The effect of pH, dilution, and temperature on the viscosity of ocular lubricants—shift in rheological parameters and potential clinical significance

Abstract

Objective To investigate the effect of temperature, dilution, and pH on the viscosity of ocular lubricants. Design Laboratory based investigation of viscosity. Participants No human subjects. Methods Hypromellose 0.3%, sodium hyaluronate 0.4%, carboxymethylcellulose sodium 0.5%/glycerin 0.9%, and carmellose sodium 0.5% were investigated. Ostwald capillary viscometers were utilised for viscosity measurements. The kinematic viscosity of each lubricant was tested quantitatively from 22 to 40 1C, and over a pH range of 5-8 under isothermal conditions. The kinematic viscosity of each eye drop was also tested under dilution by varying the mass fraction of each eye drop under isothermal conditions. Main outcome measure Changes in kinematic viscosity. Results Hypromellose 0.3% had an initial pH of 8.34, while the other lubricants had a pH close to neutral. From 22 to 35 1C, the kinematic viscosity of sodium hyaluronate 0.4 fell by 36% from 37.8 to 24.4 mm 2 /s, carboxymethylcellulose sodium 0.5%/glycerin 0.9% fell by 35% from 16.98 to 11.1 mm 2 /s, hypromellose fell by 37% from 6.89 to 3.69 mm 2 /s, and carmellose sodium 0.5% fell by 25% from 2.77 to 1.87 mm 2 /s. At 32 1C only sodium hyaluronate 0.4%, and carboxymethylcellulose sodium 0.5%/glycerin 0.9% retained sufficient kinematic viscosity to maintain precorneal residence. Kinematic viscosities of all the topical lubricants were unaffected by pH but decreased significantly with dilution. Conclusions This study suggests that currently used ocular lubricants have limited bioavailability due to reductions in viscosity by temperature and dilutional changes under physiological conditions. Developing lubricants with stable viscosities may maximise therapeutic efficacy.

Multitarget, quantitative nanoplasmonic electrical field-enhanced resonating device (NE 2 RD) for diagnostics

“…To evaluate the performance of our platform under various conditions, we tested the system for varying internal (e.g., pH, ionic content, and strength) and external (e.g., temperature) characteristics. The performance of the unmodified well-plate NE 2 RD prototype was first evaluated with diverse buffers ranging from pH 5.0 to pH 10.0, covering the ionic strength of various biological specimens including urine (30), tears (31), and sweat (32). A wide change in ionic strength and pH did not affect the performance of the device significantly, and the signal fluctuations in spectral color (wavelength) were smaller than the spectral resolution of the platform (1 nm) (n = 16, P > 0.05) ( Fig.…”

Eye

“…Carbomer, which does not form xerogels, used in the concentration 2 mg/mL, improves the availability and the prolonged activity of some active substances. No blurred vision was reported [51].…”

Tear Production Levels and Dry Eye Disease Severity in a Large Norwegian Cohort

“…Dry eye disease (DED) is a multifactorial disorder, which can be caused by an alteration in the quality or quantity of tear film's three layers 1 . DED can result from primary factors such as lacrimal gland atrophy and secondary factors such as pathological changes in the eyelids, conjunctiva, or cornea along with other influencing factors, including immunological processes, neurotransmitters, hormones, pharmaceuticals, contact lenses and environmental pollution [2][3][4] .…”