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Pulfrich's phenomenon in unilateral cataract
S M Scotcher1, D A Laidlaw, C R Canning
1Southampton Eye Unit.
The British Journal of Ophthalmology
|March 14, 1998
Summary
Unilateral cataract can induce a pathological Pulfrich phenomenon, a visual distortion. This effect, measurable with filters, resolves after cataract surgery, explaining some visual symptoms.
Area of Science:
- Ophthalmology
- Visual Neuroscience
Background:
- Unilateral cataract can lead to visual disturbances not fully explained by standard acuity or contrast measures.
- The Pulfrich phenomenon, a form of visual distortion, occurs when there's a delay in signal transmission between the two eyes.
Purpose of the Study:
- To investigate if unilateral cataract causes a pathological Pulfrich phenomenon.
- To quantify the effect and determine if it's reversible with cataract surgery.
Main Methods:
- 29 subjects with unilateral cataract underwent testing using a computer-generated pendulum and neutral density filters.
- A pathological Pulfrich effect was defined as perceived motion with zero filter strength.
- The effect's magnitude was measured by neutralizing filters, and 12 subjects were tested pre- and post-surgery.
Main Results:
- 20 of 29 subjects perceived the Pulfrich phenomenon.
- A significant pathological Pulfrich effect was observed preoperatively, resolving post-cataract extraction (p = 0.009).
- The median effect was equivalent to a 0.25 log unit filter; poorer visual acuity and stereoacuity correlated with inability to perceive the phenomenon.
Conclusions:
- Unilateral cataract is a cause of pathological Pulfrich phenomenon.
- This visual distortion may explain unexplained visual symptoms in unilateral cataract patients.
- The phenomenon is reversible upon cataract removal, highlighting its clinical relevance.