Clinical and electrophysiology findings in Slovene patients with Leber hereditary optic neuropathy.

BACKGROUND: To report clinical and electrophysiology findings in Slovene patients with Leber hereditary optic neuropathy (LHON). METHODS: Eight patients with LHON (11-26 years; one female and seven males) were examined in acute stages and at follow-up visits by means of Snellen visual acuity, Ishihara color vision, Goldmann or Octopus G2TOP perimetry, fluorescein angiography (FAG), pattern electroretinogram (PERG), visual evoked potentials (VEP) and genetic testing. RESULTS: Patients presented with typical LHON phenotype with bilateral visual acuity loss, abnormal color vision, central scotoma and hyperemic discs with no leakage on FAG. In the acute stage, electrophysiology was performed in 7/8 patients. The PERG P50 component was normal in 14/14 eyes, while the N95 component was reduced in 7/14 eyes. VEP wave P100 was reduced and delayed in 14/14 eyes. In this stage, temporal pallor of the optic disc was visible in 4/7 eyes with reduced PERG N95. At follow-up (1-11 months after), a reduced PERG N95 component was seen in 13/14 eyes and severely affected VEP in all eyes. In the only eye with a normal PERG N95, hyperemic optic disc was seen 5 months after visual acuity loss, while it was atrophic in all the others. Known mutations (14484T>C, 3460G>A) were found in 2/8 patients, while in others high-throughput sequencing identified new potentially pathogenic mutations. CONCLUSIONS: In Leber hereditary optic neuropathy, a reduced N95 component of PERG and severely reduced VEP P100 may be present already in the acute stage of disease, before optic disc pallor appears, suggesting primary dysfunction of retinal ganglion cells.

VEP characteristics in children with achiasmia, in comparison to albino and healthy children.

Achiasmia is a rare disorder of visual pathway maldevelopment that can show diverse clinical and magnetic resonance imaging spectra. The aim of this study was to define the characteristics of visual evoked potentials (VEPs) that differentiate abnormal optic-nerve-fibre decussation in children with achiasmia versus children with albinism and healthy children. In four children with achiasmia, the following VEP characteristics were studied and compared to children with ocular albinism and with healthy control children: (a) flash and pattern onset VEP interhemispheric asymmetry; (b) flash N2, P2 and onset C1 amplitudes and latencies; (c) interocular polarity differences in interhemisphere potentials; and (d) chiasm coefficients (CCs). In the children with achiasmia, VEPs were related to an absence of or reduced optic-nerve-fibre decussation at the chiasm and showed: ipsilateral asymmetry, significantly higher VEP amplitudes over the ipsilateral hemisphere (p < 0.05), interocular inverse polarity and negative CC. Other VEP features (uncrossed asymmetry and positive CC) were also seen if additional visual pathway maldevelopment (such as severe optic nerve hypoplasia and/or absence of the optic tractus on one side) were associated with achiasmia. In the children with albinism, the VEPs were related to excess optic-nerve-fibre decussation at the chiasm and showed: contralateral asymmetry, significantly higher VEP amplitudes over the contralateral hemisphere (p < 0.001), interocular inverse polarity and negative CC. In achiasmia and albinism, the VEPs to flash stimulation were more robust and more clearly distinguished between the conditions compared with the VEPs to pattern onset stimulation. VEPs in achiasmia are associated with absent or reduced optic-nerve-fibre decussation, where ipsilateral interhemispheric asymmetry is associated with interocular inverse polarity and a negative CC.

Genetic Variability in Slovenian Cohort of Patients with Oculocutaneous Albinism.

Oculocutaneous albinism (OCA) is an inherited disorder affecting the visual system and skin pigmentation. Our aim was to evaluate genetic and clinical heterogeneity in a cohort of Slovenian paediatric patients with clinically suspected OCA using advanced molecular-genetics approach. In as much as 20 out of 25 patients, genetic variants explaining their clinical phenotype were identified. The great majority of patients (15/25) had genetic variants in TYR gene associated with OCA type 1, followed by variants in TYRP1, SLC45A2 and HPS1 genes causative for OCA3, OCA4 and Hermansky-Pudlak syndrome type 1, respectively. We concluded that OCA phenotype could not predict genotype and vice versa. Nevertheless, the diagnostic yield after targeted next generation sequencing (NGS) was 80% and proved to be affective in our paediatric cohort of patients with various degree of OCA. Even in 16 patients with normal complexion the diagnostic yield was 62,5%. Interestingly, we have identified a patient of white European ancestry with OCA3, which is an extremely rare report, and one patient with OCA due to the Hermansky-Pudlak syndrome type 1.

Chromatic VEP in children with congenital colour vision deficiency.

Visual evoked potentials to chromatic stimulus (cVEP) are believed to selectively test the parvocellular visual pathway which is responsible for processing information about colour. The aim was to evaluate cVEP in children with red-green congenital colour vision deficiency. VEP responses of 15 colour deficient children were compared to 31 children with normal colour vision. An isoluminant red-green stimulus composed of horizontal gratings was presented in an onset-offset manner. The shape of the waveform was studied, as well as the latency and amplitude of positive (P) and negative (N) waves. cVEP response did not change much with increased age in colour deficient children, whereas normative data showed changes from a predominantly positive to a negative response with increased age. A P wave was present in 87% of colour deficient children (and in 100% of children with normal colour vision), whereas the N wave was absent in a great majority of colour deficient children and was present in 80% of children with normal colour vision. Therefore, the amplitude of the whole response (N-P) decreased linearly with age in colour deficient children, whereas in children with normal colour vision it increased linearly. P wave latency shortened with increased age in both groups. cVEP responses differ in children with congenital colour vision deficiency compared to children with normal colour vision.

Electroretinograms in idiopathic infantile nystagmus, optic nerve hypoplasia and albinism.

PURPOSE: To study electroretinograms in infantile nystagmus syndrome associated with idiopathic infantile nystagmus, optic nerve hypoplasia, and albinism. METHODS: A total of 30 children with idiopathic infantile nystagmus, 18 with optic nerve hypoplasia, and 18 with albinism were studied. Three electroretinogram protocols were applied according to child's age: 58 (mean: 2.0 years) were recorded with skin electrode to Great Ormond Street Hospital protocol, 11 (mean: 5.3 years) with skin electrode to International Society for Clinical Electrophysiology of Vision protocol, and 7 children (mean: 12.2 years) with HK electrode to International Society for Clinical Electrophysiology of Vision protocol. The electroretinograms were compared to those of age-matched controls. RESULTS: Electroretinogram waveforms in idiopathic infantile nystagmus, optic nerve hypoplasia, and albinism were comparable to controls in all protocols. Electroretinogram amplitudes in idiopathic infantile nystagmus group showed increased white scotopic and photopic electroretinograms in 26 children (skin electrode to Great Ormond Street Hospital protocol), no difference to the controls in 3 children (skin electrode to International Society for Clinical Electrophysiology of Vision protocol), and increased rod electroretinogram in 3 children (HK electrode to International Society for Clinical Electrophysiology of Vision protocol). Optic nerve hypoplasia group showed increased white scotopic, photopic, and blue electroretinograms in 15 children (skin electrode to Great Ormond Street Hospital protocol); increased 30-Hz electroretinogram in 3 children (HK electrode to International Society for Clinical Electrophysiology of Vision protocol); and reduced combined rod-cone, cone, and 30-Hz electroretinograms in 3 children (skin electrode to International Society for Clinical Electrophysiology of Vision protocol). Albinism group showed increased white scotopic, photopic, and 30-Hz electroretinograms in 17 children (skin electrode to Great Ormond Street Hospital protocol), while it showed reduced cone and 30-Hz electroretinograms in 5 children (skin electrode to International Society for Clinical Electrophysiology of Vision protocol). Implicit times were shorter in albinism. CONCLUSION: Electroretinogram waveforms in idiopathic infantile nystagmus, optic nerve hypoplasia, and albinism were normal with mostly increased electroretinograms, while reduced electroretinograms did not show a specific pattern as in early-onset retinal dystrophies.

Histochemical and immunohistochemical profile of human and rat ocular medial rectus muscles.

PURPOSE: To compare the organization of human and rat ocular medial recti muscles (MR). METHODS: The cryosections of human and rat MR were processed for myofibrillar ATPase (mATPase), succinate dehydrogenase and glycerol-3-phosphate dehydrogenase. To reveal myosin heavy chain (MyHC) isoforms, specific monoclonal antibodies against MyHC-1/beta- slow, alpha-cardiac (-alpha), -2a, -2x, -2b, -extraocular (eom), -embryonic (-emb) and -neonatal (-neo) were applied. The MyHC gene expression was studied by in situ hybridization in human muscle. RESULTS: The muscle fibers were arranged in two distinct layers in both species. In the orbital layer most fibers were highly oxidative and expressed fast MyHC isoforms, whereas slow and oxidative fibers expressed MyHC-1 and -alpha, some of them also MyHC-2a, -2x, -eom, very rarely -emb, and -neo. In the global layer, slow fibers with very low oxidative and glycolytic activity and three types of fast fibers, glycolytic, oxidative and oxidative-glycolytic, could be distinguished. The slow medium-sized fibers with mATPase activity stable at pH 4.4 expressed mostly MyHC-1 and -alpha in rat, while in humans they co-expressed MyHC-1 with -2b, -2x, -eom, and -neo. In both species, the fast fibers showed variable mATPase activity after preincubation at pH 9.4, and co-expressed various combinations of MyHC-2b, -2x, -2a and -eom but not -emb and -neo. MyHC-2b expressing fibers were larger and glycolytic, while MyHC-2a expressing fibers were smaller and highly oxidative in both species. To our knowledge, the present study is the first that demonstrated the expression of MyHC-2b in any of human skeletal muscles. Though the expression of MyHC genes did not correlate with the immunohistochemical profile of fibers in human MR, the expression of MyHC-2b gene was undoubtedly confirmed. CONCLUSIONS: Rat MR represent a good model that can be applied to study human MR in experiment or disease, however certain differences are to be expected due to specific oculomotor demands in humans.

Refining clinical phenotypes in septo-optic dysplasia based on MRI findings.

Septo-optic dysplasia (SOD) is a heterogeneous brain midline anomaly associated with ophthalmological, endocrinological, and/or neurodevelopmental symptoms. The clinical phenotype correlates with abnormal brain magnetic resonance imaging (MRI) findings. However, variations of the septum pellucidum (SP) appearance and their clinical impact have not been studied in depth. Sixty-eight patients with optic nerve hypoplasia (ONH) were investigated for the presence of associated SP anomalies and correlations between clinical findings and their MRI abnormalities established. Thirty patients had either complete (n = 22) or partial (n = 8) absence of the SP. Pituitary hormone deficiencies were present in 64% or 25% of the cases, respectively. Neurological symptoms did not occur in patients with SP remnants or unilateral ONH. Hippocampus abnormalities (43%) that have not been described before in SOD and falx abnormalities (17%) correlated significantly with neurological symptoms and developmental delay (p < 0.05 and p < 0.01, respectively). Maternal age at birth was low (21.2 years) and drug abuse during pregnancy was reported in 27% of the patients. Twelve patients with pituitary anomaly and ONH but normal SP showed similar clinical and MRI features, and were classified as SOD-like. The remaining 26 patients were not assigned to SOD. We conclude that unilateral ONH and SP remnants are associated with a milder SOD phenotype. Hippocampus abnormalities and falx abnormalities seem to constitute important features of severe clinical disease, irrespective of SP appearance. Our anamnestic data support the hypothesis of vascular disruption during embryogenesis.

Electroretinographic characteristics in children with infantile nystagmus syndrome and early-onset retinal dystrophies.

PURPOSE: To differentiate early-onset retinal dystrophies on the basis of electroretinogram (ERG) characteristics in children with infantile nystagmus syndrome (INS). METHODS: Thirty-seven children with INS and early-onset retinal dystrophies were included, with diagnosis according to clinical and ERG findings. Three ERG protocols were used according to the child's age and 17 children were followed with 2 protocols: 27 (mean 2.1 years) were recorded with skin electrodes to flash stimulation, 16 (mean 6.5 years) with skin electrodes to full-field stimulation, and 11 (mean 12.2 years) with HK electrodes to full-field stimulation. The ERGs were compared to those of age-matched controls, with differences significant if p<0.05. RESULTS: Clinical and electrophysiologic findings were in agreement across all of the children. In nine children with Leber congenital amaurosis, the scotopic and photopic ERGs were not recordable under all protocols. Six children with congenital stationary night blindness (CSNB) had electronegative scotopic ERG under all protocols, those with complete CSNB had absent rod ERG, and those with incomplete CSNB had reduced rod ERG. Eight children with achromatopsia had nonrecordable photopic and subnormal scotopic ERG under all protocols. The implicit times of the scotopic b-waves were prolonged. One child had blue-cone monochromatism and reduced photopic and normal S-cone ERG. Six children with cone-rod dystrophy without systemic disorder, and seven children with systemic disorder, had affected photopic and scotopic ERGs under all protocols. CONCLUSIONS: In children with INS, some early-onset retinal dystrophies can be differentiated through ERGs, also with skin electrodes.

Visual electrophysiological screening in diagnosing infants with congenital nystagmus.

OBJECTIVE: To determine the value of visual electrophysiological screening in evaluating retinal and postretinal visual pathway function in infants with congenital nystagmus. METHODS: In 28 infants with congenital nystagmus electroretinogram (ERG) was recorded with skin electrodes and, since the infants were alert, visual evoked potentials (VEP) were simultaneously recorded. The first recording was performed before the age of 1 year (age 2-11 months, mean age 6.8 months). Follow-up was performed between the ages of 7 months and 6 years (mean age 2.7 years). ERG was detected to flash stimulus and VEP to flash and/or pattern-reversal stimulus. RESULTS: In infants less than 1 year of age, retinal dysfunction was recognised in 36% of infants who had been diagnosed as Leber's congenital amaurosis, achromatopsia and retinal dystrophy; postretinal dysfunction was recognised in 32% of infants who had been diagnosed with ocular albinism, optic nerve hypoplasia and neurological nystagmus; retinal or postretinal function was normal in 7% of infants that had been diagnosed as congenital idiopathic nystagmus, while retinal function was normal and postretinal function was undefined in 25% of infants that had been diagnosed as optic nerve hypoplasia, neurological nystagmus and congenital idiopathic nystagmus. At follow-up the findings were: retinal dysfunction in 36%, postretinal dysfunction in 50% and normal retinal and postretinal function in 14% of children. All those children with normal retinal and postretinal function had been diagnosed as congenital idiopathic nystagmus. CONCLUSIONS: Visual electrophysiological screening of infants with congenital nystagmus can establish or exclude retinal and postretinal pathway dysfunction. Therefore simultaneous skin ERG and VEP which is a non-invasive approach for infants enables an objective means for identifying the basis of congenital nystagmus, thereby assisting in its classification.

Ocular abnormalities and systemic disease in Down syndrome.

INTRODUCTION: Ocular problems as refractive errors, strabismus, accommodation, and cataract are well known in children with Down syndrome (DS). However, there is little information on the possible correlation of eye problems with systemic diseases such as heart defect (with or without surgery), hypotony, hypothyroidism, hearing loss, and others. METHODS: Ophthalmic problems versus certain systemic diseases were studied in 65 children with DS, aged 2 months to 13 years, referred to the University Eye Hospital Ljubljana, Slovenia from 2008 to 2010. Standard ophthalmic examination methods were used, and physical data were taken from pediatric records. RESULTS: Ocular findings included nystagmus (29.2%), esotropia (26.1%), epiphora (21.5%), Brushfield spots (16.9%), lens opacities (12.3%), abnormalities of the retinal vessels, foveal hypoplasia, or retinal pigment epithelium hyperplasia (32.2%), and optic disc pallor (7.6%). Hyperopia (36.9%) was the most frequent refractive error in the group, followed by astigmatism (29.2%) and myopia (24.6%). No diagnosed systemic abnormalities were found in 18.3% of the children, while 30.7% had congenital heart defect. Hypothyroidism, hypotony, hearing loss, gastrointestinal tract malformations, and leukemia were less common. Nystagmus was related to myopia and esotropia, and to heart disease and heart operations. CONCLUSIONS: Comorbidities are common in DS and complicate diagnosis, development, and therapy.

GPR143 gene mutation analysis in pediatric patients with albinism.

BACKGROUND: X-linked ocular albinism type 1 is difficult to differentiate clinically from other forms of albinism in young patients. X-linked ocular albinism type 1 is caused by mutations in the GPR143 gene, encoding melanosome specific G-protein coupled receptor. Patients typically present with moderately to severely reduced visual acuity, nystagmus, strabismus, photophobia, iris translucency, hypopigmentation of the retina, foveal hypoplasia and misrouting of optic nerve fibers at the chiasm. MATERIALS AND METHODS: Following clinical ophthalmological evaluation, GPR143 gene mutational analyses were performed in a cohort of 15 pediatric male patients with clinical signs of albinism. RESULTS: Three different mutations in the GPR143 gene were identified in four patients, including a novel c.886G>A (p.Gly296Arg) mutation occurring "de novo" and a novel intronic c.360 + 5G>A mutation, identified in two related boys. CONCLUSIONS: Four patients with X-linked ocular albinism type 1 were identified from a cohort of 15 boys with clinical signs of albinism using mutation detection methods. Genetic analysis offers the possibility of early definitive diagnosis of ocular albinism type 1 in a significant portion of boys with clinical signs of albinism.

VEP maturation and visual acuity in infants and preschool children.

PURPOSE: Visual processes continue to mature well into childhood, due to the development of the retina, optic nerve, visual pathway and visual cortex. Normal development of visual acuity and maturation of visual evoked potentials (VEPs) have been well studied, although rarely for their correlation. The purpose of this study was to investigate the same population of infants and preschool children for their VEP maturation to flash, pattern-reversal (reversal) and pattern-onset (onset) stimulation, which are normally used in our everyday clinical protocol, and to determine the relationships between the VEP parameters obtained and the development of visual acuity. METHODS: Forty-one healthy children from 1.5 months to 7.5 years old were included. Their visual acuity for distance was tested with Teller Acuity Cards (<2 years of age) and Cambridge Visual Acuity Crowding Cards (>2 years of age). VEP latencies and amplitudes were evaluated to flash (P2 wave), reversal (P100 wave) and onset (C1 wave) binocular stimulation. For reversal and onset stimulation, checkerboard pattern (check) sizes of 25', 50' and 100' were used. RESULTS: Age-dependent exponential decreases in latencies to flash, reversal and onset stimulation were seen. For amplitudes, there was an age-dependent increase only to onset stimulation. There was a significant correlation between VEPs and visual acuity (P < 0.05) for latencies to flash, reversal and onset stimulation and amplitudes to onset stimulation. CONCLUSION: These findings indicate the expected maturation of flash, reversal and onset VEPs, and demonstrate their correlation to normal development of visual acuity. Maturation of VEP latencies is associated with development of visual acuity.

Photopic ON- and OFF-responses in complete type of congenital stationary night blindness in relation to stimulus intensity.

The complete type of congenital stationary night blindness (complete CSNB) is a retinal disorder where the ON-response b-wave of the photopic electroretinogram is reduced, while the ON-response a-wave and OFF-response d-wave are preserved. These findings are related to ON-bipolar cell dysfunction, whereas the effects of myopia, which is usually associated with complete CSNB, have not been studied yet. The aim was to investigate ON-bipolar cell dysfunction in complete CSNB with variable-intensity stimuli, while excluding effects of myopia. ON- and OFF-responses were recorded from six complete CSNB patients, 10 control subjects (no refractive error; emmetropic control group) and 14 myopic subjects with similar refractive error and axial length as those with complete CSNB (myopic control group). Responses were elicited with stimulus intensities from 0.4 to 2.1 log cd s/m2 on a 20 cd/m2 background. Stimulus/response (S/R) functions were fitted to the Naka-Rushton equation and statistically evaluated. In complete CSNB, the S/R function of the a-wave measured at the time corresponding to the controls showed a lower Vmax than for the emmetropic controls, while all parameters were similar to the myopic control group. The b- and d-wave S/R functions of the complete CSNB group were similarly different to both control groups--for the b-wave, the Vmax and n were significantly lower, and for the d-wave, the sigma was significantly higher. These findings suggest that in complete CSNB, dysfunction of ON-bipolar cells influences the dynamics of the ON-response b-wave and OFF-response d-wave, independently of the effects of myopia.

VEP asymmetry with ophthalmological and MRI findings in two achiasmatic children.

Achiasmia is a rarely diagnosed visual pathway maldevelopment where all or the majority of nasal retinal fibres fail to decussate at the optic chiasm. It has been identified by neuroimaging and also by visual evoked potential (VEP) asymmetry. VEP asymmetry has not been defined consistently in previous studies. The aim was to study VEP asymmetry to flash stimulation in two children with maldevelopment of the optic chiasm in comparison to control children. Both children had congenital nystagmus, optic nerve hypoplasia with a bilateral small double ring, bitemporal visual field defect and normal colour vision. In child 1 visual acuity in both eyes was 0.1, in child 2 it was 0.2. MRI showed reduced chiasmal size in child 1, while in child 2 it was combined with other midline abnormalities. VEP to monocular flash stimulation showed in both children distinctive occipital distribution, which was not observed in control children. The N2 wave was distributed asymmetrically over the ipsilateral hemisphere to the stimulated eye, while the P2 wave was distributed over both hemispheres. The P2 wave was however better defined over the ipsilateral hemisphere. Flash VEP occipital distribution remained similar in child 1, who was followed from 10 months to 9 years. These cases of achiasmia demonstrate a distinctive VEP asymmetry in the distribution of the flash VEP N2 wave, as well as the expected structural defect determined by neuroimaging.

Seroprevalence of Toxocara antibodies among patients suspected of ocular toxocariasis in Slovenia.

Ocular toxocariasis named also ocular larva migrans is caused by larvae of the roundworm Toxocara spp. The purpose of this study was to find out the seroprevalence of Toxocara antibodies in patients suspected of ocular toxocariasis. Between January 2001 and December 2003, sera from 239 ocular patients, aged 3 to 80 years, were examined by ELISA and confirmed by Western blot test. Out of the 239 patients, 172 (72%) were seronegative and 67 (28%) were Toxocara seropositive; 95% CI (22-34%). The median age of Toxocara seropositive patients was 37.6 years. There was no significant difference in the number of Toxocara positive sera between the younger age group (< or = 14 years) and the older age group (> 14 years), p > 0.05. A high rate of Toxocara seropositivity in ocular patients should alert the ophthalmologists in Slovenia to include toxocariasis in the differential diagnosis of eye diseases more frequently.