Optic nerve hypoplasia and small eyes in presumed amblyopia

Choroidal Thickness in Patients with Unilateral Amblyopia and Comparison between Anisometropic and Strabismic Amblyopia: A Prospective Cross-Sectional Study

Aims and Objectives

To determine the choroidal thickness (mainly subfoveal) using spectral domain optical coherence tomography (SD-OCT) in amblyopic eyes and to compare it with the choroidal thickness (CT) of healthy fellow eyes.

Materials and Methods

In this prospective study, 140 eyes of 70 patients (aged 5-40 years) with strabismic and anisometropic amblyopia were examined using enhanced depth imaging (EDI) mode in SD-OCT. The CT was measured directly below the fovea and six other locations: 500 μ, 1000 μ, and 1500 μ from fovea in both nasal and temporal quadrants.

Results

The mean age of the patients was 22.5 ± 11.2 years. The mean Best Corrected Visual Acuity (BCVA) in the amblyopic eyes was 0.87 ± 0.47 logMAR and 0 ± 0.02 logMAR in control eyes. The average subfoveal CT was 341.73 ± 60.39 μm in the amblyopic eyes and 314.77 ± 48.12 μm in the fellow eyes. Subgroup analysis showed that the patients with anisometropic amblyopia had a significantly thicker choroid as compared to the fellow healthy eyes (P = 0.00), whereas in strabismic amblyopic eyes, this difference was not significantly significant (P = 0.064).

Conclusion

Significant choroidal thickening was observed in subjects with amblyopia, which may contribute to the amblyopia pathogenesis and this could be used as a diagnostic parameter for amblyopia. These changes were more pronounced in patients with anisometropic amblyopia than strabismic amblyopia.

Ocular blood flow evaluation by laser speckle flowgraphy in pediatric patients with anisometropia

Purpose

To determine the differences and reproducibility of blood flow among hyperopic anisometropic, fellow, and control eyes.

Methods

We retrospectively studied 38 eyes of 19 patients with hyperopic anisometropia (8.2 ± 3.0 years of age) and 13 eyes of eight control patients (6.8 ± 1.9 years). We measured the optic nerve head (ONH) and choroidal circulation using laser speckle flowgraphy (LSFG) and analyzed the choroidal mean blur rate (MBR-choroid), MBR-A (mean of all values in ONH), MBR-V (vessel mean), MBR-T (tissue mean), and sample size (sample), which are thought to reflect the ONH area ratio, area ratio of the blood stream (ARBS). We then assessed the coefficient of variation (COV) and intraclass correlation coefficient (ICC) and compared the differences among amblyopic, fellow, and control eyes in MBR, sample, and ARBS.

Results

The ONH, MBR-A, MBR-T, and ARBS of amblyopic eyes were significantly higher than those of fellow eyes (P < 0.01, P < 0.05, and P < 0.05, respectively), and control eyes (MBR-A and ARBS, P < 0.05, for both comparisons). The sample-T (size of tissue component) in amblyopic eyes was significantly smaller than that in fellow and control eyes (P < 0.05). Blood flow in the choroid did not differ significantly between the eyes. The COVs of the MBR, sample, and ARBS were all ≤10%. All ICCs were ≥0.7. The COVs of pulse waveform parameter fluctuation, blowout score (BOS), blowout time (BOT), and resistivity index (RI) in the ONH and choroid were ≤10%.

Conclusion

The MBR value of the LSFG in children exhibited reproducibility. Thus, this method can be used in clinical studies. The MBR values of the ONH in amblyopic eyes were significantly high. It has been suggested that measuring ONH blood flow using LSFG could detect the anisometropic amblyopic eyes.

Retrobulbar Blood Flow Parameters in Patients With Anisometropic Amblyopia

Introduction We aim to compare retrobulbar blood flow parameters between the amblyopic eye and the fellow eye in patients with anisometropic amblyopia. Methods Peak systolic velocity (PSV) and end-diastolic velocity (EDV) of the ophthalmic artery (OA), central retinal artery (CRA), and posterior ciliary artery (PCA) were measured by color Doppler imaging (CDI), and the resistivity index (RI) and pulsatility index (PI) were calculated in 62 patients aged 12-40 years with anisometropic amblyopia. Results The mean PSV values of OA, CRA, and PCA in amblyopic and fellow eyes were 30.38 ± 10.34, 8.45 ± 2.27, and 8.03 ± 2.77, and 33.73 ± 14.46, 8.35 ± 2.05, and 8.81 ± 2.77, respectively. The mean EDV values of OA, CRA, and PCA in amblyopic and fellow eyes were 6.86 ± 2.64, 1.47 ± 1.59, and 1.94 ± 2.03, and 8.57 ± 4.30, 1.80 ± 1.73, and 2.32 ± 1.20, respectively. The mean RI values of OA, CRA, and PCA in amblyopic and fellow eyes were 0.77 ± 0.10, 0.85 ± 0.14, and 0.78 ± 0.15, and 0.75 ± 0.07, 0.79 ± 0.20, and 0.74 ± 0.13, respectively. OA-PSV and OA-EDV values were significantly lower in the amblyopic eye than in the healthy eye (p < 0.05). OA-RI values were significantly higher (p < 0.05) in the amblyopic eye than in the healthy eye. Conclusions Considering the decrease in PSV and EDV and the increase in RI, which are the blood flow parameters of the amblyopic eye, our study may provide guidance to focus on increasing blood flow in the treatment of amblyopia.

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.

Bilateral myelinated nerve fiber layers, high hyperopia, and amblyopia

We report a case of bilateral myelinated nerve fiber layer (MNFL) in a 24-year-old male with high hyperopia and amblyopia. He presented with poor vision bilaterally since childhood and was evaluated for ophthalmic and systemic diseases. Retinal examination indicated MNFLs in both eyes. The presence of bilateral MNFL associated with axial hypermetropia is rare. Ametropia seems to have a stronger influence on the relative visual acuity than the presence of retinal nerve fiber myelination. Early detection of ametropia and correction with glasses might prevent further deterioration of vision.

Impact of Amblyopia on the Central Nervous System

Amblyopia is a common perceptual disorder resulting from abnormal visual input during development. The clinical presentation and visual deficits associated with amblyopia are well characterized. Less is known however, about amblyopia's impact on the central nervous system (CNS). While early insights into the neuropathophysiology of amblyopia have been based on findings from animal models and postmortem human studies, recent advances in noninvasive magnetic resonance imaging (MRI) techniques have enabled the study of amblyopia's effects in vivo. We review recent retinal and neuroimaging research documenting amblyopia's structural and functional impact on the CNS. Clinical imaging provides some evidence for retinal and optic nerve abnormalities in amblyopic eyes, although the overall picture remains inconclusive. Neuroimaging studies report clearer changes in both structure and function of the visual pathways. In the optic nerves, optic tracts, and optic radiations of individuals with amblyopia, white-matter integrity is decreased. In the lateral geniculate nuclei, gray matter volume is decreased and neural activity is reduced. Reduced responses are also seen in the amblyopic primary visual cortex and extrastriate areas. Overall, amblyopia impacts structure and function at multiple sites along the visual processing hierarchy. Moreover, there is some evidence that amblyopia's impact on the CNS depends on its etiology, with different patterns of results for strabismic and anisometropic amblyopia. To clarify the impact of amblyopia on the CNS, simultaneous collection of retinal, neural, and perceptual measures should be employed. Such an approach will help (1) distinguish cause and effect of amblyopic impairments, (2) separate the impact of amblyopia from other superimposed conditions, and (3) identify the importance of amblyopic etiology to specific neural and perceptual deficits.

Macular capillary system and ganglion cell-layer complex of the amblyopic eye with optical cohorence tomography angiography and optical cohorence tomography

PURPOSE

To investigate the macular capillary system and ganglion cell-layer complex of the amblyopic eye with OCTA and OCT in comparison with fellow non-amblyopic eyes and a healthy control group and to examine their relationship with the severity of amblyopia.

METHODS

This prospective, cross-sectional comparative study enrolled 25 amblyopic patients and 25 healthy controls. All patients and controls underwent OCTA and OCT imagining. Macular vessel densities of the Superficial Capillary Plexus (SCP) and Deep Capillary Plexus (DCP) and retinal thickness were measured by OCTA and ganglion cell layer (GCL) by OCT.

RESULTS

SCP density at the fovea and parafovea was significantly lower in amblyopic eyes than in fellow eyes and control group. DCP density at the fovea was significantly lower in amblyopic eyes than fellow eyes and control group. Mean GCL thickness on OCT was 0.73 ± 0.07 μm in amblyopic eyes, 0.75 ± 0.06 μm in fellow eyes and 0.77 ± 0.06 μm in the control group. GCL volume was significantly lower in amblyopic eyes than the fellow eyes. The SCP and DCP and GCL thickness were not affected by the severity of amblyopia.

CONCLUSION

Macular vessel densities of the SCP and DCP of eyes with amblyopia is lower compared to the fellow non-amblyopic eyes and the control group. The thickness of GCL was lower in amblyopic eyes than fellow eyes while the severity of amblyopia did not have any impact on these structures. Microvascular retinal structures may have been affected in the course of amblyopia development.

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.

Comparison of the Thickness and Volume of the Macula and Fovea in Patients with Anisometropic Amblyopia Prior to and after Occlusion Therapy

Purpose

To compare the thickness of superior, temporal, inferior, and nasal macula and foveal thickness and volume in patients with anisometropic amblyopia prior to and after successful occlusion therapy using optical coherence tomography (OCT) measurement.

Methods

Data were collected prospectively on 30 patients with unilateral anisometropic amblyopia from December 2006 to August 2007. All patients had anisometropia of 2.0 diopters or more. OCT scans were obtained for all patients at diagnosis. Occlusion therapy was then prescribed and OCT scans were obtained again at the time of successful occlusion therapy (defined as interocular difference of <0.1 log units). The Stratus OCT-3 was used to measure fovea thickness and volume and the thickness of superior, temporal, inferior, and nasal macula (within a diameter of 3 mm).

Results

Of 30 patients, 22 (mean age of 5.8 years) had successful resolution of amblyopia. The mean duration of occlusion was 11.24 months and mean best-corrected visual acuity at diagnosis was 0.35 ± 0.12 logarithm of the minimum angle of resolution. The mean thicknesses of the superior, temporal, inferior, and nasal macula prior to and after occlusion were not significantly different (p > 0.05). However, mean foveal volume prior to occlusion therapy (0.15 ± 0.02 mm³) decreased after occlusion (0.14 ± 0.01 mm³) with statistical significance (Wilcoxon signed rank test, p = 0.025).

Conclusions

There was a meaningful decrease in foveal volume in patients with anisometropic amblyopia after successful occlusion therapy. Whether this decrease relates to visual improvement of the amblyopic eye remains to be determined.

Changes in macular parameters in different types of amblyopia: optical coherence tomography study

PURPOSE

The purposes of this study were to investigate the changes in macular parameters (thickness, volume) and peripapillary retinal nerve fiber layer (RNFL) thickness (RNFLT) in different cases of amblyopia versus the normal fellow eyes using optical coherence tomography (OCT) and to estimate the relationship of OCT changes with various defined patients' parameters.

DESIGN

This is a prospective, observational, cross-sectional case series.

METHODS

The method involved measuring the peripapillary RNFLT, macular thickness, and macular volume via spectral domain (OCT) in different types of amblyopia and comparing with the other fellow eyes. This study was conducted at the Mansoura Ophthalmic Center.

RESULTS

A total of 64 patients with different types of amblyopia were included. The mean central macular thickness (CMT) was 196.2±50.03 µm in the amblyopic eyes versus 167±12.76 µm in the fellow eyes (P=0.000), the mean average macular thickness was 265.80±12.77 µm in the amblyopic eyes versus 259.10±3.09 µm in the fellow eyes (P=0.000), the mean macular volume was 7.59±0.32 mm³ in the amblyopic eyes versus 7.34±0.071 mm³ in the fellow eyes (P=0.002), and the mean global RNFLT was 97.00±11.60 µm in the amblyopic eyes versus 78.50±13.05 µm in the fellow eyes (P=0.029). There was a discrepancy between the different amblyopic types. Age and the axial length were the only independent variables that statistically significantly correlated with the CMT.

CONCLUSION

The unilateral amblyopic eyes were prone to have a higher CMT and thicker global RNFL compared to those of the sound fellow eyes. Retinal variations between different types of the amblyopia differ from one type to another. The age could be considered as a predictor of the disease worsening and treatment prognosis. Further studies are required to emphasize these results.

Retina and Optic Disc Characteristics in Amblyopic and Non-amblyopic Eyes of Patients with Myopic or Hyperopic Anisometropia

Objectives:

To compare retinal and optic disc characteristics between amblyopic and non-amblyopic eyes in patients with myopic and hyperopic anisometropia measured with optical coherence tomography (OCT).

Materials and Methods:

Patients with myopic (25 patients: 17 female, 8 male; median age 27 years, range 16-40 years) and hyperopic (31 patients: 19 female, 12 male; median age 20 years, range 13-41 years) anisometropic amblyopia were included. Eye examination included determination of best-corrected visual acuity (BCVA) with a Snellen chart, measurement of manifest and cycloplegic refraction after pupillary dilation, alternate cover testing, globe movement evaluation, A-scan biometry for axial length, biomicroscopy, fundus examination, and OCT scanning. Main outcome measures were spherical equivalence, BCVA, axial length, retinal nerve fiber layer (RNFL) thickness, macular thickness, macular volume, and optic disc area.

Results:

In both myopic and hyperopic patients, the absolute value of the mean spherical equivalence was significantly greater in the amblyopic than non-amblyopic eyes, and the mean BCVA was significantly less in the amblyopic than the non-amblyopic eyes. In both myopic and hyperopic patients, there were no significant differences in mean RNFL thickness, macular thickness, macular volume, axial length, or optic disc area between amblyopic and non-amblyopic eyes.

Conclusion:

The amblyopic process may have no significant effect on the RNFL, macula, or optic disc. Further studies with more patients, including postmortem studies, may clarify the retinal, histopathologic, and anatomic differences between amblyopic and non-amblyopic eyes.

Understanding the Neural Basis of Amblyopia

Amblyopia is the condition in which reduced visual function exists despite full optical correction and an absence of observable ocular pathology. Investigation of the underlying neurology of this condition began in earnest around 40 years ago with the pioneering studies conducted by Hubel and Wiesel. Their early work on the impact of monocular deprivation and strabismus initiated what is now a rapidly developing field of cortical plasticity research. Although the monocular deprivation paradigm originated by Hubel and Wiesel remains a key experimental manipulation in studies of cortical plasticity, somewhat ironically, the neurology underlying the human conditions of strabismus and amblyopia that motivated this early work remains elusive. In this review, the authors combine contemporary research on plasticity and development with data from human and animal investigations of amblyopic populations to assess what is known and to reexamine some of the key assumptions about human amblyopia.

Evaluation of the retinal ganglion cell and choroidal thickness in young Turkish adults with hyperopic anisometropic amblyopia

The purpose of this study is to compare the choroidal thickness (CT) and ganglion cell complex (GCC) thickness of the normal fellow eyes and the amblyopic eyes using enhanced depth imaging optical coherence tomography (EDI-OCT) in young Turkish adults with hyperopic anisometropic amblyopia. Patients with unilateral hyperopic anisometropic amblyopia were enrolled and underwent a full ophthalmological assessment, including best-corrected visual acuity, cycloplegic refraction, and axial length (AL) measurements. Cirrus EDI-OCT was used to obtain subfoveal CT, GCC thickness, retinal nerve fiber layer (RNFL), and central macular thickness (CMT) measurements. Comparison was performed between the amblyopic eyes and the normal fellow eyes. Forty-three hyperopic anisometropic amblyopic patients were enrolled in this study. Mean age of 23 female and 20 male patients was 24.8 ± 7.4 years. Mean AL was 21.9 ± 1.3 and 22.4 ± 0.9 mm in amblyopic and fellow eyes, respectively (P < 0.05). Mean subfoveal CT measurements were 325.4 ± 44.2 and 317.9 ± 42.7 µ in amblyopic and fellow eyes, respectively. There was no statistically significant difference between the groups (P > 0.05). Mean GCC thickness was 83.8 ± 3.6 µ in amblyopic eyes and 83.5 ± 3.9 µ in the fellow eyes. Statistically significant difference was not seen between the groups (P > 0.05). Mean RNFL and mean CMT measurements were also similar in two groups (P > 0.05). Subfoveal CT, CMT, RNFL, and GCC thickness measurements were not statistically significant between hyperopic anisometropic amblyopic eyes and normal fellow eyes.

Analysis of Choroidal Thickness Using Spectral-Domain OCT in Children With Unilateral Amblyopia

PURPOSE

To compare the subfoveal, parafoveal, and peripapillary choroidal thickness in amblyopic eyes with those of fellow and control eyes.

METHODS

This institutional study involved 114 eyes from 38 patients with unilateral amblyopia and 19 healthy children, aged 6 to 17 years. The cause of amblyopia was identified as hyperopic anisometropia in 17 cases and strabismus in 21 cases. All patients underwent central macular thickness (CMT) and choroidal thickness measurement at seven retinal sites with spectral-domain optical coherence tomography (OCT). Statistical analysis was performed to compare the CMT and choroidal thickness of amblyopic and fellow eyes with control eyes.

RESULTS

Average CMT was 248.31 ± 24.18 μm in amblyopic eyes, 249.76 ± 26.08 μm in fellow eyes, and 243.65 ± 31.96 μm in controls (P = .604). Average subfoveal choroidal thickness was 394.15 ± 71.03 μm in amblyopic eyes, 356.07 ± 79.93 μm in fellow eyes, and 319.44 ± 87.29 μm in controls (P = .000). The choroidal thickness of the subfoveal area and at 750-μm intervals temporal and nasal to the fovea was significantly thicker in amblyopic eyes than in controls (P < .05). The choroidal thickness was significantly thicker in amblyopic eyes than in fellow eyes only at 750 μm nasal to the fovea. Type and depth of amblyopia did not differ significantly between foveal or parafoveal choroidal thickness (P > .05). There was a significant negative correlation between the nasal peripapillary choroidal thickness and the axial length in the amblyopic eyes (r = -0.37, P = .022). The choroidal thickness in the peripapillary area was not significantly different in the three groups (P > .05).

CONCLUSIONS

This study demonstrated that choroidal thickness can be measured by spectral-domain OCT in children with amblyopia. Subfoveal choroidal thickness in amblyopic eyes was significantly thicker than in control eyes. The amblyopic process may involve the choroid, but not the macula. However, further evaluation is needed.

A comparison between amblyopic and fellow eyes in unilateral amblyopia using spectral-domain optical coherence tomography

Purpose

To compare the macular retinal thickness and characteristics of optic nerve head (ONH) parameters in amblyopic and fellow eyes in patients with unilateral amblyopia.

Patients and methods

A total of 21 patients with unilateral amblyopia (14 patients with anisometropic amblyopia, four patients with strabismic amblyopia, and three patients with both) were examined using spectral-domain optical coherence tomography. The mean age of the patients was 8.5±3.5 years. The examined parameters included the mean macular (full, inner, and outer), ganglion cell complex and circumpapillary retinal nerve fiber layer (cpRNFL) thicknesses, and ONH parameters (rim volume, nerve head volume, cup volume, rim area, optic disc area, cup area, and cup-to-disc area ratio).

Results

The amblyopic eyes were significantly more hyperopic than the fellow eyes (P<0.001). Among the macular retinal thickness parameters, the cpRNFL thickness (P<0.01), macular full retinal thickness (3 mm region) (P<0.01), and macular outer retinal thickness (1 and 3 mm regions) (P<0.05) were significantly thicker in the amblyopic eyes than in the fellow eyes, while the ganglion cell complex thickness, macular full retinal thickness (1 mm region), and macular inner retinal thickness (1 and 3 mm regions) were not significantly different. Among the ONH parameters, the rim area was significantly larger and the cup-to-disc area ratio was smaller in the amblyopic eyes than in the fellow eyes (P<0.05). None of the other ONH parameters were significantly different between the investigated eyes. The differences in the cpRNFL thickness and macular outer retinal thickness in the 1 mm region were significantly correlated with the difference in axial length (P<0.05, r=−0.48; P<0.01, r=−0.59, respectively) and refractive error (P<0.05, r=0.50; P<0.01, r=0.60, respectively). The other parameters were not significantly related to the difference in axial length, refractive error, or best corrected visual acuity.

Conclusion

We found significant differences in some of the morphological measurements between amblyopic and fellow eyes that appear to be independent of abnormalities in the visual cortex.

Diffuse unilateral subacute neuroretinitis

Diffuse unilateral subacute neuroretinitis (DUSN) is a usually unilateral inflammatory disease characterized by an insidious, usually severe loss of peripheral and central vision. Clinical characteristics are manifested in early and late stages. Parasites of different sizes and several species of nematodes have been reported as the etiology of DUSN without conclusive evidence about the specific agent. Because serologic testing has been variable, the definitive diagnosis is made when the clinical characteristics of DUSN are found in conjunction with an intraocular worm. Laser photocoagulation, pars plana vitrectomy, thiabendazole, and albendazole have been used to treat DUSN with variable success.

Macular and retinal nerve fiber layer thickness in unilateral anisometropic or strabismic amblyopia

PURPOSE

To compare the macular and nerve fiber layer thicknesses as measured by optical coherence tomography (OCT) in amblyopic and fellow eyes.

METHODS

Fifty patients with monocular strabismic (n = 25) or anisometropic (n = 25) amblyopia (best corrected visual acuity (BCVA) ranging from 20/40 to 20/400) were included in a prospective cross-sectional descriptive study. A refractive error more than 5 diopters in either eye or an axial length difference between the eyes of more than 1 mm was excluded in the anisometropic group. In all cases, the thickness of the macular area and the peripapillary nerve fiber layer were measured by OCT in both amblyopic and fellow eyes and compared with each other.

RESULTS

The mean age of patients was 10 ± 3.1 years (range: 6 to 18 years) in the anisometropic group and 8.9 ± 3.7 years (range: 6 to 18 years) in the strabismic group. In the anisometropic group, the mean macular thickness was significantly increased in the amblyopic eyes (222.6 ± 47.8 μm) versus the fellow eyes (205.6 ± 33.3 μm) (P = .002), although there was no significant difference observed when comparing with the prepapillary nerve fiber layer (P = .55). There was no significant correlation of above-mentioned matters in the strabismic group (P = .07 and .52).

CONCLUSION

A thicker macula was found in anisometropic amblyopic eyes, but the increase of macular thickness in strabismic amblyopic eyes was not significant. Retinal involvement was not observed in the peripapillary nerve fiber layer of amblyopic eyes.

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.

Amblyopia and binocular vision

Amblyopia is the most common cause of monocular visual loss in children, affecting 1.3%-3.6% of children. Current treatments are effective in reducing the visual acuity deficit but many amblyopic individuals are left with residual visual acuity deficits, ocular motor abnormalities, deficient fine motor skills, and risk for recurrent amblyopia. Using a combination of psychophysical, electrophysiological, imaging, risk factor analysis, and fine motor skill assessment, the primary role of binocular dysfunction in the genesis of amblyopia and the constellation of visual and motor deficits that accompany the visual acuity deficit has been identified. These findings motivated us to evaluate a new, binocular approach to amblyopia treatment with the goals of reducing or eliminating residual and recurrent amblyopia and of improving the deficient ocular motor function and fine motor skills that accompany amblyopia.

Evaluation of peripapillary retinal nerve fiber layer, macula and ganglion cell thickness in amblyopia using spectral optical coherence tomography

AIM

To investigate peripapillary retinal nerve fiber layer (RNFL), macula and ganglion cell layer thicknesses (GCC) in amblyopic eyes with spectral domain optical coherence tomography (SD-OCT).

METHODS

Thirty six patients with a history of unilateral amblyopia and thirty two children who had emmetropia without amblyopia were included in this study. In this institutional study, 36 eyes of 36 patients with amblyopia (AE), 36 fellow eyes without amblyopia (FE), and 32 eyes of 32 normal subjects (NE) were included. RNFL, GCC and macular thickness measurements were performed with RS-3000 OCT Retina Scan (Nidek Inc CA. USA).

RESULTS

The mean global thicknesses of the RNFL were 113.22±21.47, 111.57±18.25, 109.96±11.31µm in the AE, FE, and NE, respectively. There was no statistically significant difference for mean global RNFL thickness among the eyes (P=0.13). The mean thicknesses of the macula were 258.25±18.31, 258.75±19.54, 248.62±10.57µm in the AE, FE and NE, respectively. There was no statistically significant difference for thickness of macula among the eyes (P=0.06). The GCC was investigated into two parts: superior and inferior. The mean thicknesses of superior GCC were 102.57±13.32, 103.32±10.64, 100.52±5.88µm in the AE, FE, and NE, respectively. The mean thicknesses of inferior GCC were 103.82±12.60, 107.82±12.33, 105.86±10.79µm in the AE, FE and NE, respectively. There was no statistically significant difference for thickness of superior and inferior GCC between the eyes (P=0.63, P=0.46).

CONCLUSION

The macular thicknesses of AE and FE were greater than the NE, although it was not statistically significant. Amblyopia does not seem to have a profound effect on the RNFL, macula and GCC.

A comparison between the amblyopic eye and normal fellow eye ocular architecture in children with hyperopic anisometropic amblyopia

PURPOSE

To compare the anterior and posterior ocular architecture of amblyopic and normal fellow eyes in children with hyperopic anisometropic amblyopia.

METHODS

Fourteen subjects with hyperopic anisometropic amblyopia were examined using the Pentacam and optical coherence tomography. For each participant, the amblyopic eye was compared to the fellow non-amblyopic eye.

RESULTS

There were no significant differences (P > 0.05) in the anterior corneal curvature, posterior corneal curvature, central corneal thickness, corneal volume, anterior chamber depth, anterior chamber volume, peripapillary retinal nerve fiber layer, central macular thickness, and macular volume between the amblyopic eye and fellow eye of the study participants.

CONCLUSIONS

The Pentacam and optical coherence tomography revealed no differences in the anterior and posterior ocular architecture between the amblyopic eye and fellow eye in children with hyperopic anisometropic amblyopia.

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.

Retinal nerve fiber layer thickness in recovered and persistent amblyopia

PURPOSE

To investigate, using optical coherence tomography (OCT), whether retinal nerve fiber layer thickness (RNFLT) is affected in amblyopic eyes.

METHODS

Using OCT (Stratus OCT™ [Carl Zeiss, Dublin, CA]), the RNFLT was measured in 26 patients with persistent unilateral amblyopia and in 25 patients with recovered unilateral amblyopia. The RNFLT was compared between the affected and fellow eyes in patients with persistent amblyopia and in those with recovered amblyopia, and between the amblyopic eyes of patients with persistent amblyopia and the previously amblyopic eyes of patients with recovered amblyopia.

RESULTS

In patients with persistent amblyopia and in those with recovered amblyopia, the affected eyes were significantly more hyperopic than the fellow eyes. The average (±standard deviation) RNFLT measured 105.5 ± 14.0 μm for the persistently amblyopic eyes; this value did not significantly differ from that of the fellow eyes (105.2 ± 13.0 μm) or the previously amblyopic eyes of recovered amblyopia (107.1 ± 11.7 μm). Also, logistic regression analysis adjusting for refraction showed no significant difference in the RNFLT between the persistently amblyopic eyes and the previously amblyopic eyes.

CONCLUSIONS

Our results indicate that there is no significant change in the RNFLT in amblyopic eyes.

Optic disc measurements using the Heidelberg Retina Tomograph in amblyopia

Purpose:

To investigate the characteristics of optic disc parameters in amblyopic eyes in which retinal involvement is uncertain.

Methods:

A total of 44 patients with a history of unilateral amblyopia (27 patients with persistent amblyopia and 17 patients with resolved amblyopia) were examined using the Heidelberg Retina Tomograph (HRT) II. Parameters examined included disc area, cup area, cup volume, rim area, rim volume, cup-to-disc area ratio, and mean retinal nerve fiber layer thickness.

Results:

In patients with persistent amblyopia, the amblyopic eyes were significantly more hyperopic than the fellow eyes. In the HRT parameters, there were no significant differences between the amblyopic and fellow eyes. In addition, after adjusting for refraction, the presence of strabismus, and the disc area, there was no significant difference in any HRT parameter between the amblyopic eyes of patients with persistent amblyopia and the previously amblyopic eyes of patients with resolved amblyopia.

Conclusions:

We did not find any strong evidence for the deformity of the optic disc of amblyopic eyes.

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

PURPOSE

To evaluate the optic nerve (ON) size and globe shape in amblyopic eyes using high-resolution magnetic resonance imaging (MRI) and to compare these values with those of the sound fellow eye and of normal control eyes.

DESIGN

Prospective case-control study.

METHODS

Thirty-four amblyopic patients and 60 normal control patients were evaluated using surface coil MRI. Retrobulbar ON cross-section, maximum globe cross-section, globe noncircularity (globe major axis/minor axis), axial length (AL), and the ratio of AL to ON (AL/ON) were measured.

RESULTS

Corrected logarithm of the minimum angle of resolution acuity of all 34 amblyopic eyes averaged 0.43 +/- 0.30. The mean retrobulbar ON cross-section was 9.7 +/- 2.4 mm(2), 9.5 +/- 2.3 mm(2), and 10.7 +/- 2.6 mm(2) for amblyopic, fellow, and normal ONs, respectively. Although amblyopic and fellow ONs had similar cross-sections, both were significantly (P = .02) subnormal. AL/ON was 2.7 +/- 1.2 mm(-1), 2.7 +/- 1.0 mm(-1), and 2.3 +/- 0.5 mm(-1), respectively. Although AL/ON significantly exceeded normal in amblyopic eyes (P = .01), there was no significant difference between amblyopic and fellow eyes. Globe noncircularity of amblyopic eyes (1.17 +/- 0.07; P = .002) and fellow eyes (1.15 +/- 0.04; P < .001) was significantly greater than that of control eyes (1.11 +/- 0.04), but amblyopic and fellow eyes did not differ significantly.

CONCLUSIONS

Unilateral amblyopia is associated with bilaterally, but also with subclinically hypoplastic ONs, greater than normal AL/ON, and abnormally noncircular globe cross-section. These factors evidently do not determine which of the 2 eyes will become amblyopic. Reduced circularity of amblyopic and fellow eyes may reflect optical causes of amblyopia or bilateral dysregulation of globe shape secondary to amblyopia.

Defining Amblyopia: The Need for a Joint Classification

Recent years have shown an impressive rise in high quality research on amblyopia. Unfortunately, the condition is not sufficiently defined, and consequently different studies have been used different definitions of amblyopia. Aspects in need of consideration include the degree of visual acuity reduction, magnitude of interocular difference in acuity, method of visual acuity testing used, the effect of refractive adaption, the presence of amblyogenic factors, the absence of organic cause and the treat ability of the deficit. Vision scientists worldwide are encouraged to jointly decide on what is, and what is not, amblyopia.

Retinal nerve fiber layer thickness in amblyopic eyes

PURPOSE

To compare the peripapillary retinal nerve fiber layer (RNFL) thickness of amblyopic and fellow eyes. We hypothesized that the RNFL of the amblyopic eye may be thinner.

DESIGN

Prospective, cross-sectional, observational case series.

METHODS

Optical coherence tomography of the peripapillary RNFL thickness of amblyopic and fellow eyes was performed in 37 patients 7 to 12 years of age (mean age +/- standard deviation, 9.2 +/- 1.5 years) with unilateral strabismic, anisometropic, or combined-mechanism amblyopia enrolled in a randomized treatment trial.

RESULTS

Mean global RNFL thickness of the amblyopic and fellow eyes was 111.4 and 109.6 microm, respectively (mean difference, 1.8 microm thicker in the amblyopic eyes; 95% confidence interval, -0.6 to 4.3 microm). The amblyopic eye was 8 microm or more thicker than the fellow eye in 9 patients (24%); the fellow eye was 8 microm or more thicker than the amblyopic eye in 2 patients (5%); and the difference was within test-retest variability (7 microm) in 26 patients (70%).

CONCLUSIONS

Our findings do not indicate that peripapillary RNFL thickness is thinner in eyes with moderate amblyopia compared with their fellow eyes.

Unilateral amblyopia: An optical coherence tomography study

PURPOSE

To determine whether retinal nerve fiber layer thickness (RNFLT), macular thickness (MT), and foveal volume (FV) in patients with unilateral amblyopia differ between the amblyopic and the sound eye.

METHODS

A Humphrey-Zeiss Stratus (OCT3) with software 4.0.3.1 was used to evaluate 40 patients (17 male, 23 female; mean age, 15.2 years; range, 5-56 years) with unilateral amblyopia. Patients were divided into 2 groups: 20 strabismic and 20 anisometropic. Maps of macular thickness and RNFL thickness (3.46) created by the use of optical coherence tomography were applied to calculate FV and MT and RNFLT.

RESULTS

Mean best-corrected visual acuity was +0.3 LogMAR (range, +0.2 to +1.0) in the amblyopic eye. Mean RNFL thickness was not significantly different between eyes in either group. In strabismic amblyopia, mean MT and FV were 5% lower in the sound eye than in the amblyopic eye (MT, 267 microm vs 253 microm, p = 0.005; FV, 2.57 mm(3) vs 2.43 mm(3), p = 0.001). In anisometropic amblyopia, there was no significant difference between eyes in either MT or FV.

CONCLUSIONS

In patients with strabismic amblyopia, the MT and FV were slightly but significantly lower in the sound eye than in the amblyopic eye. The clinical importance of this difference is not known. No such difference was observed in patients with anisometropic amblyopia.

Retinal area and optic disc rim area in amblyopic, fellow, and normal hyperopic eyes: a hypothesis for decreased acuity in amblyopia

PURPOSE

Defects in visual functions in amblyopic eyes may have a neuroretinal explanation. The retinal area to optic disc rim area ratios of hyperopic normal, amblyopic, and fellow eyes were evaluated.

DESIGN

Case-controlled study.

PARTICIPANTS

A total of 293 patients with amblyopia and bilateral hyperopia and 77 non-amblyopic bilaterally hyperopic patients without strabismus.

METHODS

Disc areas were measured using magnification correction formulas developed by Bengtsson and Krakau. Axial lengths were determined by ultrasound biometry or laser interferometry with a Zeiss AOL Master (Carl Zeiss Co., Oberkochen, Germany). The visual area of the retina was calculated using axial length measurements.

MAIN OUTCOME MEASURES

Optic disc rim areas, corrected for magnification, retinal areas, and a derived ratio, retinal area/disc rim area (RetA/DRimA).

RESULTS

The RetA/DRimA for the amblyopic eyes was significantly greater than that of the fellow and normal eyes, indicating that amblyopic eyes have larger retinal receptor areas than fellow or normal eyes. The RetA/DRimA of the fellow eyes was smaller than for the amblyopic but larger than that of the normal eyes. These differences were due to smaller optic disc rim areas in the amblyopic and fellow eyes.

CONCLUSIONS

Amblyopic and their fellow eyes, when compared with normal eyes, have reduced innervations of comparable retinal areas. These differences can be attributed to a paucity of nerve fibers, as indicated by the smaller neuroretinal rim areas.

FINANCIAL DISCLOSURE(S)

The authors have no proprietary or commercial interest in any materials discussed in this article.

Asymmetry in optic disc morphometry as measured by confocal scanning laser ophthalmoscopy in subjects with hyperopic anisometropia

PURPOSE

To determine whether there is an asymmetry in optic nerve head morphometry in subjects with hyperopic anisometropia.

METHODS

Seventeen men and 20 women with a mean age of 31.43 +/- 2.73 (standard error of mean) years underwent a complete eye examination and optic nerve head topography with the Heidelberg Retina Tomograph II (Heidelberg Engineering, GmBH, Heidelberg, Germany). Differences in optic nerve head parameters between anisometropic eyes and fellow eyes were evaluated using the paired-sample t test or Wilcoxon signed rank test and the correlations between refraction, visual acuity, and disc parameters were evaluated with Spearman's correlation coefficient.

RESULTS

The median refractive errors of hyperopic anisometropic and fellow eyes were +4 D (range: +2.0 to +7.50 D) and 0 D (range: 0 to +4 D), respectively. The mean best-corrected visual acuity of the amblyopic eyes was 0.43 +/- 0.25. The mean disc area of the anisometropic eyes (1.69 +/- 0.35 mm2) was significantly smaller than the fellow eyes (2.01 +/- 0.42 mm2) (P < .001). The differences between eyes in mean cup area, rim area, rim volume, and cup shape were statistically significant (P < .05). In aniosmetropic eyes, refractive error (r = -0.406; P = .013) and visual acuity (r = 0.347; P = .035) showed significant correlations with rim area.

CONCLUSION

Hyperopic anisometropia is associated with a remarkable interocular difference in optic disc size and other topographic parameters.

Pervasive ocular anomalies in posterior microphthalmos

BACKGROUND

Posterior microphthalmos is a relatively rare condition that has been reported to coexist with several other ophthalmic conditions. However, to the best of the authors' knowledge, there are no previous reports that have found posterior microphthalmos and refractive, binocular, retinal, and neurologic considerations, along with a possible hereditary component. The following report documents the coexistence of posterior microphthalmos with severe hyperopia, esotropia, macular folds, and optic nerve hypoplasia in a pair of siblings.

CASE REPORT

A 9-year-old Hispanic girl presented for a comprehensive eye examination. Best-corrected visual acuity (VA) was reduced in both eyes with poorer VA in the right eye. Binocular testing found a small angle constant right esotropia (ET). On dilated fundus examination, a peculiar, elevated, dolphin-shaped folding of the macula was identified, the right eye greater than the left eye, that extended toward an anomalous optic nerve head in both eyes (OU), presumed to be a disc hypoplasia. The patient's brother, who also exhibited severe hyperopia and ET, presented with a similar acuity reduction, a nearly identical folded macular appearance, the right eye more so than the left eye, and a probable optic nerve hypoplasia. Pachymetry, ultrasonography, and ocular coherence tomography imaging of both siblings found thickened corneas in the presence of posterior microphthalmos OU and macular folds affecting only the retina, leaving the choroid and sclera unaffected.

CONCLUSIONS

Posterior microphthalmos may exist in the presence of ocular anomalies along with refractive, binocular, retinal, neurologic, and genetic considerations. In this case, optical coherence tomography provided information on the internal morphology of the macular folds, which helped direct the differential diagnosis. The similar presentation among siblings supports a hereditary component that warrants further investigation.

Retinal nerve fiber layer thickness in amblyopic eyes

PURPOSE

To compare the peripapillary retinal nerve fiber layer (RNFL) thickness of sound and amblyopic eyes.

DESIGN

Prospective observational case series.

METHODS

SETTING

Institutional.

STUDY POPULATION

Patients with unilateral strabismic, anisometropic, or combined amblyopia.

OBSERVATION

Fast RNFL analysis with ocular coherence tomography (OCT) of sound and amblyopic eyes.

MEASURE

Mean RNFL thickness.

RESULTS

For the 17 patients (mean age 10.7 years) in whom both eyes were imaged, the mean thickness of the sound eye was 109.2 microm (median 112.7) and of the amblyopic eye was 104.2 microm (median 105.0), and the average difference (sound eye less amblyopic eye) was 5.0 microm (median 3.0) (95% confidence interval -2.3, 12.2, P = .17). The sound eye was 10 microm or more thicker than the amblyopic eye in four patients; the amblyopic eye was 10 microm or more thicker than the sound eye in one patient; and the difference was within 10 microm in 12 patients. Test-retest data were obtained for 23 pairs of sound eyes and 21 pairs of amblyopic eyes, with 75% of the test-retest pairs within 7%.

CONCLUSIONS

We found a small, but not clinically significant, difference in nerve fiber layer (NFL) thickness between amblyopic and sound eyes. Reliability was excellent, with most eyes testing within 7% of the first test.

Amblyopia

Results from recent randomised clinical trials in amblyopia should change our approach to screening for and treatment of amblyopia. Based on the current evidence, if one screening session is used, screening at school entry could be the most reasonable time. Clinicians should preferably use age-appropriate LogMAR acuity tests, and treatment should only be considered for children who are clearly not in the typical range for their age. Any substantial refractive error should be corrected before further treatment is considered and the child should be followed in spectacles until no further improvement is recorded, which can take up to 6 months. Parents and carers should then be offered an informed choice between patching and atropine drops. Successful patching regimens can last as little as 1 h or 2 h a day, and successful atropine regimens as little as one drop twice a week. Intense and extended regimens might not be needed in initial therapy.

Amblyopia prevalence and cigarette smoking by women

The relationship between cigarette smoking by young women and amblyopia in children was investigated in 13 population groups. Two searches were conducted on Medline using the following keywords for the first search: amblyopia, prevalence or incidence, and the names of specific countries. The keywords for the second search were smoking, cigarettes, women and the names of the same specific countries. Relevant articles were reviewed. A positive relationship between the rate of smoking among women and the prevalence of amblyopia in school-aged children and military recruits was found. The Pearson correlation coefficient was 0.73. The occurrence of decreased visual acuity attributed to amblyopia in disparate population groups is directly related to rates of cigarette smoking by young women.

Amblyopia characterization, treatment, and prophylaxis

Amblyopia has a 1.6-3.6% prevalence, higher in the medically underserved. It is more complex than simply visual acuity loss and the better eye has sub-clinical deficits. Functional limitations appear more extensive and loss of vision in the better eye of amblyopes more prevalent than previously thought. Amblyopia screening and treatment are efficacious, but cost-effectiveness concerns remain. Refractive correction alone may successfully treat anisometropic amblyopia and it, minimal occlusion, and/or catecholamine treatment can provide initial vision improvement that may improve compliance with subsequent long-duration treatment. Atropine penalization appears as effective as occlusion for moderate amblyopia, with limited-day penalization as effective as full-time. Cytidin-5'-diphosphocholine may hold promise as a medical treatment. Interpretation of much of the amblyopia literature is made difficult by: inaccurate visual acuity measurement at initial visit, lack of adequate refractive correction prior to and during treatment, and lack of long-term follow-up results. Successful treatment can be achieved in at most 63-83% of patients. Treatment outcome is a function of initial visual acuity and type of amblyopia, and a reciprocal product of treatment efficacy, duration, and compliance. Age at treatment onset is not predictive of outcome in many studies but detection under versus over 2-3 years of age may be. Multiple screenings prior to that age, and prompt treatment, reduce prevalence. Would a single early cycloplegic photoscreening be as, or more, successful at detection or prediction than the multiple screenings, and more cost-effective? Penalization and occlusion have minimal incidence of reverse amblyopia and/or side-effects, no significant influence on emmetropization, and no consistent effect on sign or size of post-treatment changes in strabismic deviation. There may be a physiologic basis for better age-indifferent outcome than tapped by current treatment methodologies. Infant refractive correction substantially reduces accommodative esotropia and amblyopia incidence without interference with emmetropization. Compensatory prism, alone or post-operatively, and/or minus lens treatment, and/or wide-field fusional amplitude training, may reduce risk of early onset esotropia. Multivariate screening using continuous-scale measurements may be more effective than traditional single-test dichotomous pass/fail measures. Pigmentation may be one parameter because Caucasians are at higher risk for esotropia than non-whites.

Optic nerve axons: life and death before birth

In the 2004 Bowman Lecture, I give a panegyric for Sir William Bowman, an estimate of the importance and the epidemiology of anterior visual pathway developmental disorders, followed by a history of the anterior visual system. I review the normal development of the optic nerve and chiasm and the main developmental disorders: Optic Nerve Aplasia, Optic Nerve Hypoplasia and Achiasmia.