Introduction
Diabetes mellitus can cause serious complications associated with the eyes. Conditions like diabetic retinopathy, cataracts, and macular edema can lead to vision loss. Diabetes causes dysfunction of blood vessels in the retina of the eye. The associated problems are blurred vision and blindness.
What Is a Pupil?
The pupil is the round opening at the center of the iris, which is the colored part of the eye. The pupil lets the lights enter the eye. It gets smaller in bright light and dilates (becomes more significant) in dim light.
Pupils help in perceiving images. During darkness, pupils dilate or open widely, allowing more light to enter the eyes and maximize vision.
The pupil shrinks to a small diameter in bright light to protect the sensitive photoreceptors in the eye's retina. The involuntary reflex causes it to blink or squint and limits excess light from entering the eye.
Pupils can change their size in certain states of emotion. The pupil becomes small when a person becomes angry or doubtful. Similarly, the pupil widens when a person is surprised or happy.
What Is Pupillary Response?
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Miosis or constriction response is the narrowing of the pupil. Constriction occurs when the circular muscles contract and the radial muscle relaxes.
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Mydriasis, or a dilation response, is caused by the dilation of the radial muscle's smooth cells when the iris sphincter muscles relax.
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The pupil's normal size in bright light in adults varies from 2 mm to 4 mm in diameter. In dim light, the variation is 4 mm to 8 mm in diameter. Both pupils are generally equal in size. Pupils dilate due to certain diseases, drugs, and meditations.
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Diabetes can cause specific changes in the pupil, leading to smaller pupil size. Such patients find it difficult to adjust to darker places. The normal pupillary response is lost in diabetes. This decrease in pupillary size is termed pupillary miosis, commonly associated with type 1 diabetes mellitus.
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In diabetic patients, the pupillary reflex remains the same, and the pupil size is reduced. This is due to damage to the retinal blood vessels.
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Children with type 1 diabetes mellitus show decreased pupillary size. The reduced pupillary size is considered a symptom of retinopathy in long-term diabetes.
How Does Blood Sugar Level Affect Pupillary Response?
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Hypoglycemia and Dilated Pupils:
When the blood sugar level decreases, an episode of hypoglycemia occurs, resulting in nervousness, irritability, tiredness, and a dilated pupil, which is a significant sign. This can be a vital sign in children with episodes of hypoglycemia, as children cannot express themselves.
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Diabetes and Iritis:
Iritis is an inflammatory condition of the Iris that causes blurred vision and sensitivity to light. This condition is also called uveitis and is seen in type 1 diabetes patients. People with diabetic neuropathy may experience episodes of iritis. It can occur in both eyes.
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Distortion or Degeneration of the Eye:
Distortion of the Iris rarely occurs due to trauma, injuries, or surgeries. People with diabetes are more prone to such atrophic changes. High blood sugar and blood pressure damage small blood vessels, and a lack of blood supply to the Iris can lead to iris atrophy.
What Are the Pupillary Changes in Diabetic Retinopathy?
Diabetic retinopathy is a severe complication in patients with uncontrolled diabetes. Increased blood sugar for a long time can damage the retinal blood vessels. Diabetes-related autonomic dysfunction can be seen in the pupillary response of the eye. In diabetic retinopathy, pupillary abnormalities appear before the clinical signs. The changes are detected by examining pupillomotor function. Dynamic pupillometry is a simple, inexpensive, and non-invasive procedure for studying various diseases affecting the autonomic nervous system. In diabetic patients, the pupillary dynamics are abnormal due to autonomic dysfunction.
How Is the Pupillary Examination Done?
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After taking a brief initial history of the patient, an ophthalmic examination using a slit lamp is done. Patients are asked to sit in a dark room for 15 minutes. Pupilography was performed with a ⅓ inch infrared camera and flashlight.
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The pupillary diameter was measured with infrared light with a 760 nm to 870 nm wavelength. The pupil size and response are recorded and plotted in a graph against time. Retinal photographs were also taken after pupillary dilatation.
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The pupillary reaction in diabetic retinopathy is studied to find autonomic nervous dysfunction. In diabetes patients, the pupillary response is poor. A poorly reactive or larger pupil is a result of long-standing diabetic neuropathy.
What Alters the Function of a Pupil?
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Myopathic Causes: In diabetes patients, the presence of higher glucose levels causes the storage of excess glucose as glycogen. Glycogen can be accumulated in the iris muscles. This abnormal accumulation of glycogen in iris muscle causes contraction dysfunction. This shows the presence of a vacuole in the Iris epithelium and is an accepted sign of acute diabetes.
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Neuropathic Causes: Neuropathic changes can be seen at three levels:
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Optic Neuropathy: Ischemic optic neuropathy is commonly seen in diabetes patients. In such a clinical condition, the direct pupillary reaction is lost. And in the other eye, the same for the indirect pupillary light reflex.
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Cranial Neuropathy: Damage to the nerves in the brain.
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Autonomic Neuropathy: In long-standing diabetes, a smaller pupil size is detected. Diabetic autonomic neuropathy is manifested as pupillary dysfunction of the eye.
What Are the Iris Complications Associated With Diabetes?
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Iris Transluminance - It is a condition commonly seen among type 2 diabetes patients causing a frosted glass appearance of the Iris.
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Rubeosis Iridis - The formation of new abnormal blood vessels in the Iris characterizes it. It is a strong indicator of proliferative diabetic retinopathy. The newly formed blood vessels are fragile and lead blood and protein into the eye. This is called neovascularization.
What Are the Ways to Prevent Complications in the Iris?
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Use proper sunglasses and protective glasses to avoid exposure to harmful UV radiation.
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For cleaning eyes, use a sterile wash solution.
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Properly take the diabetes medications.
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Monitor the blood pressure regularly.
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Get routine eye examinations done.
Conclusion:
Unregulated blood sugar levels can cause severe damage to the eye's Iris. The pupillary response of the eye is reduced, and the amount of light that enters the eye is reduced, making night vision more difficult. Proper treatment of the conditions associated with them is important, as it helps to improve and restore vision rather than end up in blindness.
