In Contact - April 2009
I've often discussed 3 & 9 o'clock Staining, as a frustratingly difficult to manage complication of hard lens wear. Additionally I've commented on how varied the management approaches seem to be: Ask ten experts and you?ll probably get eight conflicting management strategies.
On my return from Europe and Africa I was greeted with the usual pile of mail. A package from Holland caught my eye. On opening it I was intrigued and pleased to find a quality textbook. It presented Eef van der Worp?s 200 page thesis 'Corneal Desiccation in Rigid Gas Permeable Contact Lens Wear ? Time to deal with 3- and 9-o'clock staining'.
Eef begins his treatise with a bit on the history and basics of RGPs, physiology, tears, blinking and details complications such as desiccation and staining. The section on grading and tears (and sixteen different human mucin genes) is worth checking out. The complete work is available online at http://arno.unimaas.nl/show.cgi?fid=14422. Give it a chance to load.
The tear section can be found on pages 26-32.
In Chapter 2 Eef reviews how lens comfort was evaluated. He goes on to report that an optimal lens-to-cornea relationship is important for comfortable lens wear. He suggests that we may need to review our traditional fitting techniques in favour of topographically assisted design and I might add, manufacture. He also stresses, as do I, that we need to consider individual corneal eccentricities.
My own experience has shown me how eccentricity can vary widely from one patient to the next and significantly affects the peripheral lens design. From previously reported cornea plana to some extreme cones, we are talking very different eye shapes. Lens dynamics, centre of gravity, and numerous other factors are also affected by the extreme Rx variation of cases at the fringes of the distribution curve. Some of these corneas may need dramatically more edge lift - be it through successively flatter or aspheric curves - or in some instances reverse geometry may be needed in the mid periphery. Other minimally eccentric corneas require little change in geometry (or shape) from lens centre to periphery.
Chapter three gets stuck into the nitty gritty of 3&9 staining and notes how little research has been devoted to this issue. While soft lens staining has been in the news for the past few years, RGP 3&9 staining has received scant attention over the past decades.
Check out page 106 for a novel 3&9 grading scale developed for this thesis and gleaned from the input of many Dutch optometrists and Eef?s medewerkers. A nice effort and a useful addition to our clinical grading scales.
Chapter four looks at the relationship between signs, symptoms and staining issues. Eyes with conjunctival staining showed more corneal staining and symptoms increased if 3&9 staining was present.
The dissertation goes on to list eight variables that can affect 3&9: Five relate to lens design and include edge lift, edge design, optic zone size, lens diameter and back surface geometry. The other three relate to lens performance and include centration, movement and wettability. I might add that two of these may also be affected by design.
The study shows that flat fits, interpalpebral fits and large lenses seem to be risk factors for development of 3&9.
As I've commented before; in one case going bigger may help, in another smaller or steeper. In some cases reduced edge lift may help or a tight periphery may need opening up. Such issues lead us straight into chapter five that looks at findings which show that tear meniscus height is significantly less in RGP wearers compared to non wearers. Diameter may have an effect as would lid attachment versus interpalpebral fitting. Additionally a large, wide tear pool takes up a large volume of the limited tear volume, under the area of peripheral edge lift of the contact lens. Such factors are thought to contribute to this meniscus like thinning or ?bridging? of the tear film between the lid margins and RGP edge ?pool?. Eyeblink type and frequency (as recently reported in this column) was also investigated. Sufferers of 3&9 show a greater incidence of incomplete blinking.
I would add that we should also look at managing the tear film through diet, supplements, meibomian gland expression, compresses, reducing make up and avoiding liquid soaps. Eliminating preservatives in eye drops and solutions coupled with ?Think Blink? instruction on complete blinking should be considered.
Of course a refit into silicone-hydrogels - in sphere, toric or multifocal form - and resultant ?bandaging?, thus preventing ?exposure? in the limbal area, is a worthy management strategy. Particularly if RGP tweaks do not resolve what can otherwise be a chronic, intractable condition. H202 disinfection keeps chemicals to the absolute minimum for further potential benefit.
In cases of 3&9 staining we need to manage everything!
Full Credit.
Full credit to Eef who is becoming ever more widely known on the international lecture circuit and divides his time between the US and Netherlands. he's active in many aspects of contact lenses and research and a nice bloke to boot. He also recently initiated an email newsletter. Speakers of Dutch, Afrikaans or Flemish or those with other Germanic skills may also like to read the Dutch sections of his organised, well presented thesis.
As a born and bred Pretorian, I can make sense of most of Eef?s Dutch text.
Another aspect of that birthright makes me rather pleased to see the ascendancy of the Bulls in Super 14. It's been an interesting start. At the time of writing the Bulls remain the only unbeaten team after the full moon upsets of round five. Here?s hoping they can better the ?Canes at home.
It?ll be interesting to see what happens to the embattled Formula 1 circus this year. Former Ferrari specialist, Ross Brawn, now owns Honda?s F1 team after they pulled out of F1. Mercedes will now provide motive power. It will be interesting; particularly with a host of rule changes designed to encourage overtaking and save money.
In pandering to the Greenies, complex (expensive, problematic) Kinetic Energy Recovery Systems are being introduced.
Will we see electric Formula 1 cars in the not too distant future?
Technology advances amazingly quickly. Although the current economic climate may slow it fractionally, future advances across the range of human endeavour will continue to amaze us.
For more information or any comments email Alan at incontact@optom.co.nz.