Article Date: 1/1/2004

orthokeratology today
When the Ortho-k Magic Stops
BY JOHN MOUNTFORD, DIP, APP, SC, FAAO, FCLSA

We've all had that previously successful ortho-k patient who presents with the complaint that his lenses "aren't working as well as before." The symptoms usually consist of discomfort, loss of the  ortho-k effect or simply blurred vision. Resolving the discomfort portion of this claim is usually the easiest, so I'll focus on resolving loss of the effect.

Decreased Effect = Discomfort

If you see the patient in the morning with the lenses in situ, you may immediately note fine (grade 1) corneal staining centrally that wasn't present at previous aftercare visits. This is almost universally associated with back surface deposits.

The patient will report a gradual decrease in the ortho-k effect of the lenses associated with an increase in discomfort. Gently drying the lens with a tissue reveals a grainy central deposit that may prove resistant to removal by lens polishing because the rotation speed of the polishing dome is close to zero centrally.

Losing the Effect

Loss of the ortho-k effect can occur either gradually or suddenly. Causes of gradual loss include:

Lenses that do not initially provide an ideal bull's eye response with a small degree of either superior or lateral decentration will always get worse over time and have an adverse impact on lens efficacy. Sometimes a BCR that has flattened with time causes creeping decentration.

The following can cause rapid loss of the effect:

Unfortunately, you can't measure these curves and what then follows is a frustrating lens exchange game until another "identical" lens arrives that works. On the positive side, you can cheaply and accurately check RGLs.

Coming Up...

My next article will deal with strategies for controlling vertical and lateral decentration as well as with checking reverse geometry contact lenses.

Dr. Mountford is an optometrist in private practice specializing in advanced contact lenses for keratoconus, post refractive surgery and pediatric aphakia. He is a visiting contact lens lecturer to QUT and UNSW, Australia.

 


Contact Lens Spectrum, Issue: January 2004