Accommodative Stimulus Research Articles

Three-Dimensional Magnetic Resonance Imaging of the Phakic Crystalline Lens during Accommodation

To quantify changes in crystalline lens curvature, thickness, equatorial diameter, surface area, and volume during accommodation using a novel two-dimensional magnetic resonance imaging (MRI) paradigm to generate a complete three-dimensional crystalline lens surface model. Nineteen volunteers, aged 19 to 30 years, were recruited. T(2)-weighted MRIs, optimized to show fluid-filled chambers of the eye, were acquired using an eight-channel radio frequency head coil. Twenty-four oblique-axial slices of 0.8 mm thickness, with no interslice gaps, were acquired to visualize the crystalline lens. Three Maltese cross-type accommodative stimuli (at 0.17, 4.0, and 8.0 D) were presented randomly to the subjects in the MRI to examine lenticular changes with accommodation. MRIs were analyzed to generate a three-dimensional surface model. During accommodation, mean crystalline lens thickness increased (F = 33.39, P < 0.001), whereas lens equatorial diameter (F = 24.00, P < 0.001) and surface radii both decreased (anterior surface, F = 21.78, P < 0.001; posterior surface, F = 13.81, P < 0.001). Over the same stimulus range, mean crystalline lens surface area decreased (F = 7.04, P < 0.005) with a corresponding increase in lens volume (F = 6.06, P = 0.005). These biometric changes represent a 1.82% decrease and 2.30% increase in crystalline lens surface area and volume, respectively. CONCLUSIONS; The results indicate that the capsular bag undergoes elastic deformation during accommodation, causing reduced surface area, and the observed volumetric changes oppose the theory that the lens is incompressible.

Accommodative responses and aberrations with natural pupils in Myopic Juvenile under reading status

Background Image clarity during near work is influenced by several factors,such as accommodative lag,pupil size and monochromatic aberrations.Since image clarity during extended reading at near distance has been cited as a possible inducement of myopia in childhood and a possible difference between myopic and emmetropic people throughout life,it is important to examine these factors in myopic and emmetropic myopic juvenile during reading at near distance. Objective The aim of this study was to investigate the relationships among wavefront aberrations,accommodative response and pupil size in early onset and progressive myopes eyes under the different reading status and explore the possible mechanism of the development of myopia as well. Methods Fiflyseven subjects aged from 12 to 16 years were enrolled and grouped as emmetropes,the onset of myopes and progressive myopes.Reading material were Chinese novels presented by rapid serial visual presentation at a distance of 25 cm. Accommodative response and pupil size were recorded by a Grand Seiko WV-500 autorefractor.The Image J software was used to calculate the pupil diameter.Wavefront aberrations were then measured with a WASCA wavefront analyzer. Results Aberrations and accommodative response showed large inter-subjeet variability.With accommodative stimulus of 4 diopter,the accommodative lag in the early-onset of myopes group and progressive myopes group were ( 1.72 ±0. 53) D and ( 1.74 ±0. 44) D, showing larger value in comparison with ( 0. 96 ±0. 55) D of emmetropes group( t＝4.25 ,t=4.47 ,P 0. 05). The mean value of pupil diameter, total RMS value, high-order RMS value, spherical aberration and coma were all significantly reduced with the stimulus varied from 0 D to 4 D( P 0. 05). Conclusion The early-onset of myopes and progressive myopes had larger accommodative lag. The lower sensitivity to defocus at near reading distance,inducing the larger accommodative lag and hyperopic defocus may be linked to the developing myopia. Key words: Myopia; Wavefront aberration ; Accommodative response ; Pupil size

The Effect of Contact Lens Correction and Accommodation upon Monochromatic Higher Order Aberrations in Myopia and Hyperopia

Purpose:To measure the effects of contact lens correction and accommodation upon SA in myopia and hyperopia.Methods:Eleven myopes (Average MSE −3.22±2.21D; mean age 20.7±1.1 years) and eleven hyperopes (Average MSE 4.20±2.20; mean age 20.1±1.5) participated. Subjects were corrected with daily disposable contact lenses and pupil dilation was induced with 2.5% phenylephrine hydrochloride. SA was measured at accommodation stimulus levels of 0D and 4D, using the Zywave Aberrometer while subjects viewed a high contrast letter target array in a +5D Badal system, aligned perpendicularly to the measurement axis of the instrument via a semi-silvered mirror.Results:For 0D of accommodation, the hyperopic group had significantly (p < 0.01) greater positive SA. Contact lens correction produced a positive shift in SA in the hyperopic group (p < 0.01), whereas there was a negative shift in SA in the myopic group (p < 0.01). Negative shifts in SA were found with accommodation in both myopic (p < 0.01) and hyperopic (p < 0.01) groups, with the shift being greater in the hyperopic group (p < 0.01).Conclusions:The net effect of contact lens correction and accommodation result in SA for near visual tasks, which is predominantly negative in myopia and positive in hyperopia.

Visual Discomfort and Blur

Natural images typically have an approximately 1/f amplitude spectrum. Images that have relatively high amplitude at low spatial frequencies in comparison with a 1/f spectrum have been found to be uncomfortable (Fernandez and Wilkins, 2008, Juricevic et al, 2010). Such images also tend to be perceived as more blurred (Webster et al, 2002, Murray and Bex, 2010). This suggests that the loss of high spatial frequency information might increase visual discomfort. This could be due to an effect on the accommodation response, which is influenced by the spatial frequency content of images (eg, Charman and Tucker, 1977). Stimuli with a relative increase in low spatial frequency information might be uncomfortable because they are a poor stimulus for accommodation. The current study investigates the relationship between perceived blur, visual discomfort, and relative amounts of high and low spatial frequency information using both simple “bull's eye target” stimuli and natural images. Loss of high spatial frequency information was found to increase both visual discomfort judgements and perceived blur in simple stimuli. Increasing blur (loss of high spatial frequency information through either sinc or Gaussian filtering) in natural images was also found to increase visual discomfort judgements. Loss of high spatial frequency information increases discomfort, and perceived blur, in both simple and complex images. These results suggest that discomfort arises in images that present a difficult stimulus for accommodation. It is important therefore to consider how stimuli are accommodated by the eye, as well how they are encoded by the visual cortex, in understanding visual discomfort.

立体映像および実物体観視時の調節・輻輳応答の静特性と動特性

The conflict between accommodation and vergence stimuli has been identified as a possible cause of visual fatigue from viewing stereoscopic images. We examined static and dynamic characteristics of accommodation and vergence responses while viewing stereoscopic displays and real objects to clarify the effect of stereoscopic images on the visual function. We used an instrument based on the Shack-Hartmann wavefront sensor to measure accommodation and vergence responses simultaneously. Accommodation responses to the static stereoscopic target with large binocular disparity were deviated from those to the real target, i.e., static characteristics. The step responses of the accommodation response showed considerable individual differences, i.e., dynamic characteristics. In addition, the asymmetries of step responses of accommodation were observed between the near-to-far and the far-to-near step directions. These results suggest that we need to examine both static and dynamic characteristics of accommodation and vergence responses to clarify the biological effect of stereoscopic images.

Contact lenses vs spectacles in myopes: is there any difference in accommodative and binocular function?

Theoretically, the accommodative and vergence demands are different between single-vision contact lenses and spectacle lenses. The aim of the present study was to determine whether these differences exist when these two correction methods are used in clinical practice. For this, different visual parameters that characterize the accommodative (accommodation amplitude, accommodative facility, and accommodative response) and binocular function (near and distance horizontal and vertical dissociated phorias, near and vertical associated phorias, near and distance negative and positive fusional vergence, vergence facility, near point of convergence, negative and positive relative accommodation, stimulus AC:A ratio and stereoacuity) were evaluated in a student population when their myopia was corrected with either spectacles or soft contact lenses (SCL). All parameters were measured on two separate occasions in 30 myopic habitual contact lens and spectacle wearers of mean age 19 ± 2.4years. Some parameters such as accommodation amplitude, accommodative response, and stimulus AC:A ratio were measured using two measurement methods which are commonly used in clinical practice. Three measurements were taken for each parameter and averaged. For the comparative statistical analysis, we used the Student's t-test (p value < 0.05). The following statistically significant differences were found with the use of SCL in comparison to spectacles: higher accommodative lags, higher negative relative accommodation, more esophoric near horizontal dissociated phoria, and lower negative fusional vergence in near vision. The results found in this study show a definite trend towards poorer accommodative and vergence function with the use of contact lenses in comparison to glasses. This downward trend, though not statistically significant in accommodative function (lower PRA values and less lens amplitude of accommodation) might suggest that temporal insufficiency in the accommodation process could be occurring while contact lenses are used, thereby possibly creating a lag in accommodation to reduce associated overconvergence. This would be manifested in more esophoric values being found in the vergence function. The higher accommodative lags found in this study with SCL could indicate that prolonged use of SCL in near tasks may provoke a continuous hyperopic retinal defocus, a risk factor for the onset and progression of myopia, as indicated in numerous studies.

Axial Length Changes During Accommodation in Myopes and Emmetropes

To investigate the influence of accommodation on axial length (AXL) and a comprehensive range of ocular biometric parameters) in populations of young adult myopic and emmetropic subjects. Forty young adult subjects had ocular biometry measured using a noncontact optical biometer (Lenstar LS 900) based on the principle of optical low coherence reflectometry under 3 different accommodation demands (0 D, 3 D, and 6 D). Subjects were classified as emmetropes (n = 19) or myopes (n = 21) based on their spherical equivalent refraction (mean emmetropic refraction -0.05 +/- 0.27 D and mean myopic refraction -1.82 +/- 0.84 D). AXL changed significantly with accommodation, with a mean increase of 11.9 +/- 12.3 mum and 24.1 +/- 22.7 mum for the 3 D and 6 D accommodation stimuli, respectively. A significant axial elongation associated with accommodation was still evident even after correction of the AXL data for potential error because of lens thickness change. The mean "corrected" increase in AXL was 5.2 +/- 11.2 mum and 7.4 +/- 18.9 mum for the 3 D and 6 D stimuli, respectively. There was no significant difference between the myopic and emmetropic populations in terms of the magnitude of change in AXL with accommodation, regardless of whether the data were corrected or not. A number of other ocular biometric parameters, such as anterior chamber depth, lens thickness, and vitreous chamber depth also exhibited significant change with accommodation. The myopic and emmetropic populations also exhibited no significant difference in the magnitude of change in these parameters with accommodation. The eye undergoes a significant axial elongation associated with a brief period of accommodation, and the magnitude of this change in eye length increases for larger accommodation demands, however, there is no significant difference in the magnitude of eye elongation in myopic and emmetropic subjects.

Accommodation response when changing spherical and chromatic aberration

Abstract Purpose The aim of this study was to evaluate accommodation response by changing two of the main directional cues for accommodation. This was done under mono‐ and polychromatic light while varying the amount of spherical aberration. Methods In this study twenty subjects with a mean age 25.0 ±2,37 SD participated. Spherical aberration was measured in the uncorrected eye and accommodation was measured with a PowerRefractor with trial frame correction and with a spherical aberration controlled contact lens (‐0.15μm). Accommodation stimuli of ‐2.0 D was used. The measurements were done in white and monochromatic light (580‐585 nm). Results The analysis showed no significant influence of either the tested amounts of spherical aberrations or having monochromatic light on response time, velocity or lag of accommodation. Conclusion The small change of spherical aberration did not affect accommodation response neither did change in chromatic aberration.

Objective vs subjective measures of fixation disparity for short and long fixation periods

Fixation disparity, i.e. the vergence error for stationary fusion stimuli, can be measured objectively with eye trackers and subjectively with nonius lines. Between these two measures, previous studies found differences that tended to be proportional to the amount of forced vergence, i.e. the discrepancy between vergence and accommodative stimulus. We investigate whether objective and subjective fixation disparity might be similar without forced vergence. We simultaneously measured fixation disparity with the EyeLink II system and with flashed dichoptic nonius lines in 17 subjects who observed targets at a vergence stimulus of 6 deg in an haploscope with 60 cm viewing distance. We found individual differences in objective fixation disparity in a range of about 20 (eso) to -60 (exo) min arc which was considerably larger than the range of subjective fixation disparity. Results were similar for long fixation periods (about 15 s) and short fixation periods (about 1.5 s) between 5 deg saccadic gaze shifts. Further, objective fixation disparity was correlated with objective heterophoria, i.e. the vergence state without a fusion stimulus (r = 0.8, p < 0.001). Subjective fixation disparity explained only about 25% of the inter-individual variability in objective fixation disparity. The discrepancy between these two measures might be explained by sensory shifts in retinal correspondence, also in the present condition without forced vergence.

Anterior chamber depth measurements in eyes with an accommodating intraocular lens: Agreement between partial coherence interferometry and optical coherence tomography

To determine agreement between partial coherence interferometry (PCI) and anterior segment optical coherence tomography (AS-OCT) measurements of anterior chamber depth (ACD) and axial intraocular lens (IOL) movement in eyes with an accommodating IOL. Department of Ophthalmology, St. Thomas' Hospital, London, United Kingdom. In this prospective pilot study of cataract patients, the central ACD was measured by PCI (ACMaster) and AS-OCT (Visante) 6 months after unilateral OPAL-A accommodating IOL implantation. Measurements were performed with a distance target and 1.00 diopter (D) and 2.00 D accommodative targets and after administration of topical pilocarpine 4%. Agreement between PCI and AS-OCT ACD measurements and IOL movement was calculated. Measurements were obtained in 18 patients. There was a consistent and statistically significant bias toward shallower ACD measurements with AS-OCT than with PCI, with the bias most pronounced after pilocarpine (mean 4.117 mm +/- 0.291 [SD] versus 4.054 +/- 0.287 mm; bias 0.063 mm; P<.0001). Limited IOL movement to 1.00 D and 2.00 D accommodative stimuli was detected with both instruments. After pilocarpine, forward IOL movement measurements were statistically significantly greater by AS-OCT than by PCI (mean 0.306 +/- 0.161 mm versus 0.270 +/- 0.155 mm) (P = .017). The AS-OCT device showed a bias toward underestimation of ACD compared with the PCI device. The bias increased as ACD shallowed with pilocarpine, resulting in overestimation of forward IOL movement by AS-OCT. This may lead to overestimation of the accommodative performance of IOLs. The ACD measurements obtained by the 2 devices are not interchangeable.

Pilot study of new focus-shift accommodating intraocular lens

To determine the visual and accommodative performance of the OPAL-A focus-shift accommodating intraocular lens (IOL). Department of Ophthalmology, St. Thomas' Hospital, London, United Kingdom. In this study comprising unilateral phacoemulsification and accommodating IOL implantation, patients were followed for 6 months. Corrected distance (CDVA) and distance-corrected near (DCNVA) visual acuities were measured. Objective amplitude of accommodation was measured with an autorefractor and subjective amplitude of accommodation, using push-up tests and defocus curves. Physiological and pilocarpine-stimulated IOL movement was measured by anterior segment optical coherence tomography. The mean values at 1 month, 3 months, and 6 months, respectively, were as follows: CDVA, -0.06 +/- 0.08 (SD), -0.08 +/- 0.09, and -0.05 +/- 0.09; DCNVA, 0.31 +/- 0.15, 0.31 +/- 0.15, and 0.34 +/- 0.16; objective amplitude of accommodation, 0.36 +/- 0.38 diopters (D), 0.12 +/- 0.34 D, and 0.10 +/- 0.34 D; subjective amplitude of accommodation, 2.79 +/- 0.86 D, 2.55 +/- 0.85 D, and 2.50 +/- 0.62 D with push-up test and 0.90 +/- 0.40 D, 0.78 +/- 0.23 D, and 0.93 +/- 0.35 D with defocus curves. The maximum physiologic IOL shift at 1 month (mean 45.2 +/- 63.4 microm) occurred with a 3.0 D accommodative stimulus. At 6 months, the mean pilocarpine-stimulated forward IOL shift was 306 +/- 161 microm. Objective accommodation and forward axial shift were clinically insignificant with the accommodating IOL. The near visual performance was attributed to depth of focus rather than to true pseudophakic accommodation.

Dynamics of ocular aberrations in keratoconus

Background: The aim was to investigate the fluctuations in monochromatic ocular aberrations with accommodation and tear‐film changes in moderate keratoconic eyes.Methods: We measured the changes in ocular higher‐order aberrations in 10 moderate keratoconic and 10 visually normal eyes to accommodative stimuli ranging from zero to 5.00 DS using a Hartmann‐Shack aberrometer. In addition, the changes in ocular higher‐order aberrations were measured for up to 15 seconds after a blink in eight keratoconic and eight visually normal eyes.Results: These results show that ocular spherical (p = 0.68) and coma‐like (p = 0.71) aberrations did not change significantly with accommodation from zero to 5.00 DS in keratoconic eyes. In contrast to normal eyes, the ocular higher‐order RMS error tended to decrease in magnitude after a blink in keratoconic eyes. Vertical coma became less negative with time after a blink in the keratoconic group, therefore, reducing the manifest ocular higher order RMS error by counteracting the negative vertical coma of the cornea.Conclusions: Compared to the manifest monochromatic higher‐order aberrations, any dynamic fluctuations in ocular aberrations with accommodation and tear film changes are relatively small in moderate keratoconic eyes. This implies that the correction of monochromatic higher‐order aberrations in keratoconus using customised soft contact lenses will not be significantly hindered by such dynamic aberrational changes.

Objective depth-of-focus is different from subjective depth-of-focus and correlated with accommodative microfluctuations

In this study, we investigated whether the objective depth-of-focus (DOF) is different from the subjective DOF and whether it correlates to accommodative microfluctuations (AMF). The objective DOF and subjective DOF at 1.5 D accommodative stimulus (AS) level were compared in the same group of subjects. The objective DOF and magnitude of AMF were measured at 5 AS levels from 0 D to 4 D. Results showed that there was a significant difference and no correlation between the objective DOF and the subjective DOF. The objective DOF was correlated to the magnitude of AMF. The results suggest that objective DOF and subjective DOF represent the blur sensitivity of two different systems. AMF are correlated with the blur sensitivity of the accommodative system.

Saccadic lens instability increases with accommodative stimulus in presbyopes.

An SRI dual Purkinje image (dPi) eye tracker was used to measure lens wobble following saccades with increasing accommodative effort as an indirect measure of ciliary muscle function in presbyopes. Ten presbyopic subjects executed 32 four-degree saccades at 1-s intervals between targets arranged in a cross on illuminated cards at each of 9 viewing distances ranging from 0.5- to 8-D accommodative demands. Post-saccadic lens wobble artifacts were extracted by subtraction of P1 (H(1)/V(1)) position signals from P4 signals (Theta(H)/Theta(V)), both of which were sampled by the eye tracker at 100 Hz. A ray tracing eye model was also employed to model the fourth Purkinje image shifts for a range of lens translations and tilts. Combining all saccades from all subjects showed a significant positive relationship between lens wobble artifact amplitude and accommodative demand. Eye model simulations indicated that artifacts of the amplitude measured could arise from either lens tilts (in the range of 2-4 degrees) or lens translations (in the range of 0.1 to 0.2 mm). Saccadic lens wobble artifacts increase with accommodative effort in presbyopes, indicating preserved ciliary muscle function and greater relaxation of zonular tension with accommodative effort. Variation across subjects may reflect differences in accommodative effort, ciliary muscle function for a given effort, and/or in intraocular anatomy.

Influences of accommodation and myopia on the foveal Stiles–Crawford effect

We determined the foveal Stiles–Crawford effect (SCE) as a function of up to 8D accommodation stimulus in six young emmetropes and six young myopes using a psychophysical two-channel Maxwellian system in which the threshold luminance increment of a 1 mm spot entering through variable positions in the pupil was determined against a background formed by a 4 mm spot entering the pupil centrally. The SCE became steeper in both groups with increasing accommodation stimulus, but with no systematic shift of the peak. Combining the data of both groups gave significant increases in directionality of 15–20% in horizontal and vertical pupil meridians with 6D of accommodation. However, additional experiments indicated that much of this was an artefact of higher order aberrations and accommodative lag. Thus, there appears to be little changes in orientation or directionality in the SCE with accommodation stimulus levels up to 6 D, but it is possible that changes may occur at very high accommodation levels.

Does the dynamic cross cylinder test measure the accommodative response accurately?

Background The dynamic cross cylinder (DCC) test is a standard clinical procedure used to assess the accommodative response (AR) subjectively. However, because of potential problems arising from the ambiguous stimulus conditions, it is unclear whether this test provides an accurate measure of the AR. The aim of this study was to compare clinical subjective findings with objective measurements of the AR. Methods Subjective findings to a 2.50-diopter (D) accommodative stimulus obtained with the DCC test (without fogging lenses) were compared with objective measurements of the AR obtained with a Grand Seiko WAM 5500 optometer (RyuSyo Industrial Co. Ltd., Kagawa, Japan) in 25 young subjects. As spherical lenses were introduced to quantify the subjective finding, objective measures of the AR were also recorded through these lenses. Results The mean AR recorded subjectively and objectively was 2.35 and 1.68 D, respectively ( P < 0.0001). Of the 10 subjects who demonstrated a lead of accommodation subjectively, only 1 had a lead objectively. For the 8 subjects who showed a lag of accommodation subjectively, all had a lag objectively. Introducing lenses produced a significant change in the mean AR. Conclusion The subjective DCC test as performed here does not provide an accurate measurement of the AR to a near target in a young population. We recommend that alternative techniques such as using an objective, open-field optometer or Cross-Nott retinoscopy be adopted for determining the within-task AR.

Wavefront aberrations variations with accommodation

Abstract Purpose To study the effects of phenylephrine 5% topical administration on accommodative response and wavefront aberrations variation. Methods The research followed the tenets of the Declaration of Helsinki . 28 eyes from 14 volunteers with spherical equivalent defocus error between –2D and +1D, no eye disease history and between 20 to 25 years of age, underwent wavefront measurements with a Shack–Hartmann wavefront aberrometer which included a movable accommodative target. Wavefront data was acquired while applying 6 different increasing accommodative stimuli, from 0 D to 5 D by steps of 1 D, before and after pupil dilation with Phenylephrine 5%. Results The dilation using Phenylephrine 5% was found to larger lag errors in the accommodative response of about half of the subjects. The total RMS amount of aberrations above defocus remained stable during accommodation with and without dilation. Spherical aberration was positive in average in the non accommodated eye and changed toward negative values with increasing accommodation (p&lt;0.05). Cylinder axis came closer to 90° as accommodation increased (p&lt;0.05). Although vertical coma did not significantly vary with accommodation, horizontal coma increased significantly with accommodation (p&lt;0.05). These changes in aberrations with increasing accommodation were similar on average in both pupil conditions Conclusion Phenylephrine 5% modifies the accommodative focus response of a significant proportion of young adult eyes. Wavefront aberrations above defocus undergo similar variations in both natural and dilated pupil conditions. However the total RMS error of aberrations above defocus remains relatively constant when the eye accommodates.

New Methods for the Assessment of Accommodative Convergence

The authors introduced a new objective method for measuring horizontal eye movements based on the first Purkinje image with the use of infrared charge-coupled device (CCD) cameras and compared stimulus accommodative convergence to accommodation (AC/A) ratios as determined by a standard gradient method. The study included 20 patients, 5 to 9 years old, who had intermittent exotropia (10 eyes) and accommodative esotropia (10 eyes). Measurement of horizontal eye movements in millimeters (mm), based on the first Purkinje image, was obtained with a TriIRIS C9000 instrument (Hamamatsu Photonics K.K., Hamamatsu, Japan). The stimulus AC/A ratio was determined with the far gradient method. The average values of horizontal eye movements (mm) and eye deviation (Delta) (a) before and (b) after an accommodative stimulus of 3.00 diopters (D) were calculated with the following formula: horizontal eye movements (mm/D) and stimulus AC/A ratio (Delta/D) = (b - a)/3. The average values of the horizontal eye movements and the stimulus AC/A ratio were 0.5 mm/D and 3.8 Delta/D, respectively. Correlation analysis showed a strong positive correlation between these two parameters (r = 0.92). Moreover, horizontal eye movements are directly proportional to the AC/A ratio measured with the gradient method. The methods used in this study allow objective recordings of accommodative convergence to be obtained in many clinical situations.

Examination of accommodation in pseudophakic eyes

Some patient with monofocal intraocular lens can achieve good near visual acuity with distance correction after cataract surgery. Understanding and measuring this phenomenon also called pseudoaccommodation can help to develop new technology to substitute or restore accommodation in pseudophakic eyes. I. To measure accommodation after cataract surgery. II. To measure anterior chamber depth with Scheimpflug imaging and comparing results with standard, ultrasonic data. III. To compare anterior chamber depth data, repeatability, reproducibility and reliability with a new optical device, the anterior segment optical coherent tomography (Visante OCT) and immersion ultrasound method in phakic eyes. I. We observed accommodation with defocusing technique, partial coherent interferometry method and measuring anterior chamber depth changing during ciliary muscle blocking. II. We measured anterior chamber depth with Pentacam and data were compared to standard ultrasonic method in phakic and pseudophakic eyes. III. We analyzed anterior chamber depth data, repeatability, reproducibility and reliability obtained by two observers using Visante OCT. I. A total accommodation amplitude of 0,83 D was observed with defocusing technique. Intraocular lens movement were negligible measured by partial coherent interferometry method using physiological accommodation stimulus. Mean movement of intraocular lens was 0.18 mm during blocking of the ciliary muscle. II. Pentacam and ultrasonic device measure the same anterior chamber depth in phakic eyes, but in pseudophakic eyes optical method measures significantly shallower anterior chamber depth. III. Anterior segment optical coherent tomography measures deeper anterior chamber depth than immersion ultrasonic device in phakic eyes. Accomodation and pseudoaccommodation observed in pseudophakic eyes is hard to measure and only parts of this process can be measured with each technique. Anterior chamber depth data varies by the measuring technique. Repeatability, reproducibility and reliability of anterior chamber depth data were better with optical technique.

Visual field does not affect steady-state accommodative response and near-work induced transient myopia

To investigate whether or not peripheral retinal defocus contributes to the refractive development of myopia by influencing the overall accommodative function. The steady-state accommodative stimulus response curve (ASRC) and the near-work induced transient myopia (NITM) after a near visual task were compared between different visual field conditions in emmetropes (EMMs), stable myopes (SMs) and progressing myopes (PMs). Results showed that visual field had no effect on the ASRC and NITM but PMs exhibited greater NITM than EMMs and SMs. The results of this study suggest that peripheral defocus does not influence the overall accommodative system so its probable contribution to myopia development is not via the accommodative system.