hello i'm sergeant patel and i'm ophthalmology registrar and in this video tutorial we'll be showing you how to measure and document a distance visual acuity visual acuity or va is an essential part of assessing a patient with an eye complaint it measures the ability of the eye to distinguish details or clearness of an object at a given distance in this video we'll be using the stellen chart as this is the simplest and what is most commonly used in places such as an emergency department and general practice the standard selling chart uses auto type or letters that should be read at a total distance of 6 meters or 20 feet however you may find that your setup is slightly different by using a mirror at three meters or a variation of the standard cylinder chart called a reduced styling chart this is a scaled down version which you read at three meters instead of six meters this is what we're using today on the selling chart a small number represents each line as shown here 60 36 24 and so on when documenting a visual acuity is expressed as a ratio recorded as x over y where x is a testing distance such as 6 meters and y is the line containing the smallest letter that the patient can identify a normal visual acuity is considered to be 6 6. like any procedure ensure that you wash your hands wear appropriate ppe and explain to the patient the procedure and make sure that they're happy to continue there should be good natural lighting or illumination of the chart for distance visual acuity you should assess one eye a time use an occluder or the patient's hand to cover the other eye ask the patient to read down the chart starting from the top you can point to the letters to guide them if appropriate when they start to struggle it's important to encourage the patient to try their best but not to guess the letters in this case the patient is correctly reading the lines six over seven point five as shown here plus two extra letters on the line six over six this can be documented as six over seven point five plus two as two letters are read on the line below you can also write minus if they miss or read letters incorrectly for example six over six minus one then repeat this process with the patient's distance glasses prescription if they have it the next step is to use the pinhole occluder and ask the patients to try and read down further if they're unable to read down to the six over six line the pinhole occluder can correct refractive error and essentially provides the visual acuity with the corrected glasses prescription this can be helpful if the patient has forgotten their distance glasses and will help you determine if a lower than expected visual acuity may be due to refractive rather than a pathological cause then repeat the process for the other eye the patient's visual acuity would be documented as follows for each eye you should document the visual acuity unaided the visual acuity with a distance glasses prescription or contact lenses and finally their visual acuity with a pinhole the patient may have a low visual acuity where they cannot see the 660 line you can ask the patient to move closer to the chart until they can read a letter for example if the patient can read the top letter at half the distance it would be documented as 360. asking the patient to count fingers is an alternative but results are variable good and now how many fingers can you see there two three one if the patient still can't see then you should test the ability to detect hand movements you ask them to tell you which way your hand is moving which way is my hand moving now if less than this then finally you can test for perception of light using a bright light source just tell me which direction it's coming from you can see the light good which direction is it coming from if the patient is unable to see the light then this will be documented as no perception of light this concludes the tutorial on measuring visual acuity visual acuity testing is a simple but important test in any ophthalmology assessment it provides a measure of visual function and if done accurately can help patients to be triaged and managed appropriately many thanks for watching we hope you found this video helpful