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Crystalline lens gradient refractive index distribution in the guinea pig.
Ophthalmic and Physiological Optics ( IF 2.9 ) Pub Date : 2020-05-01 , DOI: 10.1111/opo.12667
Alberto de Castro 1 , Eduardo Martinez-Enriquez 1 , Pablo Perez-Merino 1 , Miriam Velasco-Ocaña 1 , Luis Revuelta 2 , Sally McFadden 3 , Susana Marcos 1
Affiliation  

PURPOSE The crystalline lens undergoes morphological and functional changes with age and may also play a role in eye emmetropisation. Both the geometry and the gradient index of refraction (GRIN) distribution contribute to the lens optical properties. We studied the lens GRIN in the guinea pig, a common animal model to study myopia. METHODS Lenses were extracted from guinea pigs (Cavia porcellus) at 18 days of age (n = 4, three monolaterally treated with negative lenses and one untreated) and 39 days of age (n = 4, all untreated). Treated eyes were myopic (-2.07 D on average) and untreated eyes hyperopic (+3.3 D), as revealed using streak retinoscopy in the live and cyclopeged animals. A custom 3D spectral domain optical coherence tomography (OCT) system (λ = 840 nm, Δλ = 50 nm) was used to image the enucleated crystalline lens at two orientations. Custom algorithms were used to estimate the lens shape and GRIN was modelled with four variables that were reconstructed using the OCT data and a minimisation algorithm. Ray tracing was used to calculate the optical power and spherical aberration assuming a homogeneous refractive index or the estimated GRIN. RESULTS Guinea pig lenses exhibited nearly parabolic GRIN profiles. When comparing the two age groups (18- and 39 day-old) there was a significant increase in the central thickness (from 3.61 to 3.74 mm), and in the refractive index of the surface (from 1.362 to 1.366) and the nucleus (from 1.443 to 1.454). The presence of GRIN shifted the spherical aberration (-4.1 µm on average) of the lens towards negative values. CONCLUSIONS The guinea pig lens exhibits a GRIN profile with surface and nucleus refractive indices that increase slightly during the first days of life. GRIN plays a major role in the lens optical properties and should be incorporated into computational guinea pig eye models to study emmetropisation, myopia development and ageing.

中文翻译:

豚鼠的晶状体梯度折射率分布。

目的晶状体会随着年龄的增长而发生形态和功能变化,也可能在眼正视中发挥作用。几何形状和梯度折射率(GRIN)分布都有助于镜片的光学性能。我们研究了豚鼠的晶状体GRIN,这是研究近视的常见动物模型。方法从18天大的豚鼠(豚鼠)中摘除晶状体(n = 4,用负透镜单眼治疗3例,未治疗1例),在39天龄(n = 4,均未治疗)。经治疗的眼睛是近视眼(平均-2.07 D),未经治疗的眼睛是远视眼(+3.3 D),这是通过在活体动物和独眼动物中使用条纹检影法揭示的。定制的3D光谱域光学相干断层扫描(OCT)系统(λ= 840 nm,Δλ= 50 nm)用于在两个方向上成像去核晶状体。使用自定义算法来估计镜片形状,并使用OCT数据和最小化算法重建的四个变量对GRIN进行建模。光线追踪用于计算光焦度和球面像差,假设折射率均匀或估计的GRIN。结果豚鼠晶状体显示出近乎抛物线的GRIN轮廓。比较两个年龄组(18和39天)时,中心厚度(从3.61到3.74毫米)以及表面和折射率(从1.362到1.366)和细胞核(从1.443到1.454)。GRIN的存在将透镜的球差(平均-4.1 µm)移向负值。结论豚鼠晶状体表现出GRIN轮廓,其表面和细胞核折射率在生命的最初几天略有增加。GRIN在晶状体光学特性中起着重要作用,应将其纳入计算性​​豚鼠眼模型中以研究屈光,近视发展和衰老。
更新日期:2020-04-27
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