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To evaluate the efficacy of using optokinetic nystagmus (OKN) as an objective measurement of vision in severely visually impaired patients, in whom it is difficult to measure visual function reliably. Objective visual acuity (VA) measurements would be useful in the pre-and postoperative assessment of severely visually impaired patients who are pote...
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Context 1
... root mean square error from the equation was 12.5 deg/s. A mean error was calculated for each eye by averaging the difference between the model prediction and the observed V max across all spatial frequencies (Table 1). The average re- sults agree fairly well with the model prediction, with the exception of two patients. ...
Context 2
... analyzed our data individually for each patient in an attempt to identify outliers from the overall trends that we observed for both VA and VF results. Two subjects (patients 4 and 12 in Table 1) had good central VA but extremely re- stricted VFs. Both patients had a low response rate with incon- sistent OKN responses, one of which fit the model well and one of which did not. ...
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... When the eye is exposed to sustained full-field visual motion, a distinct pattern of fast and smooth tracking eye movements and low-acceleration head movements emerge in the direction of visual motion, called optokinetic nystagmus (OKN) 1 , 2 . The neurological pathway of OKN passes from the retina to the lateral geniculate body, occipital lobe, and cerebellar flocculus and connects to the ocular motor neurons 3 . Neural damage anywhere along these neural pathways may lead to changes in the OKN responses. ...
... OKN is a reflexive saw tooth motion of the eyes in response to a drifting stimulus, which is used as a tool to assess visual acuity in human subjects 3 . In animals, including primates and rodents, OKN testing is used as a quantitative measurement of visual function. ...
Optokinetic nystagmus (OKN) is a reflexive eye movement initiated by the motion of visual stimuli in the field of vision. The head-tracking movement associated with OKN is commonly used as a measure of visual function in rodents. To record OKN responses in normal and experimental rats, a simple and inexpensive apparatus has been developed. This setup uses two tablet screens to display the OKN visual stimulus consisting of high contrast black and white stripes generated using the OKN Stripes Visualization Web Application, a freely available software. The rat is placed inside a clear Plexiglass holder that limits movement so that the rat's head continuously faces the OKN display screen. The position of the rat holder can be changed to adjust the distance between the rat and the display screen. A micro-camera positioned above the rat holder is used to record the rat's visual activities. These recordings can be used for quantitative assessments. Based on the presence or absence of clear head-tracking, the OKN responses at different spatial frequencies can be determined. The collected data demonstrates a novel technique for reliable measurement of visual acuity in normal and retinal degenerate rats.
... 1 In addition, the eye movement occurring in response to a moving scenario, optokinetic nystagmus (OKN), has been linked to the appraisal of CS (motion CS). [5][6][7] Canonically, OKN is a saw-tooth displacement of the eye, denoting the two phases of the OKN. The slow phase (OKN-SP) identifies a motion-tracking eye movement occurring in the direction of the visual stimulus drift. ...
... 8 Furthermore, the velocity of the OKN-SP appears to be lower, but nonetheless comparable to the velocity of the moving pattern, because the OKN gain (the ratio of the OKN-SP velocity to the stimulus velocity) was found to be 0.76 ± 0.15 using EOG. 6 In contrast, the quick phase of OKN (OKN-QP) occurs in the direction against the stimulus drift in a saccade-like fashion, moving the eye into the original position. It has been previously believed that the OKN-QPs are similar to normal saccades, because the main sequence parameters have not revealed any statistical difference between saccades and OKN-QPs, although the velocity of an OKN-QP was found to be slightly lower. ...
... With regard to OKN and visual performance appraisal, OKN appeared to be a reliable eye movement in assessment of visual functions in participants suffering from several visual impairments. 6 Although previous research focused on detecting visual acuity from OKN returned results that correlated with subjective measurements in both youth and adults, 12,13 the estimation of visual acuity in children using OKN reflexes did not show sufficient performance. 14 Regarding the testing of contrast sensitivity, Sangi et al. 15 showed an efficient assessment of CS in children, as did Leguire et al. 7 in emmetropic adults. ...
Purpose:
The aim of the current study was to develop and validate an automated contrast sensitivity (CS) test using a live- detection of optokinetic nystagmus (OKN) and an adaptive psychometric procedure. In addition, the study sought to replicate the known effect of defocus on CS for the OKN-based measurements in emmetropic participants.
Methods:
Fifteen participants viewed a horizontally moving grating while their eyes were tracked with an infra-red (IR) eye-tracker. To simulate the clinical conditions of the CS measurements, the participants were stimulated monocularly as the left eye was occluded by an IR filter. The horizontal eye position was continuously analyzed for OKN responses, and the stimulus contrast was changed by an adaptive psychometric method depending on the outcome. Furthermore, the newly proposed OKN live-detection was verified against an offline analysis and an expert-observer judgement. The OKN-based CS was measured for six spatial frequencies at normal vision and three levels of defocus using spherical convex lenses.
Results:
The newly proposed OKN live-detection method showed a sufficient detection performance for implementation of adaptive procedures, and the detection rate is similar or better compared to offline detection methods. Spatial frequency and defocus had a significant effect on the OKN-based CS (P < 0.0001 for both).
Conclusions:
The current study presents a novel method to measure motion CS in an automated way, combining the real-time detection of OKN and an adaptive psychometric procedure. Furthermore, the known effect of defocus on CS was successfully replicated with the newly developed tool.
Translational relevance:
OKN-based CS is a novel approach to assess spatial vision, which is sensitive to subtle effects of defocus, allowing use with nonverbal patients and infants. Furthermore, the newly developed tool may improve the performance of such measurements.
... The between-subject variation of OKN-gain that we observed is substantial but within the range reported by previous studies. 28,40,48,49 The standard deviation (σ ) of the mean for the full field condition was 0.15, which agrees with previous studies. For the 5-deg. ...
Purpose:
Assessment of functional vision across the visual field is hampered by a reliance on patients' subjective judgement of the presence of a stimulus, and the accompanying demands (time and attention) this places on them. As a first step toward determining whether an objective measure of an involuntary eye movement (optokinetic nystagmus [OKN]) could provide an objective measure of field loss, we determined how various measures of OKN depend on the extent of simulated visual field loss (SVFL).
Methods:
We used infrared eye-tracking to measure the eye movements of 16 healthy participants viewing horizontally translating 2-dimensional noise patterns over trials of varying contrasts and different levels of SVFL. We quantified the strength of OKN by estimating the velocity of tracking eye movements compared to the stimulus (OKN gain). These measurements were made using an open-loop SVFL paradigm, where a varying amount of gaze-contingent peripheral stimuli was occluded.
Results:
Full-field stimulation led to an average OKN gain of 0.92 ± 0.15. This value fell steadily with increasing SVFL to a value of 0.38 ± 0.20 when the periphery was not stimulated at all (i.e., the stimulus was a 5-deg. diameter foveal patch). We note considerable individual variation in OKN gain in all conditions.
Conclusions:
Measuring the extent of visual field loss using an objective measure of OKN gain is feasible.
Translational relevance:
Simulated visual field loss reduces optokinetic nystagmus, but further refinement of this technique would be required to overcome individual differences and to pick up clinically relevant field defects.
... As an alternative, in the last decades, a consistent bulk of research focused on procedures based on the optokinetic reflex (OKR) [11][12][13][14][15][16][17]. ...
... In the late 1960s, a number of studies have confirmed the substantial validity of these approaches, showing a correlation between subjective (optotypebased) and objective OKR-based visual acuity [11,[13][14][15][16][17][18][19]]. Yet, even if in its actual form the induction method seems more reliable [13,15,17], the procedure suffers from low predictive power. ...
... Finally, it has been reported that the use of dynamic targets increases the acuity threshold [23,24]: As the intention is to derive Teller acuity for clinical purpose, that is, to say in stationary conditions, slow moving patterns should be adopted. Considering that low velocity is preferable for low visual acuities, whereas higher speed is more indicated to test subjects with relatively better visual function [14], the shift rate is made slower in the first three presentations and faster the fourth stimulation onwards. ...
Purpose
To estimate objective visual acuity in subjects suffering from cataract and age-related macular degeneration via the optokinetic response evoked by a non-conventional induction method (oktotype); in addition, to compare such objective outcome with the subjective acuity based on the ETDRS charts.
Methods
Patients were presented with 13 sequences of symbols arranged horizontally to form a serial pattern, moving from left to right at a constant rate. In each sequence, the size of the stimuli was reduced progressively, while the operator checked for the disappearance of the optokinetic response via a small video camera mounted on the test lens frame. The minimum angular size of the serial pattern able to evoke the optokinetic response (MAER) was referred to as the objective visual acuity of the subject.
Results
Correlation between logMAER and logMAR was significant in the cataract and macular degeneration group (\(R_{\text{cat}}^{2}\) = 0.70, p < .0001; \(R_{\text{AMD}}^{2}\) = 0.63, p < .0007). In the two samples, the correspondence between subjective and objective visual acuity (as, respectively, decimal units and arbitrary decimal units) was satisfactory (concordance correlation coefficient: cataract group = 0.91 and AMD group = 0.93). Test–retest reliability of the oktotype was good for the cataract group and moderate for the AMD sample (Κ 0.81 and 0.59, respectively).
Conclusion
The oktotype seems a promising tool to objectively assess visual acuity in noncooperating subjects with cataract or macular degeneration. Further research on other clinical conditions is needed to clarify the suitability of the procedure in the clinical setting.
... 1. to the property of a structured pattern able to capture the gaze of the subject (preferential looking-based procedure [PL], in particular the Teller acuity test [4][5][6][7][8]); 2. to the amount of the electrical cortical response generated by serial visual stimulations (VEP and sweep VEP [9][10][11][12][13][14][15][16][17][18][19]); 3. to the spatial frequency of a pattern able to evoke the optokinetic reflex [20][21][22][23][24][25][26]. ...
... To confirm the suitability of the lowest contrast value on the OKR, 10 normal subjects (six males, four females, age [14][15][16][17][18][19][20][21][22][23][24][25][26][27] were administered the Oktotype at 20% contrast (Table 3). Data obtained from this sample have been merged to those collected in the preliminary part of the study so that the analysis has been performed on a total of 15 subjects. ...
... Second, the velocity of the stimulation was made lower compared to the value commonly used in other laboratories (i.e., 10°/s: e.g [22,[24][25][26]): As a matter of fact, increasing the speed leads to a decrease of the optokinetic response and makes the subject liable to the stroboscopic effect when ordinary LCD flat panels supporting a 60-Hz refresh rate are employed [25]. On the contrary, consistent optokinetic response takes place below the shifting rate of 17°/s [23], and the lower is this value, the higher is the optokinetic gain (i.e., the ratio between the velocity of the pursuit movement of the response and the velocity of the serial pattern [23]). ...
PurposeTo describe a novel optokinetic visual acuity estimator (Oktotype) and to report the preliminary results obtained in poorly and non-collaborative subjects. Methods
Eleven series of symbols arranged horizontally and moving from left to right at a constant rate were displayed. In each sequence, the size of the stimuli was reduced logarithmically. By using this paradigm, the objective visual acuity was computed in 26 normal subjects as the minimum size of the symbols able to evoke the optokinetic response. In the preliminary phase, three contrast levels were tested, with white noise added to the first five sequences so as to normalize the overestimate found at the lower-half range of the acuity scale. Subsequently, the correspondence between subjective and objective visual acuity was compared in 10 poorly collaborative subjects, and the agreement between optokinetic and Teller visual acuity was measured in six non-collaborative subjects. ResultsThe best agreement is provided by the minimum contrast level (20%) (R2 = 0.74). The correspondence between the two techniques is satisfying both in the normal and in the poorly collaborative sample (concordance correlation coefficient: 0.85 and 0.83, respectively). In the non-collaborative group, the concordance correlation coefficient between Teller acuity and OKVA ranged between 0.79 (test) and 0.85 (retest). Test–retest reliability was very good for the Oktotype (K: 0.82), and better than the Teller test (K = 0.71), even if it was lower compared to Snellen acuity (K = 0.95). Conclusion
The Oktotype seems promising to predict Snellen visual acuity in normal and poorly collaborative subjects.
... It is seen when an individual follows a moving object with their eyes, which then moves out of the field of vision at which point their eye moves back to the position it was in when it first saw the object. It has been shown to help assess visual function in visually impaired patients [3]. The application includes a red desaturation mode and an Amsler grid for additional eye testing. ...
Neuro-ophthalmology is one subspeciality that has always been an enigma for most practising ophthalmologists. The academic prowess of neuro-ophthalmologists is shown by the fact that the first four winners of the prestigious Straatsma American Academy of Ophthalmology teaching awards were all neuro-ophthalmologists [1]. However this academic-oriented branch demands high levels of patience and patient interaction that can often lead to frustration. This chapter aims to highlight some smartphone applications and web resources that can aid examination, help localize lesions and allow the neuro-ophthalmologist to do what they do best: unravel secrets beyond the optic nerve.
... Wester et al., in a 2007 study, described optokinetic nystagmus measurement by electrooculography to predict visual acuity. 12 Their formula took into account a combination of central visual acuity and peripheral vision as measured by Goldmann manual perimetry. The need for an accurate measure of visual field limits its usefulness for predicting visual acuity in suspected non-organic visual loss. ...
Purpose:
The Titmus Stereotest (Stereo Optical Co., Inc., Chicago, IL) has been used to estimate visual acuity (VA) in the evaluation of nonorganic visual loss. Previous predictions were derived from optical degradation of VA in normal subjects and may not account for the variability seen in patients with neuro-ophthalmic pathologies included in the differential diagnosis of nonorganic visual loss. The purpose of this study was to evaluate the relationship between Titmus stereoacuity and minimal VA based on a real-world testing environment.
Design:
Cross-sectional observational study.
Participants:
All patients treated at the authors' neuro-ophthalmology service between April 25, 2014, and July 31, 2014.
Methods:
All subjects underwent routine neuro-ophthalmic examination, including Titmus stereoacuity measurements. A compound Bayesian logit-lognormal model accounting for heteroscedasticity was used to determine 95% and 99% prediction intervals of the worse eye's near VA based on stereoacuity. Logarithm of the minimum angle of resolution VA and log stereoacuity were analyzed.
Main outcome measures:
Titmus stereoacuity and worse eye VA.
Results:
Of 561 patients, 364 subjects 11 to 91 years of age were included. Titmus stereoacuity was associated positively with VA: 9 circles correct (40 seconds of arc) indicated VA of at least 20/40 with 95% confidence and VA of at least 20/79 with 99% confidence; 6 circles correct (80 seconds of arc) indicated VA of at least 20/62 and 20/180, respectively; and 4 circles correct (140 seconds of arc) indicated VA of at least 20/110 and 20/570, respectively.
Conclusions:
When fully accounting for individual variation and the full spectrum of neuro-ophthalmic diseases affecting VA, stereoacuity remains associated with VA, but previous commonly used VA estimates based on stereoacuity overestimated VA. Our results more accurately predict minimum VA from Titmus stereoacuity and should be used preferentially when evaluating patients with suspected nonorganic visual loss. We demonstrated that Titmus stereoacuity cannot definitively establish normal VA, and therefore can suggest, but not fully establish, the diagnosis of nonorganic visual loss.
... Most previous studies of the effect of spatial frequency on OKN have used stimuli at or near the contrast threshold, with the goal of using eye movements as a behavioral response measure in a detection task. In these studies, OKN eyemovement parameters are typically not investigated, other than to verify whether or not they occur under given stimulus conditions (Çetinkaya, Oto, Akman, & Akova, 2008;Leguire, Zaff, Freeman, Rogers, & Bremer, 1991;Wester, Rizzo, Balkwill, & Wall, 2007). Suprathreshold studies are few and conflicting. ...
Optokinetic nystagmus (OKN) is a fundamental oculomotor response to retinal slip generated during natural movement through the environment. The timing and amplitude of the compensatory slow phases (SPs) alternating with saccadic quick phases (QPs) are remarkably variable, producing a characteristic irregular sawtooth waveform. We have previously found three stochastic processes that underlie OKN: the processes that determine QP and SP amplitude and the update dynamics of SP velocity. SP and QP parameters are interrelated and dependent on SP velocity such that changes in stimulus speed can have a seemingly complex effect on the nystagmus waveform. In this study we investigated the effect of stimulus spatial frequency on the stochastic processes of OKN. We found that increasing the spatial frequency of suprathreshold stimuli resulted in a significant increase in SP velocity with a corresponding reduction in retinal slip. However, retinal slip rarely reached values close to 0, indicating that the OKN system does not or cannot always minimize retinal slip. We deduce that OKN gain must be less than unity if extraretinal gain is lower than unity (as empirically observed), and that the difference between retinal and extraretinal gain determines the Markov properties of SP velocity. As retinal gain is reduced with stimuli of lower spatial frequency, the difference between retinal and extraretinal gain increases and the Markov properties of the system can be observed.
... Several studies related visual acuity to optokinetic eye movements [8], or smooth pursuit eye movements [9], and did so by varying the spatial frequency of the stimulus. Optokinetic eye movements refer to the following of a moving pattern of dots or stripes in the full visual field. ...
... The contrast sensitivity function has become a wellestablished tool to probe the functional integrity of the visual system [14]. Over the last decades many techniques, including psychophysics [15] and the recording of optokinetic nystagmus [8,9], have been described to measure the contrast sensitivity function. Leguire et al. [14] compared the contrast sensitivity function based on psychophysics with optokinetic measurements in a small group of healthy subjects and found a good association between the two measures. ...
The present study investigated how gaze following eye movements are affected by stimulus contrast and spatial frequency and by aberrations in central visual acuity due to refractive errors. We measured 30 healthy subjects with a range of visual acuities but without any refractive correction. Visual acuity was tested using a Landolt-C chart. Subjects were divided into three groups with low, intermediate, or good visual acuity. Gaze following responses (GFR) to moving Gabor patches were recorded by video-oculography. In each trial, the subjects were presented with a single Gabor patch with a specific spatial frequency and luminance contrast that moved sinusoidally in the horizontal plane. We observed that GFR gain decreased with increasing spatial frequency and decreasing contrast and was correlated with visual acuity. GFR gain was lower and decreased more for subjects with lower visual acuity; this was especially so for lower stimulus contrasts that are not tested in standard acuity tests. The largest differences between the groups were observed at spatial frequencies around 4 cpd and at contrasts up to 10%. Aberrations in central visual acuity due to refractive errors affect the GFR response depending on the contrast and spatial frequency of the moving stimulus. Measuring this effect may contribute to a better estimate of changes in visual function as a result of aging, disease, or treatments meant to improve vision.
... The magnitude of eye velocity refers to the absolute velocity of slow phases, i.e., the velocity independent of the direction. A weak OKR is often associated with alterations in the retina in both humans and zebrafish Shin et al., 2006;Wester et al., 2007). Thus, the weak OKR observed in some bel larvae could be caused by morphological defects in the bel eye. ...
