Retinoscopy
Encyclopedia
Retinoscopy is a technique to obtain an objective measurement of the refractive error
of a patient's eyes. The examiner uses a retinoscope to shine light into the patient's eye and observes the reflection (reflex) off the patient's retina
. While moving the streak or spot of light across the pupil the examiner observes the relative movement of the reflex then uses a phoropter
or manually places lenses over the eye (using a trial frame and trial lenses) to "neutralize" the reflex.
Static retinoscopy is a type of retinoscopy used in determining a patient's refractive error. It relies on Foucault's principle, which states that the examiner should simulate optical infinity
to obtain the correct refractive power. Hence, a power corresponding to the working distance is subtracted from the gross retinoscopy value to give the patient's refractive condition
, the working distance lens being one which has a focal length of the examiner's distance from the patient (e.g. +2.00 dioptre lens for a 50 cm
working distance). Myopes display an "against" reflex, which means that the direction of movement of light observed from the retina is a different direction to that in which the light beam is swept. Hyperopes
, on the other hand, display a "with" movement, which means that the direction of movement of light observed from the retina is the same as that in which the light beam is swept.
Static retinoscopy is performed when the patient has relaxed accommodative status. This can be obtained by the patient viewing a distance target or by the use of cycloplegic drugs (where, for example, a child's lack of reliable fixation of the target can lead to fluctuations in accommodation
and thus the results obtained). Dynamic retinoscopy is performed when the patient has active accommodation from viewing a near target.
Retinoscopy is particularly useful in prescribing corrective lenses for patients who are unable to undergo a subjective refraction that requires a judgement and response from the patient (such as children or those with severe intellectual disabilities or communication problems). In most tests however, it is used as a basis for further refinement by subjective refraction. It is also used to evaluate accommodative ability
of the eye and detect latent hyperopia
.
Refractive error
A refractive error, or refraction error, is an error in the focusing of light by the eye and a frequent reason for reduced visual acuity.-Classification:...
of a patient's eyes. The examiner uses a retinoscope to shine light into the patient's eye and observes the reflection (reflex) off the patient's retina
Retina
The vertebrate retina is a light-sensitive tissue lining the inner surface of the eye. The optics of the eye create an image of the visual world on the retina, which serves much the same function as the film in a camera. Light striking the retina initiates a cascade of chemical and electrical...
. While moving the streak or spot of light across the pupil the examiner observes the relative movement of the reflex then uses a phoropter
Phoropter
A phoropter is an instrument commonly used by eye care professionals during an eye examination, containing different lenses used for refraction of the eye during sight testing, to measure an individual's refractive error and determine his or her eyeglass prescription.Typically, the patient sits...
or manually places lenses over the eye (using a trial frame and trial lenses) to "neutralize" the reflex.
Static retinoscopy is a type of retinoscopy used in determining a patient's refractive error. It relies on Foucault's principle, which states that the examiner should simulate optical infinity
Infinity focus
In optics and photography, infinity focus is the state where a lens or other optical system forms an image of an object an infinite distance away. This corresponds to the point of focus for parallel rays. The image is formed at the focal point of the lens....
to obtain the correct refractive power. Hence, a power corresponding to the working distance is subtracted from the gross retinoscopy value to give the patient's refractive condition
Refractive error
A refractive error, or refraction error, is an error in the focusing of light by the eye and a frequent reason for reduced visual acuity.-Classification:...
, the working distance lens being one which has a focal length of the examiner's distance from the patient (e.g. +2.00 dioptre lens for a 50 cm
Centimetre
A centimetre is a unit of length in the metric system, equal to one hundredth of a metre, which is the SI base unit of length. Centi is the SI prefix for a factor of . Hence a centimetre can be written as or — meaning or respectively...
working distance). Myopes display an "against" reflex, which means that the direction of movement of light observed from the retina is a different direction to that in which the light beam is swept. Hyperopes
Hyperopia
Hyperopia, also known as farsightedness, longsightedness or hypermetropia, is a defect of vision caused by an imperfection in the eye , causing difficulty focusing on near objects, and in extreme cases causing a sufferer to be unable to focus on objects at any distance...
, on the other hand, display a "with" movement, which means that the direction of movement of light observed from the retina is the same as that in which the light beam is swept.
Static retinoscopy is performed when the patient has relaxed accommodative status. This can be obtained by the patient viewing a distance target or by the use of cycloplegic drugs (where, for example, a child's lack of reliable fixation of the target can lead to fluctuations in accommodation
Accommodation (eye)
Accommodation is the process by which the vertebrate eye changes optical power to maintain a clear image on an object as its distance changes....
and thus the results obtained). Dynamic retinoscopy is performed when the patient has active accommodation from viewing a near target.
Retinoscopy is particularly useful in prescribing corrective lenses for patients who are unable to undergo a subjective refraction that requires a judgement and response from the patient (such as children or those with severe intellectual disabilities or communication problems). In most tests however, it is used as a basis for further refinement by subjective refraction. It is also used to evaluate accommodative ability
Accommodation (eye)
Accommodation is the process by which the vertebrate eye changes optical power to maintain a clear image on an object as its distance changes....
of the eye and detect latent hyperopia
Hyperopia
Hyperopia, also known as farsightedness, longsightedness or hypermetropia, is a defect of vision caused by an imperfection in the eye , causing difficulty focusing on near objects, and in extreme cases causing a sufferer to be unable to focus on objects at any distance...
.
See also
- Eye examinationEye examinationAn eye examination is a battery of tests performed by an ophthalmologist, optometrist, or orthoptist assessing vision and ability to focus on and discern objects, as well as other tests and examinations pertaining to the eyes....
- Ophthalmoscope
- Monocular estimate methodMonocular estimate methodThe monocular estimate method or monocular estimation method is a form of dynamic retinoscopy widely used to objectively measure accommodative response. Values normally attained when performing MEM are between +0.25 and +0.50 diopters....
- Red reflexRed reflexThe red reflex refers to the reddish-orange reflection from the eye's retina that is observed when using an ophthalmoscope or retinoscope from approximately 30 cm / 1 foot...
- Eye care professionalEye care professionalAn eye care professional is an individual who provides a service related to the eyes or vision. It is a general term that can refer to any healthcare worker involved in eye care, from one with a small amount of post-secondary training to practitioners with a doctoral level of education.-Current...
- Dispensing optician
- Ophthalmologist
- Optometrist
- Orthoptist