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At least 37 records · Page 2Linked to original sources
PubMed1992

Retinoscopic measurement of the refractive state of the rat.

Using retinoscopy, we measured the refractive state of 96 eyes of three different strains of rats: albino Sprague-Dawley, Royal College of Surgeons (RCS) with and without inherited retinal dystrophy, and lean and obese varieties of Zucker rats. 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). This range of refractive errors suggests a poorly developed emmetropization mechanism in the rat, and that individual refractions should be performed on animals utilized in experiments where refractive state is critical.

Albinism, Ocular↗
PubMed2006

Retinoscopic (refractive) estimation of axial length in paediatric aphakia: a comparison with ultrasonic measurement.

AIM: To compare paediatric axial length values estimated from the aphakic refraction alone with axial length values measured by ultrasound. METHODS: Retrospective institutional medical record review of paediatric aphakic patients 12 years of age and younger with documented ultrasonic axial length and objective refraction (retinoscopy) within 3 months of each other. An estimate of axial length was made from the aphakic refraction alone (with an assumed average keratometry value of 44 dioptres) for all patients. RESULTS: 149 eyes of 102 paediatric aphakic patients were identified. The ultrasonic axial length values (mean 22.47 mm, SD 1.69, 95% confidence interval (CI) 0.27) and estimated axial length values (mean 22.41 mm, SD 1.53, 95% CI 0.25) had an average difference of 0.05 mm (SD 1.04, 95% CI 0.17) and were not significantly different (p = 0.56) by the two tailed paired t test. A histogram of the differences that did exist between the two values resembled a normal distribution. The nine eyes with the largest differences between the two values had either low hyperopic aphakic refractions or abnormal average keratometry values. CONCLUSIONS: There was no significant difference between the two groups of axial length values, and the distribution of differences that did exist seemed random. The greatest differences between the two values occurred in longer (less hyperopic) eyes and in eyes with abnormally steep or flat keratometry. Estimation of axial length from the aphakic refraction alone seems to be a useful technique in the average paediatric eye, especially if biometry is unavailable.

Adolescent↗
PubMed1987

IOL power determination by retinoscope.

IOL power prediction was performed by streak retinoscopy on the operating table after taking the previous refractive status of the patient into consideration. In 180 eyes posterior chamber lenses were implanted after determining the power of the IOL by retinoscopy on the table and selecting a suitable lens. The method though not so accurate as A scan ultra sonography and use of the SRK formula and the Colebrander formula is a good substitute to these methods particularly for avoiding high post operative refractive errors.

Eyeglasses↗
PubMed2004

Sources of normal and anomalous motion in retinoscopy.

PURPOSE: Besides the classic "with," "against," and "neutral" absence of motion, retinoscopic reflexes can display anomalous "with" motion in myopia. A model is presented that explains the source of this anomalous motion, as well as quantifies the appearance of retinoscopic motion in myopia and hyperopia. METHODS: Various 2 x 2 matrices were created to describe schematic eyes for a +20 D trial lens, a Gullstrand #1 schematic eye, and an infant schematic eye. Rays from the retinoscope were traced paraxially through these matrices over a full transit of the retinoscope beam across the pupil. Retinal position of the edge of the reflex visible to the observer was plotted as a function of pupil sizes from 2 mm to 16 mm for -5.00 D and +2.00 D refractive errors for the +20 D trial lens. RESULTS: The edge of the retinoscopic reflex could be formed by one of two sources: the edge of the retinoscope beam itself, or the shadow cast by the beam against the edge of the pupil. Anomalous "with" motion arose in myopia when the edge of the reflex was formed by the edge of the beam. The edge of the beam was also visible in hyperopia but did not create anomalous motion. The retinoscope peephole was not involved in the formation of the edge of the reflex. The degree of anomalous motion increased with greater myopia and pupil size. Measured pupil sizes needed to completely eliminate anomalous motion agreed well with those predicted by the model, except at the largest pupil sizes. The limit for anomalous motion depended only on pupil size, refractive error, and working distance but not on whether the system matrix represented the trial lens, a Gullstrand #1 eye, or an infant eye. CONCLUSIONS: Seeing the edge of the beam at large pupil sizes during retinoscopy creates anomalous "with" motion in myopia but may make the reflex easier to see in hyperopia. Anomalous "with" motion in myopia can be managed by adjustment of pupil size, working distance, or net corrected refractive error. Aside from possible effects of aberrations, retinoscopic motion appears to be consistent across various paraxial optical systems for a given refractive error and pupil size.

Artifacts↗
PubMed1987

A teaching attachment for retinoscopy.

A teaching attachment for a conventional streak retinoscope allows a second observer to view the retinoscopic reflex during retinoscopy. The device weighs 200 grams and is attached to the retinoscope by a semi-flexible, rotatable linkage. A beam splitter, one-power telescope, and erecting mirror form a displaced aerial image of the retinoscope peephole for the observer. With identical retinoscopic reflexes observed through the actual peephole and its aerial image, the device can be used to teach basic retinoscopy techniques to new refractionists, or to demonstrate subtle reflexes to more experienced observers.

Equipment Design↗
PubMed2006

Evaluation of the accuracy of estimation retinoscopy.

BACKGROUND: Some children are unable to cooperate for retinoscopy because they object strongly to the placement of lenses close to their faces. For these children, it would be ideal to obtain an accurate estimate of refractive error without using lenses. Techniques of estimation retinoscopy include sliding the sleeve of the Copeland retinoscope downward or moving closer to the patient until neutrality is achieved. The purpose of this study was to evaluate the accuracy of estimation techniques by comparing results to standard retinoscopy with loose lenses in cooperative children. METHODS: A Copeland retinoscope was calibrated using a schematic eye and loose lenses. A scale was created adjacent to the sleeve of the retinoscope which allowed an estimate of refractive error based on the position of the top of the sleeve. Estimation retinoscopy followed by standard retinoscopy with loose lenses was done on 100 eyes of 50 children after cycloplegia. RESULTS: Estimation of spherical equivalent for myopia less than 4 D and hyperopia less than 2 D correlated strongly with results obtained by standard retinoscopy with loose lenses (r = 0.87). Estimation retinoscopy had a sensitivity of 88%, specificity of 67%, positive-predictive value of 58%, and negative-predictive value of 92% in the detection of amblyogenic refractive errors. CONCLUSIONS: Estimation retinoscopy has very good accuracy for low levels of myopia, hyperopia, and astigmatism. Techniques of estimation may be useful in excluding amblyogenic refractive errors, particularly in children who object to loose lenses held close to them.

Child↗