Learning curve in the Cut and Paste method for surgery of primary pterygium.

PURPOSE: To evaluate the learning curve for the surgery of primary nasal pterygium with conjunctival autograft using fibrin adhesive (the Cut and Paste method). METHODS: The outcomes of the first consecutive 120 primary pterygium surgery cases for two surgeons (groups A and B) were investigated retrospectively and compared with the first (group C) and second (group D) 120 cases of GK. A and B were previously inexperienced in pterygium surgery. Outcome variables were surgery time, complications, the number and the temporal distribution of the recurrences. The statistics used were moving averages of the recurrences, Scheffé's test of means, learning curve analysis according to Wright and logarithmic curve fitting to operation time data. The impact of age and sex on recurrences was tested using t-tests and chi-square tests. RESULTS: The mean surgery time was 17 min for A, 13 min for B and 13 min for GK. There was a certain learning curve slope in operation time in groups A and C. The postoperative complications were few and acceptable. There were ten (8.9%) recurrences in group A, eight (6.8%) in group B, six (5.5%) in group C and five (4.6%) in group D. The temporal distribution of the recurrences did not show any learning curve. Age and sex had no significant correlation with recurrence rate or surgery time (data not shown). CONCLUSIONS: Our study indicates that the Cut and Paste technique is easy to learn and master. We did not find a significant learning curve regarding surgery time, recurrences or complications. In a clinical setting, it is beneficial to let a few, otherwise experienced eye surgeons learn the technique.

Intraoperative mitomycin C versus autologous conjunctival autograft in surgery of primary pterygium with four-year follow-up.

PURPOSE: To compare the 4-year outcome of primary pterygium excision using intraoperative mitomycin C (MMC) with suturing a free conjunctival autograft (CA). METHODS: A total of 115 eyes with nasal primary pterygium of 115 patients were included in the study. After randomization into two groups, the eyes were operated on by a single surgeon (GK). After excision of the pterygium, 56 eyes received 0.04% MMC intraoperatively on the bare sclera for 3 min and 59 eyes received a free CA sutured using 7-0 Vicryl. Postoperative follow-up was 4 years. Main outcome measures were recurrences, re-operations, surgery time, complications, visual acuity and astigmatism. Statistical evaluation was performed with the chi-squared test. RESULTS: The recurrence rate was 38% in the MMC group and 15% in the CA group (p < 0.05). The re-operation rate of the recurrences was 53% in the MMC group and 29% in the CA group. Average surgery time was 13 minutes (range: 6-22 min) in the MMC group and 26 min (range: 18-32 min) in the CA group (p < 0.01). There was no significant change in best-corrected visual acuity and astigmatism. One major complication occurred in each group. The most frequently observed complication was delayed epithelial healing (40%) and mild scleral thinning (20%) in the MMC group and suture-related inflammation in the CA group (10%). CONCLUSION: Pterygium surgery including free autologous conjunctival grafting is associated with fewer recurrences, re-operations and complications than using the bare sclera technique together with single-dose intraoperative MMC.

Clinical application of the lens haptic plane concept with transformed axial lengths.

PURPOSE: To clinically evaluate the lens haptic plane (LHP) concept in combination with thick-lens ray tracing for intraocular lens (IOL) power calculation. SETTING: St. Erik's Eye Hospital, Stockholm, Sweden. METHODS: Prospective study of normal cataract cases implanted with Pharmacia CeeOn 809C IOL. Axial length was measured by A-scan. The measured value was first transformed by addition of a constant value to correct for systematic error. Using the transformed axial length and corneal radius measured by keratometry, the LHP position was determined. Knowing the IOL design and the power implanted, expected refractive outcome was calculated and compared to manifest refraction at 6 weeks in terms of mean absolute error (MAE). Thick-lens ray tracing in the paraxial limit was used for the optical calculation. RESULTS: The mean transformed axial length was 23.87 mm. An LHP position algorithm in linear terms of transformed axial length and corneal radius gave an MAE of 0.38 D. There was no trend with axial length. On the present data, the Holladay 1, Hoffer Q, and SRK/T formulas produced MAEs of 0.39 D, 0.39 D, and 0.41 D, respectively, with optimized formula constants. The differences were not statistically significant (P > .05). CONCLUSIONS: The LHP concept in combination with thick-lens ray tracing achieved MAE comparable to that with currently used formulas. The lack of trend with axial length is important for patients with short and long eyes.

The cut-and-paste method for primary pterygium surgery: long-term follow-up.

OBJECTIVE: To evaluate the recurrence rate, reoperation rate and side-effects of a novel technique for pterygium surgery. DESIGN: Retrospective study. PARTICIPANTS: The study included 461 eyes of 381 patients operated for primary nasal pterygium by the same surgeon between 1994 and 2003 and followed for 23 +/- 20 months (range 6-112 months). METHODS: Autologous conjunctival grafts harvested at the superotemporal limbus were used to cover the sclera after pterygium excision. Using a retrospective chart review, the outcome after attaching the transplant to the sclera with a fibrin tissue adhesive (n = 325) was compared to the outcome after graft attachment using absorbable sutures (n = 136). MAIN OUTCOME MEASURES: Recurrence rate, reoperation rate and complications. RESULTS: The recurrence rate was 5.3% in the glue group and 13.5% in the suture group (p = 0.01). The reoperation rates were 1.2% and 3.3%, respectively (p = 0.31). Complications, such as transient transplant oedema and persistent corneal epithelial defects, occurred equally in both groups. CONCLUSION: Using a fibrin tissue adhesive instead of sutures when attaching the conjunctival transplant in primary pterygium surgery results in a significantly lower recurrence rate.

Comparison of 2 A-scans.

PURPOSE: To compare 2 A-scan instruments with regard to differences in measured results for the same patient sample. SETTING: St. Erik's Eye Hospital, Stockholm, Sweden. METHODS: In a study to evaluate the lens-haptic plane concept of intraocular lens (IOL) power calculation, 148 patients eligible for cataract surgery were measured with 2 different A-scan instruments (BVI Axis and Sonomed 1500). The axial length (AL), anterior chamber depth (ACD), and lens thickness (LT) results were analyzed for systematic differences and random errors. RESULTS: The Sonomed 1500 measured systematically longer than the BVI Axis for AL (0.41 mm) and ACD (0.28 mm), although the correlation was good (r = 0.99 and r = 0.87, respectively). The LT correlated poorly (r = 0.18) and showed no systematic trend. The relative random errors (standard deviations) in ACD (7.2%) and LT (18.6%) were larger than that of the AL (0.8%). The systematic difference in the AL corresponds to a 1.0 diopter difference in the A-constant. CONCLUSIONS: The large random errors in the ACD and LT reduce their value as predictors of postoperative IOL position in formulas that use them. Systematic differences in AL can be large enough to require separate formula constants for different pieces of equipment. If this is the situation in 1 setting, there is a risk of mistakes. This confusion could be avoided if there were an agreed standard and a universal calibration procedure for instruments intended for AL measurement.

Reduction of trend errors in power calculation by linear transformation of measured axial lengths.

PURPOSE: To find a method to improve the refractive outcome in short eyes and long eyes without sacrificing the outcome in normal eyes. SETTING: St. Erik's Eye Hospital, Stockholm, Sweden. METHODS: In a prospective study, 148 patients eligible for cataract surgery were measured with 2 different A-scans (BVI Axis, B.V. International; Sonomed 1500, Sonomed Inc.). Refraction was determined 6 weeks postoperatively. The postoperative refraction was compared with the refraction predicted by the Holladay 1, Hoffer Q, and SRK/T formulas; formula constants were optimized to give a zero mean error. The mean absolute error (MAE) was used as an outcome measure. RESULTS: The BVI Axis measured consistently shorter than Sonomed 1500. The mean axial lengths (ALs) were 23.033 mm and 23.435 mm, respectively. With the BVI Axis, an MAE of 0.44 diopter (D), 0.44 D, and 0.47 D was obtained, with the Holladay 1, Hoffer Q, and SRK/T formulas, respectively, with a trend toward undercorrecting short eyes and overcorrecting long eyes. The MAE with the Sonomed 1500 was 0.38 D, 0.39 D, and 0.40 D, respectively. By adding 0.402 mm to each measured value in the BVI Axis data set, the mean AL was transformed to 23.435 mm. With the transformed data, the MAE improved to 0.42 D, 0.43 D, and 0.44 D, respectively, with a reduced trend toward undercorrection and overcorrection. The 0.04 D difference between the instruments, although not statistically significant, may depend on measurement precision. Extending the concept of transformation, a minimum MAE of 0.41 D was obtained with the Holladay 1 at a mean AL of 24.0 mm, 0.43 D with Hoffer Q at 23.9 mm, and 0.40 D with SRK/T at 24.4 mm. The trend toward undercorrection and overcorrection was eliminated at the optimum for each formula. CONCLUSIONS: There were systematic differences in measured AL depending on equipment. Thus, the calculated powers differed and caused error in the degree of compliance between the labeled formula constant of an intraocular lens and the equipment used. Although personalization of formula constants reduces the mean error, in general a trend toward undercorrection of short eyes and overcorrection of long eyes will persist. Transforming the AL scale can eliminate the trend error and improve the overall refractive outcome. Transformation to a population mean AL of about 24.0 mm was close to optimum for the 3 formulas.

A new intraocular lens design to reduce spherical aberration of pseudophakic eyes.

PURPOSE: The aim of this study was to design and evaluate in the laboratory a new intraocular lens (IOL) intended to provide superior ocular optical quality by reducing spherical aberration. METHODS: Corneal topography measurements were performed on 71 cataract patients using an Orbscan I. The measured corneal surface shapes were used to determine the wavefront aberration of each cornea. A model cornea was then designed to reproduce the measured average spherical aberration. This model cornea was used to design IOLs having a fixed amount of negative spherical aberration that partially compensates for the average positive spherical aberration of the cornea. Theoretical and physical eye models were used to assess the expected improvement in optical quality of an eye implanted with this lens. RESULTS: Measurements of optical quality provided evidence that if this modified prolate IOL was centered within 0.4 mm and tilted less than 7 degrees, it would exceed the optical performance of a conventional spherical IOL. This improvement occurred without an apparent loss in depth of focus. CONCLUSION: A new IOL with a prolate anterior surface, designed to partially compensate for the average spherical aberration of the cornea, is intended to improve the ocular optical quality of pseudophakic patients.

Prophylactic intracameral cefuroxime. Efficacy in preventing endophthalmitis after cataract surgery.

PURPOSE: To evaluate the efficacy of prophylactic intracameral cefuroxime in preventing endophthalmitis in cataract surgery. SETTING: Department of Ophthalmology, St. Eriks Hospital, Stockholm, Sweden. METHODS: In a noncontrolled retrospective observational study, all cases of recorded postoperative endophthalmitis were related to the total number of uncombined cataract procedures from January 1996 to December 2000. RESULTS: Twenty cases of postoperative endophthalmitis occurred in 32180 procedures, yielding an overall rate of 0.06%. Cefuroxime-resistant organisms accounted for 12 of 13 culture-positive cases, and enterococci were the most common etiology. CONCLUSIONS: Intracameral cefuroxime 1 mg appeared to effectively inhibit sensitive bacterial strains and was associated with a low frequency of postoperative endophthalmitis. The causative organisms of future incidents of postoperative endophthalmitis will determine whether the present protocol must be reappraised.

Anterior chamber depth measurement: a-scan versus optical methods.

PURPOSE: To evaluate methods of measuring anterior chamber depth (ACD) before and after cataract surgery. SETTING: St. Erik's Eye Hospital, Stockholm, Sweden. METHODS: A-scan (BVI Axis) and Scheimpflug imaging (Nidek EAS-1000) were used to measure ACD preoperatively and 6 and 18 weeks after phacoemulsification with implantation of a poly(methyl methacrylate) (PMMA) intraocular lens (IOL) in 23 patients. Because of a large systematic difference between the 2 methods, measurement with Orbscan (Orbtek) and optical pachymetry (Haag-Streit) were included when measurements were repeated 36 weeks postoperatively. A t test for paired observations was used for statistical analysis. RESULTS: Preoperatively, the mean A-scan measurements were significantly shorter than the Scheimpflug values: 3.05 mm +/- 0.36 (SD) and 3.37 +/- 0.35 mm, respectively (P < .001). At 6 weeks, the difference was more pronounced: 3.73 +/- 0.26 mm and 4.65 +/- 0.33 mm, respectively (P < .001). At 36 weeks, the A-scan and Scheimpflug values remained unchanged. The results of the Scheimpflug measurements were confirmed with optical pachymetry and Orbscan analysis. CONCLUSIONS: There was good agreement between results obtained with 3 methods based on optical principles. Considering the basic and simple measurement principle of these instruments, they appear to provide the correct result. The A-scan equipment used in this study is unsuitable for determination of ACD in eyes with PMMA IOLs.