[Chorioretinal atrophy in pediatric cerebral folate deficiency-a preventable disease?] / Chorioretinale Atrophie bei kindlichem zerebralem Folatmangel ­ eine vermeidbare Erkrankung?

Cerebral folate deficiency (CFD) results in neurological alterations and a massive degeneration of the choroid/retina if left untreated, which limit the visual field and visual acuity. This article reports the case of a female patient with CFD, who developed autistic personal characteristics prior to reaching school age and first started to speak at the age of 3 years. At the age of 6 years she was presented because of unclear reduced visual acuity in the right eye. At that time mild bilateral peripheral chorioretinal atrophy was present, which subsequently became more pronounced. Additionally, a centrally emphasized chorioretinal atrophy further developed. Visual acuity of both eyes progressively deteriorated until stagnating at 0.1 at the age of 14 years. The causal assignment of the findings of the patient was not possible for many years. Choroideremia was excluded by molecular genetic testing (CHM gene with no mutations) and gyrate atrophy was ruled out by a normal ornithine level. The existence of a mitochondrial disease was almost completely excluded by exome sequencing. After the onset of further nonocular symptoms, e.g. neuromuscular disorders, electroencephalograph (EEG) alterations and autistic disorder, intensified laboratory diagnostics were performed in the treating pediatric hospital. Finally, an extremely low level of the folic acid metabolite 5­methyltetrahydrofolate was detected in the cerebrospinal fluid (CSF) leading to the diagnosis of CFD. High-dose substitution treatment with folic acid was subsequently initiated. After excluding the presence of a pathogenic mutation of the FOLR1 gene for the cerebral folate receptor 1, a high titer blocking autoantibody against cerebral folate receptor 1 was detected as the cause.

Unexpected Genetic Cause in Two Female Siblings with High Myopia and Reduced Visual Acuity.

In daily life, myopia is a frequent cause of reduced visual acuity (VA) due to missing or incomplete optical correction. While the genetic cause of high myopia itself is not well understood, a significant number of cases are secondary to hereditary malfunctions or degenerations of the retina. The mechanism by which this occurs remains yet unclear. Two female siblings, 4 y and 2 y, respectively, from a consanguineous Pakistani family were referred to our department for reduced VA and strabismus. Both girls were highly myopic and hence were further examined using standard clinical tests and electroretinography (ERG). The latter confirmed confounded electrical coupling of photoreceptors and bipolar cells. Further inquiry and testing confirmed a similar condition for the father including impaired night vision, reduced VA, photophobia, and an equally characteristic ERG. Findings in the mother were unremarkable. Subsequent genetic analysis of autosomal recessive and X-linked genes for congenital stationary night blindness (CSNB) revealed a novel homozygous splice site mutation in CACNA1F in the two girls transmitted from both the father and the mother. While in males the above clinical constellation is a frequent finding, this report, to the authors' knowledge, is the first demonstrating biallelic mutations at the CACNA1F locus in females.

Correlation of central visual function and ROP risk factors in prematures with and without acute ROP at the age of 6-13†years: the Giessen long-term ROP study.

AIM: To correlate light increment sensitivity (LIS) and visual acuity (VA) with birth weight (BW), gestational age (GA) and stage of acute retinopathy of prematurity (ROP) (STG) in premature children at school age. METHODS: 180 children (150 former prematures and 30 age-matched term-born children) were enrolled at age 6-13 years. Former prematures were categorised by the results of the initial ROP screening based on digital wide-field fundus imaging: absence of ROP (n=100) and spontaneously resolved ROP (n=50). The latter group was further subdivided according to their STG (Stg 1; Stg 2; Stg 3). Both groups were categorised into sectors by BW (<1000 g; 1000-1500 g; >1500 g), and GA (≤28 weeks; >28<32 weeks; ≥32 weeks). VA was assessed with Early Treatment of Diabetic Retinopathy Study letters, LIS was measured at 0°, 2.8° and 8° in the visual field (Microperimeter MP1, Nidek Technologies), and spherical equivalent refraction assessed with a Nidek autorefractor (Nidek, Italy). RESULTS: Central and pericentral LIS (0° and 2.8°) and VA were significantly lower in all groups and sectors compared with term-born controls except for BW >1500 g for LIS and GA >28 to <32 W for VA. No significant differences were found for LIS at 8° in all groups. No correlation was found between LIS and VA on an individual basis. CONCLUSIONS: Low BW, GA and increasing severity of spontaneously resolving ROP were associated with significantly decreased central visual function. In addition to VA, LIS measurement further describes foveal function and is a unique parameter to assess parafoveal function.

[Autosomal recessive bestrophinopathy (ARB): a clinical and molecular description of two patients at childhood]. / Autosomal-rezessive Bestrophinopathie (ARB): klinische und molekulare Beschreibung zweier Patienten im Kindesalter.

BACKGROUND: Autosomal recessive bestrophinopathy (ARB) is associated with mutations in BEST1. ARB is rarely diagnosed compared to BEST1-associated autosomal dominant (a. d.) juvenile vitelliform macular degeneration (Morbus Best, VMD). This is not only due to its low prevalence, but also to the phenotypic appearance. This paper describes typical features in two patients and discusses novel findings using improved ophthalmological diagnostic tools. MATERIAL AND METHODS: Two unrelated boys with reduced visual acuity as well as five further relatives underwent a comprehensive ophthalmological examination including electroretinography (ERG) and electrooculography (EOG) according to ISCEV standard, fundus autofluorescence (FAF) and spectral-domain optic coherence tomography (SD­OCT). BEST1 was screened for mutations based on the clinical diagnosis. RESULTS: Visual acuity ranged between 0.2 and 0.5 in the patients. Multifocal yellowish paramacular and peripheral lesions were visible in the fundus correlating with spots of increased FAF. The lesions correlated with thickening of the RPE layer. Especially in the inner nuclear layer hyporeflective areas were visible, reminiscent of retinoschisis but without changes of FAF. In both patients the ganzfeld ERG was within the normal range and the mfERG presented obvious reductions of amplitudes in the central area. The EOG did not show a light peak. Goldmann perimetry was normal for isopters III/4e and I/4e. The fundus controlled perimetry revealed a central sensitivity loss. Molecular genetic analysis identified four (two novel) mutations in BEST1, in the compound heterozygous state in both patients. The screened relatives carried one of the mutations in the heterozygous state and were ophthalmologically unremarkable apart from age-related changes. CONCLUSION: ARB is a rare disease, presenting with obvious differences to a.d. Mobus Best. The phenotype can easily be identified by the extramacular multifocal yellowish lesions with increased FAF and accompanied by early loss of visual acuity. Specific diagnostic tests like OCT, FAF recordings and electrophysiology support the diagnosis. Molecular genetic screening confirms the diagnosis and the autosomal recessive inheritance.

[Blind spot enlargement syndrome in acute zonal occult outer retinopathy with detection of autoantibodies against the retinal antigens CRALBP and S-Ag]. / Syndrom der Vergrößerung des blinden Flecks in akuter zonaler okkulter äußerer Retinopathie mit Nachweis von Autoantikörpern gegen die retinalen Antigene CRALBP und S-Ag.

Acute zonal occult outer retinopathy (AZOOR) is a rare disease and is part of the white dot syndrome occurring bilaterally and often asymmetrically in young healthy myopic women. Characteristic findings are distinct focal lesions of the outer segments (OS) of the photoreceptor (PR) layer and abnormalities in fundus autofluorescence (FAF) within the lesions. Currently there is a lack of defined disease criteria, such as specific laboratory findings. Also no effective therapy is known which makes it difficult to diagnose, differentiate and treat AZOOR. Supplementation of antioxidants may become part of therapeutic options in AZOOR. A 19-year-old myopic woman presented with unilaterally reduced visual acuity. Due to the clinical features and with the help of FAF, spectral domain optical coherence tomography (SD-OCT) and perimetry the diagnosis of blind spot enlargement syndrome in AZOOR was made. Identification of autoantibodies specific for two retinal antigens (CRALBP and S-Ag) supports the concept of an autoimmunological origin of the disease. Systemic steroids were given but stopped almost 6 weeks later as no improvement was seen. In follow-up controls over 12 months the clinical picture remained unchanged without any further therapy.

[Genetic and clinical heterogeneity in LCA patients. The end of uniformity]. / Genetische und klinische Heterogenität bei LCA-Patienten. Das Ende der Einheitlichkeit.

BACKGROUND: Leber congenital amaurosis (LCA) usually describes patients with severely reduced vision due to a retinal dystrophy in early childhood. METHODS: In 135 families in a case series with severely reduced vision due to a retinal dystrophy in early childhood a complete ophthalmologic examination was extended by two-color threshold perimetry, fundus autofluorescence (FAF), und optical coherence tomography (OCT). Mutation screening included AIPL1, CRB1, CRX, GUCY2D, LRAT, RPE65, RPGRIP, and TULP1. RESULTS: GUCY2D mutations caused the most severe phenotype with severely reduced vision from birth but unremarkable fundus appearance. RPE65 mutations were correlated with an obvious lack of FAF. CRB1 mutations showed a significantly thickened retina on OCT. CRX mutations were associated with a progressive form of cone-rod dystrophy. CONCLUSION: A genotype-phenotype correlation for selected genes allows an optimized strategy for the molecular genetic work-up.

[Seeing in the dusk: physiological basis and investigation]. / Sehen in der Dämmerung: Physiologische Grundlagen und Untersuchungsmethoden.

Dark adaptation and seeing in the dusk require a complex interaction of the cone and rod system. Whereas the former provides high temporal resolution and colour vision in daylight, temporal resolution of the latter is smaller but sensitivity higher by a factor of 100 to 1,000. The two operational ranges overlap by several decades. Characteristic symptoms of disease may be derived from the systems' physiological function and should be enquired about specifically. Problems due to opacity of the optic media or reduced visual acuity should be differentiated from night vision disorders in the more specific sense. Apart from a routine ophthalmological examination a set of other tests should be used: When rods function normally the second limb of the dark adaptation curve initiates at 5 - 12 min und reaches a normal absolute threshold after 30 - 40 min; dark adapted visual fields are unrestricted apart from a physiological central scotoma, and the dark adapted electroretinogram (ERG) shows normal amplitudes and latencies for low intensity flashes. The influence of glare on mesopic contrast sensitivity may be investigated with a mesoptometer. Night vision disorders may arise from cone system dysfunction, too. Intact cone vision provides high visual acuity, normal colour vision, normal photopic visual fields, a quick regeneration within minutes during the first limb of the dark adaptation curve and normal single flash and oscillatory potentials in the light-adapted ERG. Localised defects may be detected using the multifocal ERG. Interpretation of the results must account for the age-related decay of contrast sensitivity and speed of adaptation.

Contribution of cone photoreceptors and post-receptoral mechanisms to the human photopic electroretinogram.

We recorded the electroretinogram (ERG) from human subjects with normal vision, using ganzfeld stimulation in the presence of rod-suppressing blue background light. In families of responses to flashes of increasing intensity, we investigated features of both receptoral and post-receptoral origin. Firstly, we found that the oscillatory potentials (OPs, that have long been known to be post-receptoral) exhibited a time course that was invariant over a range of bright flash intensities. Secondly, we found that the photopic b-wave (which probably originates in cone ON bipolar cells) was most pronounced after test flashes of around 20 Td s, and could be suppressed either by increasing the test flash intensity or by applying a second flash after the test flash. We obtained estimates of the time course of the cone photoreceptor response using the paired-flash technique, in which an intense 'probe' flash was delivered at different times after a test flash. The response to the probe flash was recorded and, its amplitude was measured at early times after the probe flash. Estimates obtained in this way were of normalized amplitude, but could be scaled to an absolute amplitude by making an assumption about the level of probe-flash response that corresponded to complete suppression of photoreceptor current. For moderately bright test flashes the estimated cone photoreceptor response at early times coincided closely with the a-wave of the test flash ERG. However, the maximal size of this estimated response accounted for only about 70% of the peak a-wave amplitude in the case of bright flashes, and for an even smaller proportion after flashes of lower intensity, and we take this to indicate the existence of a third substantial post-receptoral contribution to the a-wave. For dim flashes, the time-to-peak of the cone response was around 15-20 ms, and for saturating flashes the dominant time constant of recovery was about 18 ms. The intensity dependence of the estimated cone response amplitude at fixed times followed an exponential saturation relation. We provide a comparison between our estimates of photoreceptor responses from human cones, and recent estimates from monkey cones obtained using related ERG approaches, and earlier single-cell measurements from isolated primate cones.

New views on RPE65 deficiency: the rod system is the source of vision in a mouse model of Leber congenital amaurosis.

Leber congenital amaurosis (LCA) is the most serious form of the autosomal recessive childhood-onset retinal dystrophies. Mutations in the gene encoding RPE65, a protein vital for regeneration of the visual pigment rhodopsin in the retinal pigment epithelium, account for 10-15% of LCA cases. Whereas previous studies of RPE65 deficiency in both animal models and patients attributed remaining visual function to cones, we show here that light-evoked retinal responses in fact originate from rods. For this purpose, we selectively impaired either rod or cone function in Rpe65-/- mice by generating double- mutant mice with models of pure cone function (rhodopsin-deficient mice; Rho-/-) and pure rod function (cyclic nucleotide-gated channel alpha3-deficient mice; Cnga3-/-). The electroretinograms (ERGs) of Rpe65-/- and Rpe65-/-Cnga3-/- mice were almost identical, whereas there was no assessable response in Rpe65-/-Rho-/- mice. Thus, we conclude that the rod system is the source of vision in RPE65 deficiency. Furthermore, we found that lack of RPE65 enables rods to mimic cone function by responding under normally cone-isolating lighting conditions. We propose as a mechanism decreased rod sensitivity due to a reduction in rhodopsin content to less than 1%. In general, the dissection of pathophysiological processes in animal models through the introduction of additional, selective mutations is a promising concept in functional genetics.

Time course of the flash response of dark- and light-adapted human rod photoreceptors derived from the electroretinogram.

1. The a-wave of the electroretinogram was recorded from human subjects with normal vision, using a corneal electrode and ganzfeld stimulation. We applied the paired-flash technique, in which an intense 'probe' flash was delivered at different times after a 'test' flash. The amplitude of the probe-flash response provided a measure of the circulating current remaining at the appropriate time after the test flash. 2. We extended previous methods by measuring not at a fixed time, but at a range of times after the probe flash, and then calculating the ratio of the 'test-plus-probe' response to the 'probe-alone' response, as a function of time. 3. Under dark-adapted conditions the rod response derived by the paired-flash technique (in response to a relatively dim test flash) peaked at ca 120 ms, with a fractional sensitivity at the peak of ca 0.1 Td(-1) s(-1). 4. As reported previously, background illumination reduced the maximal response, reflecting a reduction in rod circulating current. In addition, it shortened the time to peak (to ca 70 ms at an intensity of 170 Td), and reduced the flash sensitivity measured at the peak. The flash sensitivity declined approximately according to Weber's Law, with a 10-fold reduction occurring at an intensity of 100-200 Td. We could not reliably measure responses at significantly higher background intensities because the circulating current became so small. 5. In order to investigate the phototransduction process after correction for response compression, we expressed the derived response as a fraction of the maximal response that could be elicited in the presence of the background. The earliest rising phase of this 'fractional response per unit intensity' was little affected by background illumination, suggesting that the amplification constant of transduction was unaltered by light adaptation.

Human cone photoreceptor responses measured by the electroretinogram [correction of electoretinogram] a-wave during and after exposure to intense illumination.

We recorded the a-wave of the electroretinogram from human subjects with normal vision, using a corneal fibre electrode and ganzfeld stimulation under photopic conditions, so as to extract the parameters of cone phototransduction. The amplitude of bright flash responses provided a measure of the massed circulating current of the cones, while the amplitude of dim flash responses provided a measure of the product of the fraction of cone photopigment present, and the amplification constant of transduction within the cones. In the presence of steady background illumination, the cone circulating current declined to half at 3000 photopic trolands, and to a quarter at 20 000 photopic trolands. At very early times after the delivery of a near-total bleach, we could not determine the level of circulating current as our bright flashes did not appear to saturate the a-wave (presumably because so little pigment was present). However, by 20-30 s after a total bleach, the cone circulating current had returned to its dark-adapted level. Following smaller bleaches (when ca 50 % of the pigment remained present) the bright flashes were able to saturate the a-wave even at very early times. Within 3 s of extinction of the illumination, the cone circulating current had returned to its dark-adapted level. This is at least a factor of 300 times faster than the period of ca 15 min required for full recovery of rods exposed to the same level of bleach, and indicates a major difference between rods and cones in the way that they cope with the photoproducts of bleaching. Despite the very rapid recovery of circulating current after bleaches, the recovery of dim-flash sensitivity was much slower, with a time constant of ca 1.5 min after a near-total bleach. This time course is very similar to previous measurements of the regeneration of cone photopigment, and it seems highly probable that the reduction in dim-flash sensitivity results from pigment depletion.

Evaluation of the Night Vision Spectacles on patients with impaired night vision.

BACKGROUND: The Night Vision Spectacles (NiViS) were developed by a consortium of European companies to assist individuals who suffer from impaired night vision. They consist of a head-mounted video camera (input) and binocular displays (output) connected to a portable computer processor, which uses an algorithm to enhance the luminance and contrast of the video image. METHODS: Eighteen patients with impaired night vision were tested, including those with retinitis pigmentosa (7), Usher syndrome (2), fundus albipunctatus (1) and complete (4) and incomplete (4) congenital stationary night blindness. Normal trichromats (3) and typical, complete achromats (2) acted as controls. A battery of tests assessed: visual acuity at 5 m (projection unit) and 1 m (chart) and at high and low contrasts; contrast sensitivity; absolute and increment threshold; the influence of glare; contrast motion detection; and hand-eye performance. The tests were performed, with and without the NiViS, at three adaptation levels: low scotopic (10(-3) cd/m2), high scotopic (10(-2) cd/m2) and mesopic (10(-1) cd/m2). RESULTS: At the low and high scotopic levels, the majority of patients showed improved performance on the visual acuity, contrast sensitivity and motion contrast tests with the NiViS. At the mesopic level, the advantage with the NiViS was greatly reduced, but still present for contrast sensitivity. CONCLUSION: Patients with impaired night vision can benefit from the NiViS when performing tasks involving contrast and motion perception. Those with normal visual fields and retaining good photopic vision will benefit more than those with constricted visual fields and impaired cone vision. Recommendations regarding desirable improvements of the NiViS and suitability for the individual patient are given.

A computer-controlled system for measuring dark adaptation and other psychophysical functions.

BACKGROUND: Psychophysical thresholds, including dark-adaptation functions and increment threshold sensitivities, are useful for the early detection and diagnosis of visual pathologies. However, few instruments have been designed or adapted for their routine clinical measurement. METHODS: Here we describe an instrument prototype designed to meet this need, which we refer to as the PULS (Programmier-barer Universeller Licht-Stimulator). The instrument is computer-controlled and fully automated. It allows direct control over target location, luminance, size, duration and temporal profile and over background luminance and spectral composition. It also incorporates an efficient and statistically rigorous strategy for determining threshold. RESULTS: We present examples of psychophysical functions-dark-adaptation curves, increment threshold sensitivities, estimates of temporal summation in the dark and during the time course of dark adaptation-which have been measured by the PULS prototype in normal observers and clinical patients. CONCLUSIONS: The PULS instrument provides an automatic and efficient means of measuring dark adaptation and other psychophysical functions. It determines threshold by a more rigorous and faster method than is conventionally employed in clinical adaptometry.