eccentric fixation
Eccentric fixation is the use of a non-foveal retinal area, known as the preferred retinal locus (PRL), for fixation instead of the central fovea. It occurs in conditions where the fovea is damaged or not being used effectively, such as macular degeneration, macular holes, or amblyopia. The PRL location can vary but is often in the upper or upper-left retinal area near the scotoma. Eccentric fixation allows the patient to utilize a healthier retinal region for fixation and maintain some visual function, though the PRL used may differ for different visual tasks.
electro-oculogram (EOG)
A technique that records eye movements and eye position by measuring the difference in electrical potential between electrodes placed on the skin around the eyes. Eye movements generate a corneo-retinal potential difference detected by the electrodes, with the EOG signal corresponding to the direction and amplitude of eye movements. EOG is used to study eye movement disorders, nystagmus, optokinetic responses, and can also assess retinal function. While non-invasive with high temporal resolution, it has limitations of low spatial resolution and potential signal artifacts.
epicanthus
A condition where a fold of skin partially covers the inner corner (canthus) of the eye. It is normal and common in infants but may give the appearance of an inward eye deviation (esotropia). In some cases, epicanthus can persist beyond infancy and be associated with craniofacial syndromes or genetic disorders. It can occur in isolation or combined with other features like increased distance between the inner canthi (telecanthus) or narrow palpebral fissures (blepharophimosis). Surgical correction may be considered if epicanthus causes functional or cosmetic concerns.
esophoria
Esophoria is a binocular vision condition where the eyes have a tendency to turn inward, especially when fusion is disrupted.
esotropia
A manifest inward turning of one or both eyes towards the nose. The deviation may be constant or intermittent, present from birth or acquired later in life, and can vary in angle depending on the direction of gaze.
exophoria
A binocular vision condition where the eyes have a tendency to turn outward, especially when fusion is disrupted.
Exotropia
A manifest turning of one or both eyes away from the nose. The deviation may be constant or intermittent, present from birth or acquired later in life, and can vary in angle depending on the direction of gaze.
extorsion (excyclodeviation)
The outward wheel-like rotation or torsional movement of the eye around its anteroposterior axis, causing the superior pole of the vertical meridian to rotate temporally. It often occurs due to imbalances in the actions of the oblique extraocular muscles.