Brian S Boxer Wachler

Effect of inferior-segment Intacs with and without C3-R on keratoconus.

PURPOSE: To determine whether corneal collagen cross‐linking with riboflavin (C3‐R) augments the effect of inferior‐segment Intacs (Addition Technology) in the treatment of keratoconus. SETTING: Private practice, Beverly Hills, California, USA. METHODS: A retrospective nonrandomized comparative case series comprised 12 eyes of 9 patients who had inferior‐segment Intacs placement without C3‐R (Intacs‐only group) and 13 eyes of 12 patients who had inferior‐segment Intacs placement combined with C3‐R (Intacs with C3‐R group). The 2 groups were matched preoperatively. All patients had inferior‐segment Intacs placed with the incision in the steep axis of manifest refraction. Corneal collagen cross‐linking with riboflavin was performed after the Intacs segments were inserted. Outcome measures were topographic keratometry values and the lower–upper (L–U) ratio, which is a topographic measure of the degree of keratoconus. Preoperative data were compared to results 1 day postoperatively and measurements at the last postoperative visit. RESULTS: The Intacs with C3‐R group had a significantly greater reduction in cylinder than the Intacs‐only group (P<.05). Steep and average keratometry were reduced significantly more in the Intacs with C3‐R group (P<.05). There was a greater reduction in L–U ratio in the Intacs with C3‐R group (P<.05). CONCLUSION: The addition of C3‐R to the Intacs procedure resulted in greater keratoconus improvements than Intacs insertion alone.

Intacs for keratoconus

PURPOSE To evaluate the efficacy and safety of placement of Intacs in subjects with keratoconus. DESIGN Retrospective, nonrandomized comparative trial. INTERVENTION Intrastromal corneal ring segment implantation. PARTICIPANTS Seventy-four eyes of 50 subjects (41 male and 9 female) were evaluated. The mean age of subjects in the study was 35 years, ranging from 20 to 73 years. Twenty-six subjects underwent single-eye treatment, and 24 subjects had both eyes treated. METHODS A modified Intacs procedure was performed on subjects with keratoconus. Pachymetry was measured at the incision site, and the incision was made at 66% of the corneal thickness. A thicker ring segment was typically placed inferiorly, and a thinner segment was placed superiorly on the basis of a refractive nomogram. MAIN OUTCOME MEASURES Differences between preoperative and postoperative uncorrected visual acuity, best spectacle-corrected acuity, and spherical equivalent. Changes in irregular astigmatism were evaluated with the inferior-superior value from comeotopographic maps, and differences in refractive cylinder groups were studied. RESULTS Preoperative mean best-corrected logarithm of the minimum angle of resolution (LogMAR) visual acuity was 0.41 (20/50 - 1) (standard deviation [SD], +/-0.48), which improved to a postoperative mean of 0.24 (20/32 - 2) (SD, +/-0.31) (two lines of improvement). Preoperative mean uncorrected LogMAR visual acuity was 1.05 (20/200 - 2 1) (SD, +/-0.48), which improved to a mean of 0.61 (20/80-) (SD, +/-0.52) (four lines of improvement) at postoperative follow-up. Preoperative mean best-corrected LogMAR acuity in the corneal scarring group was 0.96 (20/200 + 2) (SD, +/-0.72), which improved to a mean of 0.54 (SD, +/-0.43) (20/63 - 2) (five lines of improvement). Uncorrected mean LogMAR acuity in the eyes with corneal scarring was 1.42 (20/400 - 4) (SD, +/-0.27), which improved to a mean of 1.03 (20/200 - 1) (SD, +/-73) (three lines of improvement). The mean spherical equivalent before surgery was -3.89 diopters (D) (SD, +/-5.16), which was reduced to a mean of -1.46 D (+/-4.11) at the postoperative follow-up. CONCLUSIONS Asymmetric Intacs implantation can improve both uncorrected and best spectacle-corrected visual acuity and can reduce irregular astigmatism in corneas with and without corneal scarring.

Wavefront-Guided LASIK for the Correction of Primary Myopia and Astigmatism A Report by the American Academy of Ophthalmology

OBJECTIVE To describe wavefront-guided (WFG) LASIK for the primary treatment of low to moderate levels of myopia and astigmatism and to examine the evidence on the safety and effectiveness of the procedure in comparison with conventional LASIK. METHODS Literature searches conducted in 2004, 2005, 2006, and 2007 retrieved 209 unique references from the PubMed and Cochrane Library databases. The panel selected 65 articles to review, and of these, chose 45 articles that they considered to be of sufficient clinical relevance to submit to the panel methodologist for review. During the review and preparation of this assessment, an additional 2 articles were included. A level I rating was assigned to properly conducted, well-designed, randomized clinical trials; a level II rating was assigned to well-designed cohort and case-controlled studies; and a level III rating was assigned to case series, case reports, and poorly designed prospective and retrospective studies. In addition, studies that were conducted by laser manufacturers before device approval (premarket approval) were reviewed as a separate category of evidence. RESULTS The assessment describes studies reporting results of WFG LASIK clinical trials, comparative trials, or both of WFG and conventional LASIK that were rated level II and level III. There were no studies rated as level I evidence. Four premarket approval studies conducted by 4 laser manufacturers were included in the assessment. The assessment did not compare study results or laser platforms because there were many variables, including the amount of follow-up, the use of different microkeratomes, and the level of preoperative myopia and astigmatism. CONCLUSIONS There is substantial level II and level III evidence that WFG LASIK is safe and effective for the correction of primary myopia or primary myopia and astigmatism and that there is a high level of patient satisfaction. Microkeratome and flap-related complications are not common but can occur with WFG LASIK, just as with conventional LASIK. The WFG procedure seems to have similar or better refractive accuracy and uncorrected visual acuity outcomes compared with conventional LASIK. Likewise, there is evidence of improved contrast sensitivity and fewer visual symptoms, such as glare and halos at night, compared with conventional LASIK. Even though the procedure is designed to measure and treat both lower- and higher-order aberrations (HOAs), the latter are generally increased after WFG LASIK. The reasons for the increase in HOA are likely multifactorial, but the increase typically is less than that induced by conventional LASIK. No long-term assessment of WFG LASIK was possible because of the relatively short follow-up (12 months or fewer) of most of the studies reviewed.

Evaluation of corneal functional optical zone after laser in situ keratomileusis.

Purpose: To evaluate the corneal functional optical zone (FOZ) after laser in situ keratomileusis (LASIK) using a primary 6.0 mm ablation diameter without a transition zone. Setting: University‐based practice. Methods: In this retrospective study, 76 eyes of 53 patients who had LASIK for myopia were evaluated. The size of the preoperative and postoperative FOZ was compared in each eye. Preoperative refraction, attempted correction, and achieved correction were correlated with the preoperative and postoperative FOZ using regression analysis. Results: After LASIK, the FOZ decreased a mean 1.2 mm ± 0.67 (SD) (P < .0001). The size of the FOZ was correlated with the preoperative manifest refraction, attempted correction, and achieved correction (P < .0001). The FOZ reduction was significantly correlated with the preoperative manifest refraction, attempted correction, and achieved correction (P < .05). Before LASIK, there was no correlation between the FOZ and the preoperative manifest refraction (P =.9427). Conclusions: Spherical aberrations exist within the laser ablation zone and are related to the amount of myopic treatment. This has implications for patients with large pupil diameters under mesopic conditions. Future studies are necessary to understand the implications in patients with high refractive errors.

Normalized Contrast Sensitivity Values

hroughout the history of refractive surgery, therapeutic procedures have been the focus of development. As the scope of treating refrac-tive disorders widens, there is increasing emphasis on diagnostic interventions that can help practitioners evaluate procedures with increased sophistication. It is not uncommon for patients to have visual complaints despite having 20/20 or better uncorrect-ed visual acuity. These occurrences highlight the need for sensitive tests of quality of vision. One study has shown that visual acuity did not significantly change following photorefractive keratecto-my (PRK), although contrast sensitivity was significantly decreased. 1 A mathematical model has shown the value of detecting subtle vision changes with contrast sensitivity. 2 Contrast sensitivity may be the method of choice because it is sensitive to changes in the refractive state, 3,4 but clinicians presently have difficulty using this test, which explains why it has remained predominantly in the research environment. Traditionally, charting the results of contrast sensitivity requires plotting curves on special graph paper (Fig 1). These curves are difficult to interpret in clinical practice, scientific presentation, and publication. Visual acuity, on the other hand, is reference based on the visual angle of resolution with familiar clinical notation, such as 20/20. Therefore, the clinician can understand the meaning of changes in visual acuity. What refractive surgery needs is a normalized notation for contrast sensitivity that is referenced to a normal population and can be incorporated into all contrast sensitivity devices. We introduce a novel method by which we generate a normalized notation of contrast sensitivity for two charts. METHODS AND RESULTS The contrast sensitivity of thirty-eight eyes of 19 healthy myopic individuals (ten male, nine female) was measured with two charts: 1) VectorVision CSV-1000E (VectorVision, Dayton, OH) without room lights and, 2) Stereo Optical F.A.C.T. (Stereo Optical, Chicago, IL) with luminance as per manufacturer guidelines (85 cd/m 2). Mean age was 34 years (range 26 to 44 yr). Mean and (standard deviation) for best spectacle-corrected logMAR visual acuity was-0.105 (SD .05) and spherical equivalent manifest refrac-tion was-3.91 diopters (D) (SD 2.33). The mean and standard deviation log contrast sensitivity values for the VectorVision CSV-1000E and Stereo Optical F.A.C.T. are shown in Table 1. These results are similar to those of a larger sample of over 100 eyes that is part of an ongoing FDA clinical trial. We determined the absolute log values and normalized ratios for the CSV-1000E chart and for the F.A.C.T. chart. The normalized …

Agreement and repeatability of pupillometry using videokeratography and infrared devices

PURPOSE To evaluate the accuracy and repeatability of the pupil-measuring modules of several corneal topography devices. SETTING Department of Ophthalmology, Saint Louis University Eye Institute, St. Louis, Missouri, USA. METHODS In 14 eyes of 7 healthy myopic patients, pupillometry was performed with 3 corneal topography devices and with an infrared pupillometer under luminance-matched conditions for the Placido projection of the topography devices. Pupils were also measured under a mesopic condition. Outcomes were pupil diameters, limits of agreement, and coefficient of repeatability of the topography devices. RESULTS Mean pupil diameter measurements with the Technomed C-Scan, Humphrey Masterview, Alcon EyeMap, and under a mesopic condition were 3.35 mm, 2.96 mm, 2.34 mm, and 5.94 mm, respectively. All pupil diameter measurements differed significantly from one another except those by the Masterview and C-Scan devices. The mean difference between the C-Scan and luminance-matched infrared measurements was 0.74 mm and between the Masterview and luminance-matched infrared measurements, 0.27 mm. The limits of agreement +/- 2 standard deviations was 4.12 mm and 1.56 mm for the C-Scan and Masterview devices, respectively. Coefficients of repeatability were 0.56 mm, 0.46 mm, and 0.44 mm for the C-Scan, Masterview, and EyeMap devices, respectively. CONCLUSIONS Although topography pupillometry was repeatable, it underestimated the largest natural pupil diameter because of the luminance of the Placido rings. The difference in limits of agreement between the C-Scan and Masterview devices may be explained by pupil physiology and the static nature of videokeratoscopy. These results have implications when topography pupillometry is used to assess pupil diameters prior to refractive surgery. We do not recommend using pupil diameters measured by topography to preoperatively determine halo-related safety.

Role of instrument cleaning and maintenance in the development of diffuse lamellar keratitis

OBJECTIVE To determine if instrument cleaning techniques affect the rate of diffuse lamellar keratitis (DLK) after laser in situ keratomileusis (LASIK). DESIGN Retrospective case series. PARTICIPANTS Two hundred ten eyes of 109 patients. METHODS A record review was performed of all patients who underwent LASIK at the Jules Stein Eye Institute from April 1 through June 24, 1999. During the first 6 weeks, the instruments used in LASIK surgery were cleaned according to our conventional protocol. At the end of this 6-week period, the cleaning protocol was modified and used for a subsequent 6-week period. For each eye during the two periods, the status of DLK on the first postoperative day was recorded. MAIN OUTCOME MEASURES Presence of DLK. RESULTS During the first 6-week period, 118 eyes of 60 patients underwent LASIK surgery. In the subsequent 6 weeks, 92 eyes of 49 patients underwent LASIK surgery. The two groups included patients with similar demographic background: gender, age, and target correction. Diffuse lamellar keratitis was present in 13 of 118 eyes (11%) using our conventional protocol. In only 2 of 92 eyes (2%) did DLK develop after the protocol was modified. Using the chi-square test, the difference between the two groups was statistically significant (P = 0.01). CONCLUSIONS Diffuse lamellar keratitis is a fairly uncommon phenomenon after LASIK surgery. Although the cause remains to be elucidated, these results demonstrated a reduced incidence of DLK associated with alteration of cleaning procedures and a decrease in stagnant instrument cleaning fluids. The authors recommend that refractive centers avoid the use of stagnant fluids in their instrument cleaning and sterilizing protocols to minimize the occurrence of DLK outbreaks.

Higher Order Aberrations and Relative Risk of Symptoms After LASIK

PURPOSE To understand what level of higher order aberrations increases the relative risk of visual symptoms in patients after myopic LASIK. METHODS This study was a retrospective comparative analysis of 103 eyes of 62 patients divided in two groups, matched for age, gender, pupil size, and spherical equivalent refraction. The symptomatic group comprised 36 eyes of 24 patients after conventional LASIK with different laser systems evaluated in our referral clinic and the asymptomatic control group consisted of 67 eyes of 38 patients following LADARVision CustomCornea wavefront LASIK. Comparative analysis was performed for uncorrected visual acuity (UCVA), best spectacle-corrected visual acuity (BSCVA), contrast sensitivity, refractive cylinder, and higher order aberrations. Wavefront analysis was performed with the LADARWave aberrometer at 6.5-mm analysis for all eyes. RESULTS Blurring of vision was the most common symptom (41.6%) followed by double image (19.4%), halo (16.7%), and fluctuation in vision (13.9%) in symptomatic patients. A statistically significant difference was noted in UCVA (P = .001), BSCVA (P = .001), contrast sensitivity (P < .001), and manifest cylinder (P = .001) in the two groups. The percentage difference between the symptomatic and control group mean root-mean-square (RMS) values ranged from 157% to 206% or 1.57 to 2.06 times greater. CONCLUSIONS Patients with visual symptoms after LASIK have significantly lower visual acuity and contrast sensitivity and higher mean RMS values for higher order aberrations than patients without symptoms. Root-mean-square values of greater than two times the normal after-LASIK population for any given laser platform may increase the relative risk of symptoms.

Agreement and repeatability of infrared pupillometry and the comparison method

OBJECTIVE To evaluate the accuracy and repeatability of the widely used comparison method of measuring pupil size. DESIGN Cross-sectional study. PARTICIPANTS Fourteen eyes of seven healthy myopic subjects were examined. INTERVENTION Two examiners made two repeated measures of pupil diameters of 14 eyes using Rosenbaum card comparison pupillometry and infrared pupillometry. Subjects fixated on a distant visual acuity chart, and pupils were measured under three luminance conditions. The agreement and inter-rater repeatability of both methods were determined. MAIN OUTCOME MEASURES Outcomes were pupil diameters, limits of agreement, and coefficient of repeatability of two examiners. RESULTS The mean difference between the two techniques ranged from 0.3 to 0.5 mm. The limits of agreement within two standard deviations ranged from 2.4 to 2.8 mm. Coefficient of repeatability ranged from 0.6 to 1.4 mm for infrared pupillometry and 1.0 to 1.2 mm for Rosenbaum pupillometry. Inter-rater repeatability of Rosenbaum pupillometry was consistently pupil diameter biased. Pupil diameters measured with the Rosenbaum method were consistently larger than diameters measured with the infrared technique for both examiners under all luminance conditions. CONCLUSIONS Results indicate that although the mean difference in techniques was small, the range of the agreement between the Rosenbaum and the infrared techniques was large. The Rosenbaum method consistently overestimated pupil diameters and was subject to inter-rater repeatability bias. Rosenbaum pupillometry may not be appropriate when accurate pupil measurements are required. The results have implications for many clinical trials in ophthalmology, including those evaluating refractive surgery that use Rosenbaum comparison pupillometry.

Role of clearance and treatment zonesin contrast sensitivity: Significance in refractive surgery

PURPOSE To evaluate the relationship between contrast sensitivity, surgical treatment zone, and clearance (ablation or clear zone-pupil diameter) in photorefractive keratectomy (PRK) and radial keratotomy (RK). SETTING Saint Louis University Eye Institute, St. Louis, Missouri, and Hunkeler Eye Center, Kansas City, Missouri, USA. METHODS Thirteen patients had PRK and 20, RK. Contrast sensitivity was measured with the Stereo Optical F.A.C.T. (F.A.C.T.) and VectorVision CSV-1000 (VV) charts. Pupils were measured with the Rosenbaum card. RESULTS In the PRK group, VV contrast sensitivity at 6 and 12 cycles per degree (cpd) correlated with the ablation zone (r2 = 0.18 and 0.22, respectively), while visual acuity and F.A.C.T. contrast sensitivity did not correlate. In the RK group, both VV and F.A.C.T. contrast sensitivity at 6 cpd correlated with clearance (r2 = 0.29 and 0.12, respectively). Pupils were larger with the VV test than with the F.A.C.T. chart because ambient chart luminance was less in the former. CONCLUSION Contrast sensitivity is likely a more sensitive indicator of visual function than acuity in refractive surgery. The VV system unmasks aberrations from the transition zone of ablated and unablated cornea in PRK. Larger samples are needed to determine the critical ablation clearance of the pupil to avoid loss of visual function.