The diagnostic accuracy of photopic negative responses evoked by broadband and chromatic stimuli in a clinically heterogeneous population.

PURPOSE: To compare the diagnostic accuracy of the photopic negative response (PhNR) elicited by red-blue (RB) and white-white (WW) stimuli, for detection of retinal ganglion cell (RGC) dysfunction in a heterogeneous clinical cohort. METHODS: Adults referred for electrophysiological investigations were recruited consecutively for this single-centre, prospective, paired diagnostic accuracy study. PhNRs were recorded to red flashes (1.5 cd·s·m-2) on a blue background (10 cd·m-2) and to white flashes on a white background (the latter being the ISCEV standard LA 3 stimulus). PhNR results were compared with a reference test battery assessing RGC/optic nerve structure and function including optical coherence tomography (OCT) retinal nerve fibre layer thickness and mean RGC volume measurements, fundus photography, pattern electroretinography and visual evoked potentials. Primary outcome measures were differences in sensitivity and specificity of the two PhNR methods. RESULTS: Two hundred and forty-three participants were initially enrolled, with 200 (median age 54; range 18-95; female 65%) meeting inclusion criteria. Sensitivity was 53% (95% confidence intervals [CI] 39% to 68%) and 62% (95% CI 48% to 76%), for WW and RB PhNRs, respectively. Specificity was 80% (95% CI 74% to 86%) and 78% (95% CI 72% to 85%), respectively. There was a statistically significant difference between sensitivities (p = 0.046) but not specificities (p = 0.08) of the two methods. Receiver operator characteristic (ROC) area under the curve (AUC) values were 0.73 for WW and 0.74 for RB PhNRs. CONCLUSION: PhNRs to red flashes on a blue background may be more sensitive than white-on-white stimuli, but there is no significant difference between specificities. This study highlights the value and potential convenience of using white-on-white stimuli, already used widely for routine ERG assessment.

Ophthalmological Manifestations of Oculocutaneous and Ocular Albinism: Current Perspectives.

Albinism describes a heterogeneous group of genetically determined disorders characterized by disrupted synthesis of melanin and a range of developmental ocular abnormalities. The main ocular features common to both oculocutaneous albinism (OCA), and ocular albinism (OA) include reduced visual acuity, refractive errors, foveal hypoplasia, congenital nystagmus, iris and fundus hypopigmentation and visual pathway misrouting, but clinical signs vary and there is phenotypic overlap with other pathologies. This study reviews the prevalence, genetics and ocular manifestations of OCA and OA, including abnormal development of the optic chiasm. The role of visual electrophysiology in the detection of chiasmal dysfunction and visual pathway misrouting is emphasized, highlighting how age-associated changes in visual evoked potential (VEP) test results must be considered to enable accurate diagnosis, and illustrated further by the inclusion of novel VEP data in genetically confirmed cases. Differential diagnosis is considered in the context of suspected retinal and other disorders, including rare syndromes that may masquerade as albinism.

WFS1-Associated Optic Neuropathy: Genotype-Phenotype Correlations and Disease Progression.

OBJECTIVE: To evaluate the pattern of vision loss and genotype-phenotype correlations in WFS1-associated optic neuropathy (WON). DESIGN: Multicenter cohort study. METHODS: The study involved 37 patients with WON carrying pathogenic or candidate pathogenic WFS1 variants. Genetic and clinical data were retrieved from the medical records. Thirteen patients underwent additional comprehensive ophthalmologic assessment. Deep phenotyping involved visual electrophysiology and advanced psychophysical testing with a complementary metabolomic study. MAIN OUTCOME MEASURES: WFS1 variants, functional and structural optic nerve and retinal parameters, and metabolomic profile. RESULTS: Twenty-two recessive and 5 dominant WFS1 variants were identified. Four variants were novel. All WFS1 variants caused loss of macular retinal ganglion cells (RGCs) as assessed by optical coherence tomography (OCT) and visual electrophysiology. Advanced psychophysical testing indicated involvement of the major RGC subpopulations. Modeling of vision loss showed an accelerated rate of deterioration with increasing age. Dominant WFS1 variants were associated with abnormal reflectivity of the outer plexiform layer (OPL) on OCT imaging. The dominant variants tended to cause less severe vision loss compared with recessive WFS1 variants, which resulted in more variable phenotypes ranging from isolated WON to severe multisystem disease depending on the WFS1 alleles. The metabolomic profile included markers seen in other neurodegenerative diseases and type 1 diabetes mellitus. CONCLUSIONS: WFS1 variants result in heterogenous phenotypes influenced by the mode of inheritance and the disease-causing alleles. Biallelic WFS1 variants cause more variable, but generally more severe, vision and RGC loss compared with heterozygous variants. Abnormal cleftlike lamination of the OPL is a distinctive OCT feature that strongly points toward dominant WON.

Prospective Study of the Phenotypic and Mutational Spectrum of Ocular Albinism and Oculocutaneous Albinism.

Albinism encompasses a group of hereditary disorders characterized by reduced or absent ocular pigment and variable skin and/or hair involvement, with syndromic forms such as Hermansky-Pudlak syndrome and Chédiak-Higashi syndrome. Autosomal recessive oculocutaneous albinism (OCA) is phenotypically and genetically heterogenous (associated with seven genes). X-linked ocular albinism (OA) is associated with only one gene, GPR143. We report the clinical and genetic outcomes of 44 patients, from 40 unrelated families of diverse ethnicities, with query albinism presenting to the ocular genetics service at Moorfields Eye Hospital NHS Foundation Trust between November 2017 and October 2019. Thirty-six were children (≤ 16 years) with a median age of 31 months (range 2-186), and eight adults with a median age of 33 years (range 17-39); 52.3% (n = 23) were male. Genetic testing using whole genome sequencing (WGS, n = 9) or a targeted gene panel (n = 31) gave an overall diagnostic rate of 42.5% (44.4% (4/9) with WGS and 41.9% (13/31) with panel testing). Seventeen families had confirmed mutations in TYR (n = 9), OCA2, (n = 4), HPS1 (n = 1), HPS3 (n = 1), HPS6 (n = 1), and GPR143 (n = 1). Molecular diagnosis of albinism remains challenging due to factors such as missing heritability. Differential diagnoses must include SLC38A8-associated foveal hypoplasia and syndromic forms of albinism.

Juvenile Batten Disease (CLN3): Detailed Ocular Phenotype, Novel Observations, Delayed Diagnosis, Masquerades, and Prospects for Therapy.

PURPOSE: To characterize the retinal phenotype of juvenile neuronal ceroid lipofuscinosis (JNCL), highlight delayed and mistaken diagnosis, and propose an algorithm for early identification. DESIGN: Retrospective case series. PARTICIPANTS: Eight children (5 female) with JNCL. METHODS: Review of clinical notes, retinal imaging including fundus autofluorescence and OCT, electroretinography (ERG), and both microscopy and molecular genetic testing. MAIN OUTCOME MEASUREMENTS: Demographic data, signs and symptoms, visual acuity (VA), fundus autofluorescence and OCT findings, ERG phenotype, and microscopy/molecular genetics. RESULTS: Participants presented with rapid bilateral vision loss over 1 to 18 months, with mean VA deteriorating from 0.44 logarithm of the minimum angle of resolution (logMAR) (range, 0.20-1.78 logMAR) at baseline to 1.34 logMAR (0.30 logMAR - light perception) at last follow-up. Age of onset ranged from 3 to 7 years (mean, 5.3 years). The age at diagnosis of JNCL ranged from 7 to 10 years (mean, 8.3 years). Six children displayed eccentric fixation, and 6 children had cognitive or neurologic signs at the time of diagnosis (75%). Seven patients had bilateral bull's-eye maculopathy at presentation. Coats-like exudative vasculopathy, not previously reported in JNCL, was observed in 1 patient. OCT imaging revealed near complete loss of outer retinal layers and marked atrophy of the nerve fiber and ganglion cell layers at the central macula. An electronegative ERG was present in 4 patients (50%), but with additional a-wave reduction, there was an undetectable ERG in the remaining 4 patients. Blood film microscopy revealed vacuolated lymphocytes, and electron microscopy showed lysosomal (fingerprint) inclusions in all 8 patients. CONCLUSIONS: In a young child with bilateral rapidly progressive vision loss and macular disturbance, blood film microscopy to detect vacuolated lymphocytes is a rapid, readily accessible, and sensitive screening test for JNCL. Early suspicion of JNCL can be aided by detailed directed history and high-resolution retinal imaging, with subsequent targeted microscopy/genetic testing. Early diagnosis is critical to ensure appropriate management, counseling, support, and social care for children and their families. Furthermore, although potential therapies for this group of disorders are in early-phase clinical trial, realistic expectations are that successful intervention will be most effective when initiated at the earliest stage of disease.

Isolated rod dysfunction associated with a novel genotype of CNGB1.

PURPOSE: To describe the clinical and electrophysiological features of an unusual retinopathy in a patient with a novel genotype of CNGB1, mutations in which are implicated in autosomal recessive retinitis pigmentosa (rod-cone dystrophy). OBSERVATIONS: A 61-year old asymptomatic woman was referred to the inherited retinal disorders clinic because of peripheral retinal pigmentary changes. She had normal visual acuity and color vision. Clinical examination and detailed imaging of the macula were normal, but there was atrophy of the outer retina in the periphery with sparse intra-retinal pigmentation. Electroretinography (ERG) revealed undetectable rod responses, with normal cone-mediated responses. The pattern ERG was normal. Genetic analysis identified two previously unreported variants in CNGB1: (c.2258T > A, p.[Leu753*] and c.807G > C, p.[Gln269His]), shown to be in trans. CONCLUSIONS AND IMPORTANCE: This report describes a functionally cone-isolated retina in an adult, apparently hemizygous for a novel missense mutation in CNGB1, a novel phenotype for this gene. The p.[Gln269His] allele is the first missense change, within the glutamic acid-rich protein (GARP) domain of CNGB1, to be associated with retinal disease in humans.

Unilateral Pigmented Paravenous Retinochoroidal Atrophy Associated With Presumed Ocular Tuberculosis.

This report describes a case of unilateral pigmented paravenous retinochoroidal atrophy (PPRCA) in a patient with low-grade unilateral intermediate uveitis. A 31-year-old woman, previously diagnosed with intermediate uveitis in the right eye (OD) presented to the clinic. Best-corrected visual acuity was 20/20 OD. Fundus examination, fluorescein angiography, autofluorescence, and optical coherence tomography OD were in keeping with a phenotypic diagnosis of PPRCA. Electrophysiology showed severe photoreceptor dysfunction of both the rod and the cone systems OD. Systemic workup revealed QuantiFERON-gold positive. This is the first report of unilateral PPRCA secondary to presumed ocular tuberculosis. [Ophthalmic Surg Lasers Imaging Retina. 2017;48:345-349.].

A randomized trial to assess functional and structural effects of ranibizumab versus laser in diabetic macular edema (the LUCIDATE study).

PURPOSE: To compare the functional and structural effects of ranibizumab versus macular laser therapy in patients with center-involving diabetic macular edema. DESIGN: Prospective, randomized, single-masked clinical trial. SETTING: Single center. STUDY POPULATION: Thirty-three eyes of 33 patients with center-involving diabetic macular edema, with best corrected visual acuity of 55 to 79 Early Treatment Diabetic Retinopathy Study letters at baseline, completing the 48-week study period. INTERVENTION: Subjects were randomized 2:1 to 3 loading doses of ranibizumab then retreatment every 4 weeks as required; or macular laser therapy at baseline, repeated as required every 12 weeks. Exploratory Outcome Measures: Structural imaging studies included greatest linear dimension and area of foveal avascular zone, perifoveal capillary dropout grade, and presence of morphologic features of diabetic macular edema on Spectralis optical coherence tomography (Heidelberg Engineering GmbH, Heidelberg, Germany). Functional measures: Visual acuity, retinal sensitivity in the central 4 and 12 degrees on microperimetry, color contrast sensitivity protan and tritan thresholds, pattern and full-field electroretinogram amplitudes and implicit times, and multifocal electroretinogram amplitude distribution. These were reported at 12, 24, and 48 weeks. RESULTS: Ranibizumab-treated subjects gained 6.0 vs 0.9 letters lost for laser, demonstrated improved tritan and protan color contrast thresholds, and improved retinal sensitivity. Electrophysiologic function also improved after ranibizumab therapy. No safety issues were evident. Better retinal thickness reduction and structural improvement in optical coherence tomography features of diabetic macular edema were seen with ranibizumab therapy than in the laser group. There was no evidence of progressive ischemia with ranibizumab therapy. CONCLUSIONS: Ranibizumab therapy in the treatment of diabetic macular edema seems to improve retinal function and structure as demonstrated by this evaluation of different assessment methods.

A phenotype-genotype correlation study of X-linked retinoschisis.

PURPOSE: To compare the clinical phenotype and detailed electroretinographic parameters in X-linked retinoschisis (XLRS). DESIGN: Retrospective, comparative study. PARTICIPANTS: Fifty-seven patients (aged 1-67 years) with molecularly confirmed XLRS were clinically ascertained. METHODS: Pattern electroretinography (PERG) and full-field electroretinography (ERG), incorporating international standard recordings, were performed in 44 cases. Thirteen patients, mostly pediatric, were tested using a simplified ERG protocol. On-Off and S-cone ERGs were performed in most adults. Fundus autofluorescence (FAF) imaging and optical coherence tomography (OCT) were available in 17 and 21 cases, respectively. MAIN OUTCOME MEASURES: The clinical and electrophysiologic data associated with different types of mutation in the RS1 gene. RESULTS: Forty-three patients had missense changes (group A), and 14 patients had nonsense, splice-site, or frame-shifting mutations in the RS1 gene (group B). The mean best-corrected visual acuity was better in group A than in group B (0.34 and 0.21, respectively). Fundus examination revealed foveal schisis in approximately half of both groups. The bright-flash dark-adapted (DA) ERG (11.0 candela.sec.m(-2)) waveform was electronegative in 62% of group A eyes and 100% of group B eyes. The photopic 30-Hz flicker ERG was delayed in all group B eyes and all except 6 group A eyes. On-Off ERG b-waves were subnormal in 39% of group A and 89% of group B eyes; d-waves were delayed in 14 eyes (group A = 10, group B = 4). S-cone ERGs were abnormal in 50% of both groups. The PERG was abnormal in 88% of group A and 100% of group B eyes. A spoke-wheel pattern of high and low intensity was the most common FAF abnormality observed. The OCT showed intraretinal schitic cavities in the majority of eyes. CONCLUSIONS: There is profound phenotypic variability in patients with XLRS. Most patients have DA bright-flash ERGs with a low b:a ratio in keeping with inner retinal dysfunction. Generalized cone system dysfunction is common and associated with an abnormal On-response and less frequent additional Off-response involvement. Nonsense, splice-site, or frame-shifting mutations in RS1 consistently caused electronegative bright-flash ERG, delayed flicker response, and abnormal PERG; missense mutations result in a wider range of ERG abnormalities.

Electroretinogram measures in a septuagenarian population.

This study reports electroretinogram (ERG) data in a septuagenarian population. Fifty healthy adults without diabetes or dementia aged 70-79 years underwent standardised electrophysiological testing incorporating current ISCEV Standards as baseline assessment for the OPAL (Older People And n-3 Long-chain polyunsaturated fatty acids) study. These data were compared with those from 53 healthy adults aged 20-50 years. Amplitudes and peak times of the major components were assessed. There were no significant differences in amplitude or peak time between sexes or between eyes. ERG amplitudes were 25-40% smaller and peak-times were longer in the older compared with the younger age group. In all participants, the bright flash ERG b-wave amplitude had the highest variability; the bright flash ERG a-wave peak time had the lowest. ERGs in a septuagenarian age group show 25-40% lower amplitude than those of a 20 to 50-year-old group and are of longer peak time. With an increasingly ageing population involved in clinical trials, and the potential use of ERG in the assessment both of efficacy and safety in forthcoming therapeutic interventions, it is important that the effects of age are given adequate consideration.

Deficits in local and global motion perception arising from abnormal eye movements.

Albino mammals exhibit a range of visual deficits including disrupted hemispheric pathways, an underdeveloped central retina, and nystagmus. Recently, it has been reported that albino animals also show deficits in the processing of visual motion, exhibiting higher motion coherence thresholds (MCTs; the proportion of coherently moving elements within a field of randomly moving distracters required to reliably report direction). Here we compare MCTs-collected from human observers with albinism-with an equivalent noise analysis of their fine-direction discrimination and report that their loss in motion sensitivity operates at both the level of local motion processing (of small objects) and at the later stage of global motion pooling. We also compare results from observers with aniridia (characterized by underdeveloped central retina and nystagmus but normal hemispheric visual pathways) and a rare group of observers with albinism who show no nystagmus. For the observers tested, nystagmus proved to be a common feature of individuals showing elevated MCTs. Since it is likely that motion perception is influenced by environmental factors early in development we postulate that the effect of congenital nystagmus on the temporal structure of the natural visual diet disrupts the ability of motion pathways to form normally.

Clinicopathological case series of four patients with inherited macular disease.

PURPOSE: To correlate the phenotype of four patients with inherited macular disease with the immunohistopathology of retinal tissue collected at the time of retinal pigment epithelium (RPE)-choroidal transplantation. METHODS: A clinicopathologic case series describing the phenotype of four patients, including confocal immunohistochemistry and electron microscopy (EM), and the results of genetic testing. RESULTS: In Case 1, electrophysiology showed only macular dysfunction. Confocal microscopy revealed minor abnormalities. EM showed abnormal cone inner segments with swollen mitochondria. In case 2 (R172W mutation in RDS), electrophysiology demonstrated generalized cone system dysfunction with severe macular involvement. Peripherin labeling of outer segments was nonuniform, and EM showed discs arranged in whorllike structures. Case 3 showed severe central macular dysfunction on multifocal electroretinogram (ERG). Peripherin staining was irregular and disorganized. EM revealed abnormal inner segment morphology, particularly in rods, and disorganized irregular outer segments. Case 4 had localized central macular dysfunction on multifocal ERG. Confocal microscopy was grossly normal, with evidence of early redistribution of cone opsin to the inner segment. EM showed variable rod morphology and normal cones. CONCLUSIONS: RPE transplantation provides a unique opportunity to gain insight into retinal disorders by enabling phenotypic correlation with the immunohistopathology of retinal tissue collected during surgery.

Differential changes in color and motion-onset visual evoked potentials from both eyes in early- and late-onset strabismic amblyopia.

PURPOSE: To examine changes in color- and motion-related visual function in patients with strabismic amblyopia. METHODS: Motion-onset and color visual-evoked potentials (VEPs) were recorded in 16 adult patients with strabismic amblyopia which had an early onset, before 18 months of age, and 14 patients with amblyopia of later onset. The results are compared with those from 21 normal adults. RESULTS: The peak times of motion-onset VEPs in the amblyopic eye were longer those than in the fellow eye in patients with both early- and late-onset strabismic amblyopia, but peak times in both amblyopic and fellow eyes were shorter than those in normal eyes. In patients with late- but not early-onset amblyopia, the peak times for color VEPs were significantly longer in amblyopic than in fellow and normal eyes. CONCLUSIONS: The patterns of abnormality for motion-onset and color VEPs in patients with strabismic amblyopia are different, probably indicating differential changes in function in magno- and parvocellular pathways. These abnormalities affect both the amblyopic and fellow eyes and are different in patients with an onset of amblyopia before or after 18 months of age.

Phenotypic variation in enhanced S-cone syndrome.

PURPOSE: To characterize the clinical, psychophysical, and electrophysiological phenotype of 19 patients with enhanced S-cone syndrome (ESCS) and relate the phenotype to the underlying genetic mutation. METHODS: Patients underwent ophthalmic examination and functional testing including pattern ERG, full-field ERG, and long-duration and short-wavelength stimulation. Further tests were performed in some patients, including color contrast sensitivity (CCS), multifocal ERG, fundus autofluorescence imaging (FAI), optical coherence tomography (OCT), and fundus fluorescein angiography (FFA). Mutational screening of NR2E3 was undertaken in 13 patients. RESULTS: The fundus appearance was variable, from normal to typical nummular pigment clumping at the level of the retinal pigment epithelium in older patients. Nine patients had foveal schisis, and one had peripheral schisis. Pattern ERG was abnormal in all patients. In all patients, ISCEV Standard photopic and scotopic responses had a similar waveform, the rod-specific-ERG was undetectable and the 30-Hz flicker ERG was markedly delayed with an amplitude lower than the photopic a-wave. Most ERG responses arose from short-wavelength-sensitive mechanisms, and a majority of patients showed possible OFF-related activity. Multifocal ERG showed relative preservation of central function, but reduced responses with increased eccentricity. Mutations were identified in NR2E3 in 12 of 13 patients including four novel variants. CONCLUSIONS: The phenotype in ESCS is variable, both in fundus appearance and in the severity of the electrophysiological abnormalities. The ERGs are dominated by short-wavelength-sensitive mechanisms. The presence, in most of the patients, of possible OFF-related ERG activity is a finding not usually associated with S-cones.

Mutations in BMP4 cause eye, brain, and digit developmental anomalies: overlap between the BMP4 and hedgehog signaling pathways.

Developmental ocular malformations, including anophthalmia-microphthalmia (AM), are heterogeneous disorders with frequent sporadic or non-Mendelian inheritance. Recurrent interstitial deletions of 14q22-q23 have been associated with AM, sometimes with poly/syndactyly and hypopituitarism. We identify two further cases of AM (one with associated pituitary anomalies) with a 14q22-q23 deletion. Using a positional candidate gene approach, we analyzed the BMP4 (Bone Morphogenetic Protein-4) gene and identified a frameshift mutation (c.226del2, p.S76fs104X) that segregated with AM, retinal dystrophy, myopia, brain anomalies, and polydactyly in a family and a nonconservative missense mutation (c.278A-->G, p.E93G) in a highly conserved base in another family. MR imaging and tractography in the c.226del2 proband revealed a primary brain developmental disorder affecting thalamostriatal and callosal pathways, also present in the affected grandmother. Using in situ hybridization in human embryos, we demonstrate expression of BMP4 in optic vesicle, developing retina and lens, pituitary region, and digits strongly supporting BMP4 as a causative gene for AM, pituitary, and poly/syndactyly. Because BMP4 interacts with HH signaling genes in animals, we evaluated gene expression in human embryos and demonstrate cotemporal and cospatial expression of BMP4 and HH signaling genes. We also identified four cases, some of whom had retinal dystrophy, with "low-penetrant" mutations in both BMP4 and HH signaling genes: SHH (Sonic Hedgehog) or PTCH1 (Patched). We propose that BMP4 is a major gene for AM and/or retinal dystrophy and brain anomalies and may be a candidate gene for myopia and poly/syndactyly. Our finding of low-penetrant variants in BMP4 and HH signaling partners is suggestive of an interaction between the two pathways in humans.

The fovea regulates symmetrical development of the visual cortex.

The foveal region contains the highest cell density in the human retina; consequently a disproportionately large area of the visual cortex is dedicated to its representation. In aniridia and albinism the fovea does not develop, and the corresponding cortical representation shows a reduction in gray matter volume. In albinos there are chiasmatic irregularities in the hemispheric projections, which are not found in aniridics. Here, we ask whether the anomalies in central retinal development, present in albinism and aniridia, have a wider impact on the architecture of the visual cortex. The length, depth, and topology of the calcarine fissure is analyzed in albino, aniridic, and normal subjects. These measures are compared between groups and between the cortical hemispheres within each subject. We show that the calcarine fissure, where the primary visual cortex is represented, is abnormally short in those lacking a fovea. Moreover, surface reconstructions of the calcarine fissure revealed marked interhemispheric asymmetries. The two groups could not be distinguished on the basis of their cortical features, and we therefore interpret the abnormalities in cortical architecture in terms of the absence of the fovea, the common retinal feature found in both groups.

Differential changes of magnocellular and parvocellular visual function in early- and late-onset strabismic amblyopia.

PURPOSE: Studies in nonhuman primates show that monocular visual deprivation starting at different ages has different effects on cells in the parvocellular and magnocellular laminae of the lateral geniculate nucleus. The present study used color and luminance contrast sensitivity (CS) measurements to look for differences in parvocellular- and magnocellular-related visual function in human subjects with strabismic amblyopia. METHODS: Fifteen subjects with early- and 14 with late-onset strabismic amblyopia and similar ranges of visual acuity were studied, together with 15 subjects with normal vision. Contrast sensitivities were measured to an equiluminant (L-M cone-modulated) grating with slow onset and an achromatic (L+M cone-modulated) 0.8-cpd grating with rapid onset using an adaptive RESULTS: Luminance and color CS were lower in the amblyopic eyes than in the fellow eyes of all amblyopes. For luminance CS, this was due both to an increase in sensitivity of the fellow eye and to a reduction in sensitivity in the amblyopic eye. Color CS was greatly reduced in the amblyopic and fellow eyes of subjects with strabismic amblyopia of early- and late onset compared with subjects with normal vision. The reduction in color CS compared with luminance CS was significantly greater in eyes with late- rather than early-onset amblyopia. CONCLUSIONS: Parvocellular and magnocellular function are differentially affected in the amblyopic and fellow eyes of subjects with strabismic amblyopia. The difference is more marked in late-onset amblyopia than in early-onset amblyopia.

A comparison of pattern and multifocal electroretinography in the evaluation of age-related macular degeneration and its treatment with photodynamic therapy.

This study compares pattern electroretinography (PERG) and multifocal electroretinography (mfERG) measures in 13 patients with predominantly classic choroidal neovascularisation (CNV) associated with age-related macular degeneration (ARMD, 9/13 unilateral, 4/13 bilateral), assesses the usefulness of each test in monitoring disease progression, and identifies electrophysiological predictors of outcome following treatment with photodynamic therapy (PDT). PERG and mfERGs were recorded at presentation, 2 weeks post-treatment, and at 3 monthly intervals for 2 years. The PERG was detectable in 8/13 patients with unilateral disease; the mfERG was detectable in 12/13 patients. P50 and N95 amplitudes increased in 6/8 patients and mfERG p1 increased in 7/13 patients at 2 years. PERG amplitudes correlated strongly with mfERG amplitudes in patients with unilateral disease. PERG P50 and mfERG p1 amplitude correlated with visual acuity at 2 years (R = 0.68, R = 0.82, respectively). The largest PERG P50 and mfERG p1 amplitude difference between treated and fellow eyes of all the groups on initial visit was associated with a poor visual outcome (P50 64% difference; p1 29% difference) whereas those with the smallest P50 and p1 amplitude difference was associated with improved vision at 2 years (P50 30% difference; p1 21% difference). The PERG and mfERG provide an objective measure of central retinal function in the progression of ARMD. A detectable PERG on presentation was the single best indicator of improved function and visual acuity at 2 years. The mfERG demonstrated disease progression from central retina into the paramacular regions over 2 years. Patients with poor visual outcomes had the largest inter-ocular amplitude difference on presentation, suggesting that such patients may have a worse prognosis following treatment.

Early midline interactions are important in mouse optic chiasm formation but are not critical in man: a significant distinction between man and mouse.

The optic chiasm is one of the most popular models for studying axon guidance. Here axons make a key binary decision either to cross the midline to innervate the contralateral hemisphere or to remain uncrossed. In rodents, midline interactions between axons from the two eyes are critical for normal development, as early removal of one eye systematically disrupts hemispheric projections from the remaining eye, increasing the crossed projection at the expense of the uncrossed. This is similar to the abnormal decussation pattern seen in albinos. This pattern is markedly different in marsupials where early eye removal has no impact on projections from the remaining eye. These differences are related to the location of the uncrossed projection through the chiasm. In rodents these axons approach the midline whereas in marsupials they remain segregated laterally. We provide anatomical evidence in man suggesting that, unlike in rodents, uncrossed axons are confined laterally and do not mix in each hemi-chiasm, which is a pattern similar to that found in marsupials. Further, we demonstrate electrophysiologically, using visual cortical evoked potentials, that the failure of one eye to develop in man has no impact on the hemispheric projections from the remaining eye. These data demonstrate that the mechanisms regulating chiasmal development in man differ from those in rodents but may be similar to those in marsupials. We suggest that mouse models of the organization and development of the optic chiasm are not common to placental mammals in general.