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Arizona眼睛模型
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infotek
2023-04-27 08:29
Arizona眼睛模型
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人眼光学模型可用来设计眼科用设备,光学系统注定了要与人眼一起使用。本文演示了这样一个模型:Arizona眼睛模型,在Jim Schwiegerling教授的书中有详细描述:《Field Guide to Visual and Ophthalmic Optics》。AZ眼睛模型达到了基于平均临床数据所决定的轴上和轴外像差等级。FRED文件包含了此眼睛模型及几个用来分析它的光源,并包括一个基于想要的屈光度来调整模型的内嵌脚本。
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模型
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模型的定义如表1种所示,由半径、圆锥常数、折射率、阿贝数、到下一面的距离等一系列表面组成。一些参数由屈光度(A)来决定。
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Table 1. AZ眼睛模型的定义
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在FRED中使用0屈光度来创建的,光瞳加在了透镜的前面。材料是创建一个新的材料并选择类型“Model Material”,输入的参数是nd和vd.
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光源
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多个光源定义来分析该模型的不同特性。图1显示了所以的光源和提示信息告诉您他们可以用来做什么。
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图1. 光源和提示信息使用
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除了“Letter F”之外的所有光源的光线位置设定在了孔径光阑位置处,并增加了pre-propagation distance= -8。尽管光线在光瞳处创建,规定的传输方向相对于光线位置在pre-propagation distance之后。这意味着光束沿着Z轴在眼睛的前面以平行光入射,而不是在光瞳处入射。
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在往下看是内置的脚本用来修改屈光度,使其为4(250mm),光源“Letter F”在视网膜处生成一个字母为F的图像。绿色的光线聚焦的非常好而红色和蓝色光线有一点的模糊。使用Positions Spot Diagram分析工具来观察最为合适。
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图2. 字母F光源的设定方法光
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图3. 字母F在视网膜上位置点列图
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视网膜的散射
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在散射文件中,有一个名为“Retina surface”的72%的反射型朗伯散射,它为视网膜的散射提供了一个粗略的近似。为了模拟来自视网膜的散射,改变自定义元件“Eye ball” 下的视网膜的表面从“halt all” 到”Allow All”。并使几何中“plane”可追迹。
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图4. 视网膜朗伯散射设定
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注意在视网膜的表面有散射重点采样规格定义,在“Scatter”标签的底部可获取该信息。“toward pupil”指定散射光朝向光瞳,半角度10度。
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图5. 视网膜重点采样规格设定
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脚本
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内置脚本使用对话框显示屈光度和光瞳直径的数值设置。使用FRED Basic脚本创建和使用对话框非常容易。图6显示了如何获取用户自定义对话框,如下图所示:
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图6. 用户对话框的创建与编辑
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图7. 用户对话框编辑器
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如果“OK”按钮按下,将会核对对话框下面的代码行,如果点击取消则脚本终止。然后输入的参数赋予变量,如果此处是保留为空白,则使用默认值。因此,如果没有值输入并点击“OK”按钮,则脚本是以屈光度为0,光瞳直径为4mm来运行的。
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余下的脚本计算与屈光度有关的所有参数。
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分析
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屈光度为4,光瞳直径为4mm,字母F点在视网膜上所成的像。
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图7. 字母F在视网膜上颜色分析
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脚本代码
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Option Explicit 'Remove this to enable non-dimensioned variables to be used.
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Dim entity As T_ENTITY
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Dim op As T_OPERATION
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Dim mat As T_MODELMATERIAL
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Dim A As Double
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Dim pupilDiam As Double
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Dim eID As Long
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Dim parID As Long
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Dim count As Integer
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Dim taq As Double, Rant As Double, CCant As Double, Rpost As Double, CCpost As Double
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Dim tlens As Double, nlens As Double
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Dim curv As Double, conic As Double
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Dim ok As Long
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Sub Main
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'用户输入对话框
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Begin Dialog UserDialog 320,126,"Input parameters" ' %GRID:10,7,1,1
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TextBox 220,21,40,21,.TextBox1 'default: 0
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Text 20,21,190,21,"Accommodation (in Diopters):",.Text1,1
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OKButton 40,91,90,21
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CancelButton 190,91,90,21
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Text 20,49,190,14,"Pupil diameter (4 mm default):",.Text2,1
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TextBox 220,49,40,21,.TextBox2 'default: 4
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End Dialog
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Dim dlg As UserDialog
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ok = Dialog (dlg)
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If ok=0 Then 'cancel button was pressed
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Print "Execution cancelled."
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End
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End If
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'Assign accommodation and pupil diameter & use defaults if field left empty
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If dlg.TextBox1 = "" Then
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A = 0 'Default accommodation
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Else
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A = CDbl(dlg.TextBox1)
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End If
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If dlg.TextBox2 = "" Then
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pupilDiam = 4 'Default pupil diameter
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Else
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pupilDiam = CDbl(dlg.TextBox2)
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End If
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Print " "
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Print "Accommodation = " & A & " Diopters"
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Print "Pupil Diameter = " & pupilDiam & " mm"
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' Calculate new parameters with accommodation
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taq = 0.55 + 2.97 - 0.04*A 'Aqueous thickness
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Rant = 12.0 - 0.4*A 'Radius of anterior lens
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CCant = -7.518749 + 1.285720*A 'Conic constant of anterior lens
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Rpost = -5.224557 + 0.2*A 'Radius of posterior lens
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CCpost = -1.353971 - 0.431762*A 'Conic constant of posterior lens
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tlens = 3.767 + 0.04*A 'Lens thickness
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nlens = 1.42 + 0.00256*A - 0.00022*A^2 'Lens index of refraction
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'Adjust parameters to account for accommodation
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'*************************************************************************
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'Aqueous thickness (Position of Lens)
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'*************************************************************************
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eID = FindFullName( "Geometry.Arizona Eye.Lens" )
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GetCustomElement eID, entity
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parID = FindFullName( "Geometry.Arizona Eye" )
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' Delete any shift(s) in z
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count = 0
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While GetOperationCount(eID)>count
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GetOperation eID, count, op
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If op.Type="ShiftZ" Then
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DeleteOperation eID,count
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count=count-1
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End If
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count=count+1
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Wend
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'Set new shift in
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op.Type = "ShiftZ"
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op.val1 = taq
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op.parent = parID
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AddOperation eID, op
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Print "Set aqueous humor thickness = " & taq-0.55
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'*************************************************************************
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'Radius and conic constant of anterior lens
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'*************************************************************************
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eID = FindFullName( "Geometry.Arizona Eye.Lens.Anterior" )
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GetConic eID, entity, curv, conic
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SetConic eID, entity, 1/Rant, CCant
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Print "Set anterior lens radius = " & Rant & " and conic constant = " & CCant
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'*************************************************************************
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'Radius and conic constant of posterior lens
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'*************************************************************************
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eID = FindFullName( "Geometry.Arizona Eye.Lens.Posterior" )
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GetConic eID, entity, curv, conic
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SetConic eID, entity, 1/Rpost, CCpost
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Print "Set posterior lens radius = " & Rpost & " and conic constant = " & CCpost
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'*************************************************************************
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'Lens thickness (Position of posterior lens surface)
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'*************************************************************************
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parID = FindFullName( "Geometry.Arizona Eye.Lens" )
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' Delete any z-shift(s)
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count = 0
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While GetOperationCount(eID)>count
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GetOperation eID, count, op
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If op.Type="ShiftZ" Then
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DeleteOperation eID,count
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count=count-1
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End If
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count=count+1
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Wend
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'Set new z-shift
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op.Type = "ShiftZ"
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op.val1 = tlens
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op.parent = parID
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AddOperation eID, op
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Print "Set lens thickness = " & tlens
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'*************************************************************************
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'Lens index of refraction
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eID = FindMaterial( "Lens" )
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GetModelMaterial eID, mat
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mat.Nd = nlens
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SetModelMaterial eID, mat
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Print "Set lens index of refraction = " & nlens
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'*************************************************************************
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'Pupil diameter
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'*************************************************************************
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eID = FindFullName( "Geometry.Arizona Eye.Pupil.Iris" )
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'Adjust pupil diameter (trimming volume inner hole)
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SetTrimVolHole eID, pupilDiam/2, pupilDiam/2, 0, 0, "Cylinder"
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' Adjust pupil location to just in front of the lens
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parID = FindFullName( "Geometry.Arizona Eye" )
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eID = FindFullName( "Geometry.Arizona Eye.Pupil" )
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count = 0
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While GetOperationCount(eID)>count
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GetOperation eID, count, op
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If op.Type="ShiftZ" Then
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DeleteOperation eID,count
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count=count-1
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End If
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count=count+1
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Wend
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op.Type = "ShiftZ"
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op.val1 = taq-0.01
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op.parent = parID
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AddOperation eID, op
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Print "Set pupil diameter = " & pupilDiam
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'Update AZ Eye subassembly Description
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eID = FindFullName( "Geometry.Arizona Eye" )
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GetEntity eID, entity
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entity.Description = "Accommodation = " & A & "D"
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SetEntity eID, entity
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Update
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Print "DONE!"
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End Sub
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如果屈光度是4,光瞳直径是4,则会输出如下数据:
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Accommodation = 4 Diopters
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Pupil Diameter = 4 mm
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Set aqueous humor thickness = 2.81
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Set anterior lens radius = 10.4 and conic constant = -2.375869
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Set posterior lens radius = -4.424557 and conic constant = -3.081019
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Set lens thickness = 3.927
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Set lens index of refraction = 1.42672
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Set pupil diameter = 4
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DONE!
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