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.

Comparison of the impact of nesofilcon A hydrogel contact lens on the ocular surface and the comfort of presbyopic and non-presbyopic wearers

AIM: To assess and compare the impact of a daily disposable contact lens(CL) with high water content on the ocular surface and comfort of the presbyopic and nonpresbyopic population after one day of use. METHODS: Totally 20 presbyopes and 30 non-presbyopes non-contact wearers were fitted with nesofilcon A CLs. CL thickness was measured to assess material stability during daily wear, and ocular surface parameters were also assessed. Optical quality was analyzed for all cases. In addition, CL comfort was rated.RESULTS: No significant differences were found in CL thickness, tear film osmolarity, average tear break-up time, bulbar redness, central corneal thickness, corneal volume, root-mean-square of higher-order aberrations(RMS of HOAs) and vertical and horizontal coma, either as a function of the group or time of use. A significant decrease in tear meniscus height and first break-up of the tear film was found in the presbyopic group(P=0.038; P=0.007 respectively). A decrease in spherical aberration coefficient was found after CL insertion(P=0.031 monofocal CL; P=0.023 low addition multifocal CL; P=0.016 high addition multifocal CL). Multifocal CL were thicker than monofocal CL(P=0.045). Comparison between groups showed more discomfort in presbyopes than non-presbyopes(P=0.003).CONCLUSION: This study evidence that the behavior of the daily disposable CL with high water content seems to be stable during the day of use. Ocular parameters measured during wear show that CL behavior is the same for presbyopes and non-presbyopes, being more uncomfortable for presbyopes.

Accommodation in human eye models:a comparison between the optical designs of Navarro,Arizona and Liou-Brennan

AIM： To simulate and compare accommodation in accommodative and non-accommodative human eye models.METHODS： Ray tracing and optical design program was used. Three eye models were designed and studied： the Navarro, the Arizona and the Liou-Brennan. In order to make the Navarro and Liou-Brennan models to accommodate, specific geometric parameters of the models were altered with values that were chosen from the literature. For the Arizona model, its’ mathematical functions for accommodation were used for the same accommodative demands. The simulation included four distances of accommodation for each model： at infinity, 3, 1 and 0.5 m.The results were diffraction images of a “letter F” for graphical comparison, spot diagrams on the retinal field and Modulation Transfer Function （MTF） graphs.RESULTS：Zernike coefficients for the aberrations, Airy disk diameter, root mean square （RMS） error diameter and total axial length of the model were provided from the program. These were compared between them in all distances. The Navarro model had the smallest axial length change as a simple model. The Arizona did not change its axial length because it is designed to be accommodative. The Liou-Brennan model had different results concerning the aberrations because of the decentration of the pupil. The MTF graphs showed small differences between the models because of the differences in their designs.CONCLUSION： All the three models are able to simulate accommodation with the expected results. There is no model that can be assumed as the best choice. Accommodation can be simulated in non-accommodativemodels and in customized ones.

Seven-year follow-up of posterior chamber phakic intraocular lens with central port design

Background:To assess the clinical outcomes of the Visian Implantable Collamer Lens(ICL)with a central port throughout 7 years of follow-up.Methods:Eighty-four eyes of 52 patients were evaluated over a follow-up period of 7 years after V4c ICL implantation.Uncorrected(UDVA)and corrected(CDVA)distance visual acuities,refraction,intraocular pressure(IOP),endothelial cell density(ECD)and vault were analysed.Results:The mean postoperative UDVA(logMAR)was 0.04±0.11,0.13±0.19 and 0.17±0.23 at 1-,5-and 7-years,respectively(P<0.0001).The mean CDVA(logMAR)remains unchanged throughout a 7-year follow-up period(0.02±0.08 and 0.02±0.08,at 5-and 7-years,respectively,P=0.2).At all follow-up visits,more than 95%of the eyes achieved a CDVA of 20/25 or better and more than 85%a CDVA of 20/20.At the end of the follow-up(7 years),no eye lost more lines of CDVA,56 eyes(66.7%)and 28 eyes(33.3%)gained lines of CDVA.At 7-years,the spherical equivalent was−0.62±0.62 D.No significant increase in IOP(>20 mmHg or an increase higher than 5 mmHg)occurred in any case throughout the 7-year of follow-up.The loss in ECD from the preoperative baseline at the last follow-up visit was 2.6%.No intraoperative or postoperative complications or adverse events occurred during the follow-up period.Conclusions:The outcomes of this study show the long-term viability of the V4c ICL implantation as a surgical option for the correction of myopia.