Ocular Optics II: Anisometropia and Aniseikonia
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Questions and Answers

What is a characteristic of binocular vision in older children or adults?

  • Normal binocular vision rarely exists. (correct)
  • Binocular vision improves with age.
  • Normal binocular vision is prevalent.
  • Binocular vision can be easily corrected.

How does the effectiveness of lenses for anisometropia differ?

  • They are equally effective for both distance and near vision.
  • They differ only for near vision.
  • They improve visual acuity across all distances.
  • They are equally effective only for distance vision. (correct)

What complication arises when the visual axes move away from the optical center (OC) of lenses with unequal powers?

  • Reduced clarity of vision.
  • Prismatic imbalance occurs. (correct)
  • Improved depth perception.
  • Increased accommodation requirements.

According to Prentice's rule, how is prismatic imbalance calculated?

<p>Using the distance between the optical center of the lenses and the visual axes. (A)</p> Signup and view all the answers

What does horizontal conjugate movement require from the visual system?

<p>The visual system must compensate for the resultant prismatic imbalance. (B)</p> Signup and view all the answers

What is the primary aim when correcting anisometropia?

<p>To reduce monocular distortion with minimal discomfort (D)</p> Signup and view all the answers

What is aniseikonia primarily characterized by?

<p>Disturbances in binocular vision (B)</p> Signup and view all the answers

Which factor is NOT considered important in the management of lens prescriptions?

<p>The patient's favorite color (D)</p> Signup and view all the answers

Which type of image size difference does meridional aniseikonia represent?

<p>Image size changes asymmetrically in one meridian (D)</p> Signup and view all the answers

How can cylinder axes be adjusted if they are oblique?

<p>They can be rotated toward the closest standard axis which is 180° or 90° (D)</p> Signup and view all the answers

Which of the following best describes symmetrical differences in aniseikonia?

<p>Image size changes in all meridians equally (D)</p> Signup and view all the answers

What is the significance of the value 1.523 in the calculations provided?

<p>It indicates the index of refraction of the lens material. (B)</p> Signup and view all the answers

Which of the following is a consideration regarding the patient's personal preferences in lens management?

<p>The patient's interest in the appearance of the glasses (D)</p> Signup and view all the answers

How does the vertex distance affect the spectacle magnification when compared to contact lenses?

<p>Longer vertex distance usually reduces magnification for spectacles compared to contact lenses. (C)</p> Signup and view all the answers

What should be minimized when making corrections for anisometropia?

<p>Monocular distortion with comfort (B)</p> Signup and view all the answers

When discussing aniseikonia, which is an example of asymmetrical differences?

<p>A pronounced difference between the images of two eyes (D)</p> Signup and view all the answers

What is the calculated percentage change in size for the lens with a front surface power of +8.00D?

<p>-2.0% (A)</p> Signup and view all the answers

What effect does anisometropia have on vision that may lead to aniseikonia?

<p>It results in unequal image sizes for the two eyes (A)</p> Signup and view all the answers

What happens to the image size if a person wears spectacles with plus power compared to contact lenses?

<p>Plus power spectacles create a magnified image compared to contact lenses. (A)</p> Signup and view all the answers

In the example, what is the front surface power for the lens that results in a size change of +4.4%?

<p>+8.00D (C)</p> Signup and view all the answers

What is the primary definition of anisometropia?

<p>A condition where the spherical equivalent refraction (SER) of both eyes differs by 1.00 D or more (D)</p> Signup and view all the answers

What can uncorrected anisometropia potentially lead to in children under the age of 6?

<p>Functional amblyopia (C)</p> Signup and view all the answers

Which of the following is NOT a symptom associated with aniseikonia?

<p>Increased contrast sensitivity (A)</p> Signup and view all the answers

What is the significance of measuring image size differences in anisometropia?

<p>To identify potential aniseikonia (A)</p> Signup and view all the answers

What aspect of spectacle magnification is vital in managing aniseikonia?

<p>Comparative analysis with contact lens magnification (A)</p> Signup and view all the answers

Which of the following can occur as a result of uncorrected anisometropia?

<p>Functional amblyopia (C)</p> Signup and view all the answers

Which mechanism is usually affected in cases of functional amblyopia due to anisometropia?

<p>Accommodation system (C)</p> Signup and view all the answers

Which intervention is aimed at minimizing induced aniseikonia?

<p>Prescribing glasses to equalize magnification (B)</p> Signup and view all the answers

What is the spectacle power calculated in the context provided?

<p>-11.36D (B)</p> Signup and view all the answers

Which equation correctly represents the calculation for %SM?

<p>%SM = (SM-1)(100) (B)</p> Signup and view all the answers

What condition is indicated by equal keratometer findings for both eyes?

<p>Axial anisometropia (C)</p> Signup and view all the answers

If the spectacle power for one eye is -11.36D and for the other is -10.00D, what type of anisometropia is suggested?

<p>Unequal axial anisometropia (D)</p> Signup and view all the answers

What is the Relative Spectacle Magnification (RSM) used to compare?

<p>Retinal image sizes between eyes (C)</p> Signup and view all the answers

Which method is typically employed to reduce monocular distortion without sacrificing visual acuity (VA)?

<p>Contact lenses for astigmatism (B)</p> Signup and view all the answers

In the provided calculations, what is the significance of a positive percentage SM?

<p>Implies an increase in effective power (D)</p> Signup and view all the answers

What does the formula RSM = image size for a corrected ametropic eye / image size for a standard emmetropic eye represent?

<p>The relative size of retinal images (D)</p> Signup and view all the answers

Flashcards

Anisometropia

A condition where the eyes have different refractive powers.

Prismatic imbalance (PE)

A shift in the visual axis caused by lenses of unequal power.

Horizontal PE

Horizontal shift in the visual axes due to unequal lens powers.

Prentice's rule

A calculation used to determine the effect of unequal powers on the visual axes.

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Accommodative system and near vision

The lens's ability to change focus for different distances is not evenly affected in anisometropia for near vision.

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Anisometropia definition

Difference in the refractive power of the two eyes, greater than 1.00 diopter, potentially causing problems.

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Anisometropia problems (uncorrected)

Can lead to functional amblyopia and binocular vision problems, especially in children under 5 or 6 years.

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Anisometropia problem (Corrected)

Despite correction, problems can persist related to accommodation, functional amblyopia, binocular vision and vergence issues.

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Functional amblyopia

Reduced vision in one eye, often the result of differing focus or other visual issues with the eyes, especially in young children.

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Binocular vision problem

Difficulties coordinating both eyes for a single image, potentially arising from diverse refractive powers of the eyes.

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Accommodation

The ability of the eyes to adjust and change their focus to see objects at different distances.

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Vergence system

The eye's coordination that controls the alignment of both eyes and enables binocular vision.

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Retinal image size

The size of the image produced on the retina of the eye, potential issues in anisometropia.

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Aniseikonia

A difference in the size or shape of the images seen by each eye, causing disturbances in binocular vision.

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Symmetrical Aniseikonia

When the image seen by one eye is either larger or smaller than the image seen by the other eye in all directions.

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Meridional Aniseikonia

When the image seen by one eye is either larger or smaller than the image seen by the other eye in a specific direction (e.g., vertically).

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Overall Aniseikonia

A type of symmetrical aniseikonia where the entire image seen by one eye is larger or smaller than the image seen by the other eye.

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Asymmetrical Aniseikonia

When the image seen by one eye is larger or smaller than the image seen by the other eye in specific areas, but not in others.

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Spectacle Lens Magnification

The change in the size of the retinal image when wearing spectacles compared to no lenses.

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Contact Lens Magnification

The change in the size of the retinal image when wearing contact lenses compared to no lenses.

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Plus Lenses and Magnification

Plus lenses, both in spectacles and contact lenses, cause magnification of the retinal image.

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Minus Lenses and Magnification

Minus lenses, both in spectacles and contact lenses, cause minification of the retinal image.

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Spectacle vs. Contact Lens Magnification

The magnification effect of plus and minus lenses is different between spectacles and contact lenses due to vertex distance.

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Anisometropia correction goal

To minimize distortion in the visual image perceived by each eye while maintaining acceptable visual acuity.

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Anisometropia correction methods

Adjusting cylinder power, rotating cylinder axes, or both, aiming for a compromise between visual acuity and minimizing distortion.

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Factors in anisometropia management

Patient age, previous corrections, occupation, temperament, appearance preference, cost, and complaint severity all influence the best solution.

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Vertex distance and aniseikonia

The distance between the lens and the cornea can significantly impact retinal image size and contribute to aniseikonia, especially in anisometropia.

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Minimizing aniseikonia in anisometropia

Using contact lenses, as they sit directly on the cornea, can help minimize the difference in image size compared to spectacles.

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Relative Spectacle Magnification (RSM)

The ratio of the retinal image size for a corrected ametropic eye to the image size for a standard emmetropic eye.

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Axial Anisometropia

A type of anisometropia where the difference in refractive power is caused by different axial lengths of the eyes.

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Refractive Anisometropia

A type of anisometropia where the difference in refractive power is caused by different curvatures of the cornea or lens.

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Equal Keratometer Findings

Indicates Axial Anisometropia, meaning the difference in eye length is causing the anisometropia.

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Unequal Keratometer Findings

Indicates Refractive Anisometropia, meaning the difference in the eye's shape is causing the anisometropia.

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Anisometropia Management: Spectacles

Can be used to correct anisometropia, but may lead to problems with retinal image size and binocular vision.

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Anisometropia Management: Contact Lenses

Can provide a better solution than spectacles for anisometropia, as they more closely mimic the natural shape of the eye.

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Astigmatism Management

Managing astigmatism in anisometropic patients can reduce problems with binocular vision.

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Study Notes

Ocular Optics II

  • OPT3054 course covers anisometropia and aniseikonia
  • Anisometropia: difference in refractive error of 1.00D or greater, between the two eyes. It can cause issues in both uncorrected and corrected states.
  • Factors related to anisometropia:
    • Children: Functional amblyopia, binocular vision problems
    • Adults: Accommodation system issues, no binocular vision, vergence system issues, retinal image size.
  • Uncorrected anisometropia:
    • Eyes may accommodate, making one or both retinal images in focus.
    • Can lead to functional amblyopia in children under 5-6 years old.
    • Can cause binocular vision problems and poor stereopsis in older children and adults.
  • Corrected anisometropia :
    • Lens effectivity differs for different fixation distances.
    • Lenses that work equally well for distance vision might not work equally well for near vision.
  • Horizontal PE:
    • Unequal lens powers cause prismatic imbalance.
    • Imbalance can be calculated by Prentice's rule if needed.
  • Vertical PE:
    • Eyes have limited vertical movement.
    • Significant vertical imbalance is seen primarily in bifocal and multifocal wearers, and in patients doing extensive near work.
  • Management of anisometropia:
    • Lower the distance OC
    • Single vision lenses for reading
    • Dissimilar bifocal segments
    • Compensated bifocal segments
    • Prism segments
    • Slab-off lenses
    • Fresnel press-on prism
    • Contact lenses
  • Aniseikonia:
    • Defined as differences in size or shape of the retinal images in the two eyes.
    • Types:
      • Symmetrical: Overall, meridional (vertical, horizontal, oblique) image size differences
      • Asymmetrical: Increase/decrease in image size, one meridian, all directions, barrel distortions, pincushion distortions.
  • Symptoms of aniseikonia
    • Mimic symptoms of undercorrected/oculomotor imbalance
    • Patients perceive issues with their eyes rather than distortion of space, such as: asthenopia, headaches, photophobia, dizziness, and nervousness
    • Symptoms persist even after monocular occlusion
  • Spectacle Magnification
    • SM = retinal image size (corrected eye) / retinal image size (uncorrected eye)
    • Percentage SM = (SM-1) * 100
    • Angular Magnification = SM * (Ms / Mp) , where Ms is the power of the front surface of the lens and Mp is the back vertex power of the composite lens.
  • Relative Spectacle Magnification (RSM)
    • Ratio of retinal image size for a corrected ametropic eye to a standard emmetropic eye.
    • A-SCAN eye ball length findings.
    • Equal: axial anisometropia
    • Unequal: refractive anisometropia
  • Management of Anisometropia
    • Factors to consider regarding patient: age, nature of previous correction, occupation/hobbies, temperament, interest in appearance of glasses, cost of correction, nature of the patient's complaint.

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Anisometropia and Aniseikonia PDF

Description

This quiz explores the concepts of anisometropia and aniseikonia as covered in the OPT3054 course. It addresses the impacts of refractive error differences on vision, detailing factors affecting children and adults. Understand the implications of uncorrected and corrected anisometropia in vision health.

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