Objective changes in astigmatism during accommodation

Abstract

Purpose Previous studies have shown small but clinically significant changes in the power and axis of astigmatism when the eye accommodates. Monocular objective measurements of the eye during accommodation, when the object approaches the eye without convergence, also reveal small astigmatic changes. Moreover, it is known that the eye exhibits ocular cyclotorsion at different gaze angles. Since accommodation and convergence normally occur simultaneously, we studied the change in the magnitude and axis of astigmatism during accommodation for different convergence angles. Methods The left eye of 15 subjects between 20 and 49 years old (mean 28.5 ± 9.7 years) having ≤1.5 D astigmatism was evaluated. Measurements were made using a Shack‐Hartmann aberrometer for an accommodation range of +0.50 D to −10 D in 0.50 D steps, and for four monocular convergence demands: 0°, 5°, 10° and 15°. Statistical analysis used power vectors to quantify the change in cylinder power and axis for each accommodation and convergence demand with age. Results Jackson cross‐cylinder component J45 did not change during accommodation for all vergences tested. However, J0 changed by an average of −0.02 D per dioptre of accommodation (D/Dacc) for convergence demands of 0°, 5° and 10° and −0.03 D/Dacc for the 15° demand. This corresponds to an average cylinder power change of −0.05 D/Dacc for convergences of 0°, 5° and 10° and −0.08 D/Dacc for 15° of convergence. The cylinder axis always changed towards 90° (against‐the‐rule), and age did not play a significant role. Conclusions Except for accommodation demands >4 D, we did not find a clinically significant change in astigmatism for convergence angles up to 15º. The small changes in cylinder power and axis may be due to shifts in the position of the crystalline lens during accommodation.

Accuracy and precision of automated subjective refraction in young hyperopes under cycloplegia

“… 12 In agreement with these findings, other authors found no differences in terms of J0 and J45 between other instruments to conduct automated subjective refraction and the traditional subjective refraction as the gold standard, also presenting similar 95% limits of agreement. 8 , 13 A recent study by Lara-Lacárcel et al 28 described how instrumental accommodation could induce changes in astigmatism power and its axis. They reported mean changes in J0 by about −0.02 D per dioptre of accommodation and minimal changes in J45.…”

Validation of the PowerRef 3 for Measuring Accommodation: Comparison With the Grand Seiko WAM-5500A Autorefractor

“…Another source of variability could be due to the required conversion from refractive measurement in spherical equivalent to vertical meridian for the present WAM-5500A data using additional, static autorefractor measurements (see Data Processing). The conversion method assumed that cylinder power and axis collected during static WAM-5500A measurements remained constant for dynamic recording (see Equations 1 and 2 ), 50 and static measures were collected at each tested accommodative demand to determine cylinder power and axis with greater accuracy. Aldaba et al (2015) did not report how conversions were applied (comparisons were conducted using spherical equivalent), but it nevertheless raises the possibility that the present conversion approach may have introduced additional variability.…”

Assessment of a Clinical Test for Detection of Alteration in Visual Perception Due to Astigmatism

“…However, changes in astigmatism due to accommodation have been shown to be clinically relevant for large accommodative demands exceeding 4.00 DS. 34 Future investigations should compare these outcomes in participants without the ability to accommodate by use of cycloplegic agents and compare between cohorts of similar age distributions.…”