Sample records for aniseikonia
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Aniseikonia quantification: error rate of rule of thumb estimation.
Lubkin, V; Shippman, S; Bennett, G; Meininger, D; Kramer, P; Poppinga, P
1999-01-01
To find the error rate in quantifying aniseikonia by using "Rule of Thumb" estimation in comparison with proven space eikonometry. Study 1: 24 adult pseudophakic individuals were measured for anisometropia, and astigmatic interocular difference. Rule of Thumb quantification for prescription was calculated and compared with aniseikonia measurement by the classical Essilor Projection Space Eikonometer. Study 2: parallel analysis was performed on 62 consecutive phakic patients from our strabismus clinic group. Frequency of error: For Group 1 (24 cases): 5 ( or 21 %) were equal (i.e., 1% or less difference); 16 (or 67% ) were greater (more than 1% different); and 3 (13%) were less by Rule of Thumb calculation in comparison to aniseikonia determined on the Essilor eikonometer. For Group 2 (62 cases): 45 (or 73%) were equal (1% or less); 10 (or 16%) were greater; and 7 (or 11%) were lower in the Rule of Thumb calculations in comparison to Essilor eikonometry. Magnitude of error: In Group 1, in 10/24 (29%) aniseikonia by Rule of Thumb estimation was 100% or more greater than by space eikonometry, and in 6 of those ten by 200% or more. In Group 2, in 4/62 (6%) aniseikonia by Rule of Thumb estimation was 200% or more greater than by space eikonometry. The frequency and magnitude of apparent clinical errors of Rule of Thumb estimation is disturbingly large. This problem is greatly magnified by the time and effort and cost of prescribing and executing an aniseikonic correction for a patient. The higher the refractive error, the greater the anisometropia, and the worse the errors in Rule of Thumb estimation of aniseikonia. Accurate eikonometric methods and devices should be employed in all cases where such measurements can be made. Rule of thumb estimations should be limited to cases where such subjective testing and measurement cannot be performed, as in infants after unilateral cataract surgery.
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Measuring aniseikonia using scattering filters to simulate cataract
Wilson, Jason
2011-12-01
The relationship between anisometropia and aniseikonia (ANK) is not well understood. Ametropic cataract patients provide a unique opportunity to study this relationship after undergoing emmetropizing lens extraction. Because light scatter may affect ANK measurement in cataract patients, its effect should also be evaluated. The Basic Aniseikonia Test (BAT) was evaluated using afocal size lenses to produce specific changes in retinal height. Several light scattering devices were then evaluated to determine which produced effects most similar to cataract. Contrast sensitivity and visual acuity (VA) losses were measured with each device and compared to those reported in cataract. After determining the most appropriate light scattering device, twenty healthy patients with normal visual function were recruited to perform the BAT using the filters to simulate cataract. Cataract patients were recruited from Vision America and the University of Alabama at Birmingham School of Optometry. Patients between 20 and 75 years of age with at least 20/80 VA in each eye, ≥ 2D ametropia, and normal binocular function were recruited. Stereopsis and ANK were tested and each patient completed a symptom questionnaire. ANK measurements using afocal size lenses indicated that the BAT underestimates ANK, although the effect was minimal for vertical targets and darkened surroundings, as previously reported. Based on VA and contrast sensitivity loss, Vistech scattering filters produced changes most similar to cataract. Results of the BAT using Vistech filters demonstrated that a moderate cataract but not a mild cataract may affect the ANK measurement. ANK measurements on cataract patients indicated that those with ≥ 2 D ametropia in each eye may suffer from induced ANK after the first cataract extraction. With upcoming healthcare reform, unilateral cataract extraction may be covered, but not necessarily bilateral, depending on patient VA in each eye. However, a questionnaire about symptoms
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[IOL and aniseikonia calculation combined with documentation of surgical data and IOL inventory].
Bastian, G O; Hiss, P
1992-08-01
The exact recording of operation data is a precondition for keeping the standards high in cataract surgery, but surgeons are reluctant to answer a questionnaire after a strenuous operation. We have designed a program easy to use in the Macintosh Hypercard System that covers all aspects of cataract surgery such as: (1) the operating record; (2) a data sheet for recording the various details of the operation; (3) recording of the data on hard disc; (4) managing the IOL stock list; (5) proposal of IOL models that are in stock with regard to IOL power (SRK2) and aniseiconia. This program enables the surgeon to record the operation data with effortless ease and it is well accepted. There is no dictation. The operating record and data sheet are printed immediately. The program is controlled by a "mouse". Selection of the suitable IOL model is facilitated by the link between the calculation of IOL power and the IOL stock list. In special cases the IOL power can be changed to obtain less aniseiconia.
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How best to assess suppression in patients with high anisometropia.
Li, Jinrong; Hess, Robert F; Chan, Lily Y L; Deng, Daming; Chen, Xiang; Yu, Minbin; Thompson, Benjamin S
2013-02-01
We have recently described a rapid technique for measuring suppression using a dichoptic signal/noise task. Here, we report a modification of this technique that allows for accurate measurements to be made in amblyopic patients with high levels of anisometropia. This was necessary because aniseikonic image size differences between the two eyes can provide a cue for signal/noise segregation and, therefore, influence suppression measurement in these patients. Suppression was measured using our original technique and with a modified technique whereby the size of the signal and noise elements was randomized across the stimulus to eliminate size differences as a cue for task performance. Eleven patients with anisometropic amblyopia, five with more than 5 diopters (D) spherical equivalent difference (SED), six with less than 5 D SED between the eyes, and 10 control observers completed suppression measurements using both techniques. Suppression measurements in controls and patients with less than 5 D SED were constant across the two techniques; however, patients with more than 5 D SED showed significantly stronger suppression on the modified technique with randomized element size. Measurements made with the modified technique correlated with the loss of visual acuity in the amblyopic eye and were in good agreement with previous reports using detailed psychophysical measurements. The signal/noise technique for measuring suppression can be applied to patients with high levels of anisometropia and aniseikonia if element size is randomized. In addition, deeper suppression is associated with a greater loss of visual acuity in patients with anisometropic amblyopia.
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Directory of Open Access Journals (Sweden)
Edith María Ballate Nodales
1999-12-01
Full Text Available Con el auge de las numerosas técnicas microquirúrgicas de la catarata, se hizo necesario un estudio detallado de todos los aspectos que llevan a un perfeccionamiento de la técnica apoyándonos en métodos computadorizados. Así se crea en nuestro servicio el Programa para el Perfeccionamiento de la Microcirugía Ocular, denominado SIPMO para el cálculo del astigmatismo residual y la evolución de la aniseiconía en pacientes con lente intraocular implantado (LIO. Estos resultados se registraron en una base de datos con posibilidades de estudios retrospectivos. Esta técnica contribuye a elevar la calidad científico-técnica de los residentes de la especialidad, profundiza sus conocimientos y habilidades prácticas y permite además, evaluar los resultados individuales y colectivos de nuestro servicio por métodos computadorizados. El programa se encuentra a disposición de cualquier oftalmólogo o institución docente que desee utilizarlo.The rise of many microsurgical techniques for cataract made the detailed study of all aspects leading to technique improvement necessary, based on computerized method. Thus, the Ocular Microsurgery Improvement Program called SIPMO was created in our service for calculating residual astigmatism and for the evolutin of aniseikonia in patients with implanted intraocular lens (IOL. These results were recorded in a database having possibilities of retrospective studies. This technique contributes to raise the technical-scientific quality of the residents in this field, to deepen their knowledge and increase their practical abilities and additionally, it serves to evaluate individual and collective results of our services by computarized methods. The program is at the disposal of any ophtalmologist or any teaching institution thay may wish to use it.
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Magnifications of Single and Dual Element Accommodative Intraocular Lenses: Paraxial Optics Analysis
Ale, Jit B; Manns, Fabrice; Ho, Arthur
2010-01-01
the translation (or the achieved accommodative amplitude) are important parameters in determining the magnifications of the AIOLs. The results highlight the need for caution in the prescribing of AIOL. Aniso-accommodation or inter-ocular differences in AIOL designs (or relative to the natural lens of the contralateral eye) may introduce dynamic aniseikonia and consequent impaired binocular vision. Nevertheless, some designs, offering greater increases in magnification on accommodation, may provide enhanced near vision depending on patient needs. PMID:21054469