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Jennifer Seino, O.D., F.A.A.O. School of Optometry

University of California, Berkeley

  Cornea –  Dome-shaped transparent tissue covering the front of

the eye; bends light to focus the image on or near the retina; about 2/3 of the focusing power of the eye

  Crystalline lens –  Transparent elastic structure behind the iris and pupil;

helps focus light with the cornea; about 1/3 of the focusing power of the eye; can also adjust it’s focusing power to focus on objects at different distances from far to near

 Retina –  Light-sensitive tissue lining the inner surface of

the eye; converts images focused by the eye’s optical system into electrical impulses and transmits them to the brain via the optic nerve

 Macula –  Small area of the retina that gives us our

detailed central vision

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  Iris –  Colored part of the eye that controls the size of

the pupil  Pupil

–  Round opening in the center of the iris; becomes smaller in bright light and larger in dim light

 Cornea and lens focus the light (image) on the retina

 Power of the eye (cornea or lens) becomes stronger or weaker

 Axial length of the eye becomes longer or shorter

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  Light (image) focused in front of the retina   Power of the eye (cornea or lens) becomes stronger

–  Cornea: increased central thickness or steeper curvature –  Lens: increased thickness, steeper curvature, moved forward, or

higher refractive index (degree to which transparent material can bend light)

  Eye becomes longer; retina moved back

 47 year old Caucasian male  Office visit  Last full eye exam 9 months prior  Complaint

–  “Vision is blurry far away with my glasses for 2 weeks” (sudden change in vision)

  20/50 vision in both eyes with his glasses

  20/20 vision with a stronger near-sighted prescription

  Eye health was normal   What should I do?

 Very thirsty for the last month  Tentative diagnosis: diabetes  Sent him to get his glucose levels (blood

sugar) tested

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 Type 2 diabetes confirmed  Patient was started on diabetes medication

and his vision returned to normal in 3 weeks

 Life-long disease in which there are high levels of glucose in the blood (blood sugar)

 Type 1 diabetes –  Body does not produce insulin (hormone

needed to move glucose into the cells, so it can be stored and used later for energy)

 Type 2 diabetes –  Most common type of diabetes –  Body does not produce enough insulin or the

body resists the effects of insulin

 Very thirsty and frequent urination –  Also, very hungry, weight loss, fatigue, slow

wound healing, more vaginal or yeast infections

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  Sudden rise in glucose level (blood sugar)

  Glucose moves into the lens of the eye

  Water follows the glucose and the lens swells (thicker with a steeper curvature)

  Lens is now more powerful resulting in more near-sightedness

 After glucose levels are under control with medication, vision will usually return to normal in about a month –  Water moves out of the lens and the lens

returns to it’s original power

 Clouding of the crystalline lens with age

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  Most common type of cataract   Hardening and yellowing of the center of the lens   Can make the lens more powerful and cause a gradual

myopic (near-sighted) shift in vision by increasing the refractive index of the lens

 Changing the patient’s spectacle prescription to a stronger near-sighted correction will often improve the distance vision

  Sudden temporary myopic shift in vision from drugs

  Case history is important   Can occur within a day to weeks of starting the

drug   Prevalence

–  Uncommon, but most common are sulfa or sulfa-related drugs

–  Can be a very large near-sighted shift in vision

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  Certain antibiotics (Bactrim, Septra) –  sulfa drug

  Topamax –  Sulfa-related drug –  Used for epilepsy, migraines,

or weight loss

 Mechanism of action for sulfa or sulfa-related drugs –  Crystalline lens moves forward and increases

the power of the eye

 Management –  Reassure the patient that vision should clear up

within a few days to weeks after discontinuing the drug

–  May not necessarily reoccur with re-administration of the drug

 Contact lens overwear, injury, ocular herpes infection –  Increased central corneal thickness and/or a

steeper corneal curvature will increase the power of the cornea

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 Can cause a small temporary myopic shift  Fluid retention can cause corneal swelling

and increase the power of the eye  Reverts back to normal after delivery or

after stops breastfeeding  Keep in mind gestational diabetes

 Become more near-sighted in dim light  Younger people more likely to be affected

(less than 40 years old)

  Most likely cause is “dark focus” –  In dim light, there is

not enough visual stimulus, so the eye adopts an intermediate focus

–  Varies, but usually focused about 1 meter in front of you

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 Night driving probably not affected by night myopia –  Studies found that driving with headlights was

not dark enough to cause “dark focus”

 Daytime photoreceptors (cones) give us our sharp, clear, fully colored vision

 Photoreceptors used at night (rods) are more sensitive to light, but give us less detailed vision

 Need to rule out eye diseases that affect night vision

 Possibly developed a small amount of myopia or astigmatism or there is a small change in your glasses or contact lens prescription

 Larger pupil at night to let in more light –  Smaller pupil during the day increases the

depth of focus (range of clarity); can conceal a small amount of uncorrected myopia or astigmatism

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  26 year old female works as an office administrator

  Complaint –  “After working on the

computer all day, my vision is blurry for a few minutes when I look far away”.

 Focusing muscles are in a spasm and unable to relax to look far away

 Associated with prolonged near work

 Need to rule out more serious causes such as: disease, infection, inflammation, drugs

 Treatment –  Treat any underlying cause –  Vision therapy to relax focus

  Light (image) focused behind the retina   Power of the eye (cornea or lens) becomes weaker

–  Cornea: flatter curvature –  Lens: decreased thickness

  Axial length of the eye becomes shorter; retina moved forward

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 Small central area of the retina with a high concentration of cone photoreceptors

 Central, sharp, detailed, color vision

 Fluid leaks under the macula and pushes the retina forward

 Light (image) is focused behind the retina and causes a small hyperopic (far-sighted) shift in vision

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  20-50 year old men; can also affect women   Usually in one eye   Symptoms

–  Blurred or dim central vision –  Distorted vision –  Colors appear washed out –  Or possibly no symptoms

  Associated with higher levels of cortisol (hormone released during times of physical or psychological stress)

 Who is at risk? –  Type A personality, stressful event, pregnancy,

certain medications, Cushing’s Syndrome  Typically heals without treatment in 3-4

months  Usually regain good vision; can be recurrent

 Aphakia –  Crystalline lens in

the eye removed and no intraocular lens implanted

–  Become very hyperopic

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 Light rays do not focus at a single point on or near the retina  Cornea is not perfectly spherical

(“basketball”)  Cornea is more curved (steeper) in some

meridians than others; steepest meridian is usually perpendicular to the flattest meridian (“football”)

 Regular astigmatism   Irregular astigmatism

–  Usually associated with eye diseases

 Cornea: change in the shape (power) of the cornea

 Lens: change in the lens power along a meridian or a change in the positioning of the lens in the eye

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 Oil gland in the eyelid gets infected and inflamed

 Red, tender lump in the eyelid

 Can put pressure on the cornea and cause an irregular astigmatism by reshaping the cornea

 Frequent warm compresses –  Apply for 10 minutes, four times a day

 Antibiotics may be necessary

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 Mass of tissue that grows onto the cornea  Usually occurs in the 3:00 or 9:00 position

 Can flatten the cornea in that area and cause irregular astigmatism

 Associated with ultraviolet radiation (sun exposure)

 Protect eyes from UV rays from the sun (sunglasses)

 Artificial tear eye drops for irritation  Anti-inflammatory eye drops for redness  Surgery is an option

–  Possibility of re-growth

 Middle of cornea thins and bulges forward forming a cone shape

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 Abnormal curvature causes irregular astigmatism

 Often begins during puberty

  Rigid contact lenses or specialty contact lenses   Corneal transplant if scarring or very poor vision

  Intacs corneal ring implant –  Flattens the central cornea

 Corneal Collagen Cross-Linking (CXL)   clinical trials

  Riboflavin drops saturate the cornea which is then activated by UV light

  Increases the amount of collagen cross-linking in the cornea; strengthens the cornea

  Not a cure, but can slow the progression of keratoconus

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  Injury –  Ring of fibrous strands holding the lens in place can

break –  Can cause irregular astigmatism (lens tilted or looking

through the peripheral portion of the lens)

  Connective tissue disorder resulting in heart problems, skeletal disorders (long arms, legs, fingers), lung and central nervous system problems, and eye problems

  Fibrous strands made of connective tissue that hold the lens in place may weaken and break; lens usually moves upward

  Can cause irregular astigmatism (lens tilted or looking through the peripheral lens)

 Need to move the focus of light (image) onto the retina to see clearly

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 Flatten the cornea with a rigid contact lens worn during sleep; weaken the power of the cornea

 Remove the contact lens in the morning

 See clearly for about one day

  Flatter/weaker cornea does not bend the light as much; the image moves back and focuses on the retina

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 Corrects low to moderate amounts of myopia (near-sightedness) and low amounts of astigmatism

 Reversible  Half the cost of LASIK

  Cut a flap in the cornea, reshape the cornea with a laser by removing tissue, then reposition the flap

 Can correct myopia, hyperopia and astigmatism

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  Steeper/stronger cornea bends the light more; the image moves forward and focuses on the retina

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  Flattening the steeper meridian of the cornea to focus the image on the retina

  Implant lens in front of the eye’s natural lens and behind the iris

 FDA-approved for correction of myopia  More invasive surgery; more expensive  Alternative for patients not suitable for

LASIK or other refractive surgeries due to very high myopia

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 Remove the crystalline lens in the eye and replace it with a new lens implant with a different power

 Like cataract surgery without the cataract  More invasive surgery; expensive  Cannot change focus to look up close with a

standard monofocal lens implant