Blind spot (vision): Difference between revisions

Latest revision as of 02:56, 11 December 2024

Area of the retina without photoreceptors

Blind spot (also known as the optic disc) refers to a specific area on the retina of the eye where the optic nerve exits the eye. This region lacks photoreceptor cells, meaning it cannot detect light, resulting in a gap in the visual field. Despite this, the brain typically compensates for the blind spot, so it is not usually noticeable in everyday vision.

Anatomy and Physiology[edit]

The blind spot is located approximately 15 degrees temporally from the point of fixation in each eye. It corresponds to the location where the ganglion cell axons exit the eye to form the optic nerve. This area is devoid of rods and cones, the photoreceptors responsible for detecting light and color.

The optic disc is approximately 1.5 mm in diameter and is situated nasally in the visual field. The absence of photoreceptors in this region means that any light that falls on the optic disc is not detected, creating a "blind" spot.

Compensation by the Brain[edit]

The human brain uses information from both eyes to fill in the blind spot. When both eyes are open, the blind spots do not overlap, allowing the brain to use visual information from one eye to fill in the missing information from the other. Even with one eye closed, the brain can use surrounding visual cues to "fill in" the blind spot, making it unnoticeable under normal circumstances.

Testing for the Blind Spot[edit]

The blind spot can be demonstrated using a simple test. By closing one eye and focusing on a specific point, an object placed at a certain angle from the point of fixation will disappear from view when it falls on the blind spot. This test highlights the area of the visual field that corresponds to the optic disc.

Clinical Significance[edit]

While the blind spot is a normal anatomical feature, changes in its size or shape can indicate pathological conditions. For example, swelling of the optic disc, known as papilledema, can occur due to increased intracranial pressure and may affect vision.

Also see[edit]

References[edit]

Eric R.,

 Principles of Neural Science, 
  
 McGraw-Hill, 
 2013, 
  
  
 ISBN 978-0071390118,

Purves, Dale,

 Neuroscience, 
 Sinauer Associates, 
 2012,
 Vol. 5th edition,

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-==Blind Spot (Scotoma)==
+{{Short description|Area of the retina without photoreceptors}}
+{{Use dmy dates|date=October 2023}}
-[[File:Yeux et fonds d'œil.png|thumb|Diagram showing the position of the blind spot in the human eye.]]
+'''Blind spot''' (also known as the '''optic disc''') refers to a specific area on the [[retina]] of the eye where the [[optic nerve]] exits the eye. This region lacks [[photoreceptor]] cells, meaning it cannot detect light, resulting in a gap in the visual field. Despite this, the brain typically compensates for the blind spot, so it is not usually noticeable in everyday vision.
-A '''blind spot''', or '''scotoma''', is an area in the visual field that lacks detection capabilities due to an absence of photoreceptor cells. The most well-known blind spot is the '''physiological blind spot''', also referred to as the '''blind point''' or '''punctum caecum''' in medical literature. This specific blind spot corresponds to the location on the retina known as the optic disc, where the optic nerve exits the eye, leading to an absence of light-detecting cells.
+==Anatomy and Physiology==
+The blind spot is located approximately 15 degrees temporally from the point of fixation in each eye. It corresponds to the location where the ganglion cell axons exit the eye to form the optic nerve. This area is devoid of [[rod cell|rods]] and [[cone cell|cones]], the photoreceptors responsible for detecting light and color.
-===Physiological Blind Spot===
+[[File:Human photoreceptor distribution.svg|thumb|Distribution of photoreceptors in the human retina, showing the absence of photoreceptors at the optic disc.]]
-The physiological blind spot exists because the optic disc, the point on the retina where the optic nerve fibers exit the eye, does not contain any photoreceptor cells. This lack of photoreceptors means that no visual information is detected at this point, creating a blind spot in the visual field.
-<youtube>
+The optic disc is approximately 1.5 mm in diameter and is situated nasally in the visual field. The absence of photoreceptors in this region means that any light that falls on the optic disc is not detected, creating a "blind" spot.
-title='''{{PAGENAME}}'''
-movie_url=http://www.youtube.com/v/fhIsfwVa-S4
-&rel=1
-embed_source_url=http://www.youtube.com/v/fhIsfwVa-S4
-&rel=1
-wrap = yes
-width=750
-height=600
-</youtube>
-===Detection and Significance===
+==Compensation by the Brain==
-Despite its presence, the physiological blind spot is not normally perceived in daily vision. This is because the brain uses the information from the surrounding retina and the other eye to fill in the gap, interpolating the blind spot based on adjacent visual detail. This remarkable process is a testament to the brain's ability to adapt and process incomplete information.
+The human brain uses information from both eyes to fill in the blind spot. When both eyes are open, the blind spots do not overlap, allowing the brain to use visual information from one eye to fill in the missing information from the other. Even with one eye closed, the brain can use surrounding visual cues to "fill in" the blind spot, making it unnoticeable under normal circumstances.
-====Causes and Types of Scotomas====
+==Testing for the Blind Spot==
-In addition to the physiological blind spot, there are various types of scotomas that can arise due to diseases, injuries, or other conditions affecting the eye or brain. These include:
+The blind spot can be demonstrated using a simple test. By closing one eye and focusing on a specific point, an object placed at a certain angle from the point of fixation will disappear from view when it falls on the blind spot. This test highlights the area of the visual field that corresponds to the optic disc.
-* '''Central scotomas''': Affect the central portion of the visual field, often related to age-related macular degeneration.
-* '''Peripheral scotomas''': Occur on the outskirts of the visual field, which can be linked to glaucoma or peripheral retinal disease.
-* '''Arcuate scotomas''': Arc-shaped blind spots that can be a sign of glaucoma.
-===Detection Methods===
+==Clinical Significance==
-Scotomas can be detected through comprehensive eye exams, including:
+While the blind spot is a normal anatomical feature, changes in its size or shape can indicate pathological conditions. For example, swelling of the optic disc, known as [[papilledema]], can occur due to increased intracranial pressure and may affect vision.
-* '''Visual field tests''': Assess the complete area visible to the eye when it is focused on a central point.
-* '''Amsler grid tests''': Used particularly to identify central scotomas associated with macular degeneration.
-===Brain's Compensation for Blind Spots===
+==Also see==
-The human brain compensates for the presence of the physiological blind spot through a process known as '''filling-in''', where it uses information from the surrounding visual field and the other eye to create a continuous image. This complex neural mechanism allows individuals to remain unaware of their blind spot during normal activities.
+* [[Retina]]
+* [[Optic nerve]]
+* [[Photoreceptor cell]]
+* [[Visual field]]
+* [[Papilledema]]
-==External Links==
+==References==
-* [https://www.nei.nih.gov/ National Eye Institute]
+* {{Cite book|last=Kandel|first=Eric R.|title=Principles of Neural Science|year=2013|publisher=McGraw-Hill|isbn=978-0071390118}}
-* [https://www.aao.org/ American Academy of Ophthalmology]
+* {{Cite journal|last=Purves|first=Dale|title=Neuroscience|journal=Sinauer Associates|year=2012|volume=5th edition}}
+[[File:Night blind spot.png|thumb|Diagram showing the night blind spot, which is different from the optic disc blind spot.]]
+{{Vision}}
+{{Eye anatomy}}
+[[Category:Vision]]
 [[Category:Ophthalmology]]
-[[Category:Visual system]]
+[[Category:Neuroscience]]
-[[Category:Neurology]]
-{{stub}}