Gustavo A. Montenegro

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.

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 Youngs 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 Youngs 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 Youngs 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 Youngs modulus of the zonules decreased 20% from presbyopic age to late presbyopic age. However, there was no significant correlation between Youngs modulus and age in presbyopes.

Wedge resection for high astigmatism after penetrating keratoplasty for keratoconus: refractive and histopathologic changes.

Purpose: To analyze the refractive, topographic, keratometric changes and the histopathologic findings after wedge resection to correct high astigmatism after penetrating keratoplasty for keratoconus. Materials and Methods: A retrospective study was done analyzing the following parameters preoperatively and at 1, 3, and 5 years postoperatively: uncorrected visual acuity, best-corrected visual acuity, and spherical equivalent and refractive, topographic, and keratometric cylinder measures. We also studied the efficacy and safety indices, as well as the histopathologic findings of tissues submitted for pathology. Results: A total of 22 eyes of 21 patients who underwent wedge resection in the host corneal tissue for correcting high irregular astigmatism after penetrating keratoplasty for keratoconus were included in the study. Mean follow-up time from penetrating keratoplasty to wedge resection was 18 years, whereas the mean follow-up time after wedge resection was 39.04 months (range, 12-280 months). The mean preoperative refractive, topographic, and keratometric cylinders were 11.58 ± 3.52 diopters (D) (range, 4.5-20 D), 10.88 ± 5.03 D (range, 2.58-21.3 D), and 11.29 ± 4.33 D (range, 4.50-18 D), respectively. The mean postoperative refractive, topographic, and keratometric cylinders at 3 years were 4.91 ± 2.48 D (range, 0.50-10 D), 3.38 ± 2.10 D (range, 2.05-7.1 D), and 5.31 ± 2.90 D (range, 0.50-9 D), respectively. The percentage of correction at 3 years of follow up was 57.5% for refractive cylinder, 68.97% for topographic cylinder, and 53.01% for keratometric cylinder. All refractive, topographic, and keratometric data showed the lowest degree of astigmatism at 3 years postoperatively, with a tendency toward regression at 5 years postoperatively. Safety index was 1.0, whereas efficacy index was 0.49. All histopathologic sections of resected tissue were consistent with keratoconus progression in the host peripheral cornea. Conclusion: Wedge resection is a safe and moderately effective procedure in the correction of high astigmatism after penetrating keratoplasty for keratoconus. Histopathologic changes confirm a true late progression of the disease in the host cornea. Keratoconus may be a disease that affects the entire cornea, and surgical resection does not cure the disease.

Variation of straylight between contra lateral eyes - results from 1017 healthy subjects.

to the caruncle, and in one case, to the plica. The remainder developed in the nasal conjunctiva. All tumours were of salmon-coloured appearance. The clinical appearance varied between cystlike (n = 2), nodular (n = 1) and pemphigoid-like (n = 1) lesions, as well as lesions mimicking the diffuse conjunctival thickening of a lymphoma (n = 3) were observed. In two patients, the tumour followed the manifestation of a conjunctival lymphoma in the fellow eye. Follow-up (1–11 years) was uneventful in all patients with no recurrence or transformation into a true lymphoma. In none of the investigated specimens either Chlamydia species or EBV were detected. In our cohort, RLH was presented as a mostly unilateral circumscribed lesion with varying clinical morphology and an apparent preference for the nasal conjunctiva ⁄ caruncle. Six of seven patients were younger than 31 years, which is different from the average age reported in the literature. RLH has – similar to malignant lymphoma – been reported to affect adults typically in the 5th through 7th decade (Sigelman & Jakobiec 1978; Coupland et al. 1998). The proposed aetiology of RLH as a reaction to antigen hyperstimulation (Sigelman & Jakobiec 1978), however, might account for a more likely occurrence in children and young adults, as well as for the nasal location. Two of our patients with a non-Hodgkin lymphoma and subsequent treatment with radiation therapy of the affected eye developed RLH in the fellow eye. Whether the occurrence of RLH is connected to radiation therapy or lymphoma remains unclear. There is still an ongoing debate on a possible association between OAL and C. psittaci (Ferreri et al. 2004; Decaudin et al. 2008). Differences in the prevalence of C. psittaci infection in various geographical regions and technical differences in the application of the assays have to be considered (Decaudin et al. 2008). However, from our results, we would not recommend a change in treatment strategy unless the association with an infectious agent can be unequivocally proven for single cases. Especially, in young adults and children, RLH should be considered in the differential diagnosis of salmoncoloured lesion of the ocular surface, even if cyst like and located at unusual sites such as the caruncle (Herwig et al. 2008).

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 β-sheets increase from SC to nucleus. β-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.

Contents Vol. 57, 2017

13 SIRCOVA-OFTARED Joined Congress Abstracts Valencia (Spain), June 30 – July 2, 2016 (online only) E-Mail karger@karger.com www.karger.com

Equatorial wrinkles in the human lens capsule

Abstract Equatorial wrinkles, or crenations, have been previously observed around the equator in coronal images of the human ocular lens. However, wrinkles are typically not apparent when the lens is viewed from saggital directions. In the current paper, the existence and geometry of these wrinkles is shown to be consistent with a mechanical model of the isolated lens, in which the capsule is held in a state of residual tension by a spatially uniform internal pressure. The occurrence of equatorial wrinkles is therefore seen to be a mechanical consequence of the spheroidal shape of the lens capsule and an excess intralenticular pressure. New observations are made, on post mortem lenses, on the geometric arrangement of these equatorial wrinkles. These observations indicate a well‐defined pattern in which wrinkles exists along meridional lines in the equatorial regions of the lens. A preliminary ‘puncture test’ is used to demonstrate that the residual stresses within the capsule in the equatorial region of the lens are broadly consistent with the proposed mechanical model of the lens capsule. It is suggested that the presence of equatorial wrinkles may have an influence on the mechanical performance of the capsule during the accommodation process. HighlightsObservations on isolated human lenses indicate the existence of capsule wrinkling near to the equator.A new experimental system is presented to quantify the geometric arrangements of equatorial wrinkles in the human lens.A mechanical model of the lens is use to support the observations presented in the paper.

Intraocular stray light compared with subjective lens grading scores in normal and cataractous eyes

A European project studying the prevalence of visual function impairment in European drivers (2422 subjects) showed that intraocular stray light correlates with cataract grading scores. Measured intraocular stray light increases continuously with cataract severity, as estimated by the mean of the LOCS score (average of nuclear colour, nuclear opacity, cortical opacity and posterior subcapsular scores divided by four). Mean intraocular stray light for the lowest LOCS score (0.025) is about 1.00 log[s] and with a LOCS score for severe cataract (> 0.75) about 1.44 log[s]. This corresponds to a more than threefold increase in stray light. The lowest levels of intraocular stray light are found in nuclear cataracts (1.19 log[s]), followed by cortical (1.20 log[s]) and posterior subcapsular cataract (1.23 log[s]). Mixed nuclear and cortical cataracts have a mean of 1.30 log[s] and mixed nuclear, cortical and posterior subcapsular cataract a mean of 1.35 log[s]. A study in patients before lens surgery at the Centro de Oftalmologia Barraquer (218 eyes) did not showed a significant relation between lens grading scores and intraocular stray light values. About 90% had nuclear cataracts with low to medium severity (LOCS score between 0.2 and 0.6) with a mean stray light of 1.46 log[s]. A few cases had cortical cataracts reaching inside the pupillary area or very minor posterior subcapsular cataracts. All studies showed a large variation of intraocular stray light values for similar cataract scores, ranging from 1.00 to 2.00 log[s]. This probably reflects the theoretical expected important discrepancy between the backscattered light (lens grading) and forward scattered light (measured intraocular stray light).