What Is Essential Iris Atrophy? 

Introduction

Essential iris atrophy (EIA) is a rare eye condition characterised by the degeneration of the iris, the coloured part of the eye that surrounds the pupil. The degeneration takes the form of a thinning of the iris due to the formation of holes.¹ This disorder is one of the diseases that make up iridocorneal endothelial syndrome or ICE syndrome (along with Chandler syndrome and Cogan-Reese syndrome), an eye disorder that involves changes to the eye structure, which can lead to various visual disturbances and complications.² The condition mainly affects the elderly population, more commonly people assigned female at birth (AFAB) ³. This article will discuss various aspects of essential iris atrophy, including its causes, symptoms, diagnosis, and treatment options.

Structure and function of the iris

The iris is the thin, circular, coloured part of the eye. Muscles in the iris control the pupil, which appears as a small black circle in the middle of the eye that lets light into the eye. 

In bright light, the iris muscles contract to reduce the diameter of the pupil and, thus, the amount of light that can enter the eye. Conversely, if there is little available light, the iris muscles relax to enlarge the pupil so that more light can enter the eye.  

Causes of essential iris atrophy

The exact cause of EIA has not been established, but it may be due to a combination of genetic and environmental influences. Some of the influencing factors involved are: 

• Ageing: essential iris atrophy is primarily an age-related condition. As individuals grow older, changes in vision are common, and the tissues in the iris can gradually degenerate, leading to EIA.
• Genetic factors: some research suggests that there may be a genetic predisposition to EIA. Some genetic variations can lead to an increase in the risk of developing this condition. These mutations can be inherited from parents who carry the mutated gene or can occur as a spontaneous new mutation in the individual.
• Other medical conditions: EIA can also be associated with other medical conditions, such as glaucoma or Fuchs' endothelial dystrophy, which can contribute to the atrophy of the iris.

Signs and symptoms of essential iris atrophy

The symptoms of essential iris atrophy can vary from person to person, and some individuals may remain asymptomatic for a long time. For some people, the progression of their symptoms may be slow, while others may see rapid effects on their vision. These mostly involve changes in the vision. 

Common signs and symptoms include:

• Changes in iris colour: one of the most noticeable signs of EIA is a change in the pigmentation and colour of the iris. The affected eye may appear to have a lighter or faded colour compared to the unaffected eye
• Pupillary abnormalities: EIA can cause irregularities in the shape and size of the pupil, leading to issues like anisocoria, which is characterised by a difference in pupil sizes between the eyes and a distorted pupil shape
• Glare sensitivity: people with EIA often experience increased sensitivity to bright lights or glare, making it a challenge to drive at night or be in brightly lit environments
• Visual disturbances: blurred vision and other visual disturbances can occur as a result of the changes in the iris and pupil. These disturbances can affect daily activities and the overall quality of the person’s vision⁴

Diagnosis of essential iris atrophy

Diagnosing essential iris atrophy typically involves a detailed and comprehensive eye examination conducted by an ophthalmologist, followed by additional tests to confirm the condition and distinguish it from other eye disorders. The following diagnostic methods are commonly used:

• Visual examination: the ophthalmologist will visually assess the iris for any colour changes, irregularities in pupil shape or size, and other abnormalities
• Slit-Lamp biomicroscopy: this specialized microscope is useful for a detailed examination of the iris, as it provides a close-up view of any structural changes.⁵
• Measurement of pupil reactions: the doctor may measure how the pupils react to light and assess them for any abnormal responses.
• Gonioscopy: This test checks for signs of glaucoma and helps determine if there are any abnormalities or blockages in the drainage angle (anterior chamber angle) of the eye, which can be associated with EIA.
• Imaging tests: high-resolution imaging techniques, such as optical coherence tomography (OCT) or ultrasound, can provide detailed images of the anterior segment of the eye, assisting in the diagnosis

Complications associated with essential iris atrophy

While EIA itself is not typically a sight-threatening condition, it can lead to complications, including:

• Glaucoma: individuals with EIA may have an increased risk of developing glaucoma. The drainage angle is the part of the eye where the sclera (the white covering of the eye) meets the iris, and it forms a complete circle at the edge of the iris. The drainage angle is the opening which allows fluid in the front of the eye (aqueous humour) to drain out of the eye into the blood in the veins. By permitting control of the level of fluid within the eye, it controls pressure within the eye (intraocular pressure). Changes in the drainage angle of the eye can potentially lead to elevated intraocular pressure and cause vision loss by damaging the optic nerve in the back of the eye. This is known as glaucoma.
• Cataracts: EIA can increase the risk of cataract formation, a cloudy patch in the eye's lens. These patches can increase in size and cause blurry vision, further impacting vision if left untreated
• Vision impairment: as the condition progresses, visual disturbances may become more pronounced, affecting daily activities and the individual’s quality of life.⁶

Treatment options for essential iris atrophy

There is a range of treatment options for EIA; the choice of treatment may depend on the stage of the disease and consideration of the patient’s medical history.  These options can slow down the progression of the disease and reduce symptoms to enhance existing capacities and restore visual function. 

1. Symptomatic management: in mild cases of EIA, treatment may focus on managing symptoms. This can include wearing tinted glasses to provide UV protection and reduce glare sensitivity or using eye drops or artificial tears to alleviate dryness and discomfort
2. Surgical interventions:
   • Iridoplasty: in some cases, laser iridoplasty can be performed to reshape the iris and improve pupil function. This is done by using low-energy lasers to place small burns into the iris so that the iris can widen the anterior chamber angle so it is at a safer position
   • Iridectomy: this procedure is performed to surgically remove part of the iris and is useful in preventing the development of glaucoma 
   • Cataract surgery: if cataracts develop as a complication of EIA, cataract surgery may be recommended to restore clear vision. The doctor will remove the cloudy lens and replace it with an artificial lens inside the eye, which is called an intraocular lens
   • Glaucoma management: individuals with EIA and associated glaucoma may require glaucoma medications or surgical interventions to control intraocular pressure.⁷

Future directions in EIA research

As essential iris atrophy remains a relatively rare and poorly understood condition, ongoing research is essential to advance understanding of its causes and develop more effective treatment strategies. Future research may focus on:

1. Genetic studies: identifying specific genetic markers associated with EIA could help predict and prevent the condition in at-risk individuals
2. Novel therapies: investigating potential drug therapies or minimally invasive procedures that can slow down or halt the progression of iris atrophy
3. Patient outcomes: conducting long-term studies to assess the visual and overall health outcomes of individuals with EIA who undergo various treatments

Summary

Essential iris atrophy is a rare but significant eye condition that primarily affects the elderly population. While it may not be sight-threatening in itself, EIA can lead to various visual disturbances and complications that have an impact on an individual's quality of life. Early diagnosis and appropriate management, including surgical interventions, when necessary, can help improve visual outcomes and reduce complications. As research in this field continues to evolve, more effective strategies for managing and potentially preventing essential iris atrophy in the future can be developed.