Brainscape's Knowledge GenomeTM


Top Flashcards (Certified)
All Flashcards

Contact Lenses > Week 10 > Flashcards

Week 10 Flashcards

1
Q

Threshold for high ametropia

A

Myopia and hyperopia above and equal to 10D
High astigmatism more than 4D

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What’s the problem with a high minus lens and what’s the carrier used

A

Thicker in the edges and lens hitch under upper eyelid, carrier is Plano or positive to reduce high riding lens

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What is the issue with high plus lens and what carrier is used

A

Thicker in centre, gravity makes lens drop, negative carrier provides lid attachment

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Fitting soft lenses in high ametropia

A

SiHy,
modality frequent replacement 3/12ly
, highest power available minus 30D.
TD larger to help with centration = larger by 0.30-0.50mm

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What are the long term issues using hydrogel lenses for high ametropia

A

Oedema and neovascularisation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Fitting strategies for RGP lens for high ametropia

A

Fit the mean K
fluorescein shows apical clearance
Aim for Lid attachment to assist with centration
Larger TD- instead of -2mm do -1.50mm from HVID

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

RGP lens fitting for aphakic corneas

A

BOZR between mean and steepest k to help with stability and centration
Fluorescein- apical clearance
TD large between 8.8-10.5
Lenticular - Negative carrier
Centration -often superior or temporal
If sits low increase TD
Avoid BST
Toric peripheries for high astigmatism
Need tint and UV block

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What is the BOZR AND TD OF Corneoscleral lenses in aphakic corneas

A

TD- 11.5-13mm - larger
BOZR- usually 0.50 flatter than K - apical touch

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Soft lens fitting in aphakia

A

Hy ( med to high wc)
Large TD 13-16mm
BOZR 0.3mm flatter than K for TD upto 14mm
Can be continuous wear- 3-6/12ly replacement
SiHy-flatter due to high modulus so stiffer

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Things to consider with aphakic children

A

Initially EW/CW until DW can be an option ( handling issues)
RGP above 5 years old
School children need over specs (bifocals,PPLS)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Advantages of cosmetic contacts - tints

A

Decreases adaptive photophobia (albinism or aphakia)
Increases handling
Enhances colour vision/ perception
Enhances or change natural eye colour

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Disadvantages of cosmetic contacts tints

A

Decreases night vision
Decreases comfort
RGP limited options
Photochromic - light/ dark transition speed is slow

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Advantages of hand painted cosmetic contacts

A

Aniridia
Trauma
Specialist needs

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Disadvantages of hand painted cosmetic lenses

A

Limited material compatibility with rigid and soft
Lower Dk and Dk/t
Lower comfort and WT as len thicker
High risk of corneal oedema and neovascularisation
Tunnel effect can restrict FOV
Can’t use fluorescein to asses opaque rgp lenses
Rgp may need fenestrations as increase in dimpling /deposits /frothing and reduced comfort

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Parameters needed for cosmetic contact lenses

A

RGP: TD larger than 11.5 (bigger)
Soft: iris diameter standardised TD 11.5
Pupil size: 5-6mm (bigger)
Black pupil: occlusion or prosthetic purposes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Options for cosmetic cls

A

Opaque or semi opaque
- laminated insert rgp
Iris matching to photograph of other eye or iris buttons

Tints
Depends on iris colour and ambient lighting - hard to change brown iris
- can be solid tint or printed matrix ( natural effect)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

How is Colour vision enhanced in cosmetic lenses

A

For colour blind people or people with colour deficiency
X- chrome lenses help perceive the difference in colours by increasing contrast

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

Irregular corneas

A

Corneal ectasia - thinning of stroma and loss of elasticity of connective tissue fibres
-Keratoconus - conical and central cornea
-Keratoglobus - whole cornea
- pellucid marginal degeneration - peripheral cornea

Corneal distortion
- scarring and refractive surgery

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

What is keratoconus

A

Progressive, non-inflammatory corneal disease characterised by central or paracentral corneal thinning and ectasia of the cornea resulting in a high degree of irregular astigmatism

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

Features/ causes of keratoconus

A

Presents in teens
Bilateral but asymmetric
Progressive
Autosomal dominant
Systemic causes: downs, EDS, marfans
Ocular causes: vernal KC, blue sclera, aniridia, eye rubbing, floppy eyelid syndrome, RP

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

Clinical features and management of keratoglobus

A

Extremely rare and from birth or acquired onset

Severe version of oval cone ( late stage)

Clinical features: globular ectasia and acute hydrops (sudden onset of corneal oedema) is rare
Cornea more prone to rupture or mild trauma

Management: surgical management is difficult
CL often unsatisfactory
Intacts and corneal cross linking CXL can be useful
Protect eyes from trauma

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

Symptoms of keratoconus

A

Asymptomatic in early stages
Visual distortion/ visual loss in one eye due to irregular astigmatism
Myopia and many cases corneal scarring
Ghosting/ monocular diplopia due to irregular astigmatism
Photophobia and flare especially at night

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

Early Signs of keratoconus

A

Progressive myopia and irregular astigmatism
Scissoring ret reflex
Distorted keratometry mires
Distorted placido rings
Inferior steepening in topography graphs

24
Q

Later signs of keratoconus

A

Vogts striae (vertical lines)
Fleishers ring (partial or complete iron ring surrounding corneal periphery)
Prominent corneal nerves

25
Other/worse signs of keratoconus
Corneal scarring Munsons sign Thinned cornea Acute hydrops (corneal oedema)
26
2 Types of keratoconus
1. Nipple or centred cone- within 2mm of centre of cornea. As it progresses the cone becomes steeper and smaller in diameter (like a football) 2. Oval cone- centre outside the central 2mm of the cornea (usually temporal). As it progresses it becomes steeper and larger in diameter (like a rugby)
27
Classification of keratoconus
Mild is less than 48D (k is 7.03mm) Moderate 48-54D (7.03-6.25mm) Severe is above 54D (6.25 and steeper)
28
Surgical Management of keratoconus
Corneal cross linking (CXL) slows progression Intact- when KC is stable but px can’t achieve good vision with specs or CLs Corneal transplantation-severe KC or when stable but px can’t achieve good vision or intolerant to CLs
29
Non surgical management of keratoconus
Px education No rubbing eyes Ocular lubricants Topical anti allergics for allergic pxs CLs for better vision - corneo rgp , corneo-scleral , scleral , hybrid , piggy-back
30
Clinical features and management of pelucid marginal degeneration
Rare, progressive peripheral corneal thinning Bilateral Adulthood Features: effects inferior cornea NO FLEISCHER RING OR VOGTS STRIAE Management: spectacle and CLs CXL keratoplasty
31
What astigmatism does PMD induce
ATR because it’s steeper in the 180 degrees and flatter in 90 degrees Inferior thinning so ATR
32
Advantages of Soft lenses for irregular corneas
Standard soft toric in early stages Excellent comfort, disposability and lower initial cost
33
Disadvantages of soft lenses for irregular corneas
Inability to mask moderate/ severe irregular astigmatism High order aberrations Compromise quality of vision?
34
Advantages of RGPS cls for irregular corneas
Provide better vision Correct astigmatism and optical aberration Better than soft High O2 transmissibility Greater tolerance in px with dry eyes
35
Disadvantages of RGP for irregular corneas
Poor fitting can damage cornea Do not fit FLAT cls !
36
What are the risks of a flat fit RGP on an irregular cornea
Cause abrasions and scarring
37
What are the risks of a steep RGP on an irregular cornea
Risk of corneal steepening, imprinting of mid periphery, 3 and 9 o clock staining, poor vision
38
What is a 3 point touch for a RGP fitting on irregular cornea
Ideal fit Lens support and bearing shared between the corneal apex and the para central cornea
39
Advantages of corneo-scleral cls
Comfort since lens edges tuck under the lids -larger than standard RGP More stable vision Not easily lost larger BOZD
40
Disadvantages of corneo-scleral cls
Limbal impingement (interfere with limbus stem cells) from the lens periphery and with the risk of stem cell damage More complicated to design and fit
41
What are scleral cls
Scleral cls rest solely on the sclera. It is intended to vault the cornea and in its entirely to retain a fluid reservoir between the lens and the eye Small diameter 14.5-18mm Large diameter 19-24mm
42
Advantages of scleral cls
Large TD eliminates lid sensation and issues associated with lens movement Lower risk of corneal damage compared to RGP due to absence of corneal contact and minimal movement The liquid reservoir keeps ocular surface hydrated, reduces ocular discomfort and protects the cornea
43
What conditions can scleral cls be beneficial
Severe dry eye sjorgren syndrome Exposure keratitis Filamentary keratitis Persistent epithelial defects Neutrophic cornea
44
How to fit scleral lenses
According to fitting guide Based on sagital height of lens and eye Lenses have to be inserted full in saline solution (without preservatives) and fluorescein to assess the fit
45
What are hybrid CLs
Central RGP material for good vision Peripheral soft material (siHy or Hy) for good comfort Useful for KC, PMD, post-LASIK, corneal transplant Special lens care solutions suitable for soft and RGP lenses needed Careful when cleaning (risk of seperation between both zones)
46
How to fit hybrid CLs
According to CL guide Based on saggital height of the eye and lens Lenses have to be inserted full of saline solution (without preservatives) and high weigh fluorescein to assess the fit
47
What are piggy back CLs
Consist of a soft lens underneath a corneal RGP to act as a cushion to a well fitting RGP DD siHy used The power of the soft Cls can be altered to help in the RGP fitting Use of 2 cls= more cost and reduce O2 permeability.
48
Uses of therapeutic/ bandage cls (6)
Promote epithelial/ corneal healing Wound coverage Pain relief Mechanical protection of the ocular surface Maintaining corneal hydration Drug delivery SiHy are the most common used
49
What is Billous kertopathy and how do therapeutic cls help
Chronic corneal edema caused by endothelial dysfunction Continues soft CL wear to reduce the pain
50
How do therapeutic cls help recurrent corneal erosions
Due to trauma or epithelial basement membrane dystrophy Cls promote healing and re-epithelialisation Cls should be worn in CW Soft lenses most used
51
How do therapeutic cls help in post -refractive surgery (PRK/ LASIK)
Reduces symptoms
52
How do therapeutic cls help severe dry eye
SiHy improve discomfort and blurred vision Modern scleral and mini scleral retainer fluid reservoir which facilitates both hydration and protection of cornea
53
How do therapeutic cls help trichiasis
Soft CL reduce symptoms and damage before ocular surgery
54
How do therapeutic cls help and what causes corneal thinning/ perforations
Common cause of perforation: accidental injury and surgical trauma Lens can prevent the extrusion of the ocular content before surgery Common cause of corneal thinning: RA results in keratolysis that destroys corneal stroma Lens prevent perforation by reinforcing cornea and preventing distension by the IOP (prevents swelling from increasing pressure)
55
What is the materials and Fitting of bandage lenses
Materials- biomimetic (better for tear film production issues), exposure keratitis high water content hydrogel (better for painful eye needing several weeks of cw like bullous keratopathy) SiHy (wound healing) like persistent epithelial defect rigid (severe dry eye and corneal exposure/ trichiasis) - large corneal; limbal diameter TD 12.50 and scleral Fitting: Plano, BOZR and TD are flatter with higher water content hydrogels, CW with lenses replaces every 4-8 weeks

Contact Lenses (4 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2025 Bold Learning Solutions. Terms and Conditions