Abstract
Purpose :
NETRA is an inexpensive smartphone-based autorefractor operated by the patient. The purpose of the study is to compare the refractive error of NETRA with the table-mounted autorefractor and with subjective refraction by optometrists.
Methods :
100 consecutive adult patients were recruited from the Optometry Clinic at Stanford University. A trial lens subjective refraction was obtained by the optometrist, and this was compared with the self-refraction using NETRA, and automated refraction from the table-mounted autorefractor (Topcon KR-800S). All refractions were non-cycloplegic. Spherical equivalent and vector components of astigmatism were analyzed by M, J0 (Cartesian astigmatism) and J45 (oblique astigmatism). Bland-Altman analysis was performed to compare the three refractions.
Results :
The mean age of the subjects was 54.6 years (range 19-92, standard deviation = 19.3). The study population consisted of 49% females and 51% males. Range of best-corrected visual acuity (BCVA) was 20/200 to 20/15, 68% of subjects had a BCVA of at least 20/20. Range of subjective refractive error was -16.25D to 2.25D. The M readings of NETRA autorefractor (mean =-0.7 D, standard deviation (SD) =2.4) were less minus compared with the table-mounted autorefractor (mean =-1.0 D, SD=2.6) and subjective refraction (mean =-1.1D, SD=2.6). The mean spherical equivalent (SE) difference between the measurements with NETRA and those using table-mounted autorefractor was 0.11D, SD=1.11 (95% LoA =2.18). Mean SE difference in NETRA refraction and subjective refraction was 0.34D, SD=0.95 (95% LoA =1.87). The difference in measurement between table-mounted refraction and subjective refraction was 0.13D, SD=0.58 (95% LoA=1.14). There were no significant differences in the J0 and J45 comparisons of subjective refraction versus the NETRA refraction, and table-mounted versus the NETRA.
Conclusions :
Non-cycloplegic refractions from the autorefractor and subjective refraction were similar. The NETRA refraction was less minus compared to the other two but produced very similar astigmatism results, and thus the sphere may need to be rechecked before dispensing a prescription directly from NETRA.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.