Gabor Koranyi

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.

Cut and paste: a no suture, small incision approach to pterygium surgery

Aim: Evaluation of the benefits of a new technique for pterygium surgery with respect to postoperative pain and surgery time. Methods: A prospective randomised clinical trial was carried out in 43 patients. 43 eyes were operated for primary nasal pterygium. Autologous conjunctival graft taken at the superotemporal limbus was used to cover the sclera after pterygium excision. After randomisation, in 20 patients the transplant was attached to the sclera with a fibrin tissue adhesive (Tisseel Duo Quick) and in 23 patients with absorbable sutures (7–0 Vicryl Rapid). The Mann-Whitney test was used as statistical analysis. Postoperative pain was graded according to the visual analogue scale (VAS) twice daily during the first week after surgery. Surgery time was noted from the first incision until the lid speculum was removed. Results: The average pain was significantly lower when glue had been used, p<0.05. Average surgery time was 9.7 minutes (range 6–13) for glue and 18.5 minutes (range 12–30) for sutures, p<0.001. No complications occurred. Conclusion: Using glue instead of sutures when attaching the conjunctival transplant in pterygium surgery causes significantly less postoperative pain and shortens surgery time significantly.

Endophthalmitis after cataract surgery: risk factors relating to technique and events of the operation and patient history: a retrospective case-control study.

OBJECTIVE This study aimed to investigate the relationship between postoperative endophthalmitis and current changes in the cataract operative technique. DESIGN A retrospective case-control study. PARTICIPANTS The 22,091 cataract operations performed from 1990 through 1993 at St Eriks Hospital formed the basis for this investigation. In a random fashion, 220 control subjects were selected to be compared with the endophthalmitis cases. MAIN OUTCOME MEASURES Numerous variables pertaining to the cataract extraction procedure and to the ocular and general health of patients with cataracts were analyzed regarding the development of postoperative intraocular infection. Patient age, presence of diabetes or immunosuppression, type of cataract extraction and intraocular lens (IOL), and intraoperative or postoperative complications were the principal variables assessed. RESULTS Fifty-seven patients with endophthalmitis were diagnosed, resulting in an overall frequency of 0.26%. Immunosuppressive treatment (P = 0.019), wound abnormality (P = 0.03), and the use of IOLs without a heparinized surface (P = 0.0023) were the only significant risk factors found in a logistic regression model. CONCLUSIONS The results suggest that cataract operating practice may alter the risk for endophthalmitis in that implanting a heparinized IOL and creating a tight section both seem to provide protection against this dreaded complication. Regarding patient history, an increased susceptibility was found among subjects treated with immunosuppressants. Designing a prophylactic protocol that protects against endophthalmitis more efficiently than did the study prophylaxis of 20 mg of subconjunctival gentamicin, is important not only for this patient subgroup but also for the cataract operated population at large.

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. Eriks 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.

Risk of acute suprachoroidal hemorrhage with phacoemulsification

Purpose: To establish whether small incision cataract surgery with phacoemulsification decreases the risk of acute suprachoroidal hemorrhage (ASCH) compared with traditional nucleus expression by extracapsular cataract extraction (ECCE). Setting: St. Erik Eye Hospital, Stockholm, Sweden. Methods: A retrospective study was done on the incidence of ASCH in cataract surgery between July 1990 and July 1996. During this period, 37,565 cataract extractions (phacoemulsification and ECCE) were performed at St. Erik Eye Hospital, combined procedures excluded. The criteria for diagnosis were the suspicion of ASCH during surgery and a verified diagnosis via an expulsive hemorrhage into the wound (4 cases), postoperative ultrasonic examination (20 cases), or a choroidal mass on performing ophthalmoscopy together with a postoperative history alluding to the diagnosis (2 cases). Results: Twenty‐six eyes were identified with ASCH, including 7 during phacoemulsification and 19 during ECCE. The incidence of ASCH was 0.03% in the 23,213 phacoemulsification cases and 0.13% in the 14,352 ECCE cases. The difference was statistically significant (P = .0003; chi‐square test). Conduslon: Small incision surgery with phacoemulsification decreased the risk of ASCH in cataract surgery compared with the traditional nucleus expression technique.

Prediction of intraocular lens power using the lens haptic plane concept

Purpose: To test algorithms for the preoperative estimation of the lens haptic plane (LHP) and to assess these in terms of predictability of postoperative refraction. Setting: SA Erik’s Eye Hospital, Stockholm, Sweden. Methods: Preoperative axial length, anterior chamber depth (ACID), and cataractous lens thickness were measured in consecutive cases scheduled for phacoemulsification and posterior chamber intraocular lens (IOL) implantation. The algorithms tested used ACID and cataractous lens thickness to estimate LHP. The exact geometry of the IOL was used to calculate postoperative ACID from LHP. Thick lens theory and paraxial ray tracing were used to calculate predicted postoperative refraction. The calculated value was compared with actual refraction 3 to 6 months postoperatively. Results: Mean absolute average error in predicted refraction was 0.38 diopters (D), with 78% of eyes within 0.50 D and 97% within 1.00 D for the best algorithm. Conclusions: The predictability in postoperative refraction found by applying the LHP concept and paraxial ray tracing was excellent. However, the small sample, with its unusually slight variation in axial lengths, did not allow statistically significant differences between different postoperative refraction prediction methods to be demonstrated.

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).

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. Eriks 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.

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. Eriks 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.

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. Eriks 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.