Introduction to Ophthalmology Ophthalmology 160.01 Fall 2019 Tuesdays 12:10-1 pm Location: Library, Room CL220&223 University of California, San Francisco WELCOME OBJECTIVES This is a 1-unit elective designed to provide 1st and 2nd year medical students with - General understanding of eye anatomy - Knowledge of the basic components of the eye exam - Recognition of various pathological processes that impact vision - Appreciation of the clinical and surgical duties of an ophthalmologist INFORMATION This elective is composed of 11 lunchtime didactic sessions. There is no required reading, but in this packet you will find some background information on topics covered in the lectures. You also have access to Vaughan & Asbury's General Ophthalmology online through the UCSF library. AGENDA 9/10 Introduction to Ophthalmology Neeti Parikh, MD CL220&223 9/17 Oculoplastics Robert Kersten, MD CL220&223 9/24 Ocular Effects of Systemic Processes Gerami Seitzman, MD CL220&223 10/01 Refractive Surgery Stephen McLeod, MD CL220&223 10/08 Comprehensive Ophthalmology Saras Ramanathan, MD CL220&223 10/15 BREAK- AAO 10/22 The Role of the Microbiome in Eye Disease Bryan Winn, MD CL220&223 10/29 Retinal imaging in patients with hereditary retinal degenerations Jacque Duncan, MD CL220&223 11/05 Pediatric Ophthalmology Maanasa Indaram, MD CL220&223 11/12 Understanding Glaucoma from a Retina Circuit Perspective Yvonne Ou, MD CL220&223 11/19 11/26 Break - Thanksgiving 12/03 Retina/Innovation/Research Daniel Schwartz, MD CL220&223 CONTACT Course Director Course Coordinator Dr. Neeti Parikh Shelle Libberton [email protected] [email protected] ATTENDANCE Two absences are permitted. Please let Shelle Libberton know if you are planning to be absent or have missed a class. See the UCSF Vision and Ophthalmology Interest Group website for more information: Please feel free to contact the coordinator first with any questions or concerns. **don’t forget to officially sign up for the class** https://sites.google.com/site/ucsfpreophthalmology/ Eye Anatomy & Physiology When looking into someone's eyes, we can easily see several structures: - A black-looking aperture, the pupil, that allows light to enter the eye. - A colored circular muscle, the iris, which controls the size of the pupil so that more or less light, depending on conditions, is allowed to enter the eye - A transparent external surface, the cornea, that covers both the pupil and the iris. This is the first and most powerful lens of the optical system of the eye and allows, together with the crystalline lens the production of a sharp image at the retina. - The "white of the eye", the sclera, which forms part of the supporting wall of the eyeball is continuous with the cornea and the dura of the central nervous system. The eye has three chambers of fluid: Anterior chamber (between cornea and iris), Posterior chamber (between iris, zonule fibers and lens) and the Vitreous chamber (between the lens and the retina). The first two chambers are filled with aqueous humor whereas the vitreous chamber is filled with a more viscous fluid, the vitreous humor. The sagittal section of the eye also reveals the lens which is a transparent body located behind the iris. The lens is suspended by ligaments (called zonule fibers) attached to the anterior portion of the ciliary body. The contraction or relaxation of these ligaments as a consequence of ciliary muscle actions, changes the shape of the lens, a process called accommodation that allows us to form a sharp image on the retina. Light rays are focussed through the transparent cornea and lens upon the retina. The central point for image focus (the visual axis) in the human retina is the fovea. Here a maximally focussed image initiates resolution of the finest detail and direct transmission of that detail to the brain for the higher operations needed for perception. Slightly more nasally than the visual axis is the optic axis projecting closer to the optic nerve head. The optic axis is the longest sagittal distance between the front or vertex of the corna and the furthest posterior part of the eyeball. It is about the optic axis that the eye is rotated by the eye muscles. Inserted into the sclera are three pairs of muscles (6 muscles altogether). Two pairs are rectus muscles running straight to the bony orbit of the skull orthogonal to each other (the superior rectus, the inferior rectus, the lateral rectus and the medial rectus muscles). A further pair of muscles, the oblique muscles (superior oblique and inferior oblique) are angled as the name implies obliquely. These muscles, named extraocular muscles rotate the eyeball in the orbits and allow the image to be focussed at all times on the fovea of central retina. The retina is a part of the central nervous system and an ideal region of the vertebrate brain to study, because like other regions of the central nervous system, it derives from the neural tube. The retina is formed during development of the embryo from optic vesicles outpouching from two sides of the developing neural tube. The primordial optic vesicles fold back in upon themselves to form the optic cup with the inside of the cup becoming the retina and the outside remaining a single monolayer of epithelium known as the retinal pigment epithelium. Initially both walls of the optic cup are one cell thick, but the cells of the inner wall divide to form a neuroepithelial layer many cells thick: the retina In the center of the retina is the optic nerve, a circular to oval white area measuring about 2 x 1.5 mm across. From the center of the optic nerve radiate the major blood vessels of the retina. There are two sources of blood supply to the mammalian retina: the central retinal artery and the choroidal blood vessels. The choroid receives the greatest blood flow (65-85%) (Henkind et al., 1979) and is vital for the maintainance of the outer retina (particularly the photoreceptors) and the remaining 20-30% flows to the retina through the central retinal artery from the optic nerve head to nourish the inner retinal layers. The central retinal artery has 4 main branches in the human retina. The arterial intraretinal branches then supply three layers of capillary networks i.e. 1) the radial peripapillary capillaries (RPCs) and 2) an inner and 3) an outer layer of capillaries. The precapillary venules drain into venules and through the corresponding venous system to the central retinal vein. Approximately 17 degrees (4.5-5 mm), or two and half disc diameters to the left of the disc, can be seen the slightly oval- shaped, blood vessel-free reddish spot, the fovea, which is at the center of the area known as the macula by ophthalmologists. A circular field of approximately 6 mm around the fovea is considered the central retina while beyond this is peripheral retina stretching to the ora serrata, 21 mm from the center of the optic disc. The total retina is a circular disc of approximately 42 mm diameter. The retina is approximately 0.5 mm thick and lines the back of the eye. The optic nerve contains the ganglion cell axons running to the brain and, additionally, incoming blood vessels that open into the retina to vascularize the retinal layers and neurons. A radial section of a portion of the retina reveals that the ganglion cells (the output neurons of the retina) lie innermost in the retina closest to the lens and front of the eye, and the photosensors (the rods and cones) lie outermost in the retina against the pigment epithelium and choroid. Light must, therefore, travel through the thickness of the retina before striking and activating the rods and cones. Subsequently the absorbtion of photons by the visual pigment of the photoreceptors is translated into first a biochemical message and then an electrical message that can stimulate all the succeeding neurons of the retina. The retinal message concerning the photic input and some preliminary organization of the visual image into several forms of sensation are transmitted to the brain from the spiking discharge pattern of the ganglion cells. A simplistic wiring diagram of the retina emphasizes only the sensory photoreceptors and the ganglion cells with a few interneurons connecting the two cell types such as seen in the figure 2. References: Kolb, H., Fernandez, E., & Nelson, R. (2003) Webvision: Organization of the Retina and Visual System. Retrieved April 15, 2007 from http://webvision.med.utah.edu/. “Red Eye” Differential diagnosis: • Conjunctivitis (viral, bacterial, allergic): most common; dilatation of superficial conjunctival blood vessels resulting in hyperemia, edema, and discharge. • Uveitis: inflammation of the iris and ciliary body, usually in young or middle-aged patients; its hallmark is the presence of inflammatory cells and protinaceous flare in the anterior chamber of the eye • Acute angle-closure glaucoma: a narrow anterior chamber angle can occur in patients with hyperopia (farsightedness) and older patients resulting in rapid elevation of intraocular pressure • Keratitis (corneal ulcer or inflammation, eg, herpes simplex): inflammation of the corneal epithelium and superficial stroma; present in cases of corneal abrasion or contact lens overwear • Scleritis: can impair vision and may be associated with vascular or connective tissue disease; prompt treatment needed • Episcleritis: self-limited, recurrent, presumably autoimmune inflammation of the episcleral vessels • Subconjunctival hemorrhage: redness is unilateral and well-circumscribed; underlying sclera is not visible and adjacent sclera is free of inflammation; may be due to trauma, anticoagulation, hypertension, excessive coughing or vomiting • Eyelid disorder (eg, blepharitis): inflammation of the eyelid often associated with conjunctival inflammation, caused by a variety of infectious agents, allergic disorders, and dermatologic diseases Patient evaluation: The following are important questions to ask while taking the patient history: • Is vision affected? • Is there foreign body sensation? May suggest corneal involvement.