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Aim: To investigate the prevalence of vigabatrin-attributed visual field defect (VAVFD) in infantile spasms and the utility of optical coherence tomography (OCT) in detecting vigabatrin-related damage., Method: We examined visual fields by Goldmann or Octopus perimetry and the thickness of peripapillary retinal nerve fiber layer (RNFL) with spectral-domain OCT at school age or adolescence., Results: Out of 88 patients (38 females, mean age at study 15y, SD 4y 3mo, range 6y 4mo-23y 3mo [n=65] or deceased [n=21] or moved abroad [n=2]) exposed to vigabatrin in infancy, 28 were able to perform formal visual field testing. Two had visual field defect from structural causes. We found mild VAVFD in four patients and severe VAVFD in one patient. Median vigabatrin treatment duration for those with normal visual field was 11 months compared to 19 months for those with VAVFD (p=0.04). OCT showed concomitant attenuated RNFL in three children with VAVFD, and was normal in one. The temporal half of the peripapillary RNFL was significantly thinner in the VAVFD group compared to the normal visual field group., Interpretation: The overall prevalence of VAVFD is lower after exposure in infancy compared to 52% which has been reported after exposure in adulthood. The risk increases with longer treatment duration. Further studies should identify infants particularly susceptible to VAVFD and clarify the role of OCT., (© 2021 Mac Keith Press.)

Infantile spasms syndrome (IS) (also known as West syndrome) is an epileptic encephalopathy with a heterogeneous etiology. One of the most common specific causes is tuberous sclerosis, diagnosed in almost 10% of the affected infants. Adrenocorticotropic hormone or steroids have been the preferred treatments for IS for several decades. Clinical studies have shown that vigabatrin is superior to placebo in decreasing the frequency of infantile spasms. In tuberous sclerosis, vigabatrin may be considered the first-line treatment for IS. The mode of action is increasing concentrations of the inhibitory neurotransmitter GABA in the brain. The use of vigabatrin is limited by a serious adverse effect, permanent visual field constriction, which may affect 6-7% of exposed infants. Treatment choices are based on balancing the potential adverse effects against the risk of catastrophic cognitive and behavioral outcomes caused by uncontrolled spasms.

Purpose: The use of vigabatrin (VGB) as an antiepileptic drug (AED) has been limited by evidence showing that it causes vigabatrin-attributed visual field loss (VAVFL) in at least 20-40% of patients exposed at school age or later. VGB is an effective drug for infantile spasms, but there are no reports on later visual field testing after such treatment. Our aim was to investigate the risk of VAVFL in school-age children who had received VGB in infancy., Methods: Visual fields of 16 children treated with VGB for infantile spasms were examined by Goldmann kinetic perimetry at age 6-12 years. Normal fields were defined as the temporal meridian extending to more than 70 degrees , and mild VAVFL between 50 and 70 degrees . Abnormal findings were always confirmed by repeating the test. Exposure data were collected from hospital charts., Results: Vigabatrin was started at a mean age of 7.6 (range, 3.2-20.3) months. The mean duration of therapy was 21.0 (9.3-29.8) months and cumulative dose 655 g (209-1,109 g). Eight children were never treated with other AEDs, five received only adrenocorticotropic hormone (ACTH) in addition to VGB, and three children had been treated with other AEDs. Fifteen children had normal visual fields. Mild VAVFL was observed in one child (6%) who had been treated with VGB for 19 months and who received a cumulative dose of 572 g., Conclusions: The risk of VAVFL may be lower in children who are treated with VGB in infancy compared to patients who receive VGB at a later age.