(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.
Emmetropia
Definition:
(n.) That refractive condition of the eye in which the rays of light are all brought accurately and without undue effort to a focus upon the retina; -- opposed to hypermetropia, myopia, an astigmatism.
Example Sentences:
(1) Of the adult aphakic cases, 80% were within 3 diopters of emmetropia at six months, with four cases showing an undercorrection.
(2) Seventy-three percent of the patients were within 3 diopters of emmetropia after surgery.
(3) We analyzed 450 consecutive cases of intraocular lens implantation (omitting only two inadvertent implantations in patients with high myopia) to determine the dioptric lens power in each case required to produce emmetropia.
(4) Fifty percent were within 2 diopters (D) of emmetropia and 92% within 3 D. All pediatric aphakic patients showed an improvement in best-corrected acuity, and 83% of eyes at 6 months were within 2 D of emmetropia; by 1 year a 3.4-D average myopic shift had occurred.
(5) At the time of entry into the USAF, refractive error data were clustered around emmetropia with a definite skew toward hyperopia.
(6) Twenty-one out of 43 eyes achieved refractive errors within 2 diopters (D) of emmetropia.
(7) The postoperative refraction and actually implanted IOL power were used to determine the IOL power needed for emmetropia.
(8) Eighty-three percent of eyes receiving intraocular lenses were within 2 D of emmetropia.
(9) The eyes of neonates grow from ametropia (refractive error) toward emmetropia.
(10) Further analysis demonstrated that results of unaided acuity and proximity to emmetropia were much better for low (< -2.87 D) and moderate (-3.0 to -5.87 D) than for high (> -6.0 D) myopes.
(11) Refraction showed 61.3% to be within 1 dioptre of emmetropia and 86.7% were within 2 dioptres.
(12) Although the optic-nerve-sectioned eye can sense the sign of a refractive error and initially adjust growth accordingly, it eventually overshoots emmetropia and reverses the sign of the initial refractive error.
(13) Contrary to previous reports, we do not find consistent high hyperopia in the rat, but rather refractions that range from near emmetropia (-0.12 D) to extreme hyperopia (+18.95 D).
(14) The predicted postoperative refraction was more accurate by modified SRK formulae, especially between emmetropia and myopia up to 0.5 diopters.
(15) The data are valuable to the intraocular lens surgeons, in that they demonstrate the range and frequency of intraocular lens powers needed to achieve emmetropia in a large population sample.
(16) At three years after surgery, 58% of eyes had refractive error within one diopter of emmetropia; 26% were undercorrected, and 16% were overcorrected by more than one diopter.
(17) Use of mean values in a theoretic artificial intraocular lens power equation suggests that aphakic dogs require an implant of approximately 40 diopters to achieve emmetropia.
(18) Multiple regression analysis was employed to estimate the amount of preoperative correction required to achieve emmetropia in 129 spherical radial keratotomy procedures.
(19) Three of 14 younger patients and 35 of 54 older patients were within 3 D of emmetropia.
(20) There was continuous changing of refraction towards emmetropia in all refraction groups.