 |
Looking into Contact Lenses |
|
|
|
 |
What
are contact lenses?
Increasing numbers of people are considering contact lenses
as an alternative to spectacles, not only because they
are virtually invisible in the eye, but they also are
much safer for active sports. |
Contact lenses are incredibly thin 'saucers' of transparent
material that fit snugly in the eye. All the main types of contact
lenses are fitted at our Rochford practice. The main categories
of lenses in use today are:
- soft lenses... when wet, they can be folded literally
in half without damage! They absorb water that can form
up to 75% of their volume so they are very easy on the eye.
Originally soft lenses were only suitable for simple prescriptions.
Nowadays we regularly fit sophisticated designs that can
cope with bifocal or astigmatic (toric)
prescriptions.
- gas permeable lenses... cover most of the cornea (the
coloured part of the eye) and float on a fine layer of tears.
There are an enormous range of different g.p. materials
- some are more durable, some allow the eye to breathe more
easily whilst others feature high 'wettability' by the tear
film. There are also many different lens geometries available
from the various laboratories. Patients' clinical needs
differ so we have a variety of fitting sets at the practice
(we are not tied to any particular laboratory for supply)
to ensure that the most appropriate choice can be made for
each fitting.
Photograph courtesy of Bausch & Lomb |
Checking
the fit of a gas permeable lens by using a dye to makes
the tear film below the lens fluoresce. |
What lens packages are available?
Disposable Lenses
(These are daily wear lenses and not extended wear i.e.
they are not kept in the eyes overnight). Current soft lens
materials are very comfortable but, as they get older, attract
grease from eyelids and deposits from the tear-film. More
time and money must then be spent in cleaning them to preserve
comfort. Such lenses have, in the past, led to allergic
reaction problems. For the past few years optometrists have
been using a system pioneered in Scandinavia that is better
suited to today's hectic lifestyle. Lenses are replaced
at planned regular intervals, so less money is spent on
cleaning and maintenance systems. Clean fresh lenses throughout
the year mean that vision always remains good and the eyes
remain clear and, most important, healthy. Ongoing costs,
which can be spread with standing order payments, are surprisingly
modest. The comfort and easy care of these systems is so
good that it is safe to predict that almost all soft lenses
will be supplied this way by the turn of the century. Replacement
lens frequency can be monthly, or quarterly to half- yearly
- the optimum time period governed by which soft lens material
best suits a particular patient's eyes.
1 Day Lenses
 |
These
are a particular type of disposable lens offering
the ultimate in hassle-free wear. These lenses are
worn for a day then thrown away. Cleaning routines
are eliminated and the insertion of a fresh sterile
lens ensures the optimum in vision and comfort.
This type of lens is proving especially popular for
those who wish to use lenses intermittently, for social
wear several times a week or for sport. Not all prescriptions
are suitable although the range is being extended
all the time. |
I need bifocals so will I be able to use lenses?
Bifocal wearers have a number of options:
- The simplest solution is to use contact lenses to
correct for distance and to wear a mild pair of reading
spectacles on top when required. This gives excellent
vision, although it does not totally eliminate the need
for spectacles.
- Bifocal rigid lenses (usually gas permeable material).
These can offer a very good standard of vision. They
may rely on the lower lid "steering" the reading
portion into position when you look down, or they may
be a "diffractive" design which gives both
near and far focus at the same time.
- Multifocal soft lenses give clear vision throughout
the range, but may not give the absolute crisp clarity
of a rigid bifocal design. We specialise in lenses of
this type for disposable use, from Bausch & Lomb
(Occasions) and Johnson & Johnson.
- Monovision correction sometimes works very well. One
eye is corrected with a bias for distance and the other
biassed for near, sometimes with a multifocal lens.
-
Specialised Fittings
Most people will be suited by one of the standard lens designs.
In a borderline case a standard design may be tried to cut
down costs, going to the more complex type only if the first
fitting is unsuccessful. Where large degrees of astigmatism
are involved, either gas permeable or Toric
Soft Lenses may be required.
-
The Old and the New
PMMA lenses, the original "hard" lens design are
occasionally used but, as they have no benefits over GP
lenses, they are usually offered only to existing PMMA wearers.
Where applicable, advice and recommendations are offered
on the new polymers materials and lens designs currently
being introduced. Cosmetic-tinted and iris-pattern soft
lenses are also available.
-
Extended Wear Soft Lenses
These have been available for a number of years. Many opticians
feel that clinical evidence does not prove them to be sufficiently
safe enough to recommend unreservedly to patients. However
there are certain clinical instances where their benefits
outweigh potential disadvantages. The latest generation
of these lenses are sometimes supplied for continuous wear
with a two-weekly replacement cycle.
|
|
|
|
 |
