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Visual Optics

Higher-order ocular aberrations

Binocular wavefront sensing

The performance of the human eye is limited by a number of optical and neural factors. Our research laboratory is interested in the measurement of higher-order ocular aberrations (i.e. those above sphere and cylinder). These higher-order ocular aberrations are known to fluctuate over time, and they may be involved in accommodation control.

Our laboratory has facility for the measurement of higher-order aberrations, and their fluctuations, in real time. We are interested in differences in aberration dynamics that may exist between emmetropes and myopes, and stable versus progressing myopes.

Adaptive optics

Our adaptive optics system uses a deformable mirror to correct higher-order aberrations. The system can be used to effectively by-pass the imperfections in the optics of the eye, thus improving visual acuity. We are currently using this system to investigate the potential role of ocular aberrations in accommodation accuracy during nearwork.

Neural adaptation to blurred images

Elevated blur sensitivity thresholds in early-onset myopes following blur. Following prolonged exposure to blur (e.g. a myopic individual with spectacles removed) the visual system adapts, thus increasing the ability to resolve images. The change in resolution is manifest as an increase in visual acuity under defocused conditions. The effect is thought to occur at central sites within the visual system. Myopic subjects undergo larger improvements compared to emmetropes, suggesting some neural differences between these two groups.

Ocular biometry and refractive error

Myopia is becoming increasingly common, particularly in the Far-East. Inherited factors do not fully explain the increase in myopia prevalence that has been evident over the last few decades. Ocular biometric studies, using the IOLMaster for example, show that elongation of the axial length of the eye is the principal structural correlate of myopia. Our research in corneal topography has been used to correct myopia using custom-made rigid contact lenses.

There is increasing evidence for the role of environmental factors, e.g. nearwork, in the onset and progression of myopia. Our research group is particularly interested in the role of the following factors in myopia progression:

  • Peripheral ocular dimensions
  • Diurnal variation in eye size
  • Exposure to defocus
  • Task illumination
  • Accommodation
  • Visual display unit use
  • Orthokeratology

Funding

Our research is funded by the EPSRC, the College of Optometrists and various charities. We also undertake contract research and consultancy work.

Investigators