Lens movement is important to keep a healthy tear exchange and overall good health of the eye.
Do not memorize the types of movements and how to adjust it. Rather try to visualize what is happening between the lens and the cornea and try to understand why the lens is moving the way it does.
NEW LENS WEARER #
With a new rigid lens patient, the movement can be very misleading. The tear film will be abnormal, both in volume and viscosity, as reflex tearing in response to a foreign body overlays the normal background tear secretion.1 A tense patient is also likely to have tighter lids than usual.
ESTABLISHED LENS WEARER #
On the established wearer, the way the lens moves, and centers is particularly important and a more realistic indication of the fit.
PATIENT POSTURE FOR EVALUATION #
Positioning of your patient’s eye is critical to evaluating lens movement. When using a slit lamp, most patients sit with their chin slightly up, which is an unnatural position. This position changes the gravity on the lens as well as the lid interaction, resulting in most lenses dropping down on the eye. Adding a bright light, brand new lens, lots of reflex tearing and bad posture, and evaluating the movement becomes almost impossible. Thus, it is very important for the patient to settle down with the lens before any evaluation can take place. Using a handheld lamp is also preferred, as it will normalize the posture for the patient.
LENS MOVEMENT #
Ideal movement is a lens following the lid slightly upwards with the blink and then slowly glide into its final resting position. The goal is a slight (2mm) unobstructed movement in the vertical meridian (up and down) while not moving horizontally (side to side).2
Excessive movement will produce poor vision with compromised comfort.
No movement might feel good for the patient, but removing the lens will be problematic and overall eye health will be compromised.
- Franklin A and Franklin N. Basic Contact Lens Course- Part 9: Assessing the fit of RGP lenses. Optician 2010.9:25-30
- Laäs C, Eksteen C, Booysen D. The art of contact lens fitting. 2005:23-26
