Comparison of scotopic pupil measurement with slitlamp-based cobalt blue light and infrared video-based system.
OBJECTIVE
To determine the accuracy and reproducibility of scotopic pupil measurements with a slitlamp-based cobalt blue light.


METHODS
University of Texas Health Science Center-San Antonio, San Antonio, Texas, USA.


METHODS
In a prospective experimental study, 2 independent observers measured 16 subjects' pupils with a standard slitlamp-based cobalt blue light. In the same setting, the accuracy and reproducibility of the measurements were compared with those obtained with an infrared video-based system.


RESULTS
Measurements of pupil size using the infrared video-computer system were highly reproducible. With the slitlamp-based cobalt blue light, the 2 measurements obtained by observer 2 (n = 16) were very close to each other (mean difference 0.09 mm +/- 0.23 [SD]; P =.12), whereas those obtained by observer 1 (n = 16) were slightly different from each other (mean difference 0.18 +/- 0.33 mm; P =.043). The mean pupil diameter measured with cobalt blue light was not significantly different between the 2 observers (P >.05), and the measurements were highly correlated with each other (r = 0.96, P <.01). The mean difference between the measurements using cobalt blue light and the infrared video-computer system was 0.21 +/- 0.54 mm for observer 1 (P =.47) and 0.06 +/- 0.47 mm for observer 2 (P =.85). Good correlation was noted between the measurements taken from each measuring device for both observers (r = 0.87 and 0.90, P <.01).


CONCLUSIONS
Slitlamp-based cobalt blue light provided a reasonably good measurement of scotopic pupil size. It correlated well with the infrared video system when used at the lowest setting by experienced personnel. However, the observed difference between the measurements obtained by the 2 devices indicates that the cobalt blue light should be used cautiously in the refractive surgery preoperative evaluation of patients with large pupils.
Starck
Tomy
T
Cornea, Refractive Surgery Services, and University of Texas LASIK Vision Center, Department of Ophthalmology, University of Texas Health Science Center, San Antonio, Texas, USA.
Liu
Yun
Y
Prewett
Amy L
AL
G  Curup
Lettie
L
D003116:Color; D003623:Dark Adaptation / Q000502:physiology*; D003936:Diagnosis, Computer-Assisted; D006801:Humans; D007259:Infrared Rays; D008027:Light; D009885:Ophthalmology / Q000295:instrumentation* / Q000379:methods*; D011446:Prospective Studies; D011680:Pupil; D015203:Reproducibility of Results; D013690:Television