Ophthalmic trial frame

{{Short description|Tool used in eye examination}} {{Infobox diagnostic | name = Ophthalmic trial frame | image = File:Ophthalmic trial frame 3.jpg | alt = | caption = Ophthalmic trial frame | pronounce = | purpose = ophthalmic trial frame is used to hold lenses and other accessories during correction of refractive errors. | test of = Visual acuity | based on = | synonyms = | reference_range = | calculator = | DiseasesDB =  | ICD10 =  | ICD9 = | ICDO = | MedlinePlus =  | eMedicine =  | MeshID = | OPS301 =  | LOINC =  }} A '''trial frame''' is a tool used by ophthalmic professionals like ophthalmologists and optometrists. It is basically an adjustable spectacle frame with multiple cells, used to hold corrective lenses, and other accessories in subjective refraction (finding the correct spectacle power) and retinoscopy.

==Uses== To measure a patient's refractive error, squint and presbyopia, it is used to hold lenses, prism or other tools like pinhole occluder.<ref name="Elliot">{{Cite book |title=Clinical procedures in primary eye care |date=2014 |others=David B. Elliott |isbn=978-0-7020-5194-4 |edition=Fourth |location=Philadelphia |pages=73–75 |language=English |chapter=Refraction and prescribing |oclc=863192233}}</ref> The cells of the trial frame allow holding lenses in correct position.<ref name="Elliot"/>

Although phoropters, which contains lenses allow a quicker refraction, the trial frame help to test near vision at the patient's preferred working distance and position.<ref name="Elliot"/> 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 patients.<ref>{{Cite journal |last1=DeCarlo |first1=Dawn K. |last2=McGwin |first2=Gerald |last3=Searcey |first3=Karen |last4=Gao |first4=Liyan |last5=Snow |first5=Marsha |last6=Waterbor |first6=John |last7=Owsley |first7=Cynthia |date=January 2013 |title=Trial Frame Refraction versus Autorefraction among New Patients in a Low-Vision Clinic |journal=Investigative Ophthalmology & Visual Science |volume=54 |issue=1 |pages=19–24 |doi=10.1167/iovs.12-10508 |issn=0146-0404 |pmc=3541945 |pmid=23188726}}</ref><ref>{{Cite web |title=An accurate trial frame refraction is the key to managing low vision patients |url=https://www.healio.com/news/optometry/20120225/an-accurate-trial-frame-refraction-is-the-key-to-managing-low-vision-patients |access-date=2022-04-17 |website=www.healio.com |language=en}}</ref>

==Parts== An ideal trial frame have minimum 3 cells, one each for holding spherical lens, cylindrical lens and other tools like occluder or pinhole.<ref name="Khurana">{{Cite book |title=Theory and practice of optics and refraction |publisher=Elsevier |date=2018 |author=A. K. Khurana |edition=Fourth |location= |page=131 |language=English |chapter= clinical refraction: determination of the errors of refraction}}</ref> Angle for axis of astigmatism is marked on outermost visible cell there are knobs to adjust pupillary distance, side angle, height and cylindrical lens axis.<ref name="CEHJ">{{Cite web |title=Community Eye Health Journal » Understanding and looking after a retinoscope and trial lens set |url=https://www.cehjournal.org/article/understanding-and-looking-after-a-retinoscope-and-trial-lens-set/ |access-date=2022-04-17 |website=www.cehjournal.org}}</ref> The nosepiece assembly can be moved front-back and up-down for correct positioning of the lenses in front of the eyes.<ref name="CEHJ"/> The length of the legs can also be adjusted.<ref name="CEHJ"/> The positions of the two side assemblies give exact measurement of interpupillary distance.<ref name="CEHJ"/>

== Modern Techniques == The majority of trial frames are manufactured using combinations of metal and plastic parts using injection moulding techniques. Newer trial frame like the [https://www.oico.co.uk/professional-trial-frame OICO TF-4]use additive SLS 3D printing to reduce the number of parts. {{cn|date=December 2025}}

==Additional images== <gallery> 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 test with trial frames </gallery>

==References== {{Reflist}}

Category:Ophthalmology Category:Optometry Category:Ophthalmic equipment