Purpose: To determine the effect of photochromatic modulation with tinted lenses on the sensory symptoms of photophobia in blepharospasm patients.
Design: Nonrandomized case-control study.
Participants: Thirty-four subjects (24 benign essential blepharospasm patients and 10 normal controls).
Methods: Subjects were seated in front of a calibrated light source. Beginning at 0%, the intensity of the light source was increased gradually until the patient reported symptomatic photophobia. The intensity of the light source was then measured with a light meter. This procedure was performed first with no chromatic lens and then with 7 different chromatic lenses, each blocking specific wavelengths of the visible spectrum. The subject was then asked which lens provided the greatest symptomatic improvement of photophobia. Statistical significance was calculated with analysis of variance and t test analysis.
Main outcome measures: Objective measurement of light intensity tolerated and subjective assessment of photophobia were obtained for each chromatic lens tested.
Results: The light intensity tolerated by the normal subjects compared with the blepharospasm group was not statistically significant with no lens, but grew to 3.5 times that tolerated by the blepharospasm group as more of the higher wavelengths of the visible spectrum were blocked (P = 0.048). Lenses 4, 5, 6, and 7 allowed blepharospasm patients to tolerate a significantly higher intensity of light when compared with no lens (P = 0.04, P = 0.007, P = 0.03, and P = 0.01, respectively). Although the highest intensity of light tolerated was measured with lens 6, 71% of blepharospasm patients reported the greatest relief of photophobia with lens 7.
Conclusions: Blepharospasm patients tolerate a lower intensity of light when compared with normal subjects; this differential in light tolerance becomes significantly more pronounced as the higher wavelengths of the visible spectrum are blocked. The symptoms of photophobia in blepharospasm patients can be reduced significantly with photochromatic modulation. Despite lens 6 allowing the patients to tolerate a higher intensity of light, the majority of patients preferred lens 7 for symptomatic relief of photophobia. These findings suggest that sensory photophobia may be related more to the wavelength than to the intensity of the light exposure.