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Study shows half of PK procedures result in ocular hypertension
Ocular hypertension is commonly seen in the long-term postoperative period after penetrating keratoplasty, and pre-existing glaucoma and additional procedures during PK are primary risk factors, according to a study.
Orucoglu and colleagues reviewed hospital charts from 146 PK procedures from 2001 to 2003 for preoperative and postoperative data to determine risk factors, incidence, patient characteristics, response to pressure-lowering medical therapy and graft outcome associated with IOP elevation.
According to the study published in the Journal of Glaucoma, the overall incidence of at least one consecutive period of ocular hypertension occurring during an average follow-up of 24.4 months after PK was 47.9% (70 eyes), with 43 cases occurring less than 1 month postoperatively, and 27 cases occurring more than 1 month after surgery.
Of those 70 eyes, 35 had a second episode of ocular hypertension after the first episode was controlled, with 29 eyes needing new or additional pressure-lowering drugs.
Patients with a history of glaucoma experienced higher IOP and earlier ocular hypertension and required more medications during periods of pressure elevation, as opposed to those without pre-existing glaucoma (p = .009).
Twenty-one patients (14.4%) had an additional surgical procedure with PK, of which 84.6% had postoperative elevated IOP (p = .007).
The authors said that mechanisms explaining a rise in IOP after PK include postoperative edema and inflammation compromising the trabecular meshwork, angle distortion, peripheral anterior synechiae, retained viscoelastics and a steroid response.
“Preventive measures for postoperative glaucoma include control of preexisting glaucoma, use of oversized donor button, goniosynechiolysis and removal of viscoelastic substance at the end of surgery,” they said.
Disclosure: The authors have no relevant financial disclosures.
Perspective
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Intraocular pressure elevation is a common finding after intraocular surgery. For patients undergoing corneal transplant (PKP), elevated IOP may lead to corneal endothelial cell damage and graft failure in addition to the possibility of glaucomatous neuropathy. Through the use of multivariate data analysis, Orucoglu and colleagues offer a more accurate understanding of the relationship between PKP and elevated IOP.
The exact mechanism of IOP elevation after surgery remains elusive and is probably multifactorial. Additionally, early postoperative- and late postoperative-onset IOP elevations are likely caused by different factors. This paper clarifies this murky area by identifying two primary risk factors for post-PKP IOP elevation: pre-existing glaucoma and additional surgical procedure (usually cataract extraction) at the time of PKP.
The paper reinforces the need to carefully screen all patients for glaucoma. Occult glaucoma at the time of PKP could result in irreversible vision loss and graft failure. Diagnosing glaucoma in a patient with a compromised cornea can be a challenge, and our corneal colleagues may not be attending to this possibility as they manage corneal disease. Better understanding factors associated with elevated post-surgical IOP will help us take better care of these patients.