Validation of the Nuclear Cataract Grading System BCN 10.

PURPOSE: To evaluate a new nuclear cataract grading system which is intended as a surgical guidance system to predict lens hardness before cataract surgery. METHODS: The new BCN 10 grading system consists of frontal and cross-sectional slit-lamp images of human eye lenses, ranging from a completely transparent lens nucleus to a totally black nuclear cataract. Validation was done with 9 observers for 110 cases. Two modalities were applied, and observers were asked to use only whole digits and then half digits for grading. RESULTS: Repeatability with regard to test-retest differences showed a mean limit of agreement of 1.70 for whole digits and 1.32 for half digits. The absolute test-retest difference was close to zero for low as well high degrees of cataracts. Reliability for the entire group of 9 observers yielded an intraclass correlation coefficient which was within the same confidence interval, i.e., 0.991-0.995, for whole digits and half digits. CONCLUSIONS: BCN 10 grading repeatability was not affected by the severity of the cataract. It showed very good repeatability. Repeatability was significantly higher when the observers used half digits compared to whole digits. Reliability was found to be very good as well, independently of the use of whole or half digits.

Protein profiles in cortical and nuclear regions of aged human donor lenses: A confocal Raman microspectroscopic and imaging study.

A combination of Raman spectroscopy, imaging, hierarchical cluster analysis (HCA) and peak ratio analysis was used to analyze protein profiles in the superficial cortex (SC), deep cortex (DC) and nucleus of old human lenses with cortical, nuclear and mixed cataracts. No consistent differences were observed in protein spectra and after cluster analysis between the three locations irrespective of the presence or absence of cortical opacities and/or coloration. A sharp increase (∼15%-∼33%) in protein content from SC to DC, normal for human lenses, was found in 7 lenses. In 4 lenses, characterized by the absence of cortical opacities, the SC has a protein content of ∼35%. A significant increase in the disulfide-to-protein ratio is found only in the SC of the 7 cortical cataracts. No changes were found in sulfhydryl-to-protein ratio. The relative contents of α-helices and ß-sheets increase from SC to nucleus. ß-Sheets are more common in the SC of lenses with cortical cataract. The absence of significant and consistent changes in protein profiles between nucleus and cortex even in cases of severe coloration is not favoring the prevailing concept that ubiquitous protein oxidation is a key factor for age related nuclear (ARN) cataracts. The observations favor the idea that multilamellar bodies or protein aggregates at very low volume densities are responsible for the rise in Mie light scatter as a main cause of ARN cataracts leaving the short-range-order of the fiber cytoplasm largely intact. The absence of significant changes in the protein spectra of the deep cortical opacities, milky white as a result of the presence of vesicle-like features, indicate they are packed with relatively undisturbed crystallins.

Experimental protocols for ex vivo lens stretching tests to investigate the biomechanics of the human accommodation apparatus.

PURPOSE: To explore alternative experimental protocols to investigate the biomechanical behavior of the crystalline lens and zonules using ex vivo stretching. METHODS: Radial stretching tests were conducted on the anterior segment (consisting of lens, zonules, ciliary body, and sclera) of four pairs of presbyopic human donor eyes. A simple mechanical model is used to describe the behavior of the anterior segment when tested in this way. Each pair of samples was initially stretched with the ciliary body intact. One sample was retested after cutting the ciliary body radially, and the other sample was retested after removing the lens. RESULTS: The external forces needed to stretch the sample with the ciliary body intact were significantly greater than for the tests in which the ciliary body had been cut. The forces measured with the ciliary body intact and lens in situ were comparable to the sum of the forces measured in the tests in which the ciliary body had been cut (lens in situ) and the forces measured in the tests on the intact ciliary body with the lens removed. CONCLUSIONS: When stretching tests are conducted on the anterior segment, significant circumferential tensions develop in the ciliary body. This means that the forces applied to the lens and zonules cannot be related directly to the forces applied by the external loading system. If radial cuts are introduced in the ciliary body prior to testing, however, then this difficulty does not arise.

Absence of amyloid-beta in lenses of Alzheimer patients: a confocal Raman microspectroscopic study.

We have compared the protein profiles in plaques and tangles in the hippocampus of post-mortem Alzheimer brains and in opaque and clear regions in the deep cortex of eye lenses of the same donors. From the 7 Alzheimer donors studied, 1 had pronounced bilateral cortical lens opacities, 1 moderate and 5 only minor or no cortical opacities. We focused on beta-sheet levels, a hallmarking property of amyloid-beta, the major protein of plaques and tau protein, the major protein of tangles in Alzheimer brains. Confocal Raman microspectroscopy and imaging was used in combination with hierarchical cluster analysis. Plaques and tangles show high levels of beta-sheets with a beta-sheet to protein ratio of 1.67. This ratio is 1.12 in unaffected brain tissue surrounding the plaques and tangles. In the lenses this ratio is 1.17 independently of the presence or absence of opacities. This major difference in beta-sheet conformation between hippocampus and lens is supported by Congo red and immunostaining of amyloid-beta and tau which were positive for plaques and tangles in the hippocampus but fully negative for the lens irrespective of the presence or absence of opacities. In line with a previous study (Michael et al., 2013) we conclude that cortical lens opacities are not typical for Alzheimer patients and are not hallmarked by accumulation of amyloid-beta, and can thus not be considered as predictors or indicators of Alzheimer disease as claimed by Goldstein et al. (2003).

Absence of beta-amyloid in cortical cataracts of donors with and without Alzheimer's disease.

Eye lenses from human donors with and without Alzheimer's disease (AD) were studied to evaluate the presence of amyloid in cortical cataract. We obtained 39 lenses from 21 postmortem donors with AD and 15 lenses from age-matched controls provided by the Banco de Ojos para Tratamientos de la Ceguera (Barcelona, Spain). For 17 donors, AD was clinically diagnosed by general physicians and for 4 donors the AD diagnosis was neuropathologically confirmed. Of the 21 donors with AD, 6 had pronounced bilateral cortical lens opacities and 15 only minor or no cortical opacities. As controls, 7 donors with pronounced cortical opacities and 8 donors with almost transparent lenses were selected. All lenses were photographed in a dark field stereomicroscope. Histological sections were analyzed using a standard and a more sensitive Congo red protocol, thioflavin staining and beta-amyloid immunohistochemistry. Brain tissue from two donors, one with cerebral amyloid angiopathy and another with advanced AD-related changes and one cornea with lattice dystrophy were used as positive controls for the staining techniques. Thioflavin, standard and modified Congo red staining were positive in the control brain tissues and in the dystrophic cornea. Beta-amyloid immunohistochemistry was positive in the brain tissues but not in the cornea sample. Lenses from control and AD donors were, without exception, negative after Congo red, thioflavin, and beta-amyloid immunohistochemical staining. The results of the positive control tissues correspond well with known observations in AD, amyloid angiopathy and corneas with lattice dystrophy. The absence of staining in AD and control lenses with the techniques employed lead us to conclude that there is no beta-amyloid in lenses from donors with AD or in control cortical cataracts. The inconsistency with previous studies of Goldstein et al. (2003) and Moncaster et al. (2010), both of which demonstrated positive Congo red, thioflavin, and beta-amyloid immunohistochemical staining in AD and Down syndrome lenses, is discussed.

Elastic properties of human lens zonules as a function of age in presbyopes.

PURPOSE: To investigate the elastic properties of human lens zonules as a function of age in presbyopes. METHODS: We studied 16 presbyopic human donor eyes (ages 47-97). Anterior eye sections with crystalline lens, zonules, ciliary body, and sclera were stretched radially. The stretching device consisted of a chamber filled with balanced salt solution and eight radial hooks to hold the anterior eye section. Radial stretching was created with a stepper motor connected to a digital outside micrometer for linear displacement and digital balance for force measurement. Three eye globes were used to test our methodology. For 13 eye globes, the spring constant, elastic modulus of the zonular system, and Young's modulus of the zonules were calculated. RESULTS: We found linear dependence for force-elongation and force-strain relationships at all ages. In young presbyopic eyes (ages 47-60), the Young's modulus of the zonules was 340 mN/mm(2), whereas in older eyes (ages 83-97) it was significantly lower at 270 mN/mm(2). However, the correlation coefficient between Young's modulus and age (47-97 years) was not significant with P = 0.063. CONCLUSIONS: The zonular system in presbyopic eyes was linear elastic, and the Young's modulus of the zonules decreased 20% from presbyopic age to late presbyopic age. However, there was no significant correlation between Young's modulus and age in presbyopes.

Posterior capsule opacification assessment and factors that influence visual quality after posterior capsulotomy.

PURPOSE: To study the correlation between posterior capsule opacification (PCO) and intraocular straylight and visual acuity. DESIGN: Prospective noninterventional study. METHODS: We measured visual acuity (VA), logarithm of minimal angle of resolution (logMAR) and intraocular straylight (C-Quant straylight parameter log[s]) under photopic conditions before and 2 weeks after YAG capsulotomy in 41 patients (53 eyes) from the Centro de Oftalmología Barraquer in Barcelona and the University Eye Clinic, Paracelsus Medical University in Salzburg. Photopic pupil diameter was also measured. To document the level of opacification, pupils were dilated and photographs were taken with a slit lamp, using retroillumination and the reflected light of a wide slit beam at an angle of 45 degrees. PCO was subjectively graded on a scale of 0 to 10 and using the POCOman system. A multiple regression analysis was performed to evaluate factors that influence straylight after capsulotomy. RESULTS: Straylight correlated well with retroillumination and reflected-light PCO scores, whereas VA only correlated with retroillumination. Both VA and straylight improved after capsulotomy. Straylight values varied widely after capsulotomy. Multiple regression analysis showed that older age, large ocular axial length, hydrophobic acrylic intraocular lenses (IOLs), and small capsulotomies are factors that increased intraocular straylight. CONCLUSION: Intraocular straylight is a useful tool in the assessment of PCO. It correlates well with PCO severity scoring methods. When performing a posterior capsulotomy, factors such as age, IOL material, axial length, and capsulotomy size must be taken into consideration, as they influence intraocular straylight.