Amblyopia

ABSTRACT Amblyopia is a developmental ocular disease of childhood-onset which may lead to persistent sequelae into adulthood. Early detection and management of amblyopia usually result in an improved visual outcome. The purpose of this study was to determine the prevalence and pattern of amblyopia in a rural hospital in Ghana. Clinical records of patients seen (from January 2014 to December 2018) at Westphalian Medical Center, Oyoko, Ashanti Region, Ghana, were reviewed retrospectively. Unilateral amblyopia was defined as a two-line interocular difference or more in visual acuity. Bilateral amblyopia was defined as best-corrected visual acuity (BCVA) of Snellen 6/12 or worse in both eyes, with evidence of bilateral ametropia or obstruction of the visual pathway. Following a review of 12,602 patient records, 258 cases of amblyopia were identified. The mean (±SD) presenting age of amblyopic patients was 24.3 ± 16.1 years, with a male-to-female ratio of 1:1.1. The period prevalence of amblyopia was 2.04%. The period prevalence of unilateral and bilateral amblyopia was 1.38% and 0.66%, respectively. The most prevalent form of amblyopia was refractive with a cumulative prevalence of 1.42%. Strabismic and stimulus deprivation amblyopia accounted for 0.36% and 0.21% of all amblyopic cases, respectively. A major cause of amblyopia in this population was refractive error, hence the use of spectacle correction for its initial management. Repeated assessment after an appropriate period of refractive adaptation would elucidate the proportion of amblyopias needing additional treatment modalities. Vision screening for early detection of amblyopia in childhood with accessible and effective management of amblyopia (including refractive correction and occlusion treatment) is necessary to reduce the impact of amblyopia in Ghana.

Non-strabismic, non-amblyopic intermittent central suppression (ICS) has been the crux of the challenge I have in accepting the conventional wisdom of suppression development: " Diplopiaphobia. " Reconciling the on-again, off-again intermittent loss of visual sensation that is ICS with cortical inhibition (often defined as masking at the cortex 1) as the proposed visual sensation shutdown mechanism is just hard. That inhibition must not only be intermittent, but alternating from side to side (in 80% of ICS patients) uncontrolled by some sort of volitional switch in fixation as occurs sometimes in alternating strabismus. Those shortcomings led me to explore how the vision science on visibility might apply to this intermittent type of suppression 2. My starting point was that the visual neurology is, well, the visual neurology. That is, whether strabismus is present or not, the neurology responsible for the suppression is in its basic construction-or perhaps in its beginning construction-the same, assuming no gross genetic or trauma-caused defects. The conventional wisdom, then, would hold that strabismus or anisometropia, through diplopiaphobia shuts down recognition of the visual signal for one side at the cortex and that defines suppression. But, if we redefine loss of the visual signal as vision science might, that is, as a loss of visibility (Troxlerʼs Perceptual Fading, possibly ICS 2), that loss of visibility is positioned as a more afferent-maybe more primary-visual sensory defect rather than being entirely secondary to misalignment or anisometropia. If accurate, an early interruption of visibility (visual sensation) changes the time course of sensory anomalies from current thought. With diplopiaphobia, although unstated, there's always a sense that " the organism " actively decides over time that diplopia doesn't work well. The diplopia comes first. If instead the sensory loss becomes more primary, the time-frame to defect may contract. And, in development of neurology and potential defects in development, time is of the essence. Exploring the consequences of loss of visibility to our view of the development of binocularity defects means putting that loss of visibility into the moving framework of time-inserting loss of visibility into the development of the visual neurology through time. But, moving the sensory defect from the cortex to the more afferent location of loss of visibility at or near the LGN also means any loss of visibility now affects development further upstream neurologically. Loss of visibility at the LGN, if developmentally early enough, has consequences for development at the cortex, versus the cortex interfering with its own development through masking. Science fiction has used intervention in the fourth dimension (time) as a vehicle for stories for decades. But, here we have real-life consequences through time from an early disturbance in information transfer. Assuming loss of visibility (that is, Troxlerʼs fading) may be responsible for the loss of sensation of intermittent central suppression led to the first suggested visual-behavioral consequence that I termed " visual dyslexia. " In this view, loss of visibility contributes to such classic behavioral descriptions of " dyslexia " as reading letters and words " backwards. " Loss of visibility not only creates fixation instability, but also surprisingly strong filling-in of the area that has lost visibility. 3 " Backwards " could easily be a short word seen correctly with one eye paired with a filled-in area from the fellow eye further confused (and variably confused?) by fixation instability. That the filling-in is strong enough to create rivalry with the " normally-seeing " eyeʼs image adds to the sense of loss-of-visibility variability in the central perception. This combination of a normal image conflicting with fixation-unstable filling-in could turn that short word into a variable visual mush-but a mush that has some " normal " characteristics from the non-suppressed eyeʼs image. Perhaps " seeing backwards " should be replaced with " confused image. " Importantly, this would move some of the visual part of " dyslexia "

Emerging technologies are now giving us unprecedented access to manipulate brain circuits, shedding new light on treatments for amblyopia. This research is identifying key circuit elements that control brain plasticity and highlight potential therapeutic targets to promote rewiring in the visual system during and beyond early life. Here, we explore how such recent advancements may guide future pharmacological, genetic, and behavioral approaches to treat amblyopia. We will discuss how animal research, which allows us to probe and tap into the underlying circuit and synaptic mechanisms, should best be used to guide therapeutic strategies. Uncovering cellular and molecular pathways that can be safely targeted to promote recovery may pave the way for effective new amblyopia treatments across the lifespan.

Although historically, treatment of amblyopia has been recommended prior to closure of a critical window in visual development, the existence and duration of that critical window is currently unclear. Moreover, there is clear evidence, both from animal and human studies of deprivation amblyopia, that there are different critical windows for different visual functions and that monocular and binocular deprivation have different neural and behavioral consequences. In view of the spectrum of critical windows for different visual functions and for different types of amblyopia, combined with individual variability in these windows, treatment of amblyopia has been increasingly offered to older children and adults. Nevertheless, treatment beyond the age of 7 years tends to be, on average, less effective than in younger children, and the high degree of variability in treatment response suggests that age is only one of many factors determining treatment response. Newly emerging treatment moda...

The major types of ametropia and visual problems for Hong Kong Chinese and Caucasian children are different. Consequently, the referral criteria developed for Caucasian children may not be applicable to Hong Kong children. Results of our study suggested that the referral criteria for Hong Kong children should be set as hyperopia of ≥+ 2.0 D, myopia of ≥ 1.0 D, anisometropis of ≥ 1.0 D and anisometropia of ≥ 1.25 D. Sensitivity using only these criteria for abnormal refraction in identifying children with amblyopia. Esotropia, exotropia and subnormal vision (< 6/12) was respectively 100%, 84.6%, 45.2% and 95.7%. The overall sensitivity for the identification of visual problems was 86.1 % and the overall specificity was 76%. If a cover test or a Hirschberg test was introduced into the screening battery so that all the strabismic cases were identified, the overall sensitivity would increase to 98.6%.

Amblyopia is one of the most common causes of visual impairment in adults and children, and visual loss may be permanent if not treated in time. Though many studies have been done on occlusion therapy which is the mainstay in the treatment of unilateral amblyopia, discrepancies exist in literature about quantification of treatment and follow up measures. The present study was undertaken to evaluate the factors responsible for the successful outcome of treatment and the optimum time required for the same in children with unilateral amblyopia. Baseline characteristics of 63 verbal patients with unilateral amblyopia (strabismic, anisometropic, mixed) referred to the Strabismus and Amblyopia Clinic at the Dr Rajendra Prasad Centre for Ophthalmic Sciences, New Delhi between September 2001 to December 2002 who improved to the desired level of visual acuity after treatment for amblyopia in the mentioned time period, were analyzed to assess for factors that directly or indirectly influenced...

Amblyopia is a developmental ocular disease of childhood-onset which may lead to persistent sequelae into adulthood. Early detection and management of amblyopia usually result in an improved visual outcome. The purpose of this study was to determine the prevalence and pattern of amblyopia in a rural hospital in Ghana. Clinical records of patients seen (from January 2014 to December 2018) at Westphalian Medical Center, Oyoko, Ashanti Region, Ghana, were reviewed retrospectively. Unilateral amblyopia was defined as a two-line interocular difference or more in visual acuity. Bilateral amblyopia was defined as best-corrected visual acuity (BCVA) of Snellen 6/12 or worse in both eyes, with evidence of bilateral ametropia or obstruction of the visual pathway. Following a review of 12,602 patient records, 258 cases of amblyopia were identified. The mean (±SD) presenting age of amblyopic patients was 24.3 ± 16.1 years, with a male-to-female ratio of 1:1.1. The period prevalence of amblyopia...

To investigate the level of agreement between orthoptists and medical practitioners in the comprehensive eye examination of children seen in an orthoptist-led triage clinic. Patient records over a 6-month period were retrospectively reviewed. Those with a presenting complaint related to vision or ocular motility were triaged into the orthoptist-led clinic and included in the study. Patients who did not meet the triage protocol and those who were not assessed by a medical practitioner at a subsequent appointment were excluded from analysis. The clinical findings from the orthoptist and medical practitioner were collected and compared. In total, sixty-three patients were reviewed during the 6-month period and met the inclusion criteria. After the initial comprehensive eye examination with an orthoptist, thirty-two were discharged from hospital and thirty-one were asked to return for a review appointment with a medical practitioner. Agreement between the orthoptists and medical practit...

The visual outcomes for infants 18 months or younger with cataracts have improved dramatically over the past couple of decades. Earlier detection of infantile cataract and prompt surgical removal-with subsequent visual rehabilitation with contact lenses-mean that these patients now have a much better visual prognosis. Advances in contact lens technology have led to a significantly higher success rate with contact lenses and this has been a major factor in improving the visual outcomes for aphakic infants. This review outlines the contact lens management of infantile cataract, including a detailed analysis of the various contact lens options available and a discussion regarding the important factors that can cause issues with contact lens wear and affect the overall visual rehabilitation of the infant.

Background: Standard clinical treatment methods for amblyopia penalize the non-amblyopic eye, with subsequent compliance problems, and do not address the binocular vision abnormality. The purpose of this study is to evaluate a novel approach to amblyopia

Background: Selective serotonin reuptake inhibitors (SSRIs) have been shown to enhance visual cortex plasticity in adult animals (Maya-Vetencourt, Sale et al. 2008). The aim of this study was to assess whether SSRIs increase visual cortex plasticity in humans. Methods: To test healthy visual plasticity, in the first experiment, participants (n = 20) with normal vision were randomized to a three-week course of fluoxetine or placebo. During drug administration, participants were trained on a motion discrimination task at a fixed motion direction. Learning was assessed for the trained motion direction and an untrained direction with and without a single dose of the benzodiazepine triazolam. Motor and visual cortex excitability was assessed using transcranial magnetic stimulation. In the second experiment, adults with amblyopia (n = 7) participated in a crossover study whereby placebo and citalopram were each combined with two weeks of occlusion therapy. Visual acuity (VA), stereopsis, electroretinograms and visual evoked potentials (VEPs) were measured fortnightly. The third experiment was a case study in which one participant with amblyopia completed two sessions of binocular training, one with placebo and the other with citalopram. Results: In the first experiment there was no effect of fluoxetine on learning or cortical excitability. However, triazolam significantly impaired performance for the untrained but not the trained motion direction. In the second experiment, there were no significant differences between citalopram and placebo for any of the outcome measures. However, three patients experienced VA improvements of over 0.1 Log MAR when treated with citalopram but not with placebo. Citalopram did not enhance the effects of binocular treatment for the single case tested. Conclusion: Fluoxetine did not affect visual cortex plasticity in normal observers. However, separate learning mechanisms were unveiled; as the untrained, but not the trained, task was affected by triazolam. Citalopram combined with occlusion may allow for VA improvements in some patients with amblyopia, however longer treatment durations may be required to improve visual functions in a larger number of patients. Preliminary data from one patient suggest that citalopram does not enhance the effects of binocular amblyopia treatment.

To identify children with isoametropic amblyopia due to moderate to high hyperopia and evaluate associated findings and visual acuity outcome.Charts from two university's pediatric ophthalmology clinics were reviewed retrospectively. Healthy children with ≥+4.5 D spherical equivalent who did not have anisometropia ≥ 1.5 D were selected for data collection. The charts of qualifying children with bilateral amblyopia (visual acuity of 20/40 or less) were further analyzed.Identified were 418 children with the above set of criteria for hyperopia; 36 of these children had isoametropic amblyopia (bilateral amblyopia). This gives an estimated prevalence of isoametropic amblyopia of 8.6% in children with at least 4.5 D of hyperopia in one or both eyes. The children with isoametropic amblyopia presented at a later age (5 years, 1 month) than the overall group of hyperopes (3 years, 5 months). Strabismus was less prevalent in this group (64%) than in the entire population of children with high hyperopia (81%). These children's amblyopia responded well to treatment with glasses, and patching in 13 (36%) cases. Surgical intervention for residual strabismus was necessary in very few cases (2 of 36, 5.5%).Children with hyperopia ≥ 4.5 D have an increased risk of amblyopia and strabismus that further threatens their future visual function. Isoametropic amblyopia is a real risk in these children. Based on these results, hyperopic correction should be prescribed for children with ≥4.5 D of hyperopia even if no strabismus or fixation preference is detected, to reduce this risk. Screening programs should also be in place to identify these children at an early age.