Basic Contact Lens Exam 1
What is a contact lens?
Small peice of plastic outfitted and worn at the the front surface of the attention to accurate
refractive errors and enhance imaginative and prescient
What are some motives to put on touch lenses?
1. Cosmesis: a few people do not like their appearance in glasses, change in iris coloration,
corneal scarring
2. Sports/Recreation or Inconvenience of glasses: uncomfortable, not able to put on,
damaged glasses, less subject of view
3. Treatment of refractive blunders: anisometropia, progressive myopia (orthokeratology or
corneal refractive therapy, reshapes cornea to decrease myopia), High ametropia
four. Treatment of eye disorder and disorders: ocular trauma (bandage lenses protects
cornea while recovery), environmentally induced disorders (dry eye), corneal disease
5. Sometimes best option post-surgical procedure: Post-PKP (corneal transplant can cause
irregular astigmatism), Post-refractive surgery (a few sufferers left with irregular astigmatism)
6. Pediatric use: excessive anisometropia (excessive chance of amblyopia), congenital
cataracts (aphasia), amblyopia (occluder contact lenses alternative to patching)
Contact lens examination "order"
1. Patient screening
2. Preliminary exam and measurements
three. Trial lens fitting
four. Lens dispensing
five. After-care
Indications for tender lenses
- Good tear first-class and amount
- Spherical refractive errors or low-slight astigmatism
- Athletes
- Unable to conform to inflexible gasoline-permeable lenses (GPs)
- Occasional wear
- Cosmetic tints to trade eye coloration
- Previous GP adherence
- Previous three and nine o'clock staining with GP's
- High motivation
Contraindications for Soft lenses
- Inflammation or disorder of the anterior section
- Poor hygiene
,- Lack of motivation
- Chronic hypersensitive reactions and antihistamines use
- Systemic diseases, which complicate touch lens put on
- Autoimmune disorder/immunocompromised
- Poor tear first-class and quantity
- Irregular astigmatism
- Radial keratotomy
- Dry, dusty environments
- Giant Papillary Conjunctivitis (GPC)
Types of Contact Lenses
1. Rigid lenses
- Hard plastic: PMMA, no oxygen transfer
- Gas permeable: acrylic, fluorine, and silicone which lets in for oxygen transfer; RGP
materials can be used for corneal lenses
2. Hydrophilic (tender lenses): HEMA = hydroxy-methylmethacrylate (larger than cornea)
- Soft plastic: plastic polymer and water, water lets in for oxygen passage
For an "best" contact lens suit, we want the lens to ____________ the corneal shape for
inflexible lenses or ____________ for tender lenses.
GP = Parallel
In order for a inflexible lens to parallel the corneal form, it too ought to flatten in outer edge
as properly
Soft lenses = drape flippantly
Soft lenses drape the globe so the curvature best wishes to be grossly comparable
Importance for an excellent contact lens match:
- Good consolation
- Good lens balance
- Minimal impact on corneal tissue
- Patient is seeing truly (readability)
Corneal shape may be described as:
Not spherical, closest is a prolate ellipse wherein it flattens gradually from center to limbus
Also may have one meridian steeper than the alternative
Explain the water ski effect in inflexible lenses.
Rigid lenses need a little edge raise to allow for tear alternate, superior capillary appeal,
save you erosion of cornea/damage to epithelium, so the PC should be a touch flatter than
the radius of curvature of the cornea in that region
, As a lens is mobbed nearer and in the direction of the eye, the ________________ of the
lens modifications.
Effective Power
When and why would you take powerful power (vertex any strength)?
Clinically, you need to vertex any strength four.00 D and above
Below this, the trade is much less than zero.25 D and is accordingly insignificant
If affected person has a refractive errors of -eight to -10 D there might be a trade of ~1.00D
while going from glasses to contacts
Explain effective powers in myopes and hyperopes in touch lenses vs. Specs.
Myopes - minus lens is extra powerful while moved closer to eye, will want much less energy
in CL then Spec
Hyperopes - plus lens is much less powerful when moved toward eye, will want extra
strength in CL than Spec
Recall from geometric optics, the ____________ of lens impacts the amount of
accommodative stimulus.
Vertex distance
What are the magnification effects in a myope vs. Hyperope in touch lenses?
Myopes can have much less minification with CLs and frequently record matters appearance
large with CLs
Hyperopes can have much less magnification with CLs and regularly document things seem
smaller with CLs
Retinal picture length is dependent upon ______________ and ___________________.
Lens electricity and the space from the eye
Greater the lens energy, the extra the impact on magnification (or minification)
Explain prismatic effect in specs vs. Touch lenses.
Recall that prism is caused every time the affected person looks via any factor other than the
optical middle of a lens.
With specs, myopes should converge greater at near due to the fact BI is prompted and
hyperopes converge less due to the fact BO is triggered at close to.
In touch lenses, the lenses move with the eye. Patient continually appears via optical center
of lens, so no prism is caused (this may be precise or horrific - have binocular assessment
before fitting touch lenses).
What is a contact lens?
Small peice of plastic outfitted and worn at the the front surface of the attention to accurate
refractive errors and enhance imaginative and prescient
What are some motives to put on touch lenses?
1. Cosmesis: a few people do not like their appearance in glasses, change in iris coloration,
corneal scarring
2. Sports/Recreation or Inconvenience of glasses: uncomfortable, not able to put on,
damaged glasses, less subject of view
3. Treatment of refractive blunders: anisometropia, progressive myopia (orthokeratology or
corneal refractive therapy, reshapes cornea to decrease myopia), High ametropia
four. Treatment of eye disorder and disorders: ocular trauma (bandage lenses protects
cornea while recovery), environmentally induced disorders (dry eye), corneal disease
5. Sometimes best option post-surgical procedure: Post-PKP (corneal transplant can cause
irregular astigmatism), Post-refractive surgery (a few sufferers left with irregular astigmatism)
6. Pediatric use: excessive anisometropia (excessive chance of amblyopia), congenital
cataracts (aphasia), amblyopia (occluder contact lenses alternative to patching)
Contact lens examination "order"
1. Patient screening
2. Preliminary exam and measurements
three. Trial lens fitting
four. Lens dispensing
five. After-care
Indications for tender lenses
- Good tear first-class and amount
- Spherical refractive errors or low-slight astigmatism
- Athletes
- Unable to conform to inflexible gasoline-permeable lenses (GPs)
- Occasional wear
- Cosmetic tints to trade eye coloration
- Previous GP adherence
- Previous three and nine o'clock staining with GP's
- High motivation
Contraindications for Soft lenses
- Inflammation or disorder of the anterior section
- Poor hygiene
,- Lack of motivation
- Chronic hypersensitive reactions and antihistamines use
- Systemic diseases, which complicate touch lens put on
- Autoimmune disorder/immunocompromised
- Poor tear first-class and quantity
- Irregular astigmatism
- Radial keratotomy
- Dry, dusty environments
- Giant Papillary Conjunctivitis (GPC)
Types of Contact Lenses
1. Rigid lenses
- Hard plastic: PMMA, no oxygen transfer
- Gas permeable: acrylic, fluorine, and silicone which lets in for oxygen transfer; RGP
materials can be used for corneal lenses
2. Hydrophilic (tender lenses): HEMA = hydroxy-methylmethacrylate (larger than cornea)
- Soft plastic: plastic polymer and water, water lets in for oxygen passage
For an "best" contact lens suit, we want the lens to ____________ the corneal shape for
inflexible lenses or ____________ for tender lenses.
GP = Parallel
In order for a inflexible lens to parallel the corneal form, it too ought to flatten in outer edge
as properly
Soft lenses = drape flippantly
Soft lenses drape the globe so the curvature best wishes to be grossly comparable
Importance for an excellent contact lens match:
- Good consolation
- Good lens balance
- Minimal impact on corneal tissue
- Patient is seeing truly (readability)
Corneal shape may be described as:
Not spherical, closest is a prolate ellipse wherein it flattens gradually from center to limbus
Also may have one meridian steeper than the alternative
Explain the water ski effect in inflexible lenses.
Rigid lenses need a little edge raise to allow for tear alternate, superior capillary appeal,
save you erosion of cornea/damage to epithelium, so the PC should be a touch flatter than
the radius of curvature of the cornea in that region
, As a lens is mobbed nearer and in the direction of the eye, the ________________ of the
lens modifications.
Effective Power
When and why would you take powerful power (vertex any strength)?
Clinically, you need to vertex any strength four.00 D and above
Below this, the trade is much less than zero.25 D and is accordingly insignificant
If affected person has a refractive errors of -eight to -10 D there might be a trade of ~1.00D
while going from glasses to contacts
Explain effective powers in myopes and hyperopes in touch lenses vs. Specs.
Myopes - minus lens is extra powerful while moved closer to eye, will want much less energy
in CL then Spec
Hyperopes - plus lens is much less powerful when moved toward eye, will want extra
strength in CL than Spec
Recall from geometric optics, the ____________ of lens impacts the amount of
accommodative stimulus.
Vertex distance
What are the magnification effects in a myope vs. Hyperope in touch lenses?
Myopes can have much less minification with CLs and frequently record matters appearance
large with CLs
Hyperopes can have much less magnification with CLs and regularly document things seem
smaller with CLs
Retinal picture length is dependent upon ______________ and ___________________.
Lens electricity and the space from the eye
Greater the lens energy, the extra the impact on magnification (or minification)
Explain prismatic effect in specs vs. Touch lenses.
Recall that prism is caused every time the affected person looks via any factor other than the
optical middle of a lens.
With specs, myopes should converge greater at near due to the fact BI is prompted and
hyperopes converge less due to the fact BO is triggered at close to.
In touch lenses, the lenses move with the eye. Patient continually appears via optical center
of lens, so no prism is caused (this may be precise or horrific - have binocular assessment
before fitting touch lenses).
