JOHN HAY BIOMEDICAL  /  PHYSICAL EXAM SKILLS
PART 1 | BACKGROUND AND DEFINITIONS
Measure clearly, report carefully
A narrative guide to distance visual acuity, screening records, and the rest of an eye exam.
Imagine a clinic team setting up a vision station. A fictional adult, Case FOCUS, says, "I can read the big
letters. The smaller ones are harder." Your first job is to make the measurement fair. Your second is to
describe what it shows without guessing why.
Cornea
Iris
Pupil opening
Lens
Retina
Optic nerve
ANTERIOR / FRONT
POSTERIOR / BACK
LIGHT
Original anatomical schematic, not to scale
Figure E1. Follow the signal. Light crosses the cornea, passes through the pupil, and crosses the lens. The cornea and lens focus
it onto the retina. Retinal cells change light into electrical signals. Those signals travel through the optic nerve toward the brain. The
iris controls the pupil opening. [S1]
Your driving question
How do we turn a person's responses into a useful vision record? A screening flags a concern. An
eye care professional uses a fuller exam to investigate it.
Route through this guide. Learn the fraction on page 2. Set up and perform the procedure on pages 3 and 4. Record on page 5.
Follow the worked case on pages 6 and 7. Explore other exam skills on page 8. Practice with fictional data on page 9.
Educational model | Fictional records | Sources S1, S3 on page 11
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JOHN HAY BIOMEDICAL  /  PHYSICAL EXAM SKILLS
PART 1 | BACKGROUND AND DEFINITIONS
What does 20/40 mean?
Visual acuity is how well a person resolves small detail under stated test conditions.
Acuity is one part of vision. A chart asks a person to identify optotypes, standardized letters or symbols.
Large optotypes are easier to resolve. Small ones demand finer detail. The smallest line that meets that
chart's scoring rule becomes the recorded result. [S2, S3]
20/20
At 20 feet, identifies detail the reference observer identifies at 20 feet.
20/40
At 20 feet, identifies detail the reference observer identifies at 40 feet.
20/80
At 20 feet, identifies detail the reference observer identifies at 80 feet.
Figure E2. Read the two numbers. The top number names the test distance in feet for these examples. The bottom number
describes the reference distance for that size of detail. The 20/40 row uses larger detail than the 20/20 row. These boxes are
explanations, not test targets. [S2]
Keep the meaning, skip the percentage
20/40 does not mean "40 percent vision" or "half of all vision." The fraction describes detail resolution. It
does not measure all visual fields, color vision, or eye health. 20/20 is a useful reference for acuity, not
proof of perfect eyes.
Metric notation uses meters: 6/6 corresponds to 20/20, and 6/12 to 20/40. A chart designed for 10 feet can
still display equivalent 20-foot labels. Use its own instructions. Do not move or resize a chart and keep its
old labels. [S2]
What to notice
For the same numerator, a larger denominator describes poorer measured detail resolution. 20/20 is
finer than 20/40. Some people resolve finer detail than 20/20, such as 20/15.
Educational model | Fictional records | Sources S2, S3, S4 on page 11
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JOHN HAY BIOMEDICAL  /  PHYSICAL EXAM SKILLS
PART 2 | DIRECTIONS
Build a fair vision station
The distance, lighting, correction, and covered eye are part of the measurement.
The team prepares the station before calling Case FOCUS. They use a real, approved chart and its
manual. This guide and its screen graphics cannot replace a calibrated chart. In class, use fictional records
unless your teacher and nurse approve the actual screening procedure.
E
T F
P O T
Z L P E
SCHEMATIC ONLY
Chart at eye level
Eye position
Measure chart-to-eye distance
Use the chart manual. Not every chart uses 20 feet.
Figure E3. Set the geometry. The person's eyes, not their toes, define the viewing distance. Give the chart even light without glare.
A floor mark helps the person keep position. The diagram is not to scale. [S2, S8]
Prepare
Check before starting
Equipment
Approved distance chart + its manual; tape measure; approved clean occluder;
record sheet; usual distance glasses if prescribed.
Environment
Chart at suitable eye level; even light; no glare, crowding, or coaching. Keep the
chart and person in the specified positions.
Correction
Use the usual prescribed distance correction as the screening protocol directs.
Record glasses, contact lenses, or no correction. Do not borrow another person's
glasses.
Permission and
comfort
Explain the task. Allow questions or stopping. For actual concerns, involve the
teacher or nurse. Keep any actual record private.
Educational model | Fictional records | Sources S2, S3, S8 on page 11
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JOHN HAY BIOMEDICAL  /  PHYSICAL EXAM SKILLS
PART 2 | DIRECTIONS
Measure one eye at a time
Use this sequence with the actual chart manual and a trained supervising adult.
1. Explain and check
Say, "Read the letters I indicate. Tell me if you cannot make them out." Confirm the chart's distance,
lighting, correction, and scoring instructions. Use a chart that matches the person's communication needs.
2. Position and start
Place the person at the marked eye-to-chart distance. Keep the head upright. Begin with the large line
specified by the chart protocol. Explain any matching or pointing response before scoring.
3. Test the right eye
Cover the left eye with an approved occluder. Keep both eyes comfortably open behind it. Do not press on
the eye. Watch for peeking around the edge, a head turn, or leaning toward the chart.
4. Move through the lines
Indicate letters without covering their neighbors. Follow the chart manual for the order, number of letters,
and when to stop. Record correct and missed letters. Do not coach the identity of a letter.
5. Score and record
Use the actual chart's pass rule. Record the smallest line meeting that rule, missed letters, right eye, test
distance, correction, and any problems. If the conditions failed, record the problem instead of a confident
result.
6. Switch eyes
Cover the right eye. Test and record the left eye with the same conditions. Use the manual's alternate chart
or sequence if provided. Two eyes together can hide a difference between eyes.
7. Clean and review
Clean reusable equipment as its maker and school infection-control policy require. A nurse or trained
professional reviews genuine concerns and follows current rescreen/referral procedures. Classroom
practice does not diagnose.
The rule belongs to the chart
Different charts have different letter counts and scoring rules. There is no universal "miss two and
stop" rule. The simulation uses a pre-scored fictional record, not a clinical scoring algorithm.
Educational model | Fictional records | Sources S2, S3, S8 on page 11
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JOHN HAY BIOMEDICAL  /  PHYSICAL EXAM SKILLS
PART 2 | DIRECTIONS
Create a record others can use
A number needs its conditions. Write down how the number was obtained.
The recorder sees Case FOCUS reach a smaller line and hesitate. "Do I just write 20/40?" they ask. The
screener says, "Add which eye, the distance, the correction, and what happened. The next person needs
the same context."
Field
What to write
Eye tested
Right eye or left eye. A binocular result means both eyes together; it cannot
replace two separate-eye results.
Chart and distance
Actual chart type/model and specified viewing distance. Record any nonstandard
condition, and do not apply standard labels blindly.
Correction
Usual distance glasses, contact lenses, or none, according to the protocol. "With
usual glasses" is not the same as best possible correction.
Responses
Smallest line meeting the actual chart rule; number or identity of missed letters;
smaller line attempted; any unreliable response.
Conditions
Lighting, glare, occlusion, leaning, understanding, or any interruption that
affected the result.
Next step
Teacher/nurse or qualified eye care follow-up per current protocol. Report
concerns with neutral language.
Build your practice record
For the fictional case on page 9, write two rows in your notes, one for each eye. Add chart and distance,
correction, smallest line, response note, and conditions. Then write one sentence about the limit of the
result.
Use words before abbreviations
Right eye may appear as OD; left as OS; both eyes as OU. Write the full words in class so laterality
stays clear. Never swap the observer's right with the person's right.
Educational model | Fictional records | Sources S2, S3 on page 11
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JOHN HAY BIOMEDICAL  /  PHYSICAL EXAM SKILLS
PART 3 | WORKED EXAMPLE
Follow Case FOCUS
A wholly fictional adult demonstration. These are model values, not your own measurements.
Case FOCUS wears their usual distance glasses. The fictional screener uses a 20-foot distance chart at 20
feet. Lighting is even, glare is absent, and each eye is covered in turn. The person understands the letters.
The same protocol is used for both eyes.
Line label
Right eye responses
Left eye responses
20/80
5 of 5 correct
5 of 5 correct
20/50
5 of 5 correct
5 of 5 correct
20/40
5 of 5 correct
5 of 5 correct
20/32
1 of 5 correct
5 of 5 correct
20/25
Not tested
5 of 5 correct
20/20
Not tested
5 of 5 correct
Record E4. Simulated responses. The fictional chart protocol has already been applied to this record. Right eye is recorded as
20/40. Left eye is 20/20, the smallest line supplied and tested. Finer left-eye lines were not tested. These extremes avoid a
borderline partial-line scoring example.
Why the team stops guessing
The right eye reads every letter on 20/40, then only one on 20/32. The left reaches 20/20. The team
records two results. They do not combine them into an average. They do not call the right eye "lazy," name
a disease, or choose a glasses prescription.
Worked report
"In this fictional 20-foot test with usual distance glasses, right-eye acuity was 20/40 and left-eye acuity
was 20/20. The right eye resolved less detail under these conditions. The cause remains unknown. A
qualified eye care professional should evaluate the concern."
Do not copy the model's numbers into your own case. The simulation lets you reveal this same record step by step. Use your
optional practice record on page 9 to rehearse the reasoning with different values.
Educational model | Fictional records | Sources S2, S3; E4 fictional on page 11
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JOHN HAY BIOMEDICAL  /  PHYSICAL EXAM SKILLS
PART 3 | WORKED EXAMPLE
Analyze the result carefully
Observation, possible mechanism, next step. Keep those three ideas separate.
1. State the observation
From Record E4, the right eye resolves less detail than the left under the stated conditions. 20/40 is
reduced relative to the 20/20 reference. A two-eye result could have hidden this difference. The separate
records make it visible.
2. Check measurement quality first
Ask whether the chart was at its specified distance. Was glare present? Could the covered eye peek?
Were the intended glasses worn? Did the person know the symbols? If the answer is uncertain, describe
the uncertainty and ask for trained review.
3. Connect a possible mechanism
A refractive error occurs when the eye's optical system fails to focus light clearly on the retina. It can reduce
acuity. In myopia, light from distant objects focuses in front of the retina. That is one possible mechanism
for distance blur, not a diagnosis of Case FOCUS. [S5, S6]
Focused on retina
Retina
Focus before retina
Retina
Figure E5. Compare focal position. Left: rays meet at the retinal plane. Right: rays meet before it and spread by the time they reach
the retina. These simplified light-path models illustrate focus only. They are not ray-traced clinical models. [S5, S6]
4. Name the limit and next step
Acuity alone cannot tell whether blur comes from refraction, the retina, the nerve pathway, or another
problem. It does not determine a lens prescription. If an actual person reports pain, sudden change, or an
injury, stop the classroom activity and tell the teacher or nurse promptly.
Educational model | Fictional records | Sources S2, S5, S6, S8 on page 11
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JOHN HAY BIOMEDICAL  /  PHYSICAL EXAM SKILLS
PART 1 EXTENSION | BEYOND THE CHART
An eye exam asks more
A clinician chooses tests for the question. One chart cannot answer them all.
Case FOCUS asks, "If I read 20/20, does that mean everything is healthy?" The team explains that a chart
tests detail. A comprehensive eye exam checks more functions and structures. Some eye diseases have
few early symptoms. [S4]
Exam component
What it explores
Classroom boundary
Distance and near
acuity
Detail at stated far or near distances. Near
tests use their own target, distance and
instructions.
Use approved charts only under
supervision, or supplied fictional
records.
Visual fields
The area seen while looking straight
ahead, including side vision.
A rough class model cannot rule out
a field defect. Keep the gaze fixed if
a teacher models the idea.
Pupil response
How pupil size changes with light,
including the response in each eye.
Use the diagram below. No lasers,
phone flash, strong lights or
prolonged light exposure in class.
Eye movements
How the eyes move together and track a
target.
A teacher may model following a
comfortable target. Stop with
discomfort or double vision.
Color vision
Ability to distinguish specified color
patterns under standardized conditions.
A screen's colors and printed copies
vary. This package is not a color
vision test.
Pressure and
internal exam
Tonometry measures eye pressure. A
clinician may dilate pupils with drops to
inspect internal structures.
No eye-contact instruments,
pressure tests or dilation drops in
class.
Dimmer setting
Brighter setting
Pupil opening
Figure E6. Pupil size model. The dark opening is larger in the dimmer model and smaller in the brighter model. The iris surrounds
it. This drawing shows a general response, not a clinical pupil exam. [S1, S4]
Educational model | Fictional records | Sources S1, S4, S7 on page 11
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JOHN HAY BIOMEDICAL  /  PHYSICAL EXAM SKILLS
PART 4 | YOUR WORK
Practice with fictional evidence
Use the offline simulation first. Then explain a fresh record in your own words.
Open Eye-Exam-Simulation.html
The page works without an internet connection. It never tests your eyes. Do not stand back or try to read its
drawings as a chart. All letter responses are fixed teaching data from Case FOCUS.
1. In "Decode the fraction," choose 20/20, 20/40, or 20/80. Read the full distance statement.
2. In "Prepare the fictional station," check the four setup steps. Say why each matters.
3. Reveal one chart line at a time for the right eye. Record the supplied responses. Switch to the left eye
and repeat.
4. Compare the completed record to E4 on page 6. Read the limit before writing a conclusion.
5. Reset the page to practice again. No information is saved or sent.
If you cannot open the simulation
Use Record E4 on page 6. Cover the lower rows with paper. Reveal one row at a time, record each
eye separately, and use the worked report to check your reasoning. Every required input is already in
this guide.
Your optional case: Record E7
A different fictional adult is tested using a 20-foot chart at its specified 20 feet. Usual distance glasses are
worn. Each eye is tested separately. Lighting, occlusion, and understanding are satisfactory. The chart
protocol is already applied.
Eye
Recorded acuity
Response note
Right
20/25
All letters on that line; next smaller line did not meet the actual protocol.
Left
20/50
All letters on that line; next smaller line did not meet the actual protocol.
Use it now. Write a three-sentence report using E7. First, state both results and their conditions. Second,
compare the measured detail resolution. Third, name one limit and the appropriate professional next step.
Do not diagnose a cause.
Reflect. Which setup error could make a line look easier? Explain the direction of the error. Then explain why 20/20 cannot certify
all eye health. Use pages 2, 3 and 8. This is optional practice; no new submission is required.
Educational model | Fictional records | Sources S2, S3; E7 fictional on page 11
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JOHN HAY BIOMEDICAL  /  PHYSICAL EXAM SKILLS
PART 4 | KEEP THE LEARNING
Words you can use precisely
Record, Reduce, Review, Reflect, Recite, Revise.
Term
Plain-language meaning
Acuity
Ability to resolve small visual detail under stated conditions.
Optotype
A standardized letter or symbol used in an acuity chart.
Cornea
Clear curved front surface that helps bend incoming light.
Pupil / iris
Pupil: opening for light. Iris: surrounding tissue that controls its size.
Lens
Clear structure behind the pupil that helps focus light.
Retina / optic nerve
Retina: light-sensitive tissue. Optic nerve: carries visual signals toward the
brain.
Refraction
Bending of light as it passes between materials.
Refractive error
Optical focusing problem that can cause blur.
Myopia
Nearsightedness; distant-object light focuses in front of the retina.
Correction
Prescribed glasses or contact lenses used during the test.
Occlusion
Blocking the eye that is not being tested, without pressing on it.
Monocular / binocular
One eye / both eyes. Record exactly which condition was used.
Visual field
Area a person can see while gaze stays fixed.
Screening / referral
A brief check for concerns / directing a concern to qualified eye care.
Dilation / tonometry
Clinician widening of the pupil / clinician measurement of eye pressure.
Recite, then revise
Close the guide. Explain the 20/40 fraction aloud. Name four conditions that belong in a record.
Reopen pages 2 to 5 and correct one missing detail in your explanation.
Educational model | Fictional records | Sources S1-S8 on page 11
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JOHN HAY BIOMEDICAL  /  PHYSICAL EXAM SKILLS
EVIDENCE AND NEXT STEPS
Sources and claim ceilings
Facts checked October 16, 2026. These links are optional; the guide supplies every practice input.
S1. National Eye Institute (NEI), How the Eyes Work. Updated April 20, 2022. Source
S2. American Academy of Ophthalmology (AAO), EyeWiki: Visual Acuity Testing in Adults. Acuity notation and documentation.
Source
S3. American Association for Pediatric Ophthalmology and Strabismus (AAPOS), Vision Screening. Updated April 2024. Source
S4. NEI, Get a Dilated Eye Exam. Updated November 26, 2025. Source
S5. NEI, Refractive Errors. Updated December 19, 2025. Source
S6. NEI, Nearsightedness (Myopia). Updated December 4, 2024. Source
S7. NEI, Color Blindness. Updated November 5, 2025. Source
S8. Ohio Department of Health, Vision Screening Requirements and Guidelines, 2017. Historical procedural support, mirrored by
Prevent Blindness Ohio. Source
S9. AAPOS, Vision Screening Recommendations. Age-specific professional guidance. Source
The evidence supports a careful screening record
Acuity results compare resolved detail under stated conditions. They do not identify a disease, set a
lens prescription, certify fitness for an activity, or rule out all eye problems. Fictional responses are
teaching examples, not clinical evidence.
Actual school screening. Use a nurse or trained screener, the actual approved chart manual, and current district and Ohio
procedures. The 2017 manual is not presented as current policy. If symptoms or concerns occur, involve the teacher/nurse and
qualified eye care. Do not keep repeating a classroom test to dismiss a concern.
Illustration provenance. E1, E2, E3, E5 and E6 are original vector teaching illustrations built for this guide from the cited anatomy
and measurement facts. They are schematic and not to scale. E4 and E7 are wholly fictional records. No patient photographs,
student records, or diagnostic chart images are used.
Educational model | Fictional records | Sources S1-S9 on page 11
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