Presbyopia: An outstanding and global opportunity for early detection of pre-frailty and frailty states

Depto. de Optometría y VisiónUnidad Docente de Inmunología, Oftalmología y ORLFac. de Óptica y OptometríaTRUEEuropean Union's Horizon 2020 programmeUniversidad Complutense de Madrid (España)Banco Santander (España)pu

Dry Eye Disease and Refractive Corrections

Depto. de Optometría y VisiónFac. de Óptica y OptometríaTRUEpu

Characterisation of the porcine eyeball as an in-vitro model for dry eye

Purpose: To characterise the anatomical parameters of the porcine eye for potentially using it as a laboratory model of dry eye. Methods: Anterior chamber depth and angle, corneal curvature, shortest and longest diameter, endothelial cell density, and pachymetry were measured in sixty freshly enucleated porcine eyeballs. Results: Corneal steepest meridian was 7.85 ± 0.32 mm, corneal flattest meridian was 8.28 ± 0.32 mm, shortest corneal diameter was 12.69 ± 0.58 mm, longest corneal diameter was 14.88 ± 0.66 mm and central corneal ultrasonic pachymetry was 1009 ± 1μm. Anterior chamber angle was 28.83 ± 4.16°, anterior chamber depth was 1.77 ± 0.27 mm, and central corneal thickness measured using OCT was 1248 ± 144μm. Corneal endothelial cell density was 3250 ± 172 cells/mm2. Conclusions: Combining different clinical techniques produced a pool of reproducible data on the porcine eye anatomy, which can be used by researchers to assess the viability of using the porcine eye as an in-vitro/ex-vivo model for dry eye. Due to the similar morphology with the human eye, porcine eyeballs may represent a useful and cost effective model to individually study important key factors in the development of dry eye, such as environmental and mechanical stresses

Objective assessment of the effect of pupil size upon the power distribution of multifocal contact lenses.

AIM: To analytically assess the effect of pupil size upon the refractive power distributions of different designs of multifocal contact lenses. METHODS: Two multifocal contact lenses of center-near design and one multifocal contact lens of center-distance design were used in this study. Their power profiles were measured using the NIMO TR1504 device (LAMBDA-X, Belgium). Based on their power profiles, the power distribution was assessed as a function of pupil size. For the high addition lenses, the resulting refractive power as a function of viewing distance (far, intermediate, and near) and pupil size was also analyzed. RESULTS: The power distribution of the lenses was affected by pupil size differently. One of the lenses showed a significant spread in refractive power distribution, from about -3 D to 0 D. Generally, the power distribution of the lenses expanded as the pupil diameter became greater. The surface of the lens dedicated for each distance varied substantially with the design of the lens. CONCLUSION: In an experimental basis, our results show how the lenses power distribution is affected by the pupil size and underlined the necessity of careful evaluation of the patient's visual needs and the optical properties of a multifocal contact lens for achieving the optimal visual outcome

Fractionation of potentially toxic elements in urban soils from five European cities by means of a harmonised sequential extraction procedure

The revised (four-step) BCR sequential extraction procedure has been applied to fractionate the chromium, copper, iron, manganese, nickel, lead and zinc contents in urban soil samples from public-access areas in five European cities. A preliminary inter-laboratory comparison was conducted and showed that data obtained by different laboratories participating in the study were sufficiently harmonious for comparisons to be made between cities and land types (e.g. parks, roadside, riverbanks, etc.). Analyte recoveries by sequential extraction, with respect to direct aqua regia digestion, were generally acceptable (100 ± 15%). Iron, nickel and, at most sites, chromium were found mainly in association with the residual phase of the soil matrix. Copper was present in the reducible, oxidisable and residual fractions, whilst zinc was found in all four sequential extracts. Manganese was strongly associated with reducible material as, in some cities, was lead. This is of concern because high lead concentrations were present in some soils (>500 mg kg−1) and the potential exists for remobilisation under reducing conditions. As would be expected, extractable metal contents were generally highest in older, more heavily industrialised cities. Copper, lead and zinc showed marked (and often correlated) variations in concentrations between sites within the same city whereas manganese and, especially, iron, did not. No overall relationships were, however, found between analyte concentrations and land use, nor between analyte partitioning and land use

Meibomian Gland Morphology: The Influence of Structural Variations on Gland Function and Ocular Surface Parameters

Purpose: To objectively and quantitatively characterize meibomian gland morphology and to investigate the influence of morphological variations on gland function and ocular surface and tear film parameters. Methods: One hundred fifty subjects were enrolled. The examinations included tear osmolarity, tear meniscus height, bulbar conjunctival hyperemia, noninvasive tear film breakup time, lid margin thickness, foam secretion, meibomian gland expressibility, count of functioning glands, corneal and conjunctival staining, fluorescein breakup time, lid wiper epitheliopathy, and Schirmer test. Patient symptoms were assessed using the Ocular Surface Disease Index questionnaire. Images from noncontact meibography were analyzed using an automated method that objectively estimates dropout area, number of glands, gland length and width, and gland irregularity. Results: Gland irregularity highly correlated with dropout area (r = −0.4, P < 0.001) and showed significant partial correlations with fluorescein breakup time (r = 0.162, P = 0.049) and the Ocular Surface Disease Index questionnaire (r = −0.250, P = 0.002) Subjects with dropout area <32% were divided into 2 groups: high and low irregularity. Gland expressibility was statistically significantly different between the 2 groups (U = 319.5, P = 0.006). In the high irregularity group, gland irregularity correlated with the Schirmer test (r = 0.530, P = 0.001) and corneal fluorescein staining (r = −0.377, P = 0.021). Conclusions: Automated morphological analysis of meibomian gland structure provides additional quantitative and objective information regarding gland morphology. The link between dropout area and gland function is not clear. Assessment of gland irregularity might better predict gland function and its effects on ocular surface and tear film parameters

Long-Term Follow-up of Intrastromal Corneal Ring Segment Implantation in Pediatric Keratoconus

Purpose: To evaluate efficacy, safety, and stability of Ferrara-type intrastromal corneal ring segment (ICRS) implantation for visual rehabilitation in pediatric patients with keratoconus. Methods: This study included patients with keratoconus aged 18 years or younger who had received Ferrara-type ICRS implantation. The uncorrected and corrected distance visual acuities, residual refractive errors, and root mean square for coma-like aberration were recorded preoperatively and at 6 months, 1, 3, and 5 years postoperatively. Results: One hundred eighteen eyes of 88 patients (mean age 16.1 ± 1.89; range 10–18) were studied. All patients were examined at a 6-month follow-up after ICRS implantation, and at the 12-, 36-, and 60-month follow-ups, 97, 71, and 23 eyes were evaluated, respectively. Mean uncorrected distance visual acuity (logarithm of minimum angle of resolution) changed from 0.67 ± 0.37 preoperatively to 0.37 ± 0.30, 6 months after ICRS implantation (P < 0.0001). Mean corrected distance visual acuity increased in turn from 0.19 ± 0.15 to 0.10 ± 0.12 (P < 0.0001). The percentage of eyes with a refractive cylinder ≤2.00 D increased from 30.5% before surgery to 70.3% 6 months later, and the root mean square for corneal coma-like aberration showed a statistically significant decrease (P < 0.001). At the follow-up visits, refractive and visual values remained stable compared with those of the 6-month visit. Conclusions: Our long-term results suggest that Ferrara-type ICRS implantation is a safe, effective, and stable procedure for restoring vision in pediatric patients with keratoconus

Superdiffusive Conduction: AC Conductivity with Correlated Noise

We present evidence of the existence of a superdiffusive regime in systems with correlated disorder for which localization is suppressed. An expression for anomalous electrical conductivity at low frequencies is found by using a generalized Langevin equation whose memory function accounts for the interactions between the carriers. New mechanisms inducing a superdiffusive conductivity are discussed and experimental possibilities for observing that phenomenon in nanotubes and superlattices are presented.Comment: 7 pages, no figure

Surgical Options for the Refractive Correction of Keratoconus: Myth or Reality

Keratoconus provides a decrease of quality of life to the patients who suffer from it. The treatment used as well as the method to correct the refractive error of these patients may influence on the impact of the disease on their quality of life. The purpose of this review is to describe the evidence about the conservative surgical treatment for keratoconus aiming to therapeutic and refractive effect. The visual rehabilitation for keratoconic corneas requires addressing three concerns: halting the ectatic process, improving corneal shape, and minimizing the residual refractive error. Cross-linking can halt the disease progression, intrastromal corneal ring segments can improve the corneal shape and hence the visual quality and reduce the refractive error, PRK can correct mild-moderate refractive error, and intraocular lenses can correct from low to high refractive error associated with keratoconus. Any of these surgical options can be performed alone or combined with the other techniques depending on what the case requires. Although it could be considered that the surgical option for the refracto-therapeutic treatment of the keratoconus is a reality, controlled, randomized studies with larger cohorts and longer follow-up periods are needed to determine which refractive procedure and/or sequence are most suitable for each case

Femto-LASIK after Deep Anterior Lamellar Keratoplasty to Correct Residual Astigmatism: A Long-Term Case Series Study

Purpose: To evaluate the long-term outcomes of femtosecond laser-assisted in situ keratomileusis (Femto-LASIK) to correct residual astigmatism after deep anterior lamellar keratoplasty (DALK). Methods: This retrospective case series study included 10 eyes that underwent Femto-LASIK after a DALK. The refractive error, uncorrected (UDVA) and corrected (CDVA) distance visual acuities, thinnest corneal thickness (TCT), and central corneal thickness (CCT) were registered. The postoperative follow-up ranged between 36 and 60 months. Results: All surgeries were uneventful, with no intra- or postoperative complications. The mean UDVA (Snellen scale) rose from 0.13 ± 0.05 to 0.47 ± 0.15 six months after Femto-LASIK (p < 0.001). All cases experienced a significant improvement in UDVA. None of the eyes lost lines of CDVA, and seven eyes (70%) improved the CDVA compared to preoperative values. The refractive cylinder changed from a preoperative value of −3.88 ± 1.00 D to −0.93 ± 0.39 six months after Femto-LASIK (p < 0.0001). In eight eyes (80%), the UDVA and refractive outcomes remained stable at postoperative follow-up visits. In contrast, one eye experienced a refractive regression over the follow-up. TCT and CCT were stable at the different postoperative follow-up visits. Conclusions: Our findings suggest that Femto-LASIK might safely and effectively corrects residual astigmatism after DALK. Despite these encouraging results, further long-term studies, including a larger number of cases, are required to confirm the safety of the procedure. The refractive stability in eyes with prior RK might be lower than for other DALK indications.Depto. de Optometría y VisiónFac. de Óptica y OptometríaTRUEpu