Gender differences in albumin and ascorbic acid in the vitreous antioxidant system.

Ascorbic acid is present at high concentrations in the vitreous and plays a central role in vitreous redox chemistry. Albumin is the main protein in the vitreous with antioxidant properties and occurs in different oxidation states, which can be used as redox indicators, but have not been studied in the vitreous. This study, therefore, addressed the vitreous redox state of cysteine-34 of albumin in relation to the ascorbic acid content, which has been suggested to exert a main function in detoxifying reactive oxygen in the vitreous. A total of 58 vitreous samples obtained from patients undergoing vitrectomy were analyzed for (i) human mercaptalbumin (HMA), the reduced thiol form; (ii) human non-mercaptalbumin1 (HNA1), a reversible oxidative modification with a disulfide at cysteine-34; and (iii) human non-mercaptalbumin2 (HNA2), a non-reversibly (highly) oxidized form of albumin; as well as (iv) ascorbic acid concentrations, to study possible relations. In addition, blood samples were taken to compare albumin redox state between plasma and the vitreous. Vitreous albumin showed greater variability in the redox state of cysteine-34 and a shift to the oxidized fractions compared to plasma albumin (P < 0.001). A strong positive relation was observed between the vitreous ascorbic acid concentrations and the reversibly oxidized form, HNA1 (P < 0.001), and a negative relation with the reduced form, HMA. Positive relations between ascorbic acid and HNA1 in the vitreous were stronger in men than in women. In contrast to HMA and HNA1, there was a distinct gender difference noted for the irreversibly oxidized form, HNA2. While males showed a positive relation between the vitreous ascorbic acid concentrations and HNA2, there was no correlation found with HNA2 in females. Our results support the view that ascorbic acid, by decreasing either directly or indirectly the concentrations of molecular oxygen, generates hydrogen peroxide, and that thiols, including HMA, are acting as antioxidants. This study for the first time provides evidence that vitreous albumin can be used as a marker molecule for the appearance of reactive oxygen species in the vitreous of patients undergoing vitrectomy. Moreover, it can be shown that there are gender differences in vitreous ascorbic acid and albumin concentrations as well as in oxidation state of vitreous albumin.

Quantifying the impact on navigation performance in visually impaired: Auditory information loss versus information gain enabled through electronic travel aids.

This study's purpose was to analyze and quantify the impact of auditory information loss versus information gain provided by electronic travel aids (ETAs) on navigation performance in people with low vision. Navigation performance of ten subjects (age: 54.9±11.2 years) with visual acuities >1.0 LogMAR was assessed via the Graz Mobility Test (GMT). Subjects passed through a maze in three different modalities: 'Normal' with visual and auditory information available, 'Auditory Information Loss' with artificially reduced hearing (leaving only visual information), and 'ETA' with a vibrating ETA based on ultrasonic waves, thereby facilitating visual, auditory, and tactile information. Main performance measures comprised passage time and number of contacts. Additionally, head tracking was used to relate head movements to motion direction. When comparing 'Auditory Information Loss' to 'Normal', subjects needed significantly more time (p<0.001), made more contacts (p<0.001), had higher relative viewing angles (p = 0.002), and a higher percentage of orientation losses (p = 0.011). The only significant difference when comparing 'ETA' to 'Normal' was a reduced number of contacts (p<0.001). Our study provides objective, quantifiable measures of the impact of reduced hearing on the navigation performance in low vision subjects. Significant effects of 'Auditory Information Loss' were found for all measures; for example, passage time increased by 17.4%. These findings show that low vision subjects rely on auditory information for navigation. In contrast, the impact of the ETA was not significant but further analysis of head movements revealed two different coping strategies: half of the subjects used the ETA to increase speed, whereas the other half aimed at avoiding contacts.

Prevalence of posterior vitreous detachment in glaucoma patients and controls.

PURPOSE: To evaluate the impact of oxidative stress - present in glaucoma - on the vitreous. We therefore compare the presence of early and late stages of posterior vitreous detachment (PVD) between patients with glaucoma and controls. METHODS: The vitreous state was evaluated by the combination of optical coherence tomography and ultrasound. The main outcome was the vitreous state classified into 'no PVD', 'initial PVD' and 'advanced PVD'. RESULTS: We evaluated the vitreous state in 48 patients with glaucoma (age: mean 66.5 ± 11.9 years; visual field deviation: mean 10.4 ± 6.8 dB) and compared the results with 101 previously investigated controls (age: mean 73.6 ± 9.3 years). After one-to-one matching on age and sex, ordinal logistic regression revealed that patients with glaucoma were significantly more likely to exhibit advanced PVD stages compared to non-glaucoma patients (OR 2.60, 95% confidence interval: 1.06-6.36, p = 0.037). CONCLUSION: Our results suggest that the presence or absence of PVD might be a valuable hint for diagnosing glaucoma - however, further research is needed to determine whether PVD can be used to supplement current glaucoma screening guidelines.

A test method for quantification of stimulus-induced depression effects on perceptual threshold in epiretinal prosthesis.

PURPOSE: As part of a clinical trial, an investigational epiretinal implant (IMI Intelligent Medical Implant) was implanted in a retinitis pigmentosa patient. The prosthesis was wirelessly controlled by a visual interface containing a microcamera, providing wireless data and energy transmission. Forty-nine (49) electrodes were used for pattern recognition. This study examined the changes of perceptual thresholds over time and its relation to long-term stimulation. The goal of the study was to introduce stimulus-related depression of perceptual threshold (StirDepth) measurements as a method to gain further insight into the safety profile of electrical stimulation. METHODS: The perceptual threshold was defined as the level of stimulation intensity at which a phosphene perception with a probability of 50% was detected using the Best-PEST method. StirDepth was measured by comparing the threshold changes immediately before and after a stimulation session of using three active electrodes and one passive electrode, which served as control. RESULTS: The initial threshold of the day remained stable over the observed period. In StirDepth measurement all thresholds raised significantly after the stimulation sessions. The threshold increase of the active electrodes never exceeded that of the inactive control electrode. CONCLUSIONS: StirDepth measurement is feasible in epiretinal implants. The prolonged stimulation raised no safety concerns in the patient. The threshold increase of both the active electrodes and the control electrode leads one to hypothesise that cognitive or neurophysiological effects are the cause rather than the desensitizing of the retinal network or incipient retinal damage.

Evolution of early changes at the vitreoretinal interface after cataract surgery determined by optical coherence tomography and ultrasonography.

PURPOSE: To evaluate the onset of posterior vitreous detachment (PVD) including early changes at the vitreoretinal interface after uneventful phacoemulsification in nonmyopic eyes using optical coherence tomography (OCT) and ultrasound. DESIGN: Prospective consecutive study. METHODS: Patients undergoing cataract surgery at our unit between January and October 2010 were recruited and examined with OCT and ultrasound preoperatively. Inclusion criteria were complete vitreoretinal attachment, no ocular pathology other than cataract, and no previous ocular surgery. All patients underwent phacoemulsification with intraocular lens implantation. Postoperatively, OCT and ultrasound were performed 1 month and 3 months after surgery. Exclusion criteria were axial length≥25 mm, lattice degeneration, intraoperative complications, and incomplete follow-up. RESULTS: Forty-nine eyes of 49 patients could be enrolled in the study. Some degree of PVD was noted in 29 eyes (59.2%) 1 month after surgery and in 35 eyes (71.4%) 3 months after surgery. Moreover, a significant decrease in prevalence of initial PVD and a corresponding increase of more advanced PVD stages throughout the duration of the study was observed. In patients older than 70 years some degree of PVD was diagnosed in 92.3% compared to 47.8% in patients younger than 70 years (P=.002). CONCLUSION: OCT facilitates the detection of early vitreoretinal separation that indicates initial PVD. After phacoemulsification the prevalence of some degree of PVD is consequently more frequent when supplementary OCT is used. Furthermore, OCT discloses a significant progression of PVD in the postoperative course. Patients older than 70 years are more likely to develop pseudophakic PVD.

Acute electrical stimulation of the human retina with an epiretinal electrode array.

PURPOSE: To determine the threshold charges needed for eliciting visual perceptions through acute electrical stimulation of the human retina in patients suffering from retinitis pigmentosa, using an epiretinal microelectrode array. METHODS: In a multicentre study, 20 patients (average age 55 years) with visual acuities ranging from 4/200 to no light perception were included. The stimulation procedure was performed during a pars plana vitrectomy, for a maximum of 45 min, by using a microcontact film with IrO(x) electrodes connected by cable to a current generator. After repeated stimulation and threshold charge determination, the microelectrode array was removed. RESULTS: Nineteen of 20 patients stated in the postoperative interviews that they experienced one or more visual perceptions with close time correlation to single stimulation events. Minimum threshold charges needed to generate visual perceptions could be measured and verified in 15 patients. The charge level ranged from 20 to 768 nC with single or multiple electrodes. One patient suffered a retinal detachment during the procedure; this patient's retina was successfully reattached. There were no further adverse reactions observed during the 3-month follow-up. CONCLUSION: Acute epiretinal stimulation of the human retina, using a microelectrode array, can elicit visual perceptions in blind patients with retinitis pigmentosa.

Prevalence of early and late stages of physiologic PVD in emmetropic elderly population.

PURPOSE: To investigate the early and late stages of posterior vitreous detachment (PVD) in the foveal area in correlation with age and gender. METHODS: Three hundred and thirty-five emmetropic eyes of 271 Caucasian patients (216 women/119 men) were examined by optical coherence tomography (OCT) and ultrasound (US). Eyes were classified into groups according to the patients age (up to 69.9; 70-74.9; 75-79.9; over 80 years) and to the clinical findings [Vitreous state: Detached in US; Detached in OCT; Foveal adhesion (FA); Attached vitreous]. RESULTS: The mean age was 76 ± 8 ranging from 44 to 89 years in female and 72 ± 10 ranging from 46 to 87 years in male subjects. The vitreous was attached in 32% of all eyes, 18.5% had FA, 18.5% were detached in OCT and 68% were detached in US. While prevalence of FA decreases with increasing age, OCT-diagnosed detachments did not change significantly with age. Between the ages of 70 and 75, an increase in PVD rates occurred. The prevalence of PVD was similar in both genders. Women were significantly older than men in the late-stage PVD in the eyes. CONCLUSION: The use of OCT and US enabled us to detect a partial or total PVD in 80% of the eyes. A sudden increase in late-stage PVD between the ages of 70 and 75 was observed, correlating with the reported age prevalence of various macular diseases. In contrast to myopics, both genders of elderly emmetropics have a similar prevalence of PVD.

Evaluation of limbal and pars plana silicone oil removal in aphakic eyes.

PURPOSE: To compare limbal and pars plana silicone oil removal (SOR) in aphakic eyes and to evaluate the acute effect of silicone oil flow to the corneal endothelium. METHODS: Sixteen aphakic patients with silicone oil endotamponade requiring SOR were recruited for this prospective study and randomly scheduled for limbal or pars plana SOR. The central corneal thickness (CCT), visual acuity (VA) and intraocular pressure were measured preoperatively, on the first postoperative day and 4 months after surgery. Endothelial cell density (ECD) was measured preoperatively and at the end of follow-up. The in vitro study was performed on ten enucleated porcine eyes. Corneoscleral discs were prepared and fixed on artificial anterior chamber followed by 2.5-mm limbal incision and 5-ml silicone oil injection in six cases and 5 ml balanced salt solution (BSS) in four cases. RESULTS: The ECD decreased by 239.2 ± 86.7 (13.9%) and 86.7 ± 22.4 cells/mm(2) (5%) after limbal (n = 8) and pars plana SOR (n = 8), respectively (p < 0.001 for both). The difference between the groups was significant (p < 0.001). A significant increase in CCT and corresponding decrease in VA was noted on the first postoperative day using both procedures. At the end of follow-up, the CCT and VA were comparable to initial values. Postoperative hypotony (≤6 mmHg) was observed more frequently after limbal SOR. In the experiment, lamellar abrasions of corneal endothelium were observed after silicone oil injection, whereas no changes were observed after BSS injection. CONCLUSION: Limbal SOR causes more considerable damage to the corneal endothelium than the pars plana approach because of mechanical abrasion.

Encircling band, laser retinopexy and lens removal as standard procedure in complicated retinal detachment shows a good clinical outcome.

PURPOSE: To evaluate vitrectomy in conjunction with the use of perfluorocarbon, cerclage, laser retinopexy, lens removal and silicone oil as surgical treatment of proliferative vitreoretinopathy associated with retinal detachment. METHODS: Sixty-two eyes of 62 patients were treated for complicated retinal detachment following failed prior scleral buckling. Outcome measures were; retinal reattachment rate 6 months after silicone oil removal, status of the retina, visual acuity (VA), duration of silicone tamponade and frequency of reoperations. RESULTS: The final reattachment rate was 95%. Reoperations had to be performed in 25% of patients. Eighty-one per cent of these patients received one and 19% two or more operations following silicone oil implantation. The mean time to reoperation was 1.8 ± 1.4 months. Silicone oil was removed after 5.6 ± 4.1 months following the last vitreoretinal procedure in 90%, respectively, 95% with attached retina. Five per cent experienced retinal detachment after silicone oil removal. At the end of follow-up, the mean VA was 0.13 ± 0.26 Snellen. Seventy per cent of patients achieved a vision of 20/200 or better (mean 0.25 ± 0.27). CONCLUSION: Our study demonstrates good final outcomes when a rigorous surgical approach was used. Furthermore, this standard procedure reduces the need for reoperations and consequently improves the functional outcome.

Anatomy and function of the macula after surgery for retinal detachment complicated by proliferative vitreoretinopathy.

PURPOSE: To investigate the macular changes following silicone oil removal after surgery for complicated retinal detachment (RD) with proliferative vitreoretinopathy (PVR). DESIGN: Retrospective interventional case series. METHODS: setting: Vienna, Austria. study population: Thirty-nine patients with attached retina after silicone oil removal following previous vitrectomy and silicone oil tamponade for complicated RD and PVR grade C3 and worse. observation procedures: Examination of macular anatomy with biomicroscopy, optical coherence tomography (OCT), and fluorescein angiography (FA). Macular function was tested by assessing logMAR distance visual acuity (VA) using Early Treatment Diabetic Retinopathy Study (ETDRS) charts and reading acuity and reading speed using a standardized test (Radner charts). main outcome measures: Macular anatomy, VA, reading acuity, and reading speed. RESULTS: The macula was clinically normal in five patients (12.8%). Retinal pigment epithelium (RPE) irregularities were found in nine patients (23.1%). Eight patients (20.5%) had macular pucker, seven (18.0%) had cystoid macular edema (CME), and 10 (25.6%) had subretinal fibrosis. The mean VA of all patients was logMAR 0.67 +/- 0.68 (range, -0.1 to 3.0). Six eyes did not achieve reading acuity. The distance VA of the remaining 33 eyes was logMAR 0.44 +/- 0.29 and their mean reading acuity was logRAD 0.62 +/- 0.35, with a reading speed ranging from 55 to 240 words per minute. CONCLUSIONS: We found macular changes in 87% of the patients, one-third thereof being eligible for further treatment (macular pucker or CME). Thus, the majority of these patients do not seem to be eligible for a further improvement of anatomic or functional outcome.

Influence of laser in situ keratomileusis and laser epithelial keratectomy on patients' reading performance.

PURPOSE: To evaluate the influence of laser in situ keratomileusis (LASIK) and laser-assisted subepithelial keratectomy (LASEK) on reading performance regarding reading acuity, reading speed based on print size, maximum reading speed, and critical print size. SETTING: Department of Ophthalmology, University of Vienna, Vienna, and Auge-und-Laser, Medicent Baden, Austria. METHODS: Fifty-two eyes of 34 patients (26 eyes per group) were studied. Best corrected LogMAR visual acuity (Early Treatment Diabetic Retinopathy Study charts), reading acuity, and reading speed were tested monocularly before LASIK or LASEK and 3 weeks after surgery. Reading acuity (LogRAD) and reading speed were determined with the standardized Radner reading charts. RESULTS: Preoperatively, the distance visual acuity and reading acuity were comparable between the LASIK and LASEK patients. Reading speed measurements also showed no statistical difference. Three weeks after refractive surgery, no statistically significant differences in the preoperative measures and between the 2 surgical procedures could be found in any tested parameters. The mean distance visual acuity was LogMAR -0.02 +/- 0.06 (SD) (LASIK) and LogMAR -0.05 +/- 0.07 (LASEK). The mean reading acuity was LogRAD 0.00 +/- 0.12 (97.7% of LogMAR) (LASIK) and LogRAD 0.04 +/- 0.16 (93.7% of LogMAR) (LASEK). The mean maximum reading speed was 235 +/- 35 words per minute (LASIK) and 240 +/- 37 words per minute (LASEK), and the mean critical print size was at LogRAD 0.48 +/- 0.19 (LASIK) and 0.49 +/- 0.17 (LASEK). CONCLUSIONS: In a standardized reading test setting, no significant effects of LASIK and LASEK on individual reading performance could be evaluated. This indicates that patients can expect to retain their normal visual function after refractive surgery with these 2 procedures under full light conditions.