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PubMed1998

Retinoscopy.

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Diagnostic Techniques, Ophthalmological↗
PubMed1996

Retinoscopic reflexes: theoretical basis and effects of monochromatic aberrations.

BACKGROUND: Current literature describing retinoscopy does not provide a full description of the pupil reflexes observed in retinoscopy or of the effects of monochromatic aberrations. The intent of the study was to develop a geometrical model of retinoscopy that provides a more complete analysis. The model can take specific aberrations and predict the succession of reflexes observed in retinoscopy for an eye with these aberrations. METHODS: Theoretical predictions were compared with observations using a hand-held streak retinoscope. CCD-based retinoscopy was performed on subjects with known aberrations. RESULTS: Reflexes observed in retinoscopy can be computed by modeling a light source whose eccentricity from the retinoscope sight-hole is varying in position. Results from study calculations show that the succession of reflexes observed in retinoscopy can be thought of as a measure of the transverse aberration of the eye. Both qualitative and quantitative measures showed agreement between theoretical and experimental results. Transverse aberration of the eye can be observed and measured using retinoscopy. CONCLUSIONS: Monochromatic aberrations have significant and predictable effects on retinoscopy. The best way for a retinoscopist to avoid such aberrations and provide a proper refraction is to neutralize the reflex across the largest visual zone possible and ignore the reflex motion at the edges of the pupil.

Humans↗
PubMed2004

[The combination of positive cylinders with negative cylinders in the detection of mixed astigmatism].

OBJECTIVE: To study clinical retinoscopy combined positive cylinders with negative cylinders in the detection of mixed astigmatisms. METHOD: 189 cases (340 eyes) with mixed astigmatism were divided into three groups (< 3.00 D; 3.00 approximately 6.00 D; > 6.00 D). There are 156 eyes with mixed astigmatism less than 3.00 D (76 eyes in experiment group, 80 eyes in control group); 132 eyes with mixed astigmatism between 3.00 D to 6.00 D (68 eyes in experiment group, 64 eyes in control group) and 53 eyes with mixed astigmatism over 6.00 D (29 eyes in experiment group, 24 eyes in control group). They were examined with cycloplegic retinoscopy. Retinoscopy of combined positive cylinders with negative cylinders was applied in experiment group, while conventional retinoscopy was used in control group. According to the shape of neutralized image, the accuracy and facility of the axis judgement, operating time and the number of combined lens, the result of retinoscopy was classified into three grades. Grade I: The shape of neutralized image is well distributed. The axis is easy to be evaluated precisely. Operating time is less than five minutes and only need one or two piece of lens. Grade II: The shape of neutralized image is not so well distributed. The axis is not difficult to be evaluated. Operating time is from five to ten minutes and needs two or three piece of lens to combine with. Grade III: The shape of neutralized image is not so well distributed and would be interfered by the combined lens or other factors easily. The axis is difficult to be evaluated precisely. Operating time is more than ten minutes and needs more than three piece of lens to combine with. RESULT: In the group of mixed astigmatism less than 3.00 D, no significant difference was found between experiment group and control group. (chi(2) = 0.094, P = 0.759). However, significant difference (chi(2) = 5.546, P = 0.019) was found between the groups with mixed astigmatisms from 3.00 D to 6.00 D and very significant difference (chi(2) = 8.509, P = 0.004) was found between the groups with mixed astigmatisms over 6.00 D. CONCLUSION: Retinoscopy of combined positive cylinders with negative cylinders is an effective, convenient and precise method for detection higher degree mixed astigmatisms. It's an additional assistance for the conventional retinoscopy.

Adolescent↗
PubMed1990

[Objective determination of refraction].

Objective determination of refraction is basically necessary for the subjective adjustment of refraction aimed at prescribing glasses. At least as important is the use of objective determination of refraction as a basis of ophthalmological diagnosis because the best-corrected visual acuity forms basic diagnostic information. Three methods of objective determination of refraction are available. Photorefraction has only been used for screening preschool children, as it has no value for the above-mentioned purpose. Refractometry is widely being used for objective determination of refraction, and during the last few years automated refractometry has also become more and more common. This trend is supported by the possibility of delegating automated refractometry to assistant medical personnel. Retinoscopy and automated refractometry yield comparable results. Retinoscopy has some advantages: great flexibility and the fact that retinoscopy forms an image of optical aberrations of the eye, giving the ophthalmologist an idea of the optical quality of the patient's eye. Due to its flexibility retinoscopy can be used for refractioning babies and infants without any problem. The disadvantage of retinoscopy is the impossibility of delegating it to assistant medical personnel and the fact that this method must be learned by the ophthalmologist. In contrast to retinoscopy, automated refractometry can easily be learned and can be delegated to assistant medical personnel. Its drawback is that it is inflexible, making it inconvenient for refractioning babies and infants. If automated refractometry and retinoscopy are used with cycloplegia, precautions are essential to avoid errors caused by optical aberrations of the eye. The measurement must be done in the center of the pupil.(ABSTRACT TRUNCATED AT 250 WORDS)

Eyeglasses↗