Minimal Invasive Procedures in Strabismus Surgery: A Narrative Review.

Purpose: To review the principles and different techniques of minimally invasive procedures in strabismus surgery. Methods: This is a narrative review on minimally invasive procedures in strabismus surgery including general aspects and different new modifications on conventional strabismus surgery. We reviewed 24 articles published between 1993 and 2020. Results: Minimal invasive procedures could be categorized into two subsets: one which minimizes conjunctival opening size and another which minimizes the muscle manipulations. Different conjunctival approaches have been introduced, such as Cul-de-sac and minimally invasive strabismus surgery incisions. Furthermore, there are different techniques for extraocular muscle weakening, strengthening, and transposition, such as mini-tenotomy, plication, mini-plication, Nishida, and modified Nishida procedures. Moreover, there are some techniques for handling strabismus in heavy eyes with high myopia and using adjustable sutures for strabismus correction. Conclusions: Minimally invasive procedures in strabismus surgery consist of surgical procedures that minimize tissue disruption, speed up rehabilitation, and often ultimate better outcomes. These techniques could be replaced traditional methods to reduce conjunctival and lid swelling in the direct postoperative period.

Comparison of deep sclerokeratodissection, a new variant of nonpenetrating glaucoma surgery, with deep sclerectomy.

PURPOSE: The aim of this study was to evaluate the safety and efficacy of deep sclerokeratodissection (DSKD), a new nonpenetrating technique in glaucoma surgery. MATERIALS AND METHODS: Retrospective comparison between patients treated with DSKS or deep sclerectomy (DS) between 2013 and 2014. In DSKD, the first and only flap is dissected directly into clear cornea with unroofing Schlemm's canal. Beside routine clinical follow-up (visual acuity, intraocular pressure [IOP] readings, slit lamp and fundus examination), postoperative ultrasound biomicroscopy (UBM) investigation and quality of life (QoL) assessment were performed. Statistically significant differences were determined by parametric or nonparametric tests, depending on normality. RESULTS: Twelve (38.7%) DSKDs and 19 (61.3%) conventional DS' were included in this analysis. IOP decreased significantly from 21.5 ± 9.2 mmHg to 6.2 ± 5.4 mmHg on day 1, 13.4 ± 7.7 at 1 month, 12.0 ± 4.1 at 3 months, 12.5 ± 3.1 mmHg at 6 months, and 13.4 ± 4.3 mmHg at 12 months (P < 0.01). No significant difference in the IOP was observed between the two groups at any follow-up (P > 0.1). There was no significant difference in intra- and post-operative complications, the morphology of the surgical site in the UBM as well as in the QoL assessment. CONCLUSION: The results indicate that DSKD is a safe and efficient new variant of nonpenetrating glaucoma surgery. IOP can be lowered as effectively compared to conventional DS, with a similarly low rate of complications. Further reports are necessary to confirm these results.

Intraoperative conversion rate to a large, limbal opening in minimally invasive strabismus surgery (MISS).

BACKGROUND: To evaluate which factors predispose to an intraoperative conversion to the usual limbal approach in minimally invasive strabismus surgery (MISS). METHODS: This study included 451 consecutive patients operated on by one surgeon at Kantonsspital St Gallen, Switzerland, with minimally invasive rectus muscle surgery between February 2003 and December 2007. We evaluated the intraoperative conversion rate to the usual limbal approach over time, and performed a retrospective determination of date of surgery, age of patient, motility of the eye, primary or revision surgery, and the type and dose of surgery in 982 consecutive rectus muscle procedures. RESULTS: In 3.6% (35/982) of MISS procedures, an intraoperative conversion to a large, limbal approach was necessary. The overall conversion rate decreased over time, from 8.4% in 2003 to 0.4% in 2007. The multivariate regression analysis showed a significant negative influence between the date of surgery and the conversion rate (p < 0.005). Muscle resections were associated with a higher conversion rate (p < 0.001). The other evaluated factors had no significant influence on an intraoperative enlargement of the conjunctival opening. CONCLUSIONS: This study confirms the reliability of the new MISS technique, and shows a low conversion rate to the usual limbal approach. The conversion rate decreased over time with increasing surgical experience. Muscle resections were associated with a higher conversion rate, while the age of the patient, the motility of the eye, revision surgery and the dose of surgery had no significant influence on an intraoperative conversion.

Combined horizontal rectus muscle minimally invasive strabismus surgery for exotropia.

OBJECTIVE: To evaluate combined horizontal rectus muscle minimally invasive strabismus surgery (MISS) for exotropia. DESIGN: Case series. PARTICIPANTS: Fifty-two consecutive exotropic patients operated on by 1 surgeon with MISS combined unilateral lateral rectus muscle recession and medial rectus muscle plication. METHODS: Alignment, binocular single vision, conjunctival injection and swelling, and complications during the first 6 postoperative months were recorded prospectively. Conjunctival swelling and injection on the first postoperative day were scored retrospectively and compared with historic controls operated on with combined recession-plication or recession-resection using a limbal approach. RESULTS: Conjunctival swelling and injection were mainly mild on the first postoperative day and less pronounced than after surgery with a limbal approach (comparison of swelling and injection for MISS vs limbal opening recession-plication p < 0.001 and for MISS vs limbal opening recession-resection p < 0.001). A conversion to a limbal approach was necessary in 3/104 (3%, 95% CI 1%-7%) of all muscles. No scleral perforation or other serious complication was observed, and no patient needed a repeat operation within 6 months (0/49, 0%, 95% CI 0%-6%). CONCLUSIONS: This study demonstrates that small-incision, minimal dissection combined recession-plication surgery induces less conjunctival swelling and injection compared with the usual limbal approach.

Impact of low vision on employment.

BACKGROUND: We investigated the influence of self-reported corrected eyesight on several variables describing the perception by employees and self-employed persons of their employment. METHODS: Our study was based on data from the Survey of Health, Ageing and Retirement in Europe (SHARE). SHARE is a multidisciplinary, cross-national database of microdata on health, socioeconomic status, social and family networks, collected on 31,115 individuals in 11 European countries and in Israel. With the help of ordered logistic regressions and binary logistic regressions, we analyzed the influence of perceived visual impairment--corrected by 19 covariates capturing socioeconomic and health-related factors--on 10 variables describing the respondents' employment situation. RESULTS: Based on data covering 10,340 working individuals, the results of the logistic and ordered regressions indicate that respondents with lower levels of self-reported general eyesight were significantly less satisfied with their jobs, felt they had less freedom to decide, less opportunity to develop new skills, less support in difficult situations, less recognition for their work, and an inadequate salary. Respondents with a lower eyesight level more frequently reported that they feared their health might limit their ability to work before regular retirement age and more often indicated that they were seeking early retirement. CONCLUSIONS: Analysis of this dataset from 12 countries demonstrates the strong impact of self-reported visual impairment on individual employment, and therefore on job satisfaction, productivity, and well-being.

A modified technique for rectus muscle plication in minimally invasive strabismus surgery.

PURPOSE: To present a novel, minimally invasive strabismus surgery (MISS) technique for faster and less invasive rectus muscle plication. METHODS: The new plication method is performed without spatula and, therefore, instead of a total dissection (TODI) only a marginal dissection (MADI) of the plicated part of the muscle is performed. Forty patients operated with combined, horizontal MISS rectus muscle recession/MADI plication are retrospectively compared to a similar group of 49 patients, who had MISS recession/TODI plication. The following outcome parameters were analyzed: alignment, binocular single vision, variations in vision, refraction, conjunctival abnormalities, dose-response relationship, and number and types of complications during the first 6 postoperative months. RESULTS: Postoperatively, the conjunctiva over the plicated muscle was less swollen and red with MADI compared to TODI plication (p < 0.01). In esodeviations, there was no significant difference in the dose-response relationship between MADI and TODI plication (1.38 +/- 0.44 vs. 1.44 +/- 0.50 degrees /mm, p > 0.1). In exodeviations, the difference between MADI and TODI plications was not significant either (1.41 +/- 0.38 vs. 1.42 +/- 0.50 degrees /mm, p > 0.1). Also final alignment, binocular single vision, visual acuities, refractive changes, or complications did not differ between the two techniques. CONCLUSIONS: This study demonstrates that MADI plication is feasible and equally effective in comparison with the TODI plication technique when performing MISS. MADI plication, which is performed without spatula, allows to considerably further reduce postoperative conjunctival swelling and redness.

Minimally invasive strabismus surgery technique in horizontal rectus muscle surgery for esotropia.

PURPOSE: To evaluate the minimally invasive strabismus surgery (MISS) technique in combined unilateral horizontal rectus muscle operations for esotropia. METHODS: This study included 61 patients operated by one surgeon with MISS medial rectus muscle recession and lateral rectus muscle plication. Alignment, binocular vision, conjunctival injection and swelling as well as complications during the first 6 postoperative months were recorded prospectively. Conjunctival swelling and injection on postoperative day 1 were scored retrospectively and compared to a study, which included patients operated with a limbal approach. RESULTS: Conjunctival swelling and injection were less pronounced than following surgery with limbal approach (comparison of swelling and injection: p < 0.001 for MISS vs. limbal opening plication and p < 0.001 for MISS vs. limbal opening resection). A conversion to a limbal opening was necessary in 2.4% of muscles. No scleral perforation or other serious complication was observed. CONCLUSIONS: This study indicates that MISS induces less conjunctival swelling and injection compared to the usual limbal approach.

Stimulus parameters for goldmann kinetic perimetry in nonorganic visual loss.

OBJECTIVE: To investigate the influence of the stimulus parameters on perimetry at various distances and draw conclusions for the clinical exploration of nonorganic visual loss. METHODS: Visual field testing using Goldmann kinetic perimetry was performed on 15 healthy volunteers. The I/1e isopter at 33 cm was compared to the I/1e, II/1e and I/2e isopters at 66 cm. The 0/1e isopter at 33 cm was compared to the 0/1e, I/1e and 0/2e isopters at 66 cm. RESULTS: Doubling the examination distance without adjusting the stimulus parameters resulted in significant perimetric visual field constriction. Doubling the stimulus diameter resulted in perimetric visual field expansion by a factor of 2.26 and 3.32 for I/1e and 0/1e, respectively. Increasing stimulus luminance by a factor of 3.17 caused expansion by a factor of 2.15 and 2.32 for I/1e and 0/1e, respectively. CONCLUSIONS: To avoid falsely diagnosing visual field constriction, stimulus parameters need to be adjusted when visual field testing is performed at double distance. Increasing stimulus luminance was more appropriate than augmenting stimulus size.

A new transconjunctival muscle reinsertion technique for minimally invasive strabismus surgery.

PURPOSE: To describe a novel, minimally invasive strabismus surgery (MISS) technique for horizontal rectus muscle recessions, plications, and advancements. METHODS: Subjects for this prospective study were the first 20 consecutive patients who underwent unilateral horizontal rectus muscle surgery with a transconjunctival suturing (TRASU) technique for primary muscle displacements of 4.5 mm or greater or for repeat muscle displacements of 3.0 mm or greater. RESULTS: The TRASU technique was associated with no increase in complication rate and was accomplished through a conjunctival approach with an incision that was smaller by 31% ± 11% compared to incisions for previously described MISS approaches. Of the 19 patients (20 eyes) returning for follow-up, 11 (55%) had minimal redness as the only grossly visible sign of surgery on the first postoperative day. By 6 months postoperatively, visual acuity and refractive error were not significantly different from preoperative values (P > .10 for each). CONCLUSION: The TRASU technique is safe and can be accomplished through a conjunctival incision that averages two-thirds the size of incisions for previously reported MISS techniques.

Computer-based test to quantify the Pulfrich stereophenomenon.

BACKGROUND: Many eye and brain diseases may induce a spontaneous Pulfrich phenomenon (PP), a stereoillusion leading to misjudgments of objects moving in a frontoparallel plane. Since, until now, no simple PP quantification method has been available, a computer pendulum (CP) system was developed and evaluated. METHODS: In 5 normal subjects, PP was induced with different neutral density filters. The resulting retardations were measured with the gold standard (a mechanical pendulum; MP), and compared to a CP, allowing the generation of interocular image phase shifts. RESULTS: A high correlation between MP and CP was found (r = 0.97, p < 0.001; slope 0.91, p > 0.1 for difference with slope 1.0). A multiple linear regression showed a significant influence of the filter density and the subject tested. The type of pendulum (MP or CP) and the side on which the filter was held were nonsignificant. CONCLUSIONS: A CP allowing an interocular image phase shift can be used as an alternative to a MP for quantification of a PP. Thus, this principle would allow the development of software or an Internet-based test for PP quantification. However, in some subjects, the CP will overestimate and in others underestimate the real retardation measured with the MP.

A new stereotest for strabismologists: the covered two pencil test.

PURPOSE: The two pencil test (TPT) checks the ability to perform a simple visual-motor task. The test is only partially based on intact stereopsis, since monocular depth perception clues are involved. To overcome this shortcoming, a new test variant has been developed and tested. METHODS: By covering the tip of the examiner's rod, monocular cues should be drastically reduced. Twenty normal subjects performed the TPT and the covered two pencil test (CTPT) under monocular and binocular conditions. Each test condition was repeated 15 times. Four subjects were retested by three different examiners in order to determine the observer variation. Differences between the accuracy and observer variation of the two test variants under monocular and binocular condition were compared using the paired t test. RESULTS: The average difference between monocular and binocular accuracy was for the TPT 1.26 cm and for the CTPT 2.37 cm (p<0.0005). The average coefficients of variation of both test variants were similar, for the TPT 0.28 and for the CTPT 0.33 (p>0.1). CONCLUSIONS: This study demonstrates that covering the tip of the examiner's rod approximately doubles the differences between monocular and binocular accuracy. Therefore, covering seems to reduce monocular cues and increase the stereoscopic value of the TPT.

Strabismus and employment: the opinion of headhunters.

PURPOSE: The aim of this study was to determine the influence of strabismus on an individual's ability to find employment based on the opinion of Swiss headhunters. METHODS: Forty Swiss headhunters retrieved from a Swiss online telephone directory were interviewed using a validated questionnaire in order to determine if strabismus would have an impact on a person's ability to find employment. Photographs of a strabismic man and woman as well as of other computer-generated facial anomalies could be downloaded from the Internet during the interview. RESULTS: 72.5% of headhunters judged that strabismic individuals would have more difficulties in finding a job than orthotropic persons. These difficulties were judged to be stronger in women than in men (P = 0.006), and in exotropic compared to esotropic persons (P = 0.01). Asked about seven facial anomalies, exotropia was found to have the third and esotropia the fourth (women) or fifth (men) most strongly negative impact on finding employment, after having strong acne and a visible missing tooth. Headhunters judged that persons with strabismus are significantly perceived as less attractive and less intelligent by potential employers. CONCLUSION: Visible strabismus negatively influences individuals' ability to find a job and therefore has an impact on their economic status. Successful strabismus surgery realigns the visual axes, producing a normal facial appearance and therefore eliminating the negative impact of strabismus on employability.

Minimally invasive strabismus surgery (MISS) for inferior obliquus recession.

PURPOSE: To present a novel, minimally invasive strabismus surgery (MISS) technique for inferior obliquus recessions. METHODS: Graded MISS inferior obliquus recessions were performed in 20 eyes of 15 patients by applying two small conjunctival cuts, one at the insertion of inferior obliquus and another where the scleral anchoring of the muscle occurred. RESULTS: The amount of recession was 12.2 +/- 2.3 mm (range 6 to 14 mm). The vertical deviation, which was measured in 25 degrees of adduction, decreased from preoperatively 12.8 degrees +/- 5.6 degrees to 2.7 degrees +/- 2.2 degrees (p < 0.0001) at 6 months. LogMAR visual acuity was preoperatively -0.10 +/- 0.17 and at 6 months -0.14 +/- 0.22 (p > 0.1). In one eye (2.5%) the two cuts had to be joined because of excessive bleeding. Binocular vision improved in eight patients, remained unchanged in six patients, and decreased from 30 to 60 arcsec in one patient (p > 0.1). Conjunctival and lid swelling were hardly visible on the first postoperative day in primary gaze position in 10/20 (50%) of eyes. Five of the eyes (25%) had mild and five (25%) moderate visibility of surgery. One patient out of 15 (7%) needed repeat surgery because of insufficient reduction of the sursoadduction within the first 6 months. The dose-effect relationship 6 months postoperatively for an accommodative near target at 25 degrees adduction was 0.83 degrees +/- 0.43 degrees per mm of recession. CONCLUSIONS: This study demonstrates that small-incision, minimal dissection inferior obliquus graded recessions are feasible and effective to improve ocular alignment in patients with strabismus sursoadductorius.

Minimally invasive strabismus surgery for rectus muscle posterior fixation.

AIMS: To present a novel, minimally invasive strabismus surgery (MISS) technique for rectus muscle posterior fixation. METHODS: This study reports the results of 32 consecutive MISS rectus muscle posterior fixation surgeries performed on 19 patients by applying only two small L-shaped openings where the two retroequatorial scleromuscular sutures were placed. RESULTS: On the first postoperative day, in primary position, redness was hardly visible in 16 eyes (50%) and only moderate redness was visible in 6 eyes (19%). No serious complication occurred. Preoperative visual acuity and refraction remained unchanged at 6 months (p > 0.1). The preoperative convergence excess (n = 13) decreased from 10.3 +/- 4.1 to 5.2 +/- 4.0 degrees at 6 months (p < 0.005). In all patients operated on for gaze incomitance (n = 6) improvement was achieved at 6 months. CONCLUSIONS: This study shows that keyhole minimal-dissection rectus muscle posterior fixation surgery is feasible and effective to improve ocular alignment. The MISS technique seems to be superior in the direct postoperative period since only minimal conjunctival swelling and no corneal complications were observed.

Performance of a new, 3D-monitor based random-dot stereotest for children under 4 years of age.

BACKGROUND: The aim of this study was to determine the performance of a new, 3D-monitor based, objective stereotest in children under the age of four. METHODS: Random-dot circles (diameter 10 cm, crossed, disparity of 0.34 degrees) randomly changing their position were presented on an 3D-monitor while eye movements were monitored by infrared photo-oculography. If > or = 3 consecutive stimuli were seen, a positive response was assumed. One hundred thirty-four normal children aged 2 months to 4 years (average 17+/-15.3 months) were examined. RESULTS: Below the age of 12 months, we were not able to obtain a response to the 3D stimulus. For older children the following rates of positive responses were found: 12-18 months 25%, 18-24 months 10%, 24-30 months 16%, 30-36 months 57%, 36-42 months 100%, and 42-48 months 91%. Multiple linear logistic regression showed a significant influence on stimulus recognition of the explanatory variables age (p<0.00001) and child cooperation (p<0.001), but not of gender (p>0.1). CONCLUSIONS: This 3D-monitor based stereotest allows an objective measurement of random-dot stereopsis in younger children. It might open new ways to screen children for visual abnormalities and to study the development of stereovision. However, the current experimental setting does not allow determining random-dot stereopsis in children younger than 12 months.

Waiting times for cataract surgery in ten European countries: an analysis using data from the SHARE survey.

AIMS: To assess waiting times for cataract surgery and their acceptance in European countries, and to find explanatory, country-specific health indicators. METHODS: Using data from the survey of health, ageing and retirement in Europe (SHARE), waiting times for cataract surgery of 245 respondents in ten countries were analysed with the help of linear regression. The influence of four country specific health indicators on waiting times was studied by multiple linear regression. The influence of waiting time and country on the wish to have surgery performed earlier was determined through logistic regression. Additional information was obtained for each country from opinion leaders in the field of cataract surgery. RESULTS: Waiting times differed significantly (p<0.001) between the ten analysed European countries. The length of wait was significantly influenced by the total expenditure on health (p<0.01) but not by the other country specific health indicators. The wish to have surgery performed earlier was determined by the length of wait (p<0.001) but not by the country where surgery was performed. CONCLUSION: The length of wait is influenced by the total expenditure on health, but not by the rate of public expenditure on health, by the physician density or by the acute bed density. The wish to have surgery performed earlier depends on the length of wait for surgery and is not influenced by the country.

A new 3D monitor-based random-dot stereotest for children.

PURPOSE: Objective testing for random-dot stereovision in preverbal children requires some type of dissociating glasses. Drawbacks of such methods are the alteration of natural visual conditions and sometimes nonacceptance of the glasses. For this reason, a new, natural method for random-dot stereopsis measurement was developed and tested. METHODS: Random-dot circles (diameter 10 cm, crossed disparity of 0.34 degrees ) were generated on an autostereoscopic display and presented to 18 normal children (mean age, 5.1 +/- 1.1 years), 8 with anisometropic amblyopia (mean age, 4.9 +/- 1.3 years), 14 with infantile essential esotropia (mean age, 5.3 +/- 0.7 years), and 16 with primary microstrabismus (mean age, 5.2 +/- 1.4 years). While the position of the stimulus randomly changed among four possible locations, eye positions were recorded by infrared photo-oculography. If two or more consecutive saccades ends corresponded to the stimulus coordinates, a positive response was assumed. The results with the new test were compared with the ability to recognize the Lang I random-dot stereotest. RESULTS: Twenty-four of 26 Lang I-positive children had positive responses (sensitivity of 92.3%), 29 of 30 Lang I-negative children had negative three-dimensional (3D) stimulus responses (specificity, 96.7%). The positive predictive value of the new test was 0.96 (95% CI, 0.79-0.99); the negative predictive value, 0.94 (95% CI, 0.78-0.99); and the overall accuracy, 0.95 (95% CI, 0.85-0.99). CONCLUSIONS: This new 3D monitor-based test allows objective assessment of random-dot stereopsis in children older than 3 years.

Development of visual pursuit in the first 6 years of life.

BACKGROUND: There are few previous investigations on the development of smooth visual pursuit in children. The aim of this study was to determine normative values for the development of horizontal and vertical smooth pursuit in a large number of normal children. METHODS: Eye movements of 358 healthy children aged 6 weeks through 6 years were recorded using infrared photo-oculography. Visual pursuit was elicited with colored squares of 1.2 degrees of visual angle. The stimulus moved horizontally or vertically with constant velocities of 7.5, 15, or 30 degrees/s. RESULTS: Attention time increased with increasing age from 0.54 to 0.77 (P<0.01) and decreased with increasing stimulus velocities (P<0.01). The ratio of time of smooth pursuit to time of smooth pursuit plus saccades increased with increasing age from 0.63 to 0.78 (P<0.01) and decreased with increasing stimulus velocities (P<0.01). For stimulus velocities of 7.5 degrees/s, no significant difference was found between horizontal and vertical gain values. For stimulus velocities of 15 degrees/s and 30 degrees/s, gains for horizontal movements were larger that for vertical (P<0.05). Increasing stimulus speeds were associated with decreasing gains (P<0.05). CONCLUSIONS: This study provides the following normative values for photo-oculography in healthy children aged 6 weeks through 6 years of age: attention time, smooth pursuit time, and gain for three stimulus velocities presented horizontally and vertically. This normative database should help to diagnose pathologic ophthalmological or neuropediatric conditions, to perform screening interventions, and to initiate therapies.

Influence of the Pulfrich phenomenon on driving performance.

BACKGROUND: The Pulfrich stereoillusion occurs spontaneously in diseases inducing asymmetric visual pathway delays. Its influence on driving performance has never been investigated and was, therefore, assessed using a three-dimensional (3D) computer driving simulation. METHODS: A 3D driving scenery of a road with obstacles was visualised on an autostereoscopic 3D display. Seven normal subjects drove at a speed of 6 m/s using a steering wheel and three angles of view of the scenery (0 degrees, 45 degrees to left, and 90 degrees to left) with different interocular delays (25 ms on the right, 25 ms on the left, and no delay). One subject drove the scenery at an angle of 90 degrees without delay and with a delay of 8 ms, 16 ms, and 25 ms on the right and left, respectively, at speeds of 6 m/s, 12 m/s and 18 m/s. RESULTS: Stereo-illusion only influenced car position if the angle of view was 90 degrees (p<0.05). At this angle, increasing car speeds were associated with larger car displacements (delay on right p<0.001, on left p<0.01) and smaller delays with smaller car displacements (p<0.001). CONCLUSIONS: This study showed that Pulfrich phenomenon has an influence on car position only if the viewing angle is 90 degrees. No influence could be found if the driving direction corresponded to the visual axis of the driver. These findings are in agreement with reports of patients with spontaneous Pulfrich phenomenon who indicate that while driving, distances are only misjudged when looking sideways.

Redundant publications in scientific ophthalmologic journals: the tip of the iceberg?

OBJECTIVE: The number of scientific publications is often used to measure scientific achievement. This practice can motivate unethical conduct, such as redundant or duplicate publications, defined as publication of the same scientific contents in more than 1 journal. The aim of this study was to estimate the amount of redundant publications in ophthalmologic journals. DESIGN: Retrospective analysis of published literature. METHODS: We developed an electronic search engine for redundancies to estimate the amount of duplicate publications in scientific journals. When redundancies reached a given degree (matching score), the articles were screened manually based on authors, titles, and abstracts. We applied this method to the 22 433 articles that were published between 1997 and 2000 in 70 ophthalmologic journals indexed by MEDLINE. MAIN OUTCOME MEASURES: The number of duplicate publications with a matching score of 0.6 or more, the number of involved journals, and the number of authors. RESULTS: Redundancies reached a matching score of 0.6 or more in 13 967 pairs of articles. Out of them, a sample of 2210 was reviewed manually. We found 60 redundant articles and estimated that 1.39% of the publications were redundant. Thirty-two journals and an estimate of 1092 authors were involved. In 5% of cases, the scientific conclusions were modified. CONCLUSIONS: Because of the restrictive selection process, the impracticability of detecting all redundant publications, and the estimated amount of duplicates increases with lower matching scores, we regard our estimate to be the tip of the iceberg. Duplicate publications have several negative impacts, but neither peer reviewers nor editors can protect their journal from them completely. Several deterrents for duplicate publications are possible, but as long as publications remain the central requirement for academic advancement, a solution seems unlikely. Nevertheless, it is the responsibility of all those who care about objective research and evidence-based medicine to address this problem-not only in ophthalmology.