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.