Nonconjugate adaptation of human saccades to anisometropic spectacles: Meridian-specificity

Abstract Recently it has been demonstrated that saccades become different in size in the two eyes if a subject is adapted to anisometropic spectacles, which provide visual images of different magnitude to the two eyes. These nonconjugate adaptations adequately meet the requirements of those spectacles and, once acquired, they persist (with some reduction) even during monocular viewing. We now demonstrate that such nonconjugate adaptations of saccades can be meridian-specific, if there is a pressure for such meridian-specificity. This pressure was provided by means of a cylindrical spectacle-lens. Adaptations along a vertical, horizontal or oblique meridian did not transfer to the orthogonal meridian. These results demonstrate a capability of saccadic adaptation to deal with calibration problems restricted not only to one eye, but even to one specific plane of muscular action. Our results also suggest that the meridian-specific adaptations of oblique saccades take place at a stage before the decomposition of motor commands into separate horizontal and vertical components. The meridian-specific nonconjugacies were also expressed in smooth-pursuit eye movements. Post-saccadic drift adapted only along the horizontal meridian

Is Hyperopia an Important Risk Factor for PACG in the Dutch Population?—A Case Control Study

Objectives. To determine if hyperopia is a risk factor for primary angle-closure glaucoma (PACG) in the Dutch population and to identify other biometrical parameters as risk factors for PACG including axial length (AL), anterior chamber depth (ACD), and k values. Methods. The study population consisted of PACG patients that had undergone a laser peripheral iridotomy (LPI). The control group consisted of age- and gender-matched cataract patients. The main outcome was hyperopia (spherical equivalent ≥+0.5 dioptres) measured with IOL Master or autorefractor. Refractive error, ACD, AL, and k values were tested with a Mann-Whitney U test and by logistic regression. Results. 117 PACG patients and 234 controls were included (mean age = 80 years ± 3.6). The prevalence of hyperopia in patients and controls was 69.6% and 61.1%, respectively (Fisher’s test P=0.076). Mann-Whitney U test showed no statistically significant relation with refractive error (P=0.068) or k values (P=0.607). In contrast, ACD and AL were statistically significant (P<0.001). Tested with logistic regression, only ACD was a significant predictor of PACG (P<0.001). Conclusion. There was no statistically significant correlation between refractive error and PACG. ACD was strongly correlated, though, with PACG, whereas AL turned out to be a less significant risk factor

Predicting visual function from the measurements of retinal nerve fiber layer structure

Purpose: To develop and validate a method for predicting visual function from retinal nerve fibre layer (RNFL) structure in glaucoma. Methods: RNFL thickness (RNFLT) measurements from GDxVCC scanning laser polarimetry (SLP) and visual field (VF) sensitivity from standard automated perimetry were made available from 535 eyes from three centres. In a training dataset, structure-function relationships were characterized using linear regression and a type of neural network: Radial Basis Function customised under a Bayesian framework (BRBF). These two models were used in a test dataset to 1) predict sensitivity values at individual VF locations from RNFLT measurements and 2) predict the spatial relationship between VF locations and positions at a peripapillary RNFLT measurement annulus. Predicted spatial relationships were compared with a published anatomical structure-function map. Results: Compared with linear regression, BRBF yielded a nearly two-fold improvement (P<0.001; paired t-test) in performance of predicting VF sensitivity in the test dataset (mean absolute prediction error of 2.9dB (standard deviation (SD) 3.7dB) versus 4.9dB (SD 4.0dB)). The predicted spatial structure-function relationship accorded better (P<0.001; paired t-test) with anatomical prior knowledge when the BRBF was compared with the linear regression (median absolute angular difference of 15° versus 62°). Conclusions: The BRBF generates clinically useful relationships that relate topographical maps of RNFL measurement to VF locations and allows the VF sensitivity to be predicted from structural measurements. This method may allow clinicians to evaluate structural and functional measures in the same domain. It could also be generalized to use other structural measures

Progression Detection of Glaucoma from Polarimetric Images

Detecting glaucoma progression is crucial for assessing the effectivity of the treatment. This paper describes three methods for detecting progression related changes in polarimetric images of the retinal nerve fiber layer (NFL), both on a global and on a local scale. Detecting global changes proved not to be feasible due to poor reproducibility of the measurements at the pixel level. Local progression on the other hand could be detected. A distribution based approach did not work, but locating specific areas with minimum size and minimum NFL decrease did give relevant results. The described algorithm yielded a TPR of 0.42 and an FPR of 0.095 on our datasets. It proved to be able to outline suspect areas that show NFL reductio

Differences in clinical presentation of primary open-angle glaucoma between African and European populations

PURPOSE: Primary open‐angle glaucoma (POAG) has been reported to occur more frequently in Africans, and to follow a more severe course compared to Europeans. We aimed to describe characteristics of POAG presentation and treatment across three ethnic groups from Africa and one from Europe. METHODS: We ascertained 151 POAG patients from South African Coloured (SAC) and 94 South African Black (SAB) ethnicity from a university hospital in South Africa. In Tanzania, 310 patients were recruited from a university hospital and a referral hospital. In the Netherlands, 241 patients of European ancestry were included. All patients were over 35 years old and had undergone an extensive ophthalmic examination. Patients were diagnosed according to the ISGEO criteria. A biogeographic ancestry analysis was performed to estimate the proportion of genetic African ancestry (GAA). RESULTS: The biogeographic ancestry analysis showed that the median proportion of GAA was 97.6% in Tanzanian, 100% in SAB, 34.2% in SAC and 1.5% in Dutch participants. Clinical characteristics at presentation for Tanzanians, SAB, SAC and Dutch participants, respectively: mean age: 63, 57, 66, 70 years (p < 0.001); visual acuity in the worse eye: 1.78, 1.78, 0.3, 0.3 LogMAR (p < 0.001); maximum intraocular pressure of both eyes: 36, 34, 29, 29 mmHg (p (anova)  < 0.001); maximum vertical cup to disc ratio (VCDR) of both eyes: 0.90, 0.90, 0.84, 0.83 (p < 0.001); mean central corneal thickness: 506, 487, 511, 528 μm (p < 0.001). Fourteen percent of Tanzanian patients presented with blindness (<3/60 Snellen) in the better eye in contrast to only 1% in the Dutch. CONCLUSION: In this multi‐ethnic comparative study, Sub‐Saharan Africans present at a younger age with lower visual acuity, higher IOP, larger VCDR, than SAC and Dutch participants. This indicates the more progressive and destructive course in Sub‐Saharan Africans

A Novel Redox Method for Rapid Production of Functional Bi-Specific Antibodies For Use in Early Pilot Studies

We demonstrate here a rapid alternative method for the production of functional bi-specific antibodies using the mild reducing agent 2-mercaptoethanesulfonic acid sodium salt (MESNA). Following reduction of a mixture of two monoclonal antibodies with MESNA to break inter heavy chain bonds, this solution is dialysed under oxidising conditions and antibodies are allowed to reform. During this reaction a mixture of antibodies is formed, including parental antibodies and bi-specific antibody. Bi-specific antibodies are purified over two sequential affinity columns. Following purification, bi-specificity of antibodies is determined in enzyme-linked immunosorbent assays and by flow cytometry. Using this redox method we have been successful in producing hybrid and same-species bi-specific antibodies in a time frame of 6–10 working days, making this production method a time saving alternative to the time-consuming traditional heterohybridoma technology for the production of bi-specific antibodies for use in early pilot studies. The use of both rat and mouse IgG antibodies forming a rat/mouse bi-specific antibody as well as producing a pure mouse bi-specific antibody and a pure rat bi-specific antibody demonstrates the flexibility of this production method