Influence of power and the time of application of fogging lenses on accommodation

A metric-based image-formation model explains the improvement in subjective refraction using temporal defocus waves

SIGNIFICANCE

Direct subjective refraction (DSR) is a novel method for refractive error measurements that uses temporal changes in defocus and a flicker minimization task. The computational models developed here are a framework for improving this clinical method.

PURPOSE

This study aimed to model the measurement of refractive error with the DSR method, which uses rapid changes in optical power and a bichromatic (red/blue) stimulus.

METHODS

The polychromatic point spread function of the eye was used to simulate the retinal image projected in DSR method, and an image quality (IQ) metric was defined based on the spatial frequencies of the retinal image. Three tasks were modeled: blur minimization (BM), monochromatic flicker minimization (MFM), and polychromatic flicker minimization or DSR. A metric was defined for each task and studied through focus in a ±3-D range. Whereas BM was modeled using only the IQ of the projected images, MFM and DSR metrics were a function of the IQ of the average retinal image and a metric to quantify the similarity (flicker) in the image. The width of the through-focus peak was used to compare between tasks, and different values of pupil size and spherical aberration were studied.

RESULTS

The through-focus 90% peak width was 0.48, 0.16, and 0.19 D for BM, MFM, and DSR tasks, respectively, which agreed well with previous experimental data. The 90% peak width increased for small pupils and with increasing values of spherical aberration in BM and MFM, but it remained relatively constant in DSR model.

CONCLUSIONS

The developed models explained previous experimental findings that reported a higher repeatability of the DSR compared with the traditional refraction method.

Pre-Cycloplegic Exam Benefit of Photoscreening and Accommodation-Relaxing Skiascopy

Background

Seeking a quick way to estimate refractions for challenging pediatric patients, we studied two non-contact methods with particular attention to accuracy and level of stress in uncovering cycloplegic hyperopia.

Methods

Newly referred and follow-up pediatric eye patients had timed school bus accommodation-relaxing skiascopy (SBARS) and Plusoptix A12 (Px) photoscreener testing before cyclopentolate 1% confirmatory examinations. The ABCD ellipsoid univariate method based on relative blur and vector components was used to compare dry sphero-cylinder refraction estimates with cycloplegic. Receiver operating characteristic (ROC) curves were used to determine screening value.

Results

Three compared refractions were attempted in 191 racially diverse children of whom 100 were age 0.2-3.9 years and 91 were 4 to 14 years. Plusoptix failed to yield a result in 21 and an additional 21 were interpreted as an excess sphere. Median spherical equivalent did not differ between Px and SBARS for 149 with Px readings but in hyperopic patients, Plusoptix uncovered 27% less hyperopia. The ellipsoid for SBARS of 0.8 was better than 2.4 for Plusoptix (Mann-Whitney p<0.001). Plusoptix was fastest (3-15 seconds) followed by SBARS (15-30 seconds) compared to 30-45 minutes for cycloplegic exam.

Conclusion

Non-contact quick refractive methods enhanced confirmatory cycloplegic pediatric exam in high-risk pediatric patients.