Postoperative Flat Anterior Chamber

What Is the Anterior Chamber of the Eye?

The region between the transparent part (cornea) and pigmented part (iris) of the eye filled with gel-like aqueous humor is known as the anterior chamber of the eye. The anterior chamber becomes shallower with old age and hypermetropia (farsightedness). The usual range of anterior chamber depth is between 1.5 to 4 mm.

What Is a Postoperative Flat Anterior Chamber?

The postoperative flat anterior chamber (POFAC) is described as the shallowing of the eye's anterior chamber owing to surgical procedures like trabeculectomy. POFAC occurs in association with a decreased tone of the eye muscles (hypotony) and increased eye pressure.

What Are the Causes Responsible for Postoperative Flat Anterior Chamber?

The leading cause for POFAC is either the hypotony of the muscles or the change in intraocular pressure and reduced resistance of the aqueous eye fluid flow from the opaque white part (sclera) after surgery.

The variety of causes associated with POFAC are:

1. Factors responsible for low intraocular pressure and early onset POFAC include

• Choroidal detachment.

• Ciliary body detachment.

2. Factors responsible for low intraocular pressure and late-onset POFAC are:

• Retinal detachment.

• Uveitis.

3. Factors responsible for normal or elevated intraocular pressure are:

• Pupillary block.

• Malignant glaucoma.

What Are the Risk Components Associated With the Postoperative Flat Anterior Chamber?

During the operative procedures, the incidence of POFAC is increased by several risk factors. The risk factors linked to POFAC are:

• Postoperative aphakia (missing lens).

• Elevated intraocular pressure.

• Tightness of the scleral flap.

• The firmness of eyepatches.

• Use of antimetabolites during surgery.

What Are the Different Forms of Postoperative Flat Anterior Chamber?

Based on the onset of POFAC after surgery, is of three types:

• Early-onset FAC occurs within one to seven days after surgery.

• Intermittent onset FAC occurs from seven to thirty days of surgery.

• Late-onset FAC appears after thirty days of surgery.

How Are Flat Anterior Chambers Graded?

The flat anterior chamber (FAC) of the eye are graded anatomically into three grades:

• Grade I - The corneal epithelium is in contact with the whole iris.

• Grade II - Cornea and iris are in contact only in the periphery of the iris.

• Grade III - Iris is completely in contact with the cornea and vitreous.

What Is the Mechanism Involved Behind the Development of Postoperative Flat Anterior Chamber?

• A severe case of FAC following surgical procedures like trabeculectomy results in the detachment of the thin tissue in the middle layer of the eye (choroidal membrane) and the ciliary body.

• As a result of which, there is an increased outflow of the aqueous humor outside into the anterior chamber angle and diminished aqueous humor production in the eye.

• It is also associated with the reduced flow into the subconjunctival space.

• These mechanisms increase intraocular pressure.

What Are the Different Clinical Signs and Symptoms Associated With Postoperative Flat Anterior Chamber?

A flat anterior chamber often results in a bleb leak (tear or hole in the conjunctiva during the surgical procedure), over-filtration, and choroidal outflow in the eye.

• A leak from the conjunctiva occurring in POFAC is of two forms:

  1. An iridocorneal leak that deepens within seven days.

  2. Corneal edema due to corneo-lenticular leak.

• A non-reacting pupil with increased intraocular pressure (pupillary blockade).

How Are Postoperative Flat Anterior Chambers Diagnosed?

Assessment of the flat anterior chamber includes clinical examination and imaging.

• Sidel's test is crucial in measuring the aqueous leakage from the eye's anterior chamber.

• Physical examination of the anterior chamber is done with the help of the pen torch method. It is the most straightforward method to detect anterior chamber depth and angle.

• Smith's method is the quickest screening tool to assess the anterior chamber quantitatively.

• Van Herrick's technique measures the size of the chamber quantitatively.

• Gonioscopy and the slit lamp technique are the gold standards for visualizing the anterior chamber.

• Imaging of the anterior chamber is performed with optical coherence tomography (OCT). It takes a cross-sectional image of the eye's structures and measures the angle.

What Are the Complications of Postoperative Flat Anterior Chamber?

Prolonged and untreated POFAC is associated with several other complications:

• Cataract.

• Peripheral anterior synechiae (adhesion of the iris to the angle).

• Dysfunction of the corneal blood vessels.

• Postoperative visual acuity loss.

• Malignant glaucoma syndrome

What Are the Conditions That Are Considered Before Confirming the Diagnosis of POFAC?

Diseases that are excluded before formin diagnosis of POFAC are:

• Angle-closure glaucoma is a condition when the bulging iris narrows the eye's drainage between the cornea and the iris. It leads to increased intraocular pressure.

• In severe cases, hypermetropia, also known as long-sightedness, is associated with the flat anterior chamber of the eye.

How Is Postoperative Flat Anterior Chamber Managed?

Management of POFAC includes:

• Immediate withdrawal of antimetabolites.

• Choroidal effusions are treated with atropine cycloplegics and corticosteroids to help in the reduction of inflammation.

• Treatment of grade I and II FAC includes cycloplegics and tight bandages. Viscoelastic injections are injected into the anterior chamber of the eye. The lesion is resutured.

• Surgery is indicated in case of persistent kissing choroidal and grade III FAC or compromise to the corneal endothelium.

• Patients at increased risk of malignant glaucoma require immediate surgical intervention.

• Corneo-lenticular leaks require aggressive treatment.

What Is the Prognosis of the Ocular Surgeries and Postoperative Flat Anterior Chamber of the Eye?

Overall, FAC reduces the surgery's success rate and slows the healing process because of the inflammatory reaction associated with it. Grade II and III FAC further worsen the prognosis post-surgery due to the added complications associated with POFAC.

Conclusion

The postoperative flat anterior chamber is an emergency ocular complication occurring early after eye surgeries. Vigilant follow-up of the patient immediately post-surgery prevents the advent of POFAC and its complications.