Ab externo scleral fixation technique optimizes IOL placement, power 

The procedure reduces the amount of time the eye is open, cutting the risk of complications such as choroidal hemorrhage and retinal detachment. 

Issue: October 10, 2012

An ab externo scleral fixation technique for secondary posterior IOL implantation optimizes lens position and postoperative refraction, according to a report. 

Additionally, the technique is safer and simpler than other ab externo scleral fixation approaches, the authors said. 

“You have incredibly good centration,” Alan S. Crandall, MD, the corresponding author, told Ocular Surgery News. “You know exactly where the lens is going. You can be more predictive on your power and you can have less tilt and rotation of the lens.” 

The technique minimizes the amount of time the eye is open, reducing the risk of choroidal hemorrhage, retinal detachment and other complications. 

Alan S. Crandall

“The eye is not even open for more than a minute and a half or 2 minutes,” Crandall said. 

The method involves a relatively flat learning curve, except for anterior segment surgeons who are not accustomed to working through a pars plana approach, he said. 

Crandall and colleagues described the technique in the Journal of Cataract and Refractive Surgery. 

Peritomies and sclerotomies 

The procedure begins with two 4-mm limbal conjunctival peritomies made 180° apart. 

“I use a Mendez scleral marker so I’m sure they’re 180° away from each other,” Crandall said. “You do the peritomy, open up the conjunctiva and the Tenon’s capsule about 3 mm to 4 mm behind the limbus and cauterize it if necessary, but I like to minimize that. You want to use little inflammatory stimulation just for the safety of the eye.” 

The peritomies are located near the vertical meridian of the eye to avoid the horizontal meridian and facilitate IOL insertion through a temporal clear corneal incision. A small radial relaxing incision is cut at one end of each peritomy to increase scleral bed exposure, Crandall and colleagues said. 

A stepped diamond paracentesis blade is used to make two grooves in the scleral bed 2 mm posterior to the limbus, at the junction of the cornea and sclera. 

“It gives you a beautiful flap,” Crandall said.  

Each groove is 300 µm to 400 µm deep. The IOL sutures are tied and the knots are hidden in the grooves at the end of surgery. 

A 23-gauge microvitreoretinal blade is used to create two sclerotomies about 2 mm apart at the bottom of each scleral groove, for a total of four sclerotomies. 

“You’re basically at pars plana but just in the region where the ciliary sulcus should be, so you’re not 3 mm or 4 mm back. You’re right behind the ciliary body,” Crandall said.  

IOL insertion, suturing 

To prepare the IOL for insertion, Crandall said he ties 8-0 Gore-Tex sutures to the eyelets of the haptics. 

“You use Gore-Tex sutures because they last indefinitely, they’re very immunologic-free and don’t cause any inflammation,” Crandall said. “They don’t erode, so you don’t have to make a lot of deep flaps or anything to hide the Prolene sutures or nylon sutures. You just tie them where you want to leave them. You don’t have to put scleral patches over them or anything like that.” 

Gore-Tex sutures are used off-label for IOL fixation, Crandall noted. 

A diamond paracentesis blade is used to create a 7-mm stepped clear corneal incision. A 2.2-mm diamond keratome is used to enter the anterior chamber at the bottom of the corneal incision. An ophthalmic viscosurgical device is used to protect the cornea and anterior chamber. 

A small loop of each IOL suture is inserted into the anterior chamber through the clear corneal incision. Each suture loop is pulled out through its respective sclerotomy using 25-gauge internal limiting membrane forceps. Four suture ends are retrieved and pulled through the sclerotomies. 

“You’ve now got your sutures through the lens and into the sclera, and at this point you can open up the lens to the full 6 mm, quickly slip the lens in, pull those sutures tight, and then close the eye before you tie them so you keep the pressure in the eye,” Crandall said. 

IOP should be maintained at about 20 mm Hg to 25 mm Hg. 

The corneal incision is closed with 10-0 nylon sutures before the IOL sutures are tightened and tucked into the scleral grooves, Crandall said. – by Matt Hasson 

Reference:

Slade DS, Hater MA, Cionni RJ, Crandall AS. Ab externo scleral fixation of intraocular lens. J Cataract Refract Surg. 2012;38(8):1316-1321.

For more information:

Alan S. Crandall, MD, can be reached at John Moran Eye Center, 65 Mario Capecchi Drive, Salt Lake City, UT 84132; email: alan.crandall@hsc.utah.edu.
Disclosure: Crandall has no relevant financial disclosures.