II. Anatomy

  1. Retina
    1. Lines the globe inner surface and contains light sensitive Neurons that transmit signals to the Optic Nerve
    2. Photoreceptors (rods and cones) comprise the inner, sensory layer of the Retina
  2. Macula
    1. Retinal region responsible for central Vision
    2. Lies two disc diameters lateral to the optic disc
  3. Fovea
    1. Subpart of the Macula with highest Visual Acuity (and highest cone density)
  4. Images
    1. eyeRetinaGrayBB879.gifLewis (1918) Gray's Anatomy 20th ed (in public domain at Yahoo or BartleBy)
    2. eyeRetinaMicroGrayBB882.gifLewis (1918) Gray's Anatomy 20th ed (in public domain at Yahoo or BartleBy)
    3. eyeRetinaMicroGrayBB881.gifLewis (1918) Gray's Anatomy 20th ed (in public domain at Yahoo or BartleBy)

III. Physiology: Neurons

  1. Background
    1. Light is refracted from Cornea and lens through pupil onto the Retina
    2. Photoreceptors (rods and cones) lie on the deepest portion of the Retina, adjacent to the Choroid
      1. Light passes through both Retinal plexiform layers to reach the photoreceptors
    3. Light stimulates photoreceptors and generates electron flow
      1. Signals are then passed from the deepest Retina, back to the superficial Retina and out the Optic Nerve
      2. Signals are passed from the inner plexiform to outer plexiform layer via bipolar cells
      3. Ganglion cells (individual Neurons of the Optic Nerve) are triggered in the outer plexiform layer
    4. Lateral inhibition prevents excessive lateral signal spread
      1. Facilitated by horizontal cells, amacrine cells and interpexiform cells
  2. Step 1: Photoreceptor Cells
    1. Rods (black and white Vision)
      1. Rods are most concentrated on the periphery
      2. More sensitive than cones to dim light (or night Vision)
      3. Decreased Visual Acuity compared with cones
        1. Rod to bipolar cell ratio may approach 1:1000
    2. Cones (color Vision)
      1. Concentrated at center of Retina (fovea)
      2. High Visual Acuity compared with rods
        1. Cone to bipolar cell ratio approaches 1:1
  3. Step 2: Outer Plexiform Layer (input from photoreceptors, adjacent to pigment epithelium and Choroid)
    1. Horizontal Cells
      1. Transmit signals horizontally (within the outer plexiform layer) between rods, cones and bipolar cells
    2. Bipolar Cells
      1. Transmits signals from photoreceptors and horizontal cells to inner plexiform layer
  4. Step 3: Inner Plexiform Layer (output to Optic Nerve, closer to vitreous)
    1. Amacrine Cells
      1. Transmits signals horizontally (within the inner plexiform layer) between bipolar and Ganglion cells
    2. Ganglion Cells
      1. Form individual Neurons of the Optic Nerve
  5. Inhibitory Cells
    1. Interplexiform Cells
      1. Transmit feedback inhibitory signals back from inner plexiform to outer plexiform layer
      2. Inhibit lateral signal spread

IV. Physiology: Color Vision

  1. Retina have three types of color detecting cone photoreceptors that roughly correlate with red, green and blue Perception
  2. Photoreceptors are most sensitive to light at peak wavelengths along the light spectrum
    1. Long (Red): 564–580 nm
    2. Medium (Green): 534–545 nm
    3. Short (Blue): 420–440 nm
  3. Each of the cone types are stimulated by light of a wider range that overlaps with other cone types
    1. However, cone firing will be maximal when stimulated in their peak range
    2. Combination of the individual firing of these three cone types will be interpreted as specific color variations
  4. Disorders
    1. See Color Blindness

V. References

  1. Guyton and Hall (2006) Medical Physiology, Elsevier, Philadelphia, p. 626-39

Images: Related links to external sites (from Bing)

Related Studies

Ontology: Structure of fovea centralis (C0016622)

Definition (NCI) Area consisting of a small depression in the retina containing only cones and where vision is most acute.
Definition (MSH) An area approximately 1.5 millimeters in diameter within the macula lutea where the retina thins out greatly because of the oblique shifting of all layers except the pigment epithelium layer. It includes the sloping walls of the fovea (clivus) and contains a few rods in its periphery. In its center (foveola) are the cones most adapted to yield high visual acuity, each cone being connected to only one ganglion cell. (Cline et al., Dictionary of Visual Science, 4th ed)
Definition (PSY) Centrally located and depressed portion of the retina containing only cone photoreceptors.
Definition (CSP) area within the macula lutea where the retina thins out greatly because of the oblique shifting of all layers except the pigment epithelium layer; includes the sloping walls of the fovea (clivus) and contains a few rods in its periphery; in its center (foveola) are the cones most adapted to yield high visual acuity, each cone being connected to only one ganglion cell.
Concepts Body Part, Organ, or Organ Component (T023)
MSH D005584
SnomedCT 181173008, 67046006
English Fovea Centralis, fovea centralis retinae, Fovea (body structure), Fovea centralis, Fovea centralis of retina, Center of fovea, Center of macula, Centre of fovea, Centre of macula, Structure of fovea centralis (body structure), Structure of fovea centralis, Fovea
French Fossette centrale de la macula, Fovea centralis, Fossette centrale
Swedish Centralgropen
Czech fovea centralis
Finnish Verkkokalvon keskikuoppa
Latvian Bedrīte, centrālā
Polish Dołek środkowy
Norwegian Fovea centralis
Spanish estructura de la fóvea central (estructura corporal), estructura de la fóvea central, fóvea central de la retina, fóvea central, Fóvea Central
German Fovea centralis
Italian Fovea centrale
Dutch Fovea centralis, Gele vlek
Portuguese Fóvea Central

Ontology: Retinal Diseases (C0035309)

Definition (MEDLINEPLUS)

The retina is a layer of tissue in the back of your eye that senses light and sends images to your brain. In the center of this nerve tissue is the macula. It provides the sharp, central vision needed for reading, driving and seeing fine detail.

Retinal disorders affect this vital tissue. They can affect your vision, and some can be serious enough to cause blindness. Examples are

  • Macular degeneration - a disease that destroys your sharp, central vision
  • Diabetic eye disease
  • Retinal detachment - a medical emergency, when the retina is pulled away from the back of the eye
  • Macular pucker - scar tissue on the macula
  • Macular hole - a small break in the macula that usually happens to people over 60
  • Floaters - cobwebs or specks in your field of vision

NIH: National Eye Institute

Definition (NCI) Any disease or disorder of the retina.
Definition (NCI) An abnormal structure or function of the retina and its associated tissues.
Definition (NCI_CTCAE) A disorder involving the retina.
Definition (CSP) pathologic condition of the innermost of the three tunics of the eyeball or retina.
Concepts Disease or Syndrome (T047)
MSH D012164
ICD9 362.9
ICD10 H35.9
SnomedCT 193430004, 267715002, 35426003, 399625000, 29555009
English Disease, Retinal, Diseases, Retinal, Retinal Diseases, Unspecified retinal disorder, RETINAL DISORDER, retina disorder, RETINOPATHY, Retinal disorder NOS, Retinal disorder, unspecified, RETINAL DIS, retinopathy (diagnosis), retinopathy, Disorder retinal, Retinopathy N0S, Retinopathy NOS, Retinal Diseases [Disease/Finding], diseases retinal, retinopathies, Disorder;retina, disease retinal, retinal diseases, disorders retina, disorders retinal, retinal disease, retinal disorder (diagnosis), Retinal Disorders, Retinal disorder NOS (disorder), Retinopathies, Retinopathy, Retinal disorder, Retinal disease, Retinal disorder (disorder), Retinopathy (disorder), disease (or disorder); retina, retina; disorder, Retinopathy, NOS, Retinal disease, NOS, Retinal disorder, NOS, Retinal Disease, Retinal Disorder, retinal disorder
French RETINOPATHIE, Trouble de la rétine, Rétinopathie SAI, Trouble rétinien SAI, Affection rétinienne non précisée, TROUBLE RETINIEN, Rétinopathie, Trouble rétinien, Rétinopathies, Maladies de la rétine, Maladies rétiniennes
Italian Retinopatia, Patologia retinica, Alterazione retinica, Disturbo non specificato della retina, Patologia retinica NAS, Retinopatia NAS, Malattie della retina
Dutch retinopathie NAO, niet-gespecificeerde retina-aandoening, retina-aandoening NAO, aandoening retina, Retinopathie, aandoening; retina, retina; aandoening, Aandoening van retina, niet gespecificeerd, retina-aandoening, retinopathie, Retinaziekte, Retinaziekten, Ziekte, retina-, Ziekten, retina-
German unspezifische Erkrankung der Retina, Erkrankung der Retina NNB, Retinopathie NNB, Affektion der Netzhaut, nicht naeher bezeichnet, RETINAERKRANKUNG, RETINOPATHIE, Retinopathie, Erkrankung der Retina, Netzhauterkrankungen, Retinakrankheiten
Portuguese Retinopatia NE, Afecção da retina, Afecção da retina NE, Alteração da retina NE, ALTERACAO DA RETINA, RETINOPATIA, Retinopatia, Anomalia da retina, Doenças Retinianas
Spanish Retinopatía NEOM, Trastorno retiniano, Trastorno retiniano NEOM, Trastorno retiniano no especificado, RETINA, TRASTORNO, RETINOPATIA, trastorno de la retina (trastorno), trastorno retiniano (trastorno), trastorno retiniano, trastorno de la retina, trastorno retiniano, SAI (trastorno), trastorno retiniano, SAI, enfermedad retiniana, retinopatía (trastorno), retinopatía, Alteración retiniana, Retinopatía, Enfermedades de la Retina
Japanese 詳細不明の網膜障害, 網膜症, 網膜障害NOS, 網膜症NOS, 網膜障害, モウマクショウ, モウマクショウガイ, モウマクショウガイNOS, ショウサイフメイノモウマクショウガイ, モウマクショウNOS
Swedish Näthinnesjukdomar
Finnish Verkkokalvon sairaudet
Czech Nespecifikovaný defekt sítnice, Porucha sítnice, Onemocnění sítnice NOS, Retinopatie NOS, Onemocnění sítnice, Retinopatie, nemoci retiny, nemoci sítnice, retina - nemoci
Korean 상세불명의 망막 장애
Polish Choroby siatkówki
Hungarian Retinabetegség, Retina betegség, k.m.n., Retinopathia, Retinopathia k.m.n., Nem meghatározott retina betegség
Norwegian Retinale sykdommer, Sykdommer i retina, Netthinnesykdommer, Retinasykdommer

Ontology: Retinal macula (C0450295)

Definition (NCI) A yellowish, highly pigmented, oval shaped area slightly lateral to the center of the retina of the eye which contains the fovea centralis and is mostly comprised of retinal cones.
Definition (MSH) An oval area in the retina, 3 to 5 mm in diameter, usually located temporal to the posterior pole of the eye and slightly below the level of the optic disk. It is characterized by the presence of a yellow pigment diffusely permeating the inner layers, contains the fovea centralis in its center, and provides the best phototropic visual acuity. It is devoid of retinal blood vessels, except in its periphery, and receives nourishment from the choriocapillaris of the choroid. (From Cline et al., Dictionary of Visual Science, 4th ed)
Concepts Body Part, Organ, or Organ Component (T023)
MSH D008266
SnomedCT 82859000
English Lutea, Macula, Luteas, Macula, Macula Lutea, Macula Luteas, Retinal macula, macula, macula lutea, Macula lutea, Macula, Macula lutea structure (body structure), Macula lutea structure
French Macula lutea, Macula, Tache jaune
Swedish Gula fläcken
Czech macula lutea, žlutá skvrna na sítnici
Finnish Keltatäplä
Latvian Dzeltenais plankums
Polish Plamka żółta
Norwegian gule flekken, Macula lutea, Den gule flekken
Spanish estructura de la mácula lútea (estructura corporal), estructura de la mácula lútea, mácula lútea, Mácula Lútea
German Gelber Fleck (Netzhaut), Macula lutea
Italian Macula lutea
Dutch Gele vlek, Macula lutea
Portuguese Macula Lutea