We read with interest the paper by Best and Acheson1 regarding the natural history of Vigabatrin-associated visual field defects in patients electing to continue their medication. The first cases of concentric bilateral visual field defects in patients taking Vigabatrin were reported in the late 1990s and since then numerous cases have been reported worldwide. The association has grown stronger and is now a well-accepted adverse drug effect of Vigabatrin therapy.2, 3, 4

In 2001, the Royal College of Ophthalmologists (RCO) published screening guidelines entitled ‘The ocular side-effects of Vigabatrin, information and guidelines for screening’.5 For adults, they recommend pretreatment baseline visual field using either static suprathreshold 2 or 3 zone perimetry (Humphrey 120 point or Octopus 07) to at least 45 radius eccentricity, or Goldman kinetic perimetry (IIIe and I4e or I2e stimuli, as appropriate). All patients should have 6 monthly follow-up assessments for the first 3 years of treatment, which can then be extended to annually in patients in whom no visual field defects are found.

We used a questionnaire survey in the South-West of England and Wales to investigate views of consultant ophthalmologists on the RCO guidelines and to review current clinical practice.

Out of 97 consultants, 54 contacted responded to the questionnaire (response rate 56%). Consultant ophthalmologists were asked about their experience with Vigabatrin-related visual field screening in the year 2002–2003. More than a third (35%) of those surveyed were unaware that the RCO had published guidelines relating to Vigabatrin-associated visual field defects. Only 15% had received new referrals for baseline visual field documentation prior to patients starting on Vigabatrin and 41% of respondents had performed or arranged visual field screening for patients already on Vigabatrin. With respect to screening intervals, 51% thought that the screening interval should be 12 months or longer, 45% agreed with a screening interval of 6 months and 4% felt that the interval should be 3 months for the first 3 years of treatment.

A lack of communication between the neurologists and ophthalmologists was stated, by 75% of respondents, as the most common reason for noncompliance with the screening guidelines. This probably relates to the failure of neurologists to refer patients for screening prior to commencing them on Vigabatrin and also to the lack of involvement of the ophthalmologist in the follow-up of these patients.

Surprisingly, a small proportion of respondents cited that an increase in workload as a reason for noncompliance with the RCO guidelines, in spite of the relatively small number of patients requiring screening. Those respondents who were involved in screening patients were performing less than five visual fields a year.

There is a disparity between current clinical practice and the RCO guidelines. None of the respondents had carried out an audit of their clinical practice regarding screening of patients on Vigabatrin. While patient numbers may be few, continued audit and clinical data collection should be encouraged in accordance with RCO guidelines. Although the exact pathogenesis of these field defects is not known, the need to screen patients on Vigabatrin is well established. Screening is important if the field defects are caused by an idiosyncratic reaction to the medication, particularly as only a certain group of patients will be affected.

It is disappointing that despite the RCO publishing guidelines, more than a third of the consultant ophthalmologists responding to the survey were unaware of their existence. Our survey of clinical practice indicates that there is only a moderate agreement with the current guidelines. A joint guideline issued by ophthalmologists and neurologists regarding screening for Vigabatrin-associated field defects may help bridge the gap between the specialties and achieve wider agreement and compliance.