Reduced grating acuity associated with retinal toxicity in children with infantile spasms on vigabatrin therapy

Elucidation of the cytogenotoxic potential of vigabatrin and its in silico computer-assisted DNA interaction

Vigabatrin (VGB) is a gammaaminobutyric acid-ergic (GABA-ergic) antiepileptic drug (AED) and is one of 2 approved drugs available to treat infantile spasms (IS). The aim of this study is to elucidate conflicting data on the toxic effects of VGB and to obtain detailed information about its possible cytogenotoxic effects in human lymphocytes. For this purpose, in vitro Chromosomal Aberration (CA), Sister Chromatid Exchange (SCE), Micronucleus (MN) tests, and Comet Assay were performed to determine possible genotoxic and cytotoxic effects of VGB. In addition, the binding energy level of VGB to DNA was determined in silico by molecular docking. The highest concentration (80 μg/ml) of VGB increased the SCE, CA, MN and micronucleated binuclear cell (BNMN) frequency significantly compared to the control after 24 and 48 hours of treatment. In the tail density and tail length parameters, the dose-dependent increase was found to be statistically significant compared to the control. At the 40 and 80 μg/ml concentrations of VGB for 48 hours caused a statistically significant increase in both CA/Cell and AC percentages, while MI and NDI decreased only significantly at the highest concentration (80 µg/ml) causing. In the Comet Assay head density, tail density and tail length parameters, the dose-dependent increase was found to be statistically significant compared to the control. Also, the in silico molecular docking analysis showed that VGB interacts with B-DNA close to the threshold binding energy. The lowest negative free binding energy (ΔG binding) was found as -5.13 kcal/mol. In conclusion, all results are evaluated together, it has been determined that VGB has cytogenotoxic effects in vitro and binds to DNA in silico with significant free binding energy.

Sex differences in side effects of antiseizure medications in pediatric patients with epilepsy: A systematic review

PURPOSE

To perform a systematic review searching for differences in the side effects of antiseizure medications (ASMs) with respect to sex in pediatric patients with epilepsy.

METHODS

We carried out a comprehensive literature search of the PubMed database and all results up to April 2020 were included. Titles, abstracts, and full texts of the articles were screened by two independent reviewers. We included all studies evaluating the side effects of ASMs in patients with epilepsy younger than 18 years, with reference to the two sexes. Studies on ASMs used for indications other than epilepsy were excluded.

RESULTS

A total of 5164 studies were identified. Sixty-seven studies were finally included, 5 of them also including adult patients in the sample. Sixteen studies revealed sex-related differences in side effects of ASMs, disclosing a higher frequency of general side effects in girls: a higher risk of overweight, hyperammonaemia, high leptin levels, and carnitine deficiency in girls on valproic acid; a lower height increase, an increased risk of weight loss, the anecdotical occurrence of acute psychosis in girls on topiramate; a higher risk of retinal toxicity in boys on vigabatrin.

CONCLUSION

The effect of sex on susceptibility to side effects of ASMs is poorly investigated with sparse results, and it could be underestimated. The findings of our study point to the presence of sex differences which should be thoroughly investigated to be confirmed, highlighting the need for a systematic evaluation of sex as a determinant variable influencing the response to medications in clinical research.

Therapeutic effect of the mesenchymal stem cells on vigabatrin-induced retinopathy in adult male albino rat

Vigabatrin (VGB) is an effective antiepileptic drug used mainly to treat infantile spasms and refractory complex partial seizures. However, using VGB was restricted as it was known to cause retinal toxicity that appears as a severe peripheral visual field defect. Accordingly, this study was conducted to examine the histopathological and biochemical effects of VGB on the retina in adult male albino rats and assess the possible therapeutic role of mesenchymal stem cells (MSCs) against this potential toxicity. The rats were divided into three groups (control group, VGB group, and VGB/MSCs group), one week after 65 days of VGB treatment ±MSCs. The right eyeballs were prepared for histological and immunohistochemical examination, whereas the left eyeballs were prepared for real-time polymerase chain reaction analysis. Our results demonstrated that MSCs ameliorated retinal pathological changes and downregulated the expression of glial fibrillary acidic protein, vascular endothelial growth factor, and synaptophysin after VGB administration suggesting MSCs function and vascular modulating effect. Moreover, MSCs regulate retinal tissue gene expression of BAX, Bcl-2, BDNF, NGF, synapsin, interleukin (IL)-6, IL-1β, and occludin suggesting MSCs antiapoptotic and immunomodulating effect. In conclusion, MSCs administration could be a suitable therapeutic line to ameliorate VGB-induced retinopathy.

Trends and Costs Associated With the Diagnosis and Treatment of Infantile Spasms: A 10-Year Multicenter Retrospective Review

OBJECTIVE

Early treatment of infantile spasms (IS) may be imperative for improvement of neurodevelopmental outcomes. Existing studies have led to inconclusive recommendations with variation in treatment. Our objective was to determine the national average cost, initial diagnostic workup, treatments, and hospital length of stay for patients with IS.

METHODS

This retrospective cohort study was designed to review data of patients < 2 years from 43 non-profit institutions. Data obtained included patient demographics, length of stay, admission cost, and treatments used from 2004 to 2014. Cost data were collected and adjusted to 2014 dollars, the year data were analyzed.

RESULTS

A total of 6183 patients met study criteria (n = 3382, 55% male). Three-quarters of patients (n = 4684, 76%) had an electroencephalogram, 56.4% had brain imaging (n = 3487), and 17% (n = 1050) underwent a lumbar puncture. Medication for IS was initiated during inpatient hospital stay in two-thirds of all patients (n = 4139, 67%). Most patients were initiated on corticotropin (n = 2066, 33%) or topiramate (n = 1804, 29%). Average length of stay was 5.8 days with an average adjusted cost of $18,348. Over time there was an 86.6% increase in cost from an average $12,534.54 (2004) to $23,391.20 (2014), a significant change (p < 0.01). This correlated with an increase in average length of stay.

CONCLUSIONS

Variability exists in diagnostic workup and pharmacotherapy initiated for IS, which may lead to differences in the cost of hospital stay. Further studies may help determine contributing factors to increased cost and improve health care utilization for IS patients.

Vigabatrin-related adverse events for the treatment of epileptic spasms: systematic review and meta-analysis

Objective: Although vigabatrin (VGB) is effective and well tolerated for the treatment of epileptic spasms, there are safety concerns. The aim of this systematic review and metaanalysis was to assess adverse events of VGB for the treatment of epileptic spasms. Methods: MEDLINE, EMBASE, and Cochrane databases were searched. The population was infants treated with VGB for epileptic spasms. The outcomes were VGB-related adverse events. Meta-analyses of VGB-related MRI abnormalities, retinal toxicity as measured by electroretinogram (ERG), visual field defect as measured by perimetry, and other adverse events were conducted. Results: Fifty-seven articles were included in the systematic review. The rate of VGB-related MRI abnormalities was 21% (95% CI: 15-29%). Risk factors for MRI abnormalities were age younger than 12 months and higher VGB dose. VGB-related retinal toxicity and visual field defect occurred in 29% (95% CI: 7-69%) and 28% (95% CI: 4-78%) respectively. Other adverse events occurred in 23% (95% CI: 16-34%), consisting predominantly of central nervous system symptoms, and the majority of these did not require therapeutic modification. Conclusion: This study will inform physicians and families on the risk profile of VGB for the treatment of epileptic spasms and will help decisions on treatment options.

A New Contrast Sensitivity Test for Pediatric Patients: Feasibility and Inter-Examiner Reliability in Ocular Disorders and Cerebral Visual Impairment

Purpose

Assess feasibility and interexaminer reliability of a new test of contrast sensitivity (CS) for pediatric populations.

Methods

The Double Happy (DH) measures CS using a method similar to the Teller Acuity Cards. The schematic DH face is 16 degrees in diameter with features of 0.3 c/d and a channel frequency of 0.8 c/d. DH log₁₀ CS is in 0.15 log unit steps, 0.05 to 2.1. Participants were 43 unselected patients, ages 2 to 18 years: 23 were diagnosed with ocular disorders only; 20 were diagnosed with cerebral visual impairment (CVI). Two examiners measured DH log₁₀ CS. Visual acuity (VA) was also measured.

Results

All 43 participants were tested for binocular DH log₁₀CS. Cohen's kappa values for interexaminer reliability were fair. The between examiner ICC was +0.92 (P < 0.001). The mean difference between examiners was near zero, and the 95% CI was −0.44 to 0.45 log₁₀CS. DH log₁₀CS was near normal in the ocular disorder group and reduced in the CVI group. VA was reduced in both groups. DH log₁₀ CS and VA were correlated (r = −0.65). DH log₁₀ CS was a marginally better predictor of diagnosis than VA.

Conclusions

DH log₁₀CS test was successful in a diverse pediatric population diagnosed with ocular disorders or CVI. Interexaminer reliability was comparable to that of adults tested previously using the same stimuli and methods. Both CS and VA are reduced in CVI.

Translational Relevance

CS and VA both should be tested in pediatric clinical populations, especially in those at risk of CVI.

VEP estimation of visual acuity: a systematic review

Purpose

Visual evoked potentials (VEPs) can be used to measure visual resolution via a spatial frequency (SF) limit as an objective estimate of visual acuity. The aim of this systematic review is to collate descriptions of the VEP SF limit in humans, healthy and disordered, and to assess how accurately and precisely VEP SF limits reflect visual acuity.

Methods

The protocol methodology followed the PRISMA statement. Multiple databases were searched using “VEP” and “acuity” and associated terms, plus hand search: titles, abstracts or full text were reviewed for eligibility. Data extracted included VEP SF limits, stimulus protocols, VEP recording and analysis techniques and correspondence with behavioural acuity for normally sighted healthy adults, typically developing infants and children, healthy adults with artificially degraded vision and patients with ophthalmic or neurological conditions.

Results

A total of 155 studies are included. Commonly used stimulus, recording and analysis techniques are summarised. Average healthy adult VEP SF limits vary from 15 to 40 cpd, depend on stimulus, recording and analysis techniques and are often, but not always, poorer than behavioural acuity measured either psychophysically with an identical stimulus or with a clinical acuity test. The difference between VEP SF limit and behavioural acuity is variable and strongly dependent on the VEP stimulus and choice of acuity test. VEP SF limits mature rapidly, from 1.5 to 9 cpd by the end of the first month of life to 12–20 cpd by 8–12 months, with slower improvement to 20–40 cpd by 3–5 years. VEP SF limits are much better than behavioural thresholds in the youngest, typically developing infants. This difference lessens with age and reaches equivalence between 1 and 2 years; from around 3–5 years, behavioural acuity is better than the VEP SF limit, as for adults. Healthy, artificially blurred adults had slightly better behavioural acuity than VEP SF limits across a wide range of acuities, while adults with heterogeneous ophthalmic or neurological pathologies causing reduced acuity showed a much wider and less consistent relationship. For refractive error, ocular media opacity or pathology primarily affecting the retina, VEP SF limits and behavioural acuity had a fairly consistent relationship across a wide range of acuity. This relationship was much less consistent or close for primarily macular, optic nerve or neurological conditions such as amblyopia. VEP SF limits were almost always normal in patients with non-organic visual acuity loss.

Conclusions

The VEP SF limit has great utility as an objective acuity estimator, especially in pre-verbal children or patients of any age with motor or learning impairments which prevent reliable measurement of behavioural acuity. Its diagnostic power depends heavily on adequate, age-stratified, reference data, age-stratified empirical calibration with behavioural acuity, and interpretation in the light of other electrophysiological and clinical findings. Future developments could encompass faster, more objective and robust techniques such as real-time, adaptive control.

Registration

International prospective register of systematic reviews PROSPERO (https://www.crd.york.ac.uk/PROSPERO/), registration number CRD42018085666.

West Syndrome: A Review and Guide for Paediatricians

West syndrome (WS), also known as infantile spasms, occurs in infancy with a peak between 4 and 7 months. Spasms, neurodevelopmental regression and hypsarrhythmia on electroencephalogram (EEG) basically define WS. The International League Against Epilepsy commission classifies the aetiologies of WS into genetic, structural, metabolic and unknown. Early diagnosis and a shorter lag time to treatment are essential for the overall outcome of WS patients. These goals are feasible with the addition of brain magnetic resonance imaging (MRI) and genetic and metabolic testing. The present work analysed the medical literature on WS and reports the principal therapeutic protocols of its management. Adrenocorticotropic hormone (ACTH), vigabatrin (VGB) and corticosteroids are the first-line treatments for WS. There is no unique therapeutic protocol for ACTH, but most of the evidence suggests that low doses are as effective as high doses for short-term treatment, which is generally 2 weeks followed by dose tapering. VGB is generally administered at doses from 50 to 150 mg/kg/day, but its related retinal toxicity, which occurs in 21-34% of infants, is most frequently observed when treatment periods last longer than 6 months. Among corticosteroids, a treatment of 14 days of oral prednisolone (40-60 mg/day) has been considered effective and well tolerated. Considering that an early diagnosis and a shorter lag time to treatment are essential for successful outcomes in these patients, further studies on efficacy of the different therapeutic approaches with evaluation of final outcome after cessation of therapy are needed.

Perceptual learning leads to long lasting visual improvement in patients with central vision loss

BACKGROUND

Macular Degeneration (MD), a visual disease that produces central vision loss, is one of the main causes of visual disability in western countries. Patients with MD are forced to use a peripheral retinal locus (PRL) as a substitute of the fovea. However, the poor sensitivity of this region renders basic everyday tasks very hard for MD patients.

OBJECTIVE

We investigated whether perceptual learning (PL) with lateral masking in the PRL of MD patients, improved their residual visual functions.

METHOD

Observers were trained with two distinct contrast detection tasks: (i) a Yes/No task with no feedback (MD: N = 3; controls: N = 3), and (ii) a temporal two-alternative forced choice task with feedback on incorrect trials (i.e., temporal-2AFC; MD: N = 4; controls: N = 3). Observers had to detect a Gabor patch (target) flanked above and below by two high contrast patches (i.e., lateral masking). Stimulus presentation was monocular with durations varying between 133 and 250 ms. Participants underwent 24- 27 training sessions in total.

RESULTS

Both PL procedures produced significant improvements in the trained task and learning transferred to visual acuity. Besides, the amount of transfer was greater for the temporal-2AFC task that induced a significant improvement of the contrast sensitivity for untrained spatial frequencies. Most importantly, follow-up tests on MD patients trained with the temporal-2AFC task showed that PL effects were retained between four and six months, suggesting long-term neural plasticity changes in the visual cortex.

CONCLUSION

The results show for the first time that PL with a lateral masking configuration has strong, non-invasive and long lasting rehabilitative potential to improve residual vision in the PRL of patients with central vision loss.

VIGABATRIN TOXICITY IN INFANCY IS ASSOCIATED WITH RETINAL DEFECT IN ADOLESCENCE: A Prospective Observational Study

PURPOSE

The purpose was to determine whether vigabatrin (VGB) (Sabril)-attributed retinal toxicity defined by electroretinogram in early childhood is associated with visual system defect in adolescents after discontinuation of VGB.

METHODS

This prospective cross-sectional study included 24 children previously treated with VGB and monitored in early childhood by electroretinogram for VGB-attributed retinal defects. Ten had been diagnosed with VGB-attributed retinal defect (Group I) and 14 had no VGB-attributed retinal defect (Group II). Outcome measures were extent of monocular visual fields using Goldmann kinetic perimetry and RNFL thickness at the optic nerve head, using optical coherence tomography.

RESULTS

Of those able to complete testing (6 eyes Group I and 16 eyes Group II), Goldmann results revealed results of visual field loss in Group I and not in Group II. The optical coherence tomography results demonstrated attenuation of the RNFL in all 6 eyes of Group I participants and in only 1 eye of 10 Group II participants. Optical coherence tomography data were nonoverlapping between Group 1 and Group II eyes.

CONCLUSION

The VGB-attributed retinal toxicity identified by means of electroretinogram in infancy was associated with visual field loss and RNFL attenuation of the retinal nerve when tested in adolescence.

Electrophysiological Evidences of Visual Field Alterations in Children Exposed to Vigabatrin Early in Life

BACKGROUND

We assessed central and peripheral visual field processing in children with epilepsy who were exposed to vigabatrin during infancy.

METHODS

Steady-state visual evoked potentials and pattern electroretinograms to field-specific radial checkerboards flickering at two cycle frequencies (7.5 and 6 Hz for central and peripheral stimulations, respectively) were recorded from Oz and at the eye in seven school-age children (10.1 ± 3.5 years) exposed to vigabatrin early in life, compared with children early exposed to other antiepileptic drugs (n = 9) and healthy children (n = 8). The stimulation was made of two concentric circles (0 to 5 and 30 to 60 degrees of angle) and presented at four contrast levels (96%, 64%, 32%, and 16%).

RESULTS

Ocular responses were similar in all groups for central but not for the peripheral stimulations, which were significantly lower in the vigabatrin-exposed group at high contrast level. This peripheral retinal response was negatively correlated to vigabatrin exposure duration. Cortical responses to central stimulations, including contrast response functions in the children with epilepsy in both groups, were lower than those in normally developing children.

CONCLUSIONS

Alteration of ocular processing was found only in the vigabatrin-exposed children. Central cortical processing, however, was impaired in both epileptic groups, with more pronounced effects in vigabatrin-exposed children. Our study suggests that asymptomatic long-term visual toxicity may still be present at school age, even several years after discontinuation of drug therapy.

Visuocortical function in infants with a history of neonatal jaundice

PURPOSE

High concentrations of unconjugated bilirubin are neurotoxic and cause brain damage in newborn infants. However, the exact level of bilirubin that may be neurotoxic in a given infant is unknown. The aim of this study was to use a quantitative measure of neural activity, the swept parameter visual evoked potential (sVEP) to determine the relationship between neonatal bilirubin levels and visual responsivity several months later.

METHODS

We compared sVEP response functions over a wide range of contrast, spatial frequency, and Vernier offset sizes in 16 full-term infants with high bilirubin levels (>10 mg/dL) and 18 age-matched infants with no visible neonatal jaundice, all enrolled at 14 to 22 weeks of age. The group means of sVEP thresholds and suprathreshold response amplitudes were compared. The correlation between individual sVEP thresholds and bilirubin levels in jaundiced infants was studied.

RESULTS

Infants who had a history of neonatal jaundice showed lower response amplitudes (P < 0.05) and worse or immeasurable sVEP thresholds compared with control infants for all three measures (P < 0.05). Swept parameter visual evoked potential thresholds for Vernier offset were correlated with bilirubin level (P < 0.05), but spatial acuity and contrast sensitivity measures in the infants with neonatal jaundice were not (P > 0.05).

CONCLUSIONS

These results indicate that elevated neonatal bilirubin levels affect measures of visual function in infancy up to at least 14 to 22 weeks of postnatal age.

Sweep visually evoked potentials and visual findings in children with West syndrome

BACKGROUND

West syndrome (WS) is a type of early childhood epilepsy characterized by progressive neurological development deterioration that includes vision.

AIM

To demonstrate the clinical importance of grating visual acuity thresholds (GVA) measurement by sweep visually evoked potentials technique (sweep-VEP) as a reliable tool for evaluation of the visual cortex status in WS children.

METHODS

This is a retrospective study of the best-corrected binocular GVA and ophthalmological features of WS children referred for the Laboratory of Clinical Electrophysiology of Vision of UNIFESP from 1998 to 2012 (Committee on Ethics in Research of UNIFESP n° 0349/08). The GVA deficit was calculated by subtracting binocular GVA score (logMAR units) of each patient from the median values of age norms from our own lab and classified as mild (0.1-0.39 logMAR), moderate (0.40-0.80 logMAR) or severe (>0.81 logMAR). Associated ophthalmological features were also described.

RESULTS

Data from 30 WS children (age from 6 to 108 months, median = 14.5 months, mean ± SD = 22.0 ± 22.1 months; 19 male) were analyzed. The majority presented severe GVA deficit (0.15-1.44 logMAR; mean ± SD = 0.82 ± 0.32 logMAR; median = 0.82 logMAR), poor visual behavior, high prevalence of strabismus and great variability in ocular positioning. The GVA deficit did not vary according to gender (P = .8022), WS type (P = .908), birth age (P = .2881), perinatal oxygenation (P = .7692), visual behavior (P = .8789), ocular motility (P = .1821), nystagmus (P = .2868), risk of drug-induced retinopathy (P = .4632) and participation in early visual stimulation therapy (P = .9010).

CONCLUSIONS

The sweep-VEP technique is a reliable tool to classify visual system impairment in WS children, in agreement with the poor visual behavior exhibited by them.

Vigabatrin-induced retinal toxicity is partially mediated by signaling in rod and cone photoreceptors

Vigabatrin (VGB) is a commonly prescribed antiepileptic drug designed to inhibit GABA-transaminase, effectively halting seizures. Unfortunately, VGB treatment is also associated with the highest frequencies of peripheral visual field constriction of any of the antiepileptic drugs and the mechanisms that lead to these visual field defects are uncertain. Recent studies have demonstrated light exposure exacerbates vigabatrin-induced retinal toxicity. We further assessed this relationship by examining the effects of vigabatrin treatment on the retinal structures of mice with genetically altered photoreception. In keeping with previous studies, we detected increased toxicity in mice exposed to continuous light. To study whether cone or rod photoreceptor function was involved in the pathway to toxicity, we tested mice with mutations in the cone-specific Gnat2 or rod-specific Pde6g genes, and found the mutations significantly reduced VGB toxicity. Our results confirm light is a significant enhancer of vigabatrin toxicity and that a portion of this is mediated, directly or indirectly, by phototransduction signaling in rod and cone photoreceptors.

Electroretinographic (ERG) responses in pediatric patients using vigabatrin

The antiepileptic drug vigabatrin is known to cause retinal and visual dysfunction, particularly visual field defects, in some patients. Electroretinography (ERG) is used in an attempt to identify adverse effects of vigabatrin (VGB) in patients who are not candidates for conventional perimetry. We report data from 114 pediatric patients taking VGB referred for clinical evaluation; median age at test was 22.9 (2.4 to 266.1) months, and median duration of VGB use was 9.7 (0.3 to 140.7) months. Twenty-seven of them were tested longitudinally (3 to 12 ERG tests). ERG responses to full-field stimuli were recorded in scotopic and photopic conditions, and results were compared to responses from healthy control subjects. We found that abnormalities of photoreceptor and post-receptor ERG responses are frequent in these young patients. The most frequently abnormal scotopic parameter was post-receptor sensitivity, log σ, derived from the b-wave stimulus-response function; the most frequently abnormal photopic parameter was the implicit time of the OFF response (d-wave) to a long (150 ms) flash. Abnormal 30-Hz flicker response amplitude, previously reported to be a predictor of visual field loss, occurred infrequently. For the group as a whole, none of the ERG parameters changed significantly with increasing duration of VGB use. Four of the 27 patients tested longitudinally showed systematic worsening of log σ with duration of VGB use. In a subset of patients who underwent perimetry (N = 39), there was no significant association of any ERG parameter with visual field defects. We cannot determine whether the ERG abnormalities we found were due solely to the effects of VGB. We caution against over-reliance on the ERG to monitor pediatric patients for VGB toxicity and recommend further development of a reliable test of peripheral vision to supplant ERG testing.

Retinal nerve fibre layer attenuation: clinical indicator for vigabatrin toxicity

PURPOSE

To investigate whether persistent visual field defects among patients exposed once to the antiepileptic drug vigabatrin (VGB) were associated with peripapillary retinal nerve fibre layer thickness (RNFLT) attenuation.

METHODS

Nine individuals with partial epilepsy and VGB-attributed visual field loss (group 1; 18 eyes) and seven age- and gender-matched individuals with epilepsy and no previous VGB exposure (group 2; 14 eyes) were included in the study. Full-field 120 point screening perimetry out to 60 degrees from central fixation using the Humphrey Field Analyzer was performed. RNFLT was quantified by optical coherence tomography (OCT) using Fast RNFLT protocol, Stratus OCT (3.0) after pupillary dilation. The results from the right eye are presented in this article.

RESULTS

Among the patients with VGB-attributed visual field loss, five patients had only peripheral field defect (group 1a) and the remaining four had advanced field defects both in the periphery and within 30° from central fixation (group 1b). None of the patients in the control group had manifest visual field loss. The mean RNFLT among the patients with VGB-attributed visual field loss was significantly attenuated compared to the controls [mean total RNFLT: group 1: 75.6 ± 12.7 μm, group 2: 103.5 ± 9.7 μm, mean difference 27.9 μm, (CI 15.9-39.9; p < 0.001)]. RNFLT values classified as borderline according to normative database (Stratus OCT) occurred more frequently among individuals with VGB-attributed visual field loss than in controls (frequency in group 1: 6/9; group 2: 0/7, p = 0.011). The nasal, superior and inferior quadrants of RNFLT in individuals with VGB-attributed visual field loss were significantly attenuated, while no difference was detected in temporal quadrants compared to controls. Both individuals with peripheral and those with advanced visual field losses in the VGB group had attenuated mean total RNFLT compared to controls (p = 0.006, p = 0.002, respectively). Occurrence of borderline classification of total RNFLT ≤5th percentile was more frequent among individuals with advanced visual field loss than among controls (p = 0.048).

CONCLUSION

Persistent visual field loss attributed to VGB is associated with reduced peripapillary RNFLT and was detected both among patients with advanced and among patients with only peripheral visual field defects. Measurements of RNFLT with OCT might be considered as a diagnostic supplement in the follow-up of patients exposed to vigabatrin.

Recommendations for visual evaluations of patients treated with vigabatrin

PURPOSE OF REVIEW

Although vigabatrin has been used for many years in Europe, this antiepileptic medication was approved for use in the USA only 1 year ago because of concerns for irreversible peripheral visual field loss that can result in functional visual disability.

RECENT FINDINGS

Visual function testing involves both subjective and objective techniques, some of which can be standardized across multiple centers. With these subjective and objectives issues as a reference, the current literature about the pathogenesis of vigabatrin visual toxicity is reviewed in order to develop a practical and reliable testing program for detecting peripheral visual field changes early in their course; thereby, hopefully limiting disabling visual field loss.

SUMMARY

Based upon the existing literature as well as the currently available data about the evaluation of visual function, an algorithm has been developed to serve as a starting point for clinicians to evaluate patients treated with vigabatrin for refractory epilepsy.