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Five pearls should be considered to protect the endothelium after cataract surgery. These involve consideration of the phacoemulsification techniques and technology, use of viscoelastics, irrigation and aspiration techniques, intracameral medications, and postoperative medications.
Take-Home Message: Five pearls should be considered to protect the endothelium after cataract surgery. These involve consideration of the phacoemulsification techniques and technology, use of viscoelastics, irrigation and aspiration techniques, intracameral medications, and postoperative medications.
By Lynda Charters; Reviewed by Terry Kim, MD
Durham, NC-Protecting the endothelium during cataract surgery can be a challenge for seasoned or novice surgeons alike depending on the status of patients, according to Terry Kim, MD.
Factors are as varied as the patients’ cases, said Dr. Kim, professor of ophthalmology, Duke University School of Medicine, and director of fellowship programs, Cornea and Refractive Surgery Services, Duke University Eye Center, Durham, NC.
Long-recognized non-corneal risk factors to watch out for to prevent injury to the corneal endothelial cells are a shallow or crowded anterior chamber, the density of the nucleus, small pupils, the volume of the infusion, the amount of ultrasound energy used, and the type of IOL to be implanted, he said.
Even more important are the following corneal characteristics that may be predictive of problems-i.e., older patient age characterized by a lower endothelial cell density and the presence of Fuchs’ dystrophy and diabetes mellitus, he noted.
Surgeons have a number of factors to consider in their decision making during the preoperative testing. Specifically, in high-risk patients, they must decide whether to perform a cataract extraction or a Descemet’s stripping endothelial keratoplasty (DSEK) triple procedure that includes corneal transplant, cataract removal, and IOL insertion.
During preoperative testing, surgeons should be aware of any symptoms the patient may have-the severity of guttae (specular reflection), stromal edema, lens density, and the anterior chamber depth observed during the slit lamp examination, and any other comorbidities. The examination also includes pachymetry and specular microscopy.
Dr. Kim offered five pearls for protecting the endothelium that include consideration of the:
The phacoemulsification technique that includes a horizontal or vertical chop procedure reduces both the energy used in the eye and the ultrasound time.
“The benefits of ultrasound power modulation are greatly reduced repulsion, decreased turbulence, enhanced followability, lower risk of thermal burns, and less endothelial trauma, which results in less total energy used and less endothelial cellular loss at 6 months postoperatively,” Dr. Kim said.
The power phaco modulation capability, he noted, is available in the following platforms: Alcon Centurion Torsional IP, the AMO Signature Ellips FX, and the Bausch + Lomb Stellaris with Hyperburst technology.
Phaco technology includes the relatively recent introduction of femtosecond-assisted cataract surgery. With femtosecond laser-assisted cataract surgery, the average phaco time has been decreased substantially from an average power of about 23.5% with phaco-only to about 13.5% with the more advanced technology, Dr. Kim noted.
The effective phaco time also was reduced from about 1 minute to less than 30 seconds, respectively.
Three types of viscoelastics are used in the eye depending on the patient:
The importance of removing all nuclear fragments cannot be overemphasized, Dr. Kim noted. He recounted a retrospective case series from the Duke Eye Center that included 54 eyes of 54 patients with lens fragments after cataract surgery identified by slit lamp evaluation, gonioscopy, and ultrasound biomicroscopy. All lens fragments were found in the inferior angle and 80% of patients with corneal edema were diagnosed with a lens fragment after day 1 postoperatively.
Importantly, three of five patients who had corneal edema that did not resolve after lens extraction required DSEK to treat corneal decompensation.
Toxic anterior segment syndrome (TASS) is a devastating, albeit rare, complication after cataract surgery, Dr. Kim continued.
TASS-which typically begins 12 to 48 hours following cataract or anterior segment surgery-is a clinically relative, sterile postoperative inflammatory reaction caused by a noninfectious substance that enters the anterior segment and causes toxic damage to the intraocular tissues. The syndrome improves after treatment with corticosteroids.
While irrigating solutions or ophthalmic viscoelastic devices and ophthalmic instrument contaminants are culprits in TASS, ocular medications also have been implicated. Incorrect concentrations, pH, or osmolality; a vehicle with incorrect pH or osmolality; and preservatives in a medication solution have been identified as causes.
Omidria (Omeros Corp.) is a new clear, colorless, sterile solution concentrate for intraoperative administration that has received FDA approval. The solution contains phenylephrine hydrochloride 1% and ketorolac tromethamine 0.3% and no preservatives or bisulfites. The product does not need to be mixed or the dilution calculated; one vial is injected into 500 milliliters of balanced saline irrigating solution.
Medical therapy after cataract surgery includes instillation of corticosteroids prednisolone acetate 1% and difluprednate 0.05%, newer delivery systems via nanoparticles and punctal plugs, and future medications such as Rho-kinase inhibitors, Dr. Kim said.
Terry Kim, MD
Dr. Kim is a consultant to Alcon Laboratories, Bausch + Lomb, Ivantis, Kala Pharmaceuticals, Ocular Systems Inc., Ocular Therapeutix, Omeros, PowerVision, Shire, and TearScience.