before, during and after handgripping using laser Doppler flowmetry. Blood pressure was measured non-invasively in one-minute intervals. Intraocular pressure was measured at the beginning and the end of the measurements and ocular perfusion pressure was calculated as 2/3*mean arterial pressure -intraocular pressure. RESULTS: Isometric exercise was associated with an increase in ocular perfusion pressure during all handgripping periods (p < 0.001). By contrast no change in optic nerve head blood flow was seen. However, in a subgroup of three subjects blood flow showed a consistent decrease of more than 10% during isometric exercise although their blood pressure values increased. In addition, three other subjects showed a consistent decline of blood flow of more than 10% during the recovery periods. CONCLUSION: Our data confirm previous results indicating that optic nerve head blood flow is autoregulated during an increase in perfusion pressure. In addition, we observed a subgroup of 6 subjects (15%) that showed an abnormal response, which is in keeping with our previous data. The mechanisms underlying this abnormal response remain to be shown.

Regulation of optic nerve head blood flow during combined changes in intraocular pressure and arterial blood pressure.

In the choroid, there is evidence that blood flow does not only depend on ocular perfusion pressure (OPP), but also on absolute mean arterial pressure (MAP) and intraocular pressure (IOP). The present study included 40 healthy subjects to investigate whether such behavior is also found in the optic nerve head (ONH). The ONH blood flow (ONHBF) was studied using laser Doppler flowmetry during a separate increase in IOP and MAP as well as during a combined elevation. Mean arterial pressure was increased by isometric exercise and IOP by the suction method. During both, the change in ONHBF was less pronounced than the change in OPP indicating autoregulation. Correlation analysis was performed for the combined experiments after pooling all data according to IOP and MAP values. A correlation between ONHBF and MAP was found at IOPs 25 mm Hg (P<0.001), but not at IOPs>25 mm Hg (P=0.79). Optic nerve head blood flow and IOP were significantly correlated (P<0.001), and ONHBF was only slightly dependent on MAP. The data of the present study indicate a complex regulation of ONHBF during combined changes in MAP and IOP. Our results may be compatible with myogenic mechanisms underlying autoregulation, and indicate better ONHBF regulation during an increase in MAP than during an increase in IOP.