Visual Acuity

1 The Children's Mercy Hospital, 2014. 03/14 Megan Sheeley, CO Visual Acuity The Children's Mercy Hospital, 2014. 03/14 2 What you will learn today History Parameters Optotypes Checking Acuity Pre-verbal Acuity Techniques Pitfalls Pearls The Children's Mercy Hospital, 2014. 03/14 3 Forefathers Herman Snellen Sr (1834-1908) Francisco Cornelius Donders (1818-1889) The Children's Mercy Hospital, 2014. 03/14 4 A little bit of Snellen devises a standardized measurement tool to check vision 1862 1867 Monoyer introduces the decimal notation for Acuity measurements 1888 Landolt proposed the broken ring symbol (Landolt Cs) 1959 Louise Sloan designs a set on non-serif letters for the Acuity chart 1976 Bailey and Lovie design a new Acuity chart with proportional spacing and 5 letters (logMAR) 1982 National Eye Institute combines Sloan and Bailey-Lovie to produce the ETDRS chart The Children's Mercy Hospital, 2014.

2 03/14 5 A little more Donder was the brains behind creating the Visual Acuity measurement While writing his book, Refraction and Accommodation, he realized the need to have a standard for sharpness of vision Donder defined the standard eye to be able to recognize letters that are 5 inches high He used this standard eye to compare his patient s vision, which would give the Visual Acuity The Children's Mercy Hospital, 2014. 03/14 6 The Donder asked his good friend, Herman Snellen to devise a measurement tool for him Snellen first used abstract shapes, but finally decided that letters were best The Children's Mercy Hospital, 2014. 03/14 7 Parameters 20 feet or 6 meters is considered standard when assessing distance vision Requires very little accommodation Reported as a fraction Illumination in room should not be less than 1/5th of the illumination of the chart Most use computer systems M&S System Acuity Pro The Children's Mercy Hospital, 2014.

3 03/14 8 The 20/200 Numerator (20) is the distance the patient is from the object Denominator is the distance a normal eye can see Emmetrope can see the letter at 200 feet Optically handicapped can see at 20 feet The Children's Mercy Hospital, 2014. 03/14 9 20/200 E 200 feet 20 feet 20 200 The Children's Mercy Hospital, 2014. 03/14 10 Optotypes Special characters designed specifically for Visual Acuity measurement Calibrated to the standard eye Optotypes in a basic row on all charts subtend 5 of arc and their detail 1 of arc from the testing distance Standard distance 20 feet or 6 meters The Children's Mercy Hospital, 2014. 03/14 11 Landolt Broken Ring aka Landolt C Ring that has a gap The patient identifies where the gap is located as the size of the C and the gap are reduced Standard optotype for Acuity measurement in most European countries Stroke width is the same as the width of the space, 1/5 of the diameter The Children's Mercy Hospital, 2014.

4 03/14 12 Tumbling E Useful for children Useful for people who may not know the language The Children's Mercy Hospital, 2014. 03/14 13 LogMAR Logarithm of the Minimum Angle of Resolution Letters progress in a geometric progression Fixed 5 letters on each line Space between lines change in proportion keeping contour interaction constant Used mostly in research settings 20/20 or (6/6) = LogMAR 6/60 or 20/200 = LogMar The Children's Mercy Hospital, 2014. 03/14 14 Lea Symbols Designed for children who do not know their alphabet or numbers Developed by Le Hyvarinen, MD, PhD in 1976 while serving her as a fellow at the Wilmer Eye Institute 4 Optotypes: apple, pentagon, square, circle Easily recognizable by preschool age patients The Children's Mercy Hospital, 2014. 03/14 15 Allen Pictures Drawn to Snellen specifications Standardized against adults with known Visual acuities Easily recognized pictures for children who do not know their alphabet Crowding bars can be added to detect amblyopia The Children's Mercy Hospital, 2014.

5 03/14 16 HOTV Designed for children who do not know the full alphabet but can say or match 4 letters Similar to Snellen chart Snellen specifications The Children's Mercy Hospital, 2014. 03/14 17 Sloan Letters Block letters Thickness of the lines equals the thickness of the white spaces Height and width is 5 times the thickness of the line The Children's Mercy Hospital, 2014. 03/14 18 To Crowd or Not to Crowd Contour Interaction Bars Crowding Bars Pediatric Visual Acuity Vision Acuity can be overestimated if measured with single optotypes Amblyopia The Children's Mercy Hospital, 2014. 03/14 19 Monocular Acuity Either eye can be tested first Amblyopic eye Consistent Occlusion Use patch, or tape Hold the occluder yourself The Children's Mercy Hospital, 2014. 03/14 20 Acuity Testing Snellen chart is best Age appropriate test Pictures Matching Letters Shorten testing distance if necessary The Children's Mercy Hospital, 2014.

6 03/14 21 Pre-Verbal Acuity Rely on objective techniques Observation & good history Babies under the age of 3 Developmentally delayed Malingerers Photo by Denis Libouton/iStockphoto/Thinkstock The Children's Mercy Hospital, 2014. 03/14 22 In the Get a good history Do the parents think their child can see? Do they follow faces? Toys? Bottles? Do they notice crossing/drifting? Systemic/Developmental? Any family history of eye problems? The Children's Mercy Hospital, 2014. 03/14 23 Tests Fix & Follow Face Lighted toy Monocular/Binocular Central Steady Maintain Light Reflex Central Nystagmus Maintain with 12BD The Children's Mercy Hospital, 2014. 03/14 24 Eye crossing? Does patient use that eye? Can patient abduct the right eye? Amblyopia? ESOTROPIA The Children's Mercy Hospital, 2014. 03/14 25 Why? What happens when you tilt the head in the opposite direction? Do parents notice head position?

7 Has it always been there? Old photos? Head posture The Children's Mercy Hospital, 2014. 03/14 26 Normal Pupil? Vision OK? Why are they being seen? Wake them up Ptosis Sleeping The Children's Mercy Hospital, 2014. 03/14 27 Tests Preferential Looking Tests Teller Cards Evoked Potential (VEP) Electrodes placed occipital lobe The Children's Mercy Hospital, 2014. 03/14 28 Pitfalls Parents Cooperation Siblings Attention Span ADHD Autistic Children!! The Children's Mercy Hospital, 2014. 03/14 29 Misunderstood Milestones Most children will only be able to identify 1 color by the age of 3 No treatment for color vision problems Letter reversal is normal for a child to do up until 4th-5th grade Work with school, on task training Vision problems will NOT cause debilitating headaches At most dull ache that resolves with break The Children's Mercy Hospital, 2014. 03/14 30 Take Away Pearls Know your tests!

8 Explain why you are doing what you are doing Give the child time to calm down Take breaks The Children's Mercy Hospital, 2014. 03/14 31 Take Away Pearls Take control of the room Gently lay down rules Hands on lap Sit up nice and tall Use your listening skills Talk directly to child Get down to child s level The Children's Mercy Hospital, 2014. 03/14 32 AAPOS Techniques for Pediatric Vision Screening ( ). In AAPOS retrieved February 2, 2015 from Biography Donders. ( ). Donders Institute. Retrieved on 12/15/2015 from Herman Snellen (1834-1908). ( ). The Foundation of the American Academy of Ophthalmology. Retrieved 02/12/2015 from The historical Evolution of Visual Acuity Management. Colenbader, August 2001. Retrieved from Visual Acuity . ( ). In Wikipoedia. Retrieved February 12, 2015 from World Health Organization. Consultation on development of standards for characterization of vision loss and Visual functioning.

9 2003. Retrieved from Works Cited