Sighting ocular dominance magnitude varies with test distance

Background

Ocular dominance can be defined as the preference of an individual for viewing with one eye over the other for particular visual tasks. It is relevant to monovision contact lens wear, cataract surgery and sports vision. Clinically, the measurement of ocular dominance is typically done at an arbitrary distance using a sighting test, such as the hole‐in‐card method that has a binary outcome. We investigated the effect of test distance on ocular dominance measured using a binocular sighting test that provided a continuous measurement of dominance.

Methods

Ten participants with normal binocular vision took part in this study. Their binocular sighting ocular dominance and phorias were measured at one, two, four, eight and 10 metres. During the dominance tests participants made a binocular alignment judgment and then were asked to indicate the relative alignment of each eye using a visual analogue scale as a reference.

Results

Eight participants had strong ocular dominance (five right, three left). For these participants, there was a significant increase in the magnitude of dominance with increasing test distance (p < 0.001). This could not be fully explained by changes in convergence demand. Two participants showed very weak ocular dominance across all test distances (p > 0.05), despite changes in convergence demand.

Conclusion

When ocular dominance is present, its magnitude varies significantly with test distance. This has significant implications for the accurate measurement of ocular dominance in the clinic and may reflect the neural processes that influence eye preference.

     

A healthy birth after intracytoplasmic sperm injection by using immotile testicular spermatozoa in a case with totally immotile ejaculated spermatozoa before and after Percoll gradients

Total asthenozoospermia is a severe problem, as only a micromanipulation technique can assist the couple, and even then fertilization and pregnancy rates are very low. The first healthy birth, achieved by using testicular immotile spermatozoa in a case with total asthenozoospermia before and after Percoll gradient preparation, is reported.      

Safety profile of parenteral ketamine and lignocaine infiltration in pediatric operations

OBJECTIVE: To study the safety and benefits of parenteral ketamine and lignocaine infiltration among pediatric surgical patients with co-morbidities that would preclude the use of general anesthesia requiring endotracheal intubation/face mask in a developing country. METHODS: This prospective study was undertaken at the Leadeks Medical Centre, Benin City Edo State, Nigeria between January 2002 and December 2006. Patients requiring surgery were safely operated even in the presence of co-morbidity. RESULTS: A total of 416 children were recruited and they were aged 6 days to 16 years (mean 12 -/+ 2.04 years) with a male/female ratio of 1:1.1. Appendectomy (33.2%), herniotomy (20.2%) and suturing of laceration (15.9%) were the most common indications for surgery. Anemia, upper respiratory tract infections, malnutrition, malaria fever, typhoid fever, and retroviral infections were co-morbidities. Ambulatory surgery was carried out in 48.6% patients. Overall, only 23.3% experienced postoperative pain, which was statistically significant in those that had laparotomy and appendectomy (p<0.0001), and analgesics such as paracetamol were enough to relieve the pain. Complications recorded such as postoperative vomiting, emergence reaction, wound infection, post operative fever, and apnea occurring after ketamine injections were tolerated and no mortality was recorded. CONCLUSION: The satisfactory anesthesia and analgesia recorded with this combination, and the low complications observed in the presence of co-morbidity showed that these agents have much to offer in a developing country.     

A review of proximal inputs to the near response

Maddox proposed that the perceived nearness of a target could influence the ocular vergence response. Proximal inputs have been used to refer to all static and dynamic cues to depth other than disparity and blur. In this paper, we review a number of studies in which proximal influences have been assessed. While general agreement exists that proximal contributions are significant when blur and disparity cues are absent (open‐loop conditions), there are conflicting reports on the role of proximal vergence and accommodation under closed‐loop conditions.     

Lack of spatial remapping of the visual field surrounding a monocular scotoma

Background: Changes in cortical receptive fields following deafferentation raise the question of whether interruption of optic nerve fibres engenders spatial distortion in the region bordering the resulting scotoma. Methods: The regularity and uniformity of the spatial metric surrounding a monocular Bjerrum scotoma were studied in both the affected and unaffected eyes of a glaucoma patient, using rigorous psychometric measurements and Amsler grid observations. Results: No expansion of distances towards the edge of the scotoma was found; however, such a change occurs at the border of the normal blind spot, though not binocularly and not in the corresponding field of the other eye. Conclusion: The findings argue against cortical reorganisation following monocular retinal deafferentation in the adult.     

Stereoacuity with balanced presbyopic contact lenses

Background: To evaluate near stereoacuity with the balanced Proclear Multifocal simultaneous vision contact lens. Methods: Twenty‐five presbyopic subjects were fitted binocularly with the Proclear Multifocal contact lens and with distance contact lenses combined with reading spectacles, which served as controls. After one month, stereoacuity was measured using the vectographic Titmus and Random dot stereotests and the Howard‐Dolman (HD) apparatus under photopic conditions (85 cd/m²) at 40 cm. Binocular high‐contrast visual acuities (BHCVA) at distance and near were examined. Results: For the multifocal group, mean stereoacuity with the Howard‐Dolman method was 22.40 ± 8.23 seconds of arc. Using the Titmus and the Random dot sterereotests, the values were 56.40 ± 18.00 and 54.80 ± 20.23 seconds of arc, respectively. For the SCL group, mean stereoacuities were 19.9 ± 4.6, 51.2 ± 16.4 and 51.2 ± 20.88 seconds of arc, with the Howard‐Dolman, Titmus and the Random dot, respectively. There were no statistically significant differences among groups for Howard‐Dolman (p = 0.07), Titmus (p = 0.10) and Random dot (p = 0.17) stereotests. No statistically significant differences were found between the Titmus and the Random dot stereotest values (multifocal group: p = 0.30 and SCL group: p = 0.50), however, these values differ significantly from those found using the Howard‐Dolman method for both groups (p < 0.001). For the multifocal group, BHCVA was ?0.007 ± 0.060 and 0.012 ± 0.063 logMAR for distance and near vision, respectively. For the SCL group, these values were ?0.02 ± 0.05 and ?0.01 ± 0.06 logMAR, for distance and near vision, respectively. Comparing both groups there were no statistically significant differences between groups for either distance (p = 0.08) or near (p = 0.09). Conclusions: The Proclear Multifocal contact lens provided good distance and near visual acuity preserving stereopsis. Multifocal optics with one lens biased to distance viewing and the other lens biased toward near viewing minimally affects stereoacuity.     

Craniofacial and dental development in cardio‐facio‐cutaneous syndrome: the importance of Ras signaling homeostasis

Cardio‐facio‐cutaneous syndrome (CFC) is a RASopathy that is characterized by craniofacial, dermatologic, gastrointestinal, ocular, cardiac, and neurologic anomalies. CFC is caused by activating mutations in the Ras/mitogen‐activated protein kinase (MAPK) signaling pathway that is downstream of receptor tyrosine kinase (RTK) signaling. RTK signaling is known to play a central role in craniofacial and dental development, but to date, no studies have systematically examined individuals with CFC to define key craniofacial and dental features. To fill this critical gap in our knowledge, we evaluated the craniofacial and dental phenotype of a large cohort (n = 32) of CFC individuals who attended the 2009 and 2011 CFC International Family Conferences. We quantified common craniofacial features in CFC which include macrocephaly, bitemporal narrowing, convex facial profile, and hypoplastic supraorbital ridges. In addition, there is a characteristic dental phenotype in CFC syndrome that includes malocclusion with open bite, posterior crossbite, and a high‐arched palate. This thorough evaluation of the craniofacial and dental phenotype in CFC individuals provides a step forward in our understanding of the role of RTK/MAPK signaling in human craniofacial development and will aid clinicians who treat patients with CFC.