What Is Urrets-Zavalia Syndrome?
In the past, penetrating keratoplasty (PKP), a surgical treatment most frequently used to treat blinding corneal illness, sometimes known as a full-thickness corneal transplant for keratoconus, a condition where the cornea, which is a clear tissue in the front of the eye, protrudes in patients using Mydriatics (a class of medication that causes the eye's pupil to enlarge or open up), has been associated with Urrets-Zavalia Syndrome (UZS), which is characterized by a fixed and dilated pupil.
Following penetrating keratoplasty (PKP), six patients were reported by Alberto Urrets-Zavalia in 1963 as having wide, stiff pupils and many with posterior synechiae (adhesions between the anterior surface of the lens and the posterior iris) and iris degeneration or atrophy. At the time, it was believed that people with keratoconus, a condition where the cornea, a transparent, dome-shaped front surface of the eyes, gradually thins and bulges outward into a cone shape, were the only ones who experienced this illness.
The presence of posterior synechiae, pigment dispersion, ectropion uvea (when the iris pigmented epithelium migrates to the iris' anterior surface), anterior subcapsular lens opacities, and secondary glaucoma syndrome (through the uveoscleral outflow or the trabecular meshwork, the aqueous humor continuously drains out). Secondary glaucoma is characterized by obstruction in either of these, which can raise eye pressure and harm the optic nerve. These were additional symptoms that were not necessary for the diagnosis.
What Is the Cause Behind Urrets-Zavalia Syndrome?
The full mechanism of Urrets-Zavalia syndrome is unknown and most likely involves multiple factors. Ischemic damage to the iris and a sharp increase in intraocular pressure are the two most frequently accepted hypotheses. Triggers may include iris anomalies, which may be more prevalent in keratoconus, powerful Mydriatic injections, and putting the iris into touch with the peripheral cornea to cause peripheral anterior synechiae. Increased intraocular pressure during or after surgery, the use of Mydriatic drugs or Atropine, the presence of keratoconus, viscoelastic material remaining in the eye, and an inflammatory reaction in the anterior chamber following surgery are all potential risk factors for Urrets-Zavalia syndrome.
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Increase in Intraocular Pressure: Assumptions are made that increased intraocular pressure blocks the iris arteries. A keratoconus eye's poor stiffness may allow for the sclera's blockage of arteries near the iris's root. It was discovered that a substantial risk factor for the development of Urrets-Zavalia syndrome was an increase in intraocular pressure within 24 hours following penetrating keratoplasty.
Urrets-Zavalia syndrome is undeniably the result of an abrupt increase in intraocular pressure that causes permanent mydriasis (when the eye's black center is larger than usual), iris ischemia, and secondary pupillary sphincter atrophy. Another possibility is that topical treatments cause the iris to become affected. It was reported as a complication of toxic anterior segment syndrome, where there are fixed and dilated pupils.
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Iris Atrophy and Ischemia: Ischemic atrophy (shrinkage or withering away of a bodily tissue) of the sphincter muscle caused by iris strangulation (constriction of iris vessels) and pupil dilation is the primary explanation for the onset of Urrets-Zavalia syndrome. An immediate postoperative rise in intraocular pressure, compression of the iris vasculature against the host cornea's incision edge during surgery, and viscoelastic material left in the anterior chamber angle are all potential causes of iris ischemia.
After penetrating keratoplasty, patients who had a fixed dilated pupil exhibited delayed and segmental iris vascular filling. Additionally, the vessels are convoluted, and the iris vessels eventually leak. These angiographic results support the presence of significant iris ischemia. The use of the trephine or scissors during surgery can also result in the same.
How to Prevent Urrets-Zavalia Syndrome?
It is challenging to prevent Urrets-Zavalia syndrome because the condition's exact cause is unknown.
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Preoperative- It was discovered that intravenous Mannitol administered prior to surgery reduced the rate of fixed dilated pupils. Mannitol can prevent iris strangulation by reducing vitreous volume. It has been demonstrated that YAG (yttrium aluminum garnet) laser iridotomy carried out the day before penetrating keratoplasty can stop Urrets-Zavalia syndrome.
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Intraoperative- In order to avoid the occurrence of Urrets-Zavalia syndrome, several precautions must be taken during surgery. First, it is important to maintain a deep anterior chamber throughout. Second, great care should be taken to prevent iris trauma during surgery. Third, the surgeon must take into account doing peripheral iridotomy, which can lessen the danger of pupillary block and iris strangulation. Similar to other ocular procedures, it is advised to carefully remove any viscoelastic substance and to only leave a small quantity of air in the anterior chamber when it is necessary to do so.
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Postoperative- All patients having penetrating keratoplasty, especially those with keratoconus, require close intraocular pressure control during the first 24 hours postoperatively. Use of Mydriatics should be avoided.
What Is the Management for Urrets-Zavalia Syndrome?
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Therapy: Dapiprazole and Guanethidine drops, which are sympatholytic drugs (a medication that blocks the effects of postganglionic nerve activity in effector organs that are sympathetically innervated), have been suggested in some accounts in the literature as a way to deal with the hypertony of the iris' sympathetic nervous system and to trigger miosis or contraction of the pupils once Urrets-Zavalia Syndrome has occurred. A study showed that Pilocarpine and Guanethidine effectively cured iris sympathetic spasm and caused miosis, although many other studies showed little benefit from either of them. Acetylcholine and Pilocarpine have not shown any effectiveness in preventing Urrets-Zavalia syndrome.
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General Treatment Therapy: In Urrets-Zavalia syndrome, partial spontaneous recovery is feasible.
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Surgical Intervention: A cyclodialysis spatula should be used to break the contact between the iris and host cornea when the cause of a fixed dilated pupil is an anterior chamber that is shallow in order to prevent the iris-cornea touch from occurring again. As soon as this contact is broken, the pupil will begin to constrict. Immediate anterior chamber washing is advised if Urrets-Zavalia syndrome develops as a result of high intraocular pressure due to viscoelastic residue or blood remaining in the anterior chamber.
For symptomatic persistent mydriasis, several restorative surgical procedures are offered. These include iris sutures, corneal tattooing, and an intraocular lens with a black diaphragm. In order to alleviate visual problems and enhance cosmetic appearance, a femtosecond-assisted keratopigmentation procedure was developed.
Conclusion:
Patients having keratoplasty with elevated intraocular pressure (IOP) in the immediate postoperative phase and with residue left in the anterior chamber are at higher risk of Urrets-Zavalia syndrome.
However, the incidence of Urrets-Zavalia syndrome may be reduced by using Mannitol intravenously, controlling intraocular pressure in the initial postoperative period, and avoiding significant gas or air injection into the anterior chamber. Iridectomy may be necessary for some circumstances, such as when there is substantial air or gas in the anterior chamber, high vitreous pressure, shallow anterior chambers, or any combination of these.
