View clinical trials related to Contrast Sensitivity.
Filter by:Contrast sensitivity (CS) and tear film (TF) changes are noted in late postoperative period after upper blepharoplasty (UB), while the same was rarely investigated in the early postoperative period. The reason for aforementioned improvement of vision quality is unclear. Suggested explanations include changes in higher-order aberrations, elimination of the overlay effect created by excess skin on the upper eyelids and/or eyelashes directed toward the eyelid, or changes in corneal topography (CT) and keratometry. Furthermore, there is no consensus on the best technique for UB. Due not only to different surgical techniques, but also to different methods of measuring the tear film quality, it is very difficult to quantify the aforementioned studies. While changes in tear volume parameters and changes in tear film (TF) rupture have been investigated in detail, changes in the lipid layer have rarely been investigated. According to previous studies, there are different findings about changes in CT after UB. The aim of the research is to determine whether there are anatomical (CT) and functional (TF and CS) changes in subjects with functional dermatochalasis before the procedure and in a month-long postoperative period. The research is conducted on examinees diagnosed by clinical examination with functional dermatochalasis with the exclusion of examinees with ocular or systemic conditions affecting TF, best corrected visual acuity or CT. Detailed medical history and ophthalmologic examination will be performed with grading of the external appearance of the upper eyelids. All diseases and conditions that can lead to changes in CS, TF or corneal defects will be noted. Preoperatively all subjects will have CS recorded in photopic conditions, TF analysis and CT (Keratograph 5M, OCULUS Optikgeraete GmbH, Wetzlar, Germany). UB will be performed in the operating room at the UED. At first (seven days postoperatively) and second (one month postoperative) check-up a CS check will be performed at the UED and TF analysis and CT at Lens LTD.
To compare the efficacy to different profiles, direct head-to-head studies had been conducted. In one previous review study revealed that TG LASIK provided patient with better uncorrected visual acuity (UCVA) than WFO LASIK and WFG LASIK. In recent previous contralateral eye studies also showed that TG LASIK induced less postoperative higher-order aberration than WFO LASIK. However, these studies included only low-to-moderate myopia patients, for patients with high myopia (spherical equivalent > 6D), the effect of TG LASIK comparing with WFO LASIK had not been reported before. The aim of our study is to analyze and compare the visual performance of TG LASIK and WFO LASIK in high myopia and low-to-moderate myopia patients, , particularly UCVA, corrected distance visual acuity (CDVA), contrast sensitivity (CS), and wavefront aberration.
Human visual acuity and contrast sensitivity are highly dependent on various different parameters. Each should be optimized for perfect visual performance. However, in real life our eyes lack such parameters, which might lead to unsatisfying results even after spectacle correction or contact lenses. A promising approach would be to design intra ocular lenses (IOL), which are implanted into the eye for example in the course of cataract extraction and are able to compensate for the human eyes' aberrations. For example cutoff frequency, edge-sharpness or specific contrast for selected structure sizes would need to be considered. Since, an aberration free optical system is almost impossible and since the impact of each single parameter is not yet known, IOL design parameters would have to be chosen very carefully. Furthermore, image quality of IOLs still is tested ex vivo by ray tracing for example, but this does not guarantee perfect function after implantation, as our visual system has complex image precessing units form the retina to the brain. The present study picks one of these parameters and seeks to assess its impact on visual quality in-vivo. By subjectively grading different images with objective changes to image quality by variations of the modulation transfer function (MTF), the potential influence and thus on our subjective visual impression shall be assessed.
The study evaluates contrast sensitivity in older children following surgery for lamellar and posterior subcapsular cataracts. Often, pediatric surgeons tend to delay surgery in these children who present beyond the amblyogenic age group. These cataracts are often compatible with reasonable visual acuity and therefore some surgeons prefer to wait for surgery, whereas others tend to operate. The study evaluates improvement in contrast sensitivity at different spatial frequencies following cataract surgery for lamellar and posterior subcapsular cataracts in older children.
Age related cataracts are responsible for about 51 percent of blindness worldwide and according to the WHO affect about 20 million people, according to the WH . As cataract surgery is firstline treatment in the western world, there is a constant attempt to improve artificial intraocular lenes (IOL). As for this study, the investigators seek to compare four different IOL designs in in a psychophysiological setting, allowing to assess the impact of these IOLs on vision and psychological processing of visual information. As these IOLs also have downsides, such as reduced light intensity or image alterations, the subjective preference and overall impression shall be investigated. The healthy subjects look through a stable spectacle frame mounted onto a table, which enables the investigator to insert the different IOLs. This would allow subjective testing of IOLs before surgery.