Eye Health

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.

  Tech Corner

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 corneal surgery.

  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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