Design of Large-aperture and Wide-band Optical Lens

The design of a large-aperture and wide-band optical lens for camera is presented. By utilizing the atmospheric window of infrared light, clear images can be achieved in the dark or poor visibility conditions. To use near-infrared and visible light to obtain images, the charge coupled device(CCD) is adopted as the image sensor of the lens with the center wavelength of 880 nm, which operates at the wavelength range from 400 nm to 1 000 nm. After calculating the parameters of optical lens, Sunnah type is selected as the initial structure. Through the optimization of optical design software ZEMAX, the lens obtains an excellent imaging performance. The modulation transfer function(MTF) can be more than 0.3 at the spatial frequency of 110 lp/mm, and the maximum distortion can be less than 0.1%.

Evaluation of visual quality of spherical and aspherical intraocular lenses by Optical Quality Analysis System

AIM： To evaluate the impact of spherical and aspherical intraocular lenses on the postoperative visual quality of age-related cataract patients using Optical Quality Analysis System （OQAS）. METHODS： Seventy-four eyes with age-related cataracts were randomly divided into spherical and aspherical lens implantation groups. Best-corrected visual acuity （BCVA） was measured preoperatively, one day, one week, two weeks, one month and two months after surgery. A biometric systems analysis using the OQAS objective scattering index （OSI） was performed. RESULTS： There were no significant differences in visual acuity （P〉0.05） before and after spherical and aspheric lens implantation. There was a negative linear correction between the OSI value and BCVA （t-=-0.634, P=-0.000）, and positive corrections between the OSI value and the lens LOCUS III value of nucleus color （NC）, nucleus opacity （NO）, cortex （C） and posterior lens capsular （P） （r=0.704, P=0.000; r=0.514, P=0.000; r=0.276, P=0.020; r=0.417, P=-0.000, respectively）. OSI values of spherical vs aspherical lenses were 11.5±3.6 vs 11.8±3.4, 4.1±0.9 vs 3.3±0.8, 3.5±0.9 vs 2.7±0.7, 3.3±0.8 vs 2.6±0.7, 3.2±0.7 vs 2.5±0.8, and 3.2±0.8 vs 2.50.8 before and ld, 1, 2wk, 1 and 2mo after surgery, respectively. All time points varied significantly （P〈0.01） between the two groups. CONCLUSION： Aspherical IOLs does not significantly affect visual acuity compared with spherical IOLs. The OSI value, was significantly lower in the aspherical lens group compared with the spherical lens. This study shows that objective visual quality of aspheric IOLs is better than that of the spherical lens by means of OQAS biological measurement method.

Repeatability of in-vitro optical quality measurements of intraocular lenses with a deflectometry technique effect of the toricity

AIM： To evaluate the repeatability of an optical device for measuring the Zernike coefficients of toric intraocular lenses（IOLs） and assess whether its toricity has any impact in its repeatability. METHODS： An experienced technician used the NIMO TR1504 to measure the Zernike coefficients 30 times for an aperture of 4.50 mm for all lenses included. The IOLs included were divided into two group： toric and nontoric ones. The cylindrical powers of the toric lenses included in the present study were 1.00, 1.50, 2.25, 3.00 and 3.75 D. Finally, the repeatability of the NIMO TR1504 was described in terms of within subject standard deviation（Sw） and repeatability limit. RESULTS： The Sw was smaller than 0.011 μm for both lens groups and all Zernike coefficients, and the difference between both groups was smaller than 0.004 μm for all Zernike coefficients. Regarding the repeatability limit, this value was smaller than 0.025 μm for the toric lens group, and smaller than 0.031 μm for the non-toric lens one for all Zernike coefficients. Furthermore, the maximum difference between both lens groups was 0.010 μm. CONCLUSION： The repeatability of the NIMO TR1504 to measure the optical quality is high and independent of the lens toricity. These results reflect that this system is robust and could be used to measure the in-vitro optical quality of either toric or non-toric IOLs.

The mechanism study of low-pressure air plasma cleaning on large-aperture optical surface unraveled by experiment and reactive molecular dynamics simulation

Low-pressure air plasma cleaning is an effective method for removing organic contaminants on large-aperture optical components in situ in the inertial confinement fusion facility.Chemical reactions play a significant role in plasma cleaning,which is a complex process involving abundant bond cleavage and species generation.In this work,experiments and reactive molecular dynamics simulations were carried out to unravel the reaction mechanism between the benchmark organic contaminants of dibutyl phthalate and air plasma.The optical emission spectroscopy was used to study the overall evolution behaviors of excited molecular species and radical signals from air plasma as a reference to simulations.Detailed reaction pathways were revealed and characterized,and specific intermediate radicals and products were analyzed during experiments and simulation.The reactive species in the air plasma,such as O,HO_(2)and O_(3)radicals,played a crucial role in cleaving organic molecular structures.Together,our findings provide an atomic-level understanding of complex reaction processes of low-pressure air plasma cleaning mechanisms and are essential for its application in industrial plasma cleaning.

Optical Modeling and Analysis of Peripheral Optics of Contact Lenses

Background: Degraded peripheral vision has been hypothesized to be a stimulus for the development of foveal refractive error. Contact lenses have been widely used to correct central vision, but their impacts on peripheral vision are still unknown. The purpose of this study was to use optical model software to evaluate the peripheral optics of rigid gas permeable (RGP) and soft contact lenses (SCLs) in isolation. This will better assist us in understanding their peripheral optical performances on human eyes. Methods: An optical design software package (Zemax EE) was used to model peripheral optics of Menicon RGP lens and Acuvue 2 SCLs. Profiles of sphero-cylindrical power and major higher-order aberrations were computed in 10osteps out to 40o off-axis eccentricity for –3.0 D central focal power contact lens. The results of optical modeling were analyzed and compared with previously published experimental data. Results: –3.0 D RGP lenses and SCLs had –1.4 D and –2.0 D dioptric power at 40o eccentricity, respectively. The reduced dioptric power in the periphery of the analyzed contact lenses quantitatively matched with the reduced amount of hyperopic field curvature found from experimental data when these contact lenses fitted on human eyes. Cylindrical power increased to 0.3 D ~ 0.4 D at 40o eccentricity for both lens types. In addition, both contact lens types produced higher order aberrations, namely 1.2 μm coma and 0.15 μm spherical aberration at 40o eccentricity. Conclusions: Compared to SCLs, RGP lenses with equal focal power had less dioptric power in the periphery. Both RGP lenses and SCLs produced the same amount of major higher-order aberrations with increasing of the field angle. Some of these results can be used to predict and understand the peripheral optical performance of contact lenses on human eyes.

Optical biometry intraocular lens power calculation using different formulas in patients with different axial lengths

AIM: To investigate the predictability of intraocular lens (IOL) power calculation using the IOLMaster and different IOL power calculation formulas in eyes with various axial length (AL). METHODS: Patients were included who underwent uneventful phacoemulsification with IOL implantation in the Department of Ophthalmology, Far Eastern Memorial Hospital, Taipei, Taiwan, China from February 2007 to January 2009. Preoperative AL and keratometric values (Ks) were measured by IOLMaster optical biometry. Patients were divided into 3 groups based on AL less than 22mm (Group 1), 22-26mm (Group 2), and more than 26mm (Group 3). The power of the implanted IOL was used to calculate the predicted postoperative spherical equivalence (SE) by various formulas: the Haigis, Hoffer Q, Holladay 1, and SRK/T. The predictive accuracy of each formula was analyzed by comparing the difference between the actual and predicted postoperative SE (MedAE, median absolute error). All the patients had follow-up periods exceeding 3 months. RESULTS: Totally, there were 200 eyes (33 eyes in Group 1, 92 eyes in Group 2, 75 eyes in Group 3). In all patients, the Haigis had the significantly lower MedAE generated by the other formulas (P【0.05). In Group 1 to 3, the MedAE calculated by the Haigis was either significantly lower or comparable to those calculated by the other formulas.CONCLUSION: Compared with other formulas using IOLMaster biometric data, the Haigis formula yields superior refractive results in eyes with various AL.

Optical quality of toric intraocular lens implantation in cataract surgery

AIM: To analyze the optical quality after implantation of toric intraocular lens with optical quality analysis system.METHODS: Fifty-two eyes of forty-four patients with regular corneal astigmatism of at least 1.00 D underwent implantation of Acry Sof toric intraocular lens, including T3 group 19 eyes, T4 group 18 eyes, T5 group 10 eyes,T6 group 5 eyes. Main outcomes evaluated at 3mo of follow-up, included uncorrected distance visual acuity(UDVA), corrected distance visual acuity(CDVA), residual refractive cylinder and intraocular lens(IOL) axis rotation.Objective optical quality were measured using optical quality analysis system(OQAS Ⅱ, Visiometrics, Spain),included the cutoff frequency of modulation transfer function(MTFcutoff), objective scattering index(OSI),Strehl ratio, optical quality analysis system value(OV)100%, OV 20% and OV 9% [the optical quality analysis system(OQAS) values at contrasts of 100%, 20%, and 9%].RESULTS: At 3mo postoperative, the mean UDVA and CDVA was 0.18 ±0.11 and 0.07 ±0.08 log MAR; the mean residual refractive cylinder was 0.50 ±0.29 D; the mean toric IOL axis rotation was 3.62 ±1.76 degrees, the mean MTFcutoff, OSI, Strehl ratio, OV 100%, OV 20% and OV9% were 22.862 ±5.584, 1.80 ±0.84, 0.155 ±0.038, 0.76 ±0.18,0.77±0.19 and 0.78±0.21. The values of UDVA, CDVA, IOL axis rotation, MTFcutoff, OSI, Strehl ratio, OV100%,OV20% and OV9% depending on the power of the cylinder of the implantation were not significantly different(P 】0.05), except the residual refractive cylinder(P 【0.05).CONCLUSION: The optical quality analysis system was useful for characterizing the optical quality of Acry Sof toric IOL implantation. Implantation of an Acry Sof toric IOL is an effective and safe method to correct corneal astigmatism during cataract surgery.

Comparison of postoperative optical quality according to the degree of decentering of V4c implantable collamer lens

AIM：To evaluate the clinical outcomes of V4 c implantable collamer lens（Hole ICL） implantation with regard to the optical quality assessed according to different degrees of decentering.METHODS：This included 49 eyes that received conventional ICL and 94 eyes that received Hole ICL.The eyes that received Hole ICL were divided into three groups according to the degree of decentering：group 1,central hole within 1 hole diameter（HD） from the pupil center;group 2,central hole within 1 HD to 2 HD;and group 3,central hole within 2 HD to 3 HD.Visual acuity（VA）,intraocular pressure（IOP）,and spherical equivalent（SE） values were assessed at 1wk,1 and 3mo after surgery.The ocular modulation transfer function,Strehl ratio,objective scattering index,and higher order aberrations（HOAs） were measured for 4-mm pupils at 3mo after surgery.RESULTS：There were no significant differences in VA,IOP,and SE among the conventional and Hole ICL groups.With regard to HOAs,values for coma and spherical aberrations showed no differences.The total HOA and trefoil values were significantly higher in group 2 than in group 1（P=0.02,0.03,respectively）.There were no significant differences among groups with regard to other optical quality parameter at 3mo after surgery.CONCLUSION：Our results suggest that Hole ICL implantation provides satisfactory visual quality that is equivalent to that provided by conventional ICL,regardless of the presence of central hole and degree of decentering.

Double-distance propagation of Gaussian beams passing through a tilted cat-eye optical lens in a turbulent atmosphere

By using the extended Huygens-Fresnel diffraction integral and the method of expanding the aperture function into a finite sum of complex Caussian functions, an approximate analytical formula of the double-distance propagation for Caussian beam passing through a tilted cat-eye optical lens and going back along the entrance way in a turbulent atmosphere has been derived. Through numerical calculation, the effects of incidence angle, propagation distance, and structure constant on the propagation properties of a Gaussian beam in a turbulent atmosphere are studied. It is found that the incidence angle creates an unsymmetrical average intensity distribution pattern, while the propagation distance and the structure constant can each create a smooth and symmetrical average intensity distribution pattern. The average intensity peak gradually deviates from the centre, and the central average intensity value decreases quickly with the increase in incidence angle, while a larger structure constant can bring the average intensity peak back to the centre.

Comparison of optical quality after implantable collamer lens implantation and wavefront-guided laser in situ keratomileusis

AIM： To compare the optical quality after implantation of implantable collamer lens（ICL） and wavefront-guided laser in situ keratomileusis（WG-LASIK）.METHODS： The study included 40 eyes of 22 patients with myopia who accepted ICL implantation and 40 eyes of 20 patients with myopia who received WG-LASIK. Before surgery and three months after surgery, the objective scattering index（OSI）, the values of modulation transfer function（MTF） cutoff frequency, Strehl ratio, and the Optical Quality Analysis System（OQAS） values（OVs） were accessed. The higher order aberrations（HOAs） data including coma, trefoil, spherical, 2^（nd） astigmatism and tetrafoil were also obtained. For patients with pupil size 〈6 mm, HOAs data were analyzed for 4 mm-pupil diameter. For patients with pupil size ≥6 mm, HOAs data were calculated for 6 mm-pupil diameter. Visual acuity, refraction, pupil size and intraocular pressures were also recorded.RESULTS： In both ICL and WG-LASIK group, significant improvements in visual acuities were found postoperatively, with a significant reduction in spherical equivalent（P〈 0.001）. After the ICL implantation, the OSI decreasedslightly from 2.34±1.92 to 2.24±1.18 with no statistical significance（P=0.62）. While in WG-LASIK group, the OSI significantly increased from 0.68±0.43 preoperatively to 0.91±0.53 postoperatively（Wilcoxon signed ranks test, P=0.000）. None of the mean MTF cutoff frequency, Strehl ratio, OVs showed statistically significant changes in both ICL and WG-LASIK groups. In the ICL group, there were no statistical differences in the total HOAs for either 4 mmpupil or 6 mm-pupil. In the WG-LASIK group, the HOA parameters increased significantly at 4 mm-pupil. The total ocular HOAs, coma, spherical and 2^（nd） astigmatism were 0.12±0.06, 0.06±0.03, 0.00±0.03, 0.02±0.01, respectively. After the operation, these values were increased into 0.16±0.07, 0.08±0.05,-0.04±0.04, 0.03±0.01 respectively（Wilcoxon signed ranks test, all P〈0.05）. At 6 mm-pupil, the induction of total HOAs was not statistically significant in the WG-LASIK group. CONCLUSION： ICL implantation has a less disturbance to optical quality than WG-LASIK. The OQAS is a valuable complementary measurement to the wavefront aberrometers in evaluating the optical quality.

Comparison of choroidal thickness in high myopic eyes after FS-LASIK versus implantable collamer lens implantation with swept-source optical coherence tomography

AIM:To investigate the changes in choroidal thickness(CT)in high myopic eyes after femtosecond laser-assisted in situ keratomileusis(FS-LASIK)surgery or central hole implantable collamer lens(ICL V4c)implantation using swept-source optical coherence tomography(SS-OCT).METHODS:We examined the right eyes of 116 patients with high myopia who were candidates for FS-LASIK surgery and ICL implantation.Sixty eyes underwent ICL V4c implantation and 56 eyes were subjected to FS-LASIK surgery.The CT was measured with SS-OCT.All data were recorded preoperatively and 2 h,1 wk,1 and 3 mo postoperatively.Other demographic information was collected,including age,sex,uncorrected visual acuity(UCVA),best corrected visual acuity(BCVA),spherical equivalent(SE),intraocular pressure(IOP)and axial length(AL).RESULTS:The UCVA improved in both groups and showed no significant differences between groups.There also were no significant differences between the two groups in postoperative BCVA and SE(P=0.581 and 0.203,respectively).The foveal CTs,inner nasal and outer nasal CTs were significantly thicker at 2 h postoperatively in both groups(P<0.05)but returned to baseline levels in 1 wk;after 1 mo,no significant differences were found relative to the preoperative values.At 3 mo in each group,nine regions showed variations in the CT as compared with preoperative thickening,but only the foveal and nasal area CTs preoperative differences were statistically significant(P<0.05).In addition,there was no significant difference in 9 regions of CT between the two groups at all follow-up times(P>0.05).CONCLUSION:The CTs after ICL implantation and FSLASIK surgery are significantly thicker than those before operation,especially in the foveal and nasal areas,but there is no significant difference between the two methods.

Measuring Topological Charges of Optical Vortices with Multi-Singularity Using a Cylindrical Lens

We present a simple method to measure the topological charges of optical vortices with multiple singularities. Using a cylindrical lens, a vortex beam can decay into a light field distribution with multiple separated dark holes, whose number just equals the topological charge of the input beam. This conclusion is then verified via experiments and numerical simulations of the propagation of vortex beams with multiple singulaxities. This method is also reliable to measure the topological charges of broadband vortex beams with different distributions of singularities, which does not resort to multiple beam interferometrie experiments.

An all-silicone zoom lens in an optical imaging system

An all-silicone zoom lens is fabricated. A tunable metal ringer is fettered around the side edge of the lens. A nylon rope linking a motor is tied, encircling the notch in the metal ringer. While the motor is operating, the rope can shrink or release to change the focal length of the lens. A calculation method is developed to obtain the focal length and the zoom ratio. The testing is carried out in succession. The testing values are compared with the calculated ones, and they tally with each other well. Finally, the imaging performance of the all-silicone lens is demonstrated. The all-silicone lens has potential uses in cellphone cameras, notebook cameras, micro monitor lenses, etc.

Effect of size and indium-composition on linear and nonlinear optical absorption of InGaN/GaN lens-shaped quantum dot

Based on the Schr ¨odinger equation for envelope function in the effective mass approximation, linear and nonlinear optical absorption coefficients in a multi-subband lens quantum dot are investigated. The effects of quantum dot size on the interband and intraband transitions energy are also analyzed. The finite element method is used to calculate the eigenvalues and eigenfunctions. Strain and In-mole-fraction effects are also studied, and the results reveal that with the decrease of the In-mole fraction, the amplitudes of linear and nonlinear absorption coefficients increase. The present computed results show that the absorption coefficients of transitions between the first excited states are stronger than those of the ground states. In addition, it has been found that the quantum dot size affects the amplitudes and peak positions of linear and nonlinear absorption coefficients while the incident optical intensity strongly affects the nonlinear absorption coefficients.

Comparison of anterior section parameters using anterior segment optical coherence tomography and ultrasound biomicroscopy in myopic patients after ICL implantation

AIM：To compare the agreement of anterior chamber depth（ACD）and central vault measurements obtained by anterior segment optical coherence tomography（AS-OCT）and ultrasound biomicroscopy（UBM）of post surgical high myopic eyes with posterior chamber phakic intraocular lens（Visian ICL;STAAR Surgical）implantation.·METHODS：Fifty-two phakic eyes of 28 high myopic patients who underwent implantable Collamer lens（ICL）surgery for the correction of high myopia were studied.The postoperative ACD,the distance between the corneal endothelium and the anterior surface of ICL（cornea-ICL）and the central vault were measured with the AS-OCT system and the UBM system.Intraclass correlation coefficient（ICC）and the Bland-Altman plot were used to evaluate the repeatability and agreement of two devices.·R ESULTS：The mean ACD,cornea-ICL and central vault in the 52 phakic eyes after ICL surgery was 3.19±0.28 mm,2.47±0.28 mm,0.50±0.19 mm by AS-OCT and3.13±0.25 mm,2.49±0.25 mm,0.44±0.19 mm by UBM,respectively.Pairwise comparison of ACD and central vault measurements showed significant differences between AS-OCT and UBM（〈0.05）.However,no statistically significant difference was found between these imaging techniques in cornea-ICL（〉0.05）.The Pearson correlation coefficient（）between AS-OCT and UBM measurements for ACD,cornea-ICL and vault was0.88,0.80 and 0.89,respectively（〈0.001）.The ICC was0.89-0.94 for the measurements of AS-OCT and UBM.Bland-Altman analysis showed the 95%limits of agreement of ACD,cornea-ICL,central vault measurements between these two devices were-0.20 to 0.32 mm,-0.36to 0.32 mm and-0.12 to 0.24 mm,respectively.58·CONCLUSION：Central ACD and vault measurements using AS-OCT demonstrated a slight significantly higher value than using UBM in phakic eyes after ICL surgery.These two devices should not be used interchangeably for measurements of central ACD and vault in patients after phakic intraocular lens implantation.

A multi-photon(7×7)-focus 3D laser printer based on a 3D-printed diffractive optical element and a 3D-printed multi-lens array

One of the challenges in the field of multi-photon 3D laser printing lies in further increasing the print speed in terms of voxels/s.Here,we present a setup based on a 7×7 focus array(rather than 3×3 in our previous work)and using a focus velocity of about 1 m/s(rather than 0.5 m/s in our previous work)at the diffraction limit(40×/NA1.4 microscope objective lens).Combined,this advance leads to a ten times increased print speed of about 108 voxels/s.We demonstrate polymer printing of a chiral metamaterial containing more than 1.7×10^(12) voxels as well as millions of printed microparticles for potential pharmaceutical applications.The critical high-quality micro-optical components of the setup,namely a diffractive optical element generating the 7×7 beamlets and a 7×7 lens array,are manufactured by using a commercial two-photon grayscale 3D laser printer.

Analysis of macular microvasculature and thickness after ICL implantation in patients with myopia using optical coherence tomography

AIM:To investigate changes in macular vessels and thickness in myopic eyes after intraocular collamer lens(ICL)implantation using quantitative optical coherence tomography angiography(OCTA).METHODS:This retrospective included 73 myopic eyes of 73 patients(average age,27.53±6.16 y)who underwent ICL implantation(28 eyes were Toric ICL).Axial length(AL),uncorrected visual acuity(UCVA),refractive dioptre(RD),intraocular pressure(IOP)and OCTA were measured and compared with before and 1 wk,1,and 3 mo after surgery.OCTA was used to image vessel density(VD)and skeleton density(SD)in both the superficial(SCP)and deep capillary plexus(DCP).Central retinal thickness(CRT)and ganglion cellinner plexiform layer thickness(GCT)were also measured.Changes between pre-and postoperative measurements were analysed by repeated measures analysis of variance.RESULTS:Compared with preoperative data,postoperative data on UCVA revealed significant improvements in all patients(P<0.05).However,there was no significant difference in IOP.After the operation,CRT and GCT exhibited significant changes(P<0.05).Among these measures,CRT was significantly higher at one and three months postoperative(all P<0.01).GCT was significantly higher at 1 wk,1,and 3 mo postoperative(all P<0.01).Changes in VD and SD were nonsignificant in both the SCP and DCP.There was no difference in postoperative changes between the ICL and Toric ICL groups.CONCLUSION:ICL and Toric ICL implantation both have good efficacy and safety for myopic eyes,but macular area changes that occur after surgery need attention.

Effect of femtosecond laser-assisted lens surgery on the optic nerve head and the macula

AIM: To evaluate the effect of femtosecond laser-assisted lens surgery(FLALS;cataract surgery or refractive lens exchange) on the structure of the optic nerve head and the macula.METHODS: This prospective longitudinal study included healthy eyes undergoing FLALS. Eyes with glaucoma or any other ocular disease that could alter optical coherence tomography results were excluded. Retinal nerve fiber layer(RNFL), Bruch’s membrane opening-minimum rim width(BMO-MRW) and macular thickness(MT) were measured preoperatively, 1 and 6 mo after surgery using spectral-domain optical coherence tomography(SD-OCT). Changes between preoperative and postoperative values were evaluated.RESULTS: A total of 87 eyes of 46 patients were included in this study. Preoperative RNFL, BMO-MRW and MT in microns(μm) were 100.77±10.39, 330.31±49.99 and 276.30±33.39, respectively. Postoperative RNFL, BMO-MRW and MT were 104.74±11.55, 348.32±54.05 and 279.83±22.65 1 mo after surgery and 102.93±11.17, 343.11±53.4 and 278.90±22.19 6 mo after surgery, respectively;which equals an increase of 3.93%, 5.45% and 1.27%,respectively, 1 mo after surgery, and 2.14%, 3.87% and 0.94% 6 mo after surgery. The differences between the preoperative and the postoperative RNFL and BMO-MRW values were statistically significant(P<0.001). Regarding MT values, there were not statistically significant differences(P=0.26).CONCLUSION: Our study suggests that FLALS does not have a negative impact on the structural status of the optic nerve head in healthy eyes, assessed by SD-OCT. There is a slight increase in the values of RNFL, BMO-MRW and MT 1 mo and 6 mo after surgery.

Relationship between Myopia and Optical Components - A Study among Chinese Hong Kong Student Population

Purpose: To establish the prevalence and severity of myopia among the Chinese Hong Kong students and to study the relationship between myopia and optical components.Methods;One thousand and seventy-five freshmen of the 1993-1994 academic year in the Chinese University of Hong Kong underwent the eye examination including evaluation of refractive error, keratometry, and A-scan ultrasonic biometry. The data were analyzed with the SPSS/PC+4. 01 statistical package. Results: The prevalence of myopia was 91. 7% with the mean refraction being -4. 00 ± 2. 64D in this young adult population. The statistical analyses demonstrated a significant correlation between refractive value and axial length of the globe (r=-0. 78), vitreous length (r=-0. 76), anterior chamber depth (r=-0. 33), lens thickness (r = 0. 13) and corneal curvature (r = 0. 19). Conclusion: The refractive status is mainly dependent on the axial length. In general, the higher the myopia was, the longer the eyeball, the deeper the anterior chamber,

Optical design of adjustable light emitting diode for different lighting requirements

Light emitting diode （LED） sources have been widely used for illumination. Optical design, especially freedom compact lens design is necessary to make LED sources applied in lighting industry, such as large-range interior lighting and small-range condensed lighting. For different lighting requirements, the size of target planes should be variable. In our paper we provide a method to design freedom lens according to the energy conservation law and Snell law through establishing energy mapping between the luminous flux emitted by a Lambertian LED source and a certain area of the target plane. The algorithm of our design can easily change the radius of each circular target plane, which makes the size of the target plane adjustable. Ray-tracing software Tracepro is used to validate the illuminance maps and polar-distribution maps. We design lenses for different sizes of target planes to meet specific lighting requirements.