Tear film evaluation

Slit-lamp examination without dyes or anesthetic Observe tear meniscus height Observe quality of tear film Evaluate integrity of ocular surface Evaluate lids, lashes... 

There have been limited field and controlled exposure studies that evaluated human reactions to carpet emissions. Winfield (1987) described a USA primary school where odor, headache, nausea, fatigue and mucosal irritation were reported by a high proportion of the students. Elevated indoor air concentrations of styrene (900-4000 xg m 3) were found, which were believed to be due to a SB R latex-backed carpet which had been installed several years previously. The carpet was removed and the ill-effects were reported to abate. Johnsen et al. (1990) exposed asthma sufferers to a foam rubber-backed carpet in a room chamber. While no clinical effects on lung function were observed, objective eye measurements found that there was a change in tear film quality. This was proposed to result from a degreasing effect of lipophilic VOCs, identified as toluene and acetone (Wolkoff, Nielsen and Hansen, 1990). 

Topical ocular fluorescein can be used to evaluate two key aspects of the lacrimal system.These are the stability of the precorneal tear film and the patency of the lacrimal drainage system. 

Pflugfelder SC,Tseng SCG, Sanabria O, et al. Evaluation of subjective assessments and objective diagnostic tests for diagnosing tear-film disorders known to cause ocular irritation. Cornea 1998 17 38-56. 

Evaluation of the lipid layer has recently received much attention. There have been many methods and types of instrumentation proposed in the literature, including the use of videokeratography to detect lipid-induced reversible changes in corneal contour and a continuous functional visual acuity test to measure the effect of the lipid layer on functional vision. However, there is not as yet an easily accessible uniform method to assess the lipid layer of the tear film. 

Measurement of the tear breakup time (TBUT) is one of the more common tests to evaluate the tear film (Figure 24-7).This test is most frequently done using NaFl and the cobalt filter on the slit lamp. Instability of the tear... 

Retropulsion of the globe (rules out orbital tumor) Biomicroscopy (evaluates corneal integrity/tear film/ superior limbic keratoconjimctivitis)... 

Examination of the nonhuman primate requires sedation (Kuhlman et al., 1992). The highly mobile primate eye and their anxious nature when handled mandate a chemically restrained animal for an adequate examination. Human safety considerations also are a factor. Ketamine hydrochloride works well due to its safety and controllable duration. The time to onset of mydriasis following tropicamide administration must be balanced against the time to the animal s recovery from ketamine s sedative effect. A refinement is the addition of a water-based lubricant eye drop at the time of tropicamide administration. This helps protect the cornea from desiccation while the monkey is sedated and may also aid in achieving prompt and satisfactory dilation by increasing tropicamide residence time in the precorneal tear film. Working with a seasoned technical staff appropriately trained for ketamine injection, the examiner can evaluate many primates in a reasonable time. 

Ousler GW III, Michaelson C, Christensen MT (2007) An evaluation of tear film breakup time extension and ocular protection index scores among three marketed lubricant eye drops. Cornea 26 949-52... 

Clinical evaluation Several subjects (usually 5 to 10) wore one test contact lens in one eye and one control contact lens in the other eye. The lenses were analyzed after a minimum of 1 h of wear for surface characteristics of wettability and surface deposition. The wettability rating scale was 0-4, where 0 meant more than two thirds of the anterior lens surface unwetted by tear film and 4 represented complete (100%) wetting by tear film. The deposition scale was 0-4, where 0 represented no surface deposits and 4 multiple deposits of 0.5 mm diameter or larger. 

During a small scale trial the level of contaminants remaining in PCR can be readily observed. In particular, the size and frequency of gels and dirt particles may not only affect the performance of the finished product but also lead to excessive scrap levels during manufacturing. Similar to the sensory assessment, the level of contaminants can be evaluated visually. These observations should also include an assessment of build up on dies or screen packs, and in film production, tear-off or bubble loss. 

To evaluate this concern, LLDPE blown films have been fabricated with PPA levels two or four times those typically used. Evaluation of mechanical properties such as tear, tensile and dart impact lest indicated no positive or negative effect due to the PPA s presence. Given that the... 

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