A recently introduced optometric technique, colorimetry, enables the perceptual effects of ophthalmic tints to be evaluated subjectively, optimized, and then prescribed in tinted
spectacles. The new technique is beneficial in reducing visual stress in patients with
dyslexia and
migraine. We describe an open trial designed to ascertain: (1) whether the colorimetry assessment, as it is now given, is safe for the investigation of photosensitive patients in optometry clinics where colorimetry equipment is most readily available, but where EEG control is not practical; (2) what proportion of patients with
photosensitive epilepsy is likely to benefit to the extent already described in individual cases; (3) whether a tint selected by colorimetry could be shown to reduce the incidence of paroxysmal epileptiform EEG activity in response to flicker and patterns, thereby validating the subjective methods and corroborating the reported seizure reduction. Twenty-four females and nine males (aged 12-43 years) took part. All the patients had suffered visually-provoked
seizures, had exhibited a photoparoxysmal response on at least one previous EEG recording, and had received a diagnosis of
photosensitive epilepsy. Twenty-two were currently experiencing
seizures. A further EEG was recorded in all except seven cases: a routine resting record, followed by
hyperventilation. Colorimetry was performed after
hyperventilation and before photic stimulation. Twenty-three (70%) reported beneficial effects during colorimetry and were prescribed glasses. There was a preponderance of
lenses with a rose or purple colour, in contrast to patients with
dyslexia. Seventeen of the 23 patients were available at follow-up, an average of 2.4 years later. Thirteen (57%) reported benefits, and said they were still using the
lenses. In six of the 13 the benefits were pronounced, including a reduction of
dizziness from fluorescent lighting, elimination of
aura when using computer screens etc. Only in three cases was there a reduction in
seizures that could reasonably be attributed to the use of
lenses; in two of these cases no medications were prescribed, and in the third the medications remained unchanged for four years, two before and two after the introduction of the glasses. In an additional four cases a reduction in
seizures was observed but medication had been changed. There was a modest reduction in EEG photosensitivity with the coloured
lenses but also to an equivalent or lesser extent with grey in all of the eight patients examined in this way. One patient had
seizures during colorimetry, but the
seizures were not accompanied by scalp EEG changes.