Gunnar Lennerstrand

Screening for visual and ocular disorders in children, evaluation of the system in Sweden

The aim of this study was to evaluate the visual screening system in Sweden. We have made a retrospective investigation of the results of screening for ocular disease and visual impairment of all children born in 1982 in three Swedish communities. The records from screening examinations from 0 to 10 y and from diagnostic follow‐up at the departments of ophthalmology that the children were referred to were inspected. The data were used to evaluate the efficiency of the Swedish visual screening system. The study included 3126 children. The attendance rate at the 4‐y examination was better than 99%. The sensitivity of the 4‐ and 5.5‐y screening examinations was on the average 92% and the specificity was 97%. The average number of false negative cases at 4 y was 5.6 in 1000 (0.56%). With this screening and subsequent diagnosis and treatment, the prevalence of amblyopia at different levels of visual acuity at the age of 10 y was: 0.06% with visual acuity <0.1,0.9% with visual acuity <0.5 and 1.7% with visual acuity < 0.7. In spite of largely unchanged pressure of amblyogenic factors in the population, the prevalence of deep and moderate amblyopia has been markedly reduced by screening and early treatment.

Reduced activity in the extrastriate visual cortex of individuals with strabismic amblyopia

In order to examine the relationship between reduced visual acuity in human strabismic amblyopia and the cortical activation pattern, we studied, by use of positron emission tomography (PET) and the H2(15)O bolus technique, changes in the regional cerebral blood flow (rCBF) induced by monocular visual stimulation of 8 individuals with this disorder. Individual amblyopic thresholds for monocular detection of the checkerboard pattern were employed as stimuli for both eyes during PET scans. Statistical analysis of subtracted images showed significant increases in rCBF (P < 0.05) by the stimulation of the sound eye localized bilaterally to Brodmanns areas (BAs) 17-19. The cortical response evoked by the amblyopic eye was significantly reduced (P < 0.05) in the ipsilateral BAs 18, 19. These results suggest that the reduction in contrast sensitivity (pattern vision) in amblyopia is coupled with deactivation in identifiable regions of occipital visual areas, including ipsilateral BAs 18,19.

MRI measurements of normal extraocular muscles and other orbital structures.

Abstract Background: Studies of extraocular muscle (EOM) by magnetic resonance imaging (MRI) need to be extended to normal subjects of different ages to obtain data on the muscle thickness, cross-sectional area, and the volume of EOM and other orbital tissues. Methods: Forty-two orbits of 21 normal subjects in three age groups with an age range of 19–70 years were examined with surface-coil MRI. The transverse and sagittal images were used to measure the thickness of the four rectus muscles during fixation in different gaze positions. The coronal images with eyes in the primary position were used to calculate the cross-sectional areas. The volumes of all six EOM, orbital fatty tissue, the optic nerve and the eyeball were measured in the coronal plane and in either the transverse or the sagittal plane. Results: The horizontal muscles were thinner than vertical muscles. Muscle volume was larger in SR (superior rectus) than in IR (inferior rectus), larger in SO (superior oblique) than in IO (inferior oblique), and the same in LR (lateral rectus) as in MR (medial rectus). No significant differences were found in the values of the cross-sectional area in any image plane between the three age groups. There were no significant differences in muscle thickness and size and fatty tissue volume between age groups. The muscle thickness was linearly correlated to the angle of the eye deviation for all four rectus muscles, both in the ”on” and ”off” directions of the muscles. Conclusions: The study provides quantitative data, in normal subjects of different ages, on the thickness and size of EOM and the volume of other orbital tissues by MRI, to serve as a basis for further studies on the morphological changes of EOM in various orbital diseases.

Eye proprioception and visual localization in humans: Influence of ocular dominance and visual context

It has been previously established that the application of low amplitude mechanical vibrations to the inferior rectus muscle of human subjects results in an illusory upward movement of a luminous spot fixated in total darkness, and in a corresponding overshooting of the target when the subject is asked to point to this spot. In the first experiment described here, we compared the effects of applying vibrations to each eye separately and to both eyes simultaneously, under monocular and binocular viewing conditions, in left- and right-eyed subjects. The results confirmed that proprioceptive signals arising from both eyes are involved in egocentric visual localization. A proprioceptive dominance was observed however since vibration of the dominant eye gave rise to larger pointing displacements. In addition, whichever eye was stimulated, the pointing shift induced by vibrating a covered eye was of smaller amplitude than that which occurred when vibrations were applied to the viewing eye. The second experiment showed that both the vibration induced illusions and the pointing shifts disappeared in a structured visual context, which suggests that the processes involved when the target is viewed in darkness might differ from those occurring in structured surroundings.

Contrast sensitivity in macular degeneration and the relation to subjective visual impairment

Abstract Contrast sensitivity was determined with electronic and computer equipment (Cadwell CTS 5000) and with optotype test charts (LH low contrast test) in 31 patients, aged 47–89, with macular degeneration, mostly of the age‐related type. Values of maximal sensitivity and mean sensitivity in different spatial frequency bands were estimated. Visual acuity at distance and the magnification factor needed for reading were also determined. Each of these measures were correlated with a score obtained in a subjective evaluation of difficulties with visual discrimination and orientation. It was found that poor visual discrimination and orientation was better correlated with low contrast sensitivity than with low visual acuity. The outcome of the LH‐test was a better predictor of orientation problems than the electronic test.

Effect of eyelid botulinum toxin injection on lacrimal drainage.

PURPOSE To determine the effect of eyelid botulinum toxin injection on the lacrimal drainage and to assess the use of botulinum toxin in dry eye conditions. METHODS Prospectively, three test groups were examined and one lacrimal system investigated in each person in each group. Botulinum toxin A (3.75 IU) was injected into the medial part of 13 lower eyelids of 13 normal test subjects and the medial part of nine lower eyelids in nine patients with dry eyes. A dose of 2.5 IU was injected into the medial part of 10 lower eyelids and the medial part of 10 upper eyelids of 10 patients with dry eyes. The drop test was used to determine the lacrimal drainage capacity and the blink output, before and after the injection. The subjective effect of the botulinum toxin injection on eye comfort was investigated. RESULTS Three weeks after lower eyelid botulinum toxin injection, the mean blink output was reduced to 64% (1.19 of 1.87; P <.001) and 70% (0.94 of 1.35; P <.001) of the baseline values in the groups of normal subjects and patients, respectively. After injection in both the upper and lower eyelid, the mean blink output was reduced to 38% (0.54 of 1.41; P <.001) of the baseline value. The patients with dry eyes reported an improved eye comfort in six of nine cases after injection in the lower eyelid and in seven of 10 cases after injection in both the upper and lower eyelid. Adverse effects included one case of increased discomfort for 3 weeks after injection. CONCLUSION Injection of botulinum toxin into the medial part of the eyelids decreased the lacrimal drainage, suggesting a new way to treat dry eye conditions. Further studies are required to assess the clinical value of this treatment.

Changes in conceptions of meaning, effects and treatment of amblyopia. A phenomenographic analysis of interview data from parents of amblyopic children

The research reported is an experimental study on the effects of intensified education of parents of children with amblyopia on their understanding of the nature of the defect, its origins and treatment. Parents in the control group were exposed to the ordinary information provided at two departments of paediatric ophthalmology, whereas parents in the experimental group, attending the same clinics, were asked to read a booklet aiming at enhancing their understanding of amblyopia and its treatment. Experimental as well as control subjects were thereafter interviewed about their understanding of the meaning of amblyopia and amblyopia-related phenomena. Data were generated in single subject, semi-structured, in-depth interviews which were taped and transcribed in extenso. The interviews were analyzed according to the phenomenographic approach: i.e. the outcome is a description of the various conceptions that emerged in the interviews. In almost all cases the categories of meaning could be hierarchically ordered with regard to the level of understanding implied. Parallel to the interviews the subjects had also filled out a questionnaire assessing general and specific attitudes towards disease and treatment (the Health Belief Model, HBM). The results reveal a superior understanding among parents in the experimental group. The experimental group had also changed attitudes towards disease and treatment in a direction that would favour compliance, more than could be observed in the control group. The outcome is discussed in terms of the role of understanding for a compliant behaviour. It is also emphasised that health care personnel would profit from being aware of the nature of common misconceptions of diseases and their treatment, in the sense that they would be better prepared for entering instructional dialogues with patients or, as in this case, other persons responsible for the management of prescriptions provided.

Visual functions in a Swedish population of dyslexic and normally reading children

Abstract Eighty‐six 9‐year old dyslexic children were carefully matched to controls with regard to age, sex, class in school, and intelligence and thorough visual functions tests and eye examinations were performed. As a group the dyslexic pupils exhibited a lower distance as well as near visual acuity both with monocular and binocular viewing. Furthermore, the dyslexic pupils had a lower contrast sensitivity at the lower and higher spatial frequencies. These differences were all statistically significant. However, no statistically significant differences between the two groups could be observed regarding refractive errors or contrast sensitivity in the middle spatial frequency range. Although some eyes were amblyopic, any severe eye anomalies or diseases were not found in any of the investigated children.

NEURO‐OPHTHALMOLOGICAL FINDINGS IN RELATION TO CNS LESIONS IN PATIENTS WITH MYELOMENINCOCELE

Twenty‐eight patients (14 male, 14 female; aged four to 34 years) with myelomeningocele were studied. Magnetic resonance imaging was used to determine the correlation between disturbances of ocular motility and the degree of hydrocephalus, tectal plate deformity and dislocation of the cerebellum and medulla oblongata. All patients had Chiari malformations. Strabismus and spontaneous nystagmus were strongly related mainly to the degree of hydrocephalus and to some extent to the amount of lower brainstem deformities. Ocular motility defects with regard to oblique muscle functions and horizontal and vertical gaze and saccadic control often correlated with lower brainstem lesions. Convergence defects correlated with deformities of the upper brainstem. However, these correlations were not valid in the individual patient; some had no strabismus and normal ocular motility, in spite of advanced hydrocephalus and Chiari malformations.

NEURO-OPHTHALMOLOGICAL EVALUATION OF PATIENTS WITH MYELOMENINGOCELE AND CHIARI MALFORMATIONS

Twenty‐eight patients (14 females and 14 males aged between four and 34 years) with myelomeningocele and Chiari malformations were examined neuro‐ophthalmologically. All patients had been under proper neurosurgical care and no reduction of visual function was found that could be related to optic atrophy or other changes in the visual pathways. However, ocular motility disorders, including strabismus, were common, although no case of down‐beat nystagmus was observed. Manifest strabismus was found in 11 patients. Esotropia with or without A‐pattern was seen in nine patients. Spontaneous or gaze‐related nystagmus and abnormal optokinetic nystagmus represented the most common disturbances of ocular motility. Abnormalities of horizontal eye‐movements were more common than those of vertical eye‐movements. Strabismus of the manifest type was combined with other ocular motility disturbances in most cases.