In last month's iSight we described the importance of maintaining a healthy oily layer on the tear film of the eye.
Another component of a healthy tear film is the aqueous (watery) layer. The aqueous layer is produced by the
lacrimal glands (located under the outer corners of your brow bones). Lacrimal gland tear secretion can be
stimulated by emotions (crying) or irritants (chopping onions) but the glands also produce a continuous small
amount of tear that keeps the eye surface clean with each blink. This small continuous flow is known as the basal
secretion. If the basal secretion is low, the eyes are dry. To find out if your aqueous layer is deficient, we can
perform a Shirmer Test, a simple, painless test that takes just five minutes. There are 3 ways to help the basal
secretion: the tear can be kept on the eye longer by insertion of tiny 'punctal plugs' in the tear drainage channel
(the punctum), much like putting a plug in a bathtub. These plugs are easily inserted and are removable. Second,
the tear film can be supplemented by applying artificial tears. Several different types are available, and we
recommend using preservative-free formulations if frequent dosing is necessary. Third, the underlying cause of the
lacrimal gland deficiency can be addressed. Although the cause is frequently unknown, in some instances it can be
due to chronic inflammatory conditions. Prescription medications (such as Restasis) can help control underlying
inflammation in some cases.
What's new in vision correction procedures
Patients with thin and irregular corneas due to certain conditions, like keratoconus, for example, can benefit from
improved vision with a procedure called Intacs. Intacs are ultra-thin microscopic strips of material that are placed
within the cornea to help support it and make the surface more even and symmetric. Vision improves, allowing
most patients to get into comfortably fitting soft contact lenses, glasses, and, in some patients, even see better
without glasses or contact lenses. Intacs is a 10-minute in office procedure and works well for patients with
keratoconus and other corneal thinning conditions.
The IntraLase laser, which is used in LASIK eye surgery at Pacific Vision Institute, has a new role in corneal
transplant surgery. The laser can be used to create a precise graft that fits perfectly on the recipient's eye. This
results in far less astigmatism in the post-operative period, and thus faster visual recovery. The laser can also be
used in transplantation of layers of cornea (i.e. lamellar keratoplasty) for certain corneal diseases that require only
replacement of one layer of tissue. The remarkable precision of the IntraLase is rapidly revolutionizing the world of
Fun Eye Facts
Even wondered how some animals see so well in the dark? Animals' eyes have a number of special features
designed for night vision. For example, snakes eyes can detect infrared light which helps them hunt for warm
blooded prey . Dogs and cats have a tapetum lucidum (meaning "bright carpet"), a reflective membrane beneath
the retina that collects and re-emits light back to the retina, giving the rod cells a second chance to absorb the
image information. Other nocturnal animals have very large eyes with wide pupils to collect more light. Some of
these large eyes don't move within their sockets but to compensate, some animals rotate their necks 270 degrees (owls)
or have eyes that are designed for very wide fields of vision with spherical lenses and widened corneas.
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