OBJECTIVE ASSESSMENT OF RETINAL FUNCTION IN PATIENTS TAKING VIGABATRIN
Abstract number :
2.237
Submission category :
Year :
2002
Submission ID :
1866
Source :
www.aesnet.org
Presentation date :
12/7/2002 12:00:00 AM
Published date :
Dec 1, 2002, 06:00 AM
Authors :
Linda J. Stephen, Kevin Kelly, Jo McDonagh, Fiona Dolan, Stuart Parks, Graeme J. Sills, Martin J. Brodie. Department of Medicine & Therapeutics, Western Infirmary, Glasgow, United Kingdom; Department of Ophthalmology, Gartnavel General Hospital, Glasgow,
RATIONALE: Vigabatrin has been reported to produce bilateral visual field defects in more than 30% of patients using subjective ophthalmological techniques. We report the use of a new objective test of retinal function in this patient population.
METHODS: Retinal function was investigated in 57 treated patients (32 currently taking vigabatrin, 25 never taken vigabatrin) with localisation-related epilepsy using a new high resolution imaging technique (wide field multifocal electroretinogram - mfERG). The groups were matched for seizure control and duration of epilepsy (vigabatrin: 17m/15f, median age 37 years, median duration 20 years; control: 12m/13f, median age 37 years, median duration 20 years). The mfERG results were compared with a normative data set (120 healthy drug-free controls) in respect of bilateral abnormalities in the timing of responses. Additional investigations included Humphrey visual field analysis (static perimetry) and fundoscopy.
RESULTS: Of the 32 patients taking vigabatrin, 15 had moderate or severe bilateral abnormalities on Humphrey visual field assessment, while 12 had significant delays in mfERG responses from both eyes. Those with abnormal mfERGs took a greater median vigabatrin dose (3g versus 2g daily) for longer (9 years versus 7 years) and, therefore, had a higher median drug burden (6048g versus 4368g) than unaffected patients. Therapeutic drug monitoring confirmed compliance with vigabatrin treatment. Of the 25 controls Humphrey visual field assessment was abnormal in 1, unreliable in 1 (multiple fixation losses) and was abandoned in 2 due to poor tolerance. Bilateral mfERG retinal abnormalities were not detected in any of these patients.
CONCLUSIONS: Wide-field multifocal ERG provides an objective assessment of retinal function that is independent of the patient[ssquote]s ability to perform visual field perimetry. This investigation is well tolerated and does not suffer the inherent variability and poor reproducibility of subjective visual field testing. This technique can be used to detect retinal dysfunction in treated epileptic patients and affords the opportunity to determine progression or regression.
[Supported by: The Ross Foundation]