A look at the basics about three of the most common conditions
By: JENEAN CARLTON, ABOC, NCLC
Eyecare Business January 1, 2015
BACK TO BASICS
Common Ocular DISEASES
A look at the basics about three of the most common conditions
BY JENEAN CARLTON, ABOC, NCLC
It’s not uncommon for patients to leave the exam room and begin speaking with opticians and staff members about their vision problems. Because of this, having a basic knowledge about common ocular diseases, as well as the structures of the eye, will increase the entire staff’s level of professionalism.
This article offers a look at three common eye problems: subconjunctival hemorrhage, corneal abrasions, and cataracts.
SUBCONJUNCTIVAL HEMORRHAGE
Also called red eye, this occurs when a small blood vessel ruptures underneath the conjunctiva—the clear membrane that lines the cornea and sclera as well as the inner surface of the eyelids.
What
Subconjunctival hemorrhage often occurs with no warning. Patients frequently wake up and don’t even realize there is a problem until they look in a mirror.
Because it makes the eye bright red, one might expect to experience pain. A subconjunctival hemorrhage is usually harmless, rarely painful, and will heal within one to two weeks.
Why
Why does the eye look so red? A subconjunctival hemorrhage occurs because a small blood vessel under the conjunctiva has leaked a tiny amount of blood. The blood is trapped underneath the conjunctiva, which doesn’t absorb blood quickly. Because the conjunctiva fits tightly over the sclera, a single droplet of blood spreads between the two layers of tissue, making it look like large amount of blood has seeped out of a vessel (see sidebar on below).
RED EYE ANALOGY
A good analogy to help describe a subconjunctival hemorrhage to patients is the experiment where a drop of water is placed between two flat plates of glass. The glass plates fit so snuggly together that the water is dispersed over a large area and appears to be a much higher volume than just one droplet of water. The same is true of blood in the case of red eye.
The condition might occur after vomiting, coughing, sneezing hard, or a migraine headache, and activities like scuba diving or experiencing a hit to the head.
Treatment
There is no specific treatment for a subconjunctival hemorrhage other than checking the patient’s visual acuity and waiting for the blood to clear.
CORNEAL ABRASION
Patients with a corneal abrasion typically present with complaints of pain, excessive tearing, blurry vision, photophobia, and a foreign body sensation.
What
Corneal abrasions can be superficial or deep scratches/lacerations on the cornea. Abrasions deeper than the epithelium and Bowman’s membrane may result in permanent scaring, depending on the depth of the laceration.
Why
Common causes of corneal abrasions are fingernails, damaged or torn contact lenses, cat scratches, paper cuts, or a foreign body trapped underneath the eyelid.
The cornea is made up of five layers of tissue—the epithelium, Bowman’s membrane, stroma, Descemet’s membrane, and endothelium—with the overall thickness of the cornea being compared to the thickness of a credit card. (See sidebar below.)
Subconjunctival hemorrhage image by Trey Sullins, O.D.
Mild central corneal abrasion image by Viktoria Davis, courtesy of EyeAtlas.org
5 LAYERS
The cornea has five layers. They are:
1THE EPITHELIUM is the outermost layer of the cornea. The first line of defense and protection for the cornea, it accounts for 10% of overall corneal thickness. It is also the only layer able to regenerate itself.
2BOWMAN’S MEMBRANE is the second layer of the cornea and is somewhat like cellophane. It is resistant to injury and infection, and if injured, a scar will form.
3THE STROMA, the third layer, is made of collagen fibers and is responsible for 90% of corneal thickness. In corneal edema, it is the stroma that is swollen.
4DESCEMET’S MEMBRANE is the fourth layer and lies between the stroma and endothelium.
5ENDOTHELIUM is the fifth and innermost layer. It is a single cell layer and is important because it acts as a tear pump, maintaining the tear film balance on the cornea. Abrasions deeper than the epithelium and Bowman’s membrane will result in permanent scarring. What’s the big deal about scars? The damaged area of the cornea is likely to heal in an irregular way, resulting in poor visual acuity through that area of the cornea.
Treatment
Doctors may use pressure patches and topical antibiotic medications to treat corneal abrasions, most of which usually heal within 24 to 48 hours.
CATARACT
Cataract is the leading cause of blindness in the world. According to the World Health Organization, it is responsible for 51% of blindness worldwide. Though most cases are associated with aging, infants can be born with the condition. Many factors can contribute to cataract development besides aging—UV wavelength exposure, blue light wavelength exposure, smoking, diabetes, hypertension, and long-term usage of corticosteroid medications.
What
A cataract is a clouding of the crystalline lens, the natural lens inside the eye. With some 16 diopters of power, it’s the second most powerful structure of the eye, surpassed only by the cornea, which has about 45 diopters of power.
The primary function of the crystalline lens is to focus light onto the retina. It achieves this by changing shape so that objects at various distances come to a focus on the macula, the central region of the retina that contains photoreceptive cells.
Cortical cataract image by Walt Mayo, O.D., courtesy of EyeAtlas.org
STEP BY STEP
Cataract surgery is an outpatient procedure. Before surgery begins, patients are given medication to help them relax. Clamps are used to spread the eyelids and keep them immobilized. Next, a colored stain is injected into the anterior chamber to tint the outer skin-like layer, called the capsule. A clear jelly is injected to displace the stain and the capsule is removed.
Modern cataract surgery employs phacoemulsification, an ultrasonic tool that liquefies the cataract, and then uses suction to remove the debris. Then, an incision of about 3mm is made to insert the intraocular lens (IOL), which looks like a soft contact lens with two nylon cords attached. IOLs are custom-ordered to a patient’s prescription. They are pliable and fold for insertion through the incision.
Once the IOL is inserted into the anterior chamber, it unfolds immediately and snaps into place. The two nylon cords attached to the IOL keep it in position. A balanced salt solution is then used to inflate the chamber to a normal pressure.
If you’re interested in seeing the procedure, check out a video posted on YouTube by Mark Sibley, M.D., with the Florida Eye Center in St. Petersburg, FL, at http://bit.ly/1zWJmnw
Accommodation is the automatic adjustment of the crystalline lens to provide vision at different distances. When viewing objects up close, the crystalline lens becomes more convex. This change results in a more plus-powered lens that enables us to see objects clearly at near. When viewing at a distance, the lens becomes more concave in shape, resulting in a more minus-powered lens.
Why
What makes the crystalline lens cloudy? It is primarily made of water and protein. In a normal lens the proteins are dissolved in the lens cells and are arranged to let light through to the retina. Cataracts form when the protein inside the lens crystallizes and clumps together. This causes light to scatter in the eye rather than coming to a sharp focus on the retina.
Treatment
In the early stages of a cataract, patients may complain that their vision isn’t as clear as it used to be, that colors aren’t as saturated as they normally are, and that night driving is problematic. Streetlights or car lights may appear to be too bright or even seem to have halos around them.
When vision deteriorates to a point that it interferes with daily activities, cataract surgery may be advised. Performed on an outpatient basis, it is the most common surgery in the U.S. It involves surgical removal of the crystalline lens and insertion of an intraocular (IOL) plastic lens. The IOL replaces the crystalline lens and the power of the IOL may be ordered to correct refractive errors, most often for distance correction. Even presbyopia-correcting IOLs are available so patients can see well up close as well as at a distance. The ultimate decision regarding the power and type of IOL to be inserted is made by the physician.
Having an understanding of common ocular diseases and disorders will help your career and allow for improved communications with physicians, patients, and other staff members.
Common Ocular Diseases
JENEAN CARLTON, ABOC, NCLC
Understanding common ocular diseases and disorders will help you as an optical professional. This puzzle includes terms that relate to ocular diseases and disorders. See the February issue of Eyecare Business to check your answers.
Across
6. Subconjunctival hemorrhage often occurs with no _____.
8. A subconjunctival hemorrhage occurs because a small blood vessel under the _____ has leaked a tiny amount of blood.
10. The macula is the central region of the retina and contains _____ cells.
11. The _____ is the fifth layer of cornea and is the innermost layer.
14. _____ is the automatic adjustment of the crystalline lens to provide vision at different distances.
16. It’s not uncommon for patients to leave the _____ room and begin speaking with opticians and staff members about their vision problems.
18. Cataract surgery is performed on an _____ basis and is the most common surgery in the United States.
19. The _____ is the third layer of the cornea and is responsible for 90% of the corneal thickness.
20. The crystalline lens is primarily made of water and _____.
21. The IOL is inserted into the _____ _____. (2 words)
22. Modern cataract surgery employs _____, an ultrasonic tool that liquefies the cataract and then uses suction to remove the debris
23. _____ is the leading cause of blindness in the world
24. Abrasions deeper than _____ _____ will result in permanent scarring. (2 words)
25. The endothelium is important because it acts as a _____ _____, keeping the tear film balance on the cornea. (2 words)
Down
1. The two _____ _____ attached to the IOL keep it in position. (2 words)
2. The _____ is the outermost layer of the cornea.
3. Cataracts form when the protein inside the lens _____ and clumps together.
4. A _____ _____ or “red eye” occurs when a small blood vessel underneath the conjunctiva ruptures. (2 words)
5. The cornea is made up of _____ layers of tissue.
7. The crystalline lens is the second most _____ structure of the eye with approximately 16 diopters of power.
9. The cornea’s fourth layer of the cornea is _____ _____. (2 words)
12. Cataract surgery is the surgical removal of the crystallinelens and insertion of an _____ plastic lens.
13. A subconjunctival hemorrhage is rarely _____.
15. Corneal abrasions can be _____ or deep scratches/lacerations on the cornea.
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