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Biomedical subjects

G Lennerstrand

Publications and source records attributed to G Lennerstrand.

At least 37 records · Page 2Linked to original sources
PubMed1995

Eye movements in normal subjects induced by vibratory activation of neck muscle proprioceptors.

Versional eye movements, induced by neck muscle vibration at 70 Hz in 8 normal subjects, were recorded with infrared reflection technique in each eye separately with one eye fixating a target and the other covered. The direction of eye movements was horizontal when the sternocleidomastoid muscle on one side of the neck and the splenius on the other side were activated, and downward when both splenii muscles were vibrated. The direction was the same as that of the illusory movements of the target also induced by the vibration. These findings would imply that the proprioceptive messages originating in the neck muscles are processed together with visual information of eye position in determining gaze direction.

Eye Movements↗
PubMed1995

Screening for ocular dysfunction in children: approaching a common program.

According to the general principles of screening, detection of visual impairment in children is worthwhile, since the condition is a serious health problem, reliable diagnostic tests are available and effective treatment is possible in most instances of ocular and visual dysfunction. However, an evaluation of the screening procedures has not been properly done and the cost-benefit of screening has not been studied. The aim of the present study is to perform a systematic analysis of the screening programs for detection of visual dysfunction. In the screening two parts can be separated, one that concerns the more serious ocular and visual conditions which have to be discovered by general survey methods very early in life, and one that involves detection of less serious conditions, mainly amblyopia, which can be diagnosed by testing for monocular reduction of visual acuity at about 3-4 years of age. The performance characteristics of the screening programs used in Sweden and Canada were evaluated and found to be very favourable. Based on the analysis and the evaluation, recommendations are made on programs for vision screening in children that could be applied more widely. The program could involve all or parts of the following: 1) A careful inspection of the eyes in the neonatal period and preferably also examination of the red reflex with the ophthalmoscope. 2) Children at high risk for ocular and visual disorder, i.e. those born prematurely before 32 weeks of age, or with genetic disease, hearing deficit and/or neurological and mental disorder, should be examined at the proper age by an ophthalmologist. 3) All staff at pediatric departments and child health care centers should be familiar with the visual development of the normal baby and should be alerted to the various symptoms and signs which first warn parents that there may be a visual defect. An inspection of the eyes to detect squint should be part of all pediatric examinations. 4) A screening test of monocular visual acuity in 4 year-old children can be reliably performed by non-ophthalmic personnel after proper training. The screening test should be repeated by school nurses during the first grade of school, and at regular intervals during the school years. 5) The children that screen positively should be seen by ophthalmologists, and in some cases by orthoptists, without undue delay for diagnosis and treatment.

Child↗
PubMed1994

Vertical saccadic velocity and force development in superior oblique palsy.

Vertical saccadic movements recorded with electrooculography (EOG) and force development measured by means of a contact lens-strain gauge technique were investigated in 13 patients with a clinical diagnosis of unilateral superior oblique palsy (SOP) and 10 normal subjects. Upward and downward movements from the horizontal level to 5, 10 and 20 deg of deviation with monocular fixation were made in the 20 deg abduction and adduction fields of gaze. Peak velocity (Vp) and the ratio of downward over upward movement (VpD/U) of the paretic eye (PE) and the sound eye (SE) of the patients were compared with the values of the covered, non-fixating eye (CE) and the fixating eye (FE) of the normals respectively. Peak tension (Fp), steady-state tension (Fs) and the ratios of downward over upward movement (Fp D/U, Fs D/U) of PE were compared with the values of CE. Comparisons were done (a) between normals and the whole group of 13 patients, (b) between normals and two subgroups of five patients with acquired and five with congenital SOP, (c) and between the subgroups. Mean Vp for the whole group of SOP showed reduced values from normals in many directions of gaze. However, mean Fp and ratios of Vp D/U and Fp D/U were not different in SOP and normals, and such measures could not be used to differentiate SOP from normal eye muscles in the sample of patients studied. Clear differences were seen in the comparisons between normals and the subtypes of SOP. Vp was significantly reduced in PE for the downward movements in the adduction field of gaze, more marked in acquired than in congenital SOP. Slowing of upward saccades was also found in the congenital group. This may be due to adaptational changes in concomitization of congenital paretic strabismus. Fp for downward saccade, and Vp D/U and Fp D/U were lower for PE in the acquired than in congenital SOP and normals in the lower adduction field of gaze, where the superior oblique has its main action. A linear relation was found between Vp and Fp of downward saccades for the congenital group in the lower adduction of gaze, but the slope was steeper than in normals. However, in acquired SOP the relationship was non-linear, which indicates a force production different from that of a normal muscle. Vertical saccadic velocity and force development measured at 20 deg adduction could reveal weakness of the superior oblique muscle and the imbalance of agonist-antagonist actions in the paretic eye.(ABSTRACT TRUNCATED AT 400 WORDS)

Adult↗
PubMed1994

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.

Eye Movements↗
PubMed1993

Regressed retinopathy of prematurity in children aged 5-10 years.

Regressed retinopathy of prematurity (ROP) and its sequelae has been analysed in pre-term born children with a birth weight < 1500 g and/or < 33 weeks of gestational age, born in Stockholm during 1976-81. At the age of 5-10 years, we found that 134 of 528 preterm born children (25.4%) had been at departments of ophthalmology in Stockholm for various reasons. These children were re-examined and a good eye fundus information could be obtained in 105. Moderate and severe regressed ROP was found in 48 and 13 children, respectively. In the Stockholm area the frequency of children with severe ROP (earlier called cicatricial ROP) was 2.5% out of the above risk group of 528. Two children were blind from ROP (0.4%). Ten children had a visual acuity < or = 0.3 in the worse eye (1.9%) and 7 of them had ROP changes. Children with a birth weight < 1000 g had the highest frequency of ROP (severe 11.6% and moderate 18.6%) and ocular complications. The results show that preterm born children often present ocular complications, and therefore they need a close follow-up.

Blindness↗
PubMed1993

Epidemiology of ROP in the Stockholm area of Sweden.

A prospective, population-based study of the epidemiology of ROP in a well-defined geographical area of Sweden was performed. Two hundred and sixty children with a birth weight of 1500 g or less, and surviving for at least eight weeks, were included in the study. ROP was seen in 40.4% of the children. We suggest that prematurely born children with a gestational age of 32 weeks or less ought to be screened for ROP.

Cryosurgery↗
PubMed1993

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

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.

Child↗
PubMed1993

Oculomotor functions in a Swedish population of dyslexic and normally reading children.

Eighty-six nine-year-old dyslexic children were matched to control children with regard to age, sex, class in school, and intelligence. Orthoptic and eye movement analysis were performed on all children. It was concluded that the dyslexic pupils did not differ significantly from control children in terms of strabismus, accommodation, stereo acuity, vergence function or ocular dominance. Eye movement recordings did not show any qualitative differences between the groups in vergence dynamics during synoptophore investigations.

Accommodation, Ocular↗
PubMed1993

A population based, prospective study of the development of ROP in prematurely born children in the Stockholm area of Sweden.

A prospective population based study including 260 children with a birth weight of 1500 g or less was performed in the Stockholm county. The total incidence of retinopathy of prematurity (ROP) was 40.4%, while severe ROP--that is, stage 3 or more, was seen in 20.0%. Cryotherapy was performed in 10.8%. Logistic regression analysis revealed independent association of both gestational age and birth weight with ROP. The association of gestational age and ROP was significantly stronger, indicating that the degree of immaturity of the eye is a main predictive factor for the development of ROP. The purpose of a general screening for ROP is to identify children requiring cryotherapy. Based on these results it seems appropriate to include children with a gestational age of 32 weeks or less in such a programme and a first examination at 5-6 weeks of postnatal age is suggested.

Birth Weight↗
PubMed1992

Regressed retinopathy of prematurity: the relationship between clinical risk factors of the newborn period and regressed retinopathy of prematurity severity in a preterm born population of Stockholm county 1976-81.

In a retrospective study, clinical risk factors of the neonatal period were correlated with the severity of regressed retinopathy of prematurity (ROP) in a population of preterm infants (bw less than 1500 g and or gestational age less than 33 weeks). At the age of 5-11 years 134 out of 528 preterm born infants (25.4%) were found to be under ophthalmic care. Reliable information on eye fundus status could be obtained in 105 of them. Regressed ROP was found in 61, the moderate form in 48 (9.1%) and the severe form in 13 (2.5%) patients. Twelve patients (2.3%) had visual acuity of less than 0.3 on the worst eye and two (0.4%) of these patients were blind from ROP. Twenty-four clinical factors of the newborn period were correlated with the severity of regressed ROP. The results suggest that long oxygen exposure in combination with other factors interfering with retinal vasotonus are associated with the degree of the disease developed.

Birth Weight↗
PubMed1992

Dyslexia; ophthalmological aspects 1991.

Dyslexia or specific reading disability is an important and frequent handicap afflicting 5-10% of the population. It is basically a disorder of acquisition of written language, probably due to a poorly developed phonological awareness, which in turn may be neurologically related. As anatomical correlates symmetry of the planum temporale and ectopies in the cerebral cortex have been suggested. Functional correlates are discovered with brain electrical mapping and stimulation of brain structures during neuro surgery. From an ophthalmological point of view there are no relations between dyslexia and ocular problems including refractive errors and accommodation, problems of binocular control and stereopsis, eye dominance instability etc. However, contrast sensitivity seems to be reduced in dyslexics for the middle range of spatial frequencies, which may be related to impaired function of the 'transient' visual system. With regard to eye movements, there is no firm experimental proof for any disturbances in dyslexia, be it with the different movement systems or in the best movement direction. 'Backward saccades' or regressions are typical not only for dyslexic reading but in all types of reading when comprehension is poor. Although there is no treatment for dyslexia itself that can be based on ophthalmological findings, the ophthalmologist must after careful examination discover and treat any ocular, orthoptic or neuroophthalmological problem that may make reading difficult for the dyslexic child. The ophthalmologist must explain to the child and the parents that dyslexia usually has no ophthalmological or visual cause but is a disability with a neurobiological background, still unknown, in which the only efficient treatment is within the area of pedagogy.

Dyslexia↗
PubMed1991

A population-based study of ocular abnormalities in premature children aged 5 to 10 years.

We studied the prevalence of ocular abnormalities in 528 children born prematurely (less than 1,501-g birth weight, less than 33 weeks' gestational age, or both) in Stockholm County from 1976 to 1981. The control group consisted of 1,047 randomly selected full-term children. Through various searches of the ophthalmic records from the period of 1981 to 1986 of Stockholm County, we found that 134 of the 528 premature children (25.4%) and 121 of the 1,047 full-term children (11.5%) had needed ophthalmic care for different reasons. The prevalence of ocular abnormalities was much higher in premature children than in full-term children: reduced visual acuity of 20/33 or worse in the best eye (21 of 528 [4.0%] and one of 1,047 [0.1%]); myopia (33 of 528 [6.3%] and 18 of 1,047 [1.8%]); anisometropia of 1 diopter or greater (31 of 528 [5.9%] and 15 of 1,047 [1.5%]); strabismus (52 of 528 [9.9%] and 22 of 1,047 [2.1%]); and nystagmus (13 of 528 [2.4%] and one of 1,047 [0.1%]). Children with birth weight less than 1,000 g had the highest rates of ocular abnormalities. We conclude that visual and oculomotor development of premature children should be carefully examined.

Amblyopia↗
PubMed1991

Regressed retinopathy of prematurity and its sequelae in children aged 5-10 years.

Regressed retinopathy of prematurity (ROP) and its sequelae were studied in children born prematurely (less than 1501 g birth weight and/or less than 33 weeks gestational age) in Stockholm county during 1976-81. Through various searches of the records at the different eye departments and other sources in Stockholm county we found that 134 out of a total of 528 premature babies (25.4%) had needed ophthalmic care for different reasons. They were re-examined and reliable information on the fundus could be obtained for 105 of them. The frequency of regressed ROP was 45.5%. Severe forms with vitreoretinal scarring and retinal traction were seen in 9.7% of cases and moderate forms with pigmentary changes and/or vitreoretinal interphase changes in 35.8%. The sequelae of regressed ROP were mainly reduction of visual acuity and myopia. Children with a birth weight below 1000 g and a gestational age less than 30 weeks presented the highest rate of regressed ROP (68.5% and 61.9%) and ocular abnormalities.

Blindness↗
PubMed1990

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.

Adolescent↗
PubMed1990

Neuro-ophthalmological findings in relation to CNS lesions in patients with myelomeningocele.

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.

Adolescent↗