Emmetropization and nonmyopic eye growth

Refractive development in utero is an impressive feat of prenatal growth as it brings the tiny infant eye to near hypermetropia without the assistance of a retinal image to guide visual development. After birth, the eye undergoes emmetropisation, a period during which most eyes see their cycloplegic refractive error evolve towards a value close to +1 D. Once this is reached, eye growth enters a phase of homeostasis when the eye continues to grow while maintaining its refractive error at mild hypermetropia through a gradual loss of crystalline lens power.Although emmetropisation was first described over 100 years ago by Straub, 1 its exact nature remains unclear. Straub and subsequent authors 2-4 knew that the refractive error could only be minimised if the refractive components of the eye could coordinate their growth rates, but there was no agreement on how this was accomplished.

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Refractive development I: Biometric changes during emmetropisation

Rozema

2023

“…However, young eyes can continue to grow into the teenage years without generating myopia. 17,18 If emmetropic growth is considered a treatment target, then efficacy may be considered as 100% if the treated axial length growth slows to levels seen in an age-matched emmetropic population. By this criterion, the dual focus contact lens achieved efficacies ranging from 86% to 112%.…”

Section: Discussionmentioning

confidence: 99%

“…For example, cross-over 14 comparisons with pre-treatment 15 and delay in reaching a criterion level 16 have all been employed to assess treatment efficacy. Also, due to the wealth of published data on axial growth in myopic and emmetropic eyes, [17][18][19] the growth of treated eyes can be compared with the growth of untreated myopic and age-matched emmetropic eyes from other studies. [20][21][22][23] Myopia is a progressive condition which can start in early childhood with a mean onset of approximately 8 years of age 24 and a mean age of stabilisation of approximately 15 years.…”

mentioning

confidence: 99%

Six‐year cumulative treatment effect and treatment efficacy of a dual focus myopia control contact lens

Chamberlain,

Hammond,

Arumugam

et al. 2023

PurposeAccumulated axial growth observed during a 6‐year clinical trial of a dual focus myopia control contact lens was used to explore different approaches to assess treatment efficacy.MethodsAxial length measurements from 170 eyes in a 6‐year clinical trial of a dual focus myopia control lens (MiSight 1 day, CooperVision) were analysed. Treatment groups comprised one having undergone 6 years of treatment and the other (the initial control group) having 3 years of treatment after 3 years of wearing a single vision control lens. Efficacy was assessed by comparing accumulated ocular growth during treatment to that expected of untreated myopic and emmetropic eyes. The impact of treatment on delaying axial growth was quantified by comparing the increased time required to reach criterion growths for treated eyes and survivor analysis approaches.ResultsWhen compared to the predicted accumulated growth of untreated eyes, 6 years of treatment reduced growth by 0.52 mm, while 3 years of treatment initiated 3 years later reduced growth by 0.19 mm. Accumulated differences between the growth of treated and untreated myopic eyes ranged between 67% and 52% of the untreated myopic growth, and between 112% and 86% of the predicted difference in growth between untreated myopic and age‐matched emmetropic eyes. Treated eyes took almost 4 years longer to reach their final accumulated growth than untreated eyes. Treatment increased the time to reach criterion growths by 2.3–2.7 times.ConclusionEstimated growth of age‐matched emmetropic and untreated myopic eyes provided evidence of an accumulated slowing in axial elongation of 0.52 mm over 6 years, and the treated growth remained close to that expected of emmetropic eyes. Six years of dual focus myopia control delayed the time to reach the final growth level by almost 4 years.

“…It is difficult to determine how much of axial elongation observed in myopic eyes belongs to physiological growth. While natural physiological growth of the eye can be observed in non‐myopic children, 2 data on age‐specific eye growth are limited. In the Singapore Cohort Study of the Risk Factors for Myopia (SCORM), annual axial elongation of emmetropic children aged 8–12 years was between 0.12 and 0.04 mm 3 .…”

Section: Introductionmentioning

confidence: 99%

Eye growth pattern of myopic children wearing spectacle lenses with aspherical lenslets compared with non‐myopic children

Wong,

Li,

Huang

et al. 2023

IntroductionTo evaluate eye growth of children wearing spectacle lenses with highly aspherical lenslets (HAL), slightly aspherical lenslets (SAL) and single‐vision lenses (SVL) compared to eye growth patterns in non‐myopes in Wenzhou, China.MethodsThe randomised trial had 170 myopic children (aged 8–13 years) randomly assigned to the HAL, SAL or SVL group. Normal eye growth was examined using 700 non‐myopic schoolchildren (aged 7–9 years) in the Wenzhou Medical University‐Essilor Progression and Onset of Myopia (WEPrOM) cohort study using logistic function models. Slow, normal and fast eye growth was defined as range of values <25th, 25th–75th and >75th percentiles, respectively.ResultsThe predicted upper limits of slow eye growth (25th percentile) among non‐myopes aged 7–10 years and 11–13 years were 0.20–0.13 and 0.08–0.01 mm (after 2‐year period; 0.37–0.33 and 0.29–0.14 mm), respectively, while the upper limits of normal eye growth (75th percentile) were 0.32–0.31 and 0.28–0.10 mm (after 2‐year period; 0.58–0.55 and 0.50–0.24 mm), respectively. The 2‐year trial had 157 children, 96 of whom wore their lenses full time (everyday ≥12 h/day). The mean 2‐year axial length change for HAL, SAL and SVL was 0.34, 0.51 and 0.69 mm (0.28, 0.46 and 0.69 mm in full‐time wear), respectively. Slow eye growth was found in 35%, 17% and 2% (44%, 29% and 3% in full‐time wear); normal eye growth in 35%, 26% and 12% (44%, 32% and 9% in full‐time wear) and fast eye growth in 30%, 57% and 86% (12%, 39% and 88% in full‐time wear), respectively (p < 0.001).ConclusionsThe eye growth pattern in approximately 90% wearing HAL full time (compared with about 10% wearing SVL full time) was similar or slower than that of non‐myopic children both after 1‐ and 2‐year periods.