Monocular and Binocular Temporal Visual Perception of Infantile Nystagmus

Abstract

duration, is defined as the point at which further stimulus presentation time does not contribute to enhanced performance 6,24. In some studies, critical duration refers to the time in which contrast sensitivity reaches 90% of the maximal value 24,25. Critical duration can be influenced by spatial and temporal parameters. Studies suggest that the period of temporal integration is affected by spatial frequency; the higher the spatial frequency is, the longer will be the time needed for integration 19. In the literature, the range of critical duration is between 160 and 200 19,26. In addition, critical duration can change as a result of cortical deprivation in cases such as amblyopia 27-31 or neurological disease 29. Nystagmus is a form of spontaneous oscillation of the eyes, which results in excessive motion of images on the retina, accompanied by poor vision including a reduction in visual acuity 32-35. In normal fixation, the eyes are not still; they move at a velocity of 3 minutes of arc in one second 36. Infantile nystagmus (IN) is accompanied by reduced vision in both eyes during the critical periods of life 37-39. The prevalence of infantile nystagmus is 1 to 1000-6000 34,35. The most common form of infantile nystagmus is afferent nystagmus; it is caused by impairment of central vision in early life, e.g., albinism or congenital cataract 35,40. Albinism is a heterogeneous group of congenital disorders affecting melanin synthesis. A few weeks after birth, nystagmus can appear in albino subjects 41. In research investigating nystagmus, albinos are one of the main participants 42-44. In addition, if efferent, it is an idiopathic nystagmus, without any involvement of ocular or systemic pathology. The onset is about 2-3 months after birth and it persists throughout life 45,46. In cases of nystagmus, contrast sensitivity is reduced 35,40,47-49. Vision impairment of cortical origin, such as amblyopia, is characterized by deficits in normal processing such as binocular summation and critical duration. In this study we investigated how binocular and monocular processing was affected in IN due to visual impairment. We hypothesized that in nystagmus, similarly to amblyopia, we would observe absent or diminished binocular summation from the two eyes, and that the critical duration differs from normal sighted vision.

Binocular summation is affected by crowding and tagging

“…Therefore, in our study we tested the effect of crowding on the binocular summation by calculating the sensitivity (d′) from the hit and false alarm parameters. We calculated the binocular summation as the ratio between the binocular d′ and the monocular d′ (the average of two eyes) (sensitivity ratio; d′ bino /d′ mono ), similar to previous studies that calculated the binocular summation as the ratio between the monocular to binocular contrast sensitivity 43 , 56 , 61 . We believe that this approach, rather than being based on the ratio of the percent correct, enables more direct comparisons with the previous studies.…”

“…Further work from our lab showed that two eyes are not always better than one. A recent study (2020) examined the spatial–temporal aspects of nystagmus perception, aiming to investigate the mechanisms underlying the deterioration of their visual performance under monocular and binocular conditions 56 . Subjects were asked to detect Gabor at different frequencies and presentation times.…”

Refractive Error in Juvenile Patients Presenting with Nystagmus at Tertiary Care Hospital of Karachi

“…There was more astigmatism in the albino (Albinism is inherited conditions in which there is a lack of pigmentation in the eyes and usually in the skin and hair as well) group (primarily with-the-rule; where the vertical meridian is steepest). 14 While In other study adolescent and adults myopic in albinos were less than idiopathic Congenital Nystagmus, [14][15][16][17][18][19][20] but in this recent study it no difference was found in type of refractive error result but study sample size was different. In our study only n=20 eyes were found hypermetric.…”

Crowding under scotopic and photopic vision in albino and normal-sighted participants

“…The lack of pigmentation results in anatomical structure deficiencies such as foveal hypoplasia (underdeveloped fovea 16 ), increased light sensitivity (photophobia), involuntary eye movements (nystagmus), and eyes misalignment (strabismus) in 53% of the cases 11 . These impairments contribute to reduced visual resolution, with visual acuity ranging between 6/18 and 6/120 and reduced contrast sensitivity 11 , 14 , 15 , 17 – 22 . In addition, studies have found that albinism has an amblyopia-like component affecting binocular vision and the symptoms accompanying their disease 22 – 24 .…”