Comparing habitual and i. Scription refractions

Abstract

Background: Many patients voice concerns regarding poor night vision, even when they see 20/20 or better in the exam room. During mesopic and scotopic conditions the pupil size increases, increasing the effects on visual performance of uncorrected (residual) refractive errors. The i.Scription refraction method claims to optimize traditional refractions for mesopic and scotopic conditions, by using the information that the Zeiss i.Profiler^plus gathers of ocular aberrations (low and high order). The aim of this study was to investigate any differences between habitual and i.Scription refractions and their relationship to night vision complaints.

Methods: Habitual, subjective, and i.Scription refractions were obtained from both eyes of eighteen subjects. Low and high order aberrations of the subjects were recorded with the Zeiss i.Profiler^plus. The root mean square (RMS) metric was calculated for small (3 mm) and maximum pupil sizes. Subjects rated their difficulty with driving at night on a scale of 1-10.

Results: There was a statistically significant difference between the habitual and i.Scription refractions on both the sphere and cylinder values [(t = 3.12, p < 0.01), (t = 5.39, p < 0.01)]. The same was found when comparing the subjective and i.Scription refractions [(t = 2.31, p = 0.03), (t = 2.54, p = 0.02)]. There were no significant differences found when comparing the sphere and cylinder values between the habitual and subjective refractions or on any combination of spherical equivalent refraction. The maximum pupil size of the subject population on this study, measured with the i.Profiler^plus, was 4.8 ± 1.04 mm. Ten out of the eighteen subjects had discomfort at night with an average magnitude of 4 ± 2.7. Ratings of difficulty with night vision correlated with the change in spherical equivalent correction between the habitual and i.Scription refractions (p = 0.01). A sub-analysis of myopic subjects (n = 15) showed an increase in the significance of this relationship (p = 0.002).

Conclusions: The i.Scription method improves night vision by correcting the sphere and cylinder more precisely. There was a correlation between the amount of change in the cylinder value between habitual and i.Scription prescriptions and the magnitude of the reported visual discomfort at night.

Keywords: I.Profilerplus; I.Scription; Night myopia; Optical aberrations; Pseudomyopia.

Fig. 1

Plot of spherical refraction (a), cylindrical refraction (b), and spherical equivalent (SE) refraction (c) comparison among habitual and i.Scription. Center lines show the medians; box limits indicate the 25th and 75th percentiles as determined by SPSS software; whiskers extend 1.5 times the interquartile range from the 25th and 75th percentiles, outliers are represented by dots; data points are plotted as open circles. n = 18 sample points

Fig. 2

Bland-Altman plot comparing habitual and i.Scription refraction from the spherical refraction (a), cylindrical refraction (b), and spherical equivalent (SE) refraction (c). The differences are plotted in Y-axis and the average in the x-axis

Fig. 3

Plots comparing the magnitude of discomfort (on a scale of 1 to 10 where 10 was most bothersome) as a function of the magnitude of the difference in refraction between i.Scription and habitual corrections for the spherical refraction (top), cylindrical refraction (middle), and spherical equivalent (SE) refractions (bottom)