Tag: Cornea

Categories
Treatments

Eye Patches After Surgery

Patching the eye after surgery is a matter of routine.  The eye patch is usually worn only overnight and then removed for the rest of the post-operative period.  It can offer protection, reduce discomfort, but really has no “healing” attributes.

The Lid Should be Closed Against the Eye

A properly placed eye patch, for any reason, should be a “pressure patch,” meaning that the taped patch should exert enough pressure on the eye to keep the lid closed.  This also ensures that the eye can not rub against the patch itself.

Pain Reduced

Whatever “discomfort” (doctor language for pain) there might be after the operation is decreased by blocking light.  While the eye is still able to move underneath the closed lid, there is some additional comfort created by decreased blinking.

The cornea is a very sensitive tissue.  Small abrasions can cause great sensitivity to light.  Corneal abrasions, even those unrelated to surgery, usually heal rapidly, with or without patching.

Protection?

The eye is dirty, so there is no protective effect from the patch, unlike, say, a true bandage.  Remember that the eye, nose and mouth are all connected.

In the old days, when cataract surgery required a “large” incision to be made into the eye, a shield was placed on top of the patch.  This shield would offer physical protection until the incision healed and became stronger.

Special Situations

There are a few special situations where patching is important after eye surgery.  Occasionally the surgical wounds are not tightly sealed (i.e. the eye is leaking) and an additional day or two of patching is required.  If patching doesn’t suffice, then a short trip back to the operating room might be warranted.

What Does This Mean? As surgical techniques have advanced, there is less tissue damage from surgery, that is, there is less cutting that causes trauma to the eye.  Hence, there is really little discomfort after surgery.

Many cataract surgeons often have the patch removed later in the day so post-operative eye drops can be started right away.  I’ve even heard of a few surgeons that forget the patch all together.

I still prefer to patch.  I find it very useful to help limit swelling after placing a scleral buckle for retinal detachment, but I don’t find it mandatory for the reasons above.

An eye patch does serve as a reminder that an operation was performed and, I believe, are expected.

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Categories
Macular Degeneration

Never Enough of a Dry Eye

Intermittent blurry vision from dry eye is common, and although ultimately a corneal problem, is a condition often faced by a retina specialist.   Many times, patients with retinal disease, such as diabetic retinopathy or macular degeneration,  are referred to me with unexplained, fluctuating,  decreased vision.  It is always up to me to figure out if the change in vision is due to the dry eye, or the retinal disease.

The cornea is the transparent tissue in the front of the eye.  It is the tissue covered by a contact lens.  The cornea is responsible for about 2/3 of the focusing power of the eye.  Not even our natural lens, which rests inside the eye, has this much focusing power.

Tear Film – When we blink, the eyelids spread tears across the surface of the eye.  The tears keep the cornea hydrated.   A well-hydrated cornea has a very uniform and smooth surface.  The air-water interface, where the air hits the watery tears on the cornea, gives the cornea so much focusing power.

(Actually, it is the radius of curvature of the cornea and the index of refraction of the  air-water interface that yields the final focusing power of the eye.  This is also why laser vision correction works; it changes the radius of curvature, or roundness, of the cornea.)

In dry eye conditions, the surface of the cornea becomes, uh…dry.  On a microscopic level, it is no longer smooth.  A “dry” cornea is irregular and rough.  It does not focus light accurately or consistently as the tear film is some what patchy.  The result is a very blurry image that reaches the retina.  We complain of blurry vision.

Treatment for dry eye usually consists of artificial tears and lubricants.  Other treatments are available, but are beyond my scope of practice.  It is important to remember, yet hard to implement, that the use of artificial tears should be regular and not used only when symptoms develop.  The idea is to prevent dry eye from developing.

Symptoms of dry eye include blurry vision, burning, sensitivity to light and tearing.  The blurry vision may only be at certain times of the day, during certain activities, such as reading, or may be more prevalent at certain seasons (winter is generally drier along the East coast).  The cornea is a highly sensitive tissue, the dryness causes the burning and sensitivity (try not blinking for 30 seconds).  The tearing develops in response to the burning (as if to wash something away).

What Does This Mean? Due to the enormous focusing power of the cornea, any small perturbation of the corneal surface can translate into rather dramatic change in vision.  To a patient with retinal disease,  these changes in vision are worrisome, scary and can be depressing.  A key difference, however, between loss of vision from dry eye versus progressing retinal disease is that the symptoms from retinal disease should not fluctuate, especially on a daily basis.

I am always happy to “blame” the dry cornea for changes in vision and we all breathe a sigh of relief when I find the retinal  disease is stable and unchanged.

It really should be called “dry cornea.”

“Randy”

Randall V. Wong, M.D.

Ophthalmologist, Retina Specialist
Fairfax Virginia

Categories
“Other” Eye Conditions

The Cornea and How We See

The cornea is the clear tissue at the front of the eye.  A contact lens rests on the cornea.  It is normally crystal clear, focuses light and permits light to be focused on to the retina.  A healthy retina absorbs light, transmits this information to our brain……..and voila………it gives us vision.

The Cornea  and Focusing Power of the Eye The cornea is more than just a clear window to the inside of the eye.  The cornea is actually responsible for about 70% of the focusing power of the eye!  For those that remember physics, the combination of the air/water interface along with a specific radius of curvature……………..

Anyway, this is why laser vision correction works so well.  By reshaping the surface of the cornea, the focusing strength of the cornea can be calibrated to refocus light onto the retinal surface.  No more need for glasses!

Ever have a scratch on your cornea?  It hurts and can cause significant loss of vision.  Why?  The surface of the cornea is usually smooth, but when scratched this critical focusing surface is now rough and uneven, resulting in significant loss of vision.  With patching, the surface usually can heal quickly with full restoration of vision.

The natural lens inside the eye also contributes a small portion to the overall focusing power of the eye, but remember most is due to the cornea.

Nearsighted vs. Farsighted Nearsighted individuals have a natural focusing point in front of the retinal surface.  Glasses/contact lenses are used to push the focusing point back to the retinal surface.  Nearsighted (not nearsightless) individuals can take their glasses off and read without glasses.

Farsighted individuals have their focusing point in back of the retinal surface.  Glasses are required to bring this focusing point forward to the retinal surface.

Measuring Your Visual Acuity of 20/20 occurs when a focused image is on the surface of the retina and the retina is healthy.  A healthy retina is required to transmit all of the focused light to the brain.

In cases of macular degeneration and diabetic retinopathy, if the disease has caused some damage to the macula, perfect vision is not possible simply because the retina is not functioning completely.

Corneal Disease is usually unassociated with diabetic retinopathy and macular degeneration, that is, there are usually no related corneal findings in these two retinal diseases.  There is a slight chance of spontaneous abrasions, but no true disease.

“Randy”

Randall V. Wong, M.D.
Ophthalmologist, Retina Specialist
Fairfax, Virginia

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