A Simplifed Model Eye for Testing Fundus Imaging Device / 中国医疗器械杂志

Based on the Gullstrand I model eye, a simplified model eye for testing fundus imaging device is designed. The model eye can reach the following requirements:(1) The refractive characteristics of the ocular refractive tissue are simulated, and the equivalent focal length in air is 17 mm; (2) The differences between relative refractive index differences of the adjacent materials of the simplified model eye and relative refractive index differences of any adjacent two layers (cornea and aqueous humor, aqueous humor and lens, lens and vitreous body) of the Gullstrand I model eye are not more than 1%; (3) In the case of the incident aperture diameter of 3 mm, the differences of radii of the diffuse spots formed by the paraxial light and the axial light are not more than 15%; (4) The differences of angles of chief ray and tangent line of the fundus are not more than 1°; (5) In the case of the incident aperture diameter of 3 mm, the differences of MTF values of the near axis light are not more than 0.1. The simplified model eye can be expected to be used for testing fundus imaging device instead of the test method in ISO 10940:2009 Ophthalmic instruments-Fundus cameras.

Study on the Imaging Quality Evaluation of Aspheric Intraocular Lenses / 中国医疗器械杂志

The article is to study the objective evaluation method of the imaging quality of aspheric intraocular lens with different design concepts by establishing the model eye which is close to the actual corneal spherical aberration characteristics. Combined with the research data of corneal spherical aberration, the simulated cornea corresponding to Zernike c(4,0) coefficient 0.00 μm, 0.10 μm, 0.20 μm and 0.28 μm was established respectively. The optical quality of the measured simulated corneal lenses basically reached the theoretical design effect, and the deviation between the MTF value and the theoretical design value was equivalent to the MTF test repeatability. The establishment of model eye for artificial lens provides a research tool for the evaluation of aspheric intraocular lens imaging quality.

Optical imaging quality change of multifocal intraocular lens following Nd∶YAG laser damage / 中华实验眼科杂志

Objective To study the optical imaging quality of multifocal intraocular lens (IOL) following Nd∶YAG laser damage.Methods Three hydrophobic acrylate discs used to make multifocal IOL were placed in line,and the Nd∶YAG laser was used to emit the posterior surface,mid-plane and anterior surface of the discs by gradually increasing the emitting energy to determine the damaged threshold energy of various planes.Eight multifocal IOLs were divided into 2 groups.IOL damage models were established by emitting 12 points along 12 clocks on circle of 3.0 mm in diameter in the group 1 (IOLs NO.1,2,3,4) and 6 points with 1-clock interval on circle of 1.0 mm in diameter in the group 2 (IOLs NO.5,6,7,8) with Nd∶YAG laser.The modulation transfer function (MTF),line spread function (LSF) and United States air force (USAF) test target images of the IOLs were tested under the optical aperture at 2.0,3.0 and 4.5 mm.Results The damage thresholds of laser power were not significantly different among three hydrophobic acrylate discs (Fgroup =1.100,P =0.337),and the thresholds were significantly different among different planes in the discs (Fposition =195.279,P=0.000),with the highest damage threshold in the anterior surface and the lowest damage threshold in the mid-plane of the discs(all at P＜0.01).The shifts of far focus and near focus MTF curves,LSF curves and USAF target images of the IOLs under the 2.0,3.0 and 4.5 mm optical aperture after laser damage were in coincidence with those before laser damage both in group 1 and group 2.The glare phenomenon of the USAF target image was observed at near focus under the 4.5 mm optical aperture both before and after laser damage.Conclusions Multifocal IOL is vulnerable to injury when the laser beam focuses on the midplane,and the anterior surface of IOL can tolerate certain degree of damage.In standard model eye,the MTF curves,LSF curves and USAF target images of multifocal IOL was not impacted by laser induced spots injuries under different pupil diameters.

Optical performance of Toric intraocular lens rotation in Hwey-Lan Liou model eye / 中华实验眼科杂志

Background The residual astigmatism following Toric intraocular lens (IOL) rotation have received much attention.However,the variation of the optical performance and the wavefront abrrveation with Toric IOL rotation are unclear.Objective The aim of this study was to evaluate the optical performance,wavefront abrrveation and residual diopter spherical and cylinder lens with Toric IOL rotation.Methods T3,T4 and T5 Toric IOLs of +22.0 D were placed in Hwey-Lan Liou model eye respectively,with the posterior surface flat on the X axis and steep on the Y axis.Corneal astigmatism model was established by mimicing the model eye with Toric IOL using Zemax optical software.Then the Toric IOLs were rotated 5° to 10° individually under the 4 mm pupil diameter and 550 nm monochromatic light,and the image performance and wavefront abrrveation were recorded with all conditions,including modulation transfer function (MTF),out-of-focus aberration,astigmatism aberration,coma,trefoil aberration and spherical aberration.The refractive error of spherical power and cylinder power were calculated.Results Corneal astigmatism was fully corrected when Toric IOLs in the middle,and the MTF curves were near in T3,T4,T5 Toric IOLs.The image performance was worse under the high spatial frequency with the increase of rotation degrees of Toric IOLs,showing the gradually low of MTF curves,especially T5 Toric IOL.No obvious changes was seen in coma,trefoil aberration and spherical aberration after rotation of Toric IOLs,while out-of-focus aberration,astigmatism aberration were obviously increased.In addition,residual astigmatism and spherical error increase with the rotation of Toric IOLs.Conclusions Toricl IOL rotation leads to increase of astigmatism and spherical refractive error but not high order aberration.