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Neural Regeneration Research Nov 2023Amblyopia is the most common cause of vision loss in children and can persist into adulthood in the absence of effective intervention. Previous clinical and neuroimaging...
Amblyopia is the most common cause of vision loss in children and can persist into adulthood in the absence of effective intervention. Previous clinical and neuroimaging studies have suggested that the neural mechanisms underlying strabismic amblyopia and anisometropic amblyopia may be different. Therefore, we performed a systematic review of magnetic resonance imaging studies investigating brain alterations in patients with these two subtypes of amblyopia; this study is registered with PROSPERO (registration ID: CRD42022349191). We searched three online databases (PubMed, EMBASE, and Web of Science) from inception to April 1, 2022; 39 studies with 633 patients (324 patients with anisometropic amblyopia and 309 patients with strabismic amblyopia) and 580 healthy controls met the inclusion criteria (e.g., case-control designed, peer-reviewed articles) and were included in this review. These studies highlighted that both strabismic amblyopia and anisometropic amblyopia patients showed reduced activation and distorted topological cortical activated maps in the striate and extrastriate cortices during task-based functional magnetic resonance imaging with spatial-frequency stimulus and retinotopic representations, respectively; these may have arisen from abnormal visual experiences. Compensations for amblyopia that are reflected in enhanced spontaneous brain function have been reported in the early visual cortices in the resting state, as well as reduced functional connectivity in the dorsal pathway and structural connections in the ventral pathway in both anisometropic amblyopia and strabismic amblyopia patients. The shared dysfunction of anisometropic amblyopia and strabismic amblyopia patients, relative to controls, is also characterized by reduced spontaneous brain activity in the oculomotor cortex, mainly involving the frontal and parietal eye fields and the cerebellum; this may underlie the neural mechanisms of fixation instability and anomalous saccades in amblyopia. With regards to specific alterations of the two forms of amblyopia, anisometropic amblyopia patients suffer more microstructural impairments in the precortical pathway than strabismic amblyopia patients, as reflected by diffusion tensor imaging, and more significant dysfunction and structural loss in the ventral pathway. Strabismic amblyopia patients experience more attenuation of activation in the extrastriate cortex than in the striate cortex when compared to anisometropic amblyopia patients. Finally, brain structural magnetic resonance imaging alterations tend to be lateralized in the adult anisometropic amblyopia patients, and the patterns of brain alterations are more limited in amblyopic adults than in children. In conclusion, magnetic resonance imaging studies provide important insights into the brain alterations underlying the pathophysiology of amblyopia and demonstrate common and specific alterations in anisometropic amblyopia and strabismic amblyopia patients; these alterations may improve our understanding of the neural mechanisms underlying amblyopia.
PubMed: 37282452
DOI: 10.4103/1673-5374.371349 -
Investigative Ophthalmology & Visual... Aug 2023To measure visual crowding, an essential bottleneck on object recognition and reliable psychophysical index of cortex organization, in older children and adults with...
PURPOSE
To measure visual crowding, an essential bottleneck on object recognition and reliable psychophysical index of cortex organization, in older children and adults with horizontal concomitant strabismus before and after strabismus surgery.
METHODS
Using real-time eye tracking to ensure gaze-contingent display, we examined the peripheral visual crowding effects in older children and adults with horizontal concomitant strabismus but without amblyopia before and after strabismus surgery. Patients were asked to discriminate the orientation of the central tumbling E target letter with flankers arranged along the radial or tangential axis in the nasal or temporal hemifield at different eccentricities (5° or 10°). The critical spacing value, which is the minimum space between the target and the flankers required for correct discrimination, was obtained for comparisons before and after strabismus surgery.
RESULTS
Twelve individuals with exotropia (6 males, 21.75 ± 7.29 years, mean ± SD) and 15 individuals with esotropia (6 males, 24.13 ± 5.96 years) participated in this study. We found that strabismic individuals showed significantly larger critical spacing with nasotemporal asymmetry along the radial axis that related to the strabismus pattern, with exotropes exhibiting stronger temporal field crowding and esotropes exhibiting stronger nasal field crowding before surgical alignment. After surgery, the critical spacing was reduced and rebalanced between the nasal and temporal hemifields. Furthermore, the postoperative recovery of stereopsis was associated with the extent of nasotemporal balance of critical spacing.
CONCLUSIONS
We find that optical realignment (i.e., strabismus surgery) can normalize the enlarged visual crowding effects, a reliable psychophysical index of cortical organization, in the peripheral visual field of older children and adults with strabismus and rebalance the nasotemporal asymmetry of crowding, promoting the recovery of postoperative stereopsis. Our results indicated a potential of experience-dependent cortical organization after axial alignment even for individuals who are out of the critical period of visual development, illuminating the capacity and limitations of optics on sensory plasticity and emphasizing the importance of ocular correction for clinical practice.
Topics: Adult; Male; Child; Humans; Adolescent; Visual Acuity; Strabismus; Amblyopia; Esotropia; Visual Perception; Sulfadiazine
PubMed: 37535007
DOI: 10.1167/iovs.64.11.5 -
Pediatric Health, Medicine and... 2023The COVID-19 pandemic came with many new challenges that forced personal and professional lifestyle modifications. Medical facilities were in scarcity against this new... (Review)
Review
The COVID-19 pandemic came with many new challenges that forced personal and professional lifestyle modifications. Medical facilities were in scarcity against this new unknown enemy and were challenged with the overloaded patient flow, scarcity of healthcare staff, and evolving treatment modalities with a better understanding of the virus each day. Ophthalmology as a "branch of medicine" suffered challenges initially because of a lack of guidelines for patient management, close working distance during routine examinations, and halt of major surgeries, including cataracts. Pediatric ophthalmology had major implications, as reduced outpatient visits would mean deeper amblyopia, and changed lifestyles, including online classes and home refinement, predisposing children to myopia, digital eye strain, and worsening of strabismus. COVID-19 also unveiled underlying accommodation and convergence anomalies that predisposed pediatric and adolescent patients to an increased prevalence of headache and acute onset esotropia. Teleophthalmology and other innovative solutions, including the use of prism glasses, safe slit-lamp shields, alternative ways of school screening with the use of photoscreeners, performing retinoscopy only when needed, and using autorefractors were among the few guidelines or modifications adopted which helped in the efficient and safe management of pediatric patients. Many pediatric ophthalmologists also suffered in terms of financial constraints due to loss of salary or even closure of private practices. School screening and retinopathy of prematurity screening suffered a great setback and costed a lot of vision years, data of which remains under-reported. Important implications and learnings from the pandemic to mitigate future similar situations include using teleophthalmology and virtual platforms for the triage of patients, managing non-emergency conditions without physical consultations, and utilizing home-based vision assessment techniques customized for different age groups. Though this pandemic had a lot of negative implications, the innovations, modifications, and other important learnings helped pediatric ophthalmologists in navigating safely.
PubMed: 37849985
DOI: 10.2147/PHMT.S395349 -
Taiwan Journal of Ophthalmology 2023Primary congenital glaucoma (PCG) occurs worldwide and has a broad range of ocular manifestations. It poses a therapeutic challenge to the ophthalmologist. A proper... (Review)
Review
Primary congenital glaucoma (PCG) occurs worldwide and has a broad range of ocular manifestations. It poses a therapeutic challenge to the ophthalmologist. A proper diagnostic evaluation under anesthesia is advisable for all children who do not cooperate for an office examination. Medical therapy only serves as a supportive role, and surgical intervention remains the principal therapeutic modality. Angle incision surgery such as goniotomy or trabeculotomy ab externo is the preferred choice of surgery in the Caucasian population. Primary combined trabeculotomy-trabeculectomy with or without antifibrotic therapy is the preferred choice in certain regions such as India and the Middle East where the disease usually presents with severe forms of corneal edema along with megalocornea. In refractory cases, trabeculectomy with antifibrotic therapy or glaucoma drainage devices are available options in the armamentarium. Cycloablative procedures should be reserved for eyes with poor visual potential. Myopia is common among children with PCG, and appropriate optical refractive correction in the form of glasses or contact lenses should be provided. Amblyopia therapy should be instituted to ensure overall visual development in the early developmental years. Low-vision rehabilitation services should be provided to children with vision impairment. Long-term follow-up is mandatory and carers of children with PCG should be counseled and educated about this need. Regardless of the visual outcomes, clinicians should emphasize the need for education of these children during the clinic visit. The overall goal of the management should be to improve the overall quality of life of the children with PCG and their carers.
PubMed: 38249492
DOI: 10.4103/tjo.TJO-D-23-00104 -
BMC Ophthalmology Jun 2024The long-term visual outcomes in spasmus nutans patients is largely unknown. The purpose of this study was to characterize visual outcomes and identify comorbid...
BACKGROUND
The long-term visual outcomes in spasmus nutans patients is largely unknown. The purpose of this study was to characterize visual outcomes and identify comorbid ophthalmic conditions in patients with spasmus nutans.
METHODS
We retrospectively reviewed the charts of consecutive patients diagnosed with spasmus nutans between 2000 and 2020. Demographic information, ophthalmic characteristics, and neuroimaging results were assessed over time.
RESULTS
Of the 32 patients included in the study, 13 (41%) were female. Underlying medical conditions included a diagnosis of Trisomy 21 in 6 (19%) and prematurity in 8 (25%). Twenty-one patients (66%) self-reported as a race other than Caucasian. 18 patients (56%) had non-private health insurance and 1 (3%) was uninsured. Mean age at diagnosis and resolution were 16 months (range 45 months) and 48 months (range 114 months), respectively. All 32 patients had nystagmus, 31 (97%) had head nodding and 16 (50%) had ocular torticollis. Mean follow-up was 66 months (range 185 months). On initial presentation, 6/32 (19%) had an amblyogenic refractive error and mean best-corrected visual acuity (BCVA) in the better-seeing eye was 0.78 Logarithm of the Minimum Angle of Resolution (LogMAR) (range 1.24). In a sub-analysis that included patients with > 1 exam (n = 23), 17/20 (85%) had an amblyogenic refractive error and mean BCVA in the better-seeing eye was 0.48 LogMAR (range 1.70). At the final exam, 12 patients had measurable stereopsis, eight had strabismus, and three had undergone strabismus surgery. Eight patients required treatment for amblyopia.
CONCLUSIONS
We found a high prevalence of amblyogenic refractive error, strabismus and amblyopia among patients with spasmus nutans. Children with spasmus nutans benefit from ongoing ophthalmic follow-up until they are past the amblyopic age range, even after resolution of nystagmus.
Topics: Humans; Female; Male; Retrospective Studies; Visual Acuity; Child, Preschool; Child; Infant; Follow-Up Studies; Nystagmus, Pathologic; Amblyopia; Strabismus
PubMed: 38867186
DOI: 10.1186/s12886-024-03494-7 -
Eye (London, England) Sep 2023Amblyopia is an important public health concern. While home-based screening may present an effective solution, this has not been rigorously assessed in a systematic... (Review)
Review
Amblyopia is an important public health concern. While home-based screening may present an effective solution, this has not been rigorously assessed in a systematic review. A systematic review was performed using Ovid MEDLINE, PubMed, The Cochrane Library, Embase, Web of Science Core Collection, and Clinicaltrials.gov. All studies reporting the diagnostic accuracy of home-based screening tools for amblyopia among children were included. Studies involving orthoptist or ophthalmologist-led screening and adult subjects were excluded. The main outcome measure was the diagnostic accuracy expressed as sensitivity and specificity. Among 3670 studies identified, 28 were eligible for inclusion in our systematic review. The age range of patients were less than 1 month to 16 years old. 7 studies used internet-based tools, 16 used smartphone/tablet applications, 3 used digital cameras, and 3 used home-based questionnaires and visual acuity tools. All studies included a reference standard except one, which was a longitudinal study. 21 studies had full ophthalmological examination whilst 6 studies had validated visual acuity measurement tools as gold standards. Of the 27 studies which compared against a reference test, only 25 studies reported sensitivity and specificity values. Using the QUADAS-2 tool, 50% of studies were deemed to have applicability concern due to patient selection from tertiary centres and unclear methods for recruitment. There is a need to improve the quality of diagnostic accuracy studies, standardise thresholds for detecting amblyopia, and ensure consistent reporting of results. Further research is needed to evaluate the suitability of these tools for amblyopia screening.
Topics: Adult; Child; Humans; Infant; Amblyopia; Longitudinal Studies; Sensitivity and Specificity; Physical Examination
PubMed: 36828959
DOI: 10.1038/s41433-023-02412-3 -
Frontiers in Neuroscience 2023Amblyopia is a common visual impairment that develops during the early years of postnatal life. It emerges as a sequela to eye misalignment, an imbalanced refractive...
Amblyopia is a common visual impairment that develops during the early years of postnatal life. It emerges as a sequela to eye misalignment, an imbalanced refractive state, or obstruction to form vision. All of these conditions prevent normal vision and derail the typical development of neural connections within the visual system. Among the subtypes of amblyopia, the most debilitating and recalcitrant to treatment is deprivation amblyopia. Nevertheless, human studies focused on advancing the standard of care for amblyopia have largely avoided recruitment of patients with this rare but severe impairment subtype. In this review, we delineate characteristics of deprivation amblyopia and underscore the critical need for new and more effective therapy. Animal models offer a unique opportunity to address this unmet need by enabling the development of unconventional and potent amblyopia therapies that cannot be pioneered in humans. Insights derived from studies using animal models are discussed as potential therapeutic innovations for the remediation of deprivation amblyopia. Retinal inactivation is highlighted as an emerging therapy that exhibits efficacy against the effects of monocular deprivation at ages when conventional therapy is ineffective, and recovery occurs without apparent detriment to the treated eye.
PubMed: 37795183
DOI: 10.3389/fnins.2023.1249466 -
Oman Journal of Ophthalmology 2024
PubMed: 38524343
DOI: 10.4103/ojo.ojo_28_24 -
Plastic and Reconstructive Surgery.... Oct 2023Metopic synostosis patients have a high prevalence of orthoptic anomalies, including hyperopia, astigmatism, and amblyopia. We hypothesized altered orbital anatomy...
BACKGROUND
Metopic synostosis patients have a high prevalence of orthoptic anomalies, including hyperopia, astigmatism, and amblyopia. We hypothesized altered orbital anatomy contributes to suboptimal visual outcomes by adversely affecting eye anatomy and growth from early life onward. Therefore, we aimed to investigate eye and orbital anatomy in metopic synostosis.
METHODS
We conducted a retrospective study in nonsyndromic metopic synostosis patients (n = 134, median age 0.43 years [IQR 0.45]) with nonsyndromic sagittal synostosis patients (n = 134, median age 0.27 years [IQR 0.23]) as controls. Primary analyses focused on eye dimensions (axial length, width, and globe height) and orbital dimensions, correcting for sex and age. Measurements were obtained from preoperative computed tomography scans.
RESULTS
Axial length and width in metopic synostosis patients did not differ from sagittal synostosis patients, but globe height was significantly smaller ( = 0.0002). Lateral wall interorbital length, lateral orbital wall length, anterior medial interorbital length, and maximal medial interorbital length were significantly smaller, and anterior vertical orbital height and maximal vertical orbital height were significantly larger ( < 0.001). The central orbital axis and interorbital angle were significantly narrower, and medial-to-lateral orbital wall angle was wider ( < 0.001).
CONCLUSIONS
Metopic synostosis patients have more shallow, wider, and higher orbits. Eye dimensions are similar in sagittal synostosis patients, although globe height was smaller. Altered orbital and eye dimensions in metopic synostosis probably have a causal relation with an unknown order of development. How these dimensions relate to future orthoptic anomalies (eg, refractive error) needs further investigation.
PubMed: 37823032
DOI: 10.1097/GOX.0000000000005303