Ralph Michael

Air-pulse corneal applanation signal curve parameters for the characterisation of keratoconus

Aims To test the use of parameters obtained from the ocular response analyser (ORA) to distinguish between normal and keratoconic eyes, to determine the severity of keratoconus (KC), and to evaluate changes after treatment with cross-linking (CXL) and intrastromal corneal ring (ICR) implantation. Methods In total, 42 parameters were derived from the ORAs applanation response curve. Data on 119 subjects were included in the study. We determined the power of discrimination between control subjects (n=48) and KC patients (stages I and II, n=54) using receiver operating characteristic (ROC) curves. We then tested the correlation between all KC stages (n=71) and the ORA parameters. Finally, we evaluated the changes at 4u2005months after CXL (n=22) and ICR (n=39). Results The ROC curves for 12 parameters showed excellent results; 24 parameters generated moderate results and six parameters generated poor results. The correlations between the KC stages and 14 parameters were significant, with good to moderate results. The corneal resistance factor and the area under the second peak of the signal curve produced the best results in distinguishing between normal and KC eyes. Two parameters after CXL (p2area and time1) and six parameters after ICR implantation (aplhf, uslope11, w11, path11, time1 and deltatime) showed significant differences with respect to the preoperative conditions. Conclusion Most of the new waveform parameters demonstrated good ability to distinguish between KC and normal eyes. The changes in the parameter values after CXL and ICR treatments were smaller than expected.

Impact of Clinical Factors on the Long-Term Functional and Anatomic Outcomes of Osteo-odonto-keratoprosthesis and Tibial Bone Keratoprosthesis

PURPOSEnTo report the long-term functional and anatomic outcomes of osteo-odonto-keratoprosthesis and tibial bone keratoprosthesis; to analyze the influence of clinical factors, such as surgical technique, primary diagnosis, age, and postoperative complications, on the final outcome.nnnDESIGNnRetrospective cohort study.nnnMETHODSnsetting: Centro de Oftalmología Barraquer, between 1974 and 2005.nnnPARTICIPANTSnTwo hundred twenty-seven patients. intervention: Biological keratoprosthesis using osteo-odonto-keratoprosthesis or tibial bone keratoprosthesis. main outcome measures: Functional survival with success defined as best-corrected visual acuity ≥0.05; anatomic survival with success defined as retention of the keratoprosthesis lamina.nnnRESULTSnOsteo-odonto-keratoprosthesis and tibial bone keratoprosthesis have comparable anatomic survival at 5 and 10 years of follow-up, but osteo-odonto-keratoprosthesis has a significantly better functional success than tibial bone keratoprosthesis at the same time periods. Among the primary diagnoses, Stevens-Johnson syndrome, chemical burn, and trachoma have generally good functional and anatomic outcomes and the least favorable prognosis is for ocular cicatricial pemphigoid. Younger patients fared better than those in older age groups. The most frequent complications were extrusion (28%), retinal detachment (16%), and uncontrolled glaucoma (11%). The glaucoma group had the best anatomic success but the worst functional results, only exceeded by the retinal detachment group in terms of functional outcome.nnnCONCLUSIONnClinical factors, such as surgical technique, primary diagnosis, age, and postoperative complications, can affect the long-term anatomic and functional successes of biological keratoprosthesis. Knowledge about the impact of each of these factors on survival can help surgeons determine the best approach in every particular case.

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

Eye lenses from human donors with and without Alzheimers 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 etxa0al. (2003) and Moncaster etxa0al. (2010), both of which demonstrated positive Congo red, thioflavin, and beta-amyloid immunohistochemical staining in AD and Down syndrome lenses, is discussed.

Anatomical survival and visual prognosis of Boston type I keratoprosthesis in challenging cases

PurposeTo describe the outcome of patients with Boston type 1 keratoprosthesis, with regard to anatomical and visual success.MethodsRetrospective case series of patients who underwent Boston type I keratoprosthesis surgery at the Centro de Oftalmología Barraquer in Barcelona and at the University Eye Clinic in Salzburg between May 2006 and December 2011. Sixty-seven eyes were included. Anatomical success, visual acuity, and complication rate were evaluated and correlated with the initial diagnosis.ResultsThe mean age of patients was 54xa0years; 62xa0% were male and 38xa0% were female. Eleven patients underwent Type I Boston Kpro implantation as a primary procedure, while the other 52 patients had previous graft failure. The most frequent diagnoses were autoimmune diseases (16 eyes), severe chemical or thermal burn (12 eyes), leukoma post-infectious keratitis (seven eyes) and bullous keratopathy (six eyes). The mean follow-up time was 26xa0months. Retention of the prosthesis was achieved in 95xa0% at 1xa0year and 78xa0% at 4.5xa0years. Two eyes suffered extrusion of the KPro, six underwent successful exchange of the prosthesis either due to infection, necrosis or extrusion, three KPro’s had to be explantated, and two eyes ended up in enucleation due to panophthalmitis. The outcome of the autoimmune cases was similar to the group with “other diagnoses” and better than those with chemical/thermal burn. The most frequent complication was development of a retroprosthetic membrane in 21 eyes (34xa0%). Visual acuity (LogMAR) in the chemical/thermal burn group was 2.30 preoperatively, 0.69 at 1xa0year, 0.52 at 2xa0years and 0.39 at 3xa0years; in the autoimmune group visual acuity was 2.3 preoperatively, 0.65 at 1xa0year, 0.15 at 2xa0years, and 1.5 at 3xa0years.ConclusionsBoston type 1 keratoprosthesis is a viable option for patients with repeated graft failure, even for those with challenging diagnoses such as ocular burns and autoimmune syndromes.

Posterior Capsule Opacification Assessment and Factors That Influence Visual Quality After Posterior Capsulotomy

PURPOSEnTo study the correlation between posterior capsule opacification (PCO) and intraocular straylight and visual acuity.nnnDESIGNnProspective noninterventional study.nnnMETHODSnWe 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.nnnRESULTSnStraylight 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.nnnCONCLUSIONnIntraocular 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.

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 etxa0al., 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 etxa0al. (2003).

Iris color and visual functions

BackgroundThe aim of this study was to evaluate if iris color is associated with differences in visual functions such as intraocular straylight (IOSL), contrast sensitivity (CS), or best-corrected visual acuity (BCVA).MethodsIn this retrospective cohort study, which is a subgroup analysis of a large prospective trial about visual impairments in European car drivers, we included 853 persons between 20 and 80xa0years of age and without a history of ocular surgery or any eye disease including cataract. Subjects participated in an ophthalmological examination, grading of lens opacity, and the measurement of visual functions such as IOSL, CS, and BCVA. Dependent on iris color, participants were divided into four groups: light-blue, blue-grey, green-hazel, and brown.ResultsIndependent of age, IOSL was significantly (all p valuesu2009<u20090.0001, Fisher’s LSD test) higher in participants with light-blue colored iris (1.14 log(IOSL) [95xa0% CI: 1.11–1.17]) compared to participants with blue-grey (1.07 log(IOSL) [95xa0% CI: 1.05–1.09]), green-hazel (1.06 log(IOSL) [95xa0% CI: 1.04–1.08]) or brown (1.06 log(IOSL) [95xa0% CI: 1.04–1.08]) iris color. CS was also lower in participants with light-blue pigmented irises (1.60 log(CS) [95xa0% CI: 1.58–1.62]) than in the other groups, but statistically significant (pu2009=u20090.013, Fisher’s LSD test) only compared to brown iris color. For BCVA we could not found any difference between the four groups.ConclusionsWe could show in this study that iris color has a significant impact on IOSL and to a lower degree on CS, but not on BCVA. Persons with light-blue iris color who showed significantly higher IOSL values therefore may experience disability glare in daily situations such as driving at night more often than others.

Refractive index of lens fiber membranes in different parts of the crystalline lens

Purpose: Local variations in refractive index are an important physical cause of light scattering in the lens. The goal of this study was to further add to the understanding of the process of light propagation in the lens by directly measuring local variations in refractive index by phase contrast microscopy. Methods: Refractive index was estimated by immersion refractometry. Cryo-sections of quick frozen human donor lenses were embedded in a graded series of bovine serum albumin solutions, and in immersion oil. Results: Superficial cortical fiber membranes proved to have a refractive index considerably above values given for cytoplasm at the same location. Nuclear fiber membranes have a refractive index of the same order as given in the literature for nuclear fiber cytoplasm. Conclusion: The large difference in refractive index between fiber membranes and cytoplasm in the lens cortex may be important for optical function and transparency of the lens. Support: Marie Curie Fellowship of the European Community program Quality of Life (QLK6-CT-1999-51159).

Neural contrast sensitivity calculated from measured total contrast sensitivity and modulation transfer function

Purpose:u2002 To test the feasibility of calculating neural contrast sensitivity function (neural CSF) from conventionally measured total contrast sensitivity function (total CSF) and measured modulation transfer function (MTF). Neural CSF considers the retina and the brain, whereas total CSF considers the optical eye media, the retina and the brain together.

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

PURPOSEnTo investigate the elastic properties of human lens zonules as a function of age in presbyopes.nnnMETHODSnWe 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.nnnRESULTSnWe 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.nnnCONCLUSIONSnThe 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.