OPT505 Clinical Skills: Refraction Techniques

The process of determining the refractive error of the eye using subjective and objective methods.

A series of steps that involve refining the sphere and cylinder to obtain the optimal lens power that provides the clearest possible vision for the patient.

Using a retinoscope to determine the approximate refractive error of the eye by observing the reflex of light from the retina.

Using a trial lens set to refine the refractive error by asking the patient for feedback on sharpness and clarity.

Measuring the visual acuity of the eye using a Snellen chart or other standardized chart.

Assessing the patient's ability to see clearly at all distances, particularly for near vision tasks.

Ensuring clear and concise documentation of the refraction process and results.

Managing patient expectations, providing clear instructions, addressing concerns, and ensuring a comfortable and supportive environment throughout the refraction process.

The refractive error of the eye, where the eye's shape prevents light from focusing correctly on the retina. This can lead to blurry vision.

A condition where the eye is too long or too strong, causing light to focus in front of the retina. This results in nearsightedness, where distant objects appear blurry.

A condition where the eye is too short or too weak, causing light to focus behind the retina. This results in farsightedness, where close objects may appear blurry.

A condition where the cornea or lens has an uneven curvature, causing light to focus at two different points on the retina. This results in blurry vision at all distances.

A measurement method that shines a light into the eye to assess the focusing power of the eye and identify refractive errors.

A check that helps determine the clarity of the eye's internal structures like the cornea, lens and vitreous. It is used to detect opacities that can affect vision.

A procedure that examines the corneal surface to assess its regularity and identify potential abnormalities like keratoconus, a condition where the cornea bulges, which can distort vision.

A check done to assess the size and shape of the pupil. It looks for abnormalities like anisocoria, a condition where the pupils are of different sizes.

Retinoscopy is a procedure used to measure the refractive error of the eye by observing the direction of light reflected from the retina.

During retinoscopy, the patient is asked to focus on a green object to relax their accommodation.

If the light reflex moves in the same direction as the retinoscope, it indicates a 'with' motion. This means the eye needs a plus lens to correct its refractive error.

If the light reflex moves in the opposite direction to the retinoscope, it indicates an 'against' motion.

A cylinder lens has different refractive powers in different meridians (directions).

The power cross diagram illustrates the refractive power of a lens across its different meridians.

The refractive error of an eye refers to how light focuses on the retina. It can be corrected with lenses.

Astigmatism is a refractive error where the eye has different powers in different meridians, causing blurred vision.

The ability of the eye to focus on objects at different distances.

The point where light rays converge after passing through a lens, ideally on or slightly behind the retina.

The smallest circle of blurred light created by a lens, representing the best possible sharpness.

The process of achieving optimal visual clarity and comfort with both eyes simultaneously.

The best vision sphere lens power that provides the sharpest and most comfortable vision subjectively.

A lens with two different refractive powers in perpendicular meridians, resulting in an overall elliptical lens shape. It's represented in the form: +Sphere / +/-Cylinder x Axis (e.g., +6.00 / +2.00 x 90)

Two cylindrical lenses with different powers and axes, where their power vectors intersect at the center. They are typically represented in the form: +Cylinder x Axis / +Cylinder x Axis (e.g., +6.00 x 180 / +8.00 x 90).

The process of converting a sphero-cylindrical lens prescription to an equivalent prescription using a different sphere and cylinder power, with a different axis. This helps understand the lens's power in different meridians.

A visual representation of the lens power in different meridians. Typically a '+' sign with the sphere power in the center and the cylinder power in the appropriate direction based on the axis. It helps visualize the lens's overall power in each direction.

The power of the cylindrical lens in the sphero-cylindrical prescription, represented by the number before the 'x' in the prescription (e.g., +2.00 in +6.00 / +2.00 x 90).

The direction of the cylindrical lens in the sphero-cylindrical prescription, represented by the number after the 'x' in the prescription (e.g., 90 in +6.00 / +2.00 x 90).

The power of the spherical lens in the sphero-cylindrical prescription, represented by the number before the '/' in the prescription (e.g., +6.00 in +6.00 / +2.00 x 90).

The power of the cylinder lens acting at 90 degrees to its axis. It's calculated by adding or subtracting the cylinder power to the sphere power, depending on the sign of the cylinder. It's useful for understanding the lens power in the meridian perpendicular to the cylinder axis.

The point at which light rays converge after passing through a lens or mirror, and it is the focal point of a lens or mirror. It is the ideal point for light to converge on the patient's retina, resulting in clear vision.

A technique used in refraction to find the best vision sphere (BVS) for a patient. It involves presenting a red and green target, and the patient identifies which color appears clearer. Ideally, the patient sees both colors as equal, or the green slightly clearer.

The process of altering the sphero-cylindrical value of a lens during refraction to achieve the best visual acuity for the patient. This includes refining the spherical power to bring the point focus to the retina and adjusting the cylindrical power to correct for astigmatism.

A technique used in refraction to determine the amount of astigmatism in a patient's eye. It involves presenting a series of lenses with varying cylindrical powers to see which provides the clearest vision.

The tendency of a patient's eyes to focus on the most prominent and clear part of a chart, regardless of their actual visual acuity. This can make it difficult to accurately determine the best vision sphere during refraction.

A type of lens that is used to correct astigmatism, which is a condition where the eye's cornea is not perfectly spherical, resulting in blurry vision.

A measure of the degree of astigmatism in a patient's eye. It is expressed in diopters and represents the difference in refractive power between two meridians of the cornea.