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Glossary

Adaptive Immune System
The adaptive immune response is the second line of defense after the innate immune system and destroys invading pathogens by producing a specific response. However, the adaptive immune response takes from several days to weeks to develop.10

Age-related macular degeneration (AMD)

Age-related macular degeneration (AMD) is a degenerative disease that affects the macular region of the retina, causing progressive, irreversible, loss of vision.3

Amsler Grid

The Amsler Grid is a device used to screen for AMD. Patients fixate with one eye at a time on the small dot in the center of the grid to asses impairments in the visual field and line detection.4

Atrophy
Body tissue or an organ that wastes away, especially as a result of the degeneration of cells.14

Best Corrected Visual Acuity (BCVA)

The best-corrected visual acuity (BVCA) test is used to determine foveal (or central) visual acuity.7

Bipolar cells

Bipolar cells are responsible for relaying electric impulses from photoreceptors to ganglion, horizontal and amacrine cells.1

Choroid
The choroid is the sole supplier of oxygen and nutrients to the outer layers of the retina and is the primary route in which waste is cleared from the retina. Given the high metabolic rate of the photoreceptors, the highest of any cell in the body, the choroid is one of the most vascularized tissues in the body.17

Choroidal neovascularization
This term describes the growth of new blood vessels that originate from the choroid through a break in the Bruch membrane into the sub–retinal pigment epithelium or subretinal space. Choroidal neovascularization is a major cause of visual loss.16

Complement System

The complement system (or complement cascade) is a complex biological network that is a major component of the innate immune system. It is one of the first lines of defense against invading pathogens.11

Cornea

The cornea is the transparent external surface of the eye that covers the iris and pupil. The cornea is responsible for the majority of the refraction necessary to focus incoming light onto the retina.9

Diagnostic testing

Diagnostic imaging tests are used to examine the presence and characteristics of AMD features in a patient.4

Drusen

Drusen are small yellow deposits of fatty proteins (lipids) that accumulate under the retina. They are a key feature of classification systems used to grade the stage and severity of AMD.13

Fovea
The fovea is the part at the center of the macula. This is the area with the highest visual acuity in the eye.9

Fundus
The fundus is the inside, back surface of the eye. It is made up of the retina, macula, optic disc, fovea and blood vessels.15

Fundus Camera
The fundus camera is a digital imaging system that captures autofluorescence using a single flash of light. Fundus cameras can capture both color and monochrome images of the retina.8

Fundus Examination

Fundus examinations are routinely carried out as part of an eye exam to assess the overall health of the retina as many features of AMD are visible by examination of the fundus.1

Ganglion Cells

Ganglion cells receive electric impulses from bipolar cells and transmit them to the brain. Importantly, the ganglion cells are the only source of output from the retina.1

Geographic Atrophy (GA)

Geographic Atrophy is a term used to describe the advanced form of dry age-related macular degeneration (AMD). It is called Geographic Atrophy because the affected area of degeneration looks like a map to the ophthalmologist.12

Immune System

The immune system is a complex network of organs, cells, and proteins that work together to protect the body.5

Initial testing

The initial evaluation of a patient to assess their vision and look for signs or symptoms of an eye disease, including AMD.4

Innate Immune System

The innate immune system is composed of physical barriers, chemical barriers, and cellular immune responses that work together to protect the body.10

Iris & Pupil

The iris regulates the amount of light that is let into the eye by constricting or expanding the pupil.9

Lens

The lens is a transparent structure behind the iris and the pupil that helps, in addition to the cornea, to refract light onto the retina. The lens provides focusing power through a process called accommodation.9

Low-Luminance Visual Acuity (LLVA)

A low-luminance visual acuity (LLVA) test is used to measure visual function in low- light. Advanced AMD patients tend to have poor visual acuity in low-light.3

Macula

The macula is a small pigmented area at the center of the retina which is responsible for central vision and color perception.9

Microperimetry

Microperimetry is a visual field test that is used to spatially map the function of photoreceptors in the macula.6

Ophthalmoscopy

Ophthalmoscopy, or fundoscopy, is used to examine the fundus and is often carried out as part of a routine eye exam.4

Optic nerve

The optic nerve consists of a bundle of nerve fibers that is responsible for transmitting visual information from the retina to the brain.9

Optical coherence tomography (OCT)
Optical Coherence Tomography (OCT) is a test that uses long wavelengths of light to take rapid cross-sectional images of the retina and surrounding structures. OCT enables 2D and 3D visualization of each of the retina’s distinct layers to measure retinal thickness. Retinal thickness can be used to identify areas of atrophy and monitor progression.18


Photoreceptors

Photoreceptors are special sensory cells that convert light into electric impulses.1

Retina

The retina is a thin layer of tissue at the back of the eye. The retina converts light to electrical impulses which are sent to the brain and processed to create vision.9

Retinal pigmented epithelium (RPE)

The retinal pigmented epithelium (RPE) is a single layer of cells in the outer layer of the retina. The RPE plays a critical role in maintaining visual function.9

Sclera

The sclera forms the thick fibrous tissues that make up the white outer layer of the eye. It is composed of collagen and elastin fiber which work as a support tissue that protects against debris and infection in addition to providing structure for the eye.9

Vitreous Humor

The vitreous humor comprises a large portion of the eyeball. It is a clear gel-like substance that occupies the space behind the lens and in front of the retina at the back of the eye.9




References:

  1. Bear, M., Connors, B. & Paradiso, M. Neuroscience: Exploring the Brain (Third Edition). Library (Lond). (2006) doi:10.1007/BF02234670.
  2. Mitchell, P., Liew, G., Gopinath, B. & Wong, T. Y. Age-related macular degeneration. www.thelancet.comvol. 392 www.thelancet.com (2018).
  3. Fleckenstein, M. et al.The progression of geographic atrophy secondary to age-related macular degeneration. Ophthalmology125, 369–390 (2018).
  4. American  Academy  of  Ophthalmology. Age-Related  Macular  Degeneration  Preferred Practice Pattern. (2019).
  5. Sattler, S. The role of the immune system beyond the fight against infection. in Advances in Experimental Medicine and Biology vol. 1003 3–14 (Springer New York LLC, 2017)."
  6. Csaky,  K.  G. et  al.Microperimetry  for  geographic  atrophy  secondary  to  age-related macular degeneration. Surv. Ophthalmol.64, 353–364 (2019).
  7. Lakshminarayanan, V. Visual acuity. in Handbook of Visual Display Technologyvol. 1 93–99 (Springer Berlin Heidelberg, 2012).
  8. Yung, M., Klufas, M. A. & Sarraf, D. Clinical applications of fundus autofluorescence in retinal disease. International Journal of Retina and Vitreous vol. 2 (2016).
  9. Remington, L. A. Aqueous and Vitreous Humors. in Clinical Anatomy and Physiology ofthe Visual System 109–122 (Elsevier Health Sciences, 2012). doi:10.1016/b978-1-4377-1926-0.10006-2."
  10. Janeway, C. J., Travers, P., Walport, M. & Al., E. Immunobiology: The Immune System in Health and Disease. 5th Edition. (2001)." Immune System in Health and Disease. 5th edition. (Garland Science, 2001)."
  11. Merle, N. S., Noe, R., Halbwachs-Mecarelli, L., Fremeaux-Bacchi, V. & Roumenina, L. T. Complement system part II: Role in immunity. Frontiers in Immunologyvol. 6 (2015).
  12. What is Geographic Atrophy? Bright Focus Foundation. Accessed Apr. 29, 2021.  https://www.brightfocus.org/macular/article/what-geographic-atrophy
  13. Bonnel, S., Mohand-Said, S. & Sahel, J. A. The aging of the retina. Exp. Gerontol. (2003) doi:10.1016/S0531-5565(03)00093-7.
  14. Ambati, J. & Fowler, B. J. Mechanisms of age-related macular degeneration. Neuron vol. 75 26–39 (2012).
  15. American  Academy  of  Ophthalmology. Fundus. Accessed Apr. 29, 2021. https://www.aao.org/eye-health/anatomy/fundus
  16. Elshatory, Y. Age-related macular degeneration. https://eyewiki.aao.org/Agerelated_macular_degeneration#cite_note-34 (2019).
  17. Holz, F. G. et al. Efficacy and safety of lampalizumab for geographic atrophy due to age-related macular degeneration: Chroma and spectri phase 3 randomized clinical trials. JAMA Ophthalmol. 136, 666–677 (2018).
  18. Holz, F. G. et al. Imaging protocols in clinical studies in advanced age-related macular degeneration: recommendations from classification of atrophy consensus Meetings. Ophthalmology 124, 464–478 (2017).


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