Wednesday, May 21, 2008

Abstract: All lipids are not equal...

This is an interesting one, not all that new in concept but less technically overwhelming than some other publications on the topic.

It's basically another reminder to be cautious about oversimplifying the classic old "three layers to the tear film" model where we think of the meibomian glands as the source of the oily "evaporation-retarding" layer (incidentally, for those interested that broader role of retarding evaporation is also subject to some serious questioning if you dig deeper - click here for an interesting discussion by Dr. Holly). While most of the lipid clearly comes from the MGs the lipids in the tear film itself are different enough from the lipids in what the MGs put out that we can't assume healthy MGs will produce a healthy lipid component.

On the lipid composition of human meibum and tears: Comparative analysis of nonpolar lipids.
Butovich IA.
Invest Ophthalmol Vis Sci. 2008 May 16. [Epub ahead of print]

PURPOSE: To qualitatively compare the nonpolar lipids present in meibomian gland (MG) secretions (samples T1) with aqueous tears (AT) collected from the lower tear menisci of healthy, non-dry eye volunteers using either glass microcapillaries (samples T2) or Schirmer test strips (samples T3).

METHODS: Samples T1-T3 were analyzed using high pressure liquid chromatography/positive ion mode atmospheric pressure chemical ionization mass spectrometry. Where possible, the unknown lipids were compared with known standards.

RESULTS: Samples T1 had the simplest lipid composition among all the tested specimens. Samples T2 and T3 were very similar to each other, but remarkably different from samples T1. In addition to all the compounds detected in samples T1, there were large amounts of lower molecular weight wax esters and other compounds found in samples T2 and T3. No appreciable amounts of fatty acid amides (e.g. oleamide), ceramides, or monoacyl glycerols were routinely detected in any of the samples. The occasionally observed minor signals of oleamide (m/z 282), were attributed to the contamination of the samples with common plasticizers routinely found in plasticware extractives and/or organic solvents.

CONCLUSIONS: The MG is a prominent source of lipids for the tear film. However, it would have been a mistake to exclude from consideration other likely sources of lipids such as conjunctiva, cornea, and tears produced by the lacrimal glands. Our data showed that lipids in AT are fundamentally different from, and more complex than, MG secretions, which necessitates a more cautious interpretation of the functions of the latter in the tear film.

Newsblurb: IPL for MGD

Dr. Toyos presented an update on using dermatological treatments in an attempt to improve meibomian gland function. For those not familiar with intense pulsed light, it's been used in rosacea treatment for quite some time, but here, OSN is reporting on a study Dr. Toyos presented in Italy about IPL and broadband light for treating meibomian glands.

OSN Supersite, 5/19/2008
Dermatological treatment may have application as dry eye therapy

Patients receive treatment in four selected facial areas. Tear break-up time and Schirmer's tests are performed during the first visit to establish baseline values before first treatment, before all subsequent treatments, and at 1, 3 and 6 months after completion of the treatment to assess the efficacy on dry eye symptoms. An average of four to five monthly treatments are usually necessary to achieve stable results, he said.

"In our patients, we found an average increase of [tear break-up time] of 47% and 33% with [intense pulse light] and [broadband light], respectively, and an increase of 60% with [intense pulse light] and 84% with [broadband light] for Schirmer's test," Dr. Toyos said.

Abstract: Blepharitis strategies...

Nice little state-of-the-union summary for blepharitis in the Canadian Journal of Ophthalmology.

Blepharitis: current strategies for diagnosis and management.
Jackson WB.
Can J Ophthalmol. 2008 Apr;43(2):170-9

BACKGROUND: The aim of this article is to present a consensus on the appropriate identification and management of patients with blepharitis based on expert clinical recommendations for 4 representative case studies and evidence from well-designed clinical trials.

METHODS: The case study recommendations were developed at a consensus panel meeting of Canadian ophthalmologists and a guest ophthalmologist from the U.K., with additional input from family doctors and an infectious disease/medical microbiologist, which took place in Toronto in June 2006. A MEDLINE search was also conducted of English language articles describing randomized controlled clinical trials that involved patients with blepharitis.

RESULTS: Blepharitis involving predominantly the skin and lashes tends to be staphylococcal and (or) seborrheic in nature, whereas involvement of the meibomian glands may be either seborrheic, obstructive, or a combination (mixed). The pathophysiology of blepharitis is a complex interaction of various factors, including abnormal lid-margin secretions, microbial organisms, and abnormalities of the tear film. Blepharitis can present with a range of signs and symptoms, and is associated with various dermatological conditions, namely, seborrheic dermatitis, rosacea, and eczema. The mainstay of treatment is an eyelid hygiene regimen, which needs to be continued long term. Topical antibiotics are used to reduce the bacterial load. Topical corticosteroid preparations may be helpful in patients with marked inflammation.

INTERPRETATION: Blepharitis can present with a range of signs and symptoms, and its management can be complicated by a number of factors. Expert clinical recommendations and a review of the evidence on treatment supports the practice of careful lid hygiene, possibly combined with the use of topical antibiotics, with or without topical steroids. Systemic antibiotics may be appropriate in some patients.