Inappropriate prescription of prism glasses for obligate fixation disparity measured with the Pola test

In the subjective measurement of fixation disparity (FD), the subject sees and fuses contours presented in the peripheral macular areas of both eyes ('fusion loek', a square for instanee). The pointing direction of the foveolae of both eyes relative to each other is determined by means of two haploscopically seen objects presented in the central visual field (Fig. la). ..

Costs and methods of preventive visual screening and the relation between esotropia and increasing hypermetropia

Atkinson has shown that early correction of hypermetropia reduces the incidence of esotropia. If esotropia is reduced by prescribing glasses early, the rate of esotropia-induced amblyopia can be similarly reduced; this would have important economic consequences. We have studied (1) how costs compare to benefits in early visual screening, (2) how videorefraction as used by Atkinson compares to retinoscopy, and (3) whether esotropia is more likely to occur in children who have increasing as opposed to decreasing hypermetropia. The costs of the study so far have been high. It was exceedingly difficult to get all infants invited, come to the clinic and examined. Videorefraction did not compare favourably with retinoscopy in terms of costs and precision, whereas the amount of skill and time needed was approximately equal. The third question, whether esotropia is more likely to occur in children who have increasing as opposed to decreasing hypermetropia, arose from the controversy whether, in the general population, refraction increases or decreases during the first years of life. We found that papers reporting a decrease of hypermetropia in early childhood were studies of large cross-sections of the general population, whereas papers that reported an initial increase originated from ophthalmological practices or strabismus departments. These conflicting results could be reconciled by assuming a population bias: if esotropia is more likely to occur in children with increasing hypermetropia, children with increasing hypermetropia will preferentially be seen by ophthalmologists. It seems natural that children with increasing hypermetropia are more likely to squint, because additional accommodation, needed to overcome increasing hypermetropia, will inevitably confer additional convergence. This relationship has meanwhile been confirmed by others

Analysis of the dosage controversy in recess-resect and Faden surgery with the Robinson computer model of eye movements

In recess-resect surgery, the dosage depends on the preoperative angle of squint and on the ratio between squint-angle reduction and dosage that the surgeon has found in previous surgery. Recommendations pertaining to this ratio vary widely among authors. Some say a recession does more than a resection, while others believe the opposite is true. Finally, most find a lower ratio at smaller preoperative angles of squint. We investigated the matter, using our modified version of the Robinson computer model of eye movements. We calculated the amounts of surgery needed to reduce 10, 15, 20, 25 and 30 degree angles of squint to zero. The increase of the ratio at large angles of squint was indeed predicted by the model. The decrease at small angles of squint, however, was not predicted by the model. We found it impossible to model the decrease of the ratio at small preoperative angles of squint. The ratios for recess and resect surgery were approximately similar. We present an inventory of the possible causes of the discrepancies. In addition, we calculated the effects of Faden surgery and found that the predictions of the computer model correspond closely to reality

Length-tension curves of human eye muscles during succinylcholine-induced contraction

We have made intraoperative, continuous-registration, length-tension diagrams of detached eye muscles in 80 strabismus patients under general anaesthesia. In 47 of these we repeated the measurements after contraction evoked by succinylcholine chloride. In contracting horizontal and vertical rectus muscles, we found a linear relation between length and tension. In contracting oblique muscles, however, the relation between length and tension was frequently nonlinear. In superior oblique palsies, the superior oblique was found to be stiff after elongation and before injection of succinylcholine, and it did not contract after injection of succinylcholine. The ipsilateral inferior oblique did contract after injection of succinylcholine, but with a higher spring constant than usual (ie, contracture of the ipsilateral antagonist). In three cases the superior oblique contracted vividly after administration of succinylcholine despite the presence of excyclotropia, stereopsis, torticollis (two cases) and a hypertropia that increased in adduction, in down-gaze, in adduction and down-gaze and on ipsilateral head-tilt. In a case of general fibrosis syndrom we found almost normally contracting vertical recti, which is compatible only with a supranuclear or misdirectional cause. These cases demonstrate the usefulness of the assessment of the length-tension diagram of an eye muscle during surgery, before and during contraction evoked by succinylcholine chloride

Force-length recording of eye muscles during local-anesthesia surgery in 32 strabismus patients

Abstract. Force-length recordings were made from isolated human eye muscles during strabismus surgery in local, eye-drop anesthesia in 32 adult patients. From each muscle three recordings were made: (1) while the patient looked with the other eye into the field of action of the recorded muscle, (2) looked ahead, and (3) looked out of the field of action of the recorded muscle. Non-innervated eye muscles (state 3) had an approximately exponential relation between force and length. During contraction evoked by letting the patient look ahead or into the field of action of the muscle (states I or 2), the relation between force and length was grossly linear. The approximate spring constants of horizontal rectus muscles that had not been operated on before ranged from 2 to 4 g/mm. In palsies, the degree of muscle paresis could be quantified accurately using this method and, accordingly, cases of true superior oblique palsy could be well differentiated from strabismus sursoadductorius (= upshoot in adduction) that may mimic a superior oblique palsy. In seven patients with Graves' disease of recent onset, affected muscles were found to be very stiff when the other eye looked ahead. It was expected that these stiff muscles would be able to shorten to some extent but would not be able to lengthen, due to fibrosis of the muscle. We found, however, that the affected muscles lengthened considerably when the other eye looked out of the field of action of the muscle. This implies that, in these cases of Graves' disease of recent onset, the raised muscle tension and reduced elasticity of the affected muscles and, hence, the strabismus were primarily caused by active muscle contraction, not by fibrosis

Intraoperative length and tension curves of human eye muscles. Including stiffness in passive horizontal eye movement in awake volunteers

Intraoperative continuous-registration length and tension curves of attached and detached eye muscles were made in 18 strabismic patients under general anesthesia. For relaxed eye muscles, we found an exponential relation between length and tension. An increased stiffness was quantified in Duane's syndrome, Graves' disease, orbital-floor fracture, and superior oblique palsy. The stiffnesses of agonist and antagonist were remarkably similar, not only in uncomplicated squint, but also when only one of the two had initially become stiffer. After intravenous administration of succinylcholine chloride, the eye muscles contracted, and the exponential length and tension curve changed into a set of straight, parallel lines. In addition, we measured stiffness in passive horizontal eye movement in awake volunteers and found 0.52 to 1.26 g/degrees (other eye in 5° of adduction), confirming other published results

Kearns-Sayre's syndrome developing in a boy who survived Pearson's syndrome caused by mitochondrial DNA deletion

Documenta Ophthalmologica 1992, Volume 82, Issue 1-2, pp 73-79 Kearns-Sayre's syndrome developing in a boy who survived Pearson's syndrome caused by mitochondrial DNA deletion Dr H. J. Simonsz, K. Bärlocher, A. Rötig … show all 3 hide » Download PDF (2,322 KB) Abstract A 7-year-old boy presented with bilateral ptosis and atypical retinitis pigmentosa. Before age two, he had had an Fe-refractory anemia, with neutropenia and thrombopenia. Just prior to the ophthalmic examination, the patient developed lactate acidosis, muscular hypotonia, ataxia and increased protein in the spinal fluid. Pancytopenia, pancreas dysfunction and growth retardation are the main features of Pearson's syndrome, most children not surviving beyond age three. The cause of Pearson's syndrome in our patient turned out to be a 5 kb deletion in the mitchondrial DNA. Similar deletions have been described in the Kearns-Sayre syndrome. It seems that children who survive the initial phase of Pearson's syndrome, may develop Kearns-Sayre syndrome

Digitisation and 3D reconstruction of 30 year old microscopic sections of human embryo, foetus and orbit

A collection of 2200 microscopic sections was recently recovered at the Netherlands Ophthalmic Research Institute and the Department of Anatomy and Embryology of the Academic Medical Centre in Amsterdam. The sections were created thirty years ago and constitute the largest and most detailed study of human orbital anatomy to date. In order to preserve the collection, it was digitised. This paper documents a practical approach to the automatic reconstruction of a 3- D representation of the original objects from the digitised sections. To illustrate the results of our approach, we show a multi-planar reconstruction and a 3-D direct volume rendering of a reconstructed foetal head

Long-term follow-up of an amblyopia treatment study: change in visual acuity 15 years after occlusion therapy

Purpose: To determine change in visual acuity (VA) in the population of a previous amblyopia treatment study (Loudon 2006) and assess risk factors for VA decrease. Methods: Subjects treated between 2001 and 2003 were contacted between December 2015 and July 2017. Orthoptic examination was conducted under controlled circumstances and included subjective refraction, best corrected VA, reading acuity, binocular vision, retinal fixation, cover-uncover and alternating cover test. As a measure for degree of amblyopia, InterOcular VA Difference (IOD) at the end of occlusion therapy was compared with IOD at the follow-up examination using Wilcoxon’s signed-rank test. Regression analysis was conducted to determine the influence of clinical and socio-economic factors on changes in IOD. Results: Out of 303 subjects from the original study, 208 were contacted successfully, 59 refused and 15 were excluded because of non-amblyopic cause of visual impairment. Mean IOD at end of therapy (mean age 6.4 years) was 0.11 ± 0.16 logMAR, and IOD at follow-up examination (mean age 18.3 years) was 0.09 ± 0.21 logMAR; this difference was not significant (p = 0.054). Degree of anisometropia (p = 0.008; univariable analysis), increasing anisometropia (p = 0.009; multivariable), eccentric fixation (p < 0.001; univariable and multivariable); large IOD (p < 0.001; univariable and multivariable) and non-compliance during therapy (p = 0.028; univariable) were associated with IOD increase. Conclusion: Long-term results of occlusion therapy were good. High or increasing anisometropia, eccentric fixation and non-compliance during occlusion therapy were associated with long-term VA decrease. Subjects with poor initial VA had a larger increase despite little patching, but often showed long-term VA decrease

Preoperative prism adaptation test in normosensoric strabismus

In 19 patients with normosensoric esotropia, the squint angles measured with the alternate cover test were compared with those after prolonged prismatic correction of the squint angle and with those after prolonged occlusion of one eye. All patients showed an increase of the squint angle after prism adaptation. The angle was generally smaller after diagnostic occlusion of one eye than after prism adaptation. We assume that the increase in the squint angle after prism adaptation is caused by an anomalous sensorial relationship between the two eyes that was not detected with the usual psychophysical tests. Surgery tailored to the squint angle after prism adaptation seems advisable in patients with normosensoric esotropia