OPT 015: Clinical Refraction Module 1

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Questions and Answers

Which of the following are types of astigmatic charts? (Select all that apply)

Arrowheads Dials (correct)

Lebensohn’s Chart (correct)

Fan Chart (correct)

Fixed Clock or Sunburst Dial (correct)

When a plus lens is accepted, the case will always indicate hyperopia.

True

What is the tentative diagnosis when using the clock dial chart?

11.25°

What should you instruct a patient to do when looking at the astigmatic chart?

Report if the lines are equally blurred. Signup and view all the answers

The strongest plus and weakest minus that gives the best VA is considered the best _____

sphere Signup and view all the answers

Match the following methods with their appropriate usage:

Jackson-Cross Cylinder = Axis confirmation under fog Duochrome Test = Assessing lens clarity Vertical Prism Dissociation = Monocular balance Tentative Prescription = Initial refraction Signup and view all the answers

The Patient's responses during adjustment should create a back and forth movement within a wide range of powers.

False Signup and view all the answers

What is the recommended test distance for both fog elimination and confirming cylinder axis?

20 ft Signup and view all the answers

If a patient reports equally blurred lines, what does that indicate?

Free from astigmatism Signup and view all the answers

What is the purpose of Static Retinoscopy?

To objectively determine the distance refractive status of the patient’s eyes with accommodation relaxed. Signup and view all the answers

What does the movement of the light reflex indicate during retinoscopy with movement?

Myopia Signup and view all the answers

What does the Break Phenomenon indicate in static retinoscopy?

Astigmatic error Signup and view all the answers

Static Retinoscopy should be performed under bright illumination.

False Signup and view all the answers

The distance of the examiner from the patient converted to diopters is known as the _____ lens.

Working Distance Signup and view all the answers

What is the formula used for calculating the working distance lens?

D = 1/f Signup and view all the answers

What is the purpose of Binocular Subjective Refraction?

To balance the state of accommodation of the two eyes Signup and view all the answers

Presbyopia is considered an ametropic condition.

False Signup and view all the answers

If the reflex motion is slow and dim, the error is low.

False Signup and view all the answers

At what commonly accepted age does presbyopia typically begin?

45 years old Signup and view all the answers

What is the significance of measuring visual acuity after retinoscopy?

To assess the effectiveness of the refractive correction. Signup and view all the answers

What is indicated by a thick reflex within the pupil during retinoscopy?

Astigmatic error Signup and view all the answers

The condition of presbyopia is defined as a diminished amplitude of accommodation to the point where _____ vision at the near point is achievable.

clear or comfortable Signup and view all the answers

Dynamic Retinoscopy is used to determine the _____ of accommodation objectively.

lag Signup and view all the answers

Match the following methods with their description:

Successive Alternate Occlusion = A method of testing each eye separately Vertical Prism Dissociation = Technique using prisms to balance vision Polaroid Techniques = Uses polarized lenses to aid in refraction Blurring Techniques = Introduces blur to assess vision under different conditions Septum Techniques = Uses a physical barrier to isolate vision in one eye Signup and view all the answers

Which of the following symptoms are associated with hyperopia?

All of the above Signup and view all the answers

What lens power is subtracted from the total near power to find the reading correction?

Far prescription Signup and view all the answers

Patients with strabismus should undergo binocular balancing tests.

False Signup and view all the answers

What is the significance of introducing plus lenses simultaneously to both eyes during presbyopia testing?

To achieve clearer vision at near Signup and view all the answers

What is an autorefractor?

An autorefractor is a refraction carried out with an instrument that generally uses infrared light. Signup and view all the answers

What is subjective refraction?

Subjective refraction is the determination of the refractive state of the eye based entirely on the patient’s subjective responses or judgments. Signup and view all the answers

What are cycloplegics?

Cycloplegics are drugs that paralyze the ciliary muscle (accommodation). Signup and view all the answers

What is the goal and endpoint of refraction?

The goal and endpoint of refraction is to render the retina conjugate with optical infinity and to identify the lenses that allow the patient to achieve clear and comfortable vision. Signup and view all the answers

Which of the following types of refraction relies on the patient's response?

Subjective Refraction Signup and view all the answers

Retinoscopy is considered more reliable than subjective refraction for uncooperative patients.

True Signup and view all the answers

What is static retinoscopy?

Static retinoscopy is when the patient is asked to fixate at a distant object. Signup and view all the answers

What is dynamic retinoscopy?

Dynamic retinoscopy is when the patient is asked to fixate at near and the accommodation is at its maximum. Signup and view all the answers

What does the point of neutrality refer to in retinoscopy?

The point of neutrality is the point at which the motion of the reflex cannot be detected and changes from with motion to against motion. Signup and view all the answers

Match the following types of refraction with their descriptions:

Objective Refraction = Determination based on optical principles without patient feedback Subjective Refraction = Determination based on patient’s responses Cycloplegic Refraction = Determination using drugs that paralyze accommodation Automated Refraction = Computerized measurement of refractive error Signup and view all the answers

What is the purpose of the fixation target in clinical refraction?

To allow the patient to focus while the examiner measures refractive error. Signup and view all the answers

The distance from the examiner’s eye to the patient when performing Mohindra's Near Retinoscopy is about ____ centimeters.

40 Signup and view all the answers

The Nott technique is useful only for adults.

False Signup and view all the answers

What should the examiner do if the child does not fixate on the light during examination?

Stimulate the infant's attention by making sounds. Signup and view all the answers

Which of the following methods can be used to test for accommodative insufficiency?

All of the above Signup and view all the answers

What is the Monocular Estimation Method (MEM) used for?

To objectively measure the accommodative response to near working distance. Signup and view all the answers

In the procedure of Subjective Refraction, the goal is to determine the combination of spherical and cylindrical lenses necessary to bring the eyes to ____.

infinity Signup and view all the answers

What does a measurement of lag equal to or greater than +1.00 indicate?

Accommodative insufficiency or infacility. Signup and view all the answers

Fogging is used to enhance the patient's accommodation.

False Signup and view all the answers

What is the first step in the Monocular Subjective Refraction process?

Sphere Used to Fog Signup and view all the answers

In Chrome Retinoscopy, what is the essential component used to measure accommodation lag?

A mobile target. Signup and view all the answers

Match the following retinoscopy techniques with their descriptions:

Nott Technique = Used for infants and toddlers. MEM = Measures accommodative response to near. Chrome Retinoscopy = Measures accommodation lag with a mobile target. Radical Retinoscopy = Used when the retinoscopic reflex is faint and indistinct. Signup and view all the answers

What is the significance of the 20-20-20 rule for patients?

It helps to prevent eye strain by encouraging regular breaks during near tasks. Signup and view all the answers

Study Notes

Clinical Refraction Overview

Optometers serve as autorefractors and visual analyzers, utilizing infrared light for refraction.
Retinoscopes are objective instruments assessing refractive status through fundus reflex observation.
Refraction is defined by Michel Millodot as measuring and correcting eye refractive errors.

Types of Refraction

Subjective Refraction: Based on patient feedback; involves comparing lenses to determine the best visual acuity.
Cycloplegic Refraction: Utilizes cycloplegics to paralyze ciliary muscles, facilitating accurate eye state determination.
Stenopaic Refraction: Involves using a stenopaic slit for refraction assessment.
Automated Refraction: Computerized measurements of refractive errors, emphasizing both objective and subjective accuracy.

Process and Techniques

The objective is to align the retina with optical infinity, achieving clear visual outcomes.
Includes three divisions: Starting Point (info gathering), Refinement (testing predictions), Endpoint Techniques (binocular balance).
Employs various methods including phoropter tests and trial frame techniques.

Retinoscopy Insights

Provides an objective assessment of refractive status without needing subjective patient input, critical for uncooperative individuals.
Can determine lag of accommodation and detect ocular media opacities.
Key historical contributors like Sir William Bowman and Parent popularized retinoscopy techniques.

Retinoscopy Advantages

Acts as a reliable starting point for subjective refraction.
Effective in detecting latent hyperopia and various accommodation dysfunctions.
Offers an independent basis for comparison against subjective refraction results.

Instrumentation and Techniques in Retinoscopy

Illumination Systems: Can use an external light source or self-illuminating designs for reflex observation.
Observation Systems: Include a peephole to gauge the fundus light reflex and assess the refractive condition.
Types of Retinoscopes: Varies based on light sources (luminous or non-luminous) and usage of different mirrors.

Static vs. Dynamic Retinoscopy

Static Retinoscopy: Patient focuses on a distance object, evaluating the far point of vision.
Dynamic Retinoscopy: Patient focuses on near objects, engaging accommodation, easing measurements of lag.

Factors Affecting Retinoscopic Results

Clarity, intensity, speed of reflex motion, and the form and shape of pupil reflex significantly influence outcomes.
Fundamentally important to adjust mirror types and distances during examination for accuracy.

Final Insights

Point of Neutrality: Indicates where the reflex motion changes from 'with' to 'against', essential in determining true refractive error.
Retinoscopy remains a cornerstone in optometric assessments, especially for patients with compromised ability to provide subjective feedback.### Static Retinoscopy Overview
Adjust interpupillary distance (IPD) for accurate distance measurement.
Instruct the patient to keep both eyes open during retinoscopy; ask about obstructions to fixation target.
Examiner also keeps both eyes open; uses right eye for patient’s right eye and vice versa.

Static Retinoscopy Procedure

Hold the retinoscope 20 inches (or 16 inches) from the patient's eye.
Use retinoscopic lens in the phoropter to eliminate the unexamined eye.
Scope both vertical (90th meridian) and horizontal (180th meridian) meridians.

Error Detection

Continuous reflex indicates spherical error; observe movement with plus or minus lens to determine error type.
Spherical errors detected involve reflex motion's direction:
- Plus lens indicates "with" motion.
- Minus lens indicates "against" motion.

Working Distance Lens (WDL)

WDL is the distance of the examiner from the patient, expressed in diopters.
Formula: D = 1/f; for example, 40 inches corresponds to 2.50D.

Break Phenomenon

Observed when reflex within the pupil is not continuous with the streak on the eye, indicating astigmatic error.

Thickness Phenomenon

Changes in reflex thickness during rotation hint at astigmatic versus spherical error; constant thickness indicates spherical error.

Skew Phenomenon

Disalignment of streak with principal meridians points to astigmatic errors; if aligned, reflex moves parallel to the streak.

Neutralizing Astigmatic Errors

Identify principal meridians, neutralize using a combination of spherical and cylindrical lenses based on motion detected.
Record findings to adjust refractive status accurately.

Dynamic Retinoscopy

Conducted to assess the lag of accommodation at near.
A lag greater than +0.75D indicates insufficient accommodative response, while under +0.50D suggests over-accommodation.

Measurement Techniques

Nott Technique: Neutralizes reflex with a card at 40 cm, moving closer to determine neutrality.
Mohindra’s Near Retinoscopy: Examines distance refractive error using light from the retinoscope as a target, useful for infants.
MEM Retinoscopy: Measures accommodative response using monocular estimation, focusing on the fixation target.

Key Considerations

Dim lighting enhances pupil dilation for better observation.
Proper understanding of eye movement and lens effect is crucial for accurate retinoscopy findings.
Different methods serve various patient needs and conditions (e.g., adults vs infants).

FAQs

Astigmatism affects nearly 2/3 of the population, often asymptomatic.
Importance of understanding reflex movements for diagnosing refractive errors effectively.### Retinoscopy Techniques
Chrome Retinoscopy: Introduced by Bobier and Sivak in 1980, it measures accommodative lag using a mobile target.
Bell Retinoscopy: Developed by Apell in 1975, this method uses a filter to limit light wavelengths entering the examiner's eye.
Radical Retinoscopy: Used when the retinoscopic reflex is faint; performed closer than usual (as close as 20 cm or 10 inches) to address issues from small pupils or cataract.

Testing for Accommodative Insufficiency

Lag can be measured using binocular cross-cylinders and near point retinoscopy.
A lag of +1.00 or greater indicates possible accommodative insufficiency.

Subjective Refraction

Determines the necessary combination of spherical and cylindrical lenses to achieve best visual acuity at infinity.
Phoropter: A lens holder with controls for spherical and cylinder adjustments, allowing efficient lens changes.
Fogging Technique: Uses plus lenses to relax accommodation, assessing the patient's refractive error.

Lens Controls in the Phoropter

Spherical Lens Control: Range of +20D to -20D; controls for adding plus or minus sphere.
Minus Plano-Cylinder Control: Adjusts cylindrical lenses, displaying cylinder and axis settings.
Auxiliary Lens Knob: Includes different apertures for controlling viewing conditions.

Monocular Subjective Refraction Steps

Fogging: Observe visual acuity (VA) before applying the strongest plus lens until vision is slightly worse.
Tentative Diagnosis: After fogging, if plus lenses improve vision, suspect hyperopia, if minus improves, suspect myopia.
Visual acuity checking and adjusting lenses continue until best possible VA is established.

Determination of Cylinder Under Fog

Astigmatic charts help assess if a patient is astigmatic by evaluating clarity of lines.
Different chart types include Fixed Clock Dial, Sunburst Dial, and Fan Chart.

Confirmation of Cylinder Axis

After establishing a tentative axis, the Jackson-Cross Cylinder (JCC) verifies the correct cylinder axis by rotating it until all lines appear equally blurred.

Common Cases and Prescriptions

Patient Examples:
- An 18-year-old male with 20/50 visual acuity; tentative diagnosis of myopia with a prescription of -1.00sph.
- A 25-year-old female with headaches related to vision, presenting hyperopia with a proper fogging lens of +1.25sph.

Additional Considerations

Importance of subjective refraction in optometry for accurate prescriptions.
Quality patient experience leads to repeat visits and referrals, enhancing clinic reputation.
Educating patients on relaxation techniques, such as the 20-20-20 rule, helps improve comfort during assessments.

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Description

Test your knowledge of Clinical Refraction in Optometry with this quiz focused on Module 1. This module introduces autorefractors and the basics of refraction. Prepare for your Doctor of Optometry studies in the third year, first semester.