Laparoscopic skills training and assessment

BACKGROUND

The introduction of laparoscopic techniques to general surgery was associated with many unnecessary complications, which led to the development of skills laboratories to train novice laparoscopic surgeons. This article reviews the tools currently available for training and assessment in laparoscopic surgery.

METHODS

Medline searches were performed to identify articles with combinations of the following key words: laparoscopy, training, curriculum, virtual reality and assessment. Further articles were obtained by manually searching the reference lists of identified papers.

RESULTS

Current training involves the use of box trainers with either innate models or animal tissues; it lacks objective assessment of skill acquisition. Virtual reality simulators have the ability to teach laparoscopic psychomotor skills, and objective assessment is now possible using dexterity-based and video analysis systems.

CONCLUSION

The tools are now available for the development of a structured, competency-based, laparoscopic surgical training programme.

Systematic review of randomized controlled trials on the effectiveness of virtual reality training for laparoscopic surgery

Background

Surgical training has traditionally been one of apprenticeship. The aim of this review was to determine whether virtual reality (VR) training can supplement and/or replace conventional laparoscopic training in surgical trainees with limited or no laparoscopic experience.

Methods

Randomized clinical trials addressing this issue were identified from The Cochrane Library trials register, Medline, Embase, Science Citation Index Expanded, grey literature and reference lists. Standardized mean difference was calculated with 95 per cent confidence intervals based on available case analysis.

Results

Twenty-three trials (mostly with a high risk of bias) involving 622 participants were included in this review. In trainees without surgical experience, VR training decreased the time taken to complete a task, increased accuracy and decreased errors compared with no training. In the same participants, VR training was more accurate than video trainer (VT) training. In participants with limited laparoscopic experience, VR training resulted in a greater reduction in operating time, error and unnecessary movements than standard laparoscopic training. In these participants, the composite performance score was better in the VR group than the VT group.

Conclusion

VR training can supplement standard laparoscopic surgical training. It is at least as effective as video training in supplementing standard laparoscopic training.

Nanoceria as Antioxidant: Synthesis and Biomedical Applications

The therapeutic application of nanomaterials has been a focus of numerous studies in the past decade. Due to its unique redox properties, cerium oxide (ceria) is finding widespread use in the treatment of medical disorders caused by the reactive oxygen intermediates (ROI). The radical-scavenging role of ceria nanoparticles (nanoceria) have been established, as well as the autocatalytic ability of nanoceria to regenerate under various environmental conditions. The synthesis of nanoceria in biocompatible media has also been reported along with cell viability in order to determine the potential use of nanoceria in biomedical applications.

Consensus guidelines for validation of virtual reality surgical simulators

The Work Group for Evaluation and Implementation of Simulators and Skills Training Programmes is a newly formed sub-group of the European Association of Endoscopic Surgeons (EAES). This work group undertook a review of validation evidence for surgical simulators and the resulting consensus is presented in this article. Using clinical guidelines criteria, the evidence for validation for six different simulators was rated and subsequently translated to a level of recommendation for each system. The simulators could be divided into two basic types; systems for laparoscopic general surgery and flexible gastrointestinal endoscopy. Selection of simulators for inclusion in this consensus was based on their availability and relatively widespread usage as of July 2004. Whilst level 2 recommendations were achieved for a few systems, it was clear that there was an overall lack of published validation studies with rigorous experimental methodology. Since the consensus meeting, there have been a number of new articles, system upgrades and new devices available. The work group intends to update these consensus guidelines on a regular basis, with the resulting article available on the EAES website (http://www.eaes-eur.org ).

Development of a virtual reality training curriculum for laparoscopic cholecystectomy

Background

Training within a proficiency-based virtual reality (VR) curriculum may reduce errors during real surgical procedures. This study used a scientific methodology for development of a VR training curriculum for laparoscopic cholecystectomy.

Methods

Inexperienced (had performed fewer than ten laparoscopic cholecystectomies), intermediate (20–50) and experienced (more than 100) surgeons were recruited. Construct validity was defined as the ability to differentiate between the three levels of experience, based on simulator-derived metrics for nine basic skills, four procedural tasks and full laparoscopic cholecystectomy on a high-fidelity VR simulator. Inexperienced subjects performed ten repetitions for learning curve analysis. Proficiency measures were based on the performance of experienced surgeons.

Results

Thirty inexperienced, 11 intermediate and 16 experienced operators were recruited. Eight of nine basic skills and three of four procedural tasks were found to be construct valid. The full procedure revealed significant intergroup differences for time (1541, 673 and 816 s; P = 0·002), movements (1021, 595 and 638; P = 0·006) and path length (2038, 1235 and 1303 cm; P = 0·033). Learning curves plateaued between the second and ninth sessions.

Conclusion

This study shows that it is possible to define and develop a whole-procedure VR training curriculum for laparoscopic cholecystectomy using structured scientific methodology.

Hepatitis E: an overview and recent advances in clinical and laboratory research

Hepatitis E virus (HEV) is a non-enveloped RNA (7.5 kb) virus that is responsible for large epidemics of acute hepatitis and a proportion of sporadic hepatitis cases in southeast and central Asia, the Middle East, parts of Africa and Mexico. Hepatitis E virus infection spreads by the faecal-oral route (usually through contaminated water) and presents after an incubation period of 8-10 weeks with a clinical illness resembling other forms of acute viral hepatitis. Clinical attack rates are the highest among young adults. Asymptomatic and anicteric infections are known to occur. Chronic HEV infection is not observed. Although the mortality rate is usually low (0.07-0.6%), the illness may be particularly severe among pregnant women, with mortality rates reaching as high as 25%. Recent isolation of a swine virus resembling human HEV has opened the possibility of zoonotic HEV infection. Studies of pathogenetic events in humans and experimental animals reveal that viral excretion begins approximately 1 week prior to the onset of illness and persists for nearly 2 weks; viraemia can be detected during the late phase of the incubation period. Immunoglobulin M antibody to HEV (anti-HEV) appears early during clinical illness but disappears rapidly over a few months. Immunoglobulin G anti-HEV appears a few days later and persists for at least a few years. There is no specific treatment available for hepatitis E virus infection. Ensuring a clean drinking water supply remains the best preventive strategy. Recombinant vaccines are being developed that may be particularly useful for travellers to disease-endemic areas and for pregnant women.

Radiation-induced proctosigmoiditis. Prospective, randomized, double-blind controlled trial of oral sulfasalazine plus rectal steroids versus rectal sucralfate

In a prospective study, 37 consecutive patients with radiation-induced proctosigmoiditis were randomized to receive a four-week course of either 3.0 g oral sulfasalazine plus 20 mg twice daily rectal prednisolone enemas (group I, N = 18) or 2.0 g twice daily rectal sucralfate enemas plus oral placebo (group II, N = 19). The two groups were comparable with respect to demographic features, duration of symptoms, and clinical and endoscopic staging of the disease. Fifteen patients in group I and 17 in group II completed the trial. At four weeks, both groups showed significant clinical improvement (P less than 0.01 for group I and P less than 0.001 for group II) and endoscopic healing (P less than 0.01 for group I and P less than 0.001 for group II). When the two groups were compared, sucralfate enemas showed a significantly better response as assessed clinically (P less than 0.05), although endoscopically the response was not statistically different (P greater than 0.05). We conclude that both treatment regimens are effective in the management of radiation proctitis. Sucralfate enemas give a better clinical response, are tolerated better, and because of the lower cost should be the preferred mode of short-term treatment.

The simulated operating theatre: comprehensive training for surgical teams

Surgical excellence is traditionally defined in terms of technical performance, with little regard for the importance of interpersonal communication and leadership skills. Studies in the aviation industry have stressed the role of human factors in causing error and, in an attempt to reduce the occurrence of adverse events, led to the organisation of simulation based training scenarios. Similar strategies have recently been employed for the surgical team with the development of a simulated operating theatre project. This enables technical and non-technical performance of the surgeon and circulating staff to be assessed by experts situated in an adjacent control room, and provides an opportunity for constructive feedback. The scenarios have good face validity and junior surgeons can benefit from the process of learning new technical skills in a realistic environment. The effect of external influences such as distractions, new technology, or a crisis scenario can also be defined, with the ultimate aim of reducing the number of adverse events arising in the real operating room.

Virtual Reality Simulation Training can Improve Inexperienced Surgeons' Endovascular Skills

PURPOSE

The aim of this study was to evaluate virtual reality (VR) simulation for endovascular training of surgeons inexperienced in this technique.

METHODS

Twenty consultant vascular surgeons were divided into those who had performed >50 endovascular procedures (e.g. aortic and carotid stent) as primary operator (n=8), and those having performed <10 procedures (n=12). To test for endovascular skill rather than procedural knowledge, all subjects performed a renal artery balloon angioplasty and stent procedure. The simulator uses real tools with active force feedback, and provides a realistic image of the virtual patient. Surgeons with endovascular skills performed two repetitions and those without completed six repetitions of the same task. The simulator recorded time taken for the procedure, the amount of contrast fluid used and total fluoroscopy time.

RESULTS

Initially, surgeons with endovascular skills were significantly faster (median 571.5 vs. 900.0 s, p=0.039) and used less contrast fluid (19.1 vs. 42.9 ml, p=0.047) than inexperienced operators, though differences for fluoroscopy time were not significant (273 vs. 441 s, p=0.305). Over the six sessions, the inexperienced group made significant improvements in performance for time taken (p=0.007) and contrast fluid usage (p=0.021), achieving similar scores at the end of the training program to the experienced group.

CONCLUSIONS

Surgeons with minimal endovascular experience can improve their time taken and contrast usage during short-phase training on a VR endovascular task. VR simulation may be useful for the early part of the learning curve for surgeons who wish to expand their endovascular interests.

Duration of viraemia and faecal viral excretion in acute hepatitis E

Data on duration of viral excretion and viraemia during hepatitis E virus (HEV) infection are limited. We tested serial stool and serum samples from 20 patients with acute hepatitis E for HEV RNA. Faecal excretion and viraemia in these patients were found to be short lived. In 19 patients, all samples obtained after biochemical resolution of hepatitis tested negative; in the remaining patient, HEV RNA was detected in the serum samples but not in stool after biochemical resolution. Long-term persistence of HEV in body fluids of infected individuals seems to be an unlikely reservoir for transmission of HEV.

Cellular mechanisms of altered contractility in the hypertrophied heart: big hearts, big sparks

To investigate the cellular mechanisms for altered Ca2+ homeostasis and contractility in cardiac hypertrophy, we measured whole-cell L-type Ca2+ currents (ICa,L), whole-cell Ca2+ transients ([Ca2+]i), and Ca2+ sparks in ventricular cells from 6-month-old spontaneously hypertensive rats (SHRs) and from age- and sex-matched Wistar-Kyoto and Sprague-Dawley control rats. By echocardiography, SHR hearts had cardiac hypertrophy and enhanced contractility (increased fractional shortening) and no signs of heart failure. SHR cells had a voltage-dependent increase in peak [Ca2+]i amplitude (at 0 mV, 1330+/-62 nmol/L [SHRs] versus 836+/-48 nmol/L [controls], P<0.05) that was not associated with changes in ICa,L density or kinetics, resting [Ca2+]i, or Ca2+ content of the sarcoplasmic reticulum (SR). SHR cells had increased time of relaxation. Ca2+ sparks from SHR cells had larger average amplitudes (173+/-192 nmol/L [SHRs] versus 109+/-64 nmol/L [control]; P<0.05), which was due to redistribution of Ca2+ sparks to a larger amplitude population. This change in Ca2+ spark amplitude distribution was not associated with any change in the density of ryanodine receptors, calsequestrin, junctin, triadin 1, Ca2+-ATPase, or phospholamban. Therefore, SHRs with cardiac hypertrophy have increased contractility, [Ca2+]i amplitude, time to relaxation, and average Ca2+ spark amplitude ("big sparks"). Importantly, big sparks occurred without alteration in the trigger for SR Ca2+ release (ICa,L), SR Ca2+ content, or the expression of several SR Ca2+-cycling proteins. Thus, cardiac hypertrophy in SHRs is linked with an alteration in the coupling of Ca2+ entry through L-type Ca2+ channels and the release of Ca2+ from the SR, leading to big sparks and enhanced contractility. Alterations in the microdomain between L-type Ca2+ channels and SR Ca2+ release channels may underlie the changes in Ca2+ homeostasis observed in cardiac hypertrophy. Modulation of SR Ca2+ release may provide a new therapeutic strategy for cardiac hypertrophy and for its progression to heart failure and sudden death.

Virtual reality simulation training can improve technical skills during laparoscopic salpingectomy for ectopic pregnancy

OBJECTIVES

To assess the first commercially available virtual reality (VR) simulator to incorporate procedural modules for training of inexperienced gynaecological surgeons to perform laparoscopic salpingectomy for ectopic pregnancy.

DESIGN

Prospective cohort study.

SETTING

Departments of surgery and gynaecology in central London teaching hospitals.

SAMPLE

Thirty gynaecological surgeons were recruited to the study, and were divided into novice (<10 laparoscopic procedures), intermediate (20-50) and experienced (>100) groups.

METHODS

All subjects were orientated to the VR simulator with a basic skills task, followed by performing ten repetitions of the virtual ectopic pregnancy module, in a distributed manner.

MAIN OUTCOME MEASURES

Operative performance was assessed by the time taken to perform surgery, blood loss and total instrument path length.

RESULTS

There were significant differences between the groups at the second repetition of the ectopic module for time taken (median 551.1 versus 401.2 versus 249.2 seconds, P = 0.001), total blood loss (median 304.2 versus 187.4 versus 123.3 ml, P = 0.031) and total instrument path length (median 17.8 versus 8.3 versus 6.8 m, P = 0.023). The learning curves of the experienced operators plateaued at the second session, although greater numbers of sessions were necessary for intermediate (seven) and novice (nine) surgeons to achieve similar levels of skill.

CONCLUSIONS

Gynaecological surgeons with minimal laparoscopic experience can improve their skills during short-phase training on a VR procedural module. In contrast, experienced operators showed nonsignificant improvements. Thus, VR simulation may be useful for the early part of the learning curve for surgeons who wish to learn to perform laparoscopic salpingectomy for ectopic pregnancy.

Systematic review of e-learning for surgical training

BACKGROUND

Internet and software-based platforms (e-learning) have gained popularity as teaching tools in medical education. Despite widespread use, there is limited evidence to support their effectiveness for surgical training. This study sought to evaluate the effectiveness of e-learning as a teaching tool compared with no intervention and other methods of surgical training.

METHODS

A systematic literature search of bibliographical databases was performed up to August 2015. Studies were included if they were RCTs assessing the effectiveness of an e-learning platform for teaching any surgical skill, compared with no intervention or another method of training.

RESULTS

From 4704 studies screened, 87 were included with 7871 participants enrolled, comprising medical students (52 studies), trainees (51 studies), qualified surgeons (2 studies) and nurses (6 studies). E-learning tools were used for teaching cognitive (71 studies), psychomotor (36 studies) and non-technical (8 studies) skills. Tool features included multimedia (84 studies), interactive learning (60 studies), feedback (27 studies), assessment (26 studies), virtual patients (22 studies), virtual reality environment (11 studies), spaced education (7 studies), community discussions (2 studies) and gaming (2 studies). Overall, e-learning showed either greater or similar effectiveness compared with both no intervention (29 and 4 studies respectively) and non-e-learning interventions (29 and 22 studies respectively).

CONCLUSION

Despite significant heterogeneity amongst platforms, e-learning is at least as effective as other methods of training.

Long-term follow-up after pneumatic dilation for achalasia cardia: factors associated with treatment failure and recurrence

BACKGROUND

Though most patients with achalasia cardia (AC) respond to pneumatic dilation (PD), one-third experienced recurrence. Long-term follow-up studies on factors associated with various outcomes are scanty.

METHODS

In this retrospective study, 126 patients (36.5 +/- 14.6 yr, 76 male) with AC (diagnosed by esophagoscopy, barium esophagogram, and/or manometry) were followed up in person or through mail. The median dysphagia-free duration was calculated by Kaplan-Meier analysis. Factors associated with nonresponse and recurrence after PD were determined using univariate and multivariate analyses.

RESULTS

Symptoms were dysphagia (126, 100%), chest pain (21, 17%), regurgitation (61, 48%), weight loss (33, 26%), and pulmonary symptoms (23, 18%); 5 of 126 (4%) had megaesophagus (> or =7 cm). The mean lower esophageal sphincter (LES) pressure was 38.7 +/- 16.8 mmHg. One hundred and fifteen of 126 (91%) patients responded to PD (90 (71%) to first session); 25 of these had recurrence of dysphagia after 15 +/- 17 months. Post-PD chest pain requiring hospitalization occurred in 21 of 126 (17%; one had an esophageal perforation). Post-PD LES pressure, which was assessed in 48 of 126 patients, had decreased by >50% from baseline in 14 of 29 responders, 0 of 11 nonresponders (p= 0.004, chi(2) test), and 5 of 8 relapsers. The median dysphagia-free duration by Kaplan-Meier analysis was 60 months (SE 2.7, 95% CI 54.7-65.3). On univariate analysis, male gender, pulmonary symptoms (nocturnal coughing spell, history of respiratory infection), absence of chest pain, and failure to achieve a reduction in LES pressure >50% after PD were associated with poor outcome; whereas age, grade of dysphagia, regurgitation, megaesophagus, and LES pressure before PD were not. Male gender was associated with poor outcome by multivariate-analysis.

CONCLUSIONS

PD is an effective and safe treatment for AC. Post-PD LES pressure measurement may be helpful in assessing response. Male patients have poorer outcomes following PD.

Systematic review of predictors of surgical performance

Background

Selection criteria for surgical training are not scientifically proven. There is a need to define which attributes predict future surgical performance. The aim of this study was to examine the predictive value of specific attributes that impact on surgical performance.

Methods

All studies assessing the predictive power of specified attributes with regard to outcome measures of surgical performance in MEDLINE, Embase, the Cochrane Central Register of Controlled Trials and Educational Resources Information Centre databases, and bibliographies of selected articles from 1950 to November 2010 were considered for inclusion by two independent reviewers. Information on study identifiers, participant characteristics, predictors assessed, evaluation methods for predictors, outcome measures, results and statistical analysis was collected. Quality assessment was carried out using the Hayden criteria.

Results

Visual–spatial perception correlated with both subjective and objective assessments of surgical performance, including rate of skill acquisition. Visual–spatial perception did not correlate with operative ability in experts, although it did with operative ability at the end of a training programme. Psychomotor aptitude, assessed collectively, correlated with rate of skill acquisition. Academic achievement predicted completion of a training programme and passing end-of-training examinations, but did not predict clinical performance during the training programme.

Conclusion

Intermediate- and high-level visual–spatial perception, as well as psychomotor aptitude, can be used as criteria for assessing candidates for surgical training. Academic achievement is an effective predictor of successful completion of training programmes and should continue to form part of the assessment of surgical candidates.

Objective assessment of gynecologic laparoscopic skills using the LapSimGyn virtual reality simulator

BACKGROUND

Safe realistic training and unbiased quantitative assessment of technical skills are required for laparoscopy. Virtual reality (VR) simulators may be useful tools for training and assessing basic and advanced surgical skills and procedures. This study aimed to investigate the construct validity of the LapSimGyn VR simulator, and to determine the learning curves of gynecologists with different levels of experience.

METHODS

For this study, 32 gynecologic trainees and consultants (juniors or seniors) were allocated into three groups: novices (0 advanced laparoscopic procedures), intermediate level (>20 and <60 procedures), and experts (>100 procedures). All performed 10 sets of simulations consisting of three basic skill tasks and an ectopic pregnancy program. The simulations were carried out on 3 days within a maximum period of 2 weeks. Assessment of skills was based on time, economy of movement, and error parameters measured by the simulator.

RESULTS

The data showed that expert gynecologists performed significantly and consistently better than intermediate and novice gynecologists. The learning curves differed significantly between the groups, showing that experts start at a higher level and more rapidly reach the plateau of their learning curve than do intermediate and novice groups of surgeons.

CONCLUSION

The LapSimGyn VR simulator package demonstrates construct validity on both the basic skills module and the procedural gynecologic module for ectopic pregnancy. Learning curves can be obtained, but to reach the maximum performance for the more complex tasks, 10 repetitions do not seem sufficient at the given task level and settings. LapSimGyn also seems to be flexible and widely accepted by the users.

Experimental studies on subclinical hepatitis E virus infection in cynomolgus macaques

Serial subclinical transmission among susceptible humans may serve as a reservoir of hepatitis E virus (HEV) in areas in which HEV is endemic. This hypothesis was investigated in an experimental primate model. Four groups of 4 cynomolgus macaques each were inoculated intravenously with 10(4)-10(5) (group 1), 10-100 (group 2), and 1-10 (group 3) cynomolgus macaque HEV infectious doses. All 4 animals in group 1 had clinical disease marked by alanine aminotransferase (ALT) elevation, fecal virus excretion, viremia, and seroconversion. Of the animals in groups 2 and 3, only 1 had evidence of biochemical hepatitis, although most had virus excretion and viremia (3 animals each in groups 2 and 3), and evidence of seroconversion (1 animal in group 2 and 3 animals in group 3). Viral genomic titers in stool specimens of animals with or without ALT elevation were similar. Infectivity studies confirmed the viability and transmission potential of the virus excreted by animals without ALT elevation. These data suggest that subclinical HEV infection may represent an HEV reservoir.

Hepatitis E: intrafamilial transmission versus waterborne spread

The relative significance of intrafamilial transmission and continued water contamination in the spread of hepatitis E is not known. To resolve this question, two surveys were conducted during a large bimodal waterborne epidemic of hepatitis E in Kanpur, India, affecting an estimated 79,000 persons: i) April 1991: covering 420 houses (60 houses each in seven municipal wards) selected using multistage sampling and random number tables, and ii) May 1992: covering the same families in five municipal wards with incidence rates exceeding 1.5% in the first survey. The number of affected cases in each family and the time of onset of disease in each case were recorded. The time interval between the first ('index') case and the subsequent ('later') case(s) in each family was calculated. The temporal relationship of the occurrence of cases was correlated with the time of control of water contamination. One hundred and eleven hepatitis cases occurred in the 343 families (with 2018 members) studied. Eighty-one of these were single or first cases in their families. Twenty-two 'later' cases occurred within 2 weeks (minimum incubation period of hepatitis E) of the 'index' cases and could not be due to intrafamilial transmission. Thus, 103 of 111 (92.8%) cases were due to primary waterborne infection. Eight 'later' cases (7.2% of 111) that occurred 2-6 weeks after the index cases could be due either to direct spread or to intrafamilial transmission. No 'later' case occurred more than 6 weeks after the 'index' cases. New cases stopped appearing 9 weeks (upper limit of incubation period of hepatitis E) after steps to check water contamination were taken.(ABSTRACT TRUNCATED AT 250 WORDS)

The assessment of topical nasal drug distribution

The mainstay of treatment of chronic rhinosinusitis is through the administration of topical nasal drugs. The delivery and intranasal distribution of these is therefore of potential clinical significance. Until there is progress in the nasal drug distribution assessment methodology, it will be difficult to improve topical nasal drug delivery, which is known to be suboptimal in many ways. This study reviews intranasal drug delivery assessment methods, the present knowledge and explores future directions for research.

Hepatitis E virus genome in stools of hepatitis patients during large epidemic in north India

Stool samples from patients affected during a large epidemic of hepatitis in north India were examined for the presence of hepatitis E virus (HEV) genome by means of reverse transcription-polymerase chain reaction. 6 of 10 samples studied were positive for the HEV genome, which suggest that HEV caused this large epidemic.

Efficacy and feasibility of stereotactic radiosurgery in the primary management of unfavorable pediatric ependymoma

Stereotactic radiosurgery was given as a boost in the initial radiation management of five children with localized intracranial ependymoma. Preliminary results in young children with high-risk tumors indicate good local control without excessive neurotoxicity.

Use of DNA polymorphisms and the polymerase chain reaction to examine the survival of a human limbal stem cell allograft

PURPOSE

The extent to which limbal epithelial stem cell allografts will repopulate the human corneal ocular surface, and the time frame over which such cells survive, are uncertain. We investigated the survival of donor-derived epithelial cells after limbal stem cell allotransplantation in a patient with bilateral limbal stem cell failure by using short tandem-repeat DNA polymorphisms to distinguish donor and recipient cells.

METHODS

Epithelial cells were harvested by impression cytology from the grafted eye before and at various times after transplantation. DNA was extracted and amplified by the polymerase chain reaction at an informative locus, D8S264.

RESULTS

Cells of donor genotype were present over the grafted areas at the time of surgery but were not detected in the central cornea until 12 weeks postoperatively, indicating that repopulation of the epithelial surface from transplanted limbal stem cells took considerable time. However, by the 20th postoperative week, only recipient-type cells were detected in the grafted eye, despite systemic immunosuppression of the recipient with azathioprine and cyclosporine.

CONCLUSIONS

Discrimination between donor and recipient cells on the ocular surface after limbal allotransplantation was possible using genotypic variation at DNA polymorphic sites (microsatellites). Long-term survival of donor cells after limbal transplantation did not occur in this patient. Detection of DNA polymorphisms amplified by the polymerase chain reaction is a simple, rapid, and noninvasive method of following the course of transplanted cells at the ocular surface.