Carboxymethyl Cellulose versus Hydroxypropyl ...

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The baseline OSDI score? 23.48 and 23.32 in Group A and B, respectively, decreased with treatment in both groups on all follow-up visits as compared to the baseline (day 90: 13.9 ± 3 vs. 14.81 ± 3.17, P: 0.01). The scores of Schirmer I test increased in both groups, with a greater improvement in Group A (at day 90: 22.75 ± 3.04 mm vs. 21.78 ± 3.36 mm, P: 0.04). The values of TF-BUT improved in both groups, the difference being statistically insignificant. An initial stinging was reported by one participant, each in both groups.

This was a prospective, randomized, comparative, and open-labeled study. The efficacy of CMC 0.5% and HPMC 0.3% tear substitutes was compared in 180 participants (90 in each group) with dry eye. Change in Ocular Surface Disease Index (OSDI) score, Schirmer I test score, and tear film break up time (TF-BUT) were used as efficacy parameters. Safety was monitored on all visits.

In this study, we compared the efficacy and safety of two commonly used tear substitutes containing CMC 0.5% and HPMC 0.3% in participants diagnosed with dry eye due to CVS. This was the first time two commonly used tear substitutes were compared in CVS using both qualitative and quantitative tests of dry eye disease.

Carboxymethyl cellulose (CMC) is a cellulose polymer with a carboxylic group and has a high viscosity. It has bioadhesive properties, and its anionic nature may be the reason for high retention time on the cornea. Hydroxypropyl methylcellulose (HPMC), also known as hypromellose, is a semisynthetic polymer. It is less viscous than CMC due to its molecular size but is known to have emollient properties.[ 8 ]

A key principle for the management of dry eye disease is an augmentation of tear film through the topical administration of artificial tear substitutes. These tear substitutes are the mainstay of treatment for mild-moderate dry eye symptoms. These products enhance tear stability and help to retain moisture in eye, thus relieving the symptoms of CVS.[ 7 ]

The Occupational Safety and Health Administration department of US Government has defined computer vision syndrome (CVS) as a &#;complex of eye and vision problems that are experienced during and related to computer use; it is a repetitive strain disorder that appears to be growing rapidly in workers using computers for more than 3 h/day.&#;[ 6 ]

The etiology of dry eye still remains unclear though some known risk factors are older age, female gender, arthritis, smoking, hormone-replacement therapy, and environmental factors such as low relative humidity.[ 4 ] Prolonged exposure to visual display terminals images on electronic devices such as computers and video games leads to reduced blink rate, which generate ocular discomfort and subsequently dry eye.[ 5 ]

As per the DEWS II global dry eye definition, &#;Dry eye is a multifactorial disease of the ocular surface characterized by a loss of homeostasis of the tear film and accompanied by ocular symptoms, in which tear film instability, hyperosmolarity, ocular surface inflammation, and damage along with neurosensory abnormalities play etiological roles.&#;[ 1 ] The prevalence of dry eye syndrome increases with age and ranges from 5.5% to 37.7%.[ 2 ] In the Indian population, hospital-based prevalence of dry eye has been reported to vary from 18% to 27%.[ 3 ]

Quantitative variables were compared using Mann&#;Whitney test (as the data sets were not normally distributed) between the two groups and Wilcoxon ranked sum test within the group across follow-up

Schirmer Test-I &#; This was performed by folding 5 mm at the top end of a special Whatman filter paper strip. It was placed in the lower conjunctival sac at the junction of the outer one-third and medial two-thirds of the lower eyelid. It was left in place for 5 min or until 30 mm of the strip becomes wet. The strip was removed from the eye and the wet portion measured. Schirmer test I (Schirmer test without anesthesia) measures basic plus reflex tear secretion. Although no absolute cutoff has been established for this test, <10 mm of strip wetting in 5 min is suggestive of an unhealthy tear film.[ 13 ] This was performed on day 0 and day 90.

Tear film break up time (TF-BUT) &#; The tear film stained with sodium fluorescein 1% was observed with a slit-lamp biomicroscope, and the time noted after instructing the patient to blink. The time taken for the first appearance of a dry spot was recorded as the &#;tear film break up time&#; or TF-BUT. A TF-BUT of <10 s was taken as dry eye.[ 13 ] This was evaluated at baseline, days 30, and 90.

This is the most frequently used survey instrument and is validated for the assessment of ocular surface disease severity in dry eye research. It consists of 12 questions that assess symptoms, functional limitations, and environmental factors related to dry eye. The maximum score is 100, which indicates complete disability and a score of zero indicates no disability.[ 12 ] Ocular Surface Disease Index (OSDI) questionnaire was administered to participants on all visits.

In addition to the tear substitute use, participants were advised to blink voluntarily more often during computer usage. Participants were advised to follow the &#;20-20-20 rule.&#; As per this rule, participants were advised to look away from the computer at least every 20 min and gaze for at least 20 s at an object at least 20 feet away: this causes relaxation of the ocular muscles of accommodation.

The participants first underwent a clinical workup including a detailed history and an ophthalmic examination. Those who fulfilled the inclusion criteria were enrolled in the study after obtaining a written informed consent. Participants were divided into two groups using computer-generated random numbers: group A received CMC 0.5% and Group B received HPMC 0.3% tear substitute for 90 days.

Participants with known hypersensitivity to the study medications and those who had used any other topical ophthalmic medications within 14 days (other than tear substitutes) were excluded from the study. Other criteria for exclusion were a history of active ocular infection or ocular allergy, ocular surgery within 12 months, recurrent herpetic keratitis, use of contact lenses, systemic medications (such as diuretics, antidepressants, anxiolytics, and antihypertensives), and any systemic diseases/syndromes associated with dry eye (Sjogren's syndrome and other autoimmune diseases).

Participants of both genders aged 18 years and above with an average computer use of &#;3 h at a stretch per day or &#;15 h a week for at least 3 months presenting with ocular symptoms (blurring of vision, headache, dry eyes, redness of eyes, or eye strain) were considered to have CVS.[ 11 ]

This was a prospective, randomized, comparative, and open labeled study, conducted by enrolling the patients, visiting the outpatient clinic of department of ophthalmology. The sample size was calculated as 180 (90 in each group) based on previous studies with an α = 0.05 and β = 0.2.[ 9 , 10 ] Patients diagnosed to have dry eye due to CVS and to satisfy the inclusion were enrolled in the study after getting the informed consent. The study procedures followed the Helsinki Declaration of , as revised in . The study was approved by the institutional ethics committee and research board.

Only one study participant, each from Group A and Group B had initial burning sensation when they used the respective tear substitutes for the first time. On subsequent usage, there was no discomfort reported, and therefore the participants continued with the prescribed medications. No other ADRs were reported.

The mean TF-BUT value for Group A and B was comparable at baseline: (10.56 s and 10.96 s, respectively; P = 0.393). TF-BUT values increased for both the groups on subsequent follow-up visits, which is indicative of an improvement in dry eye symptoms [ ]. There was no statistically significant difference between the groups on comparing the values on day 90 (P = 0.4).

The Schirmer I-test values were comparable between the two groups on day 0 (12.86 mm for Group A and 13.12 mm for Group B; P = 0.341). On day 90, the values on day 90 in both Groups A and B showed an increase compared to the baseline [ ]. The increase in value indicates an improvement in symptoms. Group A showed a statistically significant increase in values as compared to Group B [ ].

OSDI score, used as the primary efficacy parameter, was comparable in Group A and B at baseline: 23.38 and 23.32, respectively, with a P = 0.728. As compared to the baseline, there was an improvement in OSDI scores on all follow-up visits in both groups, and this difference was statistically significant. There was also a statistically significant difference between Groups A and B on all follow-up visits, as shown in .

In this study, out of a total of 180 participants, 50.6% of participants were in the age group of 21&#;30 years, while 30% of the participants were in the age group of 18&#;20 years [ ]. Overall, there was a slight female preponderance with 51.67% of the participants being female [ ].

Discussion

We evaluated the efficacy and safety of two commonly used tear substitutes, CMC and HPMC in participants in the age group of 18&#;60 years. The results of the study show that the tear substitutes are efficacious in reducing dryness of eyes as evident from the reduction of OSDI score and improvement in secondary parameters, namely, Schirmer test and TF-BUT. The safety of these drugs is also reflected in the study results.

In today's world, computers and laptops are used for different aspects of office work: accessing the Internet as well as for recreational purposes. Computer users mostly belong to the younger age group. In India, around 38% of internet users are in the age group of 25&#;34 years.[14] About 51% of participants who were diagnosed with CVS in our study are in the age group of 21&#;30 years. When combining the age groups 18&#;20 and 21&#;30 years, it comprised about 80% of study participants. Computer professionals are mainly from the younger generation, and they are more likely to be affected by computer-related problems such as CVS considering the need to spend long hours in front of visual display terminals.

The OSDI score reduced with treatment in both groups of study participants on all follow-up visits, starting from 15th day onward. This showed that both the tear substitutes were able to reduce the symptoms of dry eye due to CVS. These results are similar to other studies where an improvement in OSDI scores has been shown with the use of CMC and HPMC tear drops.[15,16] Both tear substitutes are efficacious in reducing symptoms as they moisturize the ocular surface and their high viscosity increases their retention time and persistence of beneficial effect to the patient. The improvement in OSDI score was greater for Group A (CMC) as compared to Group B (HPMC) tear substitutes; the results were statistically significant. The slightly greater improvement shown by the CMC group may be due to the higher mucoadhesive properties of CMC.[17,18]

Schirmer I-test values, assessed on day 0 and day 90, showed an improvement in both groups. Group A participants, who received CMC 0.5% tear substitutes, showed a higher improvement in comparison with Group B who received HPMC 0.3%. In a study comparing CMC with hyaluronate, a similar improvement in Schirmer test values was demonstrated by CMC and sodium hyaluronate study groups.[19] A study which compared CMC and HPMC drops in postoperative laser in situ keratomileusis patients reported that a fewer number of participants in the CMC group had dry eye symptoms at 2 weeks and 1-month follow-up, but there was no difference between the two groups at 3- and 6-month follow-up visits.[16]

Tear TF-BUT values increased for Groups A and B on subsequent follow-ups, but there was no statistically significant difference between the two groups. Similar results were reported in a study by Comez et al., in which the use of HPMC 0.3% and CMC 0.5% eye drops demonstrated significant improvement in TF-BUT as compared to the baseline, but there was no difference between the two groups.[9]

Only one study participant each from Group A and Group B had an initial burning sensation when they used the respective tear substitutes for the first time. On subsequent usage, there was no discomfort reported, and therefore they continued to use the prescribed medications. Three participants in one study had keratitis, hypersensitivity reactions, and conjunctival hyperemia,[17] while other studies have not reported any adverse effects with the use of CMC.[10,20]

Besides being highly viscous and mucoadhesive, CMC may have some additional properties which could be responsible for the observed higher efficacy of CMC when compared with HPMC. CMC has been demonstrated to have a prolonged ocular residence time and good shear thinning properties in a small-angle neutron scattering and rheology study by? Lopez et al.[18] An experimental study demonstrated that CMC may have a modulatory effect on corneal epithelial wound healing.[21] An earlier study shows that it may have a cytoprotective effect on the ocular surface when used before insertion of contact lens into the eye.[22] However, in the present study, although, we found a statistical difference between the two groups in the OSDI score and Schirmer test values, this difference may not be clinically significant.

The main strength of the study is the relevance of the study in the current scenario where online classes, webinars, along with video calls have increased exponentially due to the current pandemic. People are spending more time in front of the screen, and hence higher number of cases of CVS are likely to be seen in clinical practice. The study has a robust design and included the most clinically relevant tests and questionnaire to assess the condition. The main limitations of the study are the inability to assess patient adherence to the therapy, use of an open-label study design, and the inability to include osmolarity testing.

Both CMC and HPMC tear substitutes were efficacious in reducing subjective symptoms as indicated by improved OSDI score, supported by objective measures Schirmer I test values and TF-BUT. The study clearly gives evidence to support the use of tear substitutes in dry eye due to CVS.

This article talks about the topic of hpmc vs cmc, which puzzled people so much. And introduced their definitions, characteristics and functions separately. At last, there is a conclusion of them to help people know hpmc vs cmc easily.

What is HPMC?

HPMC (Hydroxypropyl Methyl Cellulose): White or off-white fibrous and gritty powder, a solid and flammable stuff that is incompatible with strong oxidant. It is a kind of half-synthetic, inactive, viscous polymer. It is common to be used as lubricating agent for ophthalmology and be an ingredient in oral medicine. 

CHARACTERISTICS OF HPMC

1. High stability: HPMC process has relatively good stability under the wicked condition of high temperature, high humidity, acid-base and so on. It can enhance the stability of the medicine in pharmaceutic preparation. 

2. Good plasticity: HPMC could be used as adhesive and molding agent. It can help the factory produce better pharmaceutical agent because it can improve the mobility of the particle and the stability of the compression molding.

3. High grade of transparency: It can manufacture transparent solution and will not affect the appearance of the preparation due to the transparent characteristic of HPMC.

4. Good adhesion: HPMC shows good adhesion quality in aqueous solution and can be used to make preparations such as eye drops, oral medicine and oral capsule.

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FUNCTIONS OF HPMC

1. Washing industry: HPMC has been widely used in the washing industry. It helps maintain the stability of various ingredients in products such as shampoo, hair conditioner and body wash. It prevents chemical components from separating during storage and transportation. That can guarantee product quality. Apart from that it can help to adjust the foam output and foam quality of the washing products which makes the products more comfortable and easy to use.

2. Construction industry: It is used as an adhesive in applying mortar, plaster, putty powder, or other building materials and is used as paste ceramic tile, marble, plastic decoration, and paste enhancer. It can improve spreading ability and extend the operating time, as well as reducing the amount of cement.

3.Pharmaceutical industries:Coating material; Membrane material; Rate-controlled polymer materials for sustained-release preparations; Stabilizer; Suspension aid; Tablet binder.

What is CMC?

CMC (Carboxymethyl Cellulose): A waterproof, filter and structure support and so on. It is a various particular chemical material that is widely used in medicine, food and paper manufacturing, etc. 

CHARACTERISTICS OF CMC

1. Water retention: CMC can react with water and forms an irreversible reaction, which makes the material has a good water retention quality

2. Adhesion: CMC has strong adhesive quality and could keep the stability of adhesion under different temperatures

3. Molding ability: CMC material can make various shapes

4. Filterable: CMC materials have good filterable quality 

FUNCTIONS OF CMC

1. Medicine: CMC materials are commonly used to make medicine like capsules, tablets, and so on. It has good solubility and progressive releasable ability. 

2. Food: CMC materials can be used as colloidal stabilizer, thickeners, emulsifier, etc., and widely used in beverages, juices, condiments and other food.

3. Making paper: CMC material has good adhesion, it is always used in the process of making paper, so it can improve the quality of paper and decrease the cost of production.

4. Chemical engineering: CMC material can be used in the preparation of thickening agent, emulsifier, anti-seepage agent and other chemical products, widely used. As a kind of green and environmentally friendly chemical material, CMC material is being more and more widely used in all kinds of industries. In the future, with the continuous advance of technology, the application field of CMC materials will be broader.

HPMC (Hydroxypropyl Methyl Cellulose) and CMC (Carboxymethyl Cellulose) are both cellulose-based substances commonly used in various industries. Here are some differences between HPMC VS CMC:

Chemical structure: Both HPMC and CMC are derivatives of cellulose, but their chemical structures differ slightly. 

HPMC is a modified form of cellulose that has been chemically treated with propylene oxide, while CMC is obtained by reacting alkali-cellulose with chloroacetic acid.

Solubility: HPMC dissolves in water to form a clear solution whereas CMC forms a gel-like substance when it comes into contact with water.

3. Viscosity: The viscosity of HPMC is higher than that of CMC for the same concentration at the same temperature.

4. Applications: HPMC is widely used in construction materials like cement mortar, tile adhesive, etc.

In contrast, CMC finds extensive applications in the food industry as an emulsifier or stabilizer because of its high solubility in water.

Overall, both these substances have unique properties that make them useful for different purposes depending on the specific needs of each application area.

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