Associate Professor Mark Roth
BSc(Pharm) BAppSc(Optom)PGCertOcTher NEWENCO FAAO
Re-esterified omega-3 for dry eyes
Oral consumption of re-esterified omega-3 fatty acids is associated with improvement in tear osmolarity, omega-3 index levels, TBUT, MMP-9 and OSDI symptom scores.
In a multicentre, prospective, interventional, placebo-controlled, double-masked study, 105 subjects were randomised to omega-3 (n = 54) and control group (n = 51).
The omaga-3 group received four softgels containing a total of 1,680 mg of eicosapentaenoic acid/560 mg of docosahexaenoic acid. The control group received 3,136 mg of linoleic acid, daily for 12 weeks.
Subjects from both groups were measured at baseline, week six, and week 12 for tear osmolarity, TBUT, OSDI, fluorescein corneal staining, and Schirmer test with anaesthesia. MMP-9 testing and omega-3 index were done at baseline and at 12 weeks.
The study found that a statistically significant reduction in tear osmolarity was observed in the omega-3 group versus control group at week six (-16.8 +/- 2.6 vs -9.0 +/- 2.7 mOsm/L, p = 0.042) and week 12 (-19.4 +/- 2.7 vs -8.3 +/- 2.8 mOsm/L, p = 0.004).
At 12 weeks, a statistically significant increase in omega-3 index levels (p < 0.001) and TBUT (3.5 +/- 0.5 s vs 1.2 +/- 0.5 s, p = 0.002) was also observed. The omega-3 group experienced a significant reduction in MMP-9 positivity versus control group (67.9% vs 35.0%, p = 0.024) and OSDI scores decreased significantly in omega-3 (-17.0 +/- 2.6) versus control group (-5.0 +/- 2.7, p = 0.002).
Cornea 2016; July 20 (Epub ahead of print).
The case for early intervention in pterygium
A study published in Cornea concludes that it is best to operate when the size of the pterygium corneal area is still small.
To establish determining factors for fast corneal sensitivity recovery after pterygium excision, study authors recruited 32 eyes of 14 males and 18 females with primary nasal pterygium.
Differences in corneal sensitivity (in the four quadrants and the centre using a Cochet-Bonnet esthesiometer), pterygium corneal area (PCA), tear osmolarity, tear break-up time, Schirmer test, and ocular symptoms were analysed before and one month after lesion excision. The relationship between corneal sensitivity recovery (difference between the two time points; CS1 - CS0) and the other features was assessed.
Corneal sensitivity recovery after pterygium excision showed important variability. The only studied factor that seems to be determinant could be pterygium corneal area.
The study authors concluded that it would be advisable to operate when the lesion is relatively small, with lower surgical injury and faster and complete recovery, thus protecting ocular surface homeostasis.
Cornea 2016 Jun 29 (Epub ahead of print).
Thumb-suckers less likely to develop allergies
Young children who suck their thumbs or bite their nails may be less likely to develop allergies later in childhood, according to a New Zealand study that spanned three decades.
Researchers analysed data from an ongoing study of more than 1,000 children born in New Zealand between the years 1972 and 1973. Parents reported the thumb-sucking and nail-biting habits of their children at ages five, seven, nine and 11 years. Researchers also tested the children for allergies using a skin-prick test when they were 13 years, and then followed up with the children again when they were 32 years.
It was found that frequent thumb-suckers or nail-biters had a lower risk of atopic sensitisation at age 13 years (odds ratio 0.67, 95 per cent confidence interval 0.48–0.92, p = 0.013) and age 32 years (odds ratio 0.61, 95 per cent confidence interval 0.46–0.81, p = 0.001). These associations persisted when adjusted for multiple confounding factors.
Children who had both habits had a lower risk of atopic sensitisation than those who had only one habit. No associations were found for nail-biting, thumb-sucking, and asthma or hay fever at either age.
The study’s authors suggested that these results lend support to the ‘hygiene hypothesis,’ which holds that environments that have too little dirt and germs may make children more susceptible to certain conditions, including allergies.
Pediatrics Jul 2016, e20160443; DOI: 10.1542/peds.2016-0443.
Cancer, diabetes and detection bias
According to a study that appeared in the US journal Cancer, the association between diabetes and cancer is strongest right after a diabetes diagnosis. The finding suggests that the epidemiologic associations between diabetes and cancer can be partially explained by a detection bias around the time of a diabetes diagnosis.
Researchers conducted a retrospective, population-based cohort study of more than one million adults living in Ontario, Canada, to evaluate the association between diabetes diagnosis and the incidence of cancer in three time periods: within the 10 years before a diabetes diagnosis, within the first three months after a diabetes diagnosis, and from three months to 10 years after a diabetes diagnosis.
During a median five years after diabetes diagnosis (or matched date), about 36,000 incident cancers were identified in those with diabetes and 33,000 in controls. Those with diabetes had a 62 per cent higher cancer risk in the first three months after diabetes diagnosis; however, they showed no elevated risk thereafter.
In addition to the findings suggesting detection bias, patients with diabetes were 23 per cent more likely to be diagnosed with cancer in the 10 years before diabetes diagnosis, relative to controls.
The results of the study show that individuals with diabetes had a significantly higher risk of most cancers, which was limited to the time periods before and immediately after a diabetes diagnosis. The highest risk period was observed within the first three months after a diabetes diagnosis, suggesting at least a partial role of detection bias.
Cancer 11 Jul 2016; DOI: 10.1002/cncr.30095.
What’s a ‘typical’ optic nerve head?
Do atypical optic nerve head (ONH) characteristics necessarily lead to atypical biomechanical responses to elevated IOP? Do typical biomechanical responses necessarily come from ONHs with typical characteristics?
In a recent study, researchers addressed these two specific questions. They found the answer to both questions is: no.
Researchers generated 100,000 ONH numerical models with randomly-selected values for the characteristics, all falling within the ranges of normal ONHs. The models were solved to predict their biomechanical response to an increase in IOP. Researchers classified ONH characteristics and biomechanical responses into ‘typical’ or ‘atypical’ using a percentile-based threshold. They then studied the effects of varying the percentile threshold.
When researchers classified the extreme five per cent of individual ONH characteristics or responses as atypical, only 28 per cent of ONHs with an atypical characteristic had an atypical response. Almost 29 per cent of typical responses came from ONHs with at least one atypical characteristic.
Ultimately, the results challenge the assumption that ONHs with atypical sensitivity to IOP must have atypical characteristics. This finding suggests that the traditional approach of identifying risk factors by comparing characteristics between patient groups (for example, ocular hypertensive vs primary open angle glaucoma) may not be a sound strategy.
Exp Eye Res 23 Jun 2016;149:40-47. doi: 10.1016/j.exer.2016.06.012 (Epub ahead of print).
Surprise! Pterygium in low UV index areas
A Canadian study has found that in a geographic area with low ultraviolet light index, the frequency of epithelial neoplasia seen in excised pterygium specimens was higher than expected. The rate was 2.33 per cent.
Of 215 pterygium specimens received at the Henry C Witelson Ocular Pathology Laboratory, McGill University, Montreal, ocular surface squamous neoplasia was identified in five. Four patients were women and one was a man, and age did not appear to influence the results.
All five lesions were classified according to the Armed Forces Institute of Pathology recommendations. Conjunctival intraepithelial neoplasia I was seen in three cases, and conjunctival intraepithelial neoplasia II and III were each seen in one case.
‘Our frequency rates were close to rates reported in Sydney and even higher than in Florida, regions that are known to have higher yearly exposures to UV rays than Montreal,’ the authors wrote.
The relatively high rate of dysplasia in a low ultraviolet light index area challenges the main cause of this disease in our population. The authors suggested that all pterygium samples should be sent for histopathological evaluation, even in areas with low ultraviolet light index.
Saudi J Ophthalmol 2016; doi:10.1016/j.sjopt.2016.02.007.
There’s the rub
A study published in Clinical and Experimental Optometry has shown the adverse effects of eye-rubbing before and after contact lens insertion.
To examine the prevalence of ‘removal-relief’ rubbing and its potential consequences, rubbing histories were recorded for contact lens wearing normal and keratoconic patients as well as for normal non-contact lens wearers. Analogue scaled responses were used to identify and compare abnormal rubbing habits.
Researchers found that contact lens wearing patients, both with and without keratoconus, reported significantly more rubbing before contact lens insertion (p < 0.05) compared to non-contact lens wearers. Eye-rubbing after contact lens removal (‘removal-relief’ rubbing) was found to be significantly more prevalent among contact lens-wearing keratoconic patients compared to contact lens-wearing non-keratoconic patients (p < 0.001 in both cases).
The author concludes that rubbing-related trauma occurring before contact lens insertion may predispose the cornea to wound healing activities and greater levels of adverse response to contact lens wear. Such adverse responses could predispose the cornea to greater trauma, which occurs in response to rubbing on removal of contact lenses.
Strong counselling to avoid eye rubbing is often not an adequate form of management for a significant number of patients with keratoconus. Evidence of relapses indicates the need for better and more frequent methods of counselling for keratoconus patients.
Clin Exp Optometry 2016; 99: 4: 366-372. doi: 10.1111/cxo.12343.