ABSTRACT
We present a new efficient method to find the Ising problem partition function for finite lattice graphs embeddable on an arbitrary orientable surface, with integral coupling constants bounded in the absolute value by a polynomial of the size of the lattice graph. The algorithm has been implemented for toroidal lattices using modular arithmetic and the generalized nested dissection method. The implementation has substantially better performance than any other as far as we know.
ABSTRACT
The blue field entoptic test was applied to study macular function in 32 patients with severe ocular trauma and markedly reduced visual acuity (6/60 [20/200] or less) in whom fundus details could not be seen initially. This test is based on the entoptic phenomenon, whereby one can observe one's own leukocytes flowing in the perifoveal retinal capillaries. Twenty of the 21 patients (95%) with normal perception of the corpuscles regained a visual acuity of 6/12 (20/40) or better on follow-up, whereas ten of the 11 patients (91%) with abnormal test responses had, on follow-up, a visual acuity of counting fingers or less. The blue field entoptic test is therefore useful in prognosticating macular function in patients with reduced visual acuity due to media opacities secondary to ocular trauma.
Subject(s)
Eye Injuries/complications , Macula Lutea/physiopathology , Retinal Diseases/diagnosis , Vision Tests/methods , Adolescent , Adult , Aged , Child , Humans , Middle Aged , Vision, Entoptic , Visual AcuityABSTRACT
The blue field entoptic phenomenon (BFE), which allows the observation of one's own leukocytes flowing in macular retinal capillaries, was used to predict postoperative macular function in 136 consecutive patients undergoing uncomplicated cataract operation. The results were compared to those obtained with three commonly used tests: two-light discrimination, color perception, and the Purkinje vascular entoptic phenomenon. All four tests identified a nearly equal number of the good maculae (visual acuity 20/40 of better) ranging from 87% for the two-light discrimination test to 94% for the BFE test. However, the tests varied greatly in predicting poor macular function (visual acuity 20/50 or worse). The BFE test identified more than 75% of the poor maculae; the Purkinje vascular entoptic test and the two-light discrimination test, only 22%; and the color perception test, 11%. A positive response to the BFE test indicated a .98 probability of good macular function; a negative response indicated a .82 probability of poor macular function, predictions that were better than the other three tests or their combination.
Subject(s)
Cataract/physiopathology , Macula Lutea/physiopathology , Vision Tests , Vision, Entoptic , Vision, Ocular , Visual Acuity , Cataract Extraction , Color Perception , Discrimination, Psychological , Humans , Leukocytes/physiology , Prognosis , Retinal VesselsSubject(s)
Glaucoma/diagnosis , Intraocular Pressure , Glaucoma/physiopathology , Glaucoma/therapy , Humans , Visual FieldsSubject(s)
Cataract/physiopathology , Light , Vision Tests/methods , Adolescent , Adult , Age Factors , Aged , Humans , Leukocytes , Macular Degeneration/diagnosis , Middle Aged , Vision Tests/instrumentationABSTRACT
The entoptic phenomenon of the flying corpuscles (FLC) consists of the perception of one's own leukocytes flowing in the perifoveal capillaries. A method has been developed to investigate the type of motion of the FLC, their relative number and speed, and their distribution over the central visual field. The results in 38 patients with disease affecting the macula correlated well with the clinical findings obtained by ophthalmoscopy, visual field tests, and fluorescein angiography. The test is noninvasive, inexpensive, easy to perform, and provides information on the perifoveal retinal circulation and on macular function.
Subject(s)
Capillaries , Macula Lutea/physiopathology , Photoreceptor Cells/blood supply , Retinal Vessels/physiopathology , Vision, Entoptic/physiology , Vision, Ocular/physiology , Adolescent , Adult , Aged , Cell Movement , Female , Humans , Leukocytes/physiology , Male , Microcirculation , Middle Aged , Regional Blood Flow , Retinal Diseases/diagnosis , Retinal Diseases/physiopathology , Visual Acuity , Visual FieldsABSTRACT
Fluorescein angiograms of the optic disc were studied in 23 normal and 29 ocular hypertensive eyes. Significant differences in the frequency distributions of areas of defects were obtained between normal and ocular hypertensive eyes. Increased areas of filling defects were noted in ocular hypertensive eyes as compared to normals. There were also significant correlations of the areas of filling defects with age and systolic blood pressure in the ocular hypertensive eyes that were not present in the normals. These observations support the concept that fluorescein angiography of the optic disc demonstrates localized areas of impaired circulation that increase with ocular pressure, age, and systolic blood pressure. This technique may be useful in separating normal from the ocular hypertensive patient who shows changes in the circulation of the optic disc with increased ocular pressure.
Subject(s)
Fluorescein Angiography , Intraocular Pressure , Optic Disk/pathology , Adolescent , Adult , Age Factors , Aged , Child , Female , Humans , Male , Middle AgedABSTRACT
The entoptic phenomenon by which one can observe leukocytes flowing in one's own parafoveal capillaries has been used to study the effect of changes in perfusion pressure on blood flow. Our measurements in humans with normal ocular fundi indicate that the retinal circulation of the parafovea is autoregulated in relation to perfusion pressure. The average time lag between a change in blood flow and the beginning of the autoregulatory response was about 46 sec., and the average duration of this response was about 48 sec. At the end of the autoregulatory response, the vascular resistance of the parafoveal segment was about 50% lower than that at normal intraocular pressure.
