Julio Narváez

Accuracy of intraocular lens power prediction using the Hoffer Q, Holladay 1, Holladay 2, and SRK/T formulas

PURPOSE: To compare the accuracy of intraocular lens (IOL) power calculations using 4 formulas: Hoffer Q, Holladay 1, Holladay 2, and SRK/T. SETTING: Tertiary care center. METHODS: This study was a retrospective comparative analysis. Immersion ultrasound biometry (axial length, anterior chamber depth, and lens thickness), manual keratometry, and postoperative manifest refraction were obtained in 643 eyes of consecutive patients who had routine uneventful cataract surgery with implantation of 1 of 2 IOLs using the same operative technique by the same surgeon. Biometric data were entered into each of the 4 IOL power calculation formulas, and the results were compared to the final manifest refraction. An optimized lens constant was used for each formula. Results were also stratified into groups of short, average, medium long, and very long axial length <22.0 mm, 22.0 to <24.5 mm, 24.5 to 26.0 mm, and >26.0 mm, respectively). RESULTS: No formula was more accurate than the others as measured by mean absolute error. The formulas were also equally accurate when eyes were stratified by axial length. CONCLUSION: The 4 IOL power formulas provided equivalent refractive results in the entire group of eyes and in the subsets of axial lengths tested.

Treatment of epithelial ingrowth after LASIK enhancement with a combined technique of mechanical debridement, flap suturing, and fibrin glue application.

Purpose: To report a case of clinically significant post-laser in situ keratomileusis (LASIK) epithelial ingrowth successfully treated with a combined technique of mechanical debridement, flap suturing, and fibrin glue application. Methods: A retrospective case report. Results: A 42-year-old female patient underwent LASIK and an enhancement procedure in 1998 and 2002, respectively. Two years after her enhancement, she developed severe, visually significant epithelial ingrowth. Treatment was undertaken using a combination of mechanical debridement, flap suturing, and fibrin glue application. No recurrence was found during a 15-month follow-up period. No adverse effects were seen with this approach. Conclusion: Severe progressive epithelial ingrowth may be treated successfully with a combination of mechanical debridement, flap suturing, and fibrin glue application.

Comparing immersion ultrasound with partial coherence interferometry for intraocular lens power calculation.

BACKGROUND AND OBJECTIVE To compare the utility and accuracy of high-precision immersion ultrasound, partial coherence interferometry, and the IOL Master system (Carl Zeiss Meditec, Dublin, CA) in a tertiary care referral center. PATIENTS AND METHODS Comparative clinical study in a tertiary care, multispecialty, university practice. Participants were consecutive patients scheduled for cataract surgery at Emory Eye Center. Patients underwent biometry using immersion ultrasound, partial coherence interferometry, and the IOL Master system. RESULTS Twenty-two percent of eyes undergoing surgery could not be measured using interferometry. In those eyes measurable by both methods, there was no difference in measurements nor postoperative refractive outcome. Each method had a high repeatability (intraclass correlation coefficient > 0.99) with a high intraclass correlation between methods (intraclass correlation coefficient = 0.99). CONCLUSIONS When it can be used, interferometry is equivalent to immersion ultrasonography regarding biometric accuracy and precision. However, it cannot replace ultrasonography, especially for eyes with dense media opacity.

Comparison of central corneal thickness measurements by ultrasound pachymetry, konan noncontact optical pachymetry, and orbscan pachymetry.

Purpose: To assess the repeatability of two optical techniques for measurement of central corneal thickness and to compare the validity of these techniques with standard ultrasound pachymetry. Methods: Corneal thickness was measured twice with Konan optical pachymetry, Orbscan optical pachymetry, and 3 times by conventional ultrasound pachymetry in 100 eyes of 50 healthy volunteers between the ages of 22 and 74 years. The repeatability of measurements of each instrument was determined and compared. Validity was determined by comparing the means of the first Konan and Orbscan measurements to the mean of standard ultrasound pachymetry. Intraclass correlation coefficients (ICCs) were calculated, and their confidence intervals (CIs) were determined. Results: Repeatability of ultrasound pachymetry had an ICC of 0.905 (95% CI: 0.870-0.932). The Konan pachymeter had an ICC of 0.947 (95% CI: 0.922-0.964), and the Orbscan pachymetry yielded an ICC of 0.972 (95% CI: 0.959-0.981). Validity of Konan pachymetry had an ICC of 0.730 (95% CI: 0.623-0.810). Orbscan pachymetry had an ICC of 0.865 (95% CI: 0.805-0.907). Conclusions: Both of the newer optical methods for determining corneal thickness produced measurements of greater repeatability than the standard ultrasound technique. Orbscan pachymetry provides greater repeatability (P = 0.02) and validity (P = 0.007) than the Konan optical pachymeter.

Case of corneal melting associated with the use of topical nepafenac.

Purpose: To report a case of corneal melting associated with the use of the topical nonsteroidal anti-inflammatory agent Nepafenac. Methods: Case report and literature review. Results: A 62-year-old woman with a complicated ocular history developed corneal melting associated with the use of Nepafenac. On discontinuation of Nepafenac, the melt rapidly resolved. Conclusions: Topical nonsteroidal anti-inflammatory agents have been associated with corneal ulceration and stromal melts. This is, to our knowledge, the first reported case involving the new agent, Nepafenac.

Negative dysphotopsia associated with implantation of the Z9000 intraocular lens

&NA; Uneventful small‐incision cataract surgery was performed in a 70‐year‐old man and a 62‐year‐old woman with implantation of a Tecnis Z9000 intraocular lens (IOL) (Pharmacia). No ocular pathology was present in the patients preoperatively. Unsolicited complaints of negative dysphotopsia were made postoperatively, and the symptoms have persisted for more than 1 year in both patients. Symptomatic negative dysphotopsia may be seen in association with the Z9000 IOL.

Comparison of 2 multiple-measurement infrared pupillometers to determine scotopic pupil diameter

PURPOSE: To compare a monocular and a binocular multiple‐measurement digital infrared pupillometers for measuring scotopic pupil diameter. SETTING: Department of Ophthalmology, Loma Linda University, Loma Linda, California, USA. METHODS: Scotopic pupil size was measured after 1 minute of dark adaptation in 42 eyes of 21 volunteers. Measurements were taken twice each with 2 multiple‐measurement digital infrared pupillometers, the monocular pupillometer (Neuroptics, Inc.), and the binocular pupillometer (P2000D, Procyon, Ltd.) Intraclass correlation coefficients (ICC) and limits of agreement (LOA) were used to measure repeatability and agreement of measures with each instrument and between instruments. The Wilcoxon signed rank test was used to compare variability of measurements within each instrument. RESULTS: The mean scotopic pupil size was 4.79 mm ± 0.95 (SD) with the Procyon and 4.86 ± 0.93 mm with the Neuroptics. Repeatability and agreement tests for the Procyon measures showed the following: ICC, 0.954; 95% confidence interval (CI), 0.916‐0.975; LOA, −0.60 to 0.56; range, 1.16. The Wilcoxon signed rank test of variability gave a Z score of −2.53 (P = .01, 2 tailed). The repeated measures testing with the Neuroptics pupillometer showed the following: ICC, 0.985; 95% CI, 0.972‐0.992; LOA, −0.39 to 0.26; range, 0.64; Z score, −1.15 (P = .25, 2‐tailed). Repeatability and agreement tests for measures between instruments showed the following: ICC, 0.954; 95% CI, 0.916‐0.975; LOA, −0.60 to 0.50; range 1.11. CONCLUSIONS: There was a high repeatability and agreement in scotopic pupil diameter for repeated measures within each device and measurements between the devices. Differences in variability in scotopic pupil diameter evaluated by the Wilcoxon signed rank test were significant only with the Procyon pupillometer.

Intraoperative Cyclorotation and Pupil Centroid Shift During LASIK and PRK

PURPOSE To determine the degree of cyclorotation and centroid shift in the x and y axis that occurs intraoperatively during LASIK and photorefractive keratectomy (PRK). METHODS Intraoperative cyclorotation and centroid shift were measured in 63 eyes from 34 patients with a mean age of 34 years (range: 20 to 56 years) undergoing either LASIK or PRK. Preoperatively, an iris image of each eye was obtained with the VISX WaveScan Wavefront System (Abbott Medical Optics Inc) with iris registration. A VISX Star S4 (Abbott Medical Optics Inc) laser was later used to measure cyclotorsion and pupil centroid shift at the beginning of the refractive procedure and after flap creation or epithelial removal. RESULTS The mean change in intraoperative cyclorotation was 1.48±1.11° in LASIK eyes and 2.02±2.63° in PRK eyes. Cyclorotation direction changed by >2° in 21% of eyes after flap creation in LASIK and in 32% of eyes after epithelial removal in PRK. The respective mean intraoperative shift in the x axis and y axis was 0.13±0.15 mm and 0.17±0.14 mm, respectively, in LASIK eyes, and 0.09±0.07 mm and 0.10±0.13 mm, respectively, in PRK eyes. Intraoperative centroid shifts >100 μm in either the x axis or y axis occurred in 71% of LASIK eyes and 55% of PRK eyes. CONCLUSIONS Significant changes in cyclotorsion and centroid shifts were noted prior to surgery as well as intraoperatively with both LASIK and PRK. It may be advantageous to engage iris registration immediately prior to ablation to provide a reference point representative of eye position at the initiation of laser delivery.

Late-onset traumatic dislocation with central tissue loss of laser in situ keratomileusis flap

Purpose: We report the occurrence and outcome of a severe late-onset traumatic dislocation of a laser in situ keratomileusis (LASIK) flap with loss of central flap tissue. Methods: Case report. Results: A 40-year-old woman underwent uncomplicated bilateral LASIK surgery, followed 5 years later by an enhancement procedure in both eyes. Ocular trauma with a power sander occurred 6 years after LASIK and 1 year after the enhancement procedure. The flap was found to have an almost complete tear from the nasal hinge and a central tissue defect. After irrigating, repositioning, and stabilizing the flap with 2 nylon sutures, a bandage contact lens was placed. The patient was treated with topical antibiotic and steroid drops. Stage 2 diffuse lamellar keratitis developed, which responded to topical treatment. Ten weeks after injury, the patient regained an uncorrected visual acuity of 20/20-1. Conclusion: Late-onset trauma to the LASIK flap can result in flap dehiscence and tissue loss. Prompt and appropriate management can lead to an excellent visual outcome even in severely traumatized dislocated LASIK flaps.

Pupil dilation using a standard cataract surgery regimen alone or with atropine 1.0% pretreatment: Prospective comparative evaluation

PURPOSE: To compare the amount of pupil dilation produced by a set of commonly used preoperative mydriatic agents for cataract surgery, with the same regimen preceded by topical administration of atropine 1.0%. SETTING: Department of Ophthalmology, Loma Linda University, Loma Linda, California, USA. METHODS: In this prospective unmasked study, the baseline pupil size in eyes of volunteers was measured. Pupil size was then measured 30 minutes after instillation of the institutions standard dilation regimen for cataract surgery, which included phenylephrine 2.5%, tropicamide 1.0%, and cyclopentolate 1.0%. Several days later, the subjects returned for repeat measurements after pretreating the study eye(s) with atropine 1.0% 3 times a day the day previously and once on the morning of repeat dilation and measurements. Pupil size was again measured after administration of the standard regimen. RESULTS: The study included 72 eyes of 54 patients. A paired t test showed a statistically significant difference in mean pupil dilation between the standard regimen alone and the standard regimen with atropine 1.0% pretreatment. The mean pupil dilation was 7.3 mm ± 1.2 (SD) with the standard regimen alone and 6.9 ± 1.2 mm with the standard regimen with atropine pretreatment; the difference was statistically significant (P<.001). CONCLUSION: The addition of atropine 1.0% 1 day before administration of a standard preoperative dilating regimen for cataract surgery resulted in a smaller dilated pupil diameter than administration of the standard set of preoperative mydriatic agents alone. Financial Disclosure: No author has a financial or proprietary interest in any material or method mentioned.