The key role of electrophysiology in the diagnosis of visually impaired children

Infantile nystagmus without overt eye abnormality: Early features and neuro-ophthalmological diagnosis

AIM

To analyse the neuro-ophthalmological data of children referred for further work-up of infantile nystagmus where ophthalmological evaluation had not achieved a diagnosis.

METHOD

We retrospectively reviewed medical records of patients presenting with infantile nystagmus at our institution between 2007 and 2019. Inclusion criteria were onset before 6 months of age, availability of complete ophthalmic examination, visual electrophysiological tests, and neurological examination. Children with a previous definite ophthalmological diagnosis at onset and those with uncertain nystagmus onset age were not recruited.

RESULTS

Out of 142 infants (mean age at nystagmus onset 3.6 mo, SD 1.7, range 0-6 mo; 56 females, 86 males), 23% had neurological nystagmus, 7% mixed neurological and sensory nystagmus, 48% sensory defect, and 22% idiopathic infantile nystagmus. The neurological diagnoses were inborn errors of metabolism, white matter genetic disorders, and brain malformations. The prevalent diagnosis in the sensory defect subgroup was retinal dystrophy.

INTERPRETATION

Infantile nystagmus without diagnostic ocular findings may be due to neurological, retinal, and optic nerve disorders or be a benign idiopathic condition. In infants with and without neurological abnormalities, the search for a sensory defect should include visual electrophysiology performed early in the diagnostic pathway.

WHAT THIS PAPER ADDS

Infantile nystagmus without diagnostic ophthalmological signs has an underlying neurological cause in 30% of cases. Neurological diagnoses include congenital brain malformations, and metabolic and genetic disorders. Sensory defects are part of systemic neurological disorders in 23% of infants. Electrophysiology is useful when ophthalmological examination is uninformative.

An alternative electroretinography protocol for children: a study of diagnostic agreement and accuracy relative to ISCEV standard electroretinograms

PURPOSE

To assess the diagnostic accuracy and agreement between a paediatric electroretinography protocol used at Great Ormond Street Hospital (GOSH-ERG) and the 'gold standard' international protocol (ISCEV-ERG) in health and disease.

METHODS

Patient databases between 2010 and 2020 were screened to identify children with an ISCEV-ERG recorded within four years of a GOSH-ERG. Electroretinogram (ERG) component peak times and amplitudes were re-measured, and data were analysed in terms of absolute abnormality and proportional deviation from respective reference ranges. Abnormality was defined by the retinal system affected and by individual ERG a- and b-wave component analysis.

RESULTS

A total of 59 patients were included: 38 patients had retinal disease defined by an abnormal ISCEV-ERG and 21 had normal ISCEV-ERGs. When absolute abnormality was defined by combined retinal systems, the GOSH-ERG showed an excellent overall sensitivity of 95% (accuracy 86%). Individual retinal systems showed good-excellent sensitivity (67%-100%) and specificity (68%-97%). Electroretinogram (ERG) component sensitivities ranged between 60% and 97% and specificities between 79% and 97% dependent upon the protocol step. The proportional relationship appeared mostly linear between protocols. Electroretinogram (ERG) morphology was comparable for both protocols in a range of retinal diseases including those with pathognomonic ERGs.

CONCLUSION

We demonstrate the high diagnostic accuracy of a paediatric ERG protocol (GOSH-ERG) relative to ISCEV standard ERGs. The close proportional deviation and similar waveform morphology indicate ERGs from each protocol are similarly affected in disease. This encourages the use of the GOSH-ERG protocol in the screening, diagnosis and monitoring of retinal disease in children who are unable to comply with the rigorous ISCEV-ERG protocol.

Recognizing differentiating clinical signs of CLN3 disease (Batten disease) at presentation

Purpose

To help differentiate CLN3 (Batten) disease, a devastating childhood metabolic disorder, from the similarly presenting early‐onset Stargardt disease (STGD1). Early clinical identification of children with CLN3 disease is essential for adequate referral, counselling and rehabilitation.

Methods

Medical chart review of 38 children who were referred to a specialized ophthalmological centre because of rapid vision loss. The patients were subsequently diagnosed with either CLN3 disease (18 patients) or early‐onset STGD1 (20 patients).

Results

Both children who were later diagnosed with CLN3 disease, as children who were later diagnosed with early‐onset STGD1, initially presented with visual acuity (VA) loss due to macular dystrophy at 5–10 years of age. VA in CLN3 disease decreased significantly faster than in STGD1 (p = 0.01). Colour vision was often already severely affected in CLN3 disease while unaffected or only mildly affected in STGD1. Optic disc pallor on fundoscopy and an abnormal nerve fibre layer on optical coherence tomography were common in CLN3 disease compared to generally unaffected in STGD1. In CLN3 disease, dark‐adapted (DA) full‐field electroretinogram (ERG) responses were either absent or electronegative. In early‐onset STGD1, DA ERG responses were generally unaffected. None of the STGD1 patients had an electronegative ERG.

Conclusion

Already upon presentation at the ophthalmologist, the retina in CLN3 disease is more extensively and more severely affected compared to the retina in early‐onset STGD1. This results in more rapid VA loss, severe colour vision abnormalities and abnormal DA ERG responses as the main differentiating early clinical features of CLN3 disease.

Windows into the Visual Brain: New Discoveries about the Visual System, Its Functions, and Implications for Practitioners

Introduction

In recent years, major progress has been made in understanding the human visual system because of new investigative techniques. These developments often contradict older concepts about visual function.

Methods

A detailed literature search and interprofessional discussions.

Results

Recent innovative neurological tests are described that are able to show much more accurately the visual pathways, the process of vision, and the close relationships among sensory modalities. These tests also reveal the remarkable neuroplasticity of the human brain and disorders of connectivity that frequently involve visual function.

Discussion

How these recent neurological advances may benefit service providers is discussed.

Implications for practitioners

It is important that from time to time new neurological and ophthalmic developments are summarized for professionals who are involved in the clinical management of individuals with visual disorders and how the newly acquired knowledge affects the diagnosis and intervention strategies. Visual rehabilitation must be based on up-to-date science, which continually changes and grows with research.

Novel truncating mutation in CACNA1F in a young male patient diagnosed with optic atrophy

BACKGROUND

Low vision in children can be accompanied by pallor of the optic disc with little or no characteristic morphologic changes of the retina. A variety of diseases can be the underlying cause, including hereditary optic atrophy, Leber's congenital amaurosis (LCA), achromatopsia, and calcium channel, voltage-dependent, L-type, alpha-1F subunit gene (CACNA1F)-associated retinopathy (most widely known as incomplete congenital stationary night blindness: iCSNB). Differentiation at early age is desirable due to large differences in prognosis, but may be difficult because phenotypes overlap and electrophysiological testing is challenging in young patients. We present the case of a 6-year-old boy with unexplained low vision and pallor of the optic disc who originally had been diagnosed with hereditary optic atrophy in the absence of recordable full-field electroretinography (ERG) due to poor patient cooperation.

MATERIALS AND METHODS

Standard Sanger sequencing excluded mutations in the OPA1 gene (autosomal-dominant optic atrophy). To identify the underlying genetic cause, whole-exome sequencing was performed on patient's DNA. Recording of the full-field ERG was successfully performed 6 months later.

RESULTS

We identified a novel truncating mutation in CACNA1F gene (NM_001256789: c.3895C > T in exon 33) which led to the correct diagnosis of CACNA1F-associated retinopathy in the young boy. ERG recordings showed a negative scotopic mixed response with preserved oscillatory potentials and a flicker ERG with reduced amplitude and biphasic waveform, compatible with a CACNA1F-asssociated phenotype.

CONCLUSIONS

We show that genetic testing may help to differentiate between optic atrophy, LCA, and CACNA1F-associated retinopathy at a much earlier age, in absence of electrophysiological examination and by widely overlapping phenotypes.

The diagnosis and assessment of visual function in Singaporean children with electrophysiology: 10-year results

PURPOSE

To study the clinical use and efficacy of electrophysiology in children.

METHODS

This was a retrospective review of all children aged <16 years, who were referred to the Visual Electrophysiology Laboratory at the Singapore National Eye Center between 2003 and 2013.

RESULTS

A total of 586 children, median age 8 years (range 0.15-16), were referred for a variety of reasons including investigation of poor vision (40 %), suspected retinal disease or optic nerve/cortical dysfunction (17 %), nystagmus (13 %) and screening or monitoring of a variety of ocular or neurological conditions (12 %). The number of children with vision 6/15 or worse was 418 (71 %), and 103 (18 %) had vision 6/120 or worse in at least one eye. The most common pathology noted was retinal dystrophy or dysfunction (41 %) or optic nerve/cortical dysfunction (12 %). In 30 %, visual electrophysiology was within normal limits, and in 6 %, a conclusive diagnosis could not be obtained.

CONCLUSION

Electrophysiology testing played an important role in the assessment of children and added to the clinical management of the patient.

Macular function measured by binocular mfERG and compared with macular structure in healthy children

PURPOSE

To create normative data in children from binocular multifocal ERG (mfERG) recordings and compare results with the macular thickness.

METHODS

Forty-nine 5- to 15-year-old healthy, full-term children were examined with Espion Multifocal System, using DTL electrodes. The stimulus matrix consisted of 37 hexagonal elements. Amplitudes, implicit times and response densities (presented in three rings) of the first-order component P1 were analyzed. Measurements of macular thickness were performed with spectral-domain Cirrus OCT.

RESULTS

There were no significant differences between right and left eyes regarding mfERG recordings. Median P1 implicit times of Rings 1-3 of the 46 right eyes were 30.0, 30.0 and 30.8 ms and response densities 20.5, 10.9 and 7.6 nV/deg(2), respectively. Implicit time was longer in boys than in girls (p = 0.009, 0.039, 0.005 in Rings 1-3) and was correlated with age (r s = 0.417, 0.316, 0.274 in Rings 1-3). Implicit time in Ring 1 correlated significantly with the inner circle of the OCT measurements (p = 0.014).

CONCLUSION

Binocular mfERG with DTL electrodes is a reliable test of the central macular function in children and correlates with macular structure. As previously not shown, there was a significant difference in implicit time between boys and girls.

Tests for malingering in ophthalmology

Simulation can be defined as malingering, or sometimes functional visual loss (FVL). It manifests as either simulating an ophthalmic disease (positive simulation), or denial of ophthalmic disease (negative simulation). Conscious behavior and compensation or indemnity claims are prominent features of simulation. Since some authors suggest that this is a manifestation of underlying psychopathology, even conversion is included in this context. In today's world, every ophthalmologist can face with simulation of ophthalmic disease or disorder. In case of simulation suspect, the physician's responsibility is to prove the simulation considering the disease/disorder first, and simulation as an exclusion. In simulation examinations, the physician should be firm and smart to select appropriate test(s) to convince not only the subject, but also the judge in case of indemnity or compensation trials. Almost all ophthalmic sensory and motor functions including visual acuity, visual field, color vision and night vision can be the subject of simulation. Examiner must be skillful in selecting the most appropriate test. Apart from those in the literature, we included all kinds of simulation in ophthalmology. In addition, simulation examination techniques, such as, use of optical coherence tomography, frequency doubling perimetry (FDP), and modified polarization tests were also included. In this review, we made a thorough literature search, and added our experiences to give the readers up-to-date information on malingering or simulation in ophthalmology.

The 'dark' side of sedation: 12 years of office-based pediatric deep sedation for electroretinography in the dark

OBJECTIVES

Analyze pediatric ERG data for adverse events, interventions, and outcomes of propofol sedations performed in near-complete darkness.

AIM

To demonstrate that deep sedation with propofol for ERG can be performed efficiently and safely in children in near-total darkness.

BACKGROUND

Full-field electroretinography (ERG) is a valuable tool for the diagnosis of vision loss in children. The ERG measures the electrical activity of the retina. In children, ERG quality significantly improves with deep sedation by allowing easier eye electrode placement and decreasing motion artifacts. As this procedure must be performed in darkness, administering sedation imposes unique challenges.

METHODS AND MATERIALS

ERGs are performed outside of the operating room in our hospital's electrophysiology suite. IVs are placed, and patients are allowed to adapt to complete darkness. An anesthesiologist then administers propofol sedation in the dark with the aid of a red-filter light source and monitor light shields. Data were collected on 379 patients (411 ERGs) performed from 1996 to 2008. These records were reviewed and analyzed for demographic, medical, and anesthetic data.

RESULTS

Propofol sedation resulted in an ERG completion rate of 99.5%. During sedation, 8.5% (35) of patients experienced minor respiratory complications such as airway obstruction that resulted in an oxygen saturation <90%. A total of 9.7% (40) of patients required minor airway interventions such as a chin lift.

CONCLUSIONS

We demonstrated that pediatric sedation is a safe, efficient, and a cost-effective method for measuring ERGs in a challenging environment. The incidence of minor complications is low and appears similar to other studies of propofol sedation.

[Clinical findings and diagnostics of cone dystrophy]

BACKGROUND

Cone dystrophies present with highly variable clinical findings and often limited retinal changes, which may lead to misdiagnosis. The purpose of the present review of the clinical presentation and diagnosis of cone dystrophies is to provide guidelines for improved patient care.

METHODS

A literature search and evaluation of the clinical findings were carried out in 450 patients with cone dystrophy examined between 1986 and 2008.

RESULTS

Characteristic signs are loss of visual acuity, photophobia and central scotoma. The diagnosis of cone dystrophy is determined by a full-field electroretinogram (ERG). Fundus and near-infrared autofluorescence as well as optical coherence tomography allow detection of retinal structural abnormalities even when findings from ophthalmoscopy are normal.

CONCLUSION

The diagnosis of cone dystrophy is difficult due to unspecific subjective symptoms and absence of characteristic ophthalmoscopic findings. The differential diagnosis of unexplained visual loss should include cone dystrophy and requires either a full-field or multifocal ERG.

Visually impaired children: "coming to better terms"

For a visually impaired child, the accurate establishment of the diagnosis provides information on the prognosis of his or her participation possibilities, including expectations about the need for care, and provides the basis for informed genetic counseling. To maximize the diagnostic value of electrophysiological testing, we use extensions of the standard ISCEV (International Society for Electrophysiology in Vision) protocols for both the ERG (electroretinogram) and the VEP (visual evoked potential). An overview of 3 years' practice of the Department of Ophthalmology of Bartiméus, presented at ISCEV in Glasgow, showed that, as a result of our electrophysiological assessment, in about 10% of the cases the diagnosis at referral had to be changed from a progressive to a stationary disorder or the reverse. It is obvious that these parameters drastically change the strategy to attain "coming to terms with the disorder". It turns out that for the visually impaired child or his or her parents as well as for the professionals in the rehabilitation institutes, the terminology used to describe a disorder can be unnecessarily alarming rather than comprehensible or even realistic. Terminology needs to be clear and understandable, with a clearcut distinction between the description of visual functions and the name of a disorder. In albinism, the bad connotation of the name of this disorder together with the finding of non-albinos with misrouting and definite albinos without it forces us to reconsider the nomenclature. With congenital stationary night blindness (CSNB), the finding of youngsters who are clearly capable of mobility at night and the fact that the term night blindness refers to a function instead of a disorder forces us even more to reconsider nomenclature.