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Infantile nystagmus syndrome (INS) consists of involuntary oscillation of the eyes, that usually develop within the first months of life. INS can be idiopathic or associated with albinism, retinal ...

Purpose. - To evaluate long terms outcomes of botulinum toxin in infantile esotropia by measuring the amount of microtropia 24 months after injection. Secondary purpose was to identify predictive factors of microtropia. Methods. - A retrospective, single-center study was performed at the university medical centerin Bordeaux between 2001 and 2018, including all patients with infantile esotropia greater than 20 D. All patients received 5 or 7,5 IU of botulinum toxin A in each medial rectus, once or twice depending on the angle of deviation after the first injection and after wearing full optical correction at least two months. We noted the angle at 1, 6, 12 and 24 months, the occurrence of any complications and the need for later strabismus surgery. The primary endpoint was the achievement of a microtropia less than 8 diopters (D) at 24 months post-injection. We evaluated the predictive factors for microtropia with a Fischer's test. Results. - We included 30 patients with esotropia greater than 20 D. The mean follow-up after injection was 48 months +/- 30. The mean age was 16.24 months (7-29 months) with a female predominance in the population (SR = 0.43). The mean pre-injection deviation was 41.25 +/- 12.17 D. The majority of patients were mildly (40%) or moderately (40%) hyperopic. At 24 months, 46.7% microtropias were obtained (95% CI: 28.9%-64.5%). The change in mean angle at 1, 6,12 and 24 months post-injection was -8.57 +/- 25.21 D; 14.48 +/- 13.40 D; 18.38 +/- 12.07 D and 21.23 +/- 14.97 D, respectively. No factors were predictive of microtropia. Of the 30 children, 3 had transient ptosis requiring strips and 12 showed an exotropia at 1 month. All complications were self-limited and without consequences. 3 children had a second injection of botulinum toxin, which in 2/3 of the cases resulted in a long-lasting microtropia. 26.7% (n = 8) of the children underwent secondary surgery. Obtaining a microtropia 24 months after injection statistically significantly reduced the need for secondary strabismus surgery: 92.9% P = 0.039% CI 95% (0.002; 1.0606). Conclusion. - Botulinum toxin appears to be a less invasive and more conservative alternative to surgery in children with infantile esotropia. In 46.7% of cases, microtropia is achieved. An improvement was noted in 90% (n = 27) of the children with a reduction of half (21.23 D) of the mean post-injection angle at 24 months. When effective, it significantly reduces the need for secondary surgery. (c) 2021 Elsevier Masson SAS. All rights reserved.; Objectif: Évaluer l’efficacité à long terme de la toxine botulique dans le traitement de l’ésotropie précoce grâce au pourcentage de microtropie à 24 mois post-injection. L’objectif secondaire était de rechercher les facteurs prédictifs à l’obtention de cette microtropie. Méthodes: Nous avons réalisé une étude rétrospective, monocentrique au Centre Hospitalier universitaire (CHU) de Bordeaux entre 2001 et 2018 en incluant tous les patients ayant une ésotropie précoce. Ces patients ont reçu une injection bilatérale de 5 ou 7,5 unités de toxine botulique à une ou deux reprises en fonction de l’angle après la première injection et port de la correction optique totale. L’ensemble des caractéristiques sociodémographiques et ophtalmologiques ont été recueillis en préopératoire. Nous avons noté l’angle à 1,6,12 et 24 mois ; l’apparition de complications ainsi que la nécessité d’une chirurgie de strabisme à distance. Le critère de jugement principal était l’obtention d’une microtropie inférieure à 8 dioptries (D) à 24 mois post-injection. Nous avons évalué les facteurs prédictifs de la microtropie par un test de Fischer. Résultats: Nous avons inclus 30 patients ayant une ésotropie supérieure à 20 D avec un délai moyen de suivi post-injection de 48 mois ± 30. L’âge moyen était de 16,24 mois (7–29 mois) avec une prédominance féminine dans la population (sex ratio SR = 0,43). L’angle moyen pré-injection était de 41,25 ± 12,17 D. Il y avait une majorité d’hypermétropes légers (40 %) et modérés (40 %). À 24 mois, on obtenait 46,7 % de microtropies (intervalle de confiance : IC 95 % : 28,9 %–64,5 %). L’évolution de l’angle moyen à 1,6,12 et 24 mois post-injection était respectivement de −8,57 ± 25,21 D ; 14,48 ± 13,40 D ; 18,38 ± 12,07 D et 21,23 ± 14,97 D. Aucun facteur n’était prédictif de l’obtention d’une microtropie. Parmi les 30 enfants, 3 ont eu des ptôsis transitoires nécessitant la pose de strips et 12 ont présenté une exotropie à 1 mois. Toutes les complications étaient spontanément résolutives et sans conséquences. 3 enfants ont eu une seconde injection de toxine botulique permettant dans 2/3 des cas l’obtention d’une microtropie durable. 26,7 % (n = 8) des enfants ont été opérés secondairement ; l’obtention d’une microtropie à 24 mois diminuait de façon statistiquement significative les chirurgies secondaires du strabisme : p = 0,039 % IC 95 % (0,002 ; 1,0606). Conclusion: La toxine botulique semble être une alternative moins invasive et plus conservatrice que la chirurgie chez les enfants présentant une ésotropie précoce. Elle permet l’obtention d’une microtropie dans 46,7 % des cas. On notait une amélioration chez 90 % (n = 27) des enfants avec une réduction de la moitié (21,23 D) de l’angle moyen post-injection à 24 mois. Lorsqu’elle est efficace elle réduit significativement les chirurgies secondaires.

Apart from the latent nystagmus, which arises as a consequence of failure to develop binocular vision, every case of childhood nystagmus needs an etiological assessment. Knowledge of the pathogenesis of the various types of nystagmus guides this assessment, particularly considering the morphological characteristics of the nystagmus. The clinical ophthalmologic examination is complemented by OCT and electrophysiologic testing (ERG, VEP). If this testing is normal, an MRI and genetic assessment are required.

The fast phases of latent/manifest latent nystagmus (LMLN) may either cause the target image to fall within (foveating) or outside (defoveating) the foveal area. We previously verified that both types are generated by the same mechanism as voluntary saccades and propose a hypothetical, dual-mode mechanism (computer model) for LMLN that utilizes normal ocular-motor control functions. Fixation data recorded during the past 30 years from 97 subjects with LMLN using both infrared and magnetic search coil oculography were used as a basis for our simulations. The MATLAB/Simulink software was used to construct a robust, modular, ocular motor system model, capable of simulating LMLN. Fast-phase amplitude versus both peak velocity and duration of simulated saccades were equivalent to those of saccades in normal subjects. Based on our LMLN studies, we constructed a hypothetical model in which the slow-phase velocity acted to trigger the change between foveating and defoveating LMLN fast phases. Foveating fast phases were generated during lower slow-phase velocities whereas defoveating fast phases occurred during higher slow-phase velocities. The bidirectional model simulated Alexander's law behavior under all viewing and fixation conditions. Our ocular-motor model accurately simulates LMLN patient ocular motility data and provides a hypothetical explanation for the conditions that result in both foveating and defoveating fast phases. As is the case for normal physiological saccades, the position error determined the saccadic amplitudes for foveating fast phases. However, the final slow-phase velocity determined the amplitudes of defoveating fast phases. In addition, we suggest that individuals with LMLN use their fixation subsystem to further decrease the slow-phase velocity as the target image approaches the foveal center.

Dynamic overshoots are seen after voluntary re-fixation saccades. They are microsaccadic movements which follow primary saccades and have no delay. The purpose of this study was to examine the prevalence and metrics of the dynamic overshoots seen after involuntary saccades. Using infra-red oculography we demonstrate that dynamic overshoots are a common occurrence in physiological square-wave jerks, congenital nystagmus and manifest latent nystagmus and that these overshoots are saccadic in nature and have the same dynamic characteristics as those seen following voluntary saccades. It is therefore likely that they share common neural commands to those dynamic overshoots seen after a volitional saccade. All dynamic overshoots are postulated to be the unwanted consequence of making a saccade and are simulated in a model of fast oculomotor behaviour which is consistent with known experimental results.

Current concepts of idiopathic infantile nystagmus are summarized, with special attention to treatment and differential diagnosis of this condition. Advantages of the Anderson procedure over the Kestenbaum procedure are suggested for head turn associated with this condition, and the need for further studies is acknowledged. The importance of the extended slow phase in understanding the waveforms of infantile nystagmus is stressed. Our studies reinforce what I believe to be the natural history of infantile nystagmus, as well as the history of periodic alternating nystagmus. The critical delineation of diagnosing periodic alternating nystagmus is emphasized with respect to the type of operation to avoid overcorrection of head turns in patients with nystagmus. Continued searches for manifest latent nystagmus are important, because that condition is currently the only truly treatable nystagmus. I thank the American Association for Pediatric Ophthalmology and Strabismus for the privilege and honor of presenting the 1997 Costenbader Lecture.

A 24-year-old man, left eye enucleated at the age of ten months, had jerk-right nystagmus with increasing amplitude in abduction and null position in near-extreme adduction. Under occlusion or in darkness, the nystagmus changed to jerk-left, the amplitude increased in adduction and null position was in abduction; as if his left eye had nystagmus blockage syndrome and he was seeing with this absent left eye! The difference between nystagmus blockage syndrome and latent nystagmus is discussed: nystagmus blockage syndrome is manifested by 'motor' maneuver of adduction and abduction, whereas latent nystagmus is induced with 'sensory' maneuver of occlusion. It suggests that nystagmus blockage syndrome and latent nystagmus may arise from different mechanisms despite their frequent concurrence.

The results of squint surgery in 40 children with congenital esotropia are analysed. A 'favourable outcome' was achieved in 23 (57.5%) children. The factors affecting the final outcome including ocular alignment in the immediate postoperative period, age at the time of surgery, amblyopia, associated inferior oblique overaction, dissociated vertical deviation, latent or manifest latent nystagmus, and the surgical procedures used are discussed.

Latent nystagmus (LN) and manifest latent nystagmus (MLN) are closely associated with early visual deprivation and strabismus. In both cases, the eyes oscillate horizontally in an involuntary manner and the fast phases always beat towards the attending or fixing eye. By simultaneously recording eye movements during the dichoptic viewing of dissimilar visual stimuli we present evidence that MLN offers a unique opportunity to examine the nature of sensori-motor switching. In particular, we show how the nystagmus beat direction is strongly influenced by endogenous and exogenous attention. A model describing the possible mechanisms underpinning the sensori-motor switching is proposed.

The incidence and characteristics of nystagmus in Down's syndrome are unclear. In 188 consecutive patients, 56 had nystagmus. Most had no clinically recognizable ocular pathology to account for the nystagmus. Twenty-nine had fine rapid horizontal nystagmus, 14 had a dissociated nystagmus which appeared pendular, whereas 9 had a form of latent or manifest latent nystagmus. Of the total patients with nystagmus, 41 had esotropia. Our findings suggest that fine rapid horizontal nystagmus, sometimes dissociated, occurs frequently in patients with Down's syndrome.

The fast phases of LMLN may either cause the target image to fall within (foveating) or outside (defoveating) the foveal area. We verified that both types are generated by the same mechanism as voluntary saccades and propose a hypothetical, dual-mode mechanism (computer model) for LMLN that utilizes normal ocular motor control functions. Fixation data were recorded from subjects with LMLN using both infrared and mag­ netic search coil oculography and used as templates for our simulations. Fast-phase amplitude vs. both peak velocity and duration of simulated saccades were equivalent to those of saccades in normal subjects. Based on our LMLN data, we constructed a hypothetical model in which the slow-phase velocity acted to trigger the change between foveating and defoveating LMLN fast phases. Foveating fast phases were generated during lower slow-phase velocities whereas, defoveating fast phases occurred during higher slow-phase velocities. The bidirectional model simulated Alexander's law behavior under all viewing and fixation conditions. Our ocular-motor model accurately simulates LMLN-patient ocular motility data and provides a hypothetical explanation for the conditions that re­ sult in both foveating and defoveating fast phases. As is the case for normal physiological saccades, position error determined saccadic am­ plitudes for foveating fast phases. However, final slow-phase velocity determined amplitudes of defoveating fast phases. In addition, we sug

Although electronystagmography is most useful, especially in furthering our knowledge of nystagmus, simple clinical study is the first step to any understanding of nystagmus. Ophthalmologists should be aware that they may understand a good deal about nystagmus merely by studying visual acuity in their surgery. Testing visual acuity at distance with both eyes open will lead to the qualitative and quantitative diagnosis of compensatory abnormal head postures. Testing at distance with 1 eye covered will help to distinguish between the concordant head turn, one eye fixing in abduction and the other fixing in adduction (ABD + ADD) as manifest congenital nystagmus, and the discordant head turn in which each eye fixes in adduction (ADD + ADD), as is seen in manifest latent nystagmus, for which surgery is totally different. Pseudolatent nystagmus found in congenital nystagmus with exophoria can be differentiated from latent nystagmus. This illustrates de visu (with the naked eye) the "beauty" of the movement of blocking fusional convergence and the nature of the involved mechanisms with artificial divergence surgery. Testing at near will bring out the existence of blocking convergence. Depending on the results, the clinical rationale for surgery is thus made clear: horizontal, vertical, rotatory Kestenbaum-like surgery should be used in cases of abnormal head posture, whereas artificial divergence surgery is our most satisfactory armamentarium in cases of blocking convergence. (J AAPOS 2000;4:67–74)

Background: We investigated the role convergence plays in nystagmus dampening, in particular, relationships among visual acuity demands, convergence, and nystagmus. Previously we showed that subjects with idiopathic infantile nystagmus exhibit a range of responses to acuity targets, one of which is nystagmus blockage syndrome. We report herein eye movement responses to acuity targets of patients with manifest/latent nystagmus. Methods: Fourteen patients, 11 with latent or manifest latent nystagmus and 3 with combined manifest latent with infantile nystagmus, were asked to indicate the direction of the gap in Landolt C optotypes while their eye movements were recorded. Results: The tested patients exhibited various responses to acuity demands: (1) dampening of nystagmus with convergence (i.e., nystagmus blockage syndrome) (514 patients), (2) changes in vergence without nystagmus dampening (2 patients), (3) decrease of nystagmus without convergence (2 patients), and (4) little change in nystagmus or vergence (5 patients). In nystagmus blockage syndrome the amount of convergence increased with acuity demands in two of five patients and the convergence duration in four of five patients; nystagmus dampening increased with acuity demands in one of five patients and the blockage duration in four of five patients. Conclusions: Many, but not all, patients with manifest/latent nystagmus, similar to those with infantile nystagmus, used convergence to dampen their nystagmus. The convergence response tended to increase with acuity demands, but the amount of dampening was idiosyncratic and not predictably related to the measured convergence across patients.

Only one form of nystagmus, manifest latent nystagmus (MLN), seems at this time to afford us an opportunity to treat the cause of the nystagmus--namely the lack of binocularity. The binocularity impediments needing treatment may include refractive errors, strabismus, and amblyopia. We should be able to diagnose MLN by wave form analysis, treat the obstacle(s) of fusion, and eliminate or reduce the nystagmus. The purpose of this paper is to review the data and eye movement recordings of MLN patients and look at those in which we have seen improvement (or worsening) of the nystagmus with treatment, particularly in regard to their visual disability, their potential for treatment, and their associated findings.

visual functions were examined in 26 un selected adults with DS and compared with those in an age-matched group of 35 subjects with other causes of mental retardation. The eye movements of those with clinically evident nystagmus were recorded with the infrared technique. We also recorded the eye movements of a child with DS and nystagmus. Results: Nystagmus was identified in six (23%) adults with DS and in none in the control group. All six patients showed latent/manifest latent nystagmus (LMLN), prominent with the covering of one eye, and esodeviations of 10 to 30 prism diopters. Eye movement recordings confirmed LMLN with its exponentially decaying waveform. Frequencies ranged from 2 to 5 Hz and amplitudes from 5° to 20°. While attempting to fixate straight ahead in the absence of visual cues, three subjects exhibited shifts in the mean eye position. In contrast with the findings in adults, the only child with DS examined had both congenital nystagmus and LMLN wave­ forms. Conclusions: The predominant type of nystagmus in the study subjects with DS is LMLN. The high prevalence of LMLN may reflect abnormal integration of visuospatial infor­ mation that is typical of DS. The concurrent presence of con­ genital nystagmus in a child but only LMLN in the adults with DS raises the possibility of age-related waveform changes or

Manifest latent nystagmus (MLN) was identified in 31 patients by accurate eye movement records. All the patients had horizontal tropias, and the nystagmus fast phases were always in the direction of viewing eye. The slow phases of MLN are decreasing-velocity exponentials while those of the jerk form of congenital nystagmus (CN) are increasing velocity exponentials. Several subjects who were believed to have latent nystagmus (LN) on clinical examination had small amplitude nystagmus evident by eye movement recording with both eyes open: these were actually cases of MLN. Many patients with MLN are misdiagnosed as having CN. An explanation for MLN and LN is provided based on confusion of egocentric directions between monocular and binocular viewing conditions.

We wished to study how the severity and duration of early onset visual deprivation affects eye alignment and ocular stability. Thirty-three patients (aged 1 week to 12.8 years) with infantile cataracts (16 bilateral, 17 unilateral) were examined for periods up to 61 months. Twenty-three patients were considered to have cataracts, which were a major obstacle to vision (major form deprivation), 9 of whom underwent surgery within 8 weeks of birth (mean and SD = 5.2 ± 2.3 weeks) and 10 after 8 weeks (mean and SD = 33.9 ± 29.7 months). Eye alignment and fixation stability was measured using infrared recording systems and video. Visual acuity was assessed using forced-choice preferential looking techniques in the neonates and infants and with optotypes in the children. Fifteen of the 23 (65%) patients who experienced major form deprivation exhibited a nystagmus, of which 11 (73%) were manifest latent nystagmus (MLN). Nineteen of the 23 (85%) had strabismus. Of the nine patients who underwent early surgery (⩽8 weeks), two displayed a preoperative nystagmus whilst between 10 and 39 months post-operatively 8 (89%) exhibited a nystagmus. Of the group of 10 patients with minor cataracts only 2 (1 late surgery, 1 no surgery) had nystagmus and 2 strabismus. We conclude that following optimal post-operative management of infantile cataracts a sustained nystagmus—typically an MLN—is the most likely ocular motor outcome, even when the period of deprivation is as short as 3 weeks.

A case of manifest latent nystagmus of late onset in a 13-year-old girl is reported. The nystagmus became manifest during the development of a hypertropia of the left eye. The spontaneous nystagmus was successfully treated by surgical correction of the hypertropia. The observations are discussed with regard to theories on the origin of latent nystagmus.