OPT505 Clinical Skills: Refraction Techniques

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Questions and Answers

What should you avoid when recording the axis for cylindrical measurements?

Using inconsistent units

Using 0 for horizontal cyl axis (correct)

Using ° for cyl axis (correct)

Recording in whole numbers

How should one confirm a patient's visual acuity after refining the sphere?

By comparing their results to standard charts

By inquiring if they can still see the letters (correct)

By measuring the acuity with a different scale

By asking them to read multiple lines

What factor should be considered to prevent patient fatigue during refraction?

Limiting repetition and providing reassurance (correct)

Changing testing locations frequently

Using as many lines as possible each time

Increasing the light intensity during examination

Which approach should be combined with subjective refraction techniques?

Objective refraction techniques Signup and view all the answers

What is an appropriate step size for recording sph and cyl measurements?

Record in 0.25 steps Signup and view all the answers

What is the preferred method when determining the smallest readable line during visual acuity assessment?

Limit to one or two lines, depending on their vision Signup and view all the answers

During which part of the refraction process should you establish an initial visual acuity measurement?

Before beginning subjective testing Signup and view all the answers

What is a key recommendation regarding how results should be documented during a refraction?

Results should be written down continuously as they occur Signup and view all the answers

What does retinoscopy help determine about the patient's prescription?

If the prescription is overminused Signup and view all the answers

What is the primary purpose of asking a patient to look at the green light during retinoscopy?

To relax the patient's accommodation Signup and view all the answers

What specific skill can be developed through practice in retinoscopy?

Manual retinoscopy technique Signup and view all the answers

What kind of lens is represented by a power cross diagram showing +6.00D all around?

A spherical lens Signup and view all the answers

If a lens has a +8.00D with a difference of 2D between the principal meridians, what type of lens is it?

Plus cylinder lens Signup and view all the answers

Which strategy is suggested for improving retinoscopy technique?

Eliminate the use of working lenses Signup and view all the answers

The retinoscopy technique involves leaning in or back; what does leaning in indicate?

Against the meridian Signup and view all the answers

What type of patients could benefit from manual retinoscopy techniques?

Patients who cannot access autorefractors Signup and view all the answers

What is the primary purpose of using +0.25DS during refraction?

To assess if letters appear better or worse Signup and view all the answers

What should a practitioner do if the patient perceives letters as smaller and darker after offering -0.25DS?

Stop offering minus and revert to +0.25DS Signup and view all the answers

What characterizes a myopic eye in terms of light refraction?

It is elongated, causing excessive refraction. Signup and view all the answers

In the context of the Duochrome test, what indicates the best vision sphere?

Patient sees green as clearer or both as equal Signup and view all the answers

Which visual acuity measurement corresponds to a Snellen fraction of 6/12?

Decimal 0.67 Signup and view all the answers

What is the effect of hyperopic astigmatism on the eye's focusing ability?

It results in insufficient light refraction. Signup and view all the answers

What adjustment should be made to the sphere when changing the cylinder during refraction?

Add 0.25D for every 0.50D change in cylinder Signup and view all the answers

What is the desired outcome of a refraction process according to the instructions provided?

Achieve a point focus on the retina or just behind it Signup and view all the answers

What is the primary purpose of retinoscopy in an eye examination?

To check for media opacities and corneal regularity. Signup and view all the answers

What should an optometrist do if a patient's cylinder changes dramatically from retinoscopy?

Re-check the best vision sphere and verify the changes Signup and view all the answers

What type of lens is used to correct myopic errors?

Minus lenses to diverge light rays. Signup and view all the answers

What approach should a practitioner take regarding patient comfort during refraction?

Reassure patients that uncertainty is acceptable Signup and view all the answers

Which type of astigmatism involves focal lines that differ in curvature?

Mixed astigmatism. Signup and view all the answers

During virtual refraction, which statement is true regarding the examples provided?

Only pre-presbyopic patients were tested Signup and view all the answers

What does a visual acuity of 6/24 indicate about a person's vision?

The person sees at 6 meters what a normal person sees at 24 meters. Signup and view all the answers

What does the circle of least confusion in astigmatism typically refer to?

The intersection point of two focal lines. Signup and view all the answers

What is the total power of the crossed cylinders (+6.00 x 180 and +8.00 x 90)?

+10.00D Signup and view all the answers

When laying down the most plus sphere first, what should be the resulting lens configuration for the crossed cylinders?

+8.00/-2.00 x 180 Signup and view all the answers

Which configuration represents the addition of a plus cylinder at 90 degrees?

+6.00/+2.00 x 90 Signup and view all the answers

What adjustment is made to reach a total power of +8D from a starting power of +6D?

+2.00D added Signup and view all the answers

What is the correct description of the action of a -2.00DC in this context?

Acts at 90 degrees to the principal meridian Signup and view all the answers

Which of the following correctly indicates the addition of the least plus sphere first?

+6.00DS/-2.00DC@180 Signup and view all the answers

What is the primary property of a sphero-cylindrical lens in terms of orientation?

The cylinder axis is plano and power is perpendicular Signup and view all the answers

What is the resultant effect when combining +8D with -2D in the context of these lenses?

A total of +6D Signup and view all the answers

What is the primary goal of performing retinoscopy?

To achieve a point focus on the retina or slightly behind Signup and view all the answers

During the subjective examination, which term refers to the optimal lens combination that provides sharp and comfortable vision?

Best Vision Sphere (BVS) Signup and view all the answers

What does 'Binocular Balance' refer to in the context of refraction?

The inclusion of both eyes in the refraction process Signup and view all the answers

What is the purpose of using a '+1 blur' during the retinoscopy procedure?

To relax the accommodation of the eye Signup and view all the answers

In the context of subjective refraction, what defines the 'circle of least confusion'?

The area of overlap between focused and unfocused light Signup and view all the answers

Which step should be performed first when balancing binocular refraction?

Record monocular distance visual acuity Signup and view all the answers

Why is it important to control accommodation during the subjective refraction process?

To ensure the eye is relaxed for accurate measurements Signup and view all the answers

What is indicated by performing 'Un-occlude, BEO' in the retinoscopy procedure?

Evaluating balance between both eyes Signup and view all the answers

Study Notes

Lecture Recording Information

Lectures are recorded as part of Plymouth University's Content Capture project
Recordings are available via the Panopto block on student module DLE pages
Students can ask questions during the lecture
Comments made during the lecture may appear on the recording
Students can ask the lecturer to pause the recording if they do not want their question to be recorded

Clinical Skills and Refractive Management: Refraction

Course code OPT505
Lecturer: Ellie Livings
Faculty: Health - Medicine, Dentistry & Human Sciences

Learning Objectives

Review of refraction techniques
Understanding the optics behind refraction
Applying techniques to personal routines
Progression through skills (3rd year & beyond)
Advanced refraction techniques based on patient needs
Detailed understanding of different component parts (e.g., x-cyl, BVS)

Working Cleanly

Clear recording of procedures is important to avoid errors
Accuracy in recording data is essential
Writing down results as you go, not only at the end, is crucial
Record in 0.25 steps for sphere and cylinder
Avoid confusing cylinder axis with zero
Correct use of units

Visual Acuity

Do not present the patient with too many lines to read at a time
Limit the number of times to check the patient's visual acuity
Assess initial vision to inform refraction process
Check if the patient can still see the letters after adjustments
Assess the patient's ability to see after +1.00 blur

Visual Acuity Chart Example

The exact values and letters on the chart vary, but the principle remains the same— to identify acuity levels

When to Stop Measuring VA

Initial measurement is important as a starting point for the refraction process
Adjust according to how much the patient needs the refraction adjustment to be precise
Continue with testing to see if the target lines are still visible for the patient
Final VA value should reflect to push the patient's capabilities

Ametropia effects: What does the VA/Vis tell us?

Data relating Snellen fractions to decimal and LogMAR values
Data relating Sph Blur and Cyl Blur to different Snellen fractions

Simulation of Refractive Errors

Demonstrates various refractive error types' impact on visual acuity and the identification of letters, fans, or street scenes

The Eye's Ametropia

Myopia (Nearsightedness): Eye is too long; light focuses in front of the retina, requiring a minus lens
Hyperopia (Farsightedness): Eye is too short; light focuses behind the retina, requiring a plus lens

Astigmatism

Cornea or lens surfaces are not equally curved; light focuses at multiple points on the retina, causing blurry vision.

Objective Retinoscopy

Instant check of media: corneal, lens and vitreous opacities
Identify potential issues like keratoconus, anisocoria, or media opacities.

Retinoscopy's Question/Visual Aids

The patient is asked to focus on green to help relax accommodation

Recap of Retinoscopy

Emphasize the technique involved in retinoscopy and the rationale behind observing the reflection of the light
Show how a change to the sphere affects the reflection.
Briefly describe patient position and instructions

Tips for Better Retinoscopy

Emphasize the importance of the text book for better understanding of the technique
Encourage avoiding stress during application of the technique.
Use retinoscopy troubleshooting resources from Moodle
Suggest performing practice procedures to master techniques.

Refraction: What's Going On?

Spherical lens power presentation (examples)
Difference in principle meridians for cylindrical lenses
Explanation of how to specify this

Crossed Cyl: Technique & Tips

Technique for administering correction for crossed cylindrical lenses when performing refraction
Emphasize the importance of using the right technique
When to switch to alternative techniques.

Mistake and Correction for Cross-Cyl Procedures

Indicate the mistakes to avoid when applying the technique for correcting crossed cylindrical lenses.
Provide the correction steps for such scenarios

Refine Sphere

Refining the sphere should lead to improvement in VA.
Minimal change should be observed if done correctly.
Clinical decision making is important.
Using +1.00DS blur to check if the corrected vision is acceptable.

Plus 1 Blur

Description of the process of applying Plus 1 blur to refine vision and check for conditions such as latent hyperopia.

Pinhole Acuity

Description of pinhole acuity and when to use it as diagnostic tool.
Assessing vision and potential cause of reduction in vision.

Procedure for Monocular Refraction

Stepwise procedure for monocular refraction using the retinoscopy technique and other tools.

Monocular vs. Binocular Refraction

Describe the difference between monocular and binocular refraction
Indicate the additional steps needed for binocular refraction.

Subjective: BVS/circle of least confusion

Explain subjective tests, especially the BVS
Indicate the significance of maintaining the circle of least confusion on the retina
Suggest minimal accommodation effort by the patient

Subjective Best Vision Sphere (BVS) Procedure

Steps involved in finding the best vision sphere using subjective refraction methods.

Virtual Refraction: Best Vision Sphere Examples

Provide examples of virtual refraction results, including sphere, cylinder, axis, and VA.
Examples may include pre-presbyopic patients with no pathology.

Studying That Suits You

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Description

This quiz covers essential refraction techniques and the underlying optics crucial for clinical practice in optometry. You'll review advanced methods and components necessary for effective patient management. Ideal for 3rd year students and beyond, this quiz will help reinforce key skills and knowledge in clinical settings.