Bilateral abnormalities of optic nerve size and eye shape in unilateral amblyopia

Assessing Choroidal Thickness in Pediatric Patients With Unilateral Strabismic Amblyopia by Using Spectral Domain-Enhanced Depth Imaging-Optical Coherence Tomography

Objective In this study, we aimed to evaluate the choroidal thickness in patients with unilateral strabismic amblyopia by using spectral domain-enhanced depth imaging-optical coherence tomography (SD-EDI-OCT) (Heidelberg Engineering GmbH, Heidelberg, Germany). Methods Twenty-five children with strabismic amblyopia and 20 age- and sex-matched healthy controls were included in this study. Seven sections were obtained, each comprising 25 repetitive images from each section at 200-micron intervals, and measurements were taken from nine different points at vertical and horizontal lines (1 and 3 mm from the subfoveal, superior, inferior, temporal, and nasal regions), centered on the fovea, using SD-EDI-OCT. Choroidal thickness values were obtained by measuring the distance between the basal border of the retinal pigment epithelium and the choroidoscleral border. The Mann-Whitney U test was used to compare choroidal thickness between the amblyopic and the control groups. Results The mean age of children with amblyopia and that of controls were 8.4 ±2.7 and 9.9 ±3.3 years, respectively (p=0.120). The mean subfoveal choroidal thickness was 372.8 ±78.9 μm in amblyopic eyes and 372.4 ±79.3 μm in the fellow eyes, both of which were thicker than the control eyes (310.9 ±76.3 μm; p<0.05 for each). Similarly, the mean values for the choroidal thickness of the amblyopic children at 1 mm nasal (320 ±86 μm), 1 mm superior (363 ±70 μm), and 3 mm superior (336 ±62 μm) were also significantly thicker than those of the corresponding control eyes (p<0.05 for each). There was a negative correlation between the subfoveal choroidal thickness and axial length (r=-0.332, p=0.005). There were no correlations between the choroidal thickness, age, and visual acuity. Conclusions The choroidal thicknesses of strabismic and fellow eyes were similar in patients with strabismic amblyopia. However, the choroidal thickness of both eyes in strabismic children was significantly thicker than those of the healthy controls. Emmetropization may be defective in both eyes of strabismic amblyopic patients.

Evaluation of Macular Ganglion Cell-Inner Plexiform Layer in Children with Deprivational Amblyopia Who Underwent Unilateral Cataract Surgery

Background and Objectives: The aim of the study is to assess macular ganglion cell and inner plexiform layer (mGCIPL) thickness in deprivational amblyopic eyes (AE), fellow non-amblyopic eyes (FE) and normal eyes (NE) using spectral. domain optical coherence tomography (SD-OCT). Materials and Methods: Twenty two children (64% boys) who underwent surgical removal of unilateral congenital or developmental cataracts and exhibited visual impairment despite postoperative visual rehabilitation were included in the study. Cataract surgery was performed in patients aged 55.82 ± 35.85 months (range 6 to 114 months). The mean age of the study group was 9.73 ± 2.85 years (range 5 to 15 years). The comparison group consisted of 22 healthy age- and gender-matched children. The best corrected visual acuity (BCVA) after surgery was: 0.75 ± 0.27 (range 0.3 to 1.3) in AE, 0.1 ± 0.13 (range 0 to 0.5) in FE and 0.04 ± 0.07 (range 0 to 0.2) in NE. OCT scans were performed in all patients and subsequently corrected for axial length related magnification errors. Results: The average thickness of mGCIPL was 70.6 ± 11.28 μm in AE; 77.50 ± 6.72 μm in FE and 81.73 ± 5.18 μm in NE. We found that mGCIPL was statistically significantly thinner in deprivation AE compared to FE (p = 0.038) and NE (p = 0.0005). The minimum thickness of mGCIPL was respectively: 62.68 ± 13.2 μm, 70.3 ± 7.61 μm, and 74.5 ± 5.47, and also differed between AE and FE (p = 0.023) and AE and NE (p = 0.0004). Also, measurements in the inferior, inferotemporal, and superotemporal sectors showed thinning of mGCIPL in AE compared to NE. Conclusions: This analysis may suggest that deprivational amblyopia caused by unilateral congenital or developmental cataract in children may be associated with mGCIPL thinning.

Role of Structural, Metabolic, and Functional MRI in Monitoring Visual System Impairment and Recovery

The visual system, consisting of the eyes and the visual pathways of the brain, receives and interprets light from the environment so that we can perceive the world around us. A wide variety of disorders can affect human vision, ranging from ocular to neurologic to systemic in nature. While other noninvasive imaging techniques such as optical coherence tomography and ultrasound can image particular sections of the visual system, magnetic resonance imaging (MRI) offers high resolution without depth limitations. MRI also gives superior soft-tissue contrast throughout the entire pathway compared to computed tomography. By leveraging different imaging sequences, MRI is uniquely capable of unveiling the intricate processes of ocular anatomy, tissue physiology, and neurological function in the human visual system from the microscopic to macroscopic levels. In this review we discuss how structural, metabolic, and functional MRI can be used in the clinical assessment of normal and pathologic states in the anatomic structures of the visual system, including the eyes, optic nerves, optic chiasm, optic tracts, visual brain nuclei, optic radiations, and visual cortical areas. We detail a selection of recent clinical applications of MRI at each position along the visual pathways, including the evaluation of pathology, plasticity, and the potential for restoration, as well as its limitations and key areas of ongoing exploration. Our discussion of the current and future developments in MR ocular and neuroimaging highlights its potential impact on our ability to understand visual function in new detail and to improve our protection and treatment of anatomic structures that are integral to this fundamental sensory system. LEVEL OF EVIDENCE 3:   TECHNICAL EFFICACY STAGE 3:  .

Associations between visual function and ultrastructure of the macula and optic disc after childhood cataract surgery

PURPOSE

To investigate the association between visual function and ultrastructural characteristics of the retina and optic disc in children operated for cataract and factors influencing this relationship.

METHODS

We included 56 children aged 7-18 years who had been operated for bilateral or unilateral cataract. Three-dimensional swept source OCT scans of the macula and the optic disc were obtained using the Triton OCT (Topcon, Corporation, Tokyo, Japan). Best corrected distance visual acuity was measured using the HOTV 3 Meter visual chart. Contrast vision was evaluated using the Freiburg Visual Acuity Contrast Test (FrACT). Healthy fellow eyes of the unilateral group were used as control eyes.

RESULTS

We did not find any associations between visual acuity or contrast sensitivity and structural retinal parameters. Shorter axial length, the presence of glaucoma and pseudophakia (opposed to aphakia) were all significant predictors of greater mean macular thickness in a multiple regression analysis, (p = 0.039). Two children had foveal hypoplasia, and one child had a right eye with a thin, disorganized retina.

CONCLUSIONS

Children with pseudophakia have a thicker macula but this does not seem to be related to visual function. Obtaining high quality OCT scans of the macula and optic disc in severely visually impaired children with glaucoma and/or nystagmus is challenging. We found structural macular changes which contributed to poor vision but most eyes with very reduced vision were difficult to image, and the prevalence of structural changes may be underestimated.

Optical coherence tomography angiography in amblyopia: A critical update on current understandings and future perspectives

Optical coherence tomography angiography (OCTA) is a non-invasive tool to assess the retino-choroidal vasculature in vivo. It tracks the red blood cell movement and maps the vasculature in quick succession. In routine, diabetic retinopathy, age related macular degeneration, central serous chorioretinopathy, and others are commonly being studied to unveil its clinic role. On the other hand, amblyopia is a condition where the visual acuity is subnormal due to non-organic causes in the eye. But the OCTA studies till now have shown variable changes along retino-choroidal vasculature. Hence, to comprehend the existing literature knowledge, a systematic literature search was carried out and the original works describing novel findings in amblyopic eyes on OCTA were included. Upon detailed assessment, firstly, the disturbed vasculature along superficial retinal plexus, deeper retinal plexus, and choroidal plexus were evident in most untreated amblyopic eyes. However, such changes were not uniform, which is due to noted heterogenic patient profile, small sample size, biometric biases, non-uniform algorithms, and other factors. And to note, even in presence of such diverse changes, almost all the authors stated a plausible explanation for their notable changes. Secondly, the utility of OCTA in identifying vascular changes with standard treatments and segregation of visual beneficiaries from non-beneficiaries were possible. Hence, to conclude, OCTA is a valuable tool which can provide valuable useful insights into the amblyopic eyes during pre and post treatment periods. However, to gather more concrete evidence for clinical benefits, systematic, homogenous, and better structured clinical studies are mandated.

In vivo MRI evaluation of early postnatal development in normal and impaired rat eyes

This study employed in vivo 7-T magnetic resonance imaging (MRI) to evaluate the postnatal ocular growth patterns under normal development or neonatal impairments in Sprague-Dawley rats. Using T2-weighted imaging on healthy rats from postnatal day (P) 1 (newborn) to P60 (adult), the volumes of the anterior chamber and posterior chamber (ACPC), lens, and vitreous humor increased logistically with ACPC expanding by 33-fold and the others by fivefold. Intravitreal potassium dichromate injection at P1, P7, and P14 led to T1-weighted signal enhancement in the developing retina by 188-289%. Upon unilateral hypoxic-ischemic encephalopathy at P7, monocular deprivation at P15, and monocular enucleation at P1, T2-weighted imaging of the adult rats showed decreased ocular volumes to different extents. In summary, in vivo high-field MRI allows for non-invasive evaluation of early postnatal development in the normal and impaired rat eyes. Chromium-enhanced MRI appeared effective in examining the developing retina before natural eyelid opening at P14 with relevance to lipid metabolism. The reduced ocular volumes upon neonatal visual impairments provided evidence to the emerging problems of why some impaired visual outcomes cannot be solely predicted by neurological assessments and suggested the need to look into both the eye and the brain under such conditions.

Reduced Photoreceptor Outer Segment Layer Thickness and Association with Vision in Amblyopic Children and Adolescents with Unilateral High Myopia

PURPOSE

To quantitatively compare reflectivity and other morphological changes of the photoreceptors of normal eyes with amblyopic eyes using the longitudinal reflectance profile (LRP) on swept-source optical coherence tomography (SS-OCT) images in children and adolescents with unilateral high myopia. The relationships between OCT parameters and visual acuity were investigated.

METHOD

Twenty-six amblyopes with unilateral high myopia and 34 age-, axial length- and spherical equivalent-matched normal controls were recruited. All participants underwent SS-OCT and detailed ophthalmic investigations. The reflectivity of the outer retinal and photoreceptor outer segment layer thickness were quantified by LRP using ImageJ software. All parameters were measured at three selected regions: at the fovea, 1 mm nasal to the fovea and 1 mm temporal to the fovea. Differences between the groups were evaluated.

RESULTS

The mean choroidal thickness was thinner in amblyopic eyes compared with controls (165.19 ± 59.02 μm vs 214.97 ± 66.41 μm at the fovea; 128.77 ± 57.06 μm vs 161.54 ± 57.37 μm at 1 mm nasal to the fovea; 188.13 ± 59.51 μm vs 219.87 ± 61.78 μm at 1 mm temporal to the fovea, P < .05). The amblyopic eyes had higher reflectivity of the ellipsoid zone at 1 mm nasal to the fovea only (85.41 ± 25.78 vs 70.76 ± 18.69, P = .02). The mean length of the photoreceptor outer segment (OS) layer was significantly greater in the control eyes than in the amblyopic eyes at all three regions (20.19 ± 1.89 vs 18.70 ± 2.23 at the fovea, P = .006; 16.06 ± 1.47 vs 15.07 ± 1.30 at 1 mm nasal to the fovea, P = .008; 15.81 ± 1.58 vs 14.56 ± 1.87 at 1 mm temporal to the fovea, P = .006). The shortened OS length was associated with poorer visual acuity.

CONCLUSION

The results of this study revealed that the amblyopes with unilateral high myopia had thinner choroidal thickness and shortened OS thickness compared to normal controls. The findings indicate that abnormal anatomic changes in the amblyopic children and adolescents with unilateral high myopia were not only due to high myopia but more likely due to a combination of high myopia and amblyopia.

Evaluation of amblyopic eyes with optical coherence tomography angiography and electrophysiological tests

Purpose

To investigate the structural and functional changes of the retina and optic nerve in amblyopia.

Methods

Eighteen patients with unilateral anisometropic amblyopia and 27 age-matched healthy controls were involved in this study. All patients underwent optical coherence tomography angiography (OCTA), pattern visual evoked potential (pVEP), and flash electroretinogram (fERG).

Results

There was no statistically significant difference in terms of the foveal avascular zone (FAZ), perifoveal superficial density, whole superficial density, parafoveal deep density, perifoveal deep density among the eyes (P > 0 0.05). Significant differences were found only in superficial capillary plexus (SCP) vessel density in whole (P = 0.029) and parafoveal (P = 0.008) image. In electrophysiological tests, while VEP latencies of the amblyopic eyes increased compared to nonamblyopic eyes and controls (P = 0.027), VEP amplitudes decreased in amblyopic and nonamblyopic eyes compared to controls (P = 0.01), amplitudes of the rod (P = 0.027) and cones (P < 0.001) also decreased in amblyopic eyes compared to nonamblyopic and healthy eyes. When we assessed the correlation between the parameters of OCTA and electrophysiological test, only a significant correlation was found between parafoveal SCP vessel density and VEP amplitudes (r = 0.341).

Conclusion

We found a significant decrease only in SCP vessel density of the OCTA parameters in amblyopic eyes compared to healthy eyes. We detected a significant relationship between parafoveal SCP vessel density and VEP parameters, which might be associated with the underlying pathophysiology of the amblyopia.

Neonatal sleep development and early learning in infants with prenatal opioid exposure

The aim of this chapter is to examine the role of sleep and cognition in the context of the cumulative risk model examining samples of at-risk infants and maternal-infant dyads. The cumulative risk model posits that non-optimal developmental outcomes are the result of multiple factors in a child's life including, but not limited to, prenatal teratogenic exposures, premature birth, family socioeconomic status, parenting style and cognitions as well as the focus of this volume, sleep. We highlight poor neonatal sleep as both an outcome of perinatal risk as well as a risk factor to developing attentional and cognitive capabilities during early childhood. Outcomes associated with and contributing to poor sleep and cognition during infancy are examined in relation to other known risks in our clinical population. Implications of this research and recommendations for interventions for this population are provided.

Retinal oximetry in normal and amblyopic children: a pilot study

PURPOSE

To study the retinal vascular oxygen saturation in amblyopic eyes and compare them to unaffected fellow eyes and eyes of normal subjects.

METHODS

A total of 32 amblyopic, 24 normal and 13 fellow eyes of patients below age of 18 were enrolled in this prospective observation study. Retinal oximetry was performed using the Oxymap T1 retinal oximeter. Retinal vascular oxygen saturations and diameters were compared between amblyopic eyes, normal eyes and unaffected fellow eyes.

RESULTS

The average age was 8.6 years in the amblyopia group (M:F 16:16) and 10.9 years in the normal group (M:F 7:5; p = 0.024). Median corrected distance visual acuity in the amblyopia group was 20/50; it was 20/20 in the other groups (p < 0.001). The average arteriolar and venous saturation in the amblyopia, normal and fellow group was 84.5% (95% CI: 82.6-86.4), 83.2% (95% CI: 80.7-85.6) and 80.8% (95% CI: 78.6-82.9) and 51.9% (95% CI: 50.4-53.4), 50.8% (95% CI: 48.2-53.4) and 49.3% (95% CI: 45.7-52.9). There was no statistically significant difference between the saturation values of the amblyopia group and the controls, however, significantly higher values were found in the amblyopia group compared to the fellow group for arteriolar and venous saturations (p = 0.013; p = 0.005). Arteriolar and venous diameters showed no significant difference between groups.

CONCLUSION

Amblyopic eyes showed higher mean oxygen saturations than the fellow eyes. This observation could be due to altered neuronal activity or could be due to a measurement artefact due to alterations in retinal reflectivity.

Quantitative analysis of retinal microcirculation in children with hyperopic anisometropic amblyopia: an optical coherence tomography angiography study

PURPOSE

To evaluate optical coherence tomographic angiography (OCTA) findings on retinal microcirculation in hyperopic anisometropic amblyopia compared with fellow eyes and nonamblyopic control eyes.

METHODS

A total of 40 pediatric patients with hyperopic anisometropic amblyopia and 57 control subjects were recruited, and 137 eyes (40 amblyopic, 40 fellow, and 57 control eyes) were evaluated. Data on best-corrected visual acuity (logMAR), axial length (mm), refractive error, and OCTA findings (foveal avascular zone parameters, macular vascular density in superficial and deep retinal capillary plexus, central macular thickness) were recorded in amblyopic, fellow, and control eyes.

RESULTS

Compared with fellow and control eyes, amblyopic eyes were associated with significantly lower foveal vessel density values within 300 μm around the foveal avascular zone (P < 0.01) and lower vascular density in certain areas of superficial and deep retinal capillary plexus in axial length- and refraction-adjusted analysis (P < 0.05 for all), along with significantly higher full thickness of the central macula (P = 0.04). In amblyopic eyes, best-corrected visual acuity values were negatively correlated with foveal density (r = -0.57; P = 0.02) and deep capillary retinal plexus vascular density in foveal (r = -0.51; P = 0.03) parafovea temporal (r = -0.52; P = 0.03), and parafovea superior (r = -0.51; P = 0.04) areas.

CONCLUSIONS

Our findings indicate a possible association between retinal microcirculation and amblyopia.

Evaluation of choroidal thickness in amblyopia using optical coherence tomography

Objective:

To investigate the choroidal thickness in children with amblyopia through spectral-domain optical coherence tomography.

Methods:

A total of 31 children with unilateral amblyopia and 31 right eyes of controls with normal vision were enrolled in the study. The choroidal thickness was measured directly below the fovea and at 12 other locations: 1, 2 and 3 mm superior, temporal, inferior, and nasal to the fovea. All the parameters were compared between amblyopic eyes, fellow eyes, and control eyes.

Results:

The mean subfoveal choroidal thickness was 398.03 ± 74.60, 354.13 ± 81.78, and 328.12 ± 65.93 μm in amblyopic eyes, fellow eyes, and control eyes, respectively. Significant difference was found in choroidal thickness among three groups at subfoveal choroidal thickness, N1, and S1 using multivariate analysis of covariance after adjusting for axial length. Significant negative correlation was found only between subfoveal choroidal thickness and axial length in amblyopic eyes (r = –0.463, p = 0.01).

Conclusion:

The subfoveal choroid is significantly thicker in amblyopic eyes than control eyes only at subfoveal choroidal thickness, N1, and S1. The choroidal thickness was thickest in the subfoveal region and thinnest in the nasal region. There are other changes in choroidal structure associated with amblyopia.

Increased choriocapillaris vessel density in amblyopic children: a case-control study

PURPOSE

To investigate the choriocapillaris in children with amblyopia, using optical coherence tomography angiography (OCT-A).

METHODS

Patients with amblyopia and age-matched controls were prospectively imaged using OCT-A. On OCT-A, the choriocapillaris measures 30 μm starting 31 μm posterior to the retinal pigment epithelium. The section of choriocapillaris under superficial retinal vessels was excluded from analysis to avoid shadowing or projection artifacts. The main outcome measure was choriocapillaris vessel density. Secondary outcome measures were foveal macular thickness and parafoveal macular thickness.

RESULTS

A total of 20 eyes of 16 patients with amblyopia and 25 eyes of 25 controls were included. Mean age of amblyopic subjects was 7.6 ± 3.6 years; of controls, 9.3 ± 2.2 years (P = 0.10). Mean refractive error of subjects was 4.3 ± 6.2 D; of controls, 0.0 ± 1.6 D (P = 0.004). Mean choriocapillaris vessel density was 74.8 ± 5.8 in the amblyopic group and 71.1 ± 3.6 in the control group, which was significant even after adjusting for age and refractive error (P = 0.012). There was no difference between groups in foveal macular thickness or parafoveal macular thickness; however, outer parafoveal macular thickness (the inner boundary of the inner nuclear layer to the retinal pigment epithelium outer boundary) was significantly greater in amblyopic eyes than in control eyes, even after adjusting for age and refractive error (203 ± 11 μm and 189 ± 12 μm, resp. [P = 0.014]).

CONCLUSIONS

In our study cohort, amblyopic eyes were found to have increased choriocapillaris vessel density as well as a greater outer parafoveal macular thickness, which may be due to alterations in outer retinal maturation.

Effect of optical correction on subfoveal choroidal thickness in children with anisohypermetropic amblyopia

The purpose of this study was to determine the effect of optical correction on the best-corrected visual acuity (BCVA) and subfoveal choroidal thickness (CT) in the eyes of children with anisohypermetropic amblyopia. Twenty-four anisohypermetropic amblyopic eyes and their fellow eyes of 24 patients and twenty-three eyes of 23 age-matched control children were studied. After one year of optical correction, the BCVA in the anisohypermetropic amblyopic eyes was significantly improved. Before the treatment, the mean subfoveal CT in the amblyopic eyes was 351.9 ± 59.4 μm which was significantly thicker than that of control eyes at 302.4 ± 63.2 μm. After the treatment, the amount of change in the subfoveal CT in the amblyopic and fellow eyes was greater than that in the control eyes. The amblyopic and fellow eyes with thicker choroids had a greater thinning of the choroid whereas eyes with thinner choroids had a greater thickening of the choroid. We conclude that wearing corrective lenses improves the visual acuity, and induces changes of the subfoveal CT in eyes with anisohypermetropic amblyopia.

Spectral-Domain Optical Coherence Tomographic Angiography in Children With Amblyopia

Importance

Amblyopia is the most common cause of visual impairment in childhood, with a prevalence of 1% to 4% in children in the United States. To date, no studies using noninvasive optical coherence tomographic angiography (OCTA) have measured blood flow in the retinal capillary layers in children with amblyopia.

Objective

To evaluate the retinal and microvascular features using OCTA in children (<18 years) with amblyopia.

Design, Setting, and Participants

This observational case-control study enrolled patients from September 1, 2016, through May 31, 2017, and was conducted from September 1, 2016, through June 30, 2017, at the Stein Eye Institute at UCLA (University of California, Los Angeles). Participants included 59 children (<18 years) with amblyopia and without amblyopia examined at a pediatric ophthalmology clinic or referred to the clinic by coinvestigators. All patients underwent comprehensive ophthalmological examination, including visual acuity, refraction, and ocular motility tests; anterior and posterior segment examination; and OCTA.

Main Outcomes and Measures

Reduced superficial and deep retinal capillary vessel density on OCTA.

Results

Of the 63 eyes evaluated, 13 (21%) were amblyopic and 50 (79%) were control eyes. Of the 59 patients, the mean (SD) age of patients with amblyopia was 8.0 (4.0) years and 10.3 (3.3) years for the controls; 33 patients (56%) were female; and 5 of 13 (39%) and 27 of 46 (54%) patients in the amblyopic and control groups, respectively, were identified as white. The macular vessel density of the superficial capillary plexus was lower in the amblyopic group than in the control group in both 3 × 3-mm and 6 × 6-mm scans. After adjusting for age and refractive error, the mean (SD) difference in the superficial capillary plexus in the 6 × 6-mm scan was statistically significant (49.3% [4.1] vs 51.2% [2.9]; P = .02). Macular vessel density of the deep capillary plexus in the 6 × 6-mm scans was also considerably different between groups: mean (SD) vessel density of the deep retinal capillary plexus was 54.4% (4.7%) in the amblyopia group and 60.1% (3.3%) in the control group, with a difference of 5.7% (95% CI, 3.4%-8.1%; P = .002).

Conclusions and Relevance

The study found that OCTA reveals subnormal superficial and deep retinal capillary density in the macula of patients with amblyopia. Further studies are needed to determine the clinical relevance of this finding.

Quantitative MRI criteria for optic pathway enlargement in neurofibromatosis type 1

OBJECTIVE

To determine quantitative size thresholds for enlargement of the optic nerve, chiasm, and tract in children with neurofibromatosis type 1 (NF1).

METHODS

Children 0.5-18.6 years of age who underwent high-resolution T1-weighted MRI were eligible for inclusion. This consisted of children with NF1 with or without optic pathway gliomas (OPGs) and a control group who did not have other acquired, systemic, or genetic conditions that could alter their anterior visual pathway (AVP). Maximum and average diameter and volume of AVP structures were calculated from reconstructed MRI images. Values above the 95th percentile from the controls were considered the threshold for defining an abnormally large AVP measure.

RESULTS

A total of 186 children (controls = 82; NF1noOPG = 54; NF1+OPG = 50) met inclusion criteria. NF1noOPG and NF1+OPG participants demonstrated greater maximum optic nerve diameter and volume, optic chiasm volume, and total brain volume compared to controls (p < 0.05, all comparisons). Total brain volume, rather than age, predicted optic nerve and chiasm volume in controls (p < 0.05). Applying the 95th percentile threshold to all NF1 participants, the maximum optic nerve diameter (3.9 mm) and AVP volumes resulted in few false-positive errors (specificity >80%, all comparisons).

CONCLUSIONS

Quantitative reference values for AVP enlargement will enhance the development of objective diagnostic criteria for OPGs secondary to NF1.

The assessment of anterior and posterior ocular structures in hyperopic anisometropic amblyopia

Background

The aim of this study was to examine the relationship or differences in ocular structures of amblyopic eyes compared to fellow eyes in children and young adults with hyperopic anisometropic amblyopia.

Material/Methods

Hyperopic participants with anisometropic amblyopia, defined as the presence of best-corrected visual acuity differences of at least 2 Snellen lines and 1.5 diopters between amblyopic and fellow eyes, were studied. Using the IOL Master, Pentacam Scheimpflug imaging and Spectralis optical coherence tomography, the axial length, corneal curvature, and anterior chamber depth (ACD), as well as the thickness of the cornea, peripapillary retinal nerve fiber layer (RNFL), and macula, were compared between children and young adults and between their amblyopic and fellow eyes.

Results

In 53 participants with hyperopic anisometropic amblyopia, there were significant differences in the anterior corneal curvature, ACD and axial length between the amblyopic and fellow eyes of all the patients. The mean central macular thickness in the amblyopic eyes was significantly thicker (P=.001) in the group aged 5 to 12 years; however, this was not the case in the group aged 13 to 42 years. There was no significant difference in average RNFL thickness in either group.

Conclusions

We found significantly greater mean central macular thickness in anisometropic amblyopic eyes among participants aged 5 to 12 years, but not among those who were older. Similarly, the interocular differences in axial length parameters seemed to be related to the central macular thickness differences between the amblyopic and fellow eyes in the younger group.

Choroidal and Peripapillary Retinal Nerve Fiber Layer Thickness in Adults with Anisometropic Amblyopia

Purpose

To evaluate choroidal thickness, macular thickness, and peripapillary retinal nerve fiber layer (RNFL) thickness in amblyopic eyes compared to fellow and normal control eyes using high-definition spectral-domain optical coherence tomography (SD-OCT).

Methods

Fifty-four without any systemic problem and ocular disease participated in this prospective study. Inclusion criteria included individuals older than 18 years with anisometropic amblyopia. Choroidal thickness, central macular thickness (CMT), and RNFL thickness were measured by using enhanced depth imaging SD-OCT. The choroidal thickness was measured at the fovea and at 500 μm intervals from the foveal center in both temporal and nasal directions. Axial length measurements of the cases were also recorded.

Results

Mean peripapillary RNFL thickness of the amblyopic, fellow, and control eyes was 107.5 ± 15.5 μm, 109.3 ± 12.7 μm, and 108.8 ± 8.6 μm, respectively (p = 0.343). The average CMT was 231.7 ± 14.7 μm in amblyopic eyes, 232.5 ± 15.7 μm in fellow eyes, and 230.8 ± 14.8 μm in control eyes (p = 0.599). Mean subfoveal choroidal thickness was significantly greater in the amblyopic eyes than in the fellow and control eyes (396.3 ± 104.3 μm, 361.0 ± 103.9 μm, 390.6 ± 91.7 μm). Mean axial measurement in amblyopic eyes was 22.7 ± 1.3 mm (20.5–26.1), in fellow eyes 23.1 ± 0.9 mm (20.9–25.0), and in control eyes 23.3 ± 0.9 mm.

Conclusions

In adults with anisometropic amblyopia, subfoveal, temporal, and nasal choroidal thickness of amblyopic eyes are significantly thicker than in fellow eyes. However, no significant differences in peripapillary RNFL thickness or CMT were found between amblyopic and fellow or control eyes.

Retinal thickness in children with anisohypermetropic amblyopia

PURPOSE

To determine the thickness of the fovea in eyes of children with anisohypermetropic amblyopia, their fellow eyes and eyes of age-matched controls. Additionally, to assess the effects of optical treatment on the foveal thickness in eyes with anisohypermetropic amblyopia.

MATERIALS AND METHODS

Twenty-one patients (6.0±2.3 years, mean±SD) with anisohypermetropic amblyopia and 25 age-matched controls (5.6±1.9 years) were studied. Spectral-domain optical coherence tomography (SD-OCT) was used to obtain OCT images. The foveal thickness and the thickness of the outer nuclear layer (ONL), photoreceptor inner segment (IS) layer and outer segment (OS) layer were measured by the embedded OCT software.

RESULTS

The length of the OS was significantly greater in the fellow eyes (48.0±6.6 µm) than in the amblyopic eyes (42.4±4.6 µm, p=0.03). One year after the optical treatment of the anisohypermetropia, the best-corrected visual acuity (BCVA) improved and the length of the OS was significantly increased (p=0.0001). After optical treatment, there was no more significant difference in the OS length between the amblyopic eyes and the fellow eyes (p=0.95). The change of BCVA was significantly correlated with the change of the length of the OS 1 year after the treatment (r=0.52; p=0.0004).

CONCLUSIONS

Anisohypermetropic amblyopic eyes have qualitative and quantitative differences in the retinal microstructures of the fovea from normal eyes. An increase in the OS length was detected in the amblyopic eyes after the optical treatment. A significant correlation was found between the increased OS length and better BCVA.

TRIAL REGISTRATION NUMBER

The trial registration number of the internal review board of Nara Medical University was 774.

Altered white matter in early visual pathways of humans with amblyopia

Amblyopia is a visual disorder caused by poorly coordinated binocular input during development. Little is known about the impact of amblyopia on the white matter within the visual system. We studied the properties of six major visual white-matter pathways in a group of adults with amblyopia (n=10) and matched controls (n=10) using diffusion weighted imaging (DWI) and fiber tractography. While we did not find significant differences in diffusion properties in cortico-cortical pathways, patients with amblyopia exhibited increased mean diffusivity in thalamo-cortical visual pathways. These findings suggest that amblyopia may systematically alter the white matter properties of early visual pathways.

The role of magnetic resonance imaging in diagnosing optic nerve hypoplasia

PURPOSE

To establish objective lower limits of normal optic nerve (ON) size in children based on high-resolution orbital magnetic resonance imaging (MRI).

DESIGN

Case-control study of patients with ON hypoplasia vs normal controls.

METHODS

A neuroradiologist made 4 measurements of each ON at 2 locations (5 mm posterior to the optic disc and just posterior to the optic canal) in patients with ON hypoplasia and controls aged 0-17 years from an academic eye center and children's hospital. Primary analyses were performed using mixed linear models.

RESULTS

Measurements were made in 26 cases of clinically confirmed ON hypoplasia and 31 controls (median age: ON hypoplasia, 1 year; controls, 5.5 years). Nine of 26 cases (35%) and 19 of 31 controls (61%) underwent high-resolution T2-weighted imaging of the orbits. Mean ON diameter was 1.36 mm (95% CI: 1.19-1.54; P < .001) smaller for clinically hypoplastic ONs than for controls. Optic nerve diameter increased by 0.05 mm per year of age (95% CI: 0.03-0.07; P < .001). A lower bound to the 95% prediction interval for normal optic nerves was (2.24 mm + 0.052 × [age in years]) mm and excluded all but 1 case.

CONCLUSIONS

Age was independently associated with normal ON size by MRI and should be taken into consideration when evaluating ON hypoplasia, based on MRI criteria. We have provided a formula to assist clinicians in objectively determining if ON hypoplasia is present.

The relationship between anisometropia and amblyopia

This review aims to disentangle cause and effect in the relationship between anisometropia and amblyopia. Specifically, we examine the literature for evidence to support different possible developmental sequences that could ultimately lead to the presentation of both conditions. The prevalence of anisometropia is around 20% for an inter-ocular difference of 0.5D or greater in spherical equivalent refraction, falling to 2-3%, for an inter-ocular difference of 3D or above. Anisometropia prevalence is relatively high in the weeks following birth, in the teenage years coinciding with the onset of myopia and, most notably, in older adults starting after the onset of presbyopia. It has about one-third the prevalence of bilateral refractive errors of the same magnitude. Importantly, the prevalence of anisometropia is higher in highly ametropic groups, suggesting that emmetropization failures underlying ametropia and anisometropia may be similar. Amblyopia is present in 1-3% of humans and around one-half to two-thirds of amblyopes have anisometropia either alone or in combination with strabismus. The frequent co-existence of amblyopia and anisometropia at a child's first clinical examination promotes the belief that the anisometropia has caused the amblyopia, as has been demonstrated in animal models of the condition. In reviewing the human and monkey literature however it is clear that there are additional paths beyond this classic hypothesis to the co-occurrence of anisometropia and amblyopia. For example, after the emergence of amblyopia secondary to either deprivation or strabismus, anisometropia often follows. In cases of anisometropia with no apparent deprivation or strabismus, questions remain about the failure of the emmetropization mechanism that routinely eliminates infantile anisometropia. Also, the chronology of amblyopia development is poorly documented in cases of 'pure' anisometropic amblyopia. Although indirect, the therapeutic impact of refractive correction on anisometropic amblyopia provides strong support for the hypothesis that the anisometropia caused the amblyopia. Direct evidence for the aetiology of anisometropic amblyopia will require longitudinal tracking of at-risk infants, which poses numerous methodological and ethical challenges. However, if we are to prevent this condition, we must understand the factors that cause it to develop.

Bilateral changes in foveal structure in individuals with amblyopia

PURPOSE

To examine foveal structure in amblyopia using spectral-domain optical coherence tomography (SD-OCT).

DESIGN

Prospective, cross-sectional study.

PARTICIPANTS AND CONTROLS

Two subject groups were recruited to the study: 85 amblyopes (34 adults, 51 children) and 110 visually normal controls (44 adults, 66 children).

METHODS

A detailed eye examination, including an SD-OCT scan, was performed in all participants. A total of 390 eyes of 195 subjects were imaged using a 3-dimensional (3D) macula scan covering a nominal 6 × 6-mm area with a resolution of 256 × 256 (65,536 axial scans). Data from the B-scans bisecting the fovea both horizontally and vertically were fitted with a mathematical model of the fovea to determine a range of foveal parameters.

MAIN OUTCOME MEASURES

Foveal thickness, foveal pit depth, and foveal pit slope.

RESULTS

Bilateral differences between the eyes of amblyopes compared with visually normal controls were found. The difference between foveal structure in amblyopic participants relative to structure in subjects with normal vision persisted even when variables such as age, ethnicity, axial length, and sex were taken into account. Amblyopes showed increased foveal thickness (+8.31 μm; P = 0.006) and a reduction in pit depth in the horizontal meridian (-10.06 μm; P = 0.005) but not in the vertical meridian (P = 0.082) when compared with subjects with normal vision. Foveal pit slopes were found to be approximately 1 degree flatter in the nasal (P = 0.033) and temporal (P = 0.014) meridians in amblyopes, but differences between amblyopes and controls in the superior (P = 0.061) and inferior (P = 0.087) meridians did not reach statistical significance. No statistically significant interocular differences were found in the foveal structure between amblyopic and fellow eyes.

CONCLUSIONS

Differences were found in the foveal structure in both eyes of amblyopes compared with subjects with normal vision. These differences consisted of increased foveal thickness, reduced pit depth when measured along the horizontal meridian, and flattening of the nasal and temporal sides of the foveal pit.

The effect of anisometropic amblyopia on retrobulbar blood flow parameters. Anisometropic amblyopia and retrobulbar blood flow

To look for a correlation between or the effect of anisometropia amblyopia on retrobulbar blood flow parameters. Peak systolic velocity (PSV) and end-diastolic velocity (EDV) of the ophthalmic artery (OA), central retinal artery (CRA), and temporal posterior ciliary artery (tPCA) were measured with color Doppler imaging, and systolic/diastolic ratio, resistivity index (RI), and pulsatility index (PI) were computed in 42 patients with anisometropic amblyopia. The mean PSV of OA, CRA, and tPCA in amblyopic and fellow eyes were 62.69 ± 24.04, 62.64 ± 20.18; 9.28 ± 3.71, 10.27 ± 4.18; 10.81 ± 4.59, 11.28 ± 4.91, respectively. The mean EDV of OA, CRA, and tPCA in amblyopic and fellow eyes were 15.87 ± 11.31, 14.52 ± 6.54; 2.48 ± 1.17, 2.62 ± 2.06; 3.04 ± 2.34, 3.14 ± 2.18, respectively. The mean RI of OA, CRA, and tPCA in amblyopic and fellow eyes were 0.76 ± 0.08, 0.76 ± 0.08; 0.72 ± 0.08, 0.74 ± 0.95; 0.72 ± 0.09, 0.72 ± 0.08, respectively. The mean PI of OA, CRA, and tPCA in amblyopic and fellow eyes were 1.77 ± 0.42, 1.81 ± 0.46; 01.58 ± 0.42, 1.59 ± 0.43; 1.54 ± 0.43, 1.58 ± 0.49, respectively. There was no statistically significant difference in any of the measured parameters between the amblyopic and fellow eyes. Anisometropic amblyopia did not cause any change in retrobulbar blood flow in amblyopic eyes.

Anomalous Vascular Patterns of the Optic Disc in Amblyopia

PURPOSE

To evaluate the presence of anomalies of the optic disc vascular patterns in subjects with amblyopia.

DESIGN

Case controlled study. The outcome measure is temporal deviation of central retinal vessels and / or vascular pattern asymmetry.

METHODS

A total of 342 hyperopic amblyopic patients were evaluated. An additional 88 subjects with equal visual acuity with strabismus, and 108 subjects with equal visual acuity and anisometropia were evaluated.

RESULTS

In this study, more than 50% of amblyopic patients had optic disc deformities. Sixty-five percent of subjects with amblyopia, orthophoria, and anisometropia exceeding 1.5 D had these anomalies compared with less than 7% of the groups without amblyopia or strabismus.

CONCLUSIONS

These disc anomalies may be associated with disorganization of optic nerve axons. This finding indicates the possibility of a peripheral cause for impaired vision and could provide an explanation for the variability in visual defects associated with amblyopia. Optic nerve imaging should be incorporated into clinical protocols for amblyopia research.

Longitudinal study of optic cup progression in children

PURPOSE

To determine the normative rate of cup-to-disc-ratio (C:D) progression in children and the effect of prematurity and low birth weight on this rate.

METHOD

In a single pediatric ophthalmology practice, a single examiner evaluated optic cup size by serial ophthalmoscopy over a minimum of 5 years in 92 patients (184 eyes) without intraocular surgery or optic nerve disease. A cross-sectional analysis of C:D was performed per year of age from 0 to 10 years and linear regression was used to compare C:D progression between preterm and term children and between low versus normal birth weight children.

RESULTS

Children exhibited progressive optic cupping. In term children, mean C:D increased by 0.0075 per year. Rate of mean C:D progression was double in children born preterm: 0.0160 (P = .049, comparison to term) per age-year. A similar, nonsignificant trend is observed when comparing low birth weight to normal children (P = .131).

CONCLUSION

Prematurity and low birth weight are associated with increased rate of cupping in children. Clinicians should recognize that C:D progression is not a specific sign of glaucoma in children.