In the healthy eye, flow of aqueous humor against resistance generates an intraocular pressure (IOP) of approximately 15 mmHg, necessary for the proper shape and optical properties of the globe. The circulating aqueous nourishes the cornea and lens, structures which must…
Introduction The ocular circulation is unique and complex due to the presence of two distinct vascular systems, namely the retinal and uveal systems. The part of this circulation, the one that supplies the fundus of the eye, has the useful…
Introduction Three fundamental visual sensory-motor tasks The neural control of eye movements is organized to optimize performance of three general perceptual tasks. One task is to resolve the visual field while we move either by translation or rotation through space…
Eye motility In principle the eyeball, like any rigid object, has six degrees of freedom: three for rotation, and three for translation. The adult human eyeball is about 24–25mm in diameter, and can rotate about ±50° horizontally, 42° up and…
The extraocular muscles (EOM) are found within the bony orbit. They function in conjugate eye movements, maintenance of primary gaze position, and motor fusion – maintaining corresponding visual elements within the binocular field on corresponding retinal loci. In addition, the…
Introduction The vitreous body makes up approximately 80% of the volume of the eye and thus is the largest single structure of the eye ( Fig. 6.1 ). In the anterior segment of the eye, it is delineated by and…
The lens is a remarkably specialized epithelial tissue that is responsible for fine-tuning the image that is projected on the retina. To perform this function it must be transparent, have a higher refractive index than the medium in which it…
Introduction The outermost, fibrous tunic of the human eye is the cornea and the sclera ( Fig. 4.1A,B ). Both are soft connective tissues designed to provide structural integrity of the globe and to protect the inner components of the…
Introduction “There is no other portion of physiological optics where one finds so many differing and contradictory ideas as concerns the accommodation of the eye where only recently in the most recent time have we actually made observations where previously…
Introduction Myopia, hyperopia and cylinder are refractive errors known as second-order aberrations. These aberrations result in the inability of the eye to focus images appropriately on the retina. In myopia, light rays entering the eye focus anterior to the retina.…