Tear film break up time

The tear break-up time test assesses the stability of precorneal tear film. Break-up times of less than 10 seconds are considered abnormal. 

Chitosan has been shown to increase precorneal drug residence times. The cationic chitosan slows tear drainage by increasing viscosity and by mucoadhesion with the negatively charged mucin. Up to a threefold increase of the corneal residence time has been achieved by the addition of chitosan to topical vehicles [5]. Carbomer gels at 0.3% have also been shown to be effective in prolonging the tear film break-up time [6]. Hyaluronic acid has been reported to... 

Doughty MJ, Jalota Y, Bennett E, et al. Use of high molecular weight fluorescein (fluorexon) ophthalmic strip in assessments of tear film break-up time in contact lens wearers and non-contact lens wearers. Ophthal Phys Opt 2005 25 119-127. 

Isreb M, Greiner J, Korb D, et al. Correlation of hpid layer thickness measurements with fluorescein tear film break-up time and Schirmer s test. Eye 2003 17 79-83. 

Dry eyes have been reported after the systemic or ocular use of timolol (360). A sensation of dryness in the eyes can develop and is usually transitory. There can be a reduction in the Schirmer test and tear film break-up time. Symptomatic superficial punctate keratitis in association with complete corneal anesthesia has been observed (361). 

Methylcellulose is a vehicle used in eye-drops and contact lens solutions (SEDA-1, 369). It is non-irritant and has a good refractive index. A 1% solution is well retained in the conjunctival sac. Corneal cultures have been stimulated by methylcellulose, resulting in increased growth of cells (2) tear-film break-up time was increased four-fold with 2% methylcellulose. Hydroxypropyl methylcellulose is also used as artificial tears for people with dry eyes (3). 

Personal Atopy (allergies, asthma, eczema) seborrheic dermatitis Work stress Gender Lower job status and pay Increased tear-film break-up time... 

Both allergic and irritant mechanisms have been proposed as explanations for eye symptoms. More rapid tear-film break-up time, a measure of tear film instability, is associated with increased levels of symptoms. Fat-foam thickness measurement and photography for documentation of ocular erythema have also been used. Some authors attribute eye symptoms at least in part to increased individual susceptibility based on those factors. In addition, office workers with ocular symptoms have been demonstrated to blink less frequently when working at video display terminals. Conjunctival staining with fluorescent dyes is a common clinical test for conjunctivitis sicca. 

Alcon. Tear film break up time, www.systane.com. Accessed 1 July 2014... 

Dibajnia P, Mohammadinia M, Moghadasin M, Amiri MA. Tear film break-up time in bipolar disorder. Iran J Psychiatry 2012 7(4) 191-3. 

The authors note that the munber of SRS subjects who were healthy and willing to participate in an exposure study was small relative to the numbers cited by community groups as adversely affected by MTBE. Thus, there was likely to have been a self-selection bias that the authors suggest would have been in the direction of deterring even more sensitive individuals from participating. They also state that time constraints prevented the use of additional neurobehavioural tests or other objective markers (e.g., tear film) that may have been more sensitive. However, tear film break-up tests had been incorporated in the chamber studies of [30,56,57] in which no effect of exposure to MTBE was observed on this parameter. 

Dry eye symptoms and significant ocular surface disease frequently occur in patients taking isotretinoin.The associated symptoms may be accompanied by blepharocon-jimctivitis. The presence of isotretinoin in tear fluid decreases stability (and tear break-up time) of the lipid layer of the tear film but may also cause a decrease in aqueous production, leading to ocular surface dryness. These effects could be responsible for the dry eye symptoms, contact lens intolerance, superficial punctate keratitis, and conjunctival irritation accompanying isotretinoin therapy. Use of artificial tear preparations may help to alleviate the associated discomfort. 

Under normal conditions the various components of the tear film are continually produced in sufficient quantity, not only to cover the ocular surfece but also to supply a reservoir of tears that is stored at the margin of the upper and lower eyelids. The movement of the upper eyelid distributes this reservoir, called the tear river or tear meniscus, during blinking or voluntary lid closure. As the tear film thins and breaks up, the blink reflex is stimulated. The down-phase of each blink compresses the superficial lipid layer, and the up-phase redistributes the lipid layer, which remains in a fairly dynamic state well after the completion of the blink. Each time the eyelid reopens, a new tear film layer is spread across the ocular surfece. The blink itself may also augment meibomian gland expression. 

---