Human cataractous lens nucleus implantedin a sheep eye lens as a modelfor phacoemulsification trainingOzcan Kayıkcıoglu, MD, Sait Egrilmez, MD, Sinan Emre, MD, Tansu Erakgun, MD

We describe a realistic and inexpensive experimental cataract model for phaco-emulsification training. After a capsulorhexis is performed, a deep cavity in thelens of an enucleated sheep eye is formed by phacoemulsification through a lat-eral incision. An undamaged human cataractous lens nucleus obtained by extra-capsular cataract extraction is inserted in the preformed cavity, resting in thecenter of a cortex cushion. Phacoemulsification training is performed through acorneal tunnel incision. The experimental model is prepared with a human catarac-tous lens nucleus of the preferred hardness, simulating nuclear phacoemulsifica-tion in humans.

J Cataract Refract Surg 2004; 30:555–557 2004 ASCRS and ESCRS

Performing phacoemulsification in human eye-bank cataract extraction (ECCE) and kept in a moist chambermodels,1,2 animal eyes,3�7 or plastic model eyes8 or a balanced salt solution at �4�C. A lateral stab

is essential for acquiring and mastering this modern incision is made at the corneoscleral limbus of a freshlyintraocular surgical technique. However, it is difficult enucleated sheep eye at the 9 o’clock position by ato obtain human cadaver eyes in countries with limita- 3.2 mm slit knife. A capsulorhexis is accomplishedtions on human eye-banking and organ donation; plas- with a Utrata forceps under an ophthalmic viscosurgicaltic models are expensive and not available in developing device (OVD). Phacoemulsification (DORC Harmonycountries; and experimental animal models with a soft 6800 HSP 3) of the central area of the sheep eye lens isnucleus do not simulate actual human cataract surgery, done to form a deep cavity for placement of a humanparticularly nuclear phacoemulsification. Many tech- lens nucleus. The incision at 9 o’clock is then enlargedniques to induce reproducible cataract models with hard to 5.0 to 7.0 mm using a scissors, and a human lensnuclei for phacoemulsification training have been re- nucleus of the preferred hardness is inserted into theported.2–7 We describe an experimental model in sheep preformed sheep eye lens cavity. The corneal entry siteeyes harboring a cataractous human lens nucleus. at 9 o’clock is sutured tightly with 10-0 monofilament

nylon (Figure 1).Phacoemulsification training can be started at thisTechnique

This experimental model uses an undamaged hu- point with the model that has a human lens nucleus.man cataractous lens nucleus obtained by extracapsular A corneal tunnel incision for phacoemulsification prac-

tice is performed with a 3.2 mm slit knife at 12 o’clock.A side-port incision is created using a 20-gauge MVR

Accepted for publication August 12, 2003.blade at 2 o’clock.

From Celal Bayar University Faculty of Medicine, Department ofPhacoemulsification by the desired technique andOphthalmology (Kayıkcıoglu), Manisa, and Ege University Faculty of

other ECCE techniques including manual nucleus-Medicine, Department of Ophthalmology (Egrilmez, Emre, Erakgun),Izmir, Turkey. cracking methods have been performed in the prepared

model. After a human lens nucleus has been emulsified,None of the authors has a financial interest in any product mentioned.

another can be inserted into the same sheep eye byReprint requests to Ozcan Kayıkcıoglu, MD, Gediz Cad No 11/2,35040 Bornova, Izmir, Turkey. E-mail: orkayikcioglu@ttnet.net.tr. loosening the lateral incision sutures.

2004 ASCRS and ESCRS 0886-3350/04/$–see front matterPublished by Elsevier Inc. doi:10.1016/j.jcrs.2003.08.018

TECHNIQUES: KAYIKCIOGLU

DiscussionAnimal eye models may not simulate actual phaco-

emulsification surgery since the nuclear material is clearand soft. Thus, many alternatives have been suggestedto induce a hard cataractous nucleus; these includechemicals 2–5 or microwave7, a synthetic nucleus,8 or-ganic material such as chestnuts,9 or even implantationof a whole human lens in rabbit eyes.10 We searchedfor an easy and realistic method using inexpensive andreadily available material.

Extracapsular cataract surgery is still performed forsenile cataracts in many clinics in developing countriestrying to convert to phacoemulsification or in cases ofpoor zonular support for safety reasons. This means

Figure 1. (Kayıkcıoglu) Human lens nucleus (arrows) inserted in plenty of available human lens nuclei for training pur-the sheep eye lens cortical cavity.

poses, which is the main focus of our technique. Weused freshly enucleated sheep eyes as they were readily

Results available; however, other animal eyes can be used inEight bimanual and 2 1-handed phacoemulsifica- the same manner.

In our study, real cataractous human lens nucleition techniques were performed in the eye model. Fourwere used rather than artificially induced cataract nuclei.freshly enucleated sheep eyes were used by the traineesThus, the trainees were able to experience the exactduring practice sessions. The implanted nucleus tendedhardness fragmentation characteristics, thickness, diam-to move to the periphery of the capsule and behind theeter, and color of human lens nuclei during phacoemul-iris with fluid turbulence or when pushed with thesification practice.phacoemulsification tip during 1-handed phacoemulsi-

We also had the chance to perform phacoemulsifi-fication. This was solved by creating a deeper cavity incation in 2 human nuclei kept in 10% formalin inthe sheep lens to hold the nucleus better.our model. We observed that formalin changed theManipulation and emulsification of the nucleusconsistency and fragility of the nuclei, possibly by dena-were easier to perform with the bimanual techniqueturing proteins. Later, we used a moist chamber or athan with 1-handed phacoemulsification. A chopperbalanced salt solution to keep the human lens nucleiinserted through the side-port incision stabilized andin their natural form.chopped the nucleus and moved the fragments toward

The corneal structure, thickness, and diameter; thethe phaco tip. The inserted lens nucleus was kept closeanterior chamber depth and volume; the rigidity and

to the phaco tip with high vacuum levels of aboutdiameter of the capsular bag; and the iris structure are

150 mm Hg.the main characteristics that differ between sheep and

The practice session was terminated after emulsifi- human eyes. Implantation of a foldable intraocular lenscation of the human lens nucleus. A new nucleus was in the capsular bag through a corneal incision was possi-replaced through the lateral incision when damage to ble but was not performed because it was not expectedthe cornea and/or iris did not prevent appropriate visual- to provide realistic training practice for human eyes.ization. Three or 4 human lens nuclei were used in The major advantage of this model is the abilityeach sheep eye. to emulsify human cataractous nuclei of the preferred

In 2 trials, the inserted human lens nucleus was hardness, which all models have tried to simulate, individed in the anterior chamber using a vectis and a the same sheep eye at a low cost.spatula under OVD protection. Afterward, lens frag-ments were removed from the eye by the vectis. The Referencesmanual cracking method could also be performed suc- 1. Castellano D, Spraul J, Whitaker TE. A simple, cost-

effective method for practicing phacoemulsification incessfully in this model.

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7. Van Vreeswijk H, Pameyer JH. Inducing cataract intion of cataracts of varying degrees of hardness in humanpostmortem pig eyes for cataract surgery training pur-eyes obtained postmortem for cataract surgeon training.poses. J Cataract Refract Surg 1998; 24:17–18Am J Ophthalmol 2000; 129;557–558

8. Maloney WF, Hall D, Parkinson DB. Synthetic cataract3. Sugiura T, Kurosaka D, Uezuki Y, et al. Creating cataractteaching system for phacoemulsification. J Cataract Re-in a pig eye. J Cataract Refract Surg 1999; 25:615–621fract Surg 1988; 14:218–221

4. Sudan R, Titiyal JS, Rai H, Chandra P. Formalin- 9. Mekada A, Nakajima J, Nakamura J, et al. Cataractinduced cataract in goat eyes as a surgical training model surgery training using pig eyes filled with chestnuts offor phacoemulsification. J Cataract Refract Surg 2002; various hardness. J Cataract Refract Surg 1999; 25:622–28:1904–1906 625

5. Conway MD, Peyman GA. An in vitro cataract model 10. Tolentino FI, Liu H-S. A laboratory animal model forfor practice of cataract surgery. Am Intra-Ocular Implant phacoemulsification practice. Am J Ophthalmol 1975;

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