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Assessment of objective and subjective eccentric refraction
Linda Lundström1, Jörgen Gustafsson, Ingrid Svensson
1Biomedical and X-Ray Physics, Department of Physics, Royal Institute of Technology, Stockholm, Sweden. linda@biox.kth.se
Summary
Accurately measuring peripheral refractive errors is crucial. The Hartmann-Shack sensor proved most effective among four tested eccentric refraction methods for healthy subjects.
Area of Science:
- Ophthalmology
- Optometry
- Vision Science
Background:
- Accurate peripheral refractive error measurement is vital for perimetry, visual field loss assessment, and emmetropization studies.
- Traditional foveal refraction methods yield uncertain results at eccentric angles due to aberrations and reduced retinal function.
Purpose of the Study:
- To compare and evaluate four distinct methods for eccentric refraction.
- To assess the efficacy of subjective and objective techniques in measuring peripheral refractive errors.
Main Methods:
- Tested four eccentric refraction methods on 50 healthy subjects: a novel subjective contrast sensitivity procedure, photorefraction (PowerRefractor), wavefront sensing (Hartmann-Shack), and retinoscopy.
- Measured peripheral refractive error in the nasal visual field at 20 and 30 degrees eccentricities.
Main Results:
- All methods showed reasonable agreement, with notable differences in astigmatism axis for retinoscopy.
- The PowerRefractor failed in 15 subjects at 30 degrees and underestimated high myopia.
- The Hartmann-Shack sensor indicated a consistent myopic shift (~0.5 D), while the subjective method exhibited greater variability.
Conclusions:
- All evaluated methods can assess eccentric refraction.
- The Hartmann-Shack wavefront sensing technique emerged as the most practical and useful method.
- Peripheral detection contrast sensitivity is sensitive to minor defocus, as evidenced by the agreement between objective and subjective eccentric refraction measures.