Current

Research Eye

accelerated c e l l loss from the epithelium in

humans.

REFERENCE

1. Loewenstein, W.R. (1975) Permeable Junctions. C o l d Spring Harbor Symp. Quant. Biol. , 40, as-h?

su r fac t an t s such as benzalkonium chlor ide) , r e s u l t i n a very much higher r i s e in glucose permeabil- i t y , whereas the permeation behavior of l a c t a t e and pyruvate a re influenced t o a smaller extent. Thus a 0.005% benzalkonium chlor ide solution r a i s e s the ef f lux of glucose t o 430%, whereas

~ --. l a c t a t e appeared t o be raised by a f ac to r of 3.1

CHANGE I N METABOLITE CONCENTRATION OF TEARS AFTER SHORT-TERM WEARING OF CONTACT LENSES I N NONADAPTED EYES H . Kilp, C . Thode and B. Heisig-Salentin Cologne University Eye Hospital, Cologne, West Germany

In nonadapted eyes the influence of hard contact lenses on the an ter ior region can be c l i n i c a l l y demonstrated biomicroscopically only in more

pronounced damage. I t can be shown in animal t r i a l s t ha t physical and chemical i r r i t a t i o n s of the an ter ior region of the eye can markedly a l t e r t he permeability of the corneal epithelium for

glucose. We were prompted by these r e s u l t s t o determine the metabolite concentrations of glucose, pyruvate and l a c t a t e in the t e a r f l u id of humans with nasal co l lec t ion of the t ea r f l u i d . In t h i s way i t would be possible t o demonstrate metabolites permeated from the corneal epithelium.

pyruvate did no t show any s ign i f i can t d i f fe rences between temporal co l lec t ion and nasal co l lec t ion of t he t e a r f l u i d . Only the l a c t a t e concentration was s l i g h t l y ra i sed . r e su l t s of f lushing experiments in rabbi t s in which only l a c t a t e can be flushed in la rge amounts

from the surface of the cornea.

The concentration of glucose, l a c t a t e and

This co r re l a t e s with the

With mild UV i r r a d i a t i o n the animal t r i a l showed

a r i s e of the permeability to glucose of 260%, t o l a c t a t e of 340%, and t o pyruvate of 470%. Chemical i r r i t a t i o n s which do not primarily involve the ce l l membrane b u t p r e fe ren t i a l ly in t e r f e re with i n t e r c e l l u l a r contac ts (e.g.

and pyruvate by a f a c t o r of 1.5. With complete abrasion of the corneal e p i t h e l i -

um, inves t iga t ions in humans reveal a 230% r i s e of glucose i n the t e a r f l u i d , whereas the concentra-

t i o n of pyruvate and l a c t a t e are only s l i g h t l y below the normal content. Superficial erosions of the epi the1 i urn ra i sed the glucose content t o about 120%, whereas the l a c t a t e concentration r i s e s t o 145%. Comparable measurements a f t e r wearing hard contact lenses f o r two hours reveal a r i s e o f t he glucose concentration in t h e t e a r f l u i d by 70%, whereas the pyruvate and l a c t a t e l eve l s are only ra i sed by 20%.

These r e s u l t s show tha t mechanical trauma in nonadapted eyes can e l i c i t a l t e r a t i o n s which a r e markedly grea te r than in a supe r f i c i a l erosion of the corneal epithelium. Since glucose i s mainly raised not as an i n t r a c e l l u l a r , b u t also as an i n t e r c e l l u l a r metabolite, a preferen t ia l damage of t h e i n t e r c e l l u l a r l i nks i s t o be assumed. These r e s u l t s can be amplified, as shown by animal experiments, by simultaneous application of preservatives tha t are added t o the so lu t ions f o r care of contact lenses , Further inves t iga t ions are required t o show the extent t o which the eye adapts t o the mechanical in te r fe rence . However, these r e s u l t s show tha t caution i s called fo r in t h e adaptation of lenses when p r io r damage t o the epithelium i s already present.

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