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Background Cornea astigmatism can be effectively corrected by implanting Toric intraocular lens (IOL) during cataract surgery and therefore improve visual acuity of patients.However,the decentration and rotation position errors were inevitable sometime.What's the difference of effect of position errors on quality of image between spherical IOL and Toric IOL needs further research.Objective This study was to evaluate the optical performance and wavefront with rotation and decentration of Toric IOL.Methods Different decentration for SN60AT IOL(spherical IOL) and Toric IOL in Hwey-Lan Lion model eyes was set with the role as follows:decentration 0.25 mm to 0.75 mm in a 5°-interval from 0° to 90°.Furthermore,Toric IOL was rotated at 5° and 10°,respectively.Then the image performances of SN60AT IOL and Toric IOL at different decentration distances and rotated degrees were evaluated with modulation transfer function (MTF) and value of wavefront aberration under all conditions.Results At the centration,the MTF curves of spherical IOL and Toric IOL were similar under 3,4 and 5 mm pupil diameter at each spatial frequency.Under the condition of 4 mm pupil diameter,when the decentration was 0.25 mm,the MTF values of SN60AT IOL at 6 c/d and 12 c/d were 0.581 087 and 0.411 960,respectively.T3 IOL were 0.454 259 and 0.382 313,T4 IOL were 0.426 020 and 0.360 490,T5 IOL were 0.425 606 and 0.359 877.When the decentration was 0.50 mm,the MTF values of SN60AT at 6 c/d and 12 c/d were 0.573 073 and 0.412 787,respectively.T3 IOL were 0.450943 and 0.379481,T4 IOL were 0.423 153 and 0.356 664,T5 IOL were 0.422 881 and 0.356 230.When the decentration was 0.75 mm,the MTF values of SN60AT at 6 c/d and 12 c/d were 0.560 038 and 0.413 624,respectively.T3 IOL were 0.445 597 and 0.374 322,T4 IOL were 0.418 522 and 0.350 087,T5 IOL were 0.418 468 and 0.349 976.When the IOL decentralized along 0°,5°,10°,90°meridian line,the MTF values were almostly same.The root mean square (RMS) of spherical IOL and Toric IOL was increased when the IOL decentralized from 0 mm to 0.75 mm,with the most increasing level in coma aberration and slight increase in trefoil aberration.When the T4 IOL decentralized from centre to 0.75 mm,the coma increased from 0 to C(3,-1)-0.049 79 μm,C (3,1)-0.037 59 μm and the trefoil aberration increased from 0 to C (3,3) 0.005 72 μm,C (3,-3) 0.004 64 μm.With the increase of rotation degrees (from 5°to 10°) of Toric IOL,the MTF was worse at high spatial frequency.Toric IOL rotation caused the increase of astigmatism and residual astigmatism and spherical error,but not high order aberration.Conclusions The tolerance of Toric IOL to decentration is very close to the spherical IOL,and optical performance is only associated with the amount of decentration but not direction.The aberration caused by Toric IOL decentration is mainly coma.The rotation of Toric IOL causes astigmatism error but not high order aberrations.
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Background Silicon oil tamponade eyes following vitrectomy accelerate and induce lens opacification,so the accurate measurement and calculation of intraocular lens (IOL) diopter before cataract extraction+ IOL implantation is very important for the recovery of visual function.Objective This study was to compare the differences of IOL powers measured and calculated by different apparatus and different IOL power formulas before cataract extraction + IOL implantation silicon oil tamponade combined with cataractous eyes.Methods A prospective,consecutive,nonrandomized study was performed.Thirty-six silicon oil tamponade with cataract eyes of 36 patients were included in the Second Affiliated Hospital of Soochow University from August 2011 to October 2013.Patients with silicone oil emulsification for 4 months to 2 years prepared to treat by cataract extraction + IOL implantation+silicon oil removal.Axial length (AL),corneal curvature (CC) and anterior chamber depth (ACD) were measured with IOLMaster and A-scan with manual kerameter (MK) in the eyes for the prediction of IOL power by SRK-Ⅱ,SRK/T,Hoffer Q,Holladay 1 and Haigis formulas under the oral informed consent.The mean predictive error (MPE) and mean absolute refractive error (MAE) between predictive IOL diopters before operation and actual IOL diopters after operation were evaluated.Results The AL and ACD values measured by IOLMaster was (25.43± 0.90)mm and (3.22±0.38)mm,which were significantly higher than (25.21±1.02)mm and (3.07±0.62) mm by A-scan+ MK respectively,the difference between the two measure methods was statistical significance (both at P =0.000).No significant difference was found in measured CC values between IOLMaster and A-scan+MK ([44.58±1.57] D vs.[44.56±1.62] D) (P=0.568).When the parameters measured by IOLMaster were used,the MAE from SRK/T formula was smaller than that from SRK-Ⅱ,Hoffer Q,Holladay 1 and Haigis formulas (P =0.017,0.009,0.012,0.001),and the MAE from Haigis formula was significantly larger than that from SRK-Ⅱ,Hoffer Q and Holladay 1 formulas (P =0.026,0.035,0.021).When measured by A-scan + MK,the MAE from Haigis formula was significantly larger than that from SRK-Ⅱ,SRK/T,Hoffer Q and Holladay 1 formulas (P=0.007,0.004,0.018,0.006).There was no significant difference in the number of eyes with MAE ≤ 1.0 D between IOLMaster and A-scan+MK measurements under the calculation of SRK-Ⅰ,SRK/T,Hoffer Q and Holladay 1 formulas (x2 =0.107,2.250,0.845,0.084,all at P＞0.05).However,the number of eyes with MAE ≤ 1.0 D was significantly increased in IOLMaster measurement compared with A-scan+MK under the calculation of Haigis formula (x2 =4.431,P =0.035).Conclusions In silicon oil-filled cataract eyes,SRK/T formula appears to have a more accurate predictive value of IOL power than that of other formulas when employ IOLMaster;when use A-scan+MK measurement,the predictive value of IOL power seems to be better by using SRK-Ⅱ,SRK/T,Holladay 1 or Hoffer Q formulas.
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Background The development and progression of myopic eyes is biomechanical and dominated by axial elongation.The biomechanics change of stretching of the fundus and sclera appears to reduce its thickness and elastic modulus,which make eyeballs more susceptible to the distending forces of intraocular pressure (IOP).Objective This study was to analyz the axial length (AL) and IOP changes in different degree of myopia and investigate the roles of IOP in myopia development and AL elongation.Methods A prospective cases-controlled study was performed under the informed consent of patients and custodian.Four hundred and twenty-eight eyes of 428 children aged 4-14 years were enrolled in Affilicated Second Hospital of Zhengzhou University from February to December 2014.The patients were divided into 4 groups based on the refractive status.Ninety-three eyes of 93 patients were in the hyperopic-emmetropia group with the spherical equivalent (SE) of (1.81±2.32) D,192 eyes of 192 patients were in mild myopia group with the SE of (-1.43±0.74)D,83 eyes of 83 patients were in the moderate myopia group with the SE of (-4.09±0.89) D and 60 eyes of 60 patients were in the high myopia group with the SE of (-8.02±2.61) D.AL was measured by IOL Master system,IOP was measured by iCare tomnometer,and the central corneal thickness (CCT) was measured by OCT.The corrected IOP was calculated based on IOPcorrection =IOPGAT+(544-CCT)/37.03.The correlations between IOP ion and AL or diopter were analyzed.Results The AL values were (22.44±1.32) mm,(23.89±1.09) mm,(25.05±0.89) mm and (26.47±1.20) mm in the hyperopic-emmetropia group,mild myopia group,moderate myopia group and the high myopia group,showing a significant difference among the four groups (F =177.336,P =0.000).The IOP ion values were (15.24 ±2.73) mmHg,(17.51 ±2.98) mmHg,(17.94 ±2.34) mmHg and (18.49 ± 2.90) mmHg in the hyperopic-emmetropia group,mild myopia group,moderate myopia group and the high myopia group,with a significant difference among the four groups (F =22.104,P =0.000).The IOP tion values were significantly lower in the hyperopic-emmetropia group than that in the mild myopia group,moderate myopia group and high myopia group (all at P＜0.05),and the mean IOP tion value in the high myopia group was significantly higher than that in the mild myopia group (P =0.018).The IOP tion was negatively correlated with diopter (r =-0.384,P＜0.01) and positively correlated with AL (r =0.377,P＜0.01).Conclusions As the increase of myopic diopter and elongation of AL,IOPcorrection is considerably elevated in childhood.IOP tion rising in childhood probably promotes the progression of myopia and elongation of AL.
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Background Using tablet computer at a short distance is one of the risk factors resulting to pathogenesis and progression of myopia.Studying the effect of such device on accommodative system of human eyes can provide further insights into myopia control.Objective This study was to explore the influences of playing iPAD game for a short duration on accommodative response,accommodative microfluctuation and pupil diameter in adolescent myopia patients.Methods Sixty adolescent myopic patients were included in Peking University People 's Hospital from August 2014 to April 2015,with the mean age (11.6±2.6) years and mean spherical equivalent refraction (SER) (-2.38±1.08)D.The patients were randomly divided into 3 groups according to different playing duration of iPAD game,including 3-minute group,5-minute group and 10-minute group.An open-field infrared refractometer was used to record pupil diameter and accommodation-associated data before and after playing iPAD game.Accommodative response was defined as the difference between the recorded value and theoretical accommodative response,and root mean square (RMS) was used to describe the amplitude of accommodative microfluctuation.One-dimension discrete Fourier transformation was used to analyze spectral characteristic of accommodative response curve.Paired t tests were used to compare these accommodative parameters before and after playing game,while Wilcoxon signed-rank tests were applied for analyzing high frequency component of accommodative microfluctuation.This research conforms to the declaration of Helsinki,and was approved by Peking University People's Hospital Ethics Committee,all the subjects and their guardian signed informed consent.Results The accommodative response values before and after playing iPAD game in 10-minute group were (0.81 ±0.29)D and (0.74 ± 0.27) D,respectively,with significant difference between them (t =2.263,P =0.036),and no significant differences were found in the accommodative response values before and after playing iPAD game in the 3-minute group and 5-minute group (both at P＞0.05).The RMS after playing iPAD game was (0.31 ±0.08) D in the 10-minute group,which was significantly higher than (0.27 ± 0.09) D before playing iPAD game (t =-2.259,P =0.036).The high-frequency spectral power of accommodative response curves in all the three groups were increased after playing iPAD game in comparison with before playing iPAD game,with significant differences in the 5-minute group and 10-minute group (Z =-2.213,-2.016;both at P ＜ 0.05),and the pupil diameters were significantly decreased after playing iPAD game in comparison with before playing iPAD game,with significant differences in the 5-minute group and 10-minute group (t =2.428,P =0.026;t =2.515,P =0.021).Conclusions Short-term exposure to iPAD does not deteriorate accommodative lag in adolescent myopic patients.However,the increase of amplitude and high-frequency spectral power of accommodative microfluctuation,together with accommodation lag will result in blurred images and may bring adverse effects on myopic eyes.
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Background How to control progression of myopia is a central issue in clinical optometry.Some clinical trials showed that wearing base-in (BI) prism can slow down progression of myopia to certain degree.However,whether BI prism or base-out (BO) prism should be used is worth discussing.Objective This study was to investigate the influences of different prisms on accommodative response and microfluctuation in emmetropias.Methods This clinical trail was approved by Ethic Committee of Peking University People's Hospital.During July in 2014,twenty-two emmetropias of 22 normal volunteers aged 21-27 years were recruited from Peking University People's Hospital under the written informed consent.An open-field infrared refractometer was used to monitor and record pupil diameter and accommodative response under three conditions including non-prism,3△ BI prism,and 3△ BO prism.The accommodative response value was calculated as the difference between reading value and-3.0 D,and root mean square (RMS) of accommodative response value served as amplitude of accommodative microfluctuation.Spectrum of accommodative response was analyzed by one dimension discrete Fourier transformation.The differences of accommodative response value,amplitude of accommodative microfluctuation and pupil diameter among three conditions were compared using repeated one-way ANOVA.Results The accommodative response values were (+0.31±0.78),(+0.51±0.75) and (+0.18±0.72) D under the non-prism,3△BI prism and 3△BO prismconditions,respectively,with a significant difference among them (F =28.078,P =0.000),and compared with the non-prism condition,the accommodative lag of 3△BI prism condition was increased and that of 3△BO prism condition was reduced (P =0.000,0.012).No significant difference was found in the amplitude of accommodative microfluctuation among the three conditions (F=0.062,P =0.879).The percentages of low frequency signal power (0-0.5 Hz)/total power (0-2.5 Hz) was 97.5％,98.3％ and 91.4％ under the non-prism,3△BI prism and 3△BO prism condition,respectively.The pupil diameter was (5.37-±0.69) mm under the 3 △ BI prism condition,which was larger than (5.07±0.66) mm under the non-prism condition and (5.01 ±0.69) mm under the 3△ BO prism condition (both at P =0.000).Conclusions Compared with wearing 3△ BI prism,wearing 3△ BO prism lessens the accommodative lag,decreases the pupil diameter and reduces the power of low frequency component in accommodative response.
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Background Flicker light can induce myopia,but its mechanism remains unclear.As one of immediate early genes,early growth response-1 (Egr-1) gene can generate rapid response to visual stimulation,however,its effect on the formation and development of myopia is below understood.Objective This study was to investigate the dynamic expression of Egr-1 gene in retinas of flicker light-induced eyes (FL) and compare the results with form deprived eyes (FD).Methods One hundred and fifty 28-day-old C57BL/6J mice were randomly assigned to the normal control group,FD group and FL group.The right eyes of mice were occluded with a semitransparent hemispherical thin plastic shell for 2 weeks in the FD group,and the right eyes of mice were stimulated by 2 Hz flicker light for 2 weeks in the FL group,and then the mice were fed in the normal light environment for 1 week.The refractive state and axial length of the model eyes were measured by murine-specific eccentric infrared photorefraction and A-scan ultrasonography before modeling and 1 hour,I day,1 week,2 weeks after modeling as well as 1 week after termination,respectively.The mice were sacrificed in above-mentioned time points to isolate the retinas.The expressions and location of Egr-1 protein and mRNA in the retinas were detected by Western blot,and reverse transcription PCR (RT-PCR) and immunochemistry.The expressions of Egr-1 markers,neuron and protein kinase C (PKC)-α,in the retinas were assayed by using immunofluorescence.The care and use of the animals followed the administration regulations for experimental animals of Jiangsu Province.Results Two weeks after modeling,the refraction of the FL group was (0.32±0.14) D,which was significantly lower than (-0.66±0.43)D in the FD group (t=6.78,P=0.00).One hour after modeling,The expression levels of Egr-1 mRNA in mouse retinas were 0.626±0.044 and 0.695±0.058 in the FD group and FL group,which were significantly declined in comparison with 1.009±0.089 of the normal group (t=14.81,P=0.01;t=9.15,P=0.03).In 2 weeks after modeling,the expression levels of Egr-1 mRNA were still lower in the FD group and F:L group compared with the normal group (all at P＜0.05).However,the expression levels were significantly elevated in the FD group and FL group compared with the normal group (t=4.13,P=0.01;t=4.26,P=0.01) at 1 week after termination.Western blot showed a dynamic decrease in the expressions of Egr-1 protein with lapse of time in the FD group and FL group with the lowest expressing level in the second week after modeling.In I week after termination of modeling,the expressing level was raised in the FD group or the FL group,but it was still lower than that ir the normal group (t =6.32,P=0.00;t =5.45,P=0.01).Egr-1 protein was mainly expressed in the retinal ganglion cell (RGC) layer,inner nuclear layer and photoreceptor layer in the normal mice,and the expression intensity was obviously weaker in the FD mice and FL mice 2 weeks after modeling.Htowever,the expression was enhanced in 1 week after termination of modeling.Neuron and PKC-α were strongly expressed in the RGCs and bipolar cells in the normal mice.Conclusions The eyes show a myopic trend after induce of flicker light in B6 mice.The expression level of Egr-1 gene in the retina down-regulates with the reduce of refraction in FL eyes,and its dynamic expressing change is consistent between the FD eyes and FL eyes.
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Some intriguing concepts of visual optics cannot be explained by ray tracing. However, they can be clarified using wavefront formalism. Its main advantage is in the use of the concept of vergence, which is very helpful in interpreting the optical phenomena involved in the neutralization of the ametropias. In this line of thinking, the major role of a lens is in the creation of a new light source (the image point) that orientates the refracted waves. Once the nature and position of this source is known, one can easily predict the behavior of the wavefronts. The formalism also allows for an easier understanding on how wavefronts relate to light rays and on how algebraic signs are assigned to optical distances.
Alguns conceitos intrigantes da óptica visual não podem ser explicados pelo traçado dos raios luminosos. Entretanto, eles podem ser esclarecidos através do formalismo da frente de onda. A vantagem do mesmo está no uso do conceito de vergência, que facilita o entendimento dos fenômenos ópticos envolvidos na neutralização das ametropias. Nessa linha de raciocínio, a principal função de uma lente é o de criar de uma nova fonte de luz - o ponto de imagem - que orienta as ondas refratadas. Conhecendo-se a natureza e a posição dessa fonte pode-se facilmente prever o comportamento das frentes de onda. Este formalismo também ajuda a compreensão de como as frentes de onda se relacionam com os raios de luz e como os sinais algébricos são atribuídos às distâncias ópticas.
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Humans , Refraction, Ocular/physiology , Refractive Errors/diagnosis , Models, Theoretical , Optics and PhotonicsABSTRACT
Objective To observe the distribution of macular thickness and its relationship with axial length, gender, refraction status and race in six-year-old children. Methods 1543 six-year-old children from 34 schools in Sydney were randomly selected. The thickness of center macula(CM), inner macula(IM)and outer macula (OM)were measured by optical coherence tomography (OCT), the differences of macular thickness between different genders and races were comparatively analyzed. The axial length and refraction status of all children were measured by IOL Master and autorefractor RK-F1 respectively. Results The CM, IM and OM thickness of all those six-year-old children were normally distributed,on average they were 193.6, 264.3 and 236.9 μm respectively, the differences were statistically significant (t = 0.40,0. 08,0.20;P＜0. 05). The CM,IM and OM average thickness was 194.2,264.9,229.0 μm for boys and 189.3,262.5,231.5 μm for girls respectively. CM and IM thickness of boys were thicker than those in girls(t=0. 15,0. 11;P＜0. 05). The CM, IM and OM average thickness was 196.0,265.2,237.5 μm for White kids,186.0,262.3,236.5 μm for East Asia kids and 193.4,263.7,233.8 μm for Central East kids respectively.The CM and IM thickness of White and Central East children were significantly thicker than East Asia children (t=0. 12,0.15; P＜0.05). There was no difference between these three races in OM thickness(t=0. 16,P=0.6). The IM and OM were thinner with longer axial length (P＜0. 05). The CM,IM and OM thickness was thicker with higher hyperopic degrees (P ＜0. 05). Conclusions Macular thickness was normally distributed in six-year-old children and was significantly affected by gender, race, axial length and refraction status.