Accommodative Dysfunction Research Articles

Improvements in performance following optometric vision therapy in a child with dyspraxia

SS, an 8-year-old boy with dyspraxia, presented for behavioural optometry assessment. He had been diagnosed with a subtle form of dyspraxia by his paediatric occupational therapist, based on poor proprioception, delayed bilateral integration and poor visual perception. A full visual assessment was carried out. SS was given a programme of reflex inhibition exercises for 3 months. Then, a programme of optometric vision therapy (OVT) exercises was prescribed at home and in practice for a period of 8 months. SS was assessed using a battery of occupational therapy Sensory Integration and Praxis Tests (SIPT) before optometric intervention, and after OVT. There were significant improvements in fusional reserves, accommodative facility and oculomotor control of pursuit and saccadic eye movements. His reading level had changed by 4 years in 11 months. The SIPT results showed improvements in the visual and motor/visual perception subtests, confirming the significant changes in visual perceptual performance. Consideration is given to treatment modalities for dyspraxia, and the studies confirming their effectivity of approach. This case study provides evidence supporting the use of OVT eye exercises in dyspraxia, ocular motility, accommodative dysfunction, learning difficulties and sports performance. The need for further research and inter-professional working is discussed.

Measuring ADHD behaviors in children with symptomatic accommodative dysfunction or convergence insufficiency: a preliminary study

Accommodative dysfunction and convergence insufficiency (CI) are common pediatric vision problems that have been associated with an increase in frequency and severity of vision-specific symptoms that affect children when doing schoolwork. However, the relationship between accommodative dysfunction and CI and other learning problems, such as attention deficit hyperactivity disorder (ADHD), are not well understood. The purpose of this study was to evaluate the frequency of ADHD behaviors in school-aged children with symptomatic accommodative dysfunction or CI. Children 8 to 15 years of age with symptomatic accommodative dysfunction or CI were recruited from the teaching clinic at the Southern California College of Optometry. Children with learning disabilities or ADHD were excluded. One parent of each child completed the Conners Parent Rating Scale-Revised Short Form (CPRS-R:S). The children's scores on the CPRS-R:S were compared with the normative sample. Twenty-four children (9 boys and 15 girls) participated in the study with a mean age of 10.93 years (SD = 1.75). On the CPRS-R:S, cognitive problem/inattention, hyperactivity, and ADHD index were significantly different from normative values (p < or = .001 for all tests). The results from this preliminary study suggest that school-aged children with symptomatic accommodative dysfunction or CI have a higher frequency of behaviors related to school performance and attention as measured by the CPRS-R:S.

A Systematic Review of the Applicability and Efficacy of Eye Exercises

To examine the current scientific evidence base regarding the efficacy of eye exercises as used in optometric vision therapy. A search was performed of the following databases: Allied and Complementary Medicine Database, Cochrane Database of Systematic Reviews, Cochrane Register of Controlled Trials, EMBASE, and MEDLINE. Relevant articles were reviewed and analyzed for strengths and weaknesses. Pertinent sections of classic texts were studied to provide a historical basis and to serve as a source for additional early references. Forty-three refereed studies were obtained. Of these, 14 were clinical trials (10 controlled studies), 18 review articles, 2 historical articles, 1 case report, 6 editorials or letters, and 2 position statements from professional colleges. Many of the references listed by the larger reviews were unpublished or published in obscure or nonrefereed sources and therefore were not accessible. Eye exercises have been purported to improve a wide range of conditions including vergence problems, ocular motility disorders, accommodative dysfunction, amblyopia, learning disabilities, dyslexia, asthenopia, myopia, motion sickness, sports performance, stereopsis, visual field defects, visual acuity, and general well-being. Small controlled trials and a large number of cases support the treatment of convergence insufficiency. Less robust, but believable, evidence indicates visual training may be useful in developing fine stereoscopic skills and improving visual field remnants after brain damage. As yet there is no clear scientific evidence published in the mainstream literature supporting the use of eye exercises in the remainder of the areas reviewed, and their use therefore remains controversial.

What are the visual benefits of eyelid squinting?

We propose that eyelid squint can reduce the impact of several conditions known to cause eyestrain such as uncorrected refractive error, accommodative dysfunction, presbyopia, and glare. Clinicians commonly accept that squint improves visual acuity (VA) in the presence of refractive error, and even though the benefit of eyelid squint in bright light seems self-evident, data are not available to support either benefit. The purpose of this study was to measure the effect of eyelid squint on VA in the presence of refractive blur and on visual field sensitivity. Nineteen subjects with optimal refractive correction were tested, with and without squinting, as follows: (1) distance VA with induced refractive errors of +0.50, +1.00, +2.00, +3.00, +1.00 -1.00 x 90, and +1.00 -1.00 x 180; (2) near VA with induced refractive errors of -1.00 x 90 and -1.00 x 180; and (3) central and peripheral threshold visual fields with a Humphrey Field Analyzer. Differences in visual acuity between squinting and nonsquinting were tested for significance with repeated-measures analysis of variance, and differences in visual fields were tested using mixed model analysis of variance with repeated measures. Eyelid squint significantly improved (p < 00.016) distance VA measurements for 1.00 to 3.00 D of induced myopia. The squint-induced VA improvement increased from 0.06 logarithm of the minimum angle of resolution for 1.00 D to 0.24 logarithm of the minimum angle of resolution for 3.00 D of myopia. Eyelid squint also significantly reduced visual field sensitivity below the horizontal meridian by an average of 1.4 dB, by 1.6 dB on the horizontal meridian, and with increasing reductions in the vertical field up to 11.6 dB for measurements 40 degrees above fixation. This pattern of decreased superior field sensitivity would decrease visual discomfort from overhead glare. The results provide empirical support that eyelid squint improves visual acuity for subjects with refractive error and reduces glare in the superior visual field.

The effects of accommodative facility training on a group of children with impaired relative accommodation—a comparison between dioptric treatment and sham treatment

The effects of accommodative facility training were evaluated by comparing training with plano lenses and ±2.00D lens flipper sets. Thirteen children with symptoms and signs of accommodative dysfunction were included in the study. Seven started with 2 weeks of plano lens training before proceeding to traditional dioptric flipper training; later, one patient from this group was lost to follow-up. The remaining six children used powered flipper training from the start. The positive (PRA) and negative relative accommodation (NRA) were examined every second week. During the initial training period both the PRA and the NRA decreased in the sham treatment group (P=0.010 and P=0.102, respectively), while the PRA and the NRA increased during the dioptric training in both groups (P=0.102 and P=0.033, respectively). The result of this study indicates that accommodative facility training has a real effect on the amplitude of relative accommodation in patients with impaired relative accommodation.

Visual acuity losses in pigeons with lesions of the nucleus of Edinger-Westphal that disrupt the adaptive regulation of choroidal blood flow.

Choroidal blood flow (ChBF) in birds is regulated by a neural circuit whose components are the retina, the suprachiasmatic nucleus, the medial division of the Edinger-Westphal nucleus (EWM), the ciliary ganglion, and the choriod. We have previously shown that lesions of EWM appear to result in pathological alterations in the retina. To determine whether EWM lesions also lead to altered visual functions, we have examined the effects of EWM lesions on visual acuity in pigeons. Bilateral lesions of EWM were made electrolytically, and visual acuity for high-contrast, square-wave gratings was determined behaviorally about 1 year later and compared to that of a group of pigeons that had received sham lesions of EW about 1 year prior to acuity testing. Because lesions targeting EWM invariably resulted in damage to the adjoining lateral part of the Edinger-Westphal nucleus (EWL), which controls pupillary constriction and accommodation, two additional control groups were studied. In one such control group, bilateral lesions in the area pretectalis (AP), which innervates the pupillary control part of EWL and thereby controls pupillary constriction, were made and the effects on visual acuity determined about 1 year later. In the second such control group, the effects of acute accommodative and pupillary dysfunction on acuity were studied in pigeons made cycloplegic. The accuracy of all lesions was later confirmed histologically. The mean acuities of birds with AP lesions (9.1+/-1.4 cycles/deg) and sham lesions (7.1+/-1.5 cycles/deg) were not significantly different from normal, based on published normative data on pigeons. In contrast, pigeons with lesions that completely destroyed EW bilaterally showed visual acuity (2.7+/-0.1 cycles/deg) that was well below the acuity of the sham and AP-lesion control groups. The acuity of the cycloplegic pigeons (4.8+/-0.3 cycles/deg) and one pigeon with a nearly complete bilateral EWL but a unilateral EWM lesion (6.4 cycles/deg) indicated that only about half of the loss with a bilateral EW lesion could be attributed to accommodative dysfunction. Thus, bilateral destruction of EWM appears to have led to a loss in visual acuity. This conclusion suggests that disruption of adaptive neural regulation of ChBF may impair visual function. Destruction of EWM was, however, associated with damage to the somatic components of the oculomotor and trochlear nuclei. The possibility cannot be excluded that such damage also contributed to the acuity loss.

Irlen lenses do not improve accommodative accuracy at near.

The purpose of the experiment was to determine the influence of Irlen lenses on steady-state accommodation in successful users, as there is speculation that near accommodative dysfunction may be a factor in these patients. Monocular steady-state accommodation in six successful Irlen patients was assessed for near blur stimuli (2, 3, and 4 D) either with nonfiltered spectacle refractive correction or their spectrally broad-band filtered spectacle refractive correction. Accommodation was measured subjectively using a Hartinger coincidence optometer. There was no significant difference in mean level of accommodation between the two conditions. Additionally, there was a small but significant increase in accommodative variability with the filtered prescription. The use of Irlen correction did not have any positive effect on monocular steady-state accommodation at near.

Visual development in infants and young children with Down's syndrome

Purpose: Ocular and refractive defects are common amongst people with Down's syndrome. We are conducting a long‐term study of the development of refraction, accommodation and acuity in infants with Down's syndrome, from 12 weeks of age, in order to identify age of onset and possible consequences of such defects.Methods: To date, 54 children have entered the study. All measurements are made during home visits, and comprise Mohindra and dynamic retinoscopy, and Preferential Looking.Results: Cross‐sectional data suggest that acuity lies within normal ranges in infancy, and falls behind the norms only from the age of 2 years. Refractive errors in the general population decrease in infancy (the process of emmetropisation). Our data show that the opposite happens in children with Down's syndrome. The prevalence of refractive errors is higher in the preschool and school‐age children, than amongst the infants. Accommodation is defective from the earliest age of testing. Infants and young children with Down's syndrome consistently under‐accommodate to near targets, even when visual acuity and refractive errors are normal.Conclusions: The implication of accommodative dysfunction on emmetropisation is considered, and the possible association between visual and cognitive development explored.

Investigation of accommodative and binocular function in dyslexia.

The visual correlates of dyslexia are the subject of controversy, and much evidence suggests that they may include some aspects of binocular and accommodative function. These factors were investigated in 43 control and 39 dyslexic children, who were matched for age, sex and performance intelligence quotient. The dyslexic group exhibited significantly lower positive and negative vergence reserves, and vergence instability when the eyes were dissociated at near. Their amplitudes of accommodation also were significantly reduced. However, other measures including dissociated and associated heterophoria and accommodative lag and facility were similar in both groups. The stability of motor ocular dominance, as assessed with a modified Dunlop test, was similar in both groups. The results of a simulated reading visual search task suggested that the vergence and accommodative dysfunction were not a major cause of the dyslexia. Further analyses, using reading-age matched groups, suggested that these ocular motor correlates were not attributable to the better reading performance in the control group. The most likely remaining explanation is that they are, in most cases, non-causal correlates of the dyslexia.

Relation among Accommodative Facility, Lag, and Amplitude in Elementary School Children

Normative data for accommodative lag, facility, and amplitude of children have been presented in the literature for each of the parameters separately. This paper delineates the relation among accommodative amplitude, lag, and flexibility for grade school children. Approximately 200 children were screened. Those who wore corrective lenses, had uncorrected acuity worse than 6/9 (20/30) in either eye, had strabismus, had a refractive error outside the range from 0.00 to +0.75 D; or astigmatism greater than 0.50 D were excluded from the study. Of the 123 who remained, 53% had a deficit in accommodative facility, 26% had a deficit in lag, and 25% had a deficit in amplitude from that which would be expected from their age. Sixteen percent had deficits in both facility and lag. Eighteen percent had deficits in both amplitude and lag. Twenty-four percent had deficits in both facility and amplitude. Only 4% had deficits in all three of the accommodative functions considered--amplitude, lag, and facility. Clinically, these results indicate that when a patient's accommodative dysfunction is examined all facets of accommodation--lag, facility, and amplitude--need to be evaluated.

Predicting results in the orthoptic treatment of accommodative dysfunction.

A retrospective analysis of the records of 114 orthoptic patients diagnosed as having accommodative dysfunction (accommodative insufficiency, fatigue of accommodation, infacility of accommodation, or spasm of accommodation) has allowed the construction of models of the results of orthoptic treatment. Discriminant analysis completed on various samples of the group provides linearized discriminant functions for the success of the treatment (either total or partial/none) and for the change in accommodative amplitude. These data indicate that linearized discriminant functions using the age and AC/A ratio of the patient are effective in postpredicting the success category of 60% of a calibration sample of 99 patients. Similar functions using the patient's age, initial accommodative amplitude, and blur value of the near positive vergences allow the postprediction of the category of change in accommodative amplitude with treatment (3 D or more vs. 2 D or less). Seventy-eight percent of a sample of 68 patients were correctly classified. The application of these models in predicting the results of treatment of similarly afflicted subjects is discussed.

Accommodative dysfunction.

A retrospective review of the records of 114 subjects with accommodative dysfunction has been completed. Most subjects (N = 96) were found to have accommodative insufficiency. Lesser numbers of subjects were categorized in the class of infacility of accommodation (N = 14), spasm of accommodation (N = 3) and fatigue of accommodation (N = 1). A majority of the subjects presented with complaints of blur, headaches and/or asthenopia while attempting nearwork. Most subjects presented with reduced abilities in one or more of the following areas: accommodative amplitude and facility, fusional vergences, near point of convergence and stereo acuities. The clinical characteristics of the group as a whole and the major subgroups have been examined both before and after treatment of the condition with orthoptic exercises and/or plus lenses at the nearpoint. The result of the treatment indicates that although most subjects (96%) experienced some relief with treatment only about half (53%) had their problems totally solved. The importance of these findings is briefly discussed.