Visual Disorders

Visual Disorders By: Bryan Mae H. Degorio

Corrective Refractive Disorders Astigmatism -characterized by an irregular curvature of the cornea. This type of disorder is also known as a refractive error. -is a common eye condition that's easily corrected by eyeglasses, contact lenses or surgery.

Causes: 1. Astigmatism can be hereditary and is often present at birth. 2. It can also result from pressure from the eyelids on the cornea, incorrect posture or an increased use of the eyes for close work. 3. It may accompany farsightedness or nearsightedness. 4. Usually it is caused by an irregularly shaped cornea (called corneal astigmatism). 5. But sometimes it is the result of an irregularly shaped lens, which is located behind the cornea; this is called lenticular astigmatism.

Signs and Symptoms: 1. People with undetected astigmatism often experience headaches, fatigue, eyestrain and blurred vision at all distances. 2. While these symptoms may not necessarily be the result of astigmatism, you should schedule an eye exam if you are experiencing one or more symptoms.

Treatment: 1. Almost all degrees of astigmatism can be corrected with properly prescribed eyeglasses or contact lenses. a. Corrective lenses (eyeglasses or contact lenses). - For astigmatism, special corrective lenses called toric lenses are prescribed. Toric lenses have greater light bending power in one direction than the other.

b. Refractive surgery. - Another method for correcting astigmatism is by changing the shape of the cornea through refractive or laser eye surgery. -Refractive surgeries require healthy eyes that are free from retinal problems, corneal scars and any eye disease.

Hyperopia -Farsightedness -parallel rays of light focus behind the retina -corrected with convex lens Miopia -nearsightedness -parallel rays of light is focus in front of the retina -corrected with concave lens - Radial Keratotomy(RK Surgery)

Presbyopia -”old sight” -lessening of the effective powers of accommodation as a result of hardening of the lens due to aging process -Blurring of the near objects or visual fatigue when doing close eye work -convex reading glasses is recommended

Extraoccular Disorders Hordeulom -pustular infection of the of the eyelash follicles or sebaceous gland on an eyelid margin -there is painful red swelling on eyelid margin -commonly associated with staphylococcus

Chalazion -internal eye -inflammation of the meibomian gland -painless, slow-growing, hard non-tender rpund mass in the eyelid Conjunctivitis -inflammation which results from bacterial infection and viral infection -characterized by redness, swelling, lacrimation, pain, itching and dischrges from the eyes

Strabismus (squint, tropia, heterotropia) 1. Eye deviation a. esotropia- inward convergent deviation of the eye b. exotropia- outward/divergent deviation from eyes c. hypertropia- upward deviation of the eyes d. hypotropia- downward deviation of the eyes

1. Management: a. corrective eyeglasses b. Surgery: -advancement, resection and tucking -tenotomy recession Keratitis - corneal inflammation that might lead to corneal ulceration -Assessment: a. Pain b. photopobia

c. lacrimation d. blepharospam e. decreased vission -treatment: 1. Trifulridine, idoxuridine 2. mechanical and chemical debridement Corneal Ulceration -is a medical emergency that may lead to corneal perforation, scarring and intraoccular infection and permanent vission loss.

Causes: -trauma, exposure to allergy, vitamin deficiency, lowered resistance and infection Corneal Opacity -lack of corneal transparency due to inflammation, ulceration or injury

Intraoccular Disorders Cataract -A cataract is a clouding of the eye's natural lens, which lies behind the iris and the pupil leading to blurry of vision, and eventual loss on sight

Causes: 1. degenerative changes in the eye protein 2. ultraviolet exposure 3. injury and intraocular infection 4. presence of other disease such as DM Manifestations: 1. You may notice that your vision is blurred a little, like looking through a cloudy piece of glass or viewing an impressionist painting. 2. light from the sun or a lamp seem too bright or glaring.

Classification of Cataract:  nuclear cataract (senile) - This cataract forms in the nucleus, the center of the lens, and is due to natural aging changes.  cortical cataract - which forms in the lens cortex, gradually extends its spokes from the outside of the lens to the center - Many diabetics develop cortical cataracts.  subcapsular cataract - begins at the back of the lens. -People with diabetes, high farsightedness, retinitpigmentosa or those taking high doses of steroids may develop a subcapsular cataract.

Management: 2. Intracapsular technique -removal of cataractwithn its capsule 2. Extracapsular technique -an opening is made in the capsule and the lens is lifted without disturbing the membrane 3. Cryoextraction -the cataracts lifted from the eye by a small probe that has been cooled to a temperature below zero and edheres to the wet surface of the cataract

4. Iredectomy -is done proceeding cataract extraction to create an opening for the flow of the aqueous humor which may become blocked postop. 5. Phacoembolism -a method of cataract extraction which breaks up the lens and fluhes it out into tiny pieces 6. Intraocular lens implantation - implanted in the eye in place of the patient's clouded natural lens. - the lens material is yellow because it filters out blue light, which may be harmful to eyes.

Post-op Care: l Cover the with a dressing to prevent injury l Patient is allowed to be out of bed the day following surgery l Daily change of dressing is done and after 7 days all dressings are usually removed l 1st month-protect the eye with eye shield during night l Note: temporary glasses may be prescribed 14 weeks. Permanent glasses or contact lens is given after 6-12 weeks if healing is already sufficient

5. Cataract glasses magnify so that everything appear one fourth closer than it is. It takes time to judge distance.

Glaucoma - is an eye condition that develops when too much fluid pressure builds up inside of the eye -eye disorders often associated with a dangerous build up of internal eye pressure ( intraocular pressure or IOP), which can damage the eye's optic nerve that transmits visual information to the brain.

Types of Glaucoma:

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Open-angle glaucoma. -Also called wide-angle glaucoma, this is the most common type of glaucoma. -The structures of the eye appear normal, but fluid in the eye does not flow properly through the drain of the eye, called the trabecular meshwork.

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Angle-closure glaucoma. -Also called acute or chronic angleclosure or narrow-angle glaucoma, this type of glaucoma is less common, but can cause a sudden buildup of pressure in the eye. -Drainage may be poor because the angle between the iris and the cornea (where a drainage channel for the eye is located) is too narrow. Or, the pupil opens too wide, narrowing the angle and blocking the flow of the fluid through that channel.

Causes:  Glaucoma most often occurs in adults over age 40, but it can also occur in young adults, children, and even infants. In African-Americans, glaucoma occurs more frequently and at an earlier age and with greater loss of vision.  Are of African-American, Irish, Russian, Japanese, Hispanic, Inuit, or Scandinavian descent.  Have a family history of glaucoma.  Have poor vision.  Have diabetes.  Take systemic corticosteroid medications, such as prednisone

Manifestations:  Seeing

halos around lights  Narrowing of vision (tunnel vision)  Vision loss  Redness in the eye  Eye that looks hazy  Nausea or vomiting  Pain in the eye

Diagnostic Procedure:

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Tonometry - to check for eye pressure Visual field test -to determine if there is loss of peripheral vision.

Management: Glaucoma treatment may include prescription eye drops, laser, or microsurgery.  Eye drops for glaucoma. These either reduce the formation of fluid in the front of the eye or increase its outflow. a. Miotics-used to constrict the pupil and to draw the smooth muscle of the iris away from the canal of schlemm permiting the acqueous humur to drain out

b. Acetazolamide -tend to reduce the formation of aqueous humor and commonly use for chronic glaucoma -glycerol-osmotic drugs that reduce the intraoccular pressure c. Avoid the Atropine and Mydriatrics -these drugs are use to dilate the pupil -the iris are brought closer to the angle of outflow

 Laser

surgery for glaucoma -Laser surgery for glaucoma slightly increases the outflow of the fluid from the eye in open-angle glaucoma or eliminates fluid blockage in angle-closure glaucoma. -Types of laser a. Trabeculoplasty- laser is used to pull open the trabecular meshwork drainage area b. Iridotomy- in which a tiny hole is made in the iris, allowing the fluid to flow more freely c. cyclophotocoagulation- a laser beam treats areas of the ciliary body, reducing the production of fluid.

 Microsurgery for

glaucoma a. Trabeculectomy -a new channel is created to drain the fluid, thereby reducing intraocular pressure that causes glaucoma.

Retinal Detachment -is a very serious condition that occurs when the retina pulls away from its supporting tissues. -the retina can't work properly under these conditions, permanent vision loss may occur if a detachment is not repaired within 24 to 72 hours

Causes:  Nearsighted

adults  People who have had an eye injury or postcataract extraction surgery  People with a family history of retinal detachment .

MANIFESTATIONS:  Flashes

of light -the light that enters is not absorbed by the detached melanin epithelial pigment  Showering effect of floaters (small flecks or threads) in the visual field. - These are blood and retinal cell thatare freed at the time of the tear and cast shadows on the retina as they seem to rift about the eye  Darkening of the peripheral visual field.

 Progressive

constriction of vision in one area -when detached is extensive and occur quickly , there is sensation that a curtain has been drawn before the eyes as if looking gin a fence

MANAGEMANT:  Laser (thermal) or freezing (cryopexy). -Both of these approaches can repair a detached retina if it is diagnosed early enough.  Pneumatic retinopexy. -This procedure can be used to treat retinal detachment if the tear is small and easy to close. A small gas bubble is injected into the vitreous where it then rises and presses against the retina, closing the tear. A laser or cryopexy can then be used to seal the tear. This procedure is 85% successful.

 Scleral

buckle. -This treatment for retinal detachment involves placing a silicone band (buckle)around the eye to hold the retina in place. This band is not visible and remains permanently attached. Thermal treatment may then be necessary to close the tear. This procedure is effective as high as 95% of the time.  Vitrectomy. -This procedure for retinal detachment is used for large tears. During a vitrectomy the vitreous is removed from the eye and replaced with a saline solution. It has similar success rates to the scleral buckle.