PubMed · 13084995
The source did not provide an abstract. Follow the original record for more information.
Explore connections, maps & timelines
H M BURIAN. 1953. Convergence insufficiency.. https://pubmed.ncbi.nlm.nih.gov/13084995/
Cite the original work for its findings. Save a collection to share your selection of sources.
KEEP EXPLORING
BACKGROUND: Photorefraction can be carried out in both eyes simultaneously from a distance and is therefore suitable for examination of children. This study evaluated the accuracy of a commercially available photo-refractometer (Power Refractor, Plusoptix, Erlangen, Germany) and investigated whether the working distance relaxes the accommodation sufficiently without cycloplegia. METHODS: Photo-refractometer readings were compared to cycloplegic retinoscopy. Because of the limited working range the group of patients consisted of low and moderate ametropic eyes within a spherical power of -7.0 to +5.0 D. One hundred and ninety-two eyes from 104 patients (2-81 years) were photo-refracted under cycloplegia. A subgroup of 83 eyes from 46 patients was additionally refracted without cycloplegia. RESULTS: Under cycloplegia, the Power Refractor measured the spherical equivalent slightly below that of cycloplegic retinoscopy (too much minus). The mean difference in spherical equivalent was -0.12+/-0.91 D (SD). The mean difference of cylindrical power was -0.17+/-0.73 D. The mean weighted axis difference was 0.61+/-0.71 D which is comparable to an axis deviation of 18 degrees at a cylinder power of 1.00 D. Without cycloplegia, the mean difference of the spherical equivalent was -0.73+/-1.25 D. The mean difference of cylindrical power was -0.20+/-0.65 D. The mean weighted axis difference was 0.44+/-0.58 D which is comparable to an axis deviation of 13 degrees at a cylinder power of 1.00 D. CONCLUSIONS: Without cycloplegia, the spherical equivalent of the Power Refractor tends to be underestimated due to uncontrolled accommodation, especially in children. Cycloplegia improves the accuracy in evaluating the spherical equivalent, but decreases the accuracy of cylinder power and axis.
PURPOSE: The principal ability of potentially accommodative IOLs is based on an axial shift of the IOL optics induced by the ciliary body action in interaction with a reversible change in haptic angulation. The aim of this study was to investigate the accommodative performance of this new IOL generation. METHOD: The authors have designed a test device to study IOL performance experimentally. These results were extrapolated to the in vivo situation in patients with accommodative implants. RESULTS: The 3D high-resolution presentation of the anterior segment of the eye allows a separation of the IOL haptic elements. In vitro and in the selected in vivo cases a change in haptic angulation <10 degrees in combination with a maximal IOL shift of 0.5 mm was found. CONCLUSIONS: The simulation model used in combination with 3D ultrasound biomicroscopy provides information about the potential of accommodative IOL designs. Conclusions corresponding to changes in haptic angulation during accommodation can be drawn and applied to the in vivo situation.
Experiments were undertaken to understand the relationship between dynamic accommodative refractive and biometric (lens thickness (LT), anterior chamber depth (ACD) and anterior segment length (ASL=ACD+LT)) changes during Edinger-Westphal stimulated accommodation in rhesus monkeys. Experiments were conducted on three rhesus monkeys (aged 11.5, 4.75 and 4.75 years) which had undergone prior, bilateral, complete iridectomies and implantation of a stimulating electrode in the Edinger-Westphal (EW) nucleus. Accommodative refractive responses were first measured dynamically with video-based infrared photorefraction and then ocular biometric responses were measured dynamically with continuous ultrasound biometry (CUB) during EW stimulation. The same stimulus amplitudes were used for the refractive and biometric measurements to allow them to be compared. Main sequence relationships (ratio of peak velocity to amplitude) were calculated. Dynamic accommodative refractive changes are linearly correlated with the biometric changes and accommodative biometric changes in ACD, ASL and LT show systematic linear correlations with increasing accommodative amplitudes. The relationships are relatively similar for the eyes of the different monkeys. Dynamic analysis showed that main sequence relationships for both biometry and refraction are linear. Although accommodative refractive changes in the eye occur primarily due to changes in lens surface curvature, the refractive changes are well correlated with A-scan measured accommodative biometric changes. Accommodative changes in ACD, LT and ASL are all well correlated over the full extent of the accommodative response.