Does transient increase in axial length during accommodation attenuate with age?

Abstract

BackgroundThe aim was to profile transient accommodative axial length changes from early adulthood to advanced presbyopia and to determine whether any differences exist between the responses of myopic and emmetropic individuals.MethodsOcular biometry was measured by the LenStar biometer (Haag‐Streit, Switzerland) in response to zero, 3.00 and 4.50 D accommodative stimuli in 35 emmetropes and 37 myopes, aged 18 to 60 years. All results were corrected to reduce errors arising from the increase in crystalline lens thickness with accommodation. Accommodative responses were measured sequentially by the WAM 5500 Auto Ref/Keratometer (Grand Seiko, Hiroshima, Japan).ResultsAxial length increased significantly with accommodation (p < 0.001), with a mean corrected increase in axial length of 2 ± 18 µm and 8 ± 16 µm observed at 3.00 and 4.50 D, respectively. The magnitude of accommodative change in axial length was not dependent on refractive error classification (p = 0.959); however, a significant reduction in the magnitude and variance of axial length change was evident after 43 to 44 years of age (p < 0.002).ConclusionThe negative association between transient increase in axial length and age, in combination with reduced variance of data after age 43 to 44 years, is consistent with a significant increase in posterior ocular rigidity, which may be influential in the development of presbyopia.

IMI Accommodation and Binocular Vision in Myopia Development and Progression

“…Although it has since been suggested that these values present an overestimation due to artefactual instrument optical path length errors, 113 corrected values of 0.026 and 0.047 mm, respectively, are still in excess of those found by other studies. 101 Other researchers have reported either no significant group difference, 99 , 100 , 102 increased elongation in emmetropes, 96 or only a very small, but significantly greater, transient axial elongation in myopes. 99 …”

“…Various experimental paradigms using partial coherence interferometry 96 – 98 and optical low coherence reflectometry 99 – 102 have shown that the eye experiences a transient period of axial elongation after brief periods of sustained accommodation, both on axis 96 – 100 , 102 and in the periphery, 101 with the magnitude of change increasing with larger accommodative demand. 99 The exact mechanics by which the accommodative process instigates this phenomenon remains unclear; however, it is a long-held belief that the accommodating ciliary muscle applies an internal mechanical force upon the globe.…”

Scleral HIF-1α is a prominent regulatory candidate for genetic and environmental interactions in human myopia pathogenesis

“…The subjects first watched television at a distance of 5 m for 20 min, in a room with mean ambient illuminance of about 100 lux. Then ChT and ChBP were determined using optical coherence tomography angiography (OCTA, Spectralis HRA+OCT System, Heidelberg Engineering, Baden-Württemberg, Germany) with a Badal system [ 27 , 28 ]. This system was composed of a movable target and a fixed positive power lens that was placed at its focal distance away from the eye.…”

Presbyopia: Effectiveness of correction strategies

“…Indeed, for a 20 year old eye, Heys and colleagues' ex vivo study showed that crystalline lens stiffness (measured as log shear modulus) was approximately 1.5 Pa at the nucleus and 2.0 Pa at the cortex; this inverted in the older eye where a 70 year old lens would change to approximately 4.2 Pa at the nucleus and 3.2 Pa at the cortex. Increasing rigidity of the crystalline lens is, therefore, considered the main cause of presbyopia in humans (Burd et al, 2011;Laughton et al, 2017;. That said, significant variability in data derived from such studies remains.…”