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Small pupils can create challenging phaco cases
Surgery through a 4-mm pupil is possible without using mechanical devices.
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Performing phacoemulsification through a small pupil can be challenging because the large lens needs to be fully removed via an opening that is significantly smaller without damaging the delicate iris tissue.
 Uday Devgan |
In cases of posterior synechiae, in which the iris tissue is adherent to the anterior lens capsule, gently breaking these adhesions can free the iris and allow natural enlargement of the pupil. In cases of insufficient topical pharmacologic dilation, intracameral agents such as epinephrine can be instilled to enlarge the pupil.
The pupil can be stretched using the technique described by Luther Fry, MD, using two hooks, choppers or similar instruments. This has the effect of causing micro-tears of the iris sphincter and seems more elegant that using intraocular scissors to perform macro-sphincterotomies. Once the pupil has been stretched, using the viscodilation technique of Robert Osher, MD, can help enlarge it further. Injecting a super-cohesive viscoelastic such as the viscoadaptive Healon 5 (sodium hyaluronate 2.3%, Advanced Medical Optics), the pupil can be physically pushed open to allow better access to the cataract. Mechanical devices such as iris hooks or the innovative Malyugin Ring (MicroSurgical Technology) can be used to forcibly keep the pupil expanded during surgery.
What about cases in which the pupil is smaller than average but not tiny? The size of the pupil needed to safely perform cataract surgery is generally about 4 mm in diameter. This allows sufficient access to perform surgery using a few specialized techniques.
Make the capsulorrhexis larger than the pupil
One of the chief difficulties with a small pupil is that it often leads us to create a small capsulorrhexis, and it is more challenging to perform phaco through this small opening. A small capsulorrhexis is also more prone to capsular phimosis, which can lead to a decentered IOL and compromised zonular support. This can be largely avoided by making a larger capsulorrhexis of approximately 5 mm or 5.5 mm so that it just overlaps the optic of a traditional IOL.
When making the capsulorrhexis, make sure that the leading edge of the capsular tear extends under the iris. Taking time to carefully control the creation of the capsulorrhexis allows it to be larger than the pupil. At any point, further viscoelastic can be injected to flatten the anterior lens capsule and increase control, and a second instrument such as a chopper or hook can be used to lift the iris in a quadrant to check on the position of the capsular opening. This larger capsulorrhexis will now allow us to partially prolapse the nucleus through the pupil during phacoemulsification (Figure 1).
 The capsulorrhexis edge is under the iris tissue, so its actual position is extrapolated instead of directly visualized. This allows us to create a capsulorrhexis that is larger than the pupil. |
 The nucleus is partially prolapsed through the pupil, which holds it in place. Phacoemulsification can then be performed at the iris plane. |  Use of small-gauge bimanual I&A handpieces facilitates removal of the cortex from the capsular bag for a full 360°. Images: Devgan U |
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Partially prolapse the nucleus through the pupil
The small pupil can act as an aid during surgery by holding the nucleus in position during phacoemulsification. During hydrodissection, the nucleus can be gently prolapsed out of the capsular bag and then tilted on its side. At this point, a chopper can be used to bisect the cataract while phacoemulsification is performed at the iris plane. Due to the proximity of the ultrasound energy to the corneal, it is important to use phaco power modulations and a protective viscoelastic in order to minimize the trauma to the endothelium.
The nuclear pieces can be safely emulsified by bringing them out of the capsular bag and through the pupil. Injecting viscoelastic under the nuclear pieces can also help to float them out of the capsular bag and into the anterior chamber. With the nucleus removed, the next challenge is cleaning up the cortex from the capsular bag (Figure 2).
Use bimanual irrigation and aspiration
In cases of a small pupil, accessing the cortex for a full 360° with the traditional coaxial irrigation and aspiration tip is challenging. Bimanual I&A has the advantage of separating the infusion from the aspiration so that the fluid currents in the eye can be carefully controlled. In addition, the ability to switch hands allows for a full 360° of access.
The smaller-gauge instruments make going to the capsular bag equator easier, and they allow the handpieces to be used via two small paracentesis incisions, thereby preventing the excessive leakage from the main incision, which can lead to iris prolapse.
Once the cortex is removed, a chopper or hook can be used to lift the iris in all quadrants to ensure that the capsular bag is clean. A deep fill of viscoelastic will expand the capsular bag and viscodilate the pupil to prepare for IOL insertion. I recommend slightly enlarging the main incision so that the IOL injector tip can be placed deeper into the eye and the IOL can be injected directly into the capsular bag through the small pupil. When the IOL is confirmed to be completely within the capsular bag, the viscoelastic is removed using the bimanual I&A instruments (Figure 3).
Using these techniques, we can safely perform cataract surgery through a pupil of approximately 4 mm in diameter without resorting to mechanical iris retraction devices. These patients do well, with essentially the same postoperative course as patients with larger pupils.
- Uday Devgan, MD, FACS, is in private practice at Devgan Eye Surgery in Los Angeles, Beverly Hills, and Newport Beach, California. Dr. Devgan is Chief of Ophthalmology at Olive View UCLA Medical Center and an Associate Clinical Professor at the Jules Stein Eye Institute at the UCLA School of Medicine. Dr. Devgan can be reached at 11600 Wilshire Blvd., Suite 200, Los Angeles, CA 90025; 800-337-1969; fax: 310-388-3028; e-mail: devgan@gmail.com; Web site: www.DevganEye.com. Dr.Devgan is a consultant to Abbott Medical Optics and Bausch & Lomb, and is a stockholder in Alcon Laboratories and formerly in Advanced Medical Optics.