Mike Johnson

Changes in the tear film and ocular surface from dry eye syndrome

Dry eye syndrome (DES) refers to a spectrum of ocular surface diseases with diverse and frequently multiple aetiologies. The common feature of the various manifestations of DES is an abnormal tear film. Tear film abnormalities associated with DES are tear deficiency, owing to insufficient supply or excessive loss, and anomalous tear composition. These categorizations are artificial, as in reality both often coexist. DES disrupts the homeostasis of the tear film with its adjacent structures, and adversely affects its ability to perform essential functions such as supporting the ocular surface epithelium and preventing microbial invasion. In addition, whatever the initial trigger, moderate and severe DES is characterized by ocular surface inflammation, which in turn becomes the cause and consequence of cell damage, creating a self-perpetuating cycle of deterioration. Progress has been made in our understanding of the aetiology and pathogenesis of DES, and these advances have encouraged a proliferation of therapeutic options. This article aims to amalgamate prevailing ideas of DES development, and to assist in that, relevant aspects of the structure, function, and production of the tear film are reviewed. Additionally, a synopsis of therapeutic strategies for DES is presented, detailing treatments currently available, and those in development.

The agreement and repeatability of tear meniscus height measurement methods

Purpose. This study investigated the agreement and repeatability of five techniques of measuring tear meniscus height (TMH). Methods. Pairs of TMH measurements were obtained from one eye of 25 normal subjects with five techniques: optical coherence tomography in cross-section (OCT) and optical pachymetry in cross-section (PACH), without fluorescein; and 5 minutes after the instillation of fluorescein, optical pachymetry en-face (SL-F) and in cross-section (SL-X), and video capture en-face (VC). These 10 measurements were taken on different days within a period of 21 days. Additionally, immediately successive replicates were taken at the first visit when VC was used, allowing for the separation of technique repeatability from true day-to-day variation in TMH. Results. Ninety-five percent confidence intervals for the mean TMH and 95% repeatability coefficients for repeated testing on separate occasions were: 0.25 to 0.29 mm, 0.14 mm—OCT, 0.30 to 0.36 mm, 0.13 mm—PACH, 0.27 to 0.34 mm, 0.092 mm—SL-F, 0.35 to 0.41 mm, 0.19 mm—SL-X, and 0.30 to 0.38 mm, 0.088 mm—VC. Reported repeatability coefficients are averages because, despite a relatively narrow experimental range, the measurements of low TMH were generally more repeatable than those of large TMH. Ninety-five percent limits of agreement were wide for all pairwise comparisons and included zero, indicating that the methods used in this study are interchangeable when taking single recordings, at least on subjects without dry eye. Conclusions. The average TMH of the five techniques was similar, although OCT and SL-X tended to record lower and higher values, respectively. However, their agreement for single recordings was poor, an inevitable consequence of the low intertest repeatability found for all methods. A much improved repeatability for immediate replicates indicated that this, in turn, was principally caused by a large day-to-day variation in TMH rather than measurement error.

The Effect of instilled fluorescein solution volume on the values and repeatability of TBUT measurements.

Purpose: To investigate how the volume of instilled fluorescein solution alters invasive tear breakup time (TBUT) and the standard deviation (SD) of multiple recordings, and to determine the volume of fluid supplied by traditional fluorescein-impregnated strips (FS) and a micropipette calibrated to dispense 1 μL. Methods: TBUT was measured 3 times in the right eyes of 46 subjects following the instillation of 1, 2.7, and 7.4 μL of fluorescein solution by micropipette and the use of a wetted FS. The volume of fluid delivered to an eye by FS and a micropipette set for 1 μL was estimated by weighing each before and after use. Results: The volume of fluorescein solution instilled before measurement influenced TBUT (P < 0.001). Increasing the delivered volume from 1 to 2.7 μL lengthened TBUT (P < 0.001), but an additional increase in volume to 7.4 μL was not associated with a further change in TBUT (P = 0.50). Differences between TBUT values measured after using FS and a micropipette calibrated for 1 μL were not significant (P = 0.95). No significant differences were found in the repeatability of TBUT recordings between the instillation techniques used in this study (P = 0.18), although measurement variability increased with mean TBUT for all techniques. With the FS instillation technique described herein, the average volume of fluorescein solution they supplied was less than that delivered by a micropipette set for 1 μL (P = 0.017), but the range of volumes transferred by FS was greater. Conclusions: Values of TBUT are dependent on the volume of fluorescein solution instilled before measurement; thus, attempts should be made to standardize this variable. Accurate estimation of TBUT requires more recordings to be averaged than are normally taken, unless breakup time is very short.

Educational dialogues – By Karen Littleton & Christine Howe

What are these “online literacies” that this substantial book talks about in the context of their possession by adolescent learners? By analogy with “computer literacy” and “IT literacy”, you may expect the phrase to mean the young users’ fluency with IT applications to solve their problems. Not so! In fact, neither the book’s editor nor the various authors give an explicit definition of what they mean by the term. The way in which this phrase is used in the book is, in fact, closer to the traditional meaning of ′′literacy′′ than to fluency with IT applications. I would define it on that basis as the young people’s ability to express themselves and interact with others—and by this means make sense of themselves, their experiences and the contexts in which they live.

Hodgson, V et al ed (2014) The design, experience and practice of networked learning Springer (Berlin) isbn 978‐3‐319‐01940‐6 281 pp £93.50 e‐book (boards £117) http://www.springer.com/education+%26+language/learning+%26+instruction/book/978‐3‐319‐01939‐0

This particular volume details how to organise the implementation and delivery of any national nonhigh-stakes achievement test. The book has four distinct parts. The first deals with the logistics of a national assessment and includes five chapters about the administration of the test and its stakeholders, how to select them, and their roles. The second part deals with sampling the subjects and the most important tasks to deliver step-by-step a national assessment in schools. Part 3 strictly concerns the use of technology in data collection and analysis. The last chapters address weighting, sampling error in the calculation of estimates, and working out jack knife weightings.