5.3.3 Flashcards
What is aphakia? And its side effects
Absence of lens in the eye
Can lead to =
High hyperopia
Loss of accommodation
Glare and photophobia due to increased retinal illumination
How do Rigid Gas Permeable (RGP) lenses help in aphakia?
RGP lenses provide a rigid surface that corrects the refractive error by focusing light properly on the retina.
They restore focusing power, providing clear and sharp vision.
What is high ametropia?
High ametropia involves significant refractive errors like high myopia or hyperopia that cannot be easily corrected with standard lenses.
Example: Rigid Gas Permeable (RGP) Lenses are effective for correcting high ametropia.
What role do Rigid Gas Permeable (RGP) lenses play in high ametropia?
RGP lenses maintain a smooth surface, providing sharp and clear vision, and reshape the corneal surface to correct the refractive error.
They also reduce astigmatism, which is common in high ametropia.
Define keratoconus.
Keratoconus is a condition where the cornea becomes thin and bulges outward, leading to distorted vision.
Example: Scleral lenses are commonly used for keratoconus.
How do scleral lenses help patients with keratoconus?
Scleral lenses vault over the irregular cornea and rest on the sclera, creating a fluid reservoir to correct distorted vision.
They provide comfort and stability.
What issues may arise after cataract surgery?
Patients may experience residual refractive errors or irregularities in the cornea.
Example: Rigid Gas Permeable (RGP) Lenses are used to correct these issues.
How do RGP lenses assist after cataract surgery?
RGP lenses correct residual astigmatism or refractive error by compensating for changes in the cornea.
They ensure light is properly focused on the retina.
What complications can arise from refractive surgeries like LASIK or PRK?
Residual refractive errors, dry eyes, or corneal irregularities may occur.
Example: Rigid Gas Permeable (RGP) Lenses are often used to correct these issues.
How do RGP lenses help after LASIK or PRK?
RGP lenses provide a smooth, stable surface over the cornea, correcting imperfections caused by the surgery.
They offer excellent vision quality, especially for patients with irregular corneal shapes post-surgery.
What are piggyback lenses?
Piggyback lenses are a combination of two lenses worn together to provide correction for certain conditions.
This technique involves placing a soft contact lens on the eye first, followed by a rigid gas permeable (RGP) lens.
What are common uses for piggyback lenses?
Common uses include:
* Keratoconus
* Residual refractive errors
* Comfort and stability for corneal irregularities.
How do piggyback lenses help patients with keratoconus?
The soft lens provides comfort, while the RGP lens offers optical clarity by correcting the refractive error.
The RGP lens creates a smooth, rigid surface.
What is the fitting technique for piggyback lenses?
The fitting starts with the soft lens for comfort, followed by the RGP lens placed on top.
The RGP lens should be fitted slightly larger to avoid displacement.
What patient advice is given for piggyback lenses?
Patients are advised to follow a strict cleaning routine for both lenses and have regular follow-ups.
This helps avoid irritation or infection.
What is the Peripheral Defocus Theory?
Myopia control lenses create peripheral defocus in the peripheral retina to slow down eye growth.
Peripheral defocus is achieved by altering the shape of light entering the eye, focusing it behind the retina in peripheral areas.
How do myopia control lenses work in relation to peripheral defocus?
They focus light behind the retina in the periphery, signaling the eye to slow elongation.
In a normal eye, light focuses directly on the retina. In a myopic eye, light focuses in front of the retina.
What are Multifocal Lenses?
Lenses with concentric rings providing different focal points for clear central vision and peripheral defocus.
Examples include MiSight contact lenses.
How do concentric rings in multifocal lenses help with myopia control?
They induce defocus at the periphery, reducing myopic defocus and slowing axial elongation of the eye.
The central zone provides clear vision while peripheral rings induce defocus.
What is the purpose of managing axial length in myopia control?
To reduce axial elongation of the eye, the main driver of myopia progression.
Myopia control lenses aim to alter refractive error to reduce strain on the eye’s focusing system.
How do myopia control lenses reduce the stimulus for eye elongation?
By providing altered focal points that lessen the need for the eye to elongate for better focus.
This slows myopia progression over time.
What are Orthokeratology (Ortho-K) lenses?
Lenses worn overnight to reshape the cornea temporarily, controlling myopia progression.
They help the eye focus properly during the day without glasses or contact lenses.
How do Ortho-K lenses reshape the cornea?
They flatten the cornea slightly, particularly in the central portion, reducing myopic refraction.
This also decreases peripheral defocus and signals for axial growth.
What is the role of Enhanced Depth of Field in myopia control lenses?
To create a more consistent focus across the retina, reducing stimuli for eye elongation.
An example is defocus-incorporated soft contact lenses (DISC).
How do lenses with enhanced depth of field mitigate axial eye growth?
They limit excessive accommodation or eye strain, which contributes to myopia progression.
This provides a visual experience with consistent focus across a range of distances.
