Dilated pupil examinations are a crucial component of regular care for people with diabetes. In preparation for these examinations, patients receive special eye drops that enlarge their pupils. This provides the examiner with a clearer view of the back of the eye, and makes it easier to see damage caused by diabetes. Patients with diabetes are at high risk for eye diseases such as diabetic retinopathy, glaucoma and cataracts.

Sometimes this exam helps uncover diabetes in a person who was previously undiagnosed. Blurry vision or other visual difficulties can be a symptom of diabetes.

All ophthalmologists and some specially trained optometrists can perform dilated eye examinations. Ophthalmologists are physicians who can also prescribe medications and perform surgeries. Patients may want to ask their primary care physician to recommend an eye-care specialist with a track record of treating patients who have diabetes.

People with diabetes should have a dilated pupil examination at least annually. This will help physicians to better diagnose and treat eye disorders in the early stages of their development.

The eye drops used to dilate the pupils may prevent patients from properly focusing their eyes afterward. Patients may be advised not to drive home.

Dilated pupil examinations allow physicians to use special eye drops that give them a clearer view of the health of their patients’ eyes. These drops enlarge the pupil, the black, circular part of the eye that allows light into the eye. Such tests are crucial for people with diabetes, who are at high risk of developing several eye disorders.

High glucose (blood sugar) levels, high blood pressure, unhealthy levels of cholesterol and other factors associated with diabetes can weaken the walls of the retinal capillaries (tiny blood vessels) of the retina. Nerve fibers also may become damaged because of lack of blood flow.

Many eye disorders occur without manifesting any symptoms in the early stages. Dilated pupil examinations can help physicians uncover subtle changes in the retina, optic nerve or other eye structures that may indicate the beginnings of a more serious problem.

Eye disorders associated with diabetes include:

• Diabetic retinopathy. Damage to the blood vessels that bring oxygen and nutrients to the retina, the light-sensitive tissue at the back of the eye. It is the leading cause of blindness in working–age American adults.

  

• Glaucoma. Damage to the optic nerve, usually caused by an increase in fluid pressure inside the eye. It leads to loss of peripheral (side) vision and can eventually cause blindness. Glaucoma also occurs in nondiabetics, but the risk of getting the disease is much higher in people with diabetes.
  
  
• Cataracts. Clouding of the lens of the eye. It tends to occur in older people and also affects nondiabetics. However, diabetes increases the risk of developing cataracts at a younger age.
  
  
• Age-related macular degeneration (AMD). A disease that blurs central vision. It is a leading cause of vision loss in elders. The National Eye Institute reports a link between obesity (a common feature of type 2 diabetes) and the progression of AMD. Maternally inherited diabetes and deafness (MIDD), a rare form of type 2 diabetes, can cause damage similar to that of AMD.

In addition, Wolfram syndrome, a rare genetic disorder, involves insulin-dependent diabetes, damage to the optic nerves, deafness and diabetes insipidus. 

Other endocrine disorders that may impair vision include Graves’ disease, which can cause the eyes to bulge and can cause severe double vision, scar the corneas and damage the optic nerves.

Individuals with diabetes should have a dilated pupil examination at least annually. This will help physicians to better diagnose and treat eye disorders in the early stages of their development. Women with diabetes who become pregnant should promptly schedule a dilated pupil examination.

Sometimes this test helps uncover diabetes in a person who was previously undiagnosed. Blurry vision or other visual difficulties can be a symptom of diabetes. Follow-up testing with glucose tests can yield a diagnosis of prediabetes or diabetes and lead to treatment that will limit complications.

Patients may want to schedule the eye examination with an ophthalmologist (a physician who specializes in eye diseases). An ophthalmologist is the only specialist who can detect, diagnose and treat diabetic retinopathy. Some optometrists can perform the dilated pupil examination, but they are not medical doctors and cannot perform surgery to treat diabetic eye disease.

Technicians will likely administer some parts of the eye exam, but the ophthalmologist or optometrist will interpret and discuss results with the patient. The testing is generally painless but can involve bright lights, drops that may produce a slight sting and instruments that touch the eyes.

Before the dilated pupil examination, the examiner is likely to ask patients whether they have experienced any vision problems or other symptoms related to the eyes. Examples of such symptoms might include:

• Blurred vision
• Double vision
• Narrowed field of vision
• Floating spots in vision
• Feeling of pressure or pain in the eyes

The examiner will measure visual acuity by asking the patient to read a standard eye chart. The patient will receive a numeric value (such as 20/20 or 20/40) that indicates the strength of vision. The patient may also be asked to view a series of dot patterns as a means of testing color perception.

To reveal any problems with eye movements, the examiner will test the eye muscles by having the patient look in various directions. Peripheral vision, the ability to see out of the side of the eyes, may also be checked by the doctor or technician.

Special eye drops will then be introduced into the patient’s eyes to allow the pupils to dilate (open wider). It may take between 15 to 20 minutes for the pupil to fully dilate. Dilated pupils give the examiner a wider view of the inside of the patient’s eyes, which are examined using a special instrument called an ophthalmoscope or funduscope. A bright light mounted on a microscope, called a slit lamp, may be used.

Special eye drops will then be introduced into the patient’s eyes to allow the pupils to dilate, or open wider. It may take between 15 to 20 minutes for the pupil to fully dilate. Dilated pupils give the examiner a wider view of the inside of the patient’s eyes, which are examined using a special instrument called an ophthalmoscope.

In some cases where leakage of dye into the center of the retina is detected on exam, a dye is injected into the patient’s arm vein to test for the extent of the diabetic retinopathy. The physician waits for the dye to travel to the blood vessels in the retina and, in photographs taken with special filters to show the dye in the blood vessels, observes whether or not the vessels leak. This procedure is known as fluorescein angiography.

Structures that are examined during the dilated pupil examination include:

• Retina (the light-sensitive tissue at the back of the eye)
• Blood vessels
• Optic nerve (which carries the images from the retina to the brain)

In addition, the examiner is likely to conduct the following tests:

• Examine the surface of the cornea (outermost portion of the front of the eye) for defects or scratches.
  
  
• Measure pressure inside the eye, a test called tonometry. Elevated pressure is a key indicator of glaucoma.
  
  
• Examine the iris (the colored part of the front of the eye, surrounding the pupil) for signs of new blood vessels. The vessels can be caused by lack of blood flow to the eye, and can cause neovascular "new blood vessel" glaucoma.

In a test that is not routinely performed for diabetes, the thickness of the corneas can be measured with ultrasound in a test called pachymetry. Thicker corneas reduce the risk of glaucoma.

If an exam reveals an eye disease or disorder such as diabetic retinopathy, glaucoma or cataracts, follow–up examinations and treatments are likely. If the eyes have no changes from diabetes, a follow-up will be scheduled for one year.

The eye drops used to dilate the pupils may prevent the patient from properly focusing the eyes for up to several hours afterward. This can particularly affect near vision. The physician may recommend against driving afterward or may instruct the patient to wear sunglasses if driving. Sunglasses can also bring relief to sensitive eyes after the test when in a brightly lit room.

If the exam reveals a problem, the physician may recommend additional testing, regular monitoring, medication such as prescription eye drops, or procedures such as photocoagulation or vitrectomy.

Preparing questions in advance can help patients have more meaningful discussions with their physicians regarding their conditions. Patients may wish to ask their doctor the following questions about the dilated pupil examination:

1. How often should I have a dilated pupil exam?
   
   
2. Should my test be performed by an ophthalmologist?
   
   
3. What will my dilated pupil exam include?
   
   
4. Will I also have visual field testing, a test of the pressure inside my eyes, a test of the thickness of my corneas or anything else? Do I need fluorescein angiography to check for diabetic retinopathy?
   
   
5. How long will my testing take?
   
   
6. Do I need to do anything to prepare? Should I bring sunglasses with me for afterward?
   
   
7. Could I find any of the testing uncomfortable?
   
   
8. What do my test results show?
   
   
9. If I need follow-up tests, what do they involve, and when will they take place?
   
   
10. If I need treatment, what are my options?
    
    
11. Is it safe for me to drive home afterward, or do I need a ride?