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The lack of a positive Bielschowsky head tilt test (BHTT) is commonly seen as an indicator that superior oblique paresis (SOP) is not present. This study investigated the influence of fusion on the BHTT in unilateral SOP.We analyzed vertical fusional vergence using our eye-tracking haploscope and the value of BHTT difference (BHTTD) in 11 patients who were diagnosed with congenital unilateral SOP and able to fuse.Patients used one of three different mechanisms of vertical vergence to achieve fusion. The three fusional mechanisms were associated with a significantly different BHTTD (p 0.05). Seven of the eleven patients used vertical recti-mediated fusion and had a mean BHTTD ± SD of 21.7 ± 6.3 prism diopters (PD). Three of these patients whom we measured after a patch test for at least 30 min showed a decreased BHTTD (12.7 ± 3.8 PD). Three of the eleven patients used a mixed (oblique/rectus) fusional mechanism and had a mean BHTTD ± SD of 9.3 ± 8.6 PD. Of these patients, the one whom we measured after patching showed an increase of 11 PD in BHTTD. The remaining patient used oblique muscle-mediated fusion and had a BHTTD of only 3 PD that increased to 21 PD after patching. One explanation for this BHTT behavior in the latter patient involves lingering vergence adaptation of the "paretic" superior oblique muscle (SOM) and contralateral inferior oblique muscle, which makes these muscles more effective when activated, as is the case on ipsilateral head tilt (part of the ocular counter-roll mechanism), lessening the expected increase in hyperdeviation. Similarly, in our patients with mixed fusion, the vergence-adapted "paretic" SOM and contralateral superior rectus muscle are activated on ipsilateral and contralateral tilt, respectively, lessening the hyperdeviation in both directions. In the other seven patients, however, the vergence-adapted ipsilateral inferior rectus muscle and contralateral superior rectus muscle are activated on contralateral tilt, accentuating the BHTTD.Depending upon the specific muscles used for vertical fusion, the BHTTD is decreased or increased. The presence of a large BHTTD points to lingering or persisting fusional tonus involving the vertical rectus muscles. The lack of a positive BHTT does not rule out the diagnosis of SOP, but rather may be caused by lingering or persevering fusional tonus involving the oblique muscles. Performing the BHTT after a patch test for a minimum of 30 minutes may be necessary to reveal the BHTTD, supporting the diagnosis of SOP.Das Fehlen eines positiven Bielschowsky-Kopfneigetests (BHTT) gilt gemeinhin als Indikator dafür, dass keine Trochlearisparese (SOP) vorliegt. In dieser Studie wurde der Einfluss der Fusion auf den BHTT bei einseitiger SOP untersucht.Wir analysierten die vertikale fusionale Vergenz mithilfe unseres Eye-Tracking-Haploskops und den Betrag der BHTT-Differenz (BHTTD) bei 11 Patienten, bei denen eine kongenitale einseitige SOP diagnostiziert wurde und die fusionieren konnten.Die Patienten verwendeten 1 von 3 Mechanismen der vertikalen fusionalen Vergenz. Die 3 Fusionsmechanismen waren mit einer signifikant unterschiedlichen BHTTD verbunden (p 0,05). Sieben der 11 Patienten nutzten die vertikal-Recti-vermittelte Fusion und hatten eine mittlere BHTTD ± SD von 21,7 ± 6,3 Prismendioptrien (PD). Drei dieser Patienten, die wir nach einem mindestens 30-minütigen Patch-Test gemessen haben, wiesen eine verringerte BHTTD auf (12,7 PD ± 3,8 PD). Drei der 11 Patienten benutzten einen gemischten Fusionsmechanismus (Obliquus/Rectus) und hatten eine mittlere BHTTD ± SD von 9,3 ± 8,6 PD. Der eine Patient von diesen, den wir nach dem Patching gemessen haben, wies einen Anstieg der BHTTD um 11 PD auf. Der verbleibende Patient nutzte die durch die Obliqui-vermittelte Fusion und hatte eine BHTTD von nur 3 PD, die sich nach dem Patching auf 21 PD erhöhte. Eine Erklärung für das BHTTD-Verhalten des letztgenannten Patienten ist die anhaltende Vergenzanpassung des „paretischen“ Obliquus superior (SOM) und des kontralateralen Obliquus inferior, die diese Muskeln effektiver macht, wenn sie aktiviert werden, wie es bei der ipsilateralen Kopfneigung der Fall ist (Teil des okulären Gegenrollmechanismus), wodurch die erwartete Zunahme des Höhenschielens verringert wird. In ähnlicher Weise werden bei unseren Patienten mit gemischter Fusion der vergenzadaptierte „paretische“ SOM und der kontralaterale Rectus superior bei ipsilateraler bzw. kontralateraler Neigung aktiviert, wodurch das Höhenschielen in beide Richtungen verringert wird. Bei den anderen 7 Patienten sind jedoch der vergenzadaptierte ipsilaterale Rectus inferior und der kontralaterale Rectus superior bei kontralateraler Neigung aktiviert, wodurch die BHTTD verstärkt wird.Je nachdem, welche Muskeln für die vertikale Fusion verwendet werden, ist die BHTTD verringert oder erhöht. Das Vorhandensein einer großen BHTTD weist auf einen anhaltenden oder persistierenden Fusionstonus unter Beteiligung der vertikalen Recti hin. Das Fehlen eines positiven BHTT schließt die SOP-Diagnose nicht aus, sondern kann durch einen anhaltenden oder persistierenden Fusionstonus unter Beteiligung der schrägen Augenmuskeln verursacht werden. Die Durchführung des BHTT nach einem mindestens 30-minütigen Patch-Test kann notwendig sein, um die BHTTD hervorzuheben, die die Diagnose einer SOP unterstützt.

The quality of donor corneal stroma, which makes up about 90% of total corneal thickness, is likely to be one of the main, if not the major, limiting factor(s) for success of deep anterior lamellar and penetrating keratoplasty. These are surgical procedures that involve replacing part or all of the diseased corneal layers, respectively, by donated tissue, the graft, taken from a recently deceased individual. However, means to evaluate stromal quality of corneal grafts in eye banks are limited and lack the capability of high-resolution quantitative assessment of disease indicators. Full-field optical coherence microscopy (FF-OCM), permitting high-resolution 3D imaging of fresh or fixed ex vivo biological tissue samples, is a non-invasive technique well suited for donor cornea assessment. Here we describe a method for the qualitative and quantitative analysis of corneal stroma using FF-OCM. The protocol has been successfully applied to normal donor corneas and pathological corneal buttons, and can be used to identify healthy and pathologic features on both the macroscopic and microscopic level, thereby facilitating the detection of stromal disorders that could compromise the outcome of keratoplasty. By improving the graft quality control, this protocol has the potential to result in better selection (and rejection) of donor tissues and hence decreased graft failure.

To investigate whether detection of disconjugacy of eye movements during attempted fixation, or interocular position instability, may serve as a single sensitive test for amblyopia.Binocular eye movements were recorded at 500 Hz using the EyeLink 1000 eye tracker (SR Research Ltd., Kanata, Ontario, Canada) and analyzed using EyeLink software and Matlab (MathWorks, Natick, MA, USA). Eight subjects (four amblyopes, one successfully treated amblyope, and three non-amblyopes: 7 - 44 years) were asked to fixate on a stationary cross subtending 0.5° at 57 cm. Interocular position instability was quantified by calculating the minimum area bivariate contour ellipse (BCEA) encompassing 68% of the difference between right and left eye position points during 20-second viewing epochs. For statistical analysis, BCEA values, as well as visual acuity and stereoacuity, were normalized by base-10 logarithm transformation.The amblyopic subjects with persistent vision loss (one anisometropic, two strabismic, one deprivation; uncorrected visual acuity range 20/60 - 20/300, corrected stereoacuity range nil-400 arcsec) showed significantly higher interocular position instability (larger 68% BCEAs) than the non-amblyopic subjects (uncorrected visual acuity range 20/20 - 20/800, corrected stereoacuities of 20 arcsec) and the successfully treated strabismic amblyope (to the 20/20 level of visual acuity and 70 arcsec of stereoacuity) during binocular viewing trials; p 0.01. Interocular position stability was strongly correlated with stereoacuity (in that better stereoacuity was associated with lower 68% BCEAs; r = 0.95), but not with visual acuity (r = 0.20).Interocular position instability appears to differentiate amblyopic from non-amblyopic subjects and appears to improve after successful treatment. Interocular position instability may therefore prove to be a single sensitive test for the presence of amblyopia. As a difference measure, it is inherently less susceptible to head motion and calibration error, as well as to conjugate eye motion, and as such is expected to be somewhat immune to latent nystagmus. Interocular position instability may also be useful to guide treatment, especially in preverbal children, and to assess the efficacy of novel treatments. Further research is required to establish optimal interocular position instability thresholds and to determine how specific this measure is to amblyopia.Es wird untersucht, ob der Nachweis der Diskonjugation der fixierenden Augenbewegungen beim Fixationsversuch oder der Instabilität der interokularen Augenposition als ein einziger sensitiver Test für Amblyopie dienen kann.Binokulare Augenbewegungen wurden mit dem EyeLink 1000 Eye Tracker (SR Research Ltd., Ontario, Kanada) bei 500 Hz aufgezeichnet und mit der EyeLink-Software und Matlab (Mathworks, Natick, MS) analysiert. Acht Probanden (4 Amblyope, 1 erfolgreich behandelter Amblyoper, 3 Nichtamblyope; Alter: 7 – 44 Jahre) fixierten ein stationäres Kreuz (0,5°) in 57 cm Entfernung. Die Instabilität der interokularen Augenposition wurde quantifiziert, indem die bivariate Konturellipse mit minimaler Fläche (BCEA) berechnet wurde, die 68% der Differenz zwischen den Positionspunkten des rechten und des linken Auges während 20-sekündiger Betrachtungsepochen umfasste. Für die statistische Analyse wurden die BCEA-Werte sowie die Sehschärfe und die Stereoakuität durch eine Logarithmentransformation zur Basis 10 normalisiert.Die amblyopen Probanden mit fortbestehendem Sehverlust (1 anisometrop, 2 strabismisch, 1 depriviert; unkorrigierte Sehschärfe 20/60 – 20/300, korrigierte Stereoakuität 0 – 400 Bogensekunden) zeigten bei binokularen Beobachtungen eine signifikant höhere Instabilität der interokularen Augenposition (größere 68% BCEAs) als die nicht amblyopen Probanden (unkorrigierte Sehschärfe 20/20 – 20/800, korrigierte Stereoakuitäten von 20 Bogensekunden) und der erfolgreich behandelte strabismische Amblyope (Sehschärfe auf 20/20-Niveau und 70 Bogensekunden Stereoakuität); p 0,01. Die Stabilität der interokularen Augenposition war stark mit der Stereoakuität korreliert (bessere Stereoakuität war mit niedrigeren 68% BCEAs assoziiert; r = 0,95), nicht aber mit der Sehschärfe (r = 0,20).Die Instabilität der interokularen Augenposition scheint amblyope von nicht amblyopen Personen zu unterscheiden und scheint sich nach erfolgreicher Behandlung zu verbessern. Die Instabilität der interokularen Augenposition könnte sich daher als ein einziger sensitiver Test für das Vorliegen einer Amblyopie erweisen. Als Differenzmaß ist sie inhärent weniger anfällig für Kopfbewegungen und Kalibrierungsfehler sowie für konjugierte Augenbewegungen und dürfte daher gegen latenten Nystagmus weitgehend immun sein. Die Instabilität der interokularen Augenposition kann auch nützlich sein, um die Behandlung zu steuern, insbesondere bei präverbalen Kindern, und um die Wirksamkeit neuer Behandlungen zu beurteilen. Weitere Forschungsarbeiten sind erforderlich, um optimale Schwellenwerte für die Instabilität der interokularen Augenposition festzulegen und um zu bestimmen, wie spezifisch dieses Maß für die Amblyopie ist.

International audience; Eye movements are commonly seen as an obstacle to high-resolution ophthalmic imaging. In this context we study the natural axial movements of the in vivo human eye and show that they can be used to modulate the optical phase and retrieve tomographic images via time-domain full-field optical coherence tomography (TD-FF-OCT). This approach opens a path to a simplified ophthalmic TD-FF-OCT device, operating without the usual piezo motor-camera synchronization. The device demonstrates in vivo human corneal images under the different image retrieval schemes (2-phase and 4-phase) and different exposure times (3.5 ms, 10 ms, 20 ms). Data on eye movements, acquired with a spectral-domain OCT with axial eye tracking (180 B-scans/s), are used to study the influence of ocular motion on the probability of capturing high-signal tomographic images without phase washout. The optimal combinations of camera acquisition speed and amplitude of piezo modulation are proposed and discussed.

International audience; Significance: Optical coherence tomography (OCT) allows high-resolution volumetric three-dimensional (3D) imaging of biological tissues in vivo. However, 3D-image acquisition can be time-consuming and often suffers from motion artifacts due to involuntary and physiological movements of the tissue, limiting the reproducibility of quantitative measurements.Aim: To achieve real-time 3D motion compensation for corneal tissue with high accuracy.Approach: We propose an OCT system for volumetric imaging of the cornea, capable of compensating both axial and lateral motion with micron-scale accuracy and millisecond-scale time consumption based on higher-order regression. Specifically, the system first scans three reference B-mode images along the C-axis before acquiring a standard C-mode image. The difference between the reference and volumetric images is compared using a surface-detection algorithm and higher-order polynomials to deduce 3D motion and remove motion-related artifacts.Results: System parameters are optimized, and performance is evaluated using both phantom and corneal (ex vivo) samples. An overall motion-artifact error of

Eye movements are commonly seen as an obstacle to high-resolution ophthalmic imaging. In this context we study the natural axial movements of in vivo human eye and show that they can be used to modulate the optical phase and retrieve tomographic images via time-domain full-field optical coherence tomography (TD-FF-OCT). This approach opens a path to a simplified ophthalmic TD-FF-OCT device, operating without the usual piezo motor-camera synchronization. The device demonstrates in vivo human corneal images under different image retrieval schemes (2-phase and 4-phase) and different exposure times (3.5 ms, 10 ms, 20 ms).

We present an automated data analysis procedure for clinical spectral-domain OCT, capable of correcting instrument-related hyperreflective artifacts, and its application to normal corneas. Quantitative parameters related to corneal transparency are extracted from 85 eyes.

Heterogeneities of biological tissues can strongly affect light propagation at large depths by distorting the initial wavefront. Inspired by previous works in acoustics, we have developed a matrix approach to Full-Field Optical Coherence Tomography (FF-OCT) to push back the fundamental limit of aberrations and multiple scattering. An analysis of the correlations of the matrix allows to correct for aberrations and forward multiple scattering over multiple isoplanatic areas (contrary to classic adaptive optics). Here, we report on the application of this approach to the imaging of the monkey cornea and the quantitative measurement of the corneal transparency.

Purpose To provide quantitative parameters for assessment of human donor corneal stroma by imaging stromal features of diseased and normal human corneas with full-field optical coherence microscopy (FFOCM), using confocal microscopy (CM) and histology as reference techniques. Methods Bowman's layer (BL) thickness and keratocyte density were assessed ex vivo in 23 human donor corneas and 27 human pathological corneas (keratoconus and other corneal disorders) with FFOCM, CM and histology. Stromal backscattering was assessed with FFOCM. Additionally, 10 normal human corneas were assessed in vivo with CM. Results In FFOCM, the logarithm of the normalized stromal reflectivity was a linear function of stromal depth (R2 = 0.95) in human donor corneas. Compared with keratoconus corneas, human donor corneas featured higher BL thickness (p = 0.0014) with lower coefficient of variation (BL-COV; p = 0.0002), and linear logarithmic stromal reflectivity with depth (higher R2, p = 0.0001). Compared with other corneal disorders, human donor corneas featured lower BL-COV (p = 0.012) and higher R2 (p = 0.0001). Using the 95% confidence limits of the human donor cornea group, BL thickness 18.6% (79%; 100%) and R2

International audience; Loss of corneal transparency, as occurs with various pathologies, infections, immune reactions, trauma, aging, and surgery, is a major cause of visual handicap worldwide. However, current means to assess corneal transparency are extremely limited and clinical and eye-bank practice usually involve a subjective and qualitative observation of opacities, sometimes with comparison against an arbitrary grading scale, by means of slit-lamp biomicroscopy. Here, we describe a novel objective optical data analysis-based method that enables quantifiable and standardized characterization of corneal transparency from depth-resolved corneal images, addressing the demand for such a means in both the laboratory and clinical ophthalmology setting. Our approach is based on a mathematical analysis of the acquired optical data with respect to the light attenuation from scattering processes in the corneal stroma. Applicable to any depth-resolved corneal imaging modality, it has been validated by means of full-field optical coherence tomographic microscopy (FF-OCT or FF-OCM). Specifically, our results on ex-vivo corneal specimens illustrate that 1) in homogeneous tissues, characterized by an exponential light attenuation with stromal depth (z), the computation of the scattering mean-free path (ls) from the rate of exponential decay allows quantification of the degree of transparency; 2) in heterogeneous tissues, identified by significant deviations from the normal exponential z -profile, a measure of exponential-decay model inadequacy (e.g., by computation of the Birge ratio) allows the estimation of severity of stromal heterogeneity, and the associated depth-dependent variations around the average ls enables precise localization of the pathology.

Lack of corneal transparency is a major cause of blindness worldwide. However, means to assess corneal transparency are limited and in current clinical and eye-bank practice usually involve a subjective and qualitative observation of opacities, sometimes with comparison against an arbitrary grading scale, by means of slit-lamp biomicroscopy. To address this unmet need, we have developed a method for corneal transparency assessment based on a new optical data analysis-based approach. Our method allows the objective extraction of quantitative parameters (including the scattering mean-free path, ls, a major indicator of scattering extent and thus of transparency of a medium) based on a physical model of corneal transparency and has been validated by laboratory experiments, using high-resolution, ex-vivo “full-field” optical coherence tomography (FF-OCT). Here, we apply our algorithm to depth-resolved spectral domain OCT (SD-OCT) images of in-vivo corneas and demonstrate the feasibility of our approach by means of four representative clinical cases. Specifically, we illustrate its potential in discriminating between the four clinical cases and, if applicable, deriving the scattering mean-free path as a quantitative measure of corneal transparency from objective analysis of stromal light backscattering (attenuation of the coherent mean) with SD-OCT. This measure may be related to, or expressed as, Strehl ratio reduction and thus retinal PSF broadening. As such, our approach not only has the potential to supply the demand for an objective means to quantify corneal transparency in the clinical setting, but also to create an association with visual function.

We report on a matrix approach of optical imaging that allows to overcome aberration and multiple scattering issues in microscopy. This allows in-depth diffraction-limited imaging of biological media over a wide field-of-view (FOV).

We demonstrate the feasibility of deriving quantitative measures of corneal transparency from objective analysis of stromal light backscattering with full-field optical coherence tomography (FF-OCT), addressing an unmet need in ophthalmology.

This study relates to eye fixation systems with combined optical and audio systems. Many devices for eye diagnostics and some devices for eye therapeutics require the patient to fixate on a small target for a certain period of time, during which the eyes do not move and data from substructures of one or both eyes are acquired and analyzed. With young pediatric patients, a monotonously blinking target is not sufficient to retain attention steadily. We developed a method for modulating the intensity of a point fixation target using sounds appropriate to the child's age and preference. The method was realized as a subsystem of a Pediatric Vision Screener which employs retinal birefringence scanning for detection of central fixation. Twenty-one children, age 2–18, were studied. Modulation of the fixation target using sounds ensured the eye fixated on the target, and with appropriate choice of sounds, performed significantly better than a monotonously blinking target accompanied by a plain beep. The method was particularly effective with children of ages up to 10, after which its benefit disappeared. Typical applications of target modulation would be as supplemental subsystems in pediatric ophthalmic diagnostic devices, such as scanning laser ophthalmoscopes, optical coherence tomography units, retinal birefringence scanners, fundus cameras, and perimeters.

This talk reviews ongoing work towardsin-vivocharacterization and deep imaging of the human eye, primarily for the purpose of quantifying corneal transparency, for which to date no objective clinical tool exists.

Despite obvious improvements in visualization of the in vivo cornea through the faster imaging speeds and higher axial resolutions, cellular imaging stays unresolvable task for OCT, as en face viewing with a high lateral resolution is required. The latter is possible with FFOCT, a method that relies on a camera, moderate numerical aperture (NA) objectives and an incoherent light source to provide en face images with a micrometer-level resolution. Recently, we for the first time demonstrated the ability of FFOCT to capture images from the in vivo human cornea1. In the current paper we present an extensive study of appearance of healthy in vivo human corneas under FFOCT examination. En face corneal images with a micrometer-level resolution were obtained from the three healthy subjects. For each subject it was possible to acquire images through the entire corneal depth and visualize the epithelium structures, Bowman’s layer, sub-basal nerve plexus (SNP) fibers, anterior, middle and posterior stroma, endothelial cells with nuclei. Dimensions and densities of the structures visible with FFOCT, are in agreement with those seen by other cornea imaging methods. Cellular-level details in the images obtained together with the relatively large field-of-view (FOV) and contactless way of imaging make this device a promising candidate for becoming a new tool in ophthalmological diagnostics.

We present an optical coherence tomography (OCT) imaging system that effectively compensates unwanted axial motion with micron-scale accuracy. The OCT system is based on a swept-source (SS) engine (1060-nm center wavelength, 100-nm full-width sweeping bandwidth, and 100-kHz repetition rate), with axial and lateral resolutions of about 4.5 and 8.5 microns respectively. The SS-OCT system incorporates a distance sensing method utilizing an envelope-based surface detection algorithm. The algorithm locates the target surface from the B-scans, taking into account not just the first or highest peak but the entire signature of sequential A-scans. Subsequently, a Kalman filter is applied as predictor to make up for system latencies, before sending the calculated position information to control a linear motor, adjusting and maintaining a fixed system-target distance. To test system performance, the motioncorrection algorithm was compared to earlier, more basic peak-based surface detection methods and to performing no motion compensation. Results demonstrate increased robustness and reproducibility, particularly noticeable in multilayered tissues, while utilizing the novel technique. Implementing such motion compensation into clinical OCT systems may thus improve the reliability of objective and quantitative information that can be extracted from OCT measurements.

We report on a reflection matrix approach of optical imaging that allows to overcome aberration and multiple scattering issues in microscopy. This allows an in-depth diffraction-limited imaging of biological media over a wide field-of-view.

Full-field Optical Coherence Tomography (FFOCT) offers aberration independent resolution. This property is particularly useful for eye imaging, as micrometer features are visible without adaptive optics (AO). Diffraction-limited in vivo corneal and retinal images are demonstrated.

According to the World Health Organization (WHO), corneal diseases alongside with cataract and retinal diseases are major causes of blindness worldwide. For the 95.5% of corneal blindness cases, prevention or rehabilitation could have been possible without negative consequences for vision, provided that disease is diagnosed early. However, diagnostics at the early stage requires cellular-level resolution, which is not achieved with routinely used Slit-lamp and OCT instruments. Confocal microscopy allows examination of the cornea at a resolution approaching histological detail, however requires contact with a patient’s eye. The recently developed full-field OCT technique, in which 2D en face tangential optical slices are directly recorded on a camera, was successfully applied for ex vivo eye imaging. However, in vivo human eye imaging has not been demonstrated yet. Here we present a novel non-contact full-field OCT system, which is capable of imaging in air and, therefore, shows potential for in vivo cornea imaging in patients. The first cellular-level resolution ex vivo images of cornea, obtained in a completely non-contact way, were demonstrated. We were able to scan through the entire cornea (400 µm) and resolve epithelium, Bowman’s layer, stroma and endothelium. FFOCT images of the human cornea in vivo were obtained for the first time. The epithelium structures and stromal keratocyte cells were distinguishable. Both ex vivo and in vivo images were acquired with a large (1.26 mm x 1.26 mm) field of view. Cellular details in obtained images make this device a promising candidate for realization of high-resolution in vivo cornea imaging.

In inhomogeneous media, light propagation undergoes strong phase distorsion due to aberrations and multiple scattering. A matrix approach for eye imaging is proposed to characterize and get rid of these undesirable effects in optical coherence tomography.

This talk reviews the development of a new pediatric vision screener, which employs polarization-modulated, retinal-birefringence-scanning-based eye alignment detection and bull's eye focus detection with an improved target system.

We present a new full-field optical coherence tomography instrument capable of corneal imaging in air. Acquired images show the potential of this system for realization of in-vivo ultrahigh-resolution human cornea imaging.

By analysis of the accompanying torsional movement of an eye during vertical movement, one can judge the relative contribution of the oblique muscles versus the vertical rectus muscles to that vertical movement. Such analyses have suggested that the oblique extraocular muscles play a predominant role in vertical fusional vergence in healthy individuals.1–4 Vertical fusional vergence induced by prism-produced vertical disparity in healthy subjects, and assessed using manual video-oculography, was associated with a cycloversion of the eyes (torsion of both eyes in the same direction), with the downward-moving eye intorting and the upward-moving eye extorting.1 This movement pattern suggested that the oblique muscles were largely responsible for disparity-induced vertical vergence movements. This movement pattern was largely confirmed in healthy subjects using scleral search coil recordings, with the caveat that part of the cycloversion response was in the form of torsional nystagmus.2 Subsequent studies using an afterimage technique3 and automated video-oculography4 further supported the above findings in healthy subjects and supported the idea that the oblique muscles were the primary mediators of normal vertical fusional vergence.3,4 The fourth cranial nerve, which innervates only the superior oblique muscle, can be damaged from blunt head trauma. This causes a characteristic ocular motility pattern, with elevation and extorsion of the higher eye and a compensatory head tilt away from the higher eye, which we call acquired fourth nerve paresis/palsy or superior oblique paresis/palsy (SOP). A very similar ocular motility pattern of misalignment, however, with no such trauma, can occur in any decade of life and is of uncertain etiology. The historically presumed cause has been an inborn weakness (“paresis”) of the superior oblique muscle not manifest until later in life (therefore historically termed “congenital” SOP). Magnetic resonance imaging studies, however, have shown that many patients with apparent congenital SOP have superior oblique muscles with normal cross-sectional area and normal contractility,5,6 suggesting other causes for “congenital” SOP in many cases.7,8 Because of different mechanisms likely involved in the genesis of the ocular motility pattern known as SOP, one should not be surprised if patients use different vertical vergence mechanisms to compensate for such deviations when small enough to allow motor fusion. The particular mechanism used may also correlate with surgical outcome, and thus may influence the best approach for surgical correction. Indeed, different mechanisms of vertical fusional vergence, not predominately relying on the oblique muscles, were found by Mudgil and colleagues9 in patients with various forms of “SOP.” Using scleral search coil eye movement recordings, they identified three different patterns of vertical fusional vergence during attempted fusion in patients with unilateral SOP. The predominant pattern, involving extorsion of the downward-moving eye and intorsion of the upward-moving eye, suggested a predominant role of the vertical rectus muscles. This was found in all of their patients with true, acquired SOP, but in only one-third of patients with “congenital” SOP.9 The purpose of this study was to investigate cyclovertical eye movement patterns during vertical fusion in patients with “congenital unilateral SOP” using our custom eye-tracking haploscope,4,10,11 and to investigate the value of classifying “congenital SOP” by the type of compensatory fusion used, in hopes of guiding the approach used for surgical correction.

Assessment of stromal light backscattering with full-field optical coherence tomographic microscopy shows promise as objective means to quantify corneal transparency, addressing an unmet yet critical need in anterior segment ophthalmology.

This special issue of Applied Optics contains selected papers reflecting the various disciplines that are needed for the design, implementation and advancement of imaging technology and systems, and it highlights the state-of-the-art research developments in the areas of modern imaging use.

Purpose Commercially available pediatric vision screening devices that test for amblyopia’s primary causes (strabismus and defocus) can detect strabismus only indirectly and inaccurately via assessment of the positions of external light reflections from the cornea, but they cannot detect the anatomical feature of the eyes where fixation actually occurs (the fovea). Methods Our laboratory has been developing technology to detect true foveal fixation, by exploiting the birefringence of the uniquely arranged Henle fibers delineating the fovea, using retinal birefringence scanning (RBS), and we recently described a new, polarization-modulated approach to RBS that enables entirely direct and reliable detection of true foveal fixation, with greatly enhanced signal-to-noise ratio and essentially independent of corneal birefringence. Here we present a new pediatric vision screener (PVS) that employs polarization-modulated RBS for strabismus detection, and double-pass focus detection using a bull’s eye photodetector and improved target system with accommodative control. Results Performance tests in adult volunteers and pediatric patients demonstrate that our new PVS 1) is capable of detecting even small angles of eye misalignment (at least 0.75° or 1.3 PD), 2) has the potential to detect spherical focus within ±1.00 D, and 3) has the potential to detect the misalignment in patients with accommodative esotropia who only develop a crossed eye when focusing intently on a near target. Conclusion In conclusion, the new PVS shows real promise in supplying the demand for a reliable, automated strabismus/defocus screening tool for children at risk for amblyopia.

We present an improved method for remote eye-fixation detection, using a polarization-modulated approach to retinal birefringence scanning (RBS), without the need for individual calibration or separate background measurements and essentially independent of corneal birefringence. Polarization-modulated RBS detects polarization changes generated in modulated polarized light passing through a unique pattern of nerve fibers identifying and defining the retinal region where fixation occurs (the fovea). A proof-of-concept demonstration in human eyes suggests that polarization-modulated RBS has the potential to reliably detect true foveal fixation on a specified point with an accuracy of at least ± 0.75°, and that it can be applied to the general population, including individuals with sub-optimal eyes and young children, where early diagnosis of visual problems can be critical. As could be employed in an eye-controlled display or in other devices, polarization-modulated RBS also enables and paves the way for new and reliable eye-fixation-evoked human-machine interfaces.

Amblyopia (“lazy eye”) is a major public health problem, caused by misalignment of the eyes (strabismus) or defocus. If detected early in childhood, there is an excellent response to therapy, yet most children are detected too late to be treated effectively. Commercially available vision screening devices that test for amblyopia’s primary causes can detect strabismus only indirectly and inaccurately via assessment of the positions of external light reflections from the cornea, but they cannot detect the anatomical feature of the eyes where fixation actually occurs (the fovea). Our laboratory has been developing technology to detect true foveal fixation, by exploiting the birefringence of the uniquely arranged Henle fibers delineating the fovea using retinal birefringence scanning (RBS), and we recently described a polarization-modulated approach to RBS that enables entirely direct and reliable detection of true foveal fixation, with greatly enhanced signal-to-noise ratio and essentially independent of corneal birefringence (a confounding variable with all polarization-sensitive ophthalmic technology). Here, we describe the design and operation of a new pediatric vision screener that employs polarization-modulated, RBS-based strabismus detection and bull’s eye focus detection with an improved target system, and demonstrate the feasibility of this new approach.

Purpose To determine the sensitivity of the Bielschowsky head-tilt test and other commonly used criteria in identifying patients with true bilateral superior oblique paresis. Design A retrospective chart review was performed to identify patients seen between 1978 and 2009 who were diagnosed with acquired bilateral superior oblique paresis. Methods All patients had a confirmed history of head trauma or brain surgery with altered consciousness followed by symptomatic diplopia. Bilateral superior oblique paresis was defined and diagnosed by the above history, including the presence of greater extorsion in downgaze than upgaze on Lancaster red-green testing, a V-pattern strabismus, and bilateral fundus extorsion. We analyzed findings of the Bielschowsky head-tilt test, the Parks 3-step test, and reversal of the hypertropia from straight-ahead gaze to the other 8 diagnostic positions of gaze to determine these tests' sensitivity in identifying true bilateral superior oblique paresis. Results Twenty-five patients were identified with the diagnosis of true bilateral superior oblique paresis. The Bielschowsky head-tilt test had a 40% sensitivity, the Parks 3-step test had a sensitivity of 24%, and reversal of the hypertropia had a sensitivity of 60% in making the diagnosis of true bilateral superior oblique paresis. Conclusions What previously has been described as masked bilateral superior oblique paresis simply may be a reflection of inherent poor sensitivity of the Bielschowsky head-tilt test, the Parks 3-step test, and reversal of the hypertropia in diagnosing bilateral superior oblique paresis. Hence, none of these tests should be relied on exclusively to make this diagnosis.

We developed a novel Pediatric Vision Screener (PVS) that uses wave-plate-enhanced retinal birefringence scanning for strabismus detection, essentially independent of an eye& rsquo;s corneal birefringence, and double-pass focus detection using a bull& rsquo;s eye photodetector.

To determine whether patients historically diagnosed with bilateral superior oblique paresis (BSOP) categorized into (1) immediate-onset and (2) gradual-onset torsional diplopia groups are also distinguishable on the basis of patterns of subjective misalignment in various directions of gaze, consistent with the gradual-onset group being caused by sensory extorsion rather than by BSOP.The medical records of all patients diagnosed with BSOP, V-pattern esotropia, or V-pattern exotropia between 1978 and 2009 were retrospectively reviewed. Those patients with torsional diplopia were classified into immediate- or gradual-onset diplopia groups. The torsional misalignments measured by Lancaster red-green plots were compared, and the surgical outcomes were evaluated.Of 38 patients identified, 27 had immediate-onset and 11 gradual-onset diplopia. There was a statistically significant difference in the increase in extorsion from up- to downgaze between the immediate- versus gradual-onset group (17.8° versus -1.5°, P0.001). Patients in the immediate-onset group fared significantly better with bilateral Harada-Ito procedures than with bilateral inferior oblique-weakening procedures (P = 0.02), whereas patients in the gradual-onset group fared equally well with either procedure (P = 0.72).Extorsion in upgaze is largely absent in patients with immediate-onset BSOP but is present in both up- and downgaze in patients with gradual-onset sensory extorsion. Lancaster red-green testing aids in distinguishing these two groups. The bilateral Harada-Ito procedure is a better procedure for true BSOP, whereas a bilateral inferior oblique-weakening procedure may be preferred for patients with sensory extorsion.

We describe a new removable sliding polyglactin 910 suture noose for postoperative suture adjustment following extraocular muscle surgery. No excess suture material remains after adjustment has been completed, helping to reduce discomfort, inflammation, and scarring. We have used this noose with the cul-de-sac conjunctival incision in approximately 360 patients over a period of 18 months. This report details how to fashion, use, and remove the noose.