Von Noorden Research Articles

Ocular Suppression Development at Age 12 Years

BACKGROUND: The patient experienced idiopathic increased intracranial pressure (pseudotumor cerebri syndrome) leading to an acquired, constant left exotropia at age 12 years. She had diplopia for about 2 months which resolved due to apparent suppression of the left eye. The patient has maintained the suppression without developing amblyopia through her current age of 17 years despite a stable large left exotropia, optic atrophy, and visual field defect. SIGNIFICANCE: The case is unusual because suppression has been assumed to develop only prior to age 10 years. BACKGROUND AND PURPOSE: Ocular suppression is an active neuroplastic process and is presumably limited to a sensitive period in childhood. It occurs when there is a difference in image clarity between the two eyes. The two most common causes are clinically significant anisometropia and strabismus. The strabismus may be monocular and constant, alternating and constant, or intermittent. The presence of suppression in anisometropia or constant monocular strabismus often leads to monocular amblyopia. The literature contains extensive animal, laboratory, and clinical evidence on the sensitive period of amblyopia, its causes, and its remediation. It is well established that amblyopia develops prior to about age 7 years, can recur up to about age 10 years, but does not develop, recur, or regress after age 12 years. Generally, response to amblyopia treatment is most robust during the sensitive period, but it is well documented that successful treatment is possible through the teen years and even adulthood. Few reports exist on suppression without amblyopia and most are based on clinical experience. von Noorden and Campos state: “As with other sensorial adaptations, such as amblyopia and anomalous retinal correspondence (ARC), the ability to suppress is limited to the immature visual system, that is, it develops only in children. Although no comparative studies exist, it is our clinical impression that the sensitive period during which suppression may develop ends after the age of 8 or 9 years”. The present paper reports an interesting case of an apparent onset of suppression at age 12 years in a patient with acquired, constant, unilateral strabismus secondary to idiopathic increased intracranial pressure.

Short-Term Dietary Oatmeal Interventions in Adults With Type 2 Diabetes: A Forgotten Tool

Dietary modifications play a central role in the treatment of diabetes. Educating and empowering individuals to make better dietary choices is a challenging task. In this context, 1 potential dietetic approach to achieve better glycemic control in type 2 diabetes is often overlooked: the use of short-term dietary oatmeal interventions. This concept was described more than 100 years ago by the German diabetologist Carl von Noorden. It is still applied in several German hospitals, but in a modified form. Although von Noorden initially prescribed a diet including oatmeal, butter and vegetables, some physicians nowadays tend to omit butter from the diet. The result is a hypocaloric, plant-based dietary intervention that is low in fat and excludes animal protein for a short period. This short-term dietary intervention has been associated with a significant reduction in mean blood glucose concentrations and an improved insulin sensitivity in patients with type 2 diabetes. Almost forgotten, short-term dietary oatmeal interventions are an economical, yet highly effective tool to achieve better glycemic control in patients with type 2 diabetes.

The influence of ocular sighting dominance on Fundus torsion in patients with unilateral congenital superior oblique palsy.

The purpose of our study was to determine whether ocular sighting dominance may influence the ocular torsion in patients with unilateral congenital superior oblique palsy (UCSOP). This retrospective study included 22 UCSOP patients with radiologic evidence of unilateral superior oblique muscle hypoplasia on orbital magnetic resonance imaging and 66 healthy individuals with normal ocular motility as controls. Ocular torsion was assessed both quantitatively and qualitatively using digital fundus photography. The disc-fovea angle (DFA) was measured quantitatively using image software on a computer screen. All fundus photographs were qualitatively graded as normal torsion, extorsion, or intorsion in all subjects, based on the location of the optic disc relative to the fovea, according to the Bixenman and von Noorden's criteria. Ocular sighting dominance was assessed by the hole-in-the-card test and the pointing test. The Mann-Whitney U test and Fisher's exact test were used to determine the association between the ocular sighting dominance and the ocular torsion. The median DFA was significantly larger in the eyes of patients with UCSOP (9.1° in the paretic eyes and 9.3° in the non-paretic eyes) than the eyes of the control group (4.3°, p<0.001 for both). Ocular dominance tests displayed that, among 22 patients, 11 were paretic eye dominant and the other 11 were non-paretic eye dominant. The sighting-dominant eyes demonstrated significantly smaller median DFA than the non-dominant eyes (8.3° and 10.7°, respectively, p=0.033), regardless of which eyes were paretic. Ten eyes of ten patients had extorsion, none had intorsion, and all the eyes of remaining 12 patients had no abnormal torsion, qualitatively. All the eyes showing extorsion in fundus photography were non-dominant eyes, regardless of whether the eyes were paretic or non-paretic. Our findings illuminate the importance of considering ocular sighting dominance for properly assessing ocular torsion in patients with UCSOP. Ocular sighting dominance may have an influence on objective ocular torsion in a way that decreases the torsion in the dominant eye, thereby hindering the abnormal ocular torsion from appearing in that eye.

Historical Perspective: Nonsurgical Treatment of Intermittent Exotropia

Intermittent exotropia is rich in our orthoptic history, with different modes of therapy as well as surgical methods to improve the eye drifting. We explore the very earliest nonsurgical treatments documented from the Aeginaeta mask from 600 A.D. to a plethora of devices and techniques throughout the 1800s and 1900s, including stereograms, the cheiroscope, the Tibbs Binocular Trainer, and finally to computerized orthoptic programs in the twenty-first century. We note several other founding and instrumental scientists and researchers in the field's early beginning as well as the American heritage of orthoptics. From Javal, Hering, and Mary and Edmund Maddox to Elizabeth Stark, Burian, Scobee, von Noorden, Dorothy Thompson, and Sally Moore, we delve into many influential ideas, theories, and inventions. The scientific basis for many treatments and the monumental advancements made in the field of ocular motility will be discussed.

Stereovision in patients with intermittent exotropia before and after surgical treatment

PurposeTo determine the effect of the initial stereovision on the outcome of intermittent exotropia surgical treatment.Methods20 patients with intermittent exotropia aged 10–21 years with visual acuity with correction 0.88 ± 0.29 who received surgical treatment were observed. Angle of deviation before surgery was 6–25 degrees, in average 15.7 ± 1.3 deg. for fare distance and near in average of 8.2 ± 2.18 deg, vertical component 0–3 degrees was observed in 65% of patients who underwent surgical treatment in accordance with generally accepted surgery tactic ‐ recessions and resections of extraocular muscles (Avetisov E. S.,1977, Von Noorden, E. Campos, 2002). Before and after treatment conventional ophthalmic examination and stereoacuity were determined using the Test Lung 2 in all patients.ResultsAs a result of treatment the angle of exotropia decreased in all patients and was in average 3.9 ± 1.9 deg for distance and 3.5 ± 1.4 deg for near, binocular vision was restored in 70% (14) of patients. Before treatment, only in 25% (5) of patients showed stereoacuity for near (200–600 arc sec) and 75% (11) did not show stereovision. After treatment, the stereoacuity for near increased and was detected in 65% of cases (13), compared to 5 that were before treatment (χ2 = 6.4, p = 0.01). Alignment of eyes and best stereoacuity (200–400 arc sec) was found after treatment and appeared in individuals who showed stereoacuity for near 200 arc sec before surgery and the nearest point of convergence less than 6 cm.ConclusionsPreliminary data suggest that in patients with intermittent form of exophoria good stereoacuity for near is a favorable factor for the prediction of treatment. In patients with orthotropic position of eyes stereoacuity after surgical treatment increased in 65% of cases.

Comparison between limbal (von Noorden) and para limbal (Santiago) conjunctival incisions for adjustable recessions of horizontal recti

Both limbal and para limbal conjunctival incisions are routinely used in strabismus surgery with comparable results however their outcome has not been compared while using adjustable sutures. To compare limbal (von Noorden) and para limbal (Santiago) conjunctival incisions for adjustable recessions of horizontal recti. Uniocular adjustable recessions (with conventional non adjustable resection) in 24 appropriate patients were performed according to standard slip knot technique. The patients were assigned to the two groups after obtaining an informed consent using systematmic randomization. Twelve patients in first group received the von Noorden incision with bare sclera closure and 12 in the second group received the Santiago's modification of Swan incision with deferred closure. The surgeries were performed by a single surgeon and the adjustments performed after 24 hours. The incisions were studied on the established subjective (pain) and objective (hyperaemia, chemosis, discharge and gap in incision) variables at follow ups of 1st day post adjustment, 2 weeks and 12 weeks. 'Repeated Measures Anova' test was used for statistical analysis. A p value Less than 0.05 was considered statistically significant. The limbal incision was superior to the paralimbal incision on both objective and subjective criteria by 'Repeated Measures Anova' test. We recommend using limbal incision and avoiding para limbal incisions while performing adjustable recessions.

Is type 2 diabetes a category error?

Is type 2 diabetes a category error?

New strabismus surgical techniques

Five new strabismus surgical procedures were developed by the authors and were presented as a workshop at the AAPOS annual meeting of the American Association for Pediatric Ophthalmology and Strabismus. They are summarized here to introduce these methods to the reader and provide surgeons with more options in approaching difficult strabismus problems. Diagnosis and correction of consecutive strabismus attributable to stretched scar is discussed. The pulley posterior fixation procedure is a unique approach to correct high accommodative convergence or to augment a maximal medial rectus recession. Diagnosis and repair of the partial avulsion (flap tear) of a rectus muscle allows correction of some restrictive strabismus following blunt trauma. The nasal myectomy of the inferior oblique muscle corrects persistent inferior oblique overaction without sacrificing the tether effect gained by a previous anterior transposition of the inferior oblique. The full advancement of the superior oblique tendon offers another option to strengthen a weak superior oblique muscle.

Preferred Retinal Loci Relationship to Macular Scotomas: A10-Year Comparison

Age-related maculopathy is the leading cause of vision loss among adults in developed countries, and its prevalence is expected to double over the next decade (Congdon et al., 2004; Friedman et al., 2004). The two forms of age-related maculopathy--exudative and nonexudative--are capable of affecting the macula, with potential symptoms including decreased contrast sensitivity, decreased visual acuity, abnormal adaptation to the dark, and central or pericentral scotomas (Jager, Mieler, & Miller, 2008). When a central scotoma impairs the ability of the fovea to distinguish detail, one or more preferred retinal loci (PRL) (Schuchard & Raasch, 1992; von Noorden & Mackensen, 1962; White & Bedell, 1990), also known as pseudo-foveas (Guez, Le Gargasson, Rigaudiere, & O'Regan, 1993), naturally develop at eccentric retinal locations and become the new points of fixation. The location of the PRL varies from person to person, as does the ability to maintain steady fixation with the PRL and to use it for reading and activities of daily living (Dalgleish & Naylor, 1963; Fletcher, Schuchard, & Watson, 1999; Timberlake et al., 1986; Whittaker, Budd, & Cummings, 1988). Fletcher and Schuchard (1997) reported the results of a study examining patterns of PRL ability and location relative to macular scotomas. They mapped dense scotomas and determined the location of the PRL in 1,339 eyes in 825 persons with a scanning laser ophthalmoscope during a standard low vision rehabilitation evaluation. Fletcher and Schuchard created a scoring system to measure the pursuit ability, fixation stability, and saccadic ability of the PRL. They determined the characteristics of dense scotomas within 2.5 degrees of the PRL or fovea. Of the 1,339 eyes, 84% (1,130) demonstrated an established PRL, ranging in size from 1.0 degrees to 9.0 degrees in diameter, and 82.5% had a central dense scotoma. The PRL had no dense scotomas on any border in 14.8% of the eyes. It had one, two, or three borders with a dense scotoma in 39.7%, 19.0%, and 9.0% of the eyes, respectively. Ring scotomas, bordering the PRL on four borders, were present in 17.4% of the eyes. Of the eyes with one scotomatous border, most had a field defect located either superior (39.0%) or to the right (33.7%). It was less common for the eyes to have field defects to the left or inferior, with 19.9% and 7.5% of the eyes, respectively. This report presents a 10-year comparison of these previous findings. It examines whether the PRL characteristics of persons with low vision remained steady over the ensuing decade. Changes in PRL and visual field characteristics among persons with low vision over time could have implications for the approaches of low vision rehabilitation professionals to training in eccentric viewing and other rehabilitation techniques. METHODS The study used 271 persons who were referred to the Frank Stein and Paul S. May Center for Low Vision Rehabilitation at California Pacific Medical Center (CPMC) in San Francisco between 2005 and 2007. All consecutive patients with low vision were included in the study, regardless of age, gender, race, and other demographic variables. Participants were excluded only if they lacked the cognitive or physical ability to complete a macular perimetry examination, as determined by the clinical impression of the ophthalmologist. Approval from the institutional review board was obtained from CPMC for the retrospective analyses of charts. As part of the standard low vision rehabilitation evaluation, an ophthalmologist measured visual acuity with the Early Treatment of Diabetic Retinopathy System chart (Ferris, Kassoff, Bresnick, & Bailey, 1982). The characteristics of the scotoma and PRL were measured with a Scanning Laser Ophthalmoscope (SLO; SLO-101, Rodenstock, Dusseldorf, Germany). The SLO was outfitted with a smart microperimetry (MacKeben & Gofen, 2007) program with a gaze-contingent display that automatically monitors eye movements, blinks, and other factors. …

Evidence that convergence rather than accommodation controls intermittent distance exotropia

This study considered whether vergence drives accommodation or accommodation drives vergence during the control of distance exotropia for near fixation. High accommodative convergence to accommodation (AC/A) ratios are often used to explain this control, but the role of convergence to drive accommodation (the CA/C relationship) is rarely considered. Atypical CA/C characteristics could equally, or better, explain common clinical findings. Nineteen distance exotropes, aged 4-11 years, were compared while controlling their deviation with 27 non-exotropic controls aged 5-9 years. Simultaneous vergence and accommodation responses were measured to a range of targets incorporating different combinations of blur, disparity and looming cues at four fixation distances between 2 m and 33 cm. Stimulus and response AC/A and CA/C ratios were calculated. Accommodation responses for near targets (p = 0.017) and response gains (p = 0.026) were greater in the exotropes than in the controls. Despite higher clinical stimulus AC/A ratios, the distance exotropes showed lower laboratory response AC/A ratios (p = 0.02), but significantly higher CA/C ratios (p = 0.02). All the exotropes, whether the angle changed most with lenses ('controlled by accommodation') or on occlusion ('controlled by fusion'), used binocular disparity not blur as their main cue to target distance. Increased vergence demand to control intermittent distance exotropia for near also drives significantly more accommodation. Minus lens therapy is more likely to act by correcting overaccommodation driven by controlling convergence, rather than by inducing blur-driven vergence. The use of convergence as a major drive to accommodation explains many clinical characteristics of distance exotropia, including apparently high near stimulus AC/A ratios.

Paradoxical Improvement of Visual Acuity in Macular Disease

Purpose: Improvement in visual acuity is often considered the best indicator of the effectiveness of a treatment in age-related maculopathy. However, during the course of the disease, the location of the patients’ preferred retinal locus of fixation may change. This can lead to an unexpected functional improvement, unrelated to treatment.Methods: From a running database of 1,369 retina patients, we identified 116 patients over 60 years of age when age-related maculopathy was diagnosed based on the following inclusion criteria: one study eye with an initial acuity of the logarithm of the minimum angle of resolution (logMAR) 0.7 or worse, a fellow eye with central fixation and a follow-up period of 3 years or more with precise documentation of the preferred retinal locus of fixation and scotoma distribution for both eyes using scanning laser ophthalmoscopy-based microperimetry.Results: We expected an improvement in the visual acuity in one eye (study eye) without the possibility of improvement due to previous or concurrent treatment in that eye. Twelve patients met the selection criteria. Over time, these patients had significant improvements in the visual acuity in the weaker study eye, characteristically accompanied by a concurrent decrease in visual acuity in the other eye, which initially had better visual acuity. Moreover, in all the study eyes, an unstable pseudo-central von Noorden fixation pattern evolved into a more stable eccentric preferred retinal locus.Conclusions: Visual acuity remains the gold standard for assessing visual functioning in age-related maculopathy when interpreted with caution. Improvements in visual acuity can occur solely due to the course of the disease in the other eye and as a result of its impact on binocular fixation characteristics. This finding has significant implications for low-vision rehabilitation and evaluation of various therapies in large long-term clinical studies.

Literature Commentary

W e thank Drs. Mbekeani and Slamovits for their interest in our article (1). As an author, one always lives in fear of receiving the news that one's literature search did not capture all prior reports. Gunter von Noorden, MD, used to caution residents that it was unlikely that anything in the modern English medical literature was truly the first report of anything as a thorough review of the German (and other non-English language) literature would likely produce a similar prior report. We appreciate Drs. Mbekeani and Slamovits bringing our oversight to our attention (2). We agree that ophthalmologists should always ask patients who present with orbital or ocular inflammation about the use of bisphosphonates. This is especially true in an era when many ophthalmologists may become less interested in the use of systemic medications. In obtaining a patient's history, medication lists often look like the following: “some type of anti-inflammatory,” “some lung medicine,” “some kind of bone treatment,” or the worst shortcut of all … “see list.” Most of the time we get away with it as eye MDs, but what if that “anti-inflammatory” is hydroxychloroquine, that “lung medicine” ethambutol, or that “bone treatment” is a bisphosphonate? Bo Yang, MD Andrew G. Lee, MD Houston, Texas

Fat and Energy Economy in Hypo- and Hyperthyroidism Are Not the Mirror Image of One Another

That thyroid hormone (TH) stimulates the rate of metabolism and heat production has been known for over a century. Adolf Magnus-Levy, a German physician and physiologist, asked in 1895 a very insightful question that today may seem trivial, namely whether the changes in weight observed in hyperand hypothyroid patients in disproportion to food intake had anything to do with metabolism. He and his mentor, Carl von Noorden, had developed the conceptual bases and the technology to measure metabolism, i.e. the rate of oxidations in the body. Seemingly, von Noorden’s interest in the thyroid was less than Magnus-Levy’s, so this latter took upon himself the studies that he published in a three-page article (1) of the Berlin Clinical Journal. He reported that both oxygen consumption (VO2) and carbon dioxide production were increased in patients with hyperthyroidism, that the abnormalities disappeared when the condition was cured, and that he could reproduce in healthy subjects the abnormalities observed in thyrotoxic patients when given thyroid extract for a few weeks. Of interest to the discussion that follows, the respiratory exchange ratio (RER) or respiratory quotient was reduced by TH. More than a century has gone by, yet we still cannot pinpoint the mechanisms whereby TH causes such changes in metabolism, although we have a better appreciation of the biological meaning and its impact in evolution. The article by Klieverik et al. (2) in this issue makes several points that significantly add to our understanding as to how TH influences energy economy in whole animals and raises concepts of potential value to understand energy balance and deal with the pandemic of obesity. Living systems are open, in a free exchange of energy with the environment. Through millions of years of evolution during which food has never been as readily available as it is now, species selected efficient mechanisms to seek and obtain food and to conserve energy. In this regard, the advent of homeothermy imposed a big challenge by forcing homeothermic species to consume more energy to just burn it and produce heat, essential to maintain the set core temperature ( 37 C) in environments usually cooler, particularly in latitudes far from the equator. Comparisons between poikilothermic and homeothermic species under strictly controlled conditions have shown that warm-blooded animals spend much more energy, whether as a whole or tissue by tissue (3). Furthermore, whether one looks at the energy cost of biochemical or physiological activities, this is higher in warm-blooded animals, indicating that the energy cost of living is higher in these species and that thermodynamic efficiency is reduced for the sake of producing heat (4). A large body of evidence indicates that TH is largely responsible for these differences between poikilothermic and homeothermic species. Furthermore, amphibian metamorphosis, a THdependent process, it is an energy-costly process, markedly accelerated by TH (5), yet the energy cost of bringing this process rapidly to an end is much less than resting energy expenditure (REE) of a comparable size mammal (6). Likewise, for any given amount of mechanical work, heat production is markedly greater in euthyroid than hypothyroid skeletal muscle (7). So, TH increases the energy cost of living, and the difference is largely accounted for by energy that is simply dissipated as heat for the sake of temperature homeostasis.

Training Children in Eccentric Viewing: A Case Study

Eccentric viewing is a strategy that is used to ameliorate the impact of the loss of macular vision through the use of the viable peripheral retina as an alternative to the nonfunctional fovea or macula. The efficacy of this technique has been reported in relation to adults with age-related macular degeneration (AMD) (Fitzmaurice, Kinnear, & Chen, 1994; Goodrich & Mehr, 1986; Nilsson & Nilsson, 1994; Vukicevic & Fitzmaurice, 2005). However, a keyword search of a range of appropriate databases (PubMed, CINAHL, Current Contents, and Google Scholar) did not yield any articles that specifically reported the provision of training in eccentric viewing to children. Retinal adaptation to the loss of the foveal function has been well described in the literature, particularly in relation to strabismus. The choice of the fovea for fixation is based on the high quality of vision that is provided; the sensation of straight-ahead viewing; and the fact that the fovea is the zero point for the oculomotor system, thus maintaining fixation on the object of regard (Duke-Elder & Wybar, 1973). The extent to which an eccentric fixation point develops these characteristics determines whether the anomalous situation is eccentric fixation or viewing. Eccentric fixation occurs when the eccentric position provides the best-available vision and straight-ahead oculomotor reference. Eccentric viewing occurs when an eccentric position is used to improve vision, with oculomotor orientation remaining referenced to the fovea and the person being aware that he or she is not looking at the object of regard (von Noorden & Mackensen, 1962). When foveal vision is lost because of macula or optic nerve disease and a person looks beyond the object of regard to place the image on a viable area of the peripheral retina, it is considered eccentric viewing (Duke-Elder & Wybar, 1973; von Noorden, 1990). The natural development of the use of nonfoveal loci to improve potential sight in the presence of a central scotoma has been well described in the literature, with the anomalous fixation point described as a preferred retinal locus (Crossland, Sims, Galbraith, & Rubin, 2004; Fletcher & Schuchard, 1997; Macedo, Nascimento, Gomes, & Puga, 2007; Reinhard et al., 2007; Schuchard, 1995). Some researchers have described a trained retinal locus, a term that is generally used to indicate that training has been used to modify the position of the naturally selected preferred retinal locus (Deruaz et al., 2006; Nilsson, Frennesson, & Nilsson, 2003; Watson, Schuchard, De l'Aune, & Watkins, 2006). This research has predominantly been with adults with AMD and the use of the trained retinal locus to improve reading performance. The need for such training has been debated in the literature. Nilsson et al. (1998, 2003) advocated the advantages of providing training in eccentric viewing, whereas other authors have reported that research has not yet supported the use of such training (Fletcher, Schuchard, & Watson, 1999; Schuchard, 2005). There is some support for the use of training an eccentric locus to increase the stability of fixation, but it is not clear whether this training is successful because it raises awareness of the preferred retinal locus or if a new trained retinal locus has been developed (Crossland, Culham, & Rubin, 2004; Schuchard, 2005). Research has demonstrated that there is an exponential decrease in visual acuity with eccentricity from the fovea (Davson, 1990). Logically, the closer an eccentric viewing locus is to the nonfunctional fovea, whether a preferred retinal locus or a trained retinal locus, the better the potential visual outcome. The evidence to date is not clear that the spontaneous development of the preferred retinal locus that is associated with the loss of macula vision inevitably provides the best potential acuity. Eccentric viewing is predominantly discussed in relation to reading, but some researchers have noted the application of eccentric viewing to enhance the performance of activities of daily living (ADL) (Fitzmaurice et al. …

Concordant eye movement and motion parallax asymmetries in esotropia

The role of eye movements in the perception of depth from motion was investigated in esotropia. Elevated motion parallax thresholds have been shown in strabismus [Thompson, A. M., & Nawrot, M. (1999). Abnormal depth perception from motion parallax in amblyopic observers. Vision Research, 39, 1407–1413] suggesting a global deficit in depth perception involving both stereopsis and motion. However, this motion parallax deficit in strabismus might be better explained by the role that eye movements play in motion parallax [Nawrot, M., & Joyce, L. (2006). The pursuit theory of motion parallax. Vision Research, 46, 4709–4725]. Esotropia is associated with asymmetric pursuit and optokinetic response eye movements [Demer, J. L., & von Noorden, G. K. (1988). Optokinetic asymmetry in esotropia. Journal of Pediatric Ophthalmology and Strabismus, 25, 286–292; Schor, C. M., & Levi, D. M. (1980). Disturbances of small-field horizontal and vertical optokinetic nystagmus in amblyopia. Investigative Ophthalmology and Visual Science, 19, 851–864; Tychsen, L., & Lisberger, S. G. (1986). Maldevelopment of visual motion processing in humans who had strabismus with onset in infancy. The Journal of Neuroscience, 6, 2495–2508; [Westall, C. A., Eizenman, M., Kraft, S. P., Panton, C. M., Chatterjee, S., & Sigesmund, D. (1998). Cortical binocularity and monocular optokinetic asymmetry in early-onset esotropia. Investigative Ophthalmology and Visual Science, 39, 1352–1360.]. The first experiment demonstrates that the motion parallax deficit in esotropia mirrors the pursuit eye movement asymmetry: in the direction of normal pursuit, esotropic observers had normal depth from motion parallax. A second set of experiments, conducted in normal observers, demonstrates that this motion parallax deficit is not a secondary problem due to the retinal slip created by inadequate pursuit. These results underscore the role of pursuit eye movements in the perception of depth from motion parallax.

Earlier German and Scandinavian studies on postural tachycardia syndrome (PoTS)

The concept of postural tachycardia syndrome (PoTS), characterized by excessive orthostatic tachycardia and various asthenic symptoms, including general fatigue, dizziness, headache etc., was proposed in the 1990s in North America. However, there are numerous descriptions of PoTS in earlier German, Scandinavian and Japanese literature. To provide a better understanding for the concept, we made a historical review on PoTS. In Germany, von Noorden (1893) observed that vagal neurosis, attacks of bradycardia, arrhythmia and nausea in persons with hysterical character, were caused by a centrally-mediated increase in vagal activity. Vagal neurosis corresponds to the present neurally mediated syncope (NMS), which was first referred to as vasovagal attack in English literature in 1913. Rosenbach (1897) claimed that attacks of vagal neurosis were usually preceded by tachycardia, which was not simply explained by increased vagal activity. This is considered the first description of the coexistence of NMS and PoTS. Von Bergmann (1936) used the term of vegetative stigmatization to refer to all cases of autonomic imbalance, stating that both vagal and sympathetic activities were increased. Autonomic failure, in which both vagal and sympathetic activities were decreased, had not been widely recognized at that age. In Sweden, Bjure and Laurell (1927) defined asthenic symptoms of autonomic imbalance as arterial orthostatic anemia (AOA). They measured heart rate and cardiac output in AOA cases in the supine position, the free erect position, and the erect position with the lower body immersed in water. Heart rate increased and cardiac output decreased in the free erect position, but immersion in water prevented these cardiovascular changes, as well as the appearance of asthenic symptoms. Bjure and Laurell concluded that the primary cause of AOA was excessive blood pooling in the lower part of the body. Akesson (1936) showed sympathetic overactivity in AOA, suggesting a primary lesion within venous structures. The concept of AOA was then introduced in Germany, where it was renamed orthostatic dysregulation. In his animal experiments, Mellander (1960) demonstrated that low-grade sympathetic stimulation induced venous constriction rather than arterial constriction to prevent blood pooling in vein, while high-grade sympathetic stimulation provoked strong arterial constriction to translocate blood from arteries to veins, resulting in venous pooling. In consideration of these historical studies, we hypothesize that PoTS is caused by autonomic imbalance of central origin, which likely induces venous pooling through an excessive unloading of the cardiopulmonary baroreflex.

Strabismus surgery basic and advanced strategies

This is a multiauthor book written by four well-known paediatric ophthalmologists with invited contributions from two internationally renowned strabismus surgeons, Marshall M Parks and Gunter K von Noorden. It is of medium length (194 pages) and is divided into eight chapters (Esotropic Deviations, Exotropic Deviations, Oblique Muscle Dysfunction, Dissociated Deviations, Paralytic Strabismus, Restrictive Strabismus, Nystagmus Surgery, Re-operation Strategies).

Probing the causes of visual acuity loss in patients diagnosed with functional amblyopia

Although amblyopia is normally defined as a deficit invisual acuity despite full optical correction and theabsence of observable pathology, the association be-tween ocular pathology in early life and amblyopicvisual loss is well established. For example, the presenceof monocular congenital cataract (von Noorden andMaumenee, 1968; von Noorden, 1981), unilateral ptosis(Anderson and Baumgartner, 1980; Harrad et al., 1988)or a wide variety of unilateral ocular pathologies presentduring early childhood (Kushner, 1981, 1984) canprecipitate often severe (deep) cases of amblyopia. Thesestudies provide strong support for the view that aunilateral decrease in the signal emerging from one eyebecause of patching or pathology during a sensitiveperiod early in life will precipitate a functional ambly-opia (Hardesty, 1959; Awaya et al., 1973; von Noorden,1981). In cases where the pathology cannot be resolvedthe total visual deficit reflects the combination of theprimary (organic) visual loss together with a super-imposed functional amblyopia. Recently, it has beensuggested that the visual deficit in many cases of themuch milder and more common forms of amblyopiamay also represent the sum of functional and organiccomponents (Lempert, 2000, 2003, 2004). That is, theamblyopia typically associated with strabismus and/oranisometropia, and considered to exist in the absence oforganic causes, may, in fact, be superimposed upon theloss which is due to a subtle organic defect. Thishypothesis clearly contradicts the generally held viewthat almost all amblyopias are caused by either strabis-mus or anisometropia in the absence of ocular patho-logy. This controversial hypothesis has prompted us tore-examine the traditional view of the causal agents formost amblyopias, and the implications for remediationof this condition.The vast majority of the 2–2.5% (von Noorden, 1996)ofhumansdiagnosedwithamblyopiaeitherhave,orhavepreviously had, strabismus and/or anisometropia. Theabsenceofclinically-detectedpathology,coupledwiththefact that experimentally induced anisometropia andstrabismusinanimalscausebroadlysimilarvisualdeficits(e.g. Harwerth et al., 1983; Smith et al., 1985), has led tothe ubiquitous terms anisometropic and strabismicamblyopia – with the resultant implication of a directcausalrelationship.Thatis,currentclinicaldogmaassertsthat chronic abnormal sensory input because of strabis-mus or anisometropia precipitates a neural deficit that ismanifest clinically as reduced monocular visual acuity.Improvement in visual acuity after treatment consistingonly of manipulation of sensory input (e.g. spectaclesand/or occlusion therapy) can be viewed as a formalconfirmation of the functional amblyopia diagnosis.Although the association between amblyopia andanisometropia and/or strabismus is clear, there has longbeen uncertainty regarding the causal relationshipsbetween anisometropia and strabismus and amblyopiain humans. The causal relationship is self-evident inlongitudinal animal studies in which either strabismus oranisometropia have been shown to precipitate ambly-opia (e.g. Kiorpes and Boothe, 1980; Harwerth et al.,1983; Smith et al., 1985). Furthermore, studies ofhuman infantile esotropia show that esotropia precedesthe development of amblyopia (Birch and Stager, 1985).Unfortunately, such longitudinal studies are rare in thehuman amblyopia literature. In addition to the absenceof definitive longitudinal data from human amblyopes,there are many experimental results that suggest a quitedifferent causal relationship between amblyopia andstrabismus or anisometropia. For example, althoughanimal investigations show that sustained, unilateralblurring is required to precipitate amblyopia (Smithet al., 1985), longitudinal refractive studies of human

New Orleans Academy of Ophthalmology: At the Crossings: Pediatric Ophthalmology and Strabismus

R. J. Balkan, G. S. Ellis Jr and H. S. Eustis (editors) New Orleans Academy of Ophthalmology: At the Crossings: Pediatric Ophthalmology and Strabismus 313 pages, 131 figures Kugler Publications, The Hague, 2004 ISBN: 90 6299198 x Price: €105.00/$125.00 This book consists of the proceedings of the 52nd Annual Symposium of the New Orleans Academy of Ophthalmology, held in New Orleans in February 2003. Unique to this meeting was the participation of three legendary figures within the world of paediatric ophthalmology and strabismus, namely Marshall Parks, Arthur Jampolsky and Gunter von Noorden. The rest of the list of distinguished speakers at this meeting was also impressive and several of them gave multiple presentations on their particular area. The book is divided into three sections consisting of updates on cataract and refractive issues, amblyopia and strabismus, and oculoplastics. Each section concludes with a round table discussion with the experts in the field and a short question and answer section. The text is beautifully illustrated with many high quality colour photographs and line drawings and all chapters seem well referenced. The presentations respond to both basic questions, such as the aetiology of dissociated verticle deviation (DVD), as well as basic clinical questions, such as how to deal with childhood ptosis. I found the book very interesting and, although it might not end up on every paediatric ophthalmologist's bookshelf, I think it merits a place in the clinic library.

Carotenoderma--a review of the current literature.

Carotenoderma--a review of the current literature.