(n.) A defect of the eye or of a lens, in consequence of which the rays derived from one point are not brought to a single focal point, thus causing imperfect images or indistinctness of vision.
Example Sentences:
(1) The authors have presented in two previous articles the graphic solutions resembling Tscherning ellipses, for spherical as well as for aspherical ophthalmic lenses free of astigmatism or power error.
(2) The high incidence of infant astigmatism has implications for critical periods in human visual development and for infant acuity.
(3) The most frequently occurring signs were: tilting of the disc (89%), oblique direction of the vessels (89%) and myopic astigmatism (96%).
(4) There was no evidence of glaucoma in any of the patients although two patients exhibited keratoconus and another one manifested moderate to high astigmatism.
(5) Of 809 eyes that underwent the Kelman phacoemulsification and aspiration (KPE) procedure, we report on 4 patients (0.49%) who developed sudden against-the-rule (AR) astigmatism after intraocular lens implantation.
(6) The two last methods are used for correction of astigmatism.
(7) The eyes were compared to 105 control eyes in which no astigmatic incisions were performed to assess the estimated effect of the TAK incisions.
(8) The choice of the method depends on the kind and degree of astigmatism and the degree of the spherical ametropia of the operated eye.
(9) The change in refractive astigmatism was as high as 1.50DC (diopter cylinder).
(10) The endpoint for the procedure is corneal astigmatism that will allow either spectacle or contact lens correction, depending on the patient's visual needs.
(11) A total of 527 astigmatic patients were examined for their axial distribution.
(12) Astigmatism greater than +1.25 diopters (as high as +5.50 diopters) was most commonly associated with dacryoceles (eight of 12 eyes) and with hemangiomas (14 of 17 eyes).
(13) In terms of the various keratometry values compared, mean K (corneal refractive power), flattest K, steepest K, astigmatism and the axis of astigmatism, 65% to 75% of the cases on automated keratometry were within 0.26 dioptres or 11 degrees of manually determined values; the difference was statistically significant (p < 0.001).
(14) Young adulthood myopia progression also appeared to be accompanied by a slight tendency toward a with-the-rule astigmatic shift.
(15) Forty-nine cases of primary keratophakia and 13 cases of secondary keratophakia were analyzed for postoperative astigmatism.
(16) A numerical example reveals some lesser known properties of the circle of least confusion of astigmatic pencils.
(17) Group II includes 10 patients with astigmatism due to circumscribed peripheral limbal corneal dystrophy.
(18) Amblyopia was due to anisometropia in 24 cases (50%), strabismus in 9 cases (18.7%), high astigmatism (meridional) in 7 cases (14.5%) and other causes or a combination of factors in 8 cases (16.7%).
(19) The differences between the 2 eyes were not statistically significant so far as the amount of astigmatism, final visual acuity, and peripheral anterior synechiae were concerned.
(20) Results showed that the wearing of spherical soft contact lenses, such as those used in this study, cannot be expected to predictably mask astigmatism.
Presbyopia
Definition:
() A defect of vision consequent upon advancing age. It is due to rigidity of the crystalline lens, which produces difficulty of accommodation and recession of the near point of vision, so that objects very near the eyes can not be seen distinctly without the use of convex glasses. Called also presbytia.
Example Sentences:
(1) The most common eye disease are cataract, refractive error and presbyopia, and diseases of the conjunctiva and sclera.
(2) In addition some individuals (7%) were found to develop early presbyopia.
(3) Their use for presbyopia, aphakia, and glaucoma is considered.
(4) Both the decrease in retinal illumination and the presbyopia accounted for only a trivial proportion of the acuity loss.
(5) Detailed understanding of these mechanisms and the environmental, dietary, and behavioural factors that may influence the development of presbyopia will require controlled studies and, in some cases, invasive experimental manipulations that can only be achieved through the use of an animal model.
(6) Diagnostic standards have a big practical importance in the ophthalmological geriatrics above all in glaucoma, apart from the presbyopia, which depends to the age in a big way.
(7) Complications, such as scarring from intersecting keratotomy incisions, irregular astigmatism resulting from multiple reoperations, and overcorrections with the attendant early onset of symptomatic presbyopia are becoming much less frequent.
(8) The results are described of a 10-year study of the longitudinal changes in the static response of an individual subject during the approach to absolute presbyopia.
(9) They present a variable refractive index which can be used to produce the necessary addition needed for presbyopia.
(10) The history of prostheses for presbyopia is reviewed with an account of the development of variable focus spectacles.
(11) All forms of ophthalmic correction for presbyopia require compromises in viewing flexibility and visual function.
(12) A 33-year-old white man developed premature presbyopia and anisocoria as initial manifestations of acute pandysautonomia.
(13) The corneoscleral incision could be made even smaller, the lens diaphragm would be conserved more physiologically, and a method of therapy for presbyopia might eventually be possible.
(14) The resulting data indicate significantly lower best-corrected distance visual acuities, a greater prevalence of many ocular pathologies, less frequent occurrence of myopia, and an earlier onset of presbyopia than is found in the general United States population.
(15) Is it true that environmental UVR is also the prime contributor in the deleterious lenticular changes that may begin with premature presbyopia, as has been postulated?
(16) The age at onset of presbyopia showed a slightly higher rate of concordance in the MZ than in the DZ pairs.
(17) Monovision, the use of a monocular addition for near viewing, is a clinical technique sometimes used to correct presbyopia.
(18) The genetic and environmental contributions to physical aging (hair graying, balding, presbyopia) and longevity (age at death) were examined by within-pair comparison in monozygotic (MZ) and dizygotic (DZ) twins in later adulthood.
(19) Presbyopia, cataract, and glaucoma are some of the visual constraints that may play an important role in making it difficult for the person to read the informed consent form.
(20) We have conducted two experiments to investigate the effect of monovision and other contact lens corrections for presbyopia upon peripheral visual acuity.