What causes penetrating keratoplasty and glaucoma (PKPG)?

Updated: Dec 30, 2020
  • Author: Shibandri Das, MD; Chief Editor: Inci Irak Dersu, MD, MPH  more...
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Answer

Zimmerman and colleagues [24]  demonstrated on eye bank human eye models that the depth of sutures during PKP can disrupt outflow channels of the trabecular meshwork by weakening iridocorneal angle support, particularly in aphakic eyes.

Rumelt and colleagues [11]  reported the incidence of various causes of PKPG as closed-angle glaucoma (59%), corticosteroids (21%), open-angle glaucoma (11%), angle recession (3%), aqueous misdirection (3%), and unknown (3%).

Dada and colleagues [25]  reported ultrasound biomicroscopy findings in 31 eyes with postkeratoplasty glaucoma. The types of synechiae noted on ultrasound biomicroscopy included peripheral anterior synechiae in 96.7% (30/31) of eyes, synechiae at the graft-host junction in 41.93% (13/31) of eyes, both peripheral anterior synechiae and graft-host junction synechiae in 38.7% (12/31) of eyes, central iridocorneal synechiae in 19.3% (6/31) of eyes, and intraocular lens iris synechiae in 9.6% (3/31) of eyes. [25]  The authors concluded that secondary angle closure caused by anterior synechiae formation is one of the important causes of PKPG in eyes with opaque grafts. [25]  

Other factors that are specific to patients who have undergone keratoplasty exist. Olson and Kaufman [26]  used a mathematical model to show that the elevated IOP after keratoplasty in a patient with aphakia might be the result of angle distortion secondary to a roll of excess compressed tissue in the angle. As a result of edema and inflammation, the trabecular meshwork function is compromised. According to Olson and Kaufman, [26]  "F]actors that contribute to angle distortion include tight suturing, long bites (more compressed tissue), larger trephine sizes, smaller recipient corneal diameter, and increased peripheral corneal thickness.” [26]  

Conversely, less tight wounds, smaller trephine sizes, donor corneas larger than recipient corneas, thinner recipient corneas, and larger overall corneal diameter tend to alleviate the angle distortion; therefore, donor corneal size should be kept in the range of 7.5 mm to 8.5 mm with a decentration of 0.5 mm or greater. [27, 28, 29]


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