This ppt will explain in detail regarding the disinfection system including hydrogen peroxide system and other methods of care and maintenance of soft contact lens
Contact lens care and maintenance
RGP care
Soft Contact lens care
Silicon Hydrogel Care
Contact Lens Disinfection
Thermal disinfection
Chemical Disinfection
Oxidative chemical disinfection
Contact lens care and maintenance
RGP care
Soft Contact lens care
Silicon Hydrogel Care
Contact Lens Disinfection
Thermal disinfection
Chemical Disinfection
Oxidative chemical disinfection
Why should you use Bottle Top Dispensers ?Microlit India
Bottle Top Dispensers can facilitate a broad range of applications and increase safety,speed and reliability of daily lab work.
Choosing a bottle top dispenser saves time,work and protects you and your samples.
This presentation by Microlit will help you to understand the need for using Bottle Top Dispensers.
Different types of dosage forms have different properties so according to their handling and storage conditions we have to select containers accordingly
opthalmic preparations, Classification,factors affecting for the drug given t...krishna keerthi
ophthalmic preparations are medications designed for ocular use, typically in the form of eye drops or ointments. these formulations aim to treat various eye conditions . requirements of the ophthalmic preparations includes sterility, buffers, tonicity etc. proper application is crucial for effectiveness, ensuring the medication reaches the eye surface while minimizing systemic absorption. packaging of ophthalmic preparations . labeling the ophthalmic pharmaceutical products. storage conditions.
Care and maintenance of soft contact lensesAmrit Pokharel
The presentation I have made and uploaded provides you with an in-depth insight into the care and maintenance aspects of soft contact lens wear and use.
The author does not assume responsibility or legal liability for any errors in the text or for the misuse or misapplication of material in this work.
No copyright infringement, or plagiarism intended.
Amrit Pokharel
This is about the large extraction, hope you all get benefit from this and feel easy to use it .
This is all about how we do extraction at large scale and what is the best procedure to do it properly, as a pharmacist we must know about little details of our formulations how they are extracted and their further process and machinery used. All the terms should be considered and handling is the most important step. This will be a ready to explain type information.
WASHING, DRYING AND STERILIZATION OF GLASSWARES.pptxAVINASH K
Good laboratory technique demands clean glassware, because the most carefully executed piece of work may give an erroneous result if dirty glassware is used.
In all instances, glassware must be physically clean; it must be chemically clean; and in many cases, it must be bacteriologic ally clean or sterile.
All glassware must be absolutely grease-free.
This ppt will explain about how to write a grant proposal, the steps and what to lookout for. It provides help for those who are implementing a grant proposal
Why should you use Bottle Top Dispensers ?Microlit India
Bottle Top Dispensers can facilitate a broad range of applications and increase safety,speed and reliability of daily lab work.
Choosing a bottle top dispenser saves time,work and protects you and your samples.
This presentation by Microlit will help you to understand the need for using Bottle Top Dispensers.
Different types of dosage forms have different properties so according to their handling and storage conditions we have to select containers accordingly
opthalmic preparations, Classification,factors affecting for the drug given t...krishna keerthi
ophthalmic preparations are medications designed for ocular use, typically in the form of eye drops or ointments. these formulations aim to treat various eye conditions . requirements of the ophthalmic preparations includes sterility, buffers, tonicity etc. proper application is crucial for effectiveness, ensuring the medication reaches the eye surface while minimizing systemic absorption. packaging of ophthalmic preparations . labeling the ophthalmic pharmaceutical products. storage conditions.
Care and maintenance of soft contact lensesAmrit Pokharel
The presentation I have made and uploaded provides you with an in-depth insight into the care and maintenance aspects of soft contact lens wear and use.
The author does not assume responsibility or legal liability for any errors in the text or for the misuse or misapplication of material in this work.
No copyright infringement, or plagiarism intended.
Amrit Pokharel
This is about the large extraction, hope you all get benefit from this and feel easy to use it .
This is all about how we do extraction at large scale and what is the best procedure to do it properly, as a pharmacist we must know about little details of our formulations how they are extracted and their further process and machinery used. All the terms should be considered and handling is the most important step. This will be a ready to explain type information.
WASHING, DRYING AND STERILIZATION OF GLASSWARES.pptxAVINASH K
Good laboratory technique demands clean glassware, because the most carefully executed piece of work may give an erroneous result if dirty glassware is used.
In all instances, glassware must be physically clean; it must be chemically clean; and in many cases, it must be bacteriologic ally clean or sterile.
All glassware must be absolutely grease-free.
This ppt will explain about how to write a grant proposal, the steps and what to lookout for. It provides help for those who are implementing a grant proposal
VITREOUS AND RETINA PEDIATRIC OCULAR DIESEASES.pptxreshmasu
This ppt explains about the various pediatric ocular diseases of retina and vitreous:
1.Retinoblastoma
2.Persistent hyperplastic primary vitreous (PHPV)
3.Best disease
4.Coats disease
5.Retinopathy of prematurity
6.Stargardts disease
7.Juvenile retinoschisis
8.Familial exudative vitreoretinopathy
Introduction:
RNA interference (RNAi) or Post-Transcriptional Gene Silencing (PTGS) is an important biological process for modulating eukaryotic gene expression.
It is highly conserved process of posttranscriptional gene silencing by which double stranded RNA (dsRNA) causes sequence-specific degradation of mRNA sequences.
dsRNA-induced gene silencing (RNAi) is reported in a wide range of eukaryotes ranging from worms, insects, mammals and plants.
This process mediates resistance to both endogenous parasitic and exogenous pathogenic nucleic acids, and regulates the expression of protein-coding genes.
What are small ncRNAs?
micro RNA (miRNA)
short interfering RNA (siRNA)
Properties of small non-coding RNA:
Involved in silencing mRNA transcripts.
Called “small” because they are usually only about 21-24 nucleotides long.
Synthesized by first cutting up longer precursor sequences (like the 61nt one that Lee discovered).
Silence an mRNA by base pairing with some sequence on the mRNA.
Discovery of siRNA?
The first small RNA:
In 1993 Rosalind Lee (Victor Ambros lab) was studying a non- coding gene in C. elegans, lin-4, that was involved in silencing of another gene, lin-14, at the appropriate time in the
development of the worm C. elegans.
Two small transcripts of lin-4 (22nt and 61nt) were found to be complementary to a sequence in the 3' UTR of lin-14.
Because lin-4 encoded no protein, she deduced that it must be these transcripts that are causing the silencing by RNA-RNA interactions.
Types of RNAi ( non coding RNA)
MiRNA
Length (23-25 nt)
Trans acting
Binds with target MRNA in mismatch
Translation inhibition
Si RNA
Length 21 nt.
Cis acting
Bind with target Mrna in perfect complementary sequence
Piwi-RNA
Length ; 25 to 36 nt.
Expressed in Germ Cells
Regulates trnasposomes activity
MECHANISM OF RNAI:
First the double-stranded RNA teams up with a protein complex named Dicer, which cuts the long RNA into short pieces.
Then another protein complex called RISC (RNA-induced silencing complex) discards one of the two RNA strands.
The RISC-docked, single-stranded RNA then pairs with the homologous mRNA and destroys it.
THE RISC COMPLEX:
RISC is large(>500kD) RNA multi- protein Binding complex which triggers MRNA degradation in response to MRNA
Unwinding of double stranded Si RNA by ATP independent Helicase
Active component of RISC is Ago proteins( ENDONUCLEASE) which cleave target MRNA.
DICER: endonuclease (RNase Family III)
Argonaute: Central Component of the RNA-Induced Silencing Complex (RISC)
One strand of the dsRNA produced by Dicer is retained in the RISC complex in association with Argonaute
ARGONAUTE PROTEIN :
1.PAZ(PIWI/Argonaute/ Zwille)- Recognition of target MRNA
2.PIWI (p-element induced wimpy Testis)- breaks Phosphodiester bond of mRNA.)RNAse H activity.
MiRNA:
The Double-stranded RNAs are naturally produced in eukaryotic cells during development, and they have a key role in regulating gene expression .
Earliest Galaxies in the JADES Origins Field: Luminosity Function and Cosmic ...Sérgio Sacani
We characterize the earliest galaxy population in the JADES Origins Field (JOF), the deepest
imaging field observed with JWST. We make use of the ancillary Hubble optical images (5 filters
spanning 0.4−0.9µm) and novel JWST images with 14 filters spanning 0.8−5µm, including 7 mediumband filters, and reaching total exposure times of up to 46 hours per filter. We combine all our data
at > 2.3µm to construct an ultradeep image, reaching as deep as ≈ 31.4 AB mag in the stack and
30.3-31.0 AB mag (5σ, r = 0.1” circular aperture) in individual filters. We measure photometric
redshifts and use robust selection criteria to identify a sample of eight galaxy candidates at redshifts
z = 11.5 − 15. These objects show compact half-light radii of R1/2 ∼ 50 − 200pc, stellar masses of
M⋆ ∼ 107−108M⊙, and star-formation rates of SFR ∼ 0.1−1 M⊙ yr−1
. Our search finds no candidates
at 15 < z < 20, placing upper limits at these redshifts. We develop a forward modeling approach to
infer the properties of the evolving luminosity function without binning in redshift or luminosity that
marginalizes over the photometric redshift uncertainty of our candidate galaxies and incorporates the
impact of non-detections. We find a z = 12 luminosity function in good agreement with prior results,
and that the luminosity function normalization and UV luminosity density decline by a factor of ∼ 2.5
from z = 12 to z = 14. We discuss the possible implications of our results in the context of theoretical
models for evolution of the dark matter halo mass function.
Observation of Io’s Resurfacing via Plume Deposition Using Ground-based Adapt...Sérgio Sacani
Since volcanic activity was first discovered on Io from Voyager images in 1979, changes
on Io’s surface have been monitored from both spacecraft and ground-based telescopes.
Here, we present the highest spatial resolution images of Io ever obtained from a groundbased telescope. These images, acquired by the SHARK-VIS instrument on the Large
Binocular Telescope, show evidence of a major resurfacing event on Io’s trailing hemisphere. When compared to the most recent spacecraft images, the SHARK-VIS images
show that a plume deposit from a powerful eruption at Pillan Patera has covered part
of the long-lived Pele plume deposit. Although this type of resurfacing event may be common on Io, few have been detected due to the rarity of spacecraft visits and the previously low spatial resolution available from Earth-based telescopes. The SHARK-VIS instrument ushers in a new era of high resolution imaging of Io’s surface using adaptive
optics at visible wavelengths.
Seminar of U.V. Spectroscopy by SAMIR PANDASAMIR PANDA
Spectroscopy is a branch of science dealing the study of interaction of electromagnetic radiation with matter.
Ultraviolet-visible spectroscopy refers to absorption spectroscopy or reflect spectroscopy in the UV-VIS spectral region.
Ultraviolet-visible spectroscopy is an analytical method that can measure the amount of light received by the analyte.
THE IMPORTANCE OF MARTIAN ATMOSPHERE SAMPLE RETURN.Sérgio Sacani
The return of a sample of near-surface atmosphere from Mars would facilitate answers to several first-order science questions surrounding the formation and evolution of the planet. One of the important aspects of terrestrial planet formation in general is the role that primary atmospheres played in influencing the chemistry and structure of the planets and their antecedents. Studies of the martian atmosphere can be used to investigate the role of a primary atmosphere in its history. Atmosphere samples would also inform our understanding of the near-surface chemistry of the planet, and ultimately the prospects for life. High-precision isotopic analyses of constituent gases are needed to address these questions, requiring that the analyses are made on returned samples rather than in situ.
A brief information about the SCOP protein database used in bioinformatics.
The Structural Classification of Proteins (SCOP) database is a comprehensive and authoritative resource for the structural and evolutionary relationships of proteins. It provides a detailed and curated classification of protein structures, grouping them into families, superfamilies, and folds based on their structural and sequence similarities.
Cancer cell metabolism: special Reference to Lactate PathwayAADYARAJPANDEY1
Normal Cell Metabolism:
Cellular respiration describes the series of steps that cells use to break down sugar and other chemicals to get the energy we need to function.
Energy is stored in the bonds of glucose and when glucose is broken down, much of that energy is released.
Cell utilize energy in the form of ATP.
The first step of respiration is called glycolysis. In a series of steps, glycolysis breaks glucose into two smaller molecules - a chemical called pyruvate. A small amount of ATP is formed during this process.
Most healthy cells continue the breakdown in a second process, called the Kreb's cycle. The Kreb's cycle allows cells to “burn” the pyruvates made in glycolysis to get more ATP.
The last step in the breakdown of glucose is called oxidative phosphorylation (Ox-Phos).
It takes place in specialized cell structures called mitochondria. This process produces a large amount of ATP. Importantly, cells need oxygen to complete oxidative phosphorylation.
If a cell completes only glycolysis, only 2 molecules of ATP are made per glucose. However, if the cell completes the entire respiration process (glycolysis - Kreb's - oxidative phosphorylation), about 36 molecules of ATP are created, giving it much more energy to use.
IN CANCER CELL:
Unlike healthy cells that "burn" the entire molecule of sugar to capture a large amount of energy as ATP, cancer cells are wasteful.
Cancer cells only partially break down sugar molecules. They overuse the first step of respiration, glycolysis. They frequently do not complete the second step, oxidative phosphorylation.
This results in only 2 molecules of ATP per each glucose molecule instead of the 36 or so ATPs healthy cells gain. As a result, cancer cells need to use a lot more sugar molecules to get enough energy to survive.
Unlike healthy cells that "burn" the entire molecule of sugar to capture a large amount of energy as ATP, cancer cells are wasteful.
Cancer cells only partially break down sugar molecules. They overuse the first step of respiration, glycolysis. They frequently do not complete the second step, oxidative phosphorylation.
This results in only 2 molecules of ATP per each glucose molecule instead of the 36 or so ATPs healthy cells gain. As a result, cancer cells need to use a lot more sugar molecules to get enough energy to survive.
introduction to WARBERG PHENOMENA:
WARBURG EFFECT Usually, cancer cells are highly glycolytic (glucose addiction) and take up more glucose than do normal cells from outside.
Otto Heinrich Warburg (; 8 October 1883 – 1 August 1970) In 1931 was awarded the Nobel Prize in Physiology for his "discovery of the nature and mode of action of the respiratory enzyme.
WARNBURG EFFECT : cancer cells under aerobic (well-oxygenated) conditions to metabolize glucose to lactate (aerobic glycolysis) is known as the Warburg effect. Warburg made the observation that tumor slices consume glucose and secrete lactate at a higher rate than normal tissues.
Comparing Evolved Extractive Text Summary Scores of Bidirectional Encoder Rep...University of Maribor
Slides from:
11th International Conference on Electrical, Electronics and Computer Engineering (IcETRAN), Niš, 3-6 June 2024
Track: Artificial Intelligence
https://www.etran.rs/2024/en/home-english/
2. HYDROGEN PEROXIDE
• Hydrogen peroxide, along with thermal disinfection, is one of the earliest SCL
disinfection methods.
• Produces free oxygen radicals which are very reactive and quickly bind to many
microbial cell components.
• Decomposes to water and oxygen
2H2O2 2H2O + O2
3. • Hydrogen peroxide is a non-selective antimicrobial agent normally used at 3%
concentration.
• When a second solution or step is required for neutralization, the system is called a 2-
step system.
• A 1-step system requires the combination of both the disinfection and neutralization
steps using either a catalytic disc, or a coated delayed-release catalytic neutralizing
tablet.
4. The lens is placed in the holder and kept in the
bottle with HCL solution and close the lid tightly
Leave the lens for at least 6hrs then the solution
starts to get neutralized which loosen protein,
remove debris and deep clean the lens
After which we can remove the lens clean it with
non preserved saline and insert.
The disc in the bottle acts as a catalyst.
Advantages Disadvantages
•Convenient
•Preservative-free
•Concurrent protein
removal now
possible
•Inflexible neutralization
time
• H2O2 concentration
decreases rapidly
(3% to 1% in <10mins)
• Not effective against
some fungi and
Acanthamoeba sp.
• Catalytic disc needs
regular replacement
• Potential for irritation
• Possible recontamination
ONE STEP PEROXIDE DISINFECTION
5.
6. TWO STEP PEROXIDE DISINFECTION
• Minimum 3 hours in 3% H2O2 recommended,
overnight preferred (6-9 hours)
• Bacteria 10-15 min
• Fungi 60 min
• Acanthamoeba sp. 3 - 6 hours
• Suitable for all lens types (including GP CLs)
Advantages Disadvantages
•Can vary time of
disinfection
•Concurrent protein
removal possible
•Suited to the occasional
wearer
•Less convenient
•Some have preserved
neutralizing solution
•Potential for irritation
•Expensive
9. CARE REGIMEN GUIDELINES
• If preserved saline is used, the lenses can be stored in the preserved solution
• If unpreserved saline is used, the risks of contamination are much greater once the
bottle is opened and has been in use for a few days
One-Step Hydrogen Peroxide:
• Disinfection and neutralization period depends on brand
• Platinum disc neutralizes hydrogen peroxide solution into preserved saline
• Air vent allows release of gas
10. Two-Step Hydrogen Peroxide:
• Store lens in 3% peroxide when not in use
• Neutralize before wear
• Longer soaking times are required for lenses with higher water content
• A preservative-free neutralizer is ideal
11. UNCONVENTIONAL DISINFECTION
METHODS
1. ULTRASONIC
• Induces DNA cross-linking in micro-organisms or cells causing death
• Results not superior to conventional method
• Rub and rinse step still necessary
• Expensive
• A partial explanation of the poor efficacy of ultrasonic devices was presented by Fatt
(1991)
12. • Some ultrasonic devices could behave as
microbial incubators rather than
antimicrobial devices
• Some of their temperature settings warm
the solution (80°C)
• Aquasteril™ (from France). This ultrasonic
device also has an ozone-generating UV
source in the lid
13. 2. MICROWAVE
• High heat denaturation of biological lens contaminants
• Similar principle to heat/thermal disinfection
• Needs vented lens container
• Convenient and effective for large number of lenses simultaneously
• Effect of long-term repeated microwave irradiation on lens parameters unknown
14. IN-OFFICE TRIAL SET
DISINFECTION
• Inventory trial lenses should be disinfected at least
once per month
• Thermal disinfection is safest
• If using chemical disinfection, vials and lenses
should be cleaned periodically and solution
changed regularly
15. RECOMMENDATION
• Use thermal disinfection for low water content
• Clean lenses with alcohol-based cleaner prior to storage
• Use unneutralized peroxide on high water lenses
• If using chemical disinfection, vials & CLs should be cleaned periodically & solution
changed regularly (every 6 months)
• Use disposable lenses where possible
16. PROTEIN REMOVERS
• Effectively remove protein deposits
• Have no effect on most other deposits
• React by breaking proteins into smaller molecules
To remove a protein, it
must be hydrolyzed
For lysozyme, the four
S–S (disulphide) bonds
must be cleaved (broken)
to allow an ‘unraveling’ of
the protein chain
17. 2. GENERAL PROCEDURES
• Done regularly, after daily cleaning & rinsing steps
• Can be done BEFORE disinfection, or done DURING disinfection (with H2O2 systems,
compatible enzyme required)
BEFORE: Lenses soaked in MPS or saline with enzyme dissolved in solution – 15 min
to overnight
• CL’s should be rubbed and rinsed thoroughly in MPS or sterile saline after protein
treatment
• Protein removal must be followed by disinfection
18. DURING: Protein remover tablet placed in peroxide after case is filled but before the
CLs immersed or neutralizing tablet added
• Processing time is governed by the peroxide system’s disinfection recommendations
• Lenses should be rubbed & rinsed thoroughly with fresh sterile saline after protein
treatment immediately before lens insertion
19. ENZYMATIC PROTEIN
REMOVERS
• While most protein removers are based on enzymes, not all are enzymatic
• Enzymatic cleaners work by having substrate-specific enzymes (biochemical
catalysts) break down their target molecules, thereby facilitating their removal
• The enzymes work by breaking down their targets into smaller molecules
• Enzymes can also remove other types of deposits if they are incorporated in the
protein deposits
20. • Enzymes may also break bonds between
the lens material and proteins
• Enzymatic cleaning does not replace the
disinfection step
21. 1. PAPAIN
• Protease
• Derived from papaya plant
• Binds to contact lens materials and can cause
sensitivity reactions
• Short 15 minute soaking time possible
• Examples: Allergan’s Soflens Enzymatic Cleaner or
Profree
22. 2. PANCREATIN
• Protease (protein), lipase (lipid) and amylase
(polysaccharides)
• Pig pancreas derivative
• Cleaning efficacy similar to papain
• Examples: Alcon Optizyme, Polyzym, Opti-Free
Enzymatic Cleaner
23. 3. SUBTILISIN A and B
• Proteases
• Derived from Bacillus bacteria
• Low toxicity, used in food products
• Less specific binding characteristics
• May be more effective than papain
• Examples: B&L Sensitive Eyes Thermal Protein
Removal Tablets, Sensitive Eyes Protein Removal
Tablets (Subtilisin B), Allergan Ultrazyme (Subtilisin A),
PBH Softmate Enzyme Plus
24. RE-WETTING/LUBRICATING
DROPS
• Alleviating symptoms of dryness/ discomfort
• Flushing irritating particles from eye and lens
• Rehydrating lenses
• Caution the patient not to touch the dispensing nozzle (jet) to the lids, lashes or
external eye
Useful for:
• Marginal dry eye patients
• A dry environment or windy conditions
• Tired eyes
• Alleviating allergy symptoms
25. DEMULCENTS
• Relatively new class of solution component in some newer LCPs
• Usually, demulcent is a water-soluble polymer applied to the eye topically to:
◦ protect & lubricate mucous membranes (e.g. conjunctiva)
◦ dryness symptoms & irritation
• Demulcents help to comfort by modifying CL surfaces
• HydroxyPropylMethylCellulose (HPMC) used in dry eye products, tablet coatings, drug
release systems (& 1-Step peroxide neutralizing tablets), & to solution viscosity
• HPMC effective in controlling symptoms & signs of dry eye
26. Dexpanthenol (Dexpant-5)
• Used to lens wetting & lubricity
• Used in some dry eye products
Sorbitol
• Enhances CL wettability
• Also used to adjust solution osmolality
27. • Rub & rinse important because:
◦ SiHy CLs deposit lipid and/or other tear components on & in lens matrix. This
deposition can only be removed effectively by rubbing
◦ frequently, wearers report comfort if they rub their CLs
◦ rubbing & rinsing alone removes >90% of micro-organisms from a lens
28. FOR OCCASIONAL & INFREQUENT
WEARERS
Storage:
• Lenses should be stored in disinfecting solution when not in use Storage
• For regular wearers this will involve overnight storage (approximately 8 - 10 hours),
and for occasional wearers storage for days (>24 hours)
• Stronger solutions increase adsorption by the lens material.
• Solutions containing weak preservatives increase the risk of lens contamination during
long-term (>7 days) storage
• Multi-purpose solutions and 1-step peroxide systems are unsuitable to long-term
contact lens storage
29. • Clean and disinfect lenses again prior to use
• Replace the storage solution at least every week when lenses not worn
• Use preserved saline for rinsing (sensitivity problem is unlikely if only used for rinsing)
• Surfactant cleaner is a must
• Select appropriate disinfection system
• Protein removal when needed
30. CARE FOR LENS CASE
• Scrub weekly with a new, clean toothbrush (hard/firm rather than soft) & CL
CLEANING solution
• Rinse with sterile saline or MPS & shake excess solution from case
• Rub dry with clean tissue
• Air dry case & lids upside-down on clean tissue
• Replace regularly (at least 3 monthly)
Recently, antibacterial lens cases have been marketed
• Case polymer is impregnated with silver ions (Ag+) that reduce bacterial
contamination & biofilm formation
Formulated so that the peroxide disinfection and neutralization are performed during the recommended time
With tablet using system a delay is applied to the neutralization phase. With disc-based systems, no delay is applied to the neutralization phase
When neutralization is performed as separate step, the system is called a two step neutralization.
PRESERVATIVES ARE SUBSTANCES THAT PREVENT CONTAMINATION BY MICRO-ORGANISMS INCLUDING BACTERIA. 15 DAYS DISCARD. UNBUFFERED SALINES (NP) HAS PURIFIED WATER AND SODIUM CHLORIDE. BUFFERED SALINES HAVE FOUR INGREDIENTS: PURIFIED WATER, SODIUM CHLORIDE PLUS TWO INGREDIENTS FOR BUFFERING PURPOSES: SODIUM BORATE AND BORIC ACID
DISADV
No control over disinfection phase
[H2O2] rapidly (3 to 1% <10 min)
Ineffective against some fungi & encysted Acanthamoeba sp.
Catalytic disc needs regular replacement
paradoxically, infrequent change disinfection efficacy
Potential for irritation
tablet system: tablet components
disc system: catalyst ‘poisoning’ residual peroxide
Possible re-contamination (unpreserved resulting solution)
Neutralizers are: sodium pyruvate, sodium sulphite, sodium thiosulphate.
Sodium pyruvate with H2O2 produce sodium acetate water and carbon dioxide.
NaC3H3O3 + H2O2 ⇒ NaC2H3O2 + H2O +CO2
Sodium sulphite and peroxide produce sodium sulphate and water.
Na2SO3 + H2O2 ⇒ Na2SO4 + H2O
ADV
Can vary disinfection time
unlimited possibilities, min. recommended 1 hour
Concurrent protein removal possible
peroxide-compatible product required
Better suited to the occasional wearer
lenses can be stored in unneutralized peroxide
3-monthly solution replacement recommended
Few options now available
DISADV
Less convenient
effort required to commence neutralization
more component ‘parts’ (bottles)
If preserved neutralizing solution used
potential for irritation
shorter Expiry: & Discard-After: dates (than peroxide)
Can be more expensive
Perception that too much packaging used
EFFECT ON LENS
May cause reversible lens parameter changes in higher water content CLs
Changes take a little time to reverse (equilibrate) once peroxide concentration is reduced or neutralizing solution is introduced
the higher the water content, the longer it takes to reverse induced parameter changes
Caution required
Unneutralized or incompletely neutralized peroxide in CLs will result in discomfort/pain/ocular irritation on insertion (see next slide for thresholds)
anterior eye has 3 peroxidative enzyme ‘systems’ for dealing with hydrogen peroxide exposure
glutathione peroxidase (LOCATED IN corneal epithelium [CAN DEAL WITH medium concentrations])
superoxide dismutase (corneal epithelium [medium concentrations])
catalase:
(conjunctival epithelium [heavy concentrations])
(corneal epithelium [medium concentrations])
While occasional and infrequent wearers are able to disinfect their lenses for the maximum period recommended, one-step systems present potential problems in some situations.
One-step peroxide systems neutralize their solutions using either a platinum disc or delayed release catalase tablet, a process requiring up to six hours. Their breakdown product is basically unpreserved saline (the liberated oxygen is ventilated). Unpreserved saline is a solution entirely unsuited to long-term lens storage.
A possible solution is to have a discless cup (for disc-based systems) or to withhold the delayed release neutralizing tablet (tablet-based systems). In this way the lenses are stored in unneutralized hydrogen peroxide, a safe procedure. The disadvantage of such storage is the need for neutralization immediately prior to lens usage. This presupposes a knowledge of when the lenses are required.
It is also important to remind patients that vented storage cases are not ideal for lens carrying because of their potential for leakage and contamination, especially if they topple over.
Two-step hydrogen peroxide systems provide a better long-term storage alternative since the lenses can be stored in a 3% hydrogen peroxide solution between lens uses.
Neutralization is performed prior to lens wear. Longer soaking times are required for lenses with higher water content. A preservative-free neutralizer is ideal.
It is important to realize that neutralization is not just a process involving the solution in which the lens is stored. For neutralization to be complete, the peroxide content of the lens must also be converted to compatible by-products. This takes longer because of diffusion into, and out of, the lens.
The fact that the physical properties of a hydrogel lens and saline are ‘so closely alike’ means that little energy is released at the lens/saline interface. Therefore, it seems unlikely that current soft lens materials can be ‘cleaned’ ultrasonically
Some of their temperature settings warm the solution (80°C), not sufficiently to kill micro-organisms but potentially increasing population growth rates
Another uncommon device is the Aquasteril™ (from France). This ultrasonic device also has an ozone-generating UV source in the lid. Unfortunately, no attempt has been made to seal the hinged lid to the lens wells. This leaves them open to contamination after the disinfection cycle is complete.
Needs vented lens container. If ‘explosion’ is to be prevented
The use of convenient one-bottle systems for trial lens storage is not supported by the data of a study (Callender et al., 1992) which showed the highest level of contamination occurred when such sytems were employed.
Heat, especially when used in conjunction with a preserved saline, was clearly superior to all other methods examined.
Thermal disinfection is neither recommended, nor possible, with many high water content lenses.
Storage, including long-term storage, of such lenses is possible in unneutralized hydrogen peroxide (preferably in a peroxide which is isotonic and of normal pH). However, trials with these lenses necessitate timely neutralization before use. The peroxide solution should be changed at least every six months and the case lids must be secured firmly. No metal should be in contact with lenses so stored as it may decompose the peroxide catalytically, leading to case rupture caused by excess pressure generated by liberated oxygen
While most protein removers are based on enzymes, not all are enzymatic. Some are based on inorganic chemicals while others may be organic but not enzymatic.
Enzymatic cleaners work by having substratespecific enzymes (biochemical cataysts) break down their target molecules, thereby facilitating their removal. For example proteases target proteins, lipases target lipids while amylases target polysaccharides.
The enzymes work by breaking down their targets into smaller molecules. They cleave peptide bonds within the protein molecules, creating lower molecular weight, more soluble molecules which are more easily removed.
Hydrogen peroxide is believed to be capable of breaking disulphide bonds in the protein lysozyme. Therefore, it was postulated that a combination of hydrogen peroxide and a proteolytic enzyme is potentially an effective protein ‘treatment’.
Soft CL protein removers usually contain one of the following:
Papain
Pancreatin
Subtilisin A or Subtilisin B
• Is a protease, i.e. an enzyme that acts on proteins specifically.
• Is derived from the pawpaw/papaya plant (Carica papaya).
• Preparations containing it usually have a slightly unpleasant odour due to the inclusion of cysteine (used as an enzyme stabilizer).
• Binds to soft contact lens materials and may cause sensitivity reactions. In an attempt to decrease the frequency of sensitivity reactions soaking time was reduced from two hours to just 15 minutes. Examples: Allergan’s Soflens Enzymatic Cleaner or Profree
• Has three separate enzyme activities: Protease (protein), lipase (lipid) and amylase (polysaccharides and mucus-like (glycoproteins) debris).
• Derived from the pancreas of the pig.
• Unfortunately, the lipase and amylase enzymes do not seem to improve the performance of products containing pancreatin. The performance of such products is similar to papain or subtilisin containing products (Begley et al., 1990) or even inferior on all but light deposits (Kurashige et al., 1987). Examples: Alcon Optizyme, Polyzym, Opti-Free Enzymatic Cleaner.
Dryness and discomfort can be caused by abnormalities of the tear film and lowered relative humidity. Relative humidity can be influenced by climate and air conditioning.
Any decrease in the lubricity of the tear film has the potential to decrease ocular comfort especially in contact lens wearers. Further, tear film abnormalities and/or abnormal amounts of tear film ‘drying’ on the lens surfaces have the potential to increase lens deposition. Additionally, lowering the level of lens hydration can adversely affect the Dk/t of contact lenses (Paugh, 1992).
In the interests of solution contamination control, and possible cross infection of the eyes, it is important to caution the patient not to touch the dispensing nozzle (jet) to the lids, lashes or external eye.
Re-wetting/lubricating drops should not be used prior to soft contact lens removal because they may make removal more difficult. Some are hypertonic which can tighten the lens fit and all contain surfactants which make the lens ‘slippery’. The latter effect can also be exaggerated by the use of viscosity-enhancing agents which are also common in such products
For regular wearers this will involve overnight storage (approximately 8 - 10 hours), and for occasional wearers storage for days (>24 hours).
Stronger solutions increase adsorption by the lens material. However, solutions containing weak preservatives increase the risk of lens contamination during long-term (>7 days) storage.
Multi-purpose solutions and 1-step peroxide systems are unsuitable to long-term contact lens storage. If a cold chemical system is used, the solution should be replaced weekly.
The frequency of protein removal should be based on the number of times the lenses are worn and the frequency of wear.
A factor in protein denaturation is the age of the protein involved. If lens wear is infrequent, it is probable that a recommendation to remove protein every five lens uses may be prudent.
Preserved or unpreserved saline can be used. If preserved saline is used, the lenses can be stored in the preserved solution.
However, if unpreserved saline is used, the risks of contamination are much greater once the bottle is opened and has been in use for a few days
