• Journal of Korean Clinical Health Science
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• v.8 no.1
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• pp.1362-1368
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• 2020

Purpose. In this study, The change of the accommodation function due to the use of a smartphone was objectively evaluated using an Auto Refractokeratometer and was to investigate the effect of accommodation response and microfluctuations of accommodation on stable fatigue. Methods. Twenty subjects (20 males, 20 females) who had no abnormalities in ophthalmic disease and strabismus, diplopia, suppression, convergence and ocular movement, and corrected visual acuity and unaided visual acuity of 0.8 or more were performed. The average age of the participants is (21.78 ± 1.78) years old. The refractive power of the eye was measured using an Auto Refractokeratometer (Speedy-i K-model, Righton Mfg Co. Tokyo Japan), and the equivalent spherical power was automatically calculated from the measured refractive power. The accommodation response amount was calculated for the accommodation stimulation amount in 8 steps in 0.5D increments from + 0.50D to -3.00D in the calculated equivalent spherical power. The microfluctuations of accommodation in the high frequency region was calculated according to the change in the amount of the accommodation stimulus. At this time, the spectral power of the microfluctuations of accommodation was analyzed by Fast Fourier Transformation (FFT). Results. After using the smartphone, it was found that the accommodation response to accommodation stimulation decreased and the microfluctuations of accommodation increased. Conclusions. It can be said that the use of a smartphone affects the accommodation response and the microfluctuations of accommodation, thereby causing a accommodative stable fatigue. Therefore, it is thought that the use of a smartphone for a long time may bring about a change in the accommodation function.

• Korean Journal of Optics and Photonics
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• v.18 no.5
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• pp.337-344
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• 2007

In recent years, there has been rapid progress in different areas of vision science, such as refractive surgical procedures, contact lenses and spectacles, and near vision. This progress requires a highly accurate modeling of optical performance of the human eyes in different accommodation states. A new novel model-eye was designed using the Navarro accommodation-dependent finite model eye. For each of the vergence distances, ocular wavefront error, accommodative response, and visual acuity were calculated. Using the new model eye ocular wavefront error, accommodation dative response, and visual acuity are calculated for six vergence stimuli, -0.17D, 1D, 2D, 3D, 4D and -5D. Also, $3^{rd}\;and\;4^{th}$ order aberrations, modulation transfer function, and visual acuity of the accommodation-dependent model eye were analyzed. These results are well-matched to anatomical, biometric, and optical realities. Our corrected accommodation-dependent model-eye may provide a more accurate way to evaluate optical transfer functions and optical performances of the human eye.

• Journal of Korean Ophthalmic Optics Society
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• v.9 no.2
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• pp.203-209
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• 2004

Physiological accommodation in aphakia has been reported 0.50D. Also, accommodation appears in pseudo-crystalline lens. However accommodation was not clear how to works in the eyes. Therefore, the purpose of this study is that accommodation has been affected to changes of axial length and corneal refractive power when the accommodative stimulus was taken 10 diopters to person who has pseudo-crystalline lens. To determine of the accommodative response of pseudo-phakic patients who had no side effects over 2 months, we have measured the axial length, corneal refractive power in 48 patients(96 eyes). When the accommodative stimulus was taken about 10 diopters, the axial length increased by $0.05{\pm}0.06mm$ and corneal refractive power increased $0.04{\pm}0.24$ diopter. The changes of axial length in the myopia was increased by $0.19{\pm}0.18D$, emmetropia was increased by $0.12{\pm}0.16D$ and hyperopia was $0.10{\pm}0.19D$. The results of measurement revealed that the mean value was increased $0.03{\pm}0.13D$ in the myopia, and increased $0.21{\pm}0.13D$ in the emmetropia, and decreased $0.02{\pm}0.34D$ in the hyperopia.

• Journal of Korean Ophthalmic Optics Society
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• v.20 no.3
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• pp.341-347
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• 2015

Purpose : This study was to examine a correlation of response AC/A ratio by additional spherical powers with PD(Pupilary distance) and relative accommodation, and was to investigate correlation of CA/C ratio by prism powers. The mean differences between a reciprocal response AC/A ratio and a CA/C ratio were compared, and were suggested to be used as data in the refractive power and prism prescriptions in the clinical. Methods: The open field autorefractometer (Nvision-K 5001, Shin nippon) and Howell target at 40 cm fixation distance to 62 persons with average $22.62{\pm}2.84$ ages were used to measure the response AC/A ratio according to additional Spherical powers. The CA/C ratios were measured using the DOG card at 40cm according to prism powers. Results: When the response accommodation according to Additional Spherical power changes and the response accommodation according to prism power changes were compared, it was larger than the response accommodation according prism power change. These were significant differences statistically. The correlation of response AC/A ratio and PD is showed as r = -0.158, the CA / C ratio is shown as r = 0.093. The correlation of response AC/A ratio and relative accommodation showed as r = -0.253, the CA/C ratio showed as r = 0.566 that is predictable correlation. The correlation of response AC/A ratio and CA/C ratio showed as r = -0.355 that is low minus correlation (p = 0.000). The difference between a reciprocal response AC/A ratio and a CA/C ratio showed $0.12{\pm}0.06D/{\Delta}$ with a significant difference statistically (p=0.000). Conclusions: The correlation of relative accommodation and CA/C ratio showed that depend on the individual, The more a relative accommodation is, the higher a response accommodation of convergence by convergence stimulus is. The reciprocal response AC/A and CA/C ratio showed significant differences statistically. This can have higher CA/C ratio in patients with low AC/A ratio in clinical as an independent variable. Thus when the abnormal binocular vision was prescribed in the clinical, it is necessary to consider the accommodative response even if the AC/A ratio is a normal range.

• Journal of Korean Ophthalmic Optics Society
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• v.9 no.2
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• pp.223-231
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• 2004

In most previous studies, the assessment of accommodative convergence to accommodative stimulus (AC/A) ratio was commonly made by measuring gradient AC/A ratio. This study deals with the proximal convergence/accommodation(PC/A)ratio measured by comparing values of the gradient AC/A ratio and the calculated AC/A ratio to prevail the clinical use of the AC/A ratio. Visual acuities of All 124 subjects had been corrected to at least 1.0 with either eye through their habitual refractive correction and the MEM dynamic retinoscopy was performed to estimate their accommodative response. And then the PC/A ratio was calculated by making use of the calculated AC/A ratio and the gradient AC/A ratio. This study showed that the difference between the mean calculated AC/A ratio and the mean gradient AC/A ratio in subgroups may be attributable to proximal convergence. Consequently, further studies on proximity cues including the PC/A ratio could be helpful to prevail the clinical use of the AC/A ratio.

• Journal of Korean Ophthalmic Optics Society
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• v.15 no.3
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• pp.235-240
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• 2010

Purpose: In this study, we proposed a simple accommodation-dependent crystalline lens with a constant volume and homogeneous refractive index. Methods: We proposed a human crystalline lens with two aspheric surfaces. Two surfaces intersect in two points and straight line between two points was equator(2b). It assumed that the derivative in axial direction was zero at the equator and the radial derivative was zero at the vertex. Proposed human crystalline lens was divided by the equator into the anterior and posterior parts. It was assume that the volume of each part and refractive index of the human crystalline lens were constant during accommodation. Results: For the changes during accommodation, geometrical parameters were determined by different objective distances. Considering the constant volume of each part with the small decrement of the equator, we obtained the paraxial parameters, such as the anterior and posterior vertex radius of curvature and lens thickness. Compared with the experimental data published in the literature, calculated values using simple approximation showed similar change per accommodative stimulus. Conclusions: These results showed that proposed simple approximation using assumption of constant volume and refractive index of the human crystalline lens made it possible to predict changes of geometrical parameters during accommodation.