AIM: To compare the results of noncycloplegic photorefraction, cycloplegic photorefraction and cycloplegic refraction in preschool and non-verbal children.METHODS: One hundred and ninety-six eyes of 98children(50 fema...AIM: To compare the results of noncycloplegic photorefraction, cycloplegic photorefraction and cycloplegic refraction in preschool and non-verbal children.METHODS: One hundred and ninety-six eyes of 98children(50 females, 48 males) were included in the study. Firstly, non-cycloplegic photorefraction was achieved with Plusoptix A09; secondly, cycloplegic photorefraction was carried out with Plusoptix A09 after10 min cyclopentolate. Finally, 30 min after instillation of twice cyclopentolate, cycloplegic refraction was obtained with autorefraction and/or standard retinoscopy. Spheric equivalent, spheric power, cylindric power and cylindrical axis measurements were statistically compared.RESULTS: The mean age was 28.8±18.5mo(range12-72mo). The differences in spherical equivalent, spheric power and cylindrical power measured by the three methods were found statistically significant(P 【0.05).The spherical equivalent and spheric power measured by cycloplegic photorefraction were statistically higher than the measurements of the other methods(P 【0.05). The cylindrical power measured by cycloplegic refraction was statistically lower than the measurements of the photorefraction methods(P 【0.05). There was no significant difference in cylindrical axis measurements between three methods(P 】0.05).CONCLUSION: For the determination of refractive errors in children, the Plusoptix A09 measurements give incorrect results after instillation of cyclopentolate.Additionally, the cylindrical power measured by Plusoptix A09 with or without cycloplegia is higher. However, the non-cycloplegic Plusoptix A09 measures spheric equivalent and spheric power similar to cycloplegic refraction measurements in preschool and non-verbal children.展开更多
1 Introduction Lithium niobate crystal (LN) has photoelectric effect and nonlinear optic effect, whose properties may be improved by doping impure ions. The study on the Fe: LN crystal was developed early and the holo...1 Introduction Lithium niobate crystal (LN) has photoelectric effect and nonlinear optic effect, whose properties may be improved by doping impure ions. The study on the Fe: LN crystal was developed early and the holographic storage, optical amplification and phase conjugation mirror have been carried out, but at present, many problems on the research of Fe: LN crystal are unresolved, for example, the absorption is strong for A_r^+-ion laser beam, the energy loss of light source is large, the scattering of the output light beam is intense, the spatial distribution is not uniform, etc. Therefore, it is necessary to fur-展开更多
AIM:To analyze the two-year visual and refractive outcomes as well as the safety,and efficacy of photorefractive keratectomy(PRK)surgery for myopia.METHODS:In this prospective cohort study,63 eligible patients were re...AIM:To analyze the two-year visual and refractive outcomes as well as the safety,and efficacy of photorefractive keratectomy(PRK)surgery for myopia.METHODS:In this prospective cohort study,63 eligible patients were recruited,including 45 women(71.4%)and 18 men(28.6%).Demographic characteristics along with pre-and post-operative clinical data including visual acuity,refraction,maximum ablation,spherical and cylindrical error,and residual stromal bed(RSB)were evaluated.RESULTS:The mean age of the patients was 35.42±8.16y(range 22 to 55y).The mean spherical and cylindrical error before surgery were-2.23±1.58 D(range-5 to+0.25)and-1.24±0.94 D,respectively(range-3.75 to 0.00).The mean efficacy and safety of PRK surgery at 2y follow-up were 0.98±0.06 and 1.01±0.04 respectively.The lower age was significantly correlated with a higher amount of efficacy index(P<0.001,r=-0.42).Also,the lower amount of preoperative myopia and spherical equivalent(SE)were correlated with a higher safety index(P<0.001,r=-0.44;P<0.001,r=-0.46).CONCLUSION:The two-year efficacy and safety of PRK for the treatment of low myopia is excellent.Younger age and lower amount of refractive error are correlated with higher efficacy and safety indices of the surgery.展开更多
AIM:To study the effect of mitomycin C(MMC)applied during transepithelial photorefractive keratectomy(TPRK)on the corneal endothelium one week(W1)and three months(M3)after surgery and its determinants.METHODS:In this ...AIM:To study the effect of mitomycin C(MMC)applied during transepithelial photorefractive keratectomy(TPRK)on the corneal endothelium one week(W1)and three months(M3)after surgery and its determinants.METHODS:In this two-armed cohort study conducted in 2022,eyes treated with MMC during TPRK(group 1)were compared with eyes not treated with MMC(group 2).The corneal endothelial cell(EC)count,EC density(ECD;cells/mm2),average(μm2),standard deviation(μm2),coefficient of variation(CV%),ECmax,ECmin,and EC percentage of hexagonality were estimated at W1 and M3.The postoperative changes in the EC count in the two groups were compared and correlated with the other independent variables.RESULTS:Group 1 had 26 eyes,and group 2 had 78 eyes.All TPRK indices were significantly higher for the eyes in group 1 than for those in group 2.The MMC usage was not a significant predictor of the change in ECD(P=0.644),change in CV(P=0.374),and change in the percentage of hexagonality of EC(P=0.164)at W1.However,the use of MMC was a significant predictor of changes in CV(P=0.014)and the change in the percentage of hexagonality of EC(P=0.039)at M3.The duration of laser exposure and the size of the optical zone influenced the correlation of MMC use with the changes in EC indices,postoperatively.CONCLUSION:The use of MMC doesn’t affect ECD,CV,and percentage of hexagonality at W1 if other surgical indices are considered.At M3 after operating myopic eyes by TPRK,MMC significantly influence the CV and percentage of hexagonality.The duration of the laser application and the size of the optical zone should be considered when determining the effect of MMC on the EC indices.展开更多
We have grown triply doped Mg:Fe:Mn:LiTaO3 crystals with near stoichiometry using the top seeded solution growth technique. The defect structure was investigated by infrared absorption spectra and Curie temperature. U...We have grown triply doped Mg:Fe:Mn:LiTaO3 crystals with near stoichiometry using the top seeded solution growth technique. The defect structure was investigated by infrared absorption spectra and Curie temperature. Using a blue laser as the source, excellent photorefractive properties were obtained. Nonvolatile holographic storage properties were investigated using the dual wavelength technique. We got a very high fixed diffraction efficiency and nonvolatile holographic storage sensitivity. The blue light has more than enough energy to excite holes of deep(Mn) and shallow(Fe) trap centers with the same phase, which enhance dramatically the blue photorefractive properties and the nonvolatile holographic storage. Mg2+ ion is no longer damage resistant at blue laser, but enhances photorefractive characteristics.展开更多
Bi 12 TiO 20 (BTO)crystals have same structure as that of the Bi 12 SiO 20 (BSO)which is one of the most popular photorefractive materials.And both of them belong to cubic non centrosymmetric nonferroelectric material...Bi 12 TiO 20 (BTO)crystals have same structure as that of the Bi 12 SiO 20 (BSO)which is one of the most popular photorefractive materials.And both of them belong to cubic non centrosymmetric nonferroelectric materials.The cubic nonferroelectric oxides exhibit a number of advantages such as higher sensitivity and faster respond for applications in photorefractive.Compared to BSO,BTO have the largest electro optical coefficient and lower optical activity,especially it exhibits much high photosensitivity in the red light region that permits to use a cheap He Ne laser.It is,therefore,of high potential for applications in optical devices.展开更多
ZnO(4mol%),In 2O 3(1mol%)and Fe 2O 3(0.05mol%)were doped in LiNbO 3 and Czochralski method was used to grow Zn∶In∶Fe∶LiNbO 3 crystal.The diameter of the crystal we grew is 30mm.The technology parameter we took is t...ZnO(4mol%),In 2O 3(1mol%)and Fe 2O 3(0.05mol%)were doped in LiNbO 3 and Czochralski method was used to grow Zn∶In∶Fe∶LiNbO 3 crystal.The diameter of the crystal we grew is 30mm.The technology parameter we took is that the axial temperature gradient is 40℃/cm,the growth rate is 1mm/h, the rotation rate is 15-25r/min,the temperature of polarization is 1220℃ and the current density of polarization is 5mA/cm 2.The wafer dimension is 10mm×10mm×3mm and was covered in Li 2CO 3 powder to reduce.The reduction temperature is 500℃ and reduction time is 30 hours. OH - stretch vibration transmission spectra were measured by Fourier infrared spectrophotometer. There are two absorption peaks in OH - spectra of Zn∶In∶Fe∶LiNbO 3,in which one is at 3534cm -1 (2.83μm) and the other is at 3505cm -1 (2.85μm).The peak at 2.85μm is far lower than that at 2.83μm. Because of the threshold effect of Zn 2+ and In 3+ ,the peak at 2.83μm is generated and the peak at 2.85μm is related with Fe 3+ .In LiNbO 3 only doped with Fe,Li + site is taken place by Fe 3+ .When doping Zn 2+ and In 3+ in high concentration,these two ions take place Nb that is at Li site and Fe 3+ substitutes for Nb 5+ at the same time.The interaction between Fe 3+ and OH - make the OH - peak shift to 2.85μm.展开更多
Accommodative response and its possible role in myopia development has been explored through the study of the microfluctuations(MFs) of accommodation, which are commonly divided in high(1.0 to 2.3 Hz) and low(0.1 to 0...Accommodative response and its possible role in myopia development has been explored through the study of the microfluctuations(MFs) of accommodation, which are commonly divided in high(1.0 to 2.3 Hz) and low(0.1 to 0.6 Hz) frequency components. Previous research efforts have evidenced that a certain percentage of the amplitude of MFs seems not to originate in the accommodative response. We aimed to develop and test a new approach to reduce this non-accommodative noise. For this purpose, ten healthy participants were enrolled to determine the difference between the amplitude of MFs at near and distance for each range of frequencies, which was defined as the relative amplitude of MFs. The findings support the exploration of the relative rather than absolute values of the amplitude of MFs to better understand the contribution of both accommodative and non-accommodative factors to MFs.展开更多
The dielectric properties of near-stoichiometric LiNbO3：Fe and LiNbO3：Ce single crystals have been investigated using terahertz time domain spectroscopy in a frequency range of 0.71.6 THz at room temperature. When c...The dielectric properties of near-stoichiometric LiNbO3：Fe and LiNbO3：Ce single crystals have been investigated using terahertz time domain spectroscopy in a frequency range of 0.71.6 THz at room temperature. When coupled with an applied external optical field, obvious photorefractive effects were observed, resulting in a modulation of the complex dielectric constant for the crystals. The variation in refractive index, ｜△n｜, had a linear relationship with the applied light intensity, accompanied by a step-like decrease at high intensity. The findings were attributed to the internal space charge field of the photorefraction and the light-induced domain reversal in the crystals.展开更多
The photorefractive properties of lithium niobate crystals depend strongly on the kind of doping admixture. Study of LiNbO3 crystals with various doping admixtures using photorefractive light scattering allows insight...The photorefractive properties of lithium niobate crystals depend strongly on the kind of doping admixture. Study of LiNbO3 crystals with various doping admixtures using photorefractive light scattering allows insight into the processes taking place in the crystals. This paper presents new experimental results of non-selective and selective photorefractive light scattering investigations into rhodium-doped lithium niobate crystals and proposes a model to explain the experimental data.展开更多
This paper predicts that grey spatial solitons can exist in two-photon photorefractive materials. In steady state and undcr appropriate external bias conditions, it obtains the grey spatial soliton solutions of the op...This paper predicts that grey spatial solitons can exist in two-photon photorefractive materials. In steady state and undcr appropriate external bias conditions, it obtains the grey spatial soliton solutions of the optical wave evolution equation. The intensity profile, phase distribution, and transverse velocity of these grey solitons are discussed.展开更多
AIM:To investigate quantitative and qualitative optical outcomes of single-step transepithelial photorefractive keratectomy(Trans PRK)in high myopia.METHODS:In a prospective interventional case-series,30 eyes with hig...AIM:To investigate quantitative and qualitative optical outcomes of single-step transepithelial photorefractive keratectomy(Trans PRK)in high myopia.METHODS:In a prospective interventional case-series,30 eyes with high myopia(-6.00 to-8.75 D)with(up to-3.00 D)or without astigmatism were enrolled from Bina Eye Hospital,Tehran,Iran.One-step Trans PRK was performed with aberration-free aspherical optimized profile and SCHWIND AMARIS 500 laser.One-year follow-up results for refraction,visual acuities,vector analysis,ocular wavefront(OWF)and corneal wave-front(CWF)higher order aberrations(HOA),contrast sensitivity(CS),and postoperative haze were assessed.RESULTS:After the surgery,both photopic and mesopic CSs significantly improved(both P〈0.001).We detected significant induction of OWF coma and trefoil(P〈0.001 for both)HOAs;CWF coma(P=0.002),spherical(P〈0.001),and tetrafoil(P=0.003)HOAs in 6 mm analysis diameter;and CWF trefoil(P=0.04)HOA in 4 mm analysis diameter.The range of mean induction observed for various HOAs was0.005-0.11μm.The 86.7%of eyes reached an uncorrected distance visual acuity of 20/20 or better;96.7%of eyes were within±0.5 D of targeted spherical refraction.In vector analysis,mean correction index value was 1.03 and mean index of success was 0.22.By 12mo after the operation,no eye lost any number of corrected distancevisual acuity lines.We detected no corneal haze greater than 1~+throughout the follow-up.CONCLUSION:Our findings show promising effects of single-step Trans PRK on quality of vision in high myopic eyes.It also improves refraction and visual acuity.展开更多
AIM: To evaluate postoperative pain, uncorrected visual acuity (UCVA), and cornea haze value after transepithelial photorefractive keratectomy (T-PRK) performed with aspherical ablation profile using SCHWIND ESIRIS ex...AIM: To evaluate postoperative pain, uncorrected visual acuity (UCVA), and cornea haze value after transepithelial photorefractive keratectomy (T-PRK) performed with aspherical ablation profile using SCHWIND ESIRIS excimer laser. METHODS: Retrospective case series. Fifty-nine eyes (32 patients) with myopia associated with or without astigmatism underwent phototherapeutic keratectomy (PTK) followed by photorefractive keratectomy (PRK) which performed by Optimized Refractive Keratecomy (ORK)-CAM software based on aspherical ablation profile using SCHWIND ESIRIS excimer laser. Postoperative pain scale was measured on a questionnaire through five levels. Haze was graded by five grades, and UCVA, manifest refraction spherical equivalent (MRSE) were analyzed. RESULTS: Mean pain level was (1.37 +/- 0.613) (range: 1 to 3), the mean time picking out the soft contact lens was (6.22 +/- 1.73) days, at 3 months, UCVA was 1.0 for 40 eyes (67.8%), 0.5 for all eyes (100.0%). The UCVA was significantly less than the preoperative best spectacle corrected visual acuity (BSCVA) (t=-2.84, P=0.006), haze value was (0.27 +/- 0.25), no patients had a haze grade up to 2. Mean MRSE was (0.76 +/- 0.96) diopter(D) by 3 months. CONCLUSION: The outcomes from this study show that using the SCHWIND ESIRIS aspherical ablation profile for transepithelial PRK has a good visual result. The primary advantage is related to a spherical ablation profile, automatically considers the ablation volume of the stroma and the accurate and smooth removal of the epithelium with PTK. Additional studies are needed to determine long-term outcomes.展开更多
Laser refractive surgery is one of the most performed surgical procedures in the world. Although regarded safe and efficient, it has side effects. All of the laser based refractive surgical procedures invoke corneal n...Laser refractive surgery is one of the most performed surgical procedures in the world. Although regarded safe and efficient, it has side effects. All of the laser based refractive surgical procedures invoke corneal nerve injury to some degree. The impact of this denervation can range from mild discomfort to neurotrophic corneas. Currently, three techniques are widely used for laser vision correction: small incision lenticule extraction, laser-assisted keratomileusis in situ and photorefractive keratotomy. Each of these techniques affects corneal innervation differently and has a different pattern of nerve regeneration. The purpose of this review is to summarize the different underlying mechanisms for corneal nerve injury and compare the different patterns of corneal reinnervation.展开更多
Holographic display has attracted widespread interest because of its ability to show the complete information of the object and bring people an unprecedented sense of presence. The absence of ideal recording materials...Holographic display has attracted widespread interest because of its ability to show the complete information of the object and bring people an unprecedented sense of presence. The absence of ideal recording materials has hampered the realization of their commercial applications. Here we report that the response time of a bismuth and magnesium codoped lithium niobate(LN:Bi,Mg) crystal is shortened to 7.2 ms and a sensitivity as high as 646 cm/J. The crystal was used to demonstrate a real-time holographic display with a refresh rate of 60 Hz, as that of the popular high-definition television. Moreover, the first-principles calculations indicate that the electron mobility while Bi occupying Nb-site is significantly greater than that in Li-site, which directly induces the fast response of LN:Bi,Mg crystals when the concentration of Mg is above its doping threshold.展开更多
AIM：To assess the safety,efficacy,predictability and stability of implantable collamer lens（ICL） for residual refractive error after corneal refractive surgery.METHODS： This study evaluated 19 eyes of 12 patients ...AIM：To assess the safety,efficacy,predictability and stability of implantable collamer lens（ICL） for residual refractive error after corneal refractive surgery.METHODS： This study evaluated 19 eyes of 12 patients who underwent ICL implantation after corneal refractive surgeries.They were followed up for 1y to 5y of uncorrected distance visual acuity（UDVA）,corrected distance visual acuity（CDVA）,manifest refractive error,flat and steep K value,axial length,intraocular pressure,corneal endothelial cell density,adverse events after ICL surgery.RESULTS： The mean follow-up period was 39.05 ±19.22 mo（range,1-5y）.Spherical equivalent refractive error changed from-7.45±3.02 D preoperatively to-0.85±1.10 D 1wk to 1mo after ICL implantation,with the safety and efficacy indices being 1.12 and 1.15,respectively.A total of 52.63% of eyes were within ±0.5 D of the predicted spherical equivalents,73.68% were within ±1.0 D.A trend of mild regression towards myopia with axial elongation after 5y was observed.One eye with mild anterior capsule opacity and retinal detachment 1y after surgery were observed.CONCLUSION： ICL implantation is safe and effective for the correction of residual refractive error after corneal refractive surgeries,especially in moderate to high residual myopia.展开更多
We investigate theoretically the temperature effects on the evolution and stability of a separate screening brightdark soliton pair formed in a serial non-photovoltaic photorefractive crystal circuit. Our numerical re...We investigate theoretically the temperature effects on the evolution and stability of a separate screening brightdark soliton pair formed in a serial non-photovoltaic photorefractive crystal circuit. Our numerical results show that, for a stable bright-dark soliton pair originally formed in a crystal circuit at given temperatures, when one crystal temperature changes, the soliton supported by the other crystal will evolve into another stable soliton if the temperature change is quite small, whereas it will become unstable and experience larger cycles of compression or break up into beam filaments if the temperature difference is big enough. The dark soliton is more sensitive to the temperature change than the bright one.展开更多
AIM:To evaluate the efficacy and safety of the excimer laser correction of the residual refractive errors after cataract extraction with intraocular lens(IOL)implantation in uncommon cases.METHODS:Totally 24 patients ...AIM:To evaluate the efficacy and safety of the excimer laser correction of the residual refractive errors after cataract extraction with intraocular lens(IOL)implantation in uncommon cases.METHODS:Totally 24 patients with high residual refractive error after cataract surgery with IOL implantation were examined.Twenty-two patients had a history of phacoemulsification and IOL implantation,and two had extra-capsular cataract extraction with IOL implantation.Detailed examination of preoperative medical records was done to explain the origin of the post-cataract refractive errors.All patients underwent photorefractire keratectomy(PRK)enhancement.The mean outcome measures were refraction,uncorretted visual acuity(UCVA),best corrected visual acuity(BCVA)and corneal transparency and follow up ranged from 1 to 8 y.RESULTS:The principal causes of residual ametropia was inexact IOL calculation in abnormal eyes with high myopia and congenital lens abnormalities,followed by corneal astigmatism both suture induced and preexisting.After cataract surgery and before the laser enhancement the mean spherical equivalent(SE)was-0.56±3 D ranging from-4.62 to+2.25 D in high myopic patients,instead it was-1±1.73 D ranging from-3.25 to+3.75 D in the astigmatic eyes,with a mean cylinder of-3.75±0 ranging from-3 to+5.50 D.After laser refractive surgery the mean SE was 0.1±0.73,ranging from-0.50 to+1.50 in the myopic group,and it was-0.50±0.57 ranging from-1.25 to+0.50 in astigmatic patients,with a mean cylinder of-0.25±0.75.In myopic patients the mean UCVA and BCVA were 0.038±0.072 logMAR and 0.018±0.04 respectively,both ranging from 0.10 to 0.0.In astigmatic patients,the mean UCVA and BCVA were 0.213±0.132 and 0.00±0.0 respectively,UCVA ranging from 0.50 to 0.22 and BCVA was 0.00.All patients presented normal corneal transparency.No ocular hypertension was detected and no corneal haze was observed.All registered values remained stable also at the end line evaluation.CONCLUSION:The excimer laser treatment of residual refractive errors after cataract surgery with IOL implantation in abnormal eyes resulted in satisfactory and stable visual outcome with good safety and efficacy.展开更多
AIM: To determine risk factors of regression and undercorrection following photorefractive keratectomy (PRK) in myopia or myopic astigmatism. METHODS: A case -control study was designed in which eyes with an indicatio...AIM: To determine risk factors of regression and undercorrection following photorefractive keratectomy (PRK) in myopia or myopic astigmatism. METHODS: A case -control study was designed in which eyes with an indication for re-treatment (AT) were defined as cases; primary criteria for RT indication, as assessed at least 9mo postoperatively, included an uncorrected distance visual acuity (UDVA) of 20/30 or worse and a stable refraction for more than 3mo. Additional considerations included optical quality symptoms and significant higher order aberrations (HOAs). Controls were chosen from the same cohort of operated eyes which had complete post-operative follow up data beyond 9mo and did not need RT. The cohort included patients who had undergone PRK by the Tissue-Saving (TS) ablation profile of Technolas 217z100 excimer laser (Bausch & Lomb, Rochester, NY, USA). Mitomycin C had been used in all of the primary procedures. RESULTS: We had 70 case eyes and 158 control eyes, and they were comparable in terms of age, sex and follow -up time (P values: 0.58, 1.00 and 0.89, respectively). Pre-operative spherical equivalent of more than -5.00 diopter (D), intended optical zone (OZ) diameter of less than 6.00 mm and ocular fixation instability during laser ablation were associated with AT indications (all P values <0.001). These factors maintained their significance in the multiple logistic regression model with odd ratios of 6.12, 6.71 and 7.89, respectively. CONCLUSION: Higher refractive correction (>-5.00 D), smaller OZ (<6.00 mm) and unstable fixation during laser ablation of PRK for myopia and myopic astigmatism were found to be strong predictors of undercorrection and regression.展开更多
Using fully incoherent white light emitted from an incandescent lamp and amplitude mask, we experimentally investigate the influence of several factors on the fabrication of the lattice in photovoltaic self-defocusing...Using fully incoherent white light emitted from an incandescent lamp and amplitude mask, we experimentally investigate the influence of several factors on the fabrication of the lattice in photovoltaic self-defocusing LiNbO3：Fe crystal, the factors include the orientation of the crystalline c axis relative to the principal axis of the photonic lattice and the filament, the diameter of input dark spot and the separation of the adjacent input dark spots. Experimental results reveal that the best fabricating condition of photonic lattices is that the principal axis of lattice is tilted for 45^o relative to the crystalline c axis which is parallel to the filament of the lamp. In addition, it is necessary that the diameter of the input dark spot is larger than the half of their separation.展开更多
文摘AIM: To compare the results of noncycloplegic photorefraction, cycloplegic photorefraction and cycloplegic refraction in preschool and non-verbal children.METHODS: One hundred and ninety-six eyes of 98children(50 females, 48 males) were included in the study. Firstly, non-cycloplegic photorefraction was achieved with Plusoptix A09; secondly, cycloplegic photorefraction was carried out with Plusoptix A09 after10 min cyclopentolate. Finally, 30 min after instillation of twice cyclopentolate, cycloplegic refraction was obtained with autorefraction and/or standard retinoscopy. Spheric equivalent, spheric power, cylindric power and cylindrical axis measurements were statistically compared.RESULTS: The mean age was 28.8±18.5mo(range12-72mo). The differences in spherical equivalent, spheric power and cylindrical power measured by the three methods were found statistically significant(P 【0.05).The spherical equivalent and spheric power measured by cycloplegic photorefraction were statistically higher than the measurements of the other methods(P 【0.05). The cylindrical power measured by cycloplegic refraction was statistically lower than the measurements of the photorefraction methods(P 【0.05). There was no significant difference in cylindrical axis measurements between three methods(P 】0.05).CONCLUSION: For the determination of refractive errors in children, the Plusoptix A09 measurements give incorrect results after instillation of cyclopentolate.Additionally, the cylindrical power measured by Plusoptix A09 with or without cycloplegia is higher. However, the non-cycloplegic Plusoptix A09 measures spheric equivalent and spheric power similar to cycloplegic refraction measurements in preschool and non-verbal children.
基金Project supported by the National Natural Science Foundation of China
文摘1 Introduction Lithium niobate crystal (LN) has photoelectric effect and nonlinear optic effect, whose properties may be improved by doping impure ions. The study on the Fe: LN crystal was developed early and the holographic storage, optical amplification and phase conjugation mirror have been carried out, but at present, many problems on the research of Fe: LN crystal are unresolved, for example, the absorption is strong for A_r^+-ion laser beam, the energy loss of light source is large, the scattering of the output light beam is intense, the spatial distribution is not uniform, etc. Therefore, it is necessary to fur-
文摘AIM:To analyze the two-year visual and refractive outcomes as well as the safety,and efficacy of photorefractive keratectomy(PRK)surgery for myopia.METHODS:In this prospective cohort study,63 eligible patients were recruited,including 45 women(71.4%)and 18 men(28.6%).Demographic characteristics along with pre-and post-operative clinical data including visual acuity,refraction,maximum ablation,spherical and cylindrical error,and residual stromal bed(RSB)were evaluated.RESULTS:The mean age of the patients was 35.42±8.16y(range 22 to 55y).The mean spherical and cylindrical error before surgery were-2.23±1.58 D(range-5 to+0.25)and-1.24±0.94 D,respectively(range-3.75 to 0.00).The mean efficacy and safety of PRK surgery at 2y follow-up were 0.98±0.06 and 1.01±0.04 respectively.The lower age was significantly correlated with a higher amount of efficacy index(P<0.001,r=-0.42).Also,the lower amount of preoperative myopia and spherical equivalent(SE)were correlated with a higher safety index(P<0.001,r=-0.44;P<0.001,r=-0.46).CONCLUSION:The two-year efficacy and safety of PRK for the treatment of low myopia is excellent.Younger age and lower amount of refractive error are correlated with higher efficacy and safety indices of the surgery.
文摘AIM:To study the effect of mitomycin C(MMC)applied during transepithelial photorefractive keratectomy(TPRK)on the corneal endothelium one week(W1)and three months(M3)after surgery and its determinants.METHODS:In this two-armed cohort study conducted in 2022,eyes treated with MMC during TPRK(group 1)were compared with eyes not treated with MMC(group 2).The corneal endothelial cell(EC)count,EC density(ECD;cells/mm2),average(μm2),standard deviation(μm2),coefficient of variation(CV%),ECmax,ECmin,and EC percentage of hexagonality were estimated at W1 and M3.The postoperative changes in the EC count in the two groups were compared and correlated with the other independent variables.RESULTS:Group 1 had 26 eyes,and group 2 had 78 eyes.All TPRK indices were significantly higher for the eyes in group 1 than for those in group 2.The MMC usage was not a significant predictor of the change in ECD(P=0.644),change in CV(P=0.374),and change in the percentage of hexagonality of EC(P=0.164)at W1.However,the use of MMC was a significant predictor of changes in CV(P=0.014)and the change in the percentage of hexagonality of EC(P=0.039)at M3.The duration of laser exposure and the size of the optical zone influenced the correlation of MMC use with the changes in EC indices,postoperatively.CONCLUSION:The use of MMC doesn’t affect ECD,CV,and percentage of hexagonality at W1 if other surgical indices are considered.At M3 after operating myopic eyes by TPRK,MMC significantly influence the CV and percentage of hexagonality.The duration of the laser application and the size of the optical zone should be considered when determining the effect of MMC on the EC indices.
基金Project supported by the National Natural Science Foundation of China （Grant No. 51202045）, the Postdoctoral Science Foundation of Heilongjiang Province, China, and the Fundamental Research Funds for the Central Universities of Ministry of Education of China （Grant No. HIT. NSRIF. 2013004）.
文摘We have grown triply doped Mg:Fe:Mn:LiTaO3 crystals with near stoichiometry using the top seeded solution growth technique. The defect structure was investigated by infrared absorption spectra and Curie temperature. Using a blue laser as the source, excellent photorefractive properties were obtained. Nonvolatile holographic storage properties were investigated using the dual wavelength technique. We got a very high fixed diffraction efficiency and nonvolatile holographic storage sensitivity. The blue light has more than enough energy to excite holes of deep(Mn) and shallow(Fe) trap centers with the same phase, which enhance dramatically the blue photorefractive properties and the nonvolatile holographic storage. Mg2+ ion is no longer damage resistant at blue laser, but enhances photorefractive characteristics.
文摘Bi 12 TiO 20 (BTO)crystals have same structure as that of the Bi 12 SiO 20 (BSO)which is one of the most popular photorefractive materials.And both of them belong to cubic non centrosymmetric nonferroelectric materials.The cubic nonferroelectric oxides exhibit a number of advantages such as higher sensitivity and faster respond for applications in photorefractive.Compared to BSO,BTO have the largest electro optical coefficient and lower optical activity,especially it exhibits much high photosensitivity in the red light region that permits to use a cheap He Ne laser.It is,therefore,of high potential for applications in optical devices.
文摘ZnO(4mol%),In 2O 3(1mol%)and Fe 2O 3(0.05mol%)were doped in LiNbO 3 and Czochralski method was used to grow Zn∶In∶Fe∶LiNbO 3 crystal.The diameter of the crystal we grew is 30mm.The technology parameter we took is that the axial temperature gradient is 40℃/cm,the growth rate is 1mm/h, the rotation rate is 15-25r/min,the temperature of polarization is 1220℃ and the current density of polarization is 5mA/cm 2.The wafer dimension is 10mm×10mm×3mm and was covered in Li 2CO 3 powder to reduce.The reduction temperature is 500℃ and reduction time is 30 hours. OH - stretch vibration transmission spectra were measured by Fourier infrared spectrophotometer. There are two absorption peaks in OH - spectra of Zn∶In∶Fe∶LiNbO 3,in which one is at 3534cm -1 (2.83μm) and the other is at 3505cm -1 (2.85μm).The peak at 2.85μm is far lower than that at 2.83μm. Because of the threshold effect of Zn 2+ and In 3+ ,the peak at 2.83μm is generated and the peak at 2.85μm is related with Fe 3+ .In LiNbO 3 only doped with Fe,Li + site is taken place by Fe 3+ .When doping Zn 2+ and In 3+ in high concentration,these two ions take place Nb that is at Li site and Fe 3+ substitutes for Nb 5+ at the same time.The interaction between Fe 3+ and OH - make the OH - peak shift to 2.85μm.
文摘Accommodative response and its possible role in myopia development has been explored through the study of the microfluctuations(MFs) of accommodation, which are commonly divided in high(1.0 to 2.3 Hz) and low(0.1 to 0.6 Hz) frequency components. Previous research efforts have evidenced that a certain percentage of the amplitude of MFs seems not to originate in the accommodative response. We aimed to develop and test a new approach to reduce this non-accommodative noise. For this purpose, ten healthy participants were enrolled to determine the difference between the amplitude of MFs at near and distance for each range of frequencies, which was defined as the relative amplitude of MFs. The findings support the exploration of the relative rather than absolute values of the amplitude of MFs to better understand the contribution of both accommodative and non-accommodative factors to MFs.
基金Project supported by the National Natural Science Foundation of China(Grant No.10974063)the Research Foundation of Wuhan National Laboratory,China(Grant No.P080008)the National Basic Research Program of China(Grant No.2007CB310403)
文摘The dielectric properties of near-stoichiometric LiNbO3：Fe and LiNbO3：Ce single crystals have been investigated using terahertz time domain spectroscopy in a frequency range of 0.71.6 THz at room temperature. When coupled with an applied external optical field, obvious photorefractive effects were observed, resulting in a modulation of the complex dielectric constant for the crystals. The variation in refractive index, ｜△n｜, had a linear relationship with the applied light intensity, accompanied by a step-like decrease at high intensity. The findings were attributed to the internal space charge field of the photorefraction and the light-induced domain reversal in the crystals.
文摘The photorefractive properties of lithium niobate crystals depend strongly on the kind of doping admixture. Study of LiNbO3 crystals with various doping admixtures using photorefractive light scattering allows insight into the processes taking place in the crystals. This paper presents new experimental results of non-selective and selective photorefractive light scattering investigations into rhodium-doped lithium niobate crystals and proposes a model to explain the experimental data.
基金Project supported by the National Natural Science Foundation of China （Grant No 60508005）, and Scientific Research Foundation of Harbin Institute of Technology of China （Grant No HIT. 2003. 31）.
文摘This paper predicts that grey spatial solitons can exist in two-photon photorefractive materials. In steady state and undcr appropriate external bias conditions, it obtains the grey spatial soliton solutions of the optical wave evolution equation. The intensity profile, phase distribution, and transverse velocity of these grey solitons are discussed.
文摘AIM:To investigate quantitative and qualitative optical outcomes of single-step transepithelial photorefractive keratectomy(Trans PRK)in high myopia.METHODS:In a prospective interventional case-series,30 eyes with high myopia(-6.00 to-8.75 D)with(up to-3.00 D)or without astigmatism were enrolled from Bina Eye Hospital,Tehran,Iran.One-step Trans PRK was performed with aberration-free aspherical optimized profile and SCHWIND AMARIS 500 laser.One-year follow-up results for refraction,visual acuities,vector analysis,ocular wavefront(OWF)and corneal wave-front(CWF)higher order aberrations(HOA),contrast sensitivity(CS),and postoperative haze were assessed.RESULTS:After the surgery,both photopic and mesopic CSs significantly improved(both P〈0.001).We detected significant induction of OWF coma and trefoil(P〈0.001 for both)HOAs;CWF coma(P=0.002),spherical(P〈0.001),and tetrafoil(P=0.003)HOAs in 6 mm analysis diameter;and CWF trefoil(P=0.04)HOA in 4 mm analysis diameter.The range of mean induction observed for various HOAs was0.005-0.11μm.The 86.7%of eyes reached an uncorrected distance visual acuity of 20/20 or better;96.7%of eyes were within±0.5 D of targeted spherical refraction.In vector analysis,mean correction index value was 1.03 and mean index of success was 0.22.By 12mo after the operation,no eye lost any number of corrected distancevisual acuity lines.We detected no corneal haze greater than 1~+throughout the follow-up.CONCLUSION:Our findings show promising effects of single-step Trans PRK on quality of vision in high myopic eyes.It also improves refraction and visual acuity.
文摘AIM: To evaluate postoperative pain, uncorrected visual acuity (UCVA), and cornea haze value after transepithelial photorefractive keratectomy (T-PRK) performed with aspherical ablation profile using SCHWIND ESIRIS excimer laser. METHODS: Retrospective case series. Fifty-nine eyes (32 patients) with myopia associated with or without astigmatism underwent phototherapeutic keratectomy (PTK) followed by photorefractive keratectomy (PRK) which performed by Optimized Refractive Keratecomy (ORK)-CAM software based on aspherical ablation profile using SCHWIND ESIRIS excimer laser. Postoperative pain scale was measured on a questionnaire through five levels. Haze was graded by five grades, and UCVA, manifest refraction spherical equivalent (MRSE) were analyzed. RESULTS: Mean pain level was (1.37 +/- 0.613) (range: 1 to 3), the mean time picking out the soft contact lens was (6.22 +/- 1.73) days, at 3 months, UCVA was 1.0 for 40 eyes (67.8%), 0.5 for all eyes (100.0%). The UCVA was significantly less than the preoperative best spectacle corrected visual acuity (BSCVA) (t=-2.84, P=0.006), haze value was (0.27 +/- 0.25), no patients had a haze grade up to 2. Mean MRSE was (0.76 +/- 0.96) diopter(D) by 3 months. CONCLUSION: The outcomes from this study show that using the SCHWIND ESIRIS aspherical ablation profile for transepithelial PRK has a good visual result. The primary advantage is related to a spherical ablation profile, automatically considers the ablation volume of the stroma and the accurate and smooth removal of the epithelium with PTK. Additional studies are needed to determine long-term outcomes.
文摘Laser refractive surgery is one of the most performed surgical procedures in the world. Although regarded safe and efficient, it has side effects. All of the laser based refractive surgical procedures invoke corneal nerve injury to some degree. The impact of this denervation can range from mild discomfort to neurotrophic corneas. Currently, three techniques are widely used for laser vision correction: small incision lenticule extraction, laser-assisted keratomileusis in situ and photorefractive keratotomy. Each of these techniques affects corneal innervation differently and has a different pattern of nerve regeneration. The purpose of this review is to summarize the different underlying mechanisms for corneal nerve injury and compare the different patterns of corneal reinnervation.
基金The National Key Research and Development Program of China(Grant No.2019YFA0705000)National Natural Science Foundation of China(No.12034010)Program for Changjiang Scholars and Innovative Research Team in University(No.IRT_13R29).
文摘Holographic display has attracted widespread interest because of its ability to show the complete information of the object and bring people an unprecedented sense of presence. The absence of ideal recording materials has hampered the realization of their commercial applications. Here we report that the response time of a bismuth and magnesium codoped lithium niobate(LN:Bi,Mg) crystal is shortened to 7.2 ms and a sensitivity as high as 646 cm/J. The crystal was used to demonstrate a real-time holographic display with a refresh rate of 60 Hz, as that of the popular high-definition television. Moreover, the first-principles calculations indicate that the electron mobility while Bi occupying Nb-site is significantly greater than that in Li-site, which directly induces the fast response of LN:Bi,Mg crystals when the concentration of Mg is above its doping threshold.
基金Supported by the Committee of Science and Technology of Shanghai,China(No.09411962100)the Health and Family Planning Committee of Pudong New District of Shanghai,China(No.PW2014D-1)
文摘AIM：To assess the safety,efficacy,predictability and stability of implantable collamer lens（ICL） for residual refractive error after corneal refractive surgery.METHODS： This study evaluated 19 eyes of 12 patients who underwent ICL implantation after corneal refractive surgeries.They were followed up for 1y to 5y of uncorrected distance visual acuity（UDVA）,corrected distance visual acuity（CDVA）,manifest refractive error,flat and steep K value,axial length,intraocular pressure,corneal endothelial cell density,adverse events after ICL surgery.RESULTS： The mean follow-up period was 39.05 ±19.22 mo（range,1-5y）.Spherical equivalent refractive error changed from-7.45±3.02 D preoperatively to-0.85±1.10 D 1wk to 1mo after ICL implantation,with the safety and efficacy indices being 1.12 and 1.15,respectively.A total of 52.63% of eyes were within ±0.5 D of the predicted spherical equivalents,73.68% were within ±1.0 D.A trend of mild regression towards myopia with axial elongation after 5y was observed.One eye with mild anterior capsule opacity and retinal detachment 1y after surgery were observed.CONCLUSION： ICL implantation is safe and effective for the correction of residual refractive error after corneal refractive surgeries,especially in moderate to high residual myopia.
基金Project supported by the National Natural Science Foundation of China （Grant Nos 10574051 and 10174025） and the Research Foundation for 0utstanding Young Teachers, China University of Geosciences （Grant No CUGQNL0621）.
文摘We investigate theoretically the temperature effects on the evolution and stability of a separate screening brightdark soliton pair formed in a serial non-photovoltaic photorefractive crystal circuit. Our numerical results show that, for a stable bright-dark soliton pair originally formed in a crystal circuit at given temperatures, when one crystal temperature changes, the soliton supported by the other crystal will evolve into another stable soliton if the temperature change is quite small, whereas it will become unstable and experience larger cycles of compression or break up into beam filaments if the temperature difference is big enough. The dark soliton is more sensitive to the temperature change than the bright one.
文摘AIM:To evaluate the efficacy and safety of the excimer laser correction of the residual refractive errors after cataract extraction with intraocular lens(IOL)implantation in uncommon cases.METHODS:Totally 24 patients with high residual refractive error after cataract surgery with IOL implantation were examined.Twenty-two patients had a history of phacoemulsification and IOL implantation,and two had extra-capsular cataract extraction with IOL implantation.Detailed examination of preoperative medical records was done to explain the origin of the post-cataract refractive errors.All patients underwent photorefractire keratectomy(PRK)enhancement.The mean outcome measures were refraction,uncorretted visual acuity(UCVA),best corrected visual acuity(BCVA)and corneal transparency and follow up ranged from 1 to 8 y.RESULTS:The principal causes of residual ametropia was inexact IOL calculation in abnormal eyes with high myopia and congenital lens abnormalities,followed by corneal astigmatism both suture induced and preexisting.After cataract surgery and before the laser enhancement the mean spherical equivalent(SE)was-0.56±3 D ranging from-4.62 to+2.25 D in high myopic patients,instead it was-1±1.73 D ranging from-3.25 to+3.75 D in the astigmatic eyes,with a mean cylinder of-3.75±0 ranging from-3 to+5.50 D.After laser refractive surgery the mean SE was 0.1±0.73,ranging from-0.50 to+1.50 in the myopic group,and it was-0.50±0.57 ranging from-1.25 to+0.50 in astigmatic patients,with a mean cylinder of-0.25±0.75.In myopic patients the mean UCVA and BCVA were 0.038±0.072 logMAR and 0.018±0.04 respectively,both ranging from 0.10 to 0.0.In astigmatic patients,the mean UCVA and BCVA were 0.213±0.132 and 0.00±0.0 respectively,UCVA ranging from 0.50 to 0.22 and BCVA was 0.00.All patients presented normal corneal transparency.No ocular hypertension was detected and no corneal haze was observed.All registered values remained stable also at the end line evaluation.CONCLUSION:The excimer laser treatment of residual refractive errors after cataract surgery with IOL implantation in abnormal eyes resulted in satisfactory and stable visual outcome with good safety and efficacy.
文摘AIM: To determine risk factors of regression and undercorrection following photorefractive keratectomy (PRK) in myopia or myopic astigmatism. METHODS: A case -control study was designed in which eyes with an indication for re-treatment (AT) were defined as cases; primary criteria for RT indication, as assessed at least 9mo postoperatively, included an uncorrected distance visual acuity (UDVA) of 20/30 or worse and a stable refraction for more than 3mo. Additional considerations included optical quality symptoms and significant higher order aberrations (HOAs). Controls were chosen from the same cohort of operated eyes which had complete post-operative follow up data beyond 9mo and did not need RT. The cohort included patients who had undergone PRK by the Tissue-Saving (TS) ablation profile of Technolas 217z100 excimer laser (Bausch & Lomb, Rochester, NY, USA). Mitomycin C had been used in all of the primary procedures. RESULTS: We had 70 case eyes and 158 control eyes, and they were comparable in terms of age, sex and follow -up time (P values: 0.58, 1.00 and 0.89, respectively). Pre-operative spherical equivalent of more than -5.00 diopter (D), intended optical zone (OZ) diameter of less than 6.00 mm and ocular fixation instability during laser ablation were associated with AT indications (all P values <0.001). These factors maintained their significance in the multiple logistic regression model with odd ratios of 6.12, 6.71 and 7.89, respectively. CONCLUSION: Higher refractive correction (>-5.00 D), smaller OZ (<6.00 mm) and unstable fixation during laser ablation of PRK for myopia and myopic astigmatism were found to be strong predictors of undercorrection and regression.
基金Supported by the National Natural Science Foundation of China under Grant Nos 60378013, 10474047, and 60278006.
文摘Using fully incoherent white light emitted from an incandescent lamp and amplitude mask, we experimentally investigate the influence of several factors on the fabrication of the lattice in photovoltaic self-defocusing LiNbO3：Fe crystal, the factors include the orientation of the crystalline c axis relative to the principal axis of the photonic lattice and the filament, the diameter of input dark spot and the separation of the adjacent input dark spots. Experimental results reveal that the best fabricating condition of photonic lattices is that the principal axis of lattice is tilted for 45^o relative to the crystalline c axis which is parallel to the filament of the lamp. In addition, it is necessary that the diameter of the input dark spot is larger than the half of their separation.
