Peripheral refraction and higher order aberrations

Abstract

Peripheral image quality influences several aspects of human vision. Apart from off‐axis visual functions, the manipulation of peripheral optical errors is widely used in myopia control interventions. This, together with recent technological advancements enabling the measurement of peripheral errors, has inspired many studies concerning off‐axis optical aberrations. However, direct comparison between these studies is often not straightforward. To enable between‐study comparisons and to summarise the current state of knowledge, this review presents population data analysed using a consistent approach from 16 studies on peripheral ocular optical quality (in total over 2,400 eyes). The presented data include refractive errors and higher order monochromatic aberrations expressed as Zernike co‐efficients (reported in a subset of the studies) over the horizontal visual field. Additionally, modulation transfer functions, describing the monochromatic image quality, are calculated using individual wavefront data from three studies. The analysed data show that optical errors increase with increasing eccentricity as expected from theoretical modelling. Compared to emmetropes, myopes tend to have more hypermetropic relative peripheral refraction over the horizontal field and worse image quality in the near‐periphery of the nasal visual field. The modulation transfer functions depend considerably on pupil shape (for angles larger than 30°) and to some extent, the number of Zernike terms included. Moreover, modulation transfer functions calculated from the average Zernike co‐efficients of a cohort are artificially inflated compared to the average of individual modulation transfer functions from the same cohort. The data collated in this review are important for the design of ocular corrections and the development and assessment of optical eye models.

BCLA CLEAR - Orthokeratology

“…Further studies that quantify the accommodation response using objective automated techniques while controlling for pupil diameter are still required to understand if ortho-k significantly alters the accommodation response in children and adults, and if this contributes to the myopia control effect of ortho-k. Since measurements of peripheral refraction [338,339], HOAs [340], and the accommodation response [331] can vary with pupil size, several studies have investigated the relationship between pupil size and axial eye growth in children managed with ortho-k. In addition to the empirical data summarised in Table 5, based on theoretical modelling, a larger pupil diameter yields more positive primary spherical aberration and relative peripheral myopic defocus following ortho-k treatment [322].…”

Lower sensitivity to peripheral hypermetropic defocus due to higher order ocular aberrations

“…Some previous studies found no correlation between foveal HOA and refractive error, whereas others report a correlation between HOA and myopia . Additionally, in a recent review on peripheral optical errors, myopes had slightly worse image quality than emmetropes in the 20° visual field . Further studies with larger sample size are needed to see whether myopes are less symmetric than emmetropes in their sensitivity to peripheral defocus.…”

Disparity of Central-Peripheral Refraction Inheritance in Twins

“…33 Peripheral vision is compromised not only because of low cone density and limited ganglion cell density, 34 but also for increased optical aberrations at the peripheral retina. 17,35,36 Development of myopic refractive error is mainly related to an increase in axial length (AL), following a rule-of-thumb that every 300 microns AL growth causes one diopter rise in myopia, considering no alteration of other ocular components. 37,38 However, the AL growth is unlikely to always con ned at the macular area but extends to an unknown area at the posterior ocular wall.…”