For the cataract surgeon, a small, poorly dilated pupil is defined by a pupil diameter that is—despite intense topical application of mydriatics—below the intended size of the capsulorhexis. Although it is still possible in these cases to perform a subpupillary capsulorhexis by hand, the operation is at risk of becoming increasingly difficult should problems arise during the capsulorhexis or during later steps in the procedure. A poorly dilated pupil can be expected in eyes with comorbidities such as a hard lens, pseudoexfoliation, glaucoma, chronic uveitis, and zonular dehiscence, as well as after earlier surgery and in eyes with floppy iris syndrome.1–3 Cataract surgery in eyes with small pupils is associated with a higher rate of complications.3 Examples of established means to dilate these pupils are the injection of epinephrine into the anterior chamber and the use of viscomydriasis. However, sometimes there is no way of avoiding a mechanical dilation to achieve better visualization. There are several options available to enlarge pupils mechanically, such as iris retractors4–7 that can be inserted through paracenteses or the Malyugin Ring (Microsurgical Technology, Redmond, WA). The Malyugin Ring is inserted through a main incision and expands the iris to achieve a pupil diameter of 6.25 or 7.0 mm, depending on the version used.8,9
We describe several techniques for femtosecond laser-assisted cataract surgery for small pupils.
Materials and Methods
Femtosecond laser treatment can be employed with considerable benefit for the patient, even in these difficult cases. In cataract surgery on patients who have a small, poorly dilated pupil, the femtosecond laser system is placed in a sterile operating room to avoid transporting the patient to and from separate rooms for the different steps of the procedure. In our institution, the Catalys Precision Laser System (Abbott Medical Optics, Inc., Santa Ana, CA) is located in a dedicated operating room for laser cataract surgery. The patient was positioned on the same table from the beginning to the end of the surgery and was rotated between the femtosecond laser or under the operating microscope, which is located adjacent to the laser. To maintain sterility during the entire procedure, the touchscreen, laser control buttons, and vacuum connection port were draped with sterile transparent foils. The patient interface and the disposable lens of the laser system were supplied sterile. A cup holder (Geuder, Heidelberg, Germany) was used to store the suction ring sterile.
After sterile draping and insertion of an eyelid speculum, two paracenteses were created manually under the microscope visualization and ophthalmic viscosurgical devices (OVDs) were homogenously injected in the anterior chamber. Depending on the nature of the intended procedure, we continued with one of the four surgical techniques described below.
1a: Dilating the Pupil With Iris Retractors but Without OVD
Depending on individual requirements, up to 5 incisions are made with a 27-gauge needle (Smiths Medical ASD, Keene, NH) attached to a blank aspiration/irrigation device (Geuder). A small channel following the direction of these steep stab incisions is created. Using suture tying forceps, the iris retractors are inserted and the iris retracted with their curved endings (MicroVision, Inc., Seabrook, NH). In the next step, the OVD is bimanually removed by the irrigation/aspiration hand piece (Geuder) and the anterior chamber is stabilized with BSS (Alcon, Fort Worth, TX). If necessary, a gentle hydration of the paracenteses might follow to guarantee water-tight wound closure. After removal of the OVD, the iris retractor caps can be re-aligned. The use of a cohesive OVD is advisable and preferred over a dispersive OVD for a fast and complete removal from the anterior chamber after iris retractors are in place.
When docking the ocular surface to the laser, the femtosecond laser personal liquid optics interface (LOI) has a hollow suction ring that does not touch the cornea and induces only minimal increase in intraocular pressure. Therefore, two or three laterally placed iris hooks can be directly positioned inside the LOI by moving the suction ring laterally; the other hooks will be moved by the surgeon using the tying forceps into the LOI field. When all retractors are inside the LOI (Figure 1), the suction process will be commenced and the docking done as usual. If there is no OVD in the anterior chamber, the default laser settings are deployed. After femtosecond laser fragmentation and capsulotomy (and, possibly, relaxing corneal incisions), the patient is undocked and rotated under the operating microscope.
Docking of the eye with the liquid optics interface after using the Malyugin Ring (Microsurgical Technology, Redmond, WA) for mechanical pupil dilation.
1b: Dilating the Pupil With Iris Retractors Using OVD
After creating up to five paracenteses with the Blumenthal lancet (BD Ophthalmic Systems, Bidford on Avon, United Kingdom) in a somewhat steeper angle than normal, the retractors are hooked to the iris and the pupil is stretched to the intended size. In this version of the procedure, the OVD remains in the anterior chamber while the eye pressure is kept stable by injecting additional OVD via one of the paracenteses, if required.
The choice of OVD employed for this operation should depend on the viscoelastic’s refractive index. Both the diagnostic imaging and the targeting of the femtosecond laser beam depend on the presence of fluid in the anterior chamber. Therefore, it is wise to use an OVD with a refractive index close to that of aqueous humor. If there is a major difference between these indices, changes to laser settings should be considered for safety reasons. The level height of the laser application to perform capsulotomy should be chosen rather higher than lower; the safety distance to the posterior capsule is recommended to be more than 500 μm in all circumstances. Performing corneal incisions with the laser does not affect the type of OVD to be used. If necessary, the paracenteses will be carefully hydrated. The iris retractors will be handled as described above (technique 1a) while the LOI is lowered and tilted; the other retractors will be turned/elevated inward, which does not affect the iris’ attachment to the hooks. Next the LOI is docked to the eye as usual.
However, the laser settings should be adjusted due to the presence of OVD in the anterior chamber. We recommend employing higher pulse energy (10 μJ pulse energy) and elevating the incision depth to 1,000 μm. The spot separation is not changed (horizontal spot spacing 5 μm; vertical spot spacing 10 μm).
When the anterior chamber is filled with OVD, fewer and smaller cavitation bubbles can be expected during laser treatment. On reaching threshold, optical breakdown occurs with plasma formation. Then an acoustic shockwave causes a cavitation bubble to form and collapse. What remains is the cut region and gas, which is mostly carbon dioxide. The higher the OVD’s viscosity, the lower the number and size of bubbles. In particular, Healon 5 (AMO, Abbott Park, IL) suppresses the formation of bubbles. The lens fragmentation and all of the other steps of the procedure follow just as in a normal eye.
2a: Malyugin Ring Without OVD
After performing up to two paracenteses, the main corneal incision is done in a manual two-step fashion, size 1.8 to 2.75 mm. After homogenous filling of the anterior chamber with OVD, the Malyugin Ring is implanted using the injector system provided by the manufacturer. The Frankfurt iris manipulator (Geuder) can be used to attach the iris to the ring’s four loops. A bimanual approach is used to remove the OVD by using the irrigation/aspiration handpiece. The anterior chamber may also be cleared of OVD using a coaxial technique. After stabilizing the anterior chamber with BSS and careful hydration of the paracenteses and the main incision, docking is performed (Figure 2) and the procedure initiated with the appropriate settings.
Docking of the eye with the liquid optics interface after using disposable iris retractors for mechanical pupil dilation.
2b: Malyugin Ring With OVD
This procedure resembles 2a with one difference: the OVD is left in place. There are hardly any gas bubbles now from the femtosecond laser, not even when administering a higher pulse energy. The anterior surface of the lens might be flattened or, depending on the quantity and the characteristics of the OVD, slightly dented. This may require a manual alignment to the detected anterior lens surface, normally performed automatically.
Seventy-three patients (73 eyes) with small pupils were treated with one of the four described techniques. In all cases, it was possible to install the mechanical dilation device without complications. Less balanced salt solution was necessary to pressurize the eye with the OVD in the anterior chamber. In all groups, no flattening of the anterior chamber or other complications occurred during docking or the laser treatment. Furthermore, there was no anterior or posterior capsule tear during the procedure. After OVD removal and filling the anterior chamber with balanced salt solution (n = 38), the anterior capsulotomy was free without adhesion or tags and no tongue-like slivers were recognized. With the OVD in the anterior chamber (n = 35), small adhesions were recognized in 6 cases. With the described central dimple-down maneuver it was possible to solve all of them. A posterior chamber intraocular lens was implanted into the capsular bag in all cases without complications.
Incomplete capsulotomies with tags and other irregularities were strikingly more frequent when the anterior chamber was still filled with OVD during laser treatment.
To perform a predictable, well-centered, and well-shaped femtosecond laser capsulotomy and femtosecond laser nuclear fragmentation is crucial for surgical success in eyes that challenge the surgeon because of small pupils, dense nuclei, or zonular weakness. Laser preconditioning the nucleus by means of 300- to 500-μm lens fragmentation (especially Lens Opacification Classification System III grade 4–5 nuclear sclerotic cataracts) frequently renders the lens completely moveable and easy to rotate and removable with minimal or no ultrasound phacoemulsification. Using the different techniques described here can make eyes with small pupils accessible to femtosecond laser treatment after mechanical dilation of the pupil. Operating with a sufficiently large (or in these cases, enlarged) pupil makes sense because, in addition to the capsulotomy, an intense lens fragmentation and preparation becomes possible.
Our own experiences with both options (Malyugin Ring, iris retractor) are excellent (n = 73). After a thorough cleansing of the anterior chamber or when completely refraining from using OVD, capsulotomies could be done with the expected highest quality. To verify whether we have achieved a free-floating capsulotomy, the so-called dimple-down maneuver has proved to be valuable: we open the paracentesis with a blunt cannula attached to a BSS or an OVD syringe, instill OVD to maintain the anterior chamber (if desired), advance the cannula to the middle of the lens capsule, and press downward with the tip of the cannula at the center of the capsule (Figure 3). This downward motion indents the capsule disc, pulls it gently centrally, separates the free edge from the surrounding peripheral capsule, and confirms that there is a continuous 360 degree cut with a free flap. If a tag is present, this maneuver will identify its location and usually “pop’” it free without causing a radial tear. We have not seen any capsule tears resulting from femtosecond laser capsule tags using this dimple-down technique in more than 500 cases.10
Dimple-down maneuver to identify the free floating anterior capsular disc.
Another consideration is the potential flattening or collapse of the anterior chamber due to the lack of OVD or high intraocular pressure. The intraocular pressure increase while docking the LOI is moderate with the system we use (approximately 10 mm Hg) and allows us to perform both techniques, with OVD or with OVD removal (Figure 4), in an extremely safe way and without having to fear anterior chamber instability.11,12 An impending collapse of the anterior chamber while docked is harder to detect without optical coherence tomography images that refresh throughout the treatment. Fortunately, the time that elapses between initiating the capsulotomy and starting the lens fragmentation (which starts posterior, of course) is 2 seconds at best. Therefore, the chances of a flattening of the anterior chamber and a subsequent forward movement of the posterior capsular position are small as long as there is a water-tight wound closure. Observing a capsulotomy without any signs of cavitation bubbles can serve as an indication that the different layers are shifting and a re-scan is required. In our patients, this phenomenon has not been observed with the described technique, either with or without OVD. Being aware of this potential issue is particularly essential to avoid a primary perforation of the posterior capsule, especially if the corneal main incision was made too short and more broad. Keeping OVD in the anterior chamber is, of course, safer with regard to the stability of the anterior chamber and the tightness of the wound. This applies to operations under topical anesthesia and circumstances that make docking more difficult such as deep-set eyes, vis-a-tergo (pressure from behind the vitreous), narrow palpebral fissures, or an agitated patient.
Screenshot taken from the laser system’s infrared camera: performing capsulotomy with and without ophthalmic viscosurgical device (OVD). (A) Only few and small bubbles are visible in an OVD-filled anterior chamber. (B) There is a multitude of gas bubbles in the absence of OVD, just as in a “normal” operation, with a perfectly dilated pupil.
The automated pupil detection system may be rendered useless by a mechanical pupil dilation, as might be the option of planning the capsulotomy based on the “scanned capsule” (Figure 5). In these cases, the target position of the capsulotomy can be positioned using a custom approach or by aligning the capsulotomy automatically based on the limbus detection.
Spectral-domain three-dimensional optical coherence tomography of the anterior segment of the eye, sagittal plane, of a treatment without ophthalmic viscosurgical device in the anterior chamber. The anterior surface of the lens is visibly deformed.
Excessive hydration of the paracenteses and the main incision should be avoided when entering the eye prior to laser treatment. Remarkably, even an accidental corneal opacification from stromal hydration can diminish the ability for laser pulses to reach threshold and cut in that segment.
For patients receiving anticoagulation therapy, special care should be taken if the corneal incisions are placed close to the limbus and demonstrate bleeding. In this case, it is preferable to wait a minute or two until coagulation has set in. Blood can also be washed out of the LOI. If blood remains in the optical axis, spectral-domain optical coherence tomography displays a plethora of white dots, reminiscent of a starry sky. Hemoglobin, the chromophores in blood, absorb laser energy and thus lessen the quality of the laser cut (Figure 6).
Three-dimensional spectral-domain optical coherence tomography of the anterior segment in a patient receiving anticoagulation therapy. White dots, like stars in the sky, above the cornea indicate the presence of blood within the balanced salt solution.
Compared to iris retractors, handling the Malyugin Ring is easier, less elaborate, and faster. It has been reported that in eyes with narrow pupils, the Malyugin Ring is associated with less endothelial cell loss than manual pupillary stretching with iris hooks.13
Employing mechanical pupil dilation in the way described herein enables the surgeon to perform a safe (given the acceptable rise in intraocular pressure) femtosecond laser cataract surgery in eyes with small pupils and comorbidities (Figure 7). Safety may be attributed to the sharp reduction of trauma to the tissue. Even these challenging eyes may profit from the benefits the femtosecond laser offers to cataract surgery.
Picture taken through the operating microscope at the end of a successful laser treatment without ophthalmic viscosurgical device. (A) A Malyugin Ring (Microsurgical Technology, Redmond, WA) and (B) disposable iris retractors can be detected inside the anterior chamber.
- Thomas R, Nirmalan PK, Krishnaiah S. Pseudoexfoliation in southern India: the Andhra Pradesh Eye Disease Study. Invest Ophthalmol Vis Sci. 2005;46:1170–1176. doi:10.1167/iovs.04-1062 [CrossRef]
- Agrawal R, Murthy S, Ganesh SK, Phaik CS, Sangwan V, Biswas J. Cataract surgery in uveitis. Int J Inflam. 2012;2012:548453.
- Artzén D, Lundström M, Behndig A, Stenevi U, Lydahl E, Montan P. Capsule complication during cataract surgery: case-control study of preoperative and intraoperative risk factors: Swedish Capsule Rupture Study Group report 2. J Cataract Refract Surg. 2009;35:1688–1693. doi:10.1016/j.jcrs.2009.05.026 [CrossRef]
- Novák J. Flexible iris hooks for phacoemulsification. J Cataract Refract Surg. 1997;23:828–831. doi:10.1016/S0886-3350(97)80238-6 [CrossRef]
- Kadonosono K, Ohno S. New iris retractor for pupil dilatation during anterior vitrectomy: double-hook iris retractor. Ophthalmic Surg Lasers. 1999;30:241–243.
- Tognetto D, Agolini G, Grandi G, Ravalico G. Iris alteration using mechanical iris retractors. J Cataract Refract Surg. 2001;27:1703–1705. doi:10.1016/S0886-3350(01)00764-7 [CrossRef]
- Oetting TA, Omphroy LC. Modified technique using flexible iris retractors in clear corneal cataract surgery. J Cataract Refract Surg. 2002;28:596–598. doi:10.1016/S0886-3350(01)01100-2 [CrossRef]
- Malyugin B. Small pupil phaco surgery: a new technique. Ann Ophthalmol (Skokie). 2007;39:185–193. doi:10.1007/s12009-007-0023-8 [CrossRef]
- Agarwal A, Malyugin B, Kumar DA, Jacob S, Agarwal A, Laks L. Modified Malyugin ring iris expansion technique in small-pupil cataract surgery with posterior capsule defect. J Cataract Refract Surg. 2008;34:724–726. doi:10.1016/j.jcrs.2008.01.024 [CrossRef]
- Arbisser LB, Schultz T, Dick HB. Central dimple-down maneuver for consistent continuous femtosecond laser capsulotomy. J Cataract Refract Surg. In press.
- Schultz T, Conrad-Hengerer I, Hengerer FH, Dick HB. Intraocular pressure variation during femtosecond laser-assisted cataract surgery using a fluid-filled interface. J Cataract Refract Surg. 2013;39:22–27. doi:10.1016/j.jcrs.2012.10.038 [CrossRef]
- Kerr NM, Abell RG, Vote BJ, Toh T. Intraocular pressure during femtosecond laser pretreatment of cataract. J Cataract Refract Surg. 2013;39:339–342. doi:10.1016/j.jcrs.2012.12.008 [CrossRef]
- Wilczynski M, Wierzchowski T, Synder A, Omulecki W. Results of phacoemulsification with Malyugin Ring in comparison with manual iris stretching with hooks in eyes with narrow pupil. Eur J Ophthalmol. 2013;23:196–201. doi:10.5301/ejo.5000204 [CrossRef]