ESCRS - Small pupils can create difficulty in phacoemulsification ;
ESCRS - Small pupils can create difficulty in phacoemulsification ;

Small pupils can create difficulty in phacoemulsification

Part 1 of a two-part article

Small pupils can create difficulty in phacoemulsification
TBC Soosan Jacob
Published: Friday, December 2, 2016
  [caption id="attachment_6834" align="alignnone" width="750"]A: Iris stretch B: Tri-prolonged pupil stretcher C: Mini-Sphincterotomy D: Vertical Chop A: Iris stretch B: Tri-prolonged pupil stretcher C: Mini-Sphincterotomy D: Vertical Chop[/caption]     A small pupil, either a poorly dilating one or one that constricts intraoperatively, can create difficulty in each step of phacoemulsification and result in a downward spiralling sequence of events. A pupil smaller than 5mm may result in a smaller-sized rhexis than desired. Difficult manoeuvring can cause accidental iris aspiration, iris damage, bleeding, unintentional anterior capsular tears, difficulty in nucleus and cortical removal and in-the-bag intraocular lens (IOL) insertion and IOL rotation in case of toric IOLs. Difficult surgery can result in unwanted complications such as iridodialysis, zonulodialysis, hyphema, nucleus drop, IOL drop etc. Postoperatively, prolonged and difficult surgery can result in striate keratopathy, anterior chamber inflammation, secondary glaucoma, irregular tied down pupil, iris defects/atrophic patches, cystoid macular oedema etc. A small rhexis can also result in future complications such as capsular phimosis, IOL decentration etc. It is therefore important to be prepared. PREOPERATIVE CONSIDERATIONS: Pupillary dynamics and dilated pupil size should be noted preoperatively. A thorough history and examination reveals any underlying aetiology, such as long-term topical miotics, rigid pupil, posterior synechiae, pseudoexfoliation syndrome, diabetic and post-uveitic patients and those on alpha-1 antagonists such as tamsulosin (FLOMAX®, Boehringer Ingelheim) for prostatic hypertrophy. Mydriatic and non-steroidal anti-inflammatory drug (NSAID) drops should be used preoperatively on the day of surgery. Inadequate preoperative mydriatics can result in poor dilatation or intraoperative constriction. INTRAOPERATIVE CONSIDERATIONS: Intracameral pharmacological mydriasis: Shugarcaine (1cc preservative-free 4% lidocaine and 3cc BSS plus, created by the late Dr Joel Shugar) is a well-tolerated, neutral pH intracameral anaesthetic which paralyses the pupil sphincter. Epinephrine is especially useful in intraoperative floppy iris syndrome (IFIS) as it reduces iris prolapse and billowing. Intracameral phenylephrine 1.5% may also be used together with lidocaine 2%. Epi-Shugarcaine (3cc preservative-free 4% lidocaine, 4cc bisulfite free 1:1000 epinephrine and 9cc BSS plus) increases pupil dilatation and iris rigidity by increasing dilator smooth muscle tone. Toxic anterior segment syndrome (TASS), especially with improper dilution and systemic hypertensive spikes, though rare, may occur. Mechanical mydriasis: High molecular weight cohesive viscoelastics such as Healon-5/ Healon GV can be injected into the centre of the pupil for pupillary dilatation in some cases. Repeated instillation may be required. Surgical mydriasis: Synechiolysis, if required, may be done with viscoelastic or a blunt spatula. Pupillary membranes may be cut and removed using intraocular micro-instruments. Any bleeding can generally be tamponaded with air. Small, less than 1mm mini-sphincterotomy cuts on the iris that are limited to sphincter tissue can be made with Vannas scissors or vitreoretinal scissors. Pupillary stretching, as described by Dr Luther Fry, can also be performed. Under viscoelastic cover, the pupil is stretched gently in one or more axes using two Kuglen Hooks, taking care to avoid large sphincter tears. Two-, three- and four-pronged pupil stretchers are also available. Pupil stretch has the disadvantages of creating large sphincter tears and making the iris flaccid which can cause repeated iris prolapse through phaco incisions, especially in poorly constructed, short tunnels. They can also increase postoperative inflammation. A combination of mini-sphincterotomies/gentle stretch with viscoexpansion may be employed. Pupil expander devices may be used for phaco in patients 
with small pupil (these will be 
discussed in Part 2). PHACO CONSIDERATIONS: Phaco incisions need to be self-sealing and sufficiently long. Too short or leaking tunnels can allow repeated iris prolapse and iris trauma. Viscoelastic may be used to expand the pupil. The rhexis should be done through a partial entry to avoid the ophthalmic viscosurgical device (OVD) from escaping, which can allow the pupil to constrict again. Capsular dye may be used for better visualisation. It is possible to carry the rhexis just outside the pupillary margin by keeping the anterior capsular flap flat and by repeatedly redirecting it. With sufficient experience, it is often possible to carefully perform phaco through a 4-4.5mm pupil, provided the iris is not atonic or floppy. As a smaller rhexis can increase chances of a capsular blowout, only gentle multi-quadrant hydrodissection is done. Blind manoeuvres under the iris should be avoided and vertical chop can be used for nuclear disassembly. Soft nuclei may be hydrodelineated well and then gently hydroprolapsed out. The phaco tip should remain only in the centre of the pupil to avoid iris aspiration. Once aspirated, there is a tendency for repeated aspiration at same site. The second instrument may be used to hold the iris margin away during intraoperative manoeuvres. Irrigation/aspiration (I/A) is easier with the bimanual technique. Capsule polishing mode can often be helpful to grasp and bring sub-incisional cortex centrally, following which vacuum can be increased for aspiration. A slow expanding IOL may be easier to insert, making sure both haptics enter the capsular bag. More intensive postoperative steroids may be required for controlling inflammation. In situations which do not allow adequate visualisation or if the surgeon feels the need for it, one or more of the previously mentioned techniques/devices may be used to expand the pupil. IFIS: Described by Chang and Campbell, this presents with progressive intraoperative pupillary constriction, along with billowing of a flaccid iris and iris prolapse into the phaco incisions. These may be tackled using pharmacological strategies (described earlier), bimanual microincision phacoemulsification, gentle hydrodissection, a highly viscous or viscoadaptive OVD, low flow parameters, directing irrigating currents away from the pupillary margin and mechanical pupillary dilators such as iris hooks and expansion rings. Mini-sphincterotomies and pupillary stretch are ineffective and may worsen iris flaccidity. FEMTOSECOND LASER-ASSISTED CATARACT SURGERY (FLACS): A pupil less than 6mm in diameter is a relative contraindication to FLACS. Though possible to perform an anterior capsulotomy with a 5.0mm pupil, there is risk of accidental iris injury. Laser application itself can cause pupillary miosis and lenticular fragmentation may become more difficult or cause iris trauma. Pre-treatment with a topical NSAID may be done to decrease prostaglandin induced miosis. Soosan Jacob MS, FRCS, DNB is Director and Chief of Dr Agarwal’s Refractive and Cornea Foundation at Dr Agarwal’s Eye Hospital, Chennai, India. She has a patent pending for the Glued Capsular Hook dr_soosanj@hotmail.com
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