Editing Glaucoma (section)

==Visual field defects in glaucoma==
{{see also|Visual field}}
[[File:Bjerrums area and types of scotomas on the visual field.png|thumb|Bjerrums area and types of scotomas on the visual field]]
In glaucoma visual field defects result from damage to the [[retinal nerve fiber layer]] (RNFL). Field defects are seen mainly in primary open angle glaucoma. Because of the unique anatomy of the RNFL, many noticeable patterns are seen in the visual field. Most of the early glaucomatous changes are seen within the central visual field, mainly in Bjerrum's area, 10-20° from fixation.<ref name="Parson-GL">{{cite book |title=Parsons' diseases of the eye |publisher=Elsevier |isbn=978-81-312-3818-9 |pages=288–295 |edition=22nd |chapter=Glaucoma|date=15 July 2015 }}</ref>

Following are the common glaucomatous field defects:

* '''Generalized depression''': Generalized depression is seen in early stages of glaucoma and many other conditions. Mild constriction of central and peripheral visual field due to isopter contraction comes under generalized depression. If all the isopters show similar depression to the same point, it is then called a contraction of visual field. Relative paracentral scotomas are the areas where smaller and dimmer targets are not visualized by the patient.<ref name="Parson-GL" /> Larger and brighter targets can be seen. Small paracentral depressions, mainly superonasal are seen in normal tension glaucoma (NTG).<ref name="Kanski-GL">{{cite book | vauthors = Salmon JF |title=Kanski's Clinical ophthalmology |publisher=Elsevier |edition=9th |chapter=Glaucoma|pages=362–365}}</ref> The generalized depression of the entire field may be seen in cataract also.<ref name="Eyerounds">{{cite web | vauthors = Carroll JN, Johnson CA |title=Visual Field Testing: From One Medical Student to Another |url=https://eyerounds.org/tutorials/VF-testing/ |date=2013-08-22}}</ref>
* '''Baring of blind spot''': "Baring of blind spot" means exclusion of blind spot from the central field due to inward curve of the outer boundary of 30° central field.<ref name="Khurana-GL">{{cite book | vauthors = Khurana AK, Khurana B|title=Comprehensive ophthalmology |publisher=Jaypee, The Health Sciences Publisher |isbn=978-93-5152-657-5 |pages=223–224 |edition=6th |chapter=Glaucoma|date=31 August 2015 }}</ref> It is only an early non-specific visual field change, without much diagnostic value in glaucoma.<ref name="Khurana-GL"/>
* '''Small wing-shaped Paracentral scotoma''': Small wing-shaped Paracentral scotoma within Bjerrum's area is the earliest clinically significant field defect seen in glaucoma. It may also be associated with nasal steps. Scotoma may be seen above or below the blind spot.<ref name="Khurana-GL"/>
* '''Siedel's sickle-shaped scotoma''': Paracentral scotoma joins with the [[Blind spot (vision)|blind spot]] to form the [[Seidel sign]]. 
* '''Arcuate or Bjerrum's scotoma''':[[File:Visual field arcuate scotoma.png|thumb|Arcuate scotoma]]  It is formed at later stages of glaucoma by extension of Seidel's scotoma in an area either above or below the fixation point to reach the horizontal line. Peripheral breakthrough may occur due to damage of nerve fibers.<ref name="Khurana-GL"/>
* '''Ring or Double arcuate scotoma''': Two arcuate scotomas join to form a Ring or Double arcuate scotoma. This defect is seen in advanced stages of glaucoma.
* '''Roenne's central nasal step''': It is created when two arcuate scotomas run in different arcs to form a right angled defect. This is also seen in advanced stages of glaucoma.
* '''Peripheral field defects''': Peripheral field defects may occur in early or late stages of glaucoma. Roenne's peripheral nasal steps occur due to contraction of peripheral isopter.<ref name="Khurana-GL"/>
* '''Tubular vision''': [[File:Eye disease simulation, retinitis pigmentosa.jpg|thumb|Tubular vision]] Since macular fibers are the most resistant to glaucomatous damage, the central vision remains unaffected until end stages of glaucoma. Tubular vision or [[Tunnel vision]] is the loss of peripheral vision with retention of central vision, resulting in a constricted circular tunnel-like field of vision. It is seen in the end stages of glaucoma. [[Retinitis pigmentosa]] is another disease that causes tubular vision.<ref>{{cite web|title = Retinitis pigmentosa|url = http://ghr.nlm.nih.gov/condition/retinitis-pigmentosa|website = Genetics Home Reference}}</ref>
* '''Temporal island of vision''': It is also seen in end stages of glaucoma. The temporal islands lie outside of the central 24 to 30° visual field,<ref>{{cite web | vauthors = Themes UF |title=Visual Fields in Glaucoma |url=https://entokey.com/visual-fields-in-glaucoma/#:~:text=The%20typical%20visual%20field%20in,24%20to%2030%C2%B0%C2%B0 |website=Ento Key |date=11 July 2016}}</ref> so it may not be visible with standard central field measurements done in glaucoma.