ABSTRACT
PURPOSE: To compare the surface reflections in a pseudophakic model eye with and without a monofocal additional refractive intraocular lens (add-on IOL). SETTING: Department of Ophthalmology, Rudolf-Virchow-Klinikum Glauchau, Glauchau, and Experimental Ophthalmology, Saarland University, Homburg, Germany. DESIGN: Experimental study. METHODS: The Liou and Brennan model eye was used to determine the retinal surface reflections in a pseudophakic model eye with and without an add-on IOL. The crystalline lens of the model eye was replaced by (1) a standard posterior chamber IOL (PC IOL) with a refractive power of 22.0 diopters (D) and (2) a PC IOL and an add-on IOL with refractive powers of 19.0 D and 2.5 D, respectively. To theoretically estimate the impact of the reflected images to visual impression, the signal-to-noise ratio (SNR) was calculated under 2 conditions: without and with straylight and double reflection effects. RESULTS: Compared with the pseudophakic model eye without an add-on IOL, the pseudophakic model eye with an add-on IOL showed no relevant differences in the SNR under both conditions. CONCLUSION: Findings indicate that implantation of monofocal add-on IOLs will not induce relevant additional disturbing glare compared with conventional pseudophakia.
Subject(s)
Glare , Lenses, Intraocular , Models, Biological , Optics and Photonics , Pseudophakia/physiopathology , Refraction, Ocular/physiology , Humans , Lens Implantation, Intraocular , Light , Pseudophakia/surgery , Retina/physiology , Scattering, RadiationABSTRACT
PURPOSE: Visual sensations in patients with blindness and retinal degenerations may be restored by electrical stimulation of retinal neurons with implantable microelectrode arrays. A prospective trial was initiated to evaluate the safety and efficacy of a wireless intraocular retinal implant (EPIRET3) in six volunteers with blindness and RP. METHODS: The implant is a remotely controlled, fully intraocular wireless device consisting of a receiver and a stimulator module. The stimulator is placed on the retinal surface. Data and energy are transmitted via an inductive link from outside the eye to the implant. Surgery included removal of the lens, vitrectomy, and implantation of the EPIRET3 device through a corneal incision. The clinical outcome after implantation and explantation of the device was determined. The implant was removed after 4 weeks, according to the study protocol. RESULTS: Implantation was successful in all six patients. While the anterior part was fixed with transscleral sutures, the stimulating foil was placed onto the posterior pole and fixed with retinal tacks. The implant was well tolerated, causing temporary moderate postoperative inflammation, whereas the position of the implant remained stable until surgical removal. In all cases explantation of the device was performed successfully. Adverse events were a sterile hypopyon effectively treated with steroids and antibiotics in one case and a retinal break in a second case during explantation requiring silicone oil surgery. CONCLUSIONS: The EPIRET3 system can be successfully implanted and explanted in patients with blindness and RP. The surgical steps are feasible, and the postoperative follow-up disclosed an acceptable range of adverse events.
Subject(s)
Blindness/rehabilitation , Electric Stimulation Therapy/instrumentation , Electrodes, Implanted , Microelectrodes , Prosthesis Implantation , Retina/surgery , Retinitis Pigmentosa/rehabilitation , Device Removal , Electric Stimulation , Electroretinography , Feasibility Studies , Fluorescein Angiography , Humans , Prospective Studies , Telecommunications , Visual Acuity/physiology , Visual Field TestsABSTRACT
PURPOSE: To assess corneal asphericity (Q) and evaluate potential factors influencing the shape of the anterior corneal surface. SETTING: Medical Optics Research Group, Institute of Medical Physics, University of Erlangen-Nuremberg, Erlangen, Germany. METHODS: In this cross-sectional consecutive study, 3 topographic measurements were taken. Eyes were grouped by age in years (A:
Subject(s)
Cornea/pathology , Corneal Topography , Refractive Errors/diagnosis , Adolescent , Adult , Age Factors , Aged , Aged, 80 and over , Cross-Sectional Studies , Female , Humans , Male , Middle Aged , Refraction, Ocular/physiology , Refractive Errors/physiopathology , Sex Factors , Young AdultABSTRACT
PURPOSE: To determine the impact of decentration and tilt on the imaging quality of aspheric intraocular lens (IOL) designs in a schematic model eye. SETTING: Institute of Medical Physics, University of Erlangen-Nuremberg, Erlangen, Germany. METHOD: A model eye was used to calculate the impact of misalignment on the imaging quality of 6 IOL designs. The crystalline lens in the model eye was replaced with IOL designs with 22.0 diopters nominal refractive power, and the anterior chamber depth (ACD) was set to the estimated ACD value provided by the manufacturer. The retinal position was optimized for the best image quality. The IOLs were decentered up to +/-1.0 mm and tilted up to +/-5 degrees relative to the line of sight. At each position, the modulation transfer function was recorded with 3.0 mm and 4.5 mm pupil diameters. The results between the IOL designs and those of the phakic model eye were then compared. RESULTS: Aberration-correcting IOLs were very sensitive to decentration and tilt. However, the impact of misalignment depended on IOL design. Aberration-free IOLs showed less sensitivity within a wide range of displacement but provided better results than the spherical IOL. CONCLUSIONS: Overall, modern aspheric IOLs provided better imaging quality than conventional spherical IOL designs. Aberration-free IOLs were less sensitive to decentration and tilt than aberration-correcting IOLs but provided better image quality than spherical IOLs. Aberration-correcting IOLs have the potential to provide diffraction-limited imaging quality when perfectly aligned.
