O. Bergamin

A New Dynamic Visual Acuity Test to Assess Peripheral Vestibular Function

OBJECTIVE To evaluate a novel test for dynamic visual acuity (DVA) that uses an adaptive algorithm for changing the size of Landolt rings presented during active or passive head impulses, and to compare the results with search-coil head impulse testing. DESIGN Prospective study in healthy individuals and patients with peripheral vestibular deficits. SETTING Tertiary academic center. PARTICIPANTS One hundred neuro-otologically healthy individuals (age range, 19-80 years) and 15 patients with bilateral (n = 5) or unilateral (n = 10) peripheral vestibular loss (age range, 27-72 years). INTERVENTIONS Testing of static visual acuity (SVA), DVA during active and passive horizontal head rotations (optotype presentation at head velocities >100 degrees/s and >150 degrees/s), and quantitative horizontal head impulse testing with scleral search coils. MAIN OUTCOME MEASURE Difference between SVA and DVA, that is, visual acuity loss (VA loss), gain of the high-acceleration vestibulo-ocular reflex. RESULTS Passive head impulses and higher velocities were more effective than active impulses and lower velocities. Using passive head impulses and velocities higher than 150 degrees/s, the DVA test discriminated significantly (P < .001) among patients with bilateral vestibulopathy, those with unilateral vestibulopathy, and normal individuals. The DVA test sensitivity was 100%, specificity was 94%, and accuracy was 95%, with search-coil head impulse testing used as a reference. In healthy individuals, VA loss increased significantly with age (P < .001; R(2) = 0.04). CONCLUSION Dynamic visual acuity testing with Landolt rings that are adaptively changed in size enables detection of peripheral vestibular dysfunction in a fast and simple way.

Cytomegalovirus-associated chorioretinitis after liver transplantation: case report and review of the literature.

Abstract: A cytomegalovirus (CMV) donor positive/recipient negative liver transplant recipient developed CMV syndrome with presumed colitis 2 weeks after discontinuing the standard 3 months of valganciclovir prophylaxis. Treatment with intravenous ganciclovir (GCV) reduced, but did not clear, CMV replication. A CMV UL97 mutation (M460V) conferring GCV resistance was identified. Reduction of immunosuppression was followed by rapidly rising lymphocyte counts as well as by clearance of CMV viremia and of clinical symptoms. However, bilateral chorioretinitis was diagnosed 2 weeks later and treated with foscarnet and cidofovir. Then, right eye vitritis occurred necessitating vitrectomy due to a partially rhegmatogeneous retinal detachment. Because chorioretinitis–vitritis after rising lymphocyte counts and clearance of CMV viremia was strongly suggestive of an immune reconstitution syndrome (IRS)‐like disease, we investigated CMV‐specific T‐cells in the peripheral blood available during follow‐up. We found strong CD8+ but only low CD4+ T‐cell responses (4.77% vs.<0.1%) to the CMV immediate early pp72, while responses to CMV‐lysate or CMV‐pp65 (CD4+ <0.01%; CD8+<0.01%) were low. Over 16 weeks of follow‐up, pp72‐specific CD8+ responses declined, while responses to pp65 gradually increased (CD4+ 0.16%; CD8+ 0.76%) indicating a slowly adapting CMV‐specific cellular T‐cell response. Review of 12,653 published liver transplant patients identified only 14 (0.1%) reported cases of CMV‐associated chorioretinitis at a median 41.7 weeks post transplant. CMV‐associated opthalmologic complications late post transplantation may possibly involve 2 different entities of cytopathic retinitis and IRS‐like chorioretinitis–vitritis.

Extraocular muscle deformation assessed by motion-encoded MRI during eye movement in healthy subjects

Conventional magnetic resonance imaging (MRI) is useful for assessing morphological changes but not for assessing deformations inside homogeneous structures (M. D. Abràmoff, A. P. Van Gils, G. H. Jansen, & M. P. Mourits, 2000). Since no intrinsic contrast can be imaged for distinguishing heterogeneous patterns of muscle contraction, morphological changes along the length of the extraocular muscles (EOMs) are not macroscopically detectable. However, an imaging method that is able to directly encode motion could give evidence about the dynamics of the inhomogeneous deformation of the EOMs. Thus, we developed a method for acquiring motion-encoded MRI images of the EOMs during eye movements. Seven healthy subjects gazed at a horizontal sinusoidally oscillating target. A small surface coil was placed in front of the right orbit. The contracting and relaxing horizontal rectus muscles and the noncontracting optic nerve were reliably tracked. The differential contractility of the EOMs could be distinguished from the third time frame on (=140 ms from the beginning of the right to left eye movement lasting 1 s). The muscle belly of the contracting medial rectus muscle could be distinguished from the posterior and the anterior segment from the sixth time frame on (=350 ms). In conclusion, motion-encoded MRI resolved the heterogeneous contraction of moving EOM segments in healthy subjects without using physical markers.

Vitreous deformation during eye movement

Retinal detachment results in visual loss and requires surgical treatment. The risk of retinal detachment depends, among other factors, on the vitreous rheology, which varies with age. To date, the viscoelasticity of the vitreous body has only been measured in cadaver eyes. However, the ex vivo and in vivo viscoelasticity may differ as a result of the effect of intravitreal membranes. Therefore, an MRI method and appropriate postprocessing tools were developed to determine the vitreous deformation and viscoelastic properties in the eyes of living humans. Nineteen subjects (eight women and 11 men; mean age, 33 years; age range, 14–62 years) gazed at a horizontal sinusoidal moving target during the segmented acquisition of complementary spatial modulation of magnetization images. The center of the lens and the scleral insertion of the optic nerve defined the imaging plane. The vitreous deformation was tracked with a dedicated algorithm and fitted with the commonly used viscoelastic model to determine the model parameters: the modified Womersley number a and the phase angle b. The vitreous deformation was successfully quantified in all 17 volunteers having a monophasic vitreous. The mean and standard deviation of the model parameters were determined to be 5.5 ± 1.3 for a and −2.3 ± 0.2 for b. The correlation coefficient (−0.76) between a and b was significant. At the eye movement frequency used, the mean storage and loss moduli of the vitreous were around 3 ± 1 hPa. For two subjects, the vitreous deformation was clearly polyphasic: some compartments of the vitreous were gel‐like and others were liquefied. The borders of these compartments corresponded to reported intravitreal membrane patterns. Thus, the deformation of the vitreous can now be determined in situ, leaving the structure of the intravitreal membranes intact. Their effect on vitreous dynamics challenges actual vitreous viscoelastic models. The determination of the vitreous deformation will aid in the quantification of local vitreous stresses and their correlation with retinal detachment. Copyright

Local deformation of extraocular muscles during eye movement.

PURPOSE To study extraocular muscle (EOM) function, the local physiologic contraction and elongation (deformation) along human horizontal EOMs were quantified by using motion-encoded magnetic resonance imaging (MRI). METHODS Eleven subjects (healthy right eye) gazed at a target that moved horizontally in a sinusoidal fashion (period, 2 seconds; amplitude, +/-20 degrees), during MRI with an optimized protocol. In addition, EOM longitudinal deformation in two patients with Duanes syndrome type I was analyzed. The horizontal EOMs and the optic nerve were tracked through 15 time frames, and their local deformation was calculated. Eight segments were separated along the EOMs and left-to-right and right-to-left eye movements were compared. RESULTS In healthy subjects, the maximum EOM deformation was situated at approximately two thirds of the muscle lengths from the scleral insertions. The EOM deformations were similar for the entire movement range as well as in both movement directions. In the two patients with Duanes syndrome type I, the abnormal innervation of lateral rectus muscle affected specific EOM segments only. The posterior muscle segments contracted and the anterior muscle segments relaxed during adduction. CONCLUSIONS Motion-encoded MRI is a useful technique for advancing the understanding of the physiology and pathophysiology of EOMs in humans during eye movement.

Longterm follow-up of children with traumatic optic nerve avulsion

Purpose:  We report the longterm follow‐up of children with optic nerve avulsion (ONA) caused by traumatic events. The remarkable differences in courses and outcomes may elucidate the spectrum of ONA‐associated symptoms and injuries.

Comparison of Harms tangent screen and search coil recordings in patients with trochlear nerve palsy

Harms tangent screen, a subjective measurement method of three-dimensional binocular alignment, was compared with search coil recording. Twenty-three patients with unilateral trochlear nerve palsy were measured in nine gaze positions. The two methods correlated best for the horizontal gaze deviation, the vertical gaze deviation, and the vertical incomitance, but there was no correlation for the results of torsional incomitance. Using Harms tangent screen, torsional deviation underestimated the torsional incomitance measured by the search coils. Therefore, central torsional fusional mechanisms or alignment error in the Harms tangent screen are assumed.

Binocular vertical rectus muscle recession for comitant vertical strabismus.

Background: Binocular vertical rectus muscle recession has not been formally evaluated in the correction of comitant vertical strabismus. Methods: Eight patients with stable comitant vertical strabismus for at least 6 months were included. All underwent recession of the superior rectus muscle of the hypertropic eye combined with an equal or nearly equal recession of the inferior rectus muscle in the hypotropic eye. On the day before surgery, on one of the first three postoperative days, and at one year postoperatively, ocular alignment in vertical and horizontal gaze directions were measured with simultaneous and alternate cover test at a viewing distance of 5 meters, and with the two dimensional Hess screen test. The field of single binocular vision was determined with a Goldmann perimeter. The Lang stereopsis chart was presented at the last follow-up visit. Results: All patients were orthotropic at the last postoperative follow-up visit. In primary gaze, the degree of vertical and horizontal phoria diminished significantly. Normal alignment was achieved in nearly all gaze directions and stereopsis was reestablished. The field of single binocular vision enlarged after the surgery. Conclusions: Binocular vertical rectus muscle recession is an effective surgical approach for patients with comitant vertical ocular misalignment.

Residual Torsion Following Ocular Counterroll

Abstract: A recent study on static ocular counterroll suggested the existence of residual torsion (RT): when healthy subjects repositioned their head to the upright position after sustained static tilt, eye position differed from the original ocular torsion measured prior to the static head tilt. Our experiments aimed at further characterizing this phenomenon. Using a three‐dimensional motorized turntable, healthy human subjects (n= 8) were rotated quasi‐statically (0.05 deg/s2, 2 deg/s velocity plateau reached after 40 s) from the upright position about the naso‐occipital axis. Three full whole‐body rotations were completed while subjects fixed upon a blinking laser dot straight ahead in otherwise complete darkness. Three‐dimensional eye movements were recorded with modified dual search coils (wires exiting inferiorly). Torsional position of the right eye at consecutive upright body positions was analyzed. The torsional eye position before the beginning of the chair rotation was defined as zero torsion. On average, the right eye was intorted by 1.3° or extorted by 2.0° after the first full chair rotation in the clockwise or counterclockwise direction, respectively. These torsional offset values of the right eye did not significantly change after the two subsequent full chair rotations. We conclude that RT observed after static ocular counterroll is the result of static hysteresis, that is, a position lag of the eye, which depends on the direction of head roll. The fact that residual torsion did not further increase after the first rotation cycle emphasizes that RT is a static rather than a dynamic phenomenon.