Edinburgh optometrist David Crystal MCOptom DipTp specialises in diagnosing and treating the root cause of dry, watery or uncomfortable eyes using advanced techniques at the forefront of the optometry profession.


If your eyes are white and healthy you shouldn't feel the need to touch them. If you periodically have the urge to rub, then its possible the cause of your discomfort is Demodex.

It has been estimated that Demodex is the most common, but often overlooked, cause of 29 - 74% of eyes with ocular surface inflammation from blepharitis and meibomian gland dysfunction, which constitute 47% of the patients seen in clinical practices by optometrists. It is very common.

The reason you've not heard about Demodex is because ophthalmology "buried" the subject as there was simply no treatment. This all changed in November 2013 with publication of research papers that underpin our current treatment knowledge.

At Crystal Optometry, David Crystal has a specialist interest in this field and has been in dialogue with the doctors who did the original research. It's an evolving science too and he has been refining new treatment techniques and has enough experience to be ahead of the professional curve in the UK, to the extent that optometrists in Edinburgh have requested his advice.

So here are the facts about Demodex.

Firstly you may not need to do anything since, for the majority of people Demodex cause no symptoms. But here's the problem.... 

There is now compelling evidence that links the presence of Demodex to the chronic lid margin disease blepharitis, meibomian gland dysfunction and ocular surface inflammation from blepharokeratitis, which can be sight threatening. Collectively, this group of conditions, when associated with Demodex is known as Ocular Demodecosis.

Ocular Demodecosis causes itching, soreness, redness and crusting of the lid margins, and blurred vision. It is the major cause of evaporative dry eye which is the most common condition presenting to optometrists. There is also an association with rosacea.

Since Demodex multiply with time, especially when the immune system is depressed in poor health, the risk to vision also increases with age.  If you're young with Demodex you may want prophylactic treatment.


Demodex is an ectoparasite mite which colonises the skin of many animals. In humans, two species occur. Demodex Folliculorum is found in the eyelash follicles and Demodex Brevis lives deeper in the meibomian glands and sebaceous glands of the lashes.

The prevalence of Demodex is quoted as 84% of the population at age 60 and 100% of those older than 70 years. In our Edinburgh optometry practice we find around 15% of all patients show the signs.

You cannot see them yourself on your eyelashes because they are not there! We use slit-lamp biomicroscopy x40 magnification. They reside inside the skin at the base of eyelashes and they hate light.

At night male Demodex leave the hair follicles moving slowly at 6-8mm/ hour to find a female and mate. Eggs are laid just inside the eyelash follicle. Nymphs hatch 3-4 days later and they take about a week to develop into adults. The total lifespan of a Demodex is 18 days. Outside of the body a Demodex can survive 56 hours in a drop of oil. The mites have eight claws at the front which they use for locomotion and they feed off the sebum-oil surrounding eye lash follicles.

The characteristic sign of Demodex is cylindrical dandruff (CD) at the base eyelashes and is a mixture of keratinised epithelial cells and sebum likely caused by Demodex clawing in and out of the eyelashes at night. The mites carry bacteria, such as staphylococci.

Up to 5 -10 CD lashes mild - moderate (easier to treat).
More than 10 CD mod - severe (harder to eradicate)

Treatment is based on waiting for eggs to hatch killing the mites and preventing them mating.

Although the subject of Demodex has been normalised by the press and media, it is not "normal" to have them and cross-infection is by direct contact with someone who has a Demodex infestation, or from pillows and towels.

Our approach is eradication of Demodex within 6 weeks which we achieve for 7 out of 9 patients.

But first, in order to demonstrate with certainty the diagnosis of ocular demodecosis we remove a few eyelashes and examine them at 540x magnification using a video-microscope.

Should you wish it we will do everything possible to eradicate the Demodex. Treatment is based on delivering mitacidal agents over two life cycles. This is done by a combination of in-practice "clean and kill" sessions lasting 45 minutes and a supportive home treatment. All products and instructions are provided. Up to 6 weekly return visits are needed.

With experience we have found that removing the CD by using the BlephEx procedure alone, whilst cleaning the eyelashes perfectly to the base, lasts no longer than one week before the signs of Demodex return. So we are using ground-breaking innovative treatments built upon past research which have a solid scientific foundation. And it works.

Respect to the Demodex, eradicating them is difficult and time consuming. Future products will no doubt have improved follicular penetration to reach the deepest Demodex Brevis. Only then could we guarantee removal of the risks of ocular demodecosis.  

Evolving an effective treatment protocol for Demodex raises the tantalising prospect of finding a cure for the main reasons why patients suffer from the discomfort of evaporative dry eye.

Download Demodex treatment CET article for Optometrists

Optometrists CET Demodex treatment article             

Video of Demodex feeding on cuticle sebum