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Adaptive optics has emerged as an empowering technology for retinal imaging with cellular resolution. This technology holds potential for non-invasive detection and diagnoses of the most common eye diseases such as glaucoma, diabetic retinopathy and age-related macular degeneration (AMD). However, the cost and complexity of adaptive optics ophthalmoscopes currently impede its clinical use. A scanning laser ophthalmoscope with phase plate has the potential to establish adaptive optics in a clinical application by simplifying its incorporation in the prevailing systems. Phase plates can correct aberrations down to diffraction limit and can be easily incorporated into ophthalmoscopes to improve the retinal image quality.

More than 25 years ago, the first in vivo measurement of the eye’s wave aberration was demonstrated at the University of Heidelberg, using the Shack-Hartmann method. The continuous measurement of ocular aberrations paved the way to employ adaptive optics for the correction of ocular aberrations in ophthalmoscopy. Various new diagnostic and treatment modalities have since been successfully introduced, e.g. adaptive optics scanning laser ophthalmoscopy (AO-SLO), adaptive optics optical coherence tomography (AO-OCT) and adaptive optics two-photon ophthalmoscopy (AO-TPO). Employing adaptive optics techniques, the limits of human vision can be assessed. With the development of wavefront-guided laser refractive surgery, the quest for optically perfect vision is being pursued over the last 20 years.

Cataract surgeons are in constant pursuit to achieve optimal visual outcomes for their patients. Therefore, numerous technologies and techniques have emerged, most of which are designed to assist the surgeon preoperatively and intraoperatively. The in vivo modification is achieved by creating a lens within an existing IOL using a femtosecond laser. The lens within the lens is created by altering the hydrophilicity of an existing and standard IOL in certain designated areas. The changes created by the perfect lens technology alter the IOL’s refractive outcome and enable the surgeon to create the patient’s desired vision in a simple postoperative in-office procedure.

A three-sided pyramid prism is used as a wavefront sensor in non-modulating mode with an artificial neural network (NN) as a control unit in an adaptive optical setup. The NN is composed of a convolution network for feature extraction from the pyramid signal and a three-layer feed-forward back-propagation net. The network is trained with over 15,000 examples of signal–wavefront pairs. Presenting wavefronts of 6 mm pupil diameter and a RMS error of under 200 nm to the adaptive optical system with the trained network, it can correct the aberrations within three loops to a wavefront with

In this work, a new approach, a method using artificial neural networks was applied to reconstruct the wavefront. First, the optimal structure of neural networks was found. Then, the networks were trained on both noise-free and noisy spot patterns. The results of the wavefront reconstruction with artificial neural networks were compared to those obtained through the least square fit and singular value decomposition method.

We describe what we believe to be the first wave-front measurements of the human eye at a sampling rate of 300 Hz with a custom Hartmann–Shack wave-front sensor that uses complementary metal-oxide semiconductor (CMOS) technology. This sensor has been developed to replace standard charge-coupled device (CCD) cameras and the slow software image processing that is normally used to reconstruct the wave front from the focal-plane image of a lenslet array. We describe the sensor’s principle of operation and introduce the performance with static wave fronts. The system has been used to measure human-eye wave-front aberrations with a bandwidth of 300 Hz, which is approximately an order of magnitude faster than with standard software-based solutions. Finally, we discuss the measured data and consider further improvements to the system.

We describe existing concepts for CMOS3-based Hartmann-Shack wavefront sensors and propose the next step for a further miniaturization of adaptive optics by integrating the modal wavefront reconstruction on chip. In conventional Hartmann-Shack wavefront sensing a CCD4 camera is placed on the focal plane of a microlens array. The spot pattern in the focal plane is captured, analyzed by image processing and the wavefront is often decomposed into orthogonal modes, usually expressed in coe.cients of Zernike polynomials. The single-chip modal wavefront reconstructor would include all these processing steps in a single chip. We propose to use already existing CMOS-based wavefront sensor concepts and add a hardware arti.cial neural network for modal wavefront reconstruction.

Wavefront technology was originally developed for the improvement of star images in optical astronomy. In 1978, this technology was for the first time applied to ophthalmology. At the University of Heidelberg, Germany, a closed loop adaptive optical system was designed to compensate for optical aberrations of the human eye. In the meantime, superresolution in retinal imaging has been achieved, providing detailed information on photoreceptors, small blood vessels, and nerve fiber structure in the human eye in vivo. Recently, new wavefront technology has been developed for the assessment of the human eye and it is now possible to apply a custom treatment to the eye, using the excimer laser. An adaptive optical closed loop system has been devised for preoperative simulation of refractive outcomes of aberration-free refractive surgical procedures. Treatment of a patient’s entire wavefront error has been demonstrated to improve the patient’s visual acuity beyond best spectacle-corrected vision.

The optical errors caused by the elements of the optical apparatus of the eye, as the cornea or the lens, strongly degrade the image on the retina. These errors are lager for larger pupil sizes.

Measurements of the wavefront of light reflected from the retina of the human eye can be used to determine optical aberrations of the human eye for large pupils. An instrument based on the Hartmann-Shack principle was developed. The wavefront is refracted by a microlens array and detected by a CCD camera. In first clinical studies human volunteer eyes and preoperative and postoperative refractive surgical patient eyes have been examined. An adaptive optical closed loop system has been devised for preoperative simulation of refractive outcomes of aberration free refractive surgical procedures. [J Refract Surg 2000; 16: S608-S6101

Changes in parapapillary retina height may be an early indicator of glaucomatous tissue damage. The subject of this study is the development of an automatic computer analysis for the height variations of the parapapillary retina obtained from simultaneously taken pairs of stereophotographs of optic nerve heads. The exact evaluation of stereo photographs is, so far, processed manually in the USA (Takamoto, Boston) in a timeconsuming procedure. An automatic analysis can be considered as an essential improvement in glaucoma diagnosis.© (1994) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

This paper presents the measurement of the wave aberrations of human eyes with a Hartmann-Shack Sensor (HSS), used in a system for active optical depth resolution improvement of the Laser Tomographic Scanner(LTS). A least-squares algorithm of modal wavefront estimation from the tested derivatives is described. The noise propagation of this algorithm is examined. And the experimental results of tested living eyes are presented.© (1991) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

For real-time analysis of light microscopic images by using structural features we have developed a special image processing system. The major components of the system are a parallel multi--microprocessor system, an image buffer, a stepping motor driver module for x-, y-, and z-movement of the microscope, a video processing module and a binary image module. The two latter modules are special hardware to generate structural parameters of the video image in real-time. The parameters are derived from the number and optical density of individual objects within each image line. An object is recognized if its optical density exceeds a predefined threshold and its size falls into a programmable interval. We have applied this system to objectively evaluate histological changes occuring in neoplasias treated preoperatively with chemotherapy. The result is an automated mapping of residual tumor lesions for each specimen. These maps are used to define chemotherapy effects. It should be emphasized that because of its flexibility, the system described can be used more generally to analyse structures of histological images.

A microprocessor controlled photo-thermoplastic device has been developed for the real-time recording of holographic filters in a hybrid digital-optical data processing system. It is possible to position the filters with an accuracy of 0,2 µm.© (1981) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

With optically generated component filters a binary recognition of 2-D objects is possible. The correlation signals of the filters are processed by a digital computer system to achieve a classification by signal intensity and shape. The computer also controlls the filtergeneration and carries out the recognition.© (1981) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.