4.2 CL IV - Soft CLs Flashcards
Soft CLs are the ..., with ...% new fittings and ...% re-fittings. This increasing popularity is propsed to be due to ..., ..., ..., ..., ....
Soft CLs are the most popular modality, with 97% new fittings and 91% re-fittings. This increasing popularity is propsed to be due to comfort, improved designs, public awareness, increased availability, silicon hydrogel materials.
What are the benefits of SCLs over RGP/ Glasses? (10 points)
- Initial comfort and short adaptation period
- Flexible CLs wear (varying modalities)
- Relative ease of fit
- Induce minimal corneal distortion
- Excellent on-eye stability
- Optical benefits → large optic zone = minimal glare; reduced aniseikonia compared with spectacles ∴ improved tolerance of anisometripic Rx
- Ease of replacement
- Low cost per lens relatively
- Ideal for active lifestyle
- Low risk of FB entrapment
What are th limitations of SCLs?
- Limited application for higher degree of astigmatism
- May not suit irregular corneas e.g. Keratoconus, ocular trauma, because soft CLs conforms to corneal shape
- Diffculty with verification of parameters
- Relatively higher incidence of cornel inflammatory and infective events compared with RGP
- Limited durability
- Prone to deposition (protein, mineral, lipid) and drying
Conventional soft lenses are ... with ... (usually ...months). All soft CLs should be replaced at least .... Due to being ..., they are available in wide ranges of ..., ... and ... designs in materials of ... water content. Lens cost is overall ... than disposable SCLs, excluding the cost of .... Conventional SCLs requires more ... and .... There are higher overall rate of ... compared to disposable lenses, possibly due to lower .... Thy are also ... due to being .... These disadvantages have contributed to the ... of this lens modality over the past ... years (<...% CL wearers).
Conventional soft lenses are custom made CLs with replacement intervals over 6 months (usually 6-12 months). All soft CLs should be replaced at least annually. Due to being custom fitted, they are available in wide ranges of spherical, toric and MF designs in materials of low, medium or high water content. Lens cost is overall lower than disposable SCLs, excluding the cost of care systems. Conventional SCLs requires more rigorous maintenance systems and enzyme protein removal solutions. There are higher overall rate of adverse reactions compared to disposable lenses, possibly due to lower oxygen permeability. Thy are also less convenient due to being custom made. These disadvantages have contributed to the decrease in use of this lens modality over the past 10 years (<1% CL wearers).
Why is regular lens replacement important? (4 points)
- Minimise effects of lens deterioration and deposition → minimise CL-related complications
- Assist with compliance
- Regular checks of ocular health
- Detect changes in refraction or vision
What are the available modality, lens deisgn and material for disposable SCLs?
- Modality: daily, fortnightly, monthly
- Lens designs: SV (spherical, toric), MF, myopia control
- Materials: hydrogel, silicon hydrogel
What are the advantages of disposable SCLs?
- Inventory maintained in practice ∴ easy trialling
- Wide range of parameters
- Improved ocular health ∵thinner lens profile & reduced deposits → reduced GPC
- Px convenience: simpler care system
- Ideal for part-time wearers
- Specialty lenses only slight price premium compared with spheres
- Numerous features available: handling tint, UV blocker, inversion indicator
- Enhanced compliance as px need to come in once they expire
How safe are daily disposable CLs?
DD wearers have the lowest incidence of non-severe keratitis of all types of SCLs. However, studies have not found a lower risk of microbial keratitis compared to other types of SCLs. It is associate with the lowest risk of severe microbial keratitis.
What are the potential disadvantages of daily disposables?
- Cost is the highest of any lens type for full type (unless wears 3 days a week, then it is cost competitive with 2/4 weekly lenses)
- More limited parameters than 2/4 weekly disposables
- More limited choice for astigmatic correction, presbyopic correction and coloured lenses
- Often only one base curve ∴ not good for steep or v flat corneal curvatures
- Limited availability of SiHy materials
Rates of compliance is found to be the highest with ... > ... > ....
The common reasons why px are non-compliant with recommended replacement schedules are ... and .... Studies have found no difference in frequency of ... or ... between ... and ... modalities.
Rates of compliance is found to be the highest with daily disposables > Monthly > Fortnightly.
The common reasons why px are non-compliant with recommended replacement schedules are forgetting which day to replace lenses and save money or running out of lenses. Studies have found no difference in frequency of CL-related dry eye or corneal staining between fortnightly and monthly modalities.
It is important that optometrists reinforces ... at every visit. Optom should use ... to identify ... patients. Optoms should encourage compliance by explaining the ..., ... and ... of ... as recommended, and the ... of over-wear. It may be useful to track ... to identify px using fewer lenses than expected. ... may aid in compliance, may suggest the ... or ... of the month as replacement aids for fortnightly or using .... Patients should always have ..., just in case they run out of CLs or cannot wear them for any reason.
It is important that optometrists reinforces compliance advice at every visit. Optom should use open questions to identify non-compliant patients. Optoms should encourage compliance by explaining the comfort, vision and ocular health benefits of replacing the CLs as recommended, and the potential consequences of over-wear. It may be useful to track order patterns to identify px using fewer lenses than expected. Direct shipments may aid in compliance, may suggest the 1st or 15th of the month as replacement aids for fortnightly or using electronic reminded systems. Patients should always have backup glasses, just in case they run out of CLs or cannot wear them for any reason.
- Handling tints of SCLs are usually a
...% density, which does not haveany ... effect on .... It is a standard on.... Handling tint is recommended for... or ... px who have ...;...can modify apparent iris colour for... eyes. They are usually tintedover a ... that is equal to the ... e.g. ...mm. Colours are additive to the... colour, therefore may not beapparent on ...; - Opaque tints can
.... There are designs with...to allow natural iris colour to be seen and to prevent"..." look of a ... tint. This lens tend to reduce...by less than...dB. There is also slightly reduced comfort due to... where the ... is located.
Handling tints of SCLs are usually a 10% density, which does not have any cosmetic effect on eye colour. It is a standard on many disposable CLs. Handling tint is recommended for hypermetropic or presbyopic px who have near focussing difficulties; Enhancement tints can modify apparent iris colour for lightly coloured eyes. They are usually tinted over a diameter that is equal to the HVID e.g. 11-11.5mm. Colours are additive to the iris colour, therefore may not be apparent on darker irises; Opaque tints can change iris colour. There are designs with opaque dots to allow natural iris colour to be seen and to prevent "bulbous" look of a fully opaque tint. This lens tend to reduce visual field sensitivity by less than 1dB. There is also slightly reduced comfort due to surface irregularity where the colourant is located.
UV blocking lenses absorbs an average of ...% of UV. However, only the... is protected, therefore these lenses are not .... These are useful for ...; reduce risk of reactivation of ..., and therefore reduce risk for .... UV blocking properties are ... e.g. ... (J&J), ... (Alcon).
UV blocking lenses absorbs an average of 90% of UV. However, only thecornea is protected, therefore these lenses are not a replacement for sunglasses. These are useful for patients working outdoors; reduce risk of reactivation of herpes simplex virus, and therefore reduce risk fo herpes simplex keratitis. UV blocking properties are standard in some disposable lenses e.g. Acuvue (J&J), Air Optix (Alcon).
