EyeWorld is the official news magazine of the American Society of Cataract & Refractive Surgery.
Issue link: https://digital.eyeworld.org/i/78721
60 EW RESIDENTS Practice continued from page 58 Practicing cataract surgery in the wet lab poses several challenges. First and foremost is finding a substitute for the human eye with: 1) anatomic similarity, 2) realistic tissue "feel," 3) clear view through the cornea and anterior chamber, and 4) reasonable cost. There is no perfect system, but five options are worth discussing. Human cadaveric eyes are ideal in size and dimensions, as well as tissue feel. However, the cost ($200 each) prohibits sequential practice. Visibility through the cornea can be problematic. It is important to re- quest phakic cadaveric eyes to avoid receiving pseudophakic or aphakic eyes by accident. Pig eyes are much less expensive ($3 each), though freshness is essential as the cornea clouds with tissue decay. Difficulties with pig eyes are twofold: 1) the much larger size and dimensions create difficulty in reaching across the anterior chamber with standard phaco instruments, and 2) the cap- sule is extremely elastic, and it is nearly impossible to prevent a cap- sulorhexis from running away unless the capsule is pretreated (see below). Lens size and capsular thickness in rabbits is similar to that of humans, although the rabbit lens occupies disproportionately more space within the anterior chamber, and proximity to the cornea makes ma- nipulation of instruments difficult. Additionally, practice on (or ex- planting lenses from) live animals has significant cost, both financial and ethical. Computerized simula- tors such as the VRmagic Eyesi (VRmagic, Mannheim, Germany) allow unlimited practice and repeti- tion without actual tissue, instru- ments, or lab space. Although feedback sensation may not be per- fectly realistic, the cerebellar train- ing through reiterated movements is beneficial. My preferred system is the synthetic eye model from Phillips Studio in the U.K. Each eye costs about $20, but the dimensions are perfect, the cornea is always clear, the lens capsule is realistic, and the nucleus can be made to a density that feels like true senile cataract, receptive to sculpting and chopping. Once an eye model system is se- lected, there are a few tricks to assist in phaco practice. Cloudy corneas can be treated with glycerine and the epithelium can be scraped to im- prove visibility. Soft globes can be inflated with saline. I recommend staining pig capsules with trypan blue to improve visibility and de- crease elasticity. The capsulorhexis can also be practiced on boiled tomatoes. Pig eyes can be mi- crowaved or injected with alcohol to increase lens hardness and opacifica- tion. Practicing nuclear fragmenta- tion (cracking and chopping) is best done with an actual phaco machine and surgeon settings. However, many critical steps in phaco surgery (wound construction, capsulorhexis, and hydrodissection) can be prac- ticed without a machine. In my opinion, a large component of the learning needed in phaco surgery is cerebellar—and therefore repetition is key. Repetition in seemingly artifi- cial environments (e.g., rhexis on a tomato or a simulator) still leads to increased comfort and agility during real surgery. Lastly, the value of hav- ing an experienced phaco teacher watch and proctor surgical practice cannot be underestimated. An hour or two of supervised practice can set the foundation of good technique that will translate to improved pa- tient outcomes. EW References 1. Ophthalmic Surg. (1985) 16:182-184. Contact information Chiu: chiuc@vision.ucsf.edu Johnson: a-tim-johnson@uiowa.edu Reisman: jreisman@tuftsmedicalcenter.org January 2012