Question
A patient presented with blurring of vision.He is diagnosed to be suffering from an eye condition with narrow angle of Anterior chamber . On examination IOP was found to be more than 21 mmHg and field defect was found as shown in the image.Identify this field defect .
A. Superior paracentral scotoma.
B. Bjerrum’s scotoma.
C. Seidel’s scotoma.
D. Double arcuate scotoma.
|
Correct Answer » D Explanation |
 |
Ans:D. Double arcuate or ring shaped scotoma: It develops when two arcuate scotomas join.
The patient is suffering from Angle Closure Glaucoma
Glaucoma
- It is a group of eye diseases which result in damage to the optic nerve and vision loss.(seen as cupping of optic disc,increased cup to disc ratio more than 0.3 and visual fied defects on perimetry)
- The most common type is open-angle glaucoma with less common types including closed-angle glaucoma and normal-tension glaucoma.
- An elevated IOP (more than 21 mmHg)is the most important risk factor for the development of glaucoma.
Field of vision or Visual field
- It is defined as the area that is perceived while fixating one central target.
- It is “an island of vision surrounded by a sea of darkness”.
- It is a 3D hill – peak being fovea and at ground level, it extends ~ 50° superiorly, 60° nasally, 70° inferiorly and 90° temporally.
- Normal blind spot is 15° temporal to the fixation and measure 6° wide and 8° high.
- Terminologies:
- Scotoma: Area of reduced sensitivity surrounded by a more sensitive area
- Depression: Area of reduced sensitivity without a normal surround
- Isopter: A threshold line joining points of equal sensitivity on a visual field chart
- Fixation: Part of visual field corresponding to fovea centralis
- Central field: Portion of visual field within 30° of fixation
- Bjerrum’s area: Central visual field within 25° of fixation.
Progression of Visual Field Defects in Glaucoma
90% of the early glaucomatous changes are within central field.
A. Early non-specific changes:
- Isopter contraction (Generalized depression): Mild constriction of central and peripheral field
- Baring of blind spot.
B. Early significant changes:
- Peripheral nasal step (may be early or late): Due to unequal contraction of peripheral isopter
- Small wing-shaped Paracentral scotoma (Within Bjerrum’s area).
- Siedel’s sickle-shaped scotoma: Paracentral scotoma joins the blind spot (it is alsko known as Derringer scotoma)
C. Late significant changes:
- Arcuate or Bjerrum scotoma: Extension of Seidel’s scotoma in an area either above or below the fixation point to reach the horizontal line
- Ring or Double arcuate scotoma: When 2 arcuate scotomas join together
- Roenne’s central nasal step
D. Advanced glaucomatous field defects:
- Tubular vision: Only a small island of central vision accompanied by temporal island
- No light perception: Complete visual field defect (temporal island is the most resistant one)
