Comparison of Techniques for Correction of Chin-down Vertical Abnormal Head Position Associated with Infantile Nystagmus Syndrome.

PURPOSE: We evaluated the relative effectiveness of combined recession-resection of vertical rectus muscles versus superior rectus recession with inferior oblique weakening for patients who underwent surgical correction of chin-down abnormal head position (AHP) associated with infantile nystagmus syndrome (INS). DESIGN: Retrospective interventional case series. METHODS: This is a review of 22 patients who underwent surgical correction of chin-down vertical AHP associated with INS at an academic institution. The primary outcome was collapse of AHP. Unfavorable outcomes included repeat surgery and induced strabismus, in addition to failure of collapse of AHP. RESULTS: Twenty-two patients had chin-down AHP. Recession-resection (bilateral superior rectus recession 6-9 mm; bilateral inferior rectus resection 5-9 mm) was performed in 11 cases; weakening of both elevators (bilateral superior rectus recession 5-8 mm, bilateral inferior oblique recession or myectomy) occurred in 11 cases. Unfavorable outcome rates were 64% (7/11) compared with 18% (2/11), respectively (P = .03). Reoperation was performed for 6 of 22 patients. Five patients were from the recession-resection group, namely 3 for induced V-pattern esotropia, 1 for alternating esotropia, and 1 to correct recurrent AHP. The last of the 6 who required reoperation was in the elevator weakening group, and required correction of a recurrent AHP (P = .06). CONCLUSIONS: While recession-resection of the vertical recti and weakening of both elevators each produce acceptable collapse of chin-down AHP, the former frequently induces a V-pattern esotropia requiring reoperation.

Management of Strabismus Associated With Infantile Nystagmus Syndrome: A Novel Classification to Assist in Surgical Planning.

PURPOSE: There is no consensus on the surgical management of head position associated with infantile nystagmus syndrome (INS) when strabismus coexists, and few outcome data have been published. We propose classifying strabismus into concordant or discordant based on the relationship between head positioning and strabismus and then modifying surgery accordingly. Our objective is to describe this system and to review surgical outcomes. DESIGN: Retrospective observational case series. METHODS: Twenty-eight patients with INS and coexisting horizontal strabismus underwent surgery for horizontal head positioning and had ≥2 months of follow-up from 1995-2018 at the Vanderbilt Eye Institute. Outcome variables included head positioning (minimal, ≤10°; mild, 11-30°; moderate 31-44°; and severe ≥45°), strabismus (range 0-70 prism diopters [PDs]; minimal ≤10 PD), and reoperation rates. Nonparametric Wilcoxon signed rank, Fisher exact, and Mann-Whitney U tests were used for statistical analysis. RESULTS: Twenty-one cases were concordant and 7 were discordant; the mean follow-up was 4.1 years. Ninety-six percent of patients had moderate to severe head positioning at baseline. Correction rates (to minimal) were 100% at 2-5 months postoperatively and 86% at last follow-up (P < .0001 at both time points compared with preoperatively). The magnitude of strabismus decreased compared with preoperative strabismus (30.8 ± 10.8 PDs; n = 28), strabismus at 2-5 months (9.1 ± 11.9 PDs; P = .0001; n = 26), and last follow-up (12.0 ± 14.1 PDs; P = .0003; n = 28). The overall reoperation rate was 32%. CONCLUSIONS: Our classification system in patients with INS allows a systematic way to surgically improve head positioning and strabismus in cases of moderate to severe baseline head positioning.

Clinical evaluation of graded Anderson's procedure in idiopathic infantile nystagmus.

Aim: To study the efficacy of graded, bilateral, single, horizontal yoked rectus muscle recession for correction of anomalous head posture (AHP) in idiopathic infantile nystagmus (IIN). We hypothesize that the above procedure would sufficiently correct AHP in IIN. Methods: Case records of patients who presented with IIN and AHP due to eccentric null position were included in a retrospective study following IRB approval. Best-corrected visual acuity (binocular Snellen's acuity for distance, in both null position and primary position), anterior segment evaluation using slit lamp biomicroscopy, fundus examination, ocular motility examination and stereopsis (using TNO for adults and older children, Titmus fly test for younger children) were recorded. In all cases recession of the yoke muscles was performed with a gradation of recession, depending on the initial head turn as elaborated in Table 1. AHP was recorded before surgery and 1 and 3 months after surgery. Visual acuity and stereopsis before and after surgery were recorded. Results: Mean AHP improved from 22.5 ± 6.12 degrees of head turn preoperatively to 7.58 ± 3.62 degrees at 1-month postoperative visit (p < .001). The mean binocular visual acuity improved from 0.47 ± 0.15 preoperatively to 0.25 ± 0.17 after surgery (p < .001). Conclusion: Graded yoke muscle recession based on the initial head turn was found to be successful in correcting moderate AHP in patients with IIN. This procedure leaves behind two recti muscles for further surgical intervention in cases with residual AHP.

Longitudinal Studies and Eye-Movement-Based Treatments of Infantile Nystagmus Syndrome: Estimated and Measured Therapeutic Improvements in Three Complex Cases.

INTRODUCTION AND PURPOSE: To demonstrate the utility of using eye-movement data to reveal the diagnostic characteristics of infantile nystagmus syndrome (INS), determine treatment, and both estimate and document therapeutic improvements in three patients with well-developed foveation periods, fairly broad, lateral gaze "nulls," head turns, strabismus, and complex, multiplanar nystagmus. PATIENTS AND METHODS: Infrared reflection, magnetic search coil, and high-speed digital video systems were used to record the eye movements of INS patients, pre- and post-Kestenbaum null-point correction surgery (horizontal or vertical). Data were analyzed and estimations made, using the eXpanded Nystagmus Acuity Function (NAFX) that is part of the OMtools toolbox for MATLAB. RESULTS: In all three subjects (S1-S3), both peak NAFX and longest foveation domain (LFD) improved from their pre-Kestenbaum values. S1: 0.700-0.745 (6.4%) and 25-34° (36%), respectively. S2: 0.445-0.633 (42.4%) and >40° to >50° (10%), respectively. S3: 0.250-0.300 (20%) and 13° to ≫18° (see text), respectively. CONCLUSIONS: S1: Even at the high ends of the pre-therapy NAFX and LFD spectra, INS foveation (and therefore, visual-function) improvements may be adequate to justify nystagmus surgery and provide clinical improvements beneficial to the patient. S2: INS foveation improvements in the vertical plane are equal to those originally estimated using the horizontal data in prior patients. S3: Two apparent NAFX peaks can be converted into a very broad peak by surgery based on the preferred lower peak.

Clinical and ocular motor complications of extraocular muscle extirpation for infantile nystagmus syndrome.

PURPOSE: To describe the effects of extraocular muscle extirpation performed after previous eye muscle surgery in a 20-year-old woman with infantile nystagmus syndrome (INS) for whom we have 19 years of follow-up data. METHODS: Clinical examinations were performed. Eye movement data analysis was carried out using the eXpanded Nystagmus Acuity Function (NAFX) and longest foveation domain (LFD). RESULTS: The patient re-presented to the authors at age 20, 2 years after bilateral anterior myectomy of the horizontal rectus muscles, bilateral anterior nasal transposition of the inferior oblique muscle, and bilateral superior oblique recessions. Evaluation revealed deterioration in nystagmus at lateral gaze angles, new incomitant strabismus with severe loss of convergence, limited ductions, saccadic hypometria, slow saccades, and hypo-accommodation. Also, there was a pre- to post-extirpation minimal change of 21% in her peak NAFX, a 50% decrease in LFD, plus a predominant, asymmetric, multiplanar oscillation. CONCLUSIONS: It appears that in this patient, horizontal extirpation failed to abolish the nystagmus and caused significant, new, symptomatic deficits interfering with many of the patient's visual functions.

[Ultrastructural alteration of extraocular muscle proprioceptor in congenital idiopathic nystagmus].

Objective: To explore the ultrastructural alteration of extraocular muscle proprioceptor in congenital idiopathic nystagmus (CIN). Methods: Case-control study. Ten extraocular muscle samples were collected from five CIN children who underwent nystagmus surgeries in Beijing Children's Hospital from March 2015 to March 2016. Another ten extraocular muscle specimens were collected from five strabismus children in surgery at the same period as normal contrast. There were 3 male patients and 2 female patients of CIN with age of 61-147 months (median age: 91 months). The ultrastructure of extraocular muscle proprioceptors was compared between these two groups by transmission electron microscope. Results: Twenty-three proprioceptors were found in extraocular muscle specimens of CIN children, whereas thirty-three proprioceptors were detected in strabismus children. The ultrastructure of extraocular muscle proprioceptor of CIN altered greatly comparing with that of the control. Fourteen extraocular muscle proprioceptors of CIN were discovered much smaller and vacuolated not only at inner capsules but also at the space between inner and outer capsules with lipofuscins and myeloid bodies in the intrafusal muscle fibers. Sensory nerve fibers degenerated greatly with a lot of lipofuscins and myeloid bodies in these sensory nerve fibers. Demyelination also appeared in some severe cases. Nine extraocular muscle proprioceptors of CIN showed significant dissolving degeneration of myofibrils and proliferation of collagen fibrils. The normal structures could not be distinguished in these proprioceptors. And these structural disorders also appeared in extrafusal muscle fibers and nerve endings. Conclusion: The ultrastructure of extraocular muscle proprioceptor in CIN turned much smaller and had significantly structural disorder.(Chin J Ophthalmol, 2017, 53: 136-139).

Small-incision lenticule extraction in a patient with congenital nystagmus.

We report a case of a 23-year-old woman with congenital nystagmus who had small-incision lenticule extraction (SMILE) procedure to correct refractive errors. The manifest refraction was -5.50 -1.75 × 180 in the right eye, -5.0 -2.50 × 180 in the left eye, and the patient presented with horizontal pendular nystagmus with an amplitude range of 5 to 10 degrees. Uneventful simultaneous bilateral small-incision lenticule extraction was performed. Six months postoperatively, the uncorrected distance visual acuity was 20/18 with -0.25, -0.25 × 80 in the right eye, and 20/20 with +0.25 -0.5 × 50 in the left eye. The case suggests that small-incision lenticule extraction can be an effective alternative for correcting myopic astigmatism in patients with nystagmus.

[Clinical characteristics and surgical treatment of idiopathic congenital nystagmus in 224 patients].

OBJECTIVE: To study clinical characteristics and surgical treatment of idiopathic congenital nystagmus (ICN). METHODS: A retrospective study was conducted in 224 patients with ICN in Tianjin eye hospital from July 2007 to February 2013. RESULTS: There were 224 patients, 158 (70.54%) males and 66 (29.5%) females, mean age was (11.6±8.4) years and (11.4±6.4) years separately. Horizontal nystgamus happened in 215 cases, 3 cases were vertical type and 6 cases were mixed. 214 cases were with no history of operation and 10 patients had ever underwent surgeries before. Furthermore, 151 patients combined with strabismus and refractive error, anterior segment or retinal disorders, which accounting for 67.4% of all the patients. 48 patients were associated myopia, 30 patients with hyperopia, 43 patients with strabismus. Among them, 153 cases of compensatory head position direction were horizontal with face turn, 43 cases (43/153, 28.1%) showed face turning to the left, 110 cases (110/153, 71.9%) showed face turning to the right. Surgeries were designed according to the compensatory head position and head retroversion angle. For 15 patients with double intermediate zones, the position which was often used with good visual function was chosen for operation design. As for the patients with nystagmus and strabismus, the transfer null zone to primary position for the dominant eye and strabismus surgery for the other eye was chosen. And for complicated patients with compensative head position, the dominant head posture were designed for surgery. CONCLUSIONS: ICN is dominated by male with variable clinical manifestations. Surgical choice for ICN depends on the direction of head position and if there is strabismus accompanying it.The aim of ocular muscle surgery is to transfer null zone to primary position. (Chin J Ophthalmol, 2016, 52: 574-578).

Effects of augmented tenotomy and reattachment in the infantile nystagmus syndrome.

PURPOSE: To test the hypothesis that augmented tenotomy and reattachment surgery (AT-R), which involves placing an additional suture in each distal tendon during the 4-muscle tenotomy and reattachment (T-R) or other infantile nystagmus syndrome (INS) procedures, could increase the beneficial effects of many types of extraocular muscle (EOM) surgery to treat INS. METHODS: Both infrared reflection and high-speed digital video systems were used to record the eye movements in 4 patients with INS before and after AT-R surgery. Data were analyzed using the eXpanded Nystagmus Acuity Function (NAFX) that is part of the OMtools software. RESULTS: Placement of the augmentation suture did not interfere with Kestenbaum, Anderson, bilateral medial rectus muscle recession, or T-R surgeries. The therapeutic effects of AT-R were similar to but not equal to those from the traditional single-suture surgeries (ie, broadening longest foveation domain [LFD] but no improvement of NAFX peak). The average of the NAFX percent improvements after AT-R was within 31% of those estimated from NAFX values before T-R; the average of the percent broadenings of the LFD values after AT-R was within 16%. CONCLUSIONS: The AT-R does not improve the foveation quality in INS above the traditional T-R surgery. It is not improved by an additional suture; indeed, some improvements may be diminished by the added suture. The hypothesized augmented-tendon suture technique (sans tenotomy) has been modified and remains to be tested.

A prospective evaluation of retroequatorial recession of horizontal rectus muscles and Hertle-Dell'Osso tenotomy procedure in patients with infantile nystagmus with no definite null position.

PURPOSE: To compare results of retroequatorial recession of horizontal rectus muscles and Hertle-Dell'Osso tenotomy procedure in patients with infantile nystagmus with null in primary position. METHODS: In this prospective study, 10 subjects ≥5 years of age with infantile nystagmus with null in primary position were randomly assigned to two groups: group 1 underwent a large retroequatorial recession of the four horizontal rectus muscles; group 2, simple tenotomy and resuturing (Hertle-Dell'Osso procedure) of the four muscles. Patients were evaluated using Snellen and logMAR visual acuity charts, contrast sensitivity testing, color vision testing, stereopsis testing (TNO), and electronystagmography (ENG) for nystagmus waveforms, frequency, amplitude, and intensity. RESULTS: Group 1 patients showed a trend toward 1-line improvement in their visual acuity for distance on the logMAR and ETDRS charts (P = 0.32); there was no improvement in group 2 patients. Contrast sensitivity improved significantly in both groups (P = 0.03), as did stereopsis (P = 0.02 [group 1], P = 0.04 [group 2]). The amplitude and intensity of nystagmus showed a tendancy to decrease in both the groups in all gazes, although the frequency showed no change in either group. Intergroup variability on all the parameters was not statistically significant. CONCLUSIONS: Both retroequatorial recession of horizontal recti and the Hertle-Dell'Osso procedure showed a trend toward reducing ENG amplitude and improved contrast sensitivity and stereopsis in infantile nystagmus with null in primary position.

Clinical Evaluation of Four-Muscle Tenotomy Surgery for Nystagmus.

PURPOSE: To document prospectively the effect of four-muscle tenotomy surgery on visual acuity (VA) and nystagmus intensity and assess, by the use of a questionnaire, the experience of adult patients and the parents of children who have had the four-muscle tenotomy procedure for nystagmus in the absence of strabismus or an anomalous head position. The qualitative perceived benefits or lack thereof from the procedure were compared to the subjective effects on nystagmus intensity and VA. METHODS: Fifteen patients diagnosed as having congenital/infantile or acquired nystagmus, including albinism or other visual sensory disorders without anomalous head positions or coexisting strabismus, were included in this study. The changes in preoperative and postoperative VA and nystagmus were evaluated based on clinical and perceptual measurements and video recordings. RESULTS: All 15 patients had preoperative and postoperative ophthalmological examinations. One patient had a postoperative conjunctival cyst, which was successfully removed. Fourteen patients (93%) showed clinical VA improvement in at least one eye. Fourteen patients were video recorded preoperatively and postoperatively to analyze their nystagmus intensity; case 9 was not included. Postoperatively, 10 patients (71%) showed a decrease in nystagmus intensity. Thirteen patients (87%) perceived vision improvement and 11 patients (73%) perceived a decrease in nystagmus intensity. All patients experienced either clinically improved VA or a decrease in nystagmus intensity. Fourteen patients (93%) perceived either improved VA or a decrease in nystagmus intensity. The preoperative and postoperative changes in VA (P = .002) and nystagmus intensity (P = .043) were both statistically significant. CONCLUSIONS: The authors have shown that four-muscle tenotomy surgery for nystagmus can improve VA and decrease nystagmus intensity. The study yielded subjective patient satisfaction, modest objective improvement in VA, and no significant complications.

[Quantitative assess the efficacy of congenital idiopathic nystagmus surgery by digital eye tracker].

OBJECTIVE: To evaluate the feasibility of independently developed digital eye tracker in determining the efficacy of congenital idiopathic nystagmus (CIN) surgery. METHODS: Aprospective selfpairing study. The surgical efficacy was evaluated by independently developed eye tracker in 16 CIN patients. The null zone and the frequency, amplitude, intensity of nystagmus in various gazing position were recorded with eye tracker pre and post operatively. The consistency of null zone determined by digital eye tracker and clinical investigation were evaluated. The preoperative and postoperative rectification of horizontal and vertical nystagmus in the horizontal direction of individual patient were compared by paired samples t-test. The improvement or aggravation quantity were recorded by comparing preoperative and postoperative intensity of nystagmus every 5° within 25°. RESULT: The null zone got from digital eye tracker and clinical investigation were highly consistent (r = 0.952, P < 0.01). The horizontal and vertical intensity improved in 9 patients (t = 2.335-6.609, P < 0.05) and 5 patients (t = 2.176-5.471, P < 0.05) respectively after surgery. There were 67.63% (117/173) horizontal intensity and 69.94% (121/173) vertical intensity improvement. CONCLUSION: The independently developed digital eye tracker can quantitatively evaluate the pre and post-operative nystagmus and analyze the surgical efficacy for CIN patients.

Photorefractive keratectomy in 22 adult eyes with infantile nystagmus syndrome.

PURPOSE: To analyze visual and refractive outcomes of photorefractive keratectomy (PRK) in adult patients with infantile nystagmus syndrome. SETTING: Ophthalmology Unit, Department of Experimental Diagnostic and Specialty Medicine, Saint Orsola-Malpighi Hospital, University of Bologna, Bologna, Italy. DESIGN: Retrospective case series. METHODS: Photorefractive keratectomy was performed in both eyes of patients with infantile nystagmus syndrome under topical anesthesia using an eye-tracking excimer laser. Patient satisfaction was tested using a questionnaire. The main outcomes were a decrease in refractive error, an improvement in postoperative corrected distance visual acuity (CDVA), and an uncorrected distance visual acuity (UDVA) equal to or better than the preoperative UDVA. RESULTS: Twenty-two eyes of 11 patients with infantile nystagmus syndrome were evaluated. The mean patient age was 30.82 years (range 22 to 42 years). All eyes had simple, compound, or mixed astigmatism (mean -3.40 D; range -0.75 to -6.00 diopters [D]). The mean postoperative astigmatism (-0.70 D ± 0.81 [SD]) and spherical equivalent (-0.420 ± 0.652 D) were statistically significantly better than the preoperative values (-3.40 ± 1.31 D and -3.426 ± 3.343 D, respectively (P < .0001 and P = .0002, respectively). The mean monocular postoperative CDVA (0.24 ± 0.19 logMAR) and UDVA (0.25 ± 0.18 logMAR) were better than the mean preoperative CDVA (0.32 ± 0.28 logMAR) (P = .0045 and P = .0338, respectively). The mean binocular postoperative UDVA was better than the mean preoperative CDVA (0.15 ± 0.14 logMAR versus 0.23 ± 0.23 logMAR) (P = .05). No patient required repeat surgery. CONCLUSIONS: Nystagmus patients are eligible for PRK. The results were promising; gaining a few Snellen lines in visual acuity can be very important to these patients for their daily life. FINANCIAL DISCLOSURE: No author has a financial or proprietary interest in any material or method mentioned.

ANOMALOUS HEAD POSTURES IN STRABISMUS AND NYSTAGMUS DIAGNOSIS AND MANAGEMENT.

UNLABELLED: Abnormal head positions are adopted in order to improve visual acuity, to avoid diplopia or to obtain a more comfortable binocular vision. The head can be turned or tilted toward right or left, with the chin rotated up or downwards or combination of these positions. The ophthalmologic examination including the assessment of versions leads to the diagnosis. When versions are free, the cause may be congenital nystagmus or strabismus with large angle. When versions are limited we suspect paralytic or restrictive strabismus. The head tilted to one shoulder suggests cyclotropia (IV Nerve Palsy) or congenital nystagmus. We present few of the above cases. An adequate surgical treatment can improve or correct the ocular deviation, diplopia and the abnormal head posture. CONCLUSIONS: The abnormal head posture must be assessed and treated early in order to correct the ocular position and head posture. All patient presenting abnormal head position HAD TO BE investigated by an ophthalmologist.

[Efficacy of surgery on congenital nystagmus with convergence damping].

OBJECTIVE: To evaluate the efficacy of surgery in the treatment of congenital nystagmus with convergence damping. METHODS: Retrospective and comparative case series. Eight patients diagnosed as congenital nystagmus with convergence damping at Beijing Children's Hospital between September 2010 and September 2012 were enrolled in this study. The ages were 9.5 (12, 6) years old, and follow-up was 9 (24, 6) months. All patients received prism induced convergence and the same surgery of bimedial rectus recession and bilateral rectus tenotomy. The best corrected visual acuity, the range of fusion and the nystagmus waveforms were analyzed before and after surgery. RESULTS: The range of fusion was -3.75±1.83° to +19.38±3.16° before surgery and -3.88±1.55° to +19.00±3.02° after surgery; there was no significant difference (t=0.24, P=0.82). The binocular visual acuity increased from 0.21±0.15 without convergence to 0.28±0.18 using convergence; there was significant difference (t=-4.43, P=0.00). The visual acuity was 0.32±0.20 after surgery, significantly different from that before surgery without convergence (t=-5.29, P=0.00), but not significantly different from that before surgery using convergence (t=-2.12, P=0.07). Patients had significant improvements in the frequency (t=3.28, 3.02, P<0.05) and intensity of the nystagmus waveforms when using convergence and postoperatively (t=3.27, 3.48; P<0.05), but there was no significant improvement in the amplitude of the waveforms (t=1.31, 1.57, 0.31, P>0.05). CONCLUSIONS: Surgery for congenital nystagmus with convergence damping can provide expectations for ocular motor and visual results. The range of fusion should be wide enough, and the effect of convergence on the frequency is greater than that on the amplitude.

What we know about the generation of nystagmus and other ocular oscillations: are we closer to identifying therapeutic targets?

Mechanisms underlying acquired nystagmus are better understood than those leading to infantile nystagmus. Accordingly, further progress has been made in the development of effective therapies for acquired nystagmus, mainly through pharmacological interventions. Some of these therapies have been developed under the guidance of findings from experimental animal models. Although mechanisms behind infantile nystagmus are less understood, progress has been made in determining the genetic basis of nystagmus and characterizing associated sensory deficits. Pharmacological, surgical, and other treatments options for infantile nystagmus are now emerging. Further investigations are required for all forms of nystagmus to produce high-quality evidence, such as randomized controlled trials, upon which clinicians can make appropriate treatment decisions.

Secondary or new compensatory head posture after Anderson-Kestenbaum surgery.

PURPOSE: To report clinical findings and surgical management of 4 patients with congenital nystagmus who presented with a new or reversal of their original horizontal compensatory head posture (CHP) after Anderson-Kestenbaum (A-K) surgery. METHOD: Retrospective chart review. RESULTS: All 4 patients demonstrated a 40°-45° horizontal face turn at the time of their initial surgery and 3 underwent 20% and one 30% augmented A-K surgery to correct the CHP. The new CHP or reversal of the original CHP was observed at a mean of 4 years (range 1-9 years) after the initial surgery. The reversed CHPs measured 20°, 40°, 20°, and 20°, respectively. These new or residual CHPs were surgically managed in 3 patients and an acceptable head position was achieved in all patients. CONCLUSIONS: This series of patients points out the occurrence of secondary null points and reversed CHP after surgical correction of initial CHP.

Smooth-pursuit changes after the tenotomy and reattachment procedure for infantile nystagmus syndrome: model predictions and patient data.

PURPOSE: Patients with infantile nystagmus syndrome (INS) often cannot quickly locate new visual targets or track moving objects. Dynamic demands on visual function are not measured by static measures (eg, visual acuity); they require time-sensitive measures. The authors investigated how dynamic properties of INS (pursuit-target acquisition times) were affected by the tenotomy and reattachment (T&R) procedure in both patients with INS and behavioral ocular motor system model predictions. METHODS: Responses of 3 patients with different INS waveforms were compared before and after T&R to test the model's predictions. A high-speed digital video system was used to take eye-movement data. Human responses to target-ramp stimuli were analyzed. RESULTS: T&R did not improve the smooth-pursuit responses of patients with INS; pursuit-target acquisition times did not show marked improvements. However, in one case, T&R allowed the patient to pursue targets "faster" in a specific direction. CONCLUSION: T&R can improve peak visual acuity, broaden the high-acuity gaze-angle range, and reduce target acquisition times to static targets but not moving targets. When the target moves simultaneously with an ongoing saccade in the nystagmus cycle, the steady-state errors and elongated target acquisition times observed might be part of the intrinsic characteristics of normal pursuit responses.