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J. E. Rome, P. Ichhpujani, A. Jindal, P. Khator, B. E. Leiby, G. L. Spaeth; Comparative Study of Techniques for Detection of Relative Afferent Pupillary Defects. Invest. Ophthalmol. Vis. Sci. 2010;51(13):193. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
The Relative Afferent Pupillary Defect (RAPD) is an important test to determine optic nerve function. Small RAPDs are often difficult to detect in patients with mild nerve dysfunction. The study objectives were to compare the standard method of testing a RAPD with two novel techniques, and to evaluate the sensitivity and reproducibility of each method.
This prospective study enrolled 101 subjects (68 diagnosed glaucoma, 20 glaucoma suspects, and 13 controls). Three methods were used to determine the presence or absence of a RAPD. These include the standard Swinging Flashlight Method (SFM), the Magnifier-Assisted swinging flashlight Method (MAM), which modifies the SFM with a magnifying lens (+20 diopter, Volk), and the Swinging Flashlight Method with a direct Ophthalmoscope (SFM-O), which uses an ophthalmoscope with the +10 lens in place to focus on the plane of the iris. Humphrey Visual Field (24-2 SITA Standard) mean deviation (MD) of each eye and the intereye differences (ΔMD) were calculated. The optic discs were graded according to the disc damage likelihood scale (DDLS) and the mean amount of intereye disk asymmetry (ΔDDLS) was determined. Sensitivities for each method were cacluated based on the method’s ablity to appreciate a RAPD at various levels of ΔDDLS and ΔMD. Weighted kappa scores were used to determine potential observer biases and method reliablity.
MAM is the most sensitive method for determining a RAPD in terms of both ΔDDLS and ΔMD at all levels of change. At a DDLS difference of >2, MAM is 95% sensitive, where SFM is 84% and SFM-O is 75%. At a MD difference of >6 dB, MAM is 91% sensitive, SFM 65%, and SFM-O 68%. Weighted kappa scores revealed substantial agreement between methods and observers (kappa values 0.63-0.66).
Of the methods we used for detecting a RAPD, MAM was the most sensitive technique. Weighted kappa scores indicate the methods are reproducible. The observers were in substantial agreement. This study demonstrates that MAM provides a more sensitive and reproducible method of detecting a RAPD than the standard SFM.
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