Biomedical subjects

D Dowley

Publications and source records attributed to D Dowley.

4 recordsLinked to original sources

PubMed1990

Heterophoria.

With the large number of factors that contribute to the "position of rest" or fusion-free posture, it might be expected that heterophoria would be normally distributed. Data from a large sample of symptom-free subjects (N = 925) show that this is not so. Furthermore, the difference in the prism adaptation response in orthophoria, esophoria, and exophoria suggests that the presence of heterophoria in normal subjects is due to the partial saturation of prism adaptation.

Adaptation, Ocular↗

PubMed1990

Heterophoria and monocular occlusion.

Prism adaptation responses in orthophoric, exophoric and esophoric subjects are compared and found to be significantly different. Following a prolonged period of monocular occlusion the prism adaptation responses were compared, after occlusion the differences are no longer significant. This supports the theory that vergence (prism) adaptation is responsible for the existence of heterophoria. This paper shows that changes in heterophoria with monocular occlusion are caused by desaturation of prism adaptation.

Adaptation, Ocular↗

PubMed1989

Fixation disparity.

Fixation disparity may be a symptom of binocular stress or a purposeful error signal to drive vergence eye movements. Two similar units for detecting fixation disparity (Mallett and Sheedy units) are compared and evaluated. The Mallett unit was found to be more reliable, with similar readings in symptom-free subjects, whereas the Sheedy unit gave a larger spread of fixation disparity measurements and appears to be less useful than the Mallett unit for routine clinical use. The exact role of fixation disparity remains unresolved. Fixation disparity has two components in symptomatic subjects; the vergence signal component and an oculomotor imbalance component.

Adolescent↗

PubMed1987

The orthophorization of heterophoria.

The distribution of heterophoria within the general population is significantly non-normal and a high incidence of approximate orthophoria is observed. This observation has been named the orthophorization of heterophoria. It has been suggested that prism adaptation is the mechanism underlying orthophorization. A prolonged occlusion experiment has been used to investigate this possibility and further supports this theory.

Adaptation, Ocular↗