A trial frame is a tool used by ophthalmic professionals like

ophthalmologist Ophthalmology ( ) is a surgery, surgical subspecialty within medicine that deals with the diagnosis and treatment of eye disorders. An ophthalmologist is a physician who undergoes subspecialty training in medical and surgical eye care. Followin ...

s and

optometrist Optometry is a specialized health care profession that involves examining the eyes and related structures for defects or abnormalities. Optometrists are health care professionals who typically provide comprehensive primary eye care. In the Uni ...

s. It is basically an adjustable spectacle frame with multiple cells, used to hold

corrective lenses A corrective lens is a lens (i.e. a transmissive optical device) that is typically worn in front of the eye to improve daily vision. The most common use is to treat refractive errors: myopia, hypermetropia, astigmatism, and presbyopia. Glas ...

, and other accessories in

subjective refraction Subjective Refraction is a technique to determine the combination of lenses that will provide the best corrected visual acuity (BCVA). It is a clinical examination used by orthoptists, optometrists and ophthalmologists to determine a patient's ne ...

(finding the correct spectacle power) and

retinoscopy Retinoscopy (Ret) 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. W ...

Uses

To measure a patient's

refractive error Refractive error, also known as refraction error, is a problem with focus (optics), focusing light accurately on the retina due to the shape of the human eye, eye and or cornea. The most common types of refractive error are myopia, near-sightedne ...

squint Squinting is the action of looking at something with partially closed eyes. Squinting is most often practiced by people who suffer from refractive errors of the eye who either do not have or are not using their glasses. Squinting helps momentari ...

and

presbyopia Presbyopia is physiological insufficiency of accommodation associated with the aging of the eye that results in progressively worsening ability to focus clearly on close objects. Also known as age-related farsightedness (or age-related long si ...

, it is used to hold

lens A lens is a transmissive optical device which focuses or disperses a light beam by means of refraction. A simple lens consists of a single piece of transparent material, while a compound lens consists of several simple lenses (''elements''), ...

es,

prism Prism usually refers to: * Prism (optics), a transparent optical component with flat surfaces that refract light * Prism (geometry), a kind of polyhedron Prism may also refer to: Science and mathematics * Prism (geology), a type of sedimentary ...

or other tools like

pinhole occluder A pinhole occluder is an opaque disk with one or more small holes through it, used by ophthalmologists, orthoptists and optometrists to test visual acuity. The occluder is a simple way to focus light, as in a pinhole camera, temporarily removing t ...

. The cells of the trial frame allow holding lenses in correct position. Although

phoropter A phoropter or refractor is an ophthalmic testing device. It is commonly used by eye care professionals during an eye examination, and contains different lenses used for refraction of the eye during sight testing, to measure an individual's ref ...

s, which contains lenses allow a quicker refraction, the trial frame help to test near vision at the patient's preferred working distance and position. Since it is portable, a trial frame is ideal for vision and refraction screening during home (domiciliary) visits and outreach camps. Since it allows more natural vision, trial frame refraction is preferred for patients with

low vision Visual impairment, also known as vision impairment, is a medical definition primarily measured based on an individual's better eye visual acuity; in the absence of treatment such as correctable eyewear, assistive devices, and medical treatment� ...

patients.

Parts

An ideal trial frame have minimum 3 cells, one each for holding spherical lens, cylindrical lens and other tools like occluder or pinhole. Angle for axis of

astigmatism Astigmatism is a type of refractive error due to rotational asymmetry in the eye's refractive power. This results in distorted or blurred vision at any distance. Other symptoms can include eyestrain, headaches, and trouble driving at nig ...

is marked on outermost visible cell There are knobes to adjust pupillary distance, side angle, height and cylindrical lens axis. The nosepiece assembly can be moved front-back and up-down for correct positioning of the lenses in front of the eyes. The length of the legs can also be adjusted. The positions of the two side assemblies give exact measurement of

interpupillary distance Pupillary distance (PD) or interpupillary distance (IPD) is the distance measured in millimeters between the centers of the pupils of the eyes. This measurement is different from person to person and also depends on whether they are looking at near ...

Additional images

File:Ophthalmic trial frame 5.jpg, upside view of a trial frame File:Step 2) Searching for Astigmatism.jpg, a patient wearing trial frame while doing test for astigmatism File:Lens changing technique in eye test.jpg, a patient wearing trial frame while doing refraction File:Maddox rod with trial frames.png, Double

Maddox rod The Maddox rod test can be used to subjectively detect and measure a latent, manifest, horizontal or vertical strabismus for near and distance. The test is based on the principle of diplopic projection. Dissociation of the deviation is brought abo ...

test with trial frames

References

{{Reflist Ophthalmology Optometry Ophthalmic equipment