The management of strabismus

The original causes of strabismus and the complications that develop from efforts by a child to adjust to the condition may present a complex diagnostic and therapeutic problem. The complications of suppression, amblyopia, contractures and anomalous visual habits may become more difficult to correct than the cause of the strabismus. The longer the duration of strabismus, the more complex the problem, the more difficult the treatment, and the less the probability of functional cure. Treatment should be started early. Correction may be brought about by the use of glasses, eye patches and orthoptic training, or by operation. If anatomic abnormality prevents bringing the eyes into line by conservative means, operation should be carried out after the best results possible by these means have been achieved. Surgical treatment, too, where it is indicated, should be done early, in order that normal binocular cooperation can develop before abnormal visual habits can become established.     

THE MANAGEMENT OF STRABISMUS

The original causes of strabismus and the complications that develop from efforts by a child to adjust to the condition may present a complex diagnostic and therapeutic problem. The complications of suppression, amblyopia, contractures and anomalous visual habits may become more difficult to correct than the cause of the strabismus. The longer the duration of strabismus, the more complex the problem, the more difficult the treatment, and the less the probability of functional cure. Treatment should be started early. Correction may be brought about by the use of glasses, eye patches and orthoptic training, or by operation. If anatomic abnormality prevents bringing the eyes into line by conservative means, operation should be carried out after the best results possible by these means have been achieved. Surgical treatment, too, where it is indicated, should be done early, in order that normal binocular cooperation can develop before abnormal visual habits can become established.     

Ophthalmic issues in hemangiomas of infancy

Hemangiomas are the most common benign tumor of infancy. Although most hemangiomas remain asymptomatic, certain hemangiomas can cause significant morbidity and require treatment. Periocular hemangiomas require close observation and early therapy for those lesions with potential for visual impairment. Hemangiomas typically cause visual morbidity by induction of amblyopia, strabismus, significant refractive error or optic nerve compromise. Diagnosis is typically straightforward but occasionally other entities may cause diagnostic confusion and radiologic evaluation can be helpful. This is particularly important if the hemangioma is one component of the PHACES syndrome. Therapeutic options which may be useful include steroids (oral, intralesional or topical), interferon alpha (usually reserved for life- or sight-threatening lesions due to serious potential side effects), laser, embolization and surgery. Ophthalmic treatment using patching, atropine, glasses and stabismus surgery may be necessary.     

Benefit of Bi-Ocular Visual Stimulation for Postural Control in Children with Strabismus

Vision is important for postural control as is shown by the Romberg quotient (RQ): with eyes closed, postural instability increases relative to eyes open (RQ = 2). Yet while fixating at far distance, postural stability is similar with eyes open and eyes closed (RQ = 1). Postural stability can be better with both eyes viewing than one eye, but such effect is not consistent among healthy subjects. The first goal of the study is to test the RQ as a function of distance for children with convergent versus divergent strabismus. The second goal is to test whether vision from two eyes relative to vision from one eye provides better postural stability. Thirteen children with divergent strabismus and eleven with convergent strabismus participated in this study. Posturtography was done with the Techno concept device. Experiment 1, four conditions: fixation at 40 cm and at 200 cm both with eyes open and eyes covered (evaluation of RQ). Experiment 2, six conditions: fixation at 40 cm and at 200 cm, with both eyes viewing or under monocular vision (dominant and non-dominant eye). For convergent strabismus, the groups mean value of RQ was 1.3 at near and 0.94 at far distance; for divergent, it was 1.06 at near and 1.68 at far. For all children, the surface of body sway was significantly smaller under both eyes viewing than monocular viewing (either eye). Increased RQ value at near for convergent and at far for divergent strabismus is attributed to the influence of the default strabismus angle and to better use of ocular motor signals. Vision with the two eyes improves postural control for both viewing distances and for both types of strabismus. Such benefit can be due to complementary mechanisms: larger visual field, better quality of fixation and vergence angle due to the use of visual inputs from both eyes.     

斜视矫正手术对双眼视觉功能影响的临床研究

目的:探讨斜视矫正手术对双眼视觉功能的影响。方法:将收集的85例斜视患者根据斜视类型分组,共同性外斜视组51例,占60.00%;共同性内斜视组16例,占18.82%。麻痹性斜视组13例,占15.30%,特殊类型斜视组5例,占5.88%。同视机检查并记录患者术前及术后双眼视功能情况。结果:外斜视手术方式多选用单眼外直肌后徙+内直肌缩短术,内斜视手术主要选用双眼内直肌后徙术,上斜肌麻痹多行患眼下斜肌适量后徙或转位术,麻痹性内斜和外斜手术方式为患眼水平肌后徙联合缩短术,外斜V征手术方式为双眼外直肌后徙联合上移半个肌腱,伴有斜肌亢进者需同时行斜肌减弱术,固定性内斜1例手术方式为患眼内直肌断键+直肌联结术。85例患者术后正位73例(85.89%),双眼视觉功能手术前后比较有显著性差异(P0.05),术后较术前可见明显改善。结论:斜视矫正手术可促进双眼视觉功能的恢复,尤其是对于学龄前儿童效果更明显。     

NONSURGICAL TREATMENT OF CONVERGENT STRABISMUS

It is generally agreed that surgical treatment of convergent strabismus should be withheld until all other less traumatic approaches have proved ineffectual. There are four categories of nonsurgical treatment.One is psychiatric. Too often psychiatric problems in the causation of convergent strabismus are either overlooked or unrecognized.Another is the proper employment of optical devices. For example, spectacle lenses to eliminate the need for excessive accommodation with its associated convergence excess, and the employment of prisms in the lenses to permit the two eyes to see as a unit even though they may not be properly anatomically oriented.Another kind of treatment is orthoptics, the use of exercises and rather complex optical equipment in a laboratory to train the patient in coordination between the two eyes.Treatment with drugs is based on the fact that certain drugs reduce the effort necessary for accommodation (much as eye-glasses do) and therefore lessen the stimulus toward convergence which may possibly tend toward the development of convergent strabismus.     

Effects of cortical damage on binocular depth perception

Stereoscopic depth perception requires considerable neural computation, including the initial correspondence of the two retinal images, comparison across the local regions of the visual field and integration with other cues to depth. The most common cause for loss of stereoscopic vision is amblyopia, in which one eye has failed to form an adequate input to the visual cortex, usually due to strabismus (deviating eye) or anisometropia. However, the significant cortical processing required to produce the percept of depth means that, even when the retinal input is intact from both eyes, brain damage or dysfunction can interfere with stereoscopic vision. In this review, I examine the evidence for impairment of binocular vision and depth perception that can result from insults to the brain, including both discrete damage, temporal lobectomy and more systemic diseases such as posterior cortical atrophy.This article is part of the themed issue ‘Vision in our three-dimensional world’.     

COMMON EYE PROBLEMS IN CHILDREN

Most penetrating or lacerating injuries of the eye in children justify examination under anesthesia to avoid further harm to an uncooperative patient. The pediatrician in doubt should merely apply a sterile dressing and have an ophthalmologist examine the injury in hospital. Nonperforating injuries may result in severe bleeding 48 to 72 hours later; this may be averted by bandaging the eyes and maintaining rest for four or five days. Removal of foreign bodies should be followed by application of antibiotic ointment and patching to prevent contamination.Congenital stenosis of the lacrimal duct may clear spontaneously or through application of decongestants and sympathomimetic drops. More severe effects, especially infection, justify probing at six months or earlier. The operation should be done under general anesthesia, preferably in hospital.Acute conjunctivitis is best treated by local application of antibiotics or sulfonamides only. Chronic infections may be better managed with the addition of corticosteroids, which reduce local inflammation and control bacterial reaction. Bacterial study should be done only if empirical antibiotic therapy fails. Bacterial desensitization may be helpful. The same methods are effective in blepharitis, aided by hygienic measures. Corticosteroids are most useful in allergic inflammations.Refractive difference is difficult to test before a child can read, and apparent defects may be due to lack of cooperation. Marked inequality of the eyes may signify organic disorder. Strabismus, on the other hand, can be detected as early as 12 or 15 months and should be treated as early as possible by proper lenses, surgery, or both. Pediatricians and parents should be aware that many children appear to have strabismus because of wide epicanthi and deep-set eyes.     

Facilitation of Visual Perception in Head Direction: Visual Attention Modulation Based on Head Direction

People usually see things using frontal viewing, and avoid lateral viewing (or eccentric gaze) where the directions of the head and eyes are largely different. Lateral viewing interferes with attentive visual search performance, probably because the head is directed away from the target and/or because the head and eyes are misaligned. In this study, we examined which of these factors is the primary one for interference by conducting a visual identification experiment where a target was presented in the peripheral visual field. The critical manipulation was the participants’ head direction and fixation position: the head was directed to the fixation location, the target position, or the opposite side of the fixation. The performance was highest when the head was directed to the target position even when there was misalignment of the head and eye, suggesting that visual perception can be influenced by both head direction and fixation position.     

Eye-specific segregation of optic afferents in mammals,fish, and frogs: The role of activity

Eye-specific patches or stripes normally develop in the visual cortex and superior colliculus of many (but not all) mammals and are also formed, after surgically produced binocular innervation, in the optic tectum of fish and frogs. The segregation of ocular dominance patches or columns has been studied using a variety of anatomical pathway-tracing techniques, by electrophysiological recording of postsynaptic units or field potentials, and by the 2-deoxyglucose method following visual stimulation of only one eye. In the tectum of both fish and frogs and in the cortex and colliculus of mammals, eye-specific patches develop from initially diffuse, overlapping projections. Of the various mechanisms that might cause such segregation, the evidence favors an activity-dependent process that stabilizes synapses from the same eye because of their correlated activity. First, several environmental manipulations affect the segregation of afferents in visual cortex: strabismus and alternate monocular exposure apparently enhance segregation, whereas dark rearing slows the segregation process, and monocular deprivation causes the experienced eye to form larger patches at the expense of those of the deprived eye. Second, blocking activity in both eyes is effective in preventing the segregation both in the tectum of fish and frog and in the visual cortex of cat. With the eyes blocked, alternate stimulation of the optic nerves permits the segregation of ocular dominance, at least onto single cells in the cat visual cortex. These findings are discussed in terms of an activity-dependent stabilization of those synapses having correlated activity (those from neighboring ganglion cells within one eye) but not of those lacking correlated activity (those from left and right eyes). We suggest that the eye-specific patches represent a compromise between total segregation of the projections from the two eyes and the formation of a single continuous retinotopic map across the surface of the cortex or tectum.     

框架眼镜联合角膜塑形镜矫正青少年高度近视的临床疗效及对角膜内皮细胞和泪膜的影响

目的:探讨框架眼镜联合角膜塑形镜矫正青少年高度近视的临床疗效及对角膜内皮细胞和泪膜的影响.方法:选取2018年1月～2019年3月期间我院收治的青少年高度近视患者98例(181眼),根据信封抽签法分为对照组49例92眼(框架眼镜配戴治疗)和观察组49例89眼(对照组基础上联合角膜塑形镜治疗).对比两组裸眼视力、屈光度、...     

Biofeedback techniques in the treatment of visual and ophthalmologic disorders

The literature on the use of biofeedback techniques in the treatment of visual and opthalmologic disorders is reviewed. Although this consists mainly of case studies, there is mounting evidence that biofeedback may be applicable to the treatment of strabismus, nystagmus, blepharospasm, elevated intraocular pressure, and myopia. Because of the success in applying biofeedback techniques in the treatment of other neuromuscular disorders, it is concluded that the use of these techniques in the treatment of blepharospasm and strabismus shows the most promise.     

Ocular motility in craniofacial reconstruction

Of 140 children undergoing major craniofacial reconstruction at The Children's Hospital of Philadelphia and examined preoperatively and postoperatively by the Ophthalmology Division, only 10 had surgically induced alteration in primary position horizontal alignment, 4 greater than 10 prism diopters. Only 2 patients had a new strabismus in primary position created by craniofacial surgery, both cranial nerve palsies. We believe early strabismus surgery is advantageous for attainment of binocularity and ease of tissue manipulation. Of 44 patients with craniofacial dysostosis (Crouzon), 20 had preoperative strabismus, and 12 required extraocular muscle surgery. Five of 12 had anomalies of extraocular muscle number and structure, usually involving the superior rectus muscle.     

The long-term effectiveness of different regimens of occlusion on recovery from early monocular deprivation in kittens.

Although the behavioural effects of an early period of monocular deprivation imposed on kittens can be very severe, resembling an extreme form of the human clinical condition deprivation amblyopia, they are not necessarily irreversible. Considerable behavioural as well as physiological recovery can occur if normal visual input is restored to the deprived eye sufficiently early, particularly if the other (initially non-deprived) eye is occluded at the same time (reverse occlusion). However, past work has shown that in many situations the improvement in the vision of the initially deprived eye that occurs during reverse occlusion is not retained following the subsequent introduction of binocular visual input. Furthermore, the vision of the other eye is often reduced as well, with the result that the eventual outcome is a condition of bilateral amblyopia. This study first examines the consequences of several periods of reverse occlusion whose onset and duration would be thought to maximize the opportunity for good and long-standing recovery of vision in the initially deprived eye. However, only in a very restricted set of exposure conditions did animals acquire good vision in one or both eyes; in most situations the final outcome was one of bilateral amblyopia. A second set of experiments examined the consequences of various regimens of part-time reverse occlusion, where the initially non-deprived eye was occluded for only part of each day to allow a period of binocular visual exposure, on kittens that had been monocularly deprived until 6, 8, 10 or 12 weeks of age. Whereas short or long daily periods of occlusion of the initially non-deprived eye resulted eventually in amblyopia in one, or usually both, eyes, certain intermediate occlusion times (3.5 or 5 h each day) resulted in recovery of normal acuities, contrast sensitivity and vernier acuity in both eyes, in animals that had been monocularly deprived until 6, 8 or 10 weeks of age, but not in animals deprived for longer periods. Experiments were done to establish some of the factors that contributed to the successful outcome associated with certain of the regimens of part-time reverse occlusion. It was established that recovery was just as good in animals in which the visual axes were vertically misaligned by means of prisms during the daily period of binocular visual exposure, thereby indicating that the visual input to the two eyes need not be concordant. However, animals that received equivalent visual exposure of the two eyes each day, but successively rather than simultaneously, all developed very severe bilateral amblyopia.(ABSTRACT TRUNCATED AT 400 WORDS)     

Comments on the eyes of tardigrades

A survey is given on the scarce information on the visual organs (eyes or ocelli) of Tardigrada. Many Eutardigrada and some Arthrotardigrada, namely the Echiniscidae, possess inverse pigment-cup ocelli, which are located in the outer lobe of the brain, and probably are of cerebral origin. Occurrence of such organs in tardigrades, suggested as being eyeless, has never been checked. Depending on the species, response to light (photokinesis) is negative, positive or indifferent, and may change during the ontogeny. The tardigrade eyes of the two eutardigrades examined up to now comprise a single pigment cup cell, one or two microvillous (rhabdomeric) sensory cells and ciliary sensory cell(s). In the eyes of the eutardigrade Milnesium tardigradum the cilia are differentiated in an outer branching segment and an inner (dendritic) segment. Because of the scarcity of information on the tardigrade eyes, their homology with the visual organs of other bilaterians is currently difficult to establish and further comparative studies are needed. Thus, the significance of these eyes for the evolution of arthropod visual systems is unclear yet.     

Dynamics of parietal neural activity during spatial cognitive processing

Dynamic neural processing unrelated to changes in sensory input or motor output is likely to be a hallmark of cognitive operations. Here we show that neural representations of space in parietal cortex are dynamic while monkeys perform a spatial cognitive operation on a static visual stimulus. We recorded neural activity in area 7a during a visual maze task in which monkeys mentally followed a path without moving their eyes. We found that the direction of the followed path could be recovered from neuronal population activity. When the monkeys covertly processed a path that turned, the population representation of path direction shifted in the direction of the turn. This neural population dynamic took place during a period of unchanging visual input and showed characteristics of both serial and parallel processing. The data suggest that the dynamic evolution of parietal neuronal activity is associated with the progression of spatial cognitive operations.     

吉西他滨眼内应用抑制兔眼白内障术后 后囊膜混浊的实验研究

目的：研究眼内应用浓度为5mg／ml的吉西他滨（GEM）对于后囊膜混浊的抑制作用。方法：12只（24眼）实验动物随机分为A、B二组,A组为治疗组,B组为对照组。所有的实验动物均进行晶状体囊外摘除＋人工晶体植入术。A组术中应用5mg/ml吉西他滨溶液作水分离;B组术中应用平衡盐溶液作水分离。术后定期观察角膜水肿,评价PCO及进行角膜内皮细胞分析。结果：术后第1天,第3天,第7天两组角膜水肿的例数均无差异。术后第二周,两组后囊膜发现不同程度混浊,第四周后囊膜混浊程度分级,对照组中央后囊明显混浊;角膜内皮细胞分析显示两组的角膜内皮数量明显低于术前,比较两组的角膜内皮数量减少量无统计学意义。结论：实验显示眼内应用5mg／ml吉西他滨后囊膜混浊程度较对照组明显轻。尽管眼内应用有导致眼内组织毒性反应的可能性,但通过用药方法的改进和保护措施的加强是可以有效避免或减轻的,因此吉西他滨是一种有潜力的预防后发性白内障的侯选药物。     

Dispersal between shallow and abyssal seas and evolutionary loss and regain of compound eyes in cylindroleberidid ostracods: conflicting conclusions from different comparative methods

Complex organs such as eyes are commonly lost during evolution, but the timescale on which lost phenotypes could be reactivated is a matter of long-standing debate, with important implications for the molecular mechanisms of trait loss. Two phylogenetic approaches have been used to test whether regain of traits has occurred. One way is by comparison of nested, continuous-time Markov models of trait evolution, approaches that we term tree-based tests. A second way to demonstrate statistical support for trait regain is through use of node-based tests that employ explicit estimation of ancestral node states. Here, we estimate new molecular and morphological phylogenies and use them to examine the possibility of eye regain and dispersal between abyssal and shallow seas during the history of cylindroleberidid ostracods, a family of about 200 species, comprising both eyeless and sighted species. First, we confirmed that eye presence/absence is correlated with habitat depth. Parameter estimates from a phylogenetic model indicate that speciation is more rapid in deep-sea eyeless clades compared with shallow-water sighted clades. In addition, we found that tree-based statistical tests usually indicated reversals, including both transitions from deep to shallow seas and regain of eyes. In contrast, node-based statistical tests usually failed to show significant support for reversals. These results also hold for simulated phylogenies, indicating that they are not unique to the current data set. We recommend that both tree-based and node-based tests should be examined before making conclusions about character reversal and that ideally, alternative character histories should be tested using additional data, besides just the phylogenetic distribution of presence/absence of the characters.     

Pituitary Ablation for Diabetic Retinopathy

Pituitary ablation was performed on 26 patients with advanced diabetic retinopathy by pituitary stalk section (nine patients) or transphenoidal hypophysectomy (17 patients). After a latent period varying from six to 12 months, retinal hemorrhages disappeared, vitreous hemorrhages stopped and new vessels regressed. Eight of 10 patients followed up for more than a year had a complete remission, although in one of two patients whose ablation was incomplete the retinopathy remained active. Preoperative visual acuity levels were preserved in 47 of 50 eyes of patients followed up for a mean period of 12 months. Three patients have died, two from causes related to their operation. Twenty of the survivors have continued in their usual occupation. Pituitary ablation is effective in preventing the progressive visual deterioration usually associated with advanced diabetic retinopathy.