Comparison of early visual outcomes after low-energy SMILE, high-energy SMILE, and LASIK for myopia and myopic astigmatism in the United States.

PURPOSE: To compare uncorrected distance visual acuities (UDVAs) and induced higher-order aberrations (HOAs) in the early postoperative period between low-energy (LE) small-incision lenticule extraction (SMILE), high-energy (HE) SMILE, and femtosecond laser-assisted laser in situ keratomileusis (FS-LASIK) procedures. SETTING: University based refractive surgery center. STUDY DESIGN: Retrospective cohort study. METHODS: Records of patients who underwent SMILE or FS-LASIK were retrospectively reviewed. SMILE patients were separated into 2 groups: HE settings (125 nJ, 3.0 µm spot spacing) and LE settings (125-130 nJ, 4.5 µm spot spacing). UDVA was measured at postoperative day (POD) 1. Corneal HOAs and UDVA were measured at postoperative month (POM) 1. Induced spherical aberration, vertical coma, horizontal coma, total coma, and total HOAs were calculated. RESULTS: The study included 147 eyes of 106 patients, 49 in each group. For SMILE patients, the difference in mean UDVA at POD1 was highly statistically significant in favor of the LE group (-0.003 vs 0.141, P < .0001). No significant difference in mean UDVA at POD1 was noted between the LE group and FS-LASIK group (-0.003 vs -0.011, P = .498). Induced change in spherical aberration was less in LE SMILE than that in FS-LASIK (0.136 vs 0.186 µm, P = .02) at POM1. No significant differences in POM1 mean UDVA (-0.033 vs -0.036) or induced change in all other HOAs were noted between LE SMILE and FS-LASIK. CONCLUSIONS: LE settings were associated with significantly improved POD1 UDVA. POD1 and POM1 UDVA were comparable with those of FS-LASIK. Spherical aberration induction was less with LE SMILE than that with FS-LASIK, whereas all other induced HOAs were comparable with FS-LASIK.

Method for IOL Power Calculation in the Second Eye of Patients With Previous Keratorefractive Surgery.

PURPOSE: To describe and evaluate a method for calculating intraocular lens (IOL) power in the second operative eye of patients with a history of keratorefractive surgery. METHODS: All eyes had undergone cataract surgery by a single surgeon from 2015 to 2018. Postoperative outcomes on the first eye (eg, IOL power implanted and postoperative refractive error) were used to back calculate a "Real K" for the first eye. The difference (delta) between the second and first eye topographic simulated keratometry values was then added to the first eye Real K to calculate the second eye Real K. This Real K value was inputted into the Holladay IOL Consultant software as an "alternate K" to derive an accurate IOL power for the second eye. Mean absolute error, mean error, and percentage of eyes on target using the Delta K method were compared with results obtained with intraoperative abserrometry and the Haigis-L and Barrett True-K No History formulas. RESULTS: The mean error for the Delta K method was significantly better than the Haigis-L (P = .00001) and Barrett True-K No History (P = .027) formulas, and on par with intra-operative aberrometry (P = .25). The mean absolute error of the Delta K method was significantly better than the Haigis-L formula (P = .03). The Delta K mean absolute error was on par with intraoperative aberrometry (P = .81) and the Barrett True-K No History formula (P = .56). CONCLUSIONS: The Delta K mean absolute error is comparable to the Barrett True-K No History formula. The mean error is lower than that calculated with the Barrett True-K No History formula and comparable to intraoperative aberrometry. [J Refract Surg. 2020;36(12):826-831.].

Prevention and management of refractive prediction errors following cataract surgery.

Patient satisfaction after modern day cataract surgery requires excellent surgical technique but increasingly demands superior refractive outcomes as well. In many cases, there exists an expectation from patients, as well as surgeons, to achieve emmetropia after cataract surgery. This is particularly true in patients electing premium intraocular lens technology to correct astigmatism and presbyopia to minimize spectacle dependence. Despite continued advances in preoperative and intraoperative diagnostics, refractive planning, and surgical technology, residual refractive error remains a primary source of dissatisfaction after cataract surgery. The need to enhance refractive outcomes and treat residual astigmatic or spherical refractive errors postoperatively becomes paramount to meeting the expectations of patients in their surgical outcome. This article reviews the potential preoperative and intraoperative pitfalls that can be the source of refractive error, the various options to enhance refractive outcomes, and potential future technologies to limit residual refractive error after cataract surgery.

A Technique to Reduce Incidence of Opaque Bubble Layer Formation During LASIK Flap Creation Using the VisuMax Femtosecond Laser.

PURPOSE: To identify risk factors for opaque bubble layer (OBL) formation and compare the incidence of OBL using a cone modification technique versus the original technique for LASIK flap creation using the VisuMax laser (Carl Zeiss Meditec, Jena, Germany). METHODS: This retrospective study examined videos of flap creation using the VisuMax laser to identify OBL occurrence. Eyes were divided into three groups: eyes where OBL occurred using the original technique (OBL group), eyes where OBL did not occur using the original technique (no OBL group), and eyes in which the cone modification technique was used for LASIK flap creation (larger flap diameter) (cone modification technique group). Preoperative measurements including simulated keratometry (flat and steep) values, white-to-white distance (WTW), pachymetry, patient age and gender, amount of correction, flap parameters, energy setting, corneal hysteresis, and corneal resistance factor were analyzed to identify parameters with statistical difference between the OBL and no OBL groups. Incidence of OBL was compared between the original and cone modification techniques. RESULTS: OBL incidence was significantly lower with the cone modification technique (7.6%; 7 of 92 eyes) than with the original technique (28.8%; 34 of 118 eyes) (Fisher's exact test, P = .0009). Factors identified with a significant difference between eyes with and without OBL using the original technique were: corneal thickness (OBL: 561.2 µm, no OBL: 549.6 µm, P = .0132), WTW diameter (OBL: 11.6 mm, no OBL: 11.9 mm, P = .0048), corneal resistance factor (OBL: 10.4 mm Hg, no OBL: 9.6 mm Hg, P = 0.0329), and corneal astigmatism (OBL: 0.80 diopter, no OBL: 1.00 diopter, P = .0472) CONCLUSIONS: Less astigmatic, thicker, denser, and smaller corneas increased the risk of OBL using the original technique for flap creation. The cone modification technique was associated with lower risk of OBL formation, even in eyes with significant risk factors for OBL using the original technique. [J Refract Surg. 2017;33(9):584-590.].

Surgical correction of presbyopia.

UNLABELLED: Presbyopia is the most common refractive disorder for people older than 40 years. It is characterized by a gradual and progressive decrease in accommodative amplitude. Many surgical procedures for the correction of presbyopia exist, with additional procedures on the horizon. This review describes the prevalent theories of presbyopia and discusses the available surgical options for correction. FINANCIAL DISCLOSURE: Proprietary or commercial disclosures are listed after the references.

Second-generation corneal deformation signal waveform analysis in normal, forme fruste keratoconic, and manifest keratoconic corneas after statistical correction for potentially confounding factors.

PURPOSE: To evaluate the difference in corneal biomechanical waveform parameters between manifest keratoconus, forme fruste keratoconus, and healthy eyes with a second-generation biomechanical waveform analyzer (Ocular Response Analyzer 2). SETTING: Jules Stein Eye Institute, University of California, Los Angeles, California, USA. DESIGN: Retrospective chart review. METHODS: The biomechanical waveform analyzer was used to obtain corneal hysteresis (CH), corneal resistance factor (CRF), and 37 biomechanical waveform parameters in manifest keratoconus eyes, forme fruste keratoconus eyes, and healthy eyes. Useful distinguishing parameters were found using t tests and a multivariable logistic regression model with stepwise variable selection. Potential confounders were controlled for. RESULTS: The study included 68 manifest keratoconus eyes, 64 forme fruste keratoconus eyes, and 249 healthy eyes. There was a statistical difference in the mean CRF between the normal group (10.2 mm Hg ± 1.7 [SD]) and keratoconus group (6.3 ± 1.9 mm Hg) (P = .003), and between the normal group and the forme fruste keratoconus group (7.8 ± 1.4 mm Hg) (P < .0001). There was no statistical difference in the mean CH between the normal group and the keratoconus group or the forme fruste keratoconus group. The CRF, height of peak 1 (P1) (P = .001), downslope of P1 (dslope1) (P = .027), upslope of peak 2 (P2) (P = .004), and downslope of P2 (P = .006) distinguished the normal group from the keratoconus groups. The CRF, downslope of P2 derived from upper 50% of applanation peak (P = .035), dslope1 (P = .014), and upslope of P1 (P = .008) distinguished the normal group from the forme fruste keratoconus group. CONCLUSION: Differences in multiple biomechanical waveform parameters can differentiate between healthy and diseased conditions and might improve early diagnosis of keratoconus and forme fruste keratoconus. FINANCIAL DISCLOSURE: No author has a financial or proprietary interest in any material or method mentioned.

Combined astigmatic keratotomy and conductive keratoplasty to correct high corneal astigmatism.

PURPOSE: To determine the safety, efficacy, and predictability of combined astigmatic keratotomy (AK) and conductive keratoplasty (CK) for treating high corneal astigmatism. SETTING: University of California-Los Angeles, Los Angeles, California, USA. DESIGN: Retrospective case series. METHODS: From January 1, 2004, to December 31, 2009, AK and CK were performed in eyes with corneal astigmatism of 5.0 diopters (D) or more after keratoplasty or trauma. The uncorrected (UDVA) and corrected (CDVA) distance visual acuities, spherical equivalent (SE), defocus equivalent, mean astigmatism, efficacy index, and complications were evaluated. RESULTS: In 11 eyes of 11 patients, the mean UDVA improved from 1.54 logMAR ± 0.50 (SD) preoperatively to 0.69 ± 0.62 logMAR 3 months postoperatively (P < .001) and the mean CDVA from 0.55 ± 0.62 logMAR to 0.12 ± 0.11 logMAR (P = .028). The mean SE and mean defocus equivalent decreased from -1.25 ± 5.06 D to 3.13 ± 3.06 D (P = .15) and from 7.98 ± 4.41 D to 6.97 ± 3.73 D (P = .45), respectively; these changes were not statistically significant. The mean absolute astigmatism decreased from 10.25 ± 4.71 D to 4.31 ± 2.34 D (P < .001). The mean absolute orthogonal and mean oblique astigmatism showed a statistically significant decrease. The efficacy index was 0.82. One case of wound gape after AK required suturing. No infectious keratitis, corneal perforation, or graft rejection occurred. CONCLUSIONS: Results indicate that combined AK and CK is safe and effective for correcting high corneal astigmatism after surgery or trauma.

Effect of posterior corneal astigmatism on refractive outcomes after toric intraocular lens implantation.

PURPOSE: To compare the prediction error after toric intraocular lens (IOL) (Acrysof IQ) implantation using corneal astigmatism measurements obtained with an IOLMaster automated keratometer and a Galilei dual rotating camera Scheimpflug-Placido tomographer. SETTING: Jules Stein Eye Institute, University of California Los Angeles, Los Angeles, California, USA. DESIGN: Retrospective case series. METHODS: The predicted residual astigmatism after toric IOL implantation was calculated using preoperative astigmatism values from an automated keratometer and the total corneal power (TCP) determined by ray tracing through the measured anterior and posterior corneal surfaces using dual Scheimpflug-Placido tomography. The prediction error was calculated as the difference between the predicted astigmatism and the manifest astigmatism at least 1 month postoperatively. The calculations included vector analysis. RESULTS: The study evaluated 35 eyes (35 patients). The preoperative corneal posterior astigmatism mean magnitude was 0.33 diopter (D) ± 0.16 (SD) (vector mean 0.23 × 176). Twenty-six eyes (74.3%) had with-the-rule (WTR) posterior astigmatism. The postoperative manifest refractive astigmatism mean magnitude was 0.38 ± 0.18 D (vector mean 0.26 × 171). There was no statistically significant difference in the mean magnitude prediction error between the automated keratometer and TCP techniques. However, the automated keratometer method tended to overcorrect WTR astigmatism and undercorrect against-the-rule (ATR) astigmatism. The TCP technique lacked these biases. CONCLUSIONS: The automated keratometer and TCP methods for estimating the magnitude of corneal astigmatism gave similar results. However, the automated keratometer method tended to overcorrect WTR astigmatism and undercorrect ATR astigmatism. FINANCIAL DISCLOSURE: Dr. Hamilton has received honoraria for educational lectures from Ziemer Ophthalmic Systems. No other author has a financial or proprietary interest in any material or method mentioned.

Effect of mitomycin-C on the variance in refractive outcomes after photorefractive keratectomy.

PURPOSE: To compare the variance in manifest refraction spherical equivalent (MRSE) after photorefractive keratectomy (PRK) with mitomycin-C (MMC), PRK without MMC, and laser in situ keratomileusis (LASIK) for the treatment of myopic astigmatism. SETTING: Jules Stein Eye Institute, University of California, Los Angeles, Los Angeles, California, USA. DESIGN: Retrospective case series. METHODS: Patients were classified into 3 groups of preoperative refraction-matched eyes as follows: PRK with MMC 0.02%, PRK without MMC, and LASIK. The preoperative and postoperative MRSE, preoperative corrected distance visual acuity, and postoperative uncorrected distance visual acuity (UDVA) were analyzed. RESULTS: Each group comprised 30 eyes. Follow-up was at least 6 months in the LASIK group and 12 months in the 2 PRK groups. There were no statistically significant differences in the mean preoperative MRSE (P=.95) or postoperative MRSE (P=.06) between the 3 groups. The mean postoperative MRSE was -0.07 diopter (D) ± 0.47 (SD), -0.14 ± 0.26 D, and 0.02 ± 0.25 D in the PRK with MMC 0.02% group, PRK without MMC group, and LASIK group, respectively. The variance in the postoperative MRSE in the PRK with MMC 0.02% group was significantly higher than that in the PRK without MMC group (P=.002) and in the LASIK group (P=.001). There was no statistically significant difference in the mean postoperative UDVA between the 3 groups (P=.47). CONCLUSIONS: Refractive outcomes after PRK for myopia were more variable when MMC 0.02% was used. This should be weighed against the advantage of intraoperative MMC use in reducing haze after PRK.

Annular amniotic membrane transplantation as a host incorporated graft in the management of Brown-McLean syndrome.

PURPOSE: To report the use of annular amniotic membrane transplantation as a host incorporated graft in the management of Brown-McLean syndrome. METHODS: Case report. RESULTS: An 87-year-old man underwent annular amniotic membrane transplantation with ethylenediaminetetraacetic acid chelation resulting in resolution of pain, irritation, and foreign body sensation, and resolution of recurrent peripheral epithelial defects. CONCLUSIONS: Annular amniotic membrane transplantation is a safe and effective treatment strategy for the management of Brown-McLean syndrome.

Comparison of posterior corneal imaging before and after LASIK using dual rotating scheimpflug and scanning slit-beam corneal tomography systems.

PURPOSE: To compare the maximum posterior elevation (MPE) measurements before and after LASIK using a dual rotating Scheimpflug (DRS) imaging system (Galilei, Ziemer Ophthalmic Systems, Port, Switzerland) and a scanning slit-beam (SSB) imaging system (Orbscan IIz, Bausch & Lomb, Rochester, NY). METHODS: This retrospective study included 78 eyes from 78 patients who underwent myopic LASIK. Preoperative and postoperative data collected included anterior and posterior best-fit sphere radius and axial curvature readings, posterior central elevation (PCE), and MPE relative to a best-fit sphere using a 7.8-mm region of interest. Data were compared using paired t test analysis. RESULTS: Mean preoperative PCE (5.06 ± 2.29 µm with the DRS system and 12.78 ± 6.90 µm with the SSB system) and MPE (4.87 ± 4 µm with the DRS system and 15.44 ± 9.78 µm with the SSB system) were statistically different (P < .001). Mean postoperative PCE (4.55 ± 2.34 µm with the DRS system and 20.59 ± 8.11 µm with the SSB system) and MPE (4.90 ± 3.35 µm with the DRS system and 24.95 ± 10.15 µm with the SSB system) were statistically different (P < .001). The difference between preoperative and postoperative MPE measurements by DRS was not statistically significant (P = .953), whereas the difference measured by SSB was statistically significant (P < .001). CONCLUSIONS: The consistency of DRS measurements suggests that the posterior surface of the cornea does not change appreciably after keratorefractive surgery and is imaged more accurately using DRS compared with SSB. The DRS system affords confidence in interpreting data that are useful for discerning morphologic abnormalities of the cornea, both before and after keratorefractive surgery.

Corneal deformation signal waveform analysis in keratoconic versus post-femtosecond laser in situ keratomileusis eyes after statistical correction for potentially confounding factors.

PURPOSE: To evaluate and compare corneal biomechanical waveform parameters between keratoconic and post-femtosecond laser in situ keratomileusis (LASIK). SETTING: Jules Stein Eye Institute, University of California, Los Angeles, California, USA. DESIGN: Comparative case series. METHODS: The Ocular Response Analyzer was used to obtain the corneal hysteresis (CH), corneal resistance factor (CRF), and 39 biomechanical waveform parameters in manifest keratoconic eyes and post-femtosecond LASIK eyes. Univariate tests were used to assess the difference in each parameter between the 2 groups of eyes. After controlling for central corneal thickness (CCT) and age, a logistic regression model was used to select the parameters most useful in distinguishing between the 2 groups. RESULTS: After statistically controlling for the differences in CCT and age, 7 parameters were found to be the most useful in distinguishing between groups: aplhf (high frequency noise in the region between peaks [P1 and P2]; P<.0001), w2 (width of P2 at base; P=.001), dslop1 (down-slope of P1 of wave; P<.0001), aindex (degree of "non-monotonicity" of rising and falling edges of first peak of wave, P=.0007), uslope1 (upslope of the P1 of wave; P=.001), CH (P=.035), and P1area (area under P1 of wave; P=.006). The area under the receiver operating characteristic curve for the model using these parameters was 0.932. CONCLUSIONS: Differences in multiple biomechanical waveform parameters between the keratoconus and post-LASIK groups suggests that waveform analysis may be useful to differentiate between healthy and diseased biomechanical conditions.

Development of an advanced nomogram for myopic astigmatic wavefront-guided laser in situ keratomileusis (LASIK).

BACKGROUND AND OBJECTIVE: To identify the relationship between preoperative parameters and postoperative overcorrection or undercorrection in eyes with myopic astigmatism treated with wavefront-guided laser in situ keratomileusis (LASIK), and to develop an advanced surgical nomogram. PATIENTS AND METHODS: A retrospective chart review of 468 eyes that underwent wavefront-guided LASIK for myopia with astigmatism with the Alcon LADARVision 4000 (Alcon Laboratories, Fort Worth, TX), of which 235 had flaps created by microkeratome (OneUse; Moria Surgical, Doylestown, PA) and 233 by femtosecond laser (Intralase; AMO, Santa Ana, CA). Manifest sphere, cylinder, and spherical equivalent were recorded preoperatively and 3 months postoperatively. Various parameters from patient records were analyzed to identify which had greatest influence on outcomes. RESULTS: Manifest spherical equivalent was the most important predictor of surgical overcorrection, with the second being spherical aberration. In both groups, there was a statistically significant (P < .0001) correlation of spherical aberration with the amount of overcorrection. Using these two parameters, compensatory nomograms were derived. CONCLUSION: Surgical overcorrection in wavefront-guided LASIK for myopic astigmatism correlates positively with the amount of spherical equivalent treated and preoperative spherical aberration. Nomograms incorporating spherical aberration may improve accuracy of outcomes.

Corneal biomechanical properties in normal, forme fruste keratoconus, and manifest keratoconus after statistical correction for potentially confounding factors.

PURPOSE: To evaluate the difference in corneal biomechanical properties, after controlling for potentially confounding factors, along the spectrum of keratoconic disease as measured by the keratoconus severity score. METHODS: The corneal biomechanical properties of 73 keratoconic (KCN) eyes of 54 patients, 42 forme fruste keratoconic (FFKCN) eyes of 32 patients, and 115 healthy eyes of 115 age- and sex-matched patients were reviewed retrospectively. The main outcome measures were corneal hysteresis (CH) and corneal resistance factor (CRF). RESULTS: In the normal group, the mean CH was 11.0 ± 1.4 mm Hg and mean CRF was 11.1 ± 1.6 mm Hg. The FFKCN mean CH was 8.8 ± 1.4 mm Hg and mean CRF was 8.6 ± 1.3 mm Hg. The KCN mean CH was 7.9 ± 1.3 mm Hg and mean CRF was 7.3 ± 1.4 mm Hg. There were statistically significant differences in the mean CH and CRF in the normal group compared with the FFKCN and the KCN groups (P < 0.001) after statistically controlling for differences in central corneal thickness, age, and sex. CONCLUSIONS: There is a significant difference in the mean CH and CRF between normal and FFKCN corneas after controlling for differences in age, sex, and central corneal thickness. However, there is a significant overlap in the distribution of CH and CRF values among all groups. The biomechanical parameters CH and CRF cannot be used alone but may be a useful clinical adjunct to other diagnostic tools, such as corneal tomography, in distinguishing normal from subclinical keratoconic corneas.

Differences in the corneal biomechanical effects of surface ablation compared with laser in situ keratomileusis using a microkeratome or femtosecond laser.

PURPOSE: To compare the effects of different flap creation techniques on the biomechanical properties of the cornea in patients having myopic laser refractive surgery. SETTING: UCLA Laser Refractive Center of the Jules Stein Eye Institute, Los Angeles, California, USA. METHODS: In this retrospective case series, eyes that had myopic laser refractive surgery were categorized according to the type of flap creation: mechanical microkeratome (MK) LASIK (n=32), femtosecond laser (FSL) LASIK (n=32), or no flap creation (PRK) (n=33). The preoperative central corneal thickness, intraoperative flap thickness, and planned ablation depth (AD),and the preoperative and postoperative manifest refraction spherical equivalent, corneal hysteresis (CH), and corneal resistance factor (CRF) were recorded. RESULTS: The mean change in CH (DeltaCH) was 2.2 mm Hg, 1.9 mm Hg, and 2.3 mm Hg in the MK, FSL, and PRK groups, respectively. There were no significant differences in AD, DeltaCH, or DeltaCRF between the 3 groups. The correlation between AD and DeltaCH was significant in all 3 groups. The correlation was strongest in the FSL group (r=0.82, P<.0001) and weaker in the PRK group (r=0.47, P= .006) and MK group (r=0.46, P= .008). CONCLUSIONS: The biomechanical measures of CH and CRF decreased similarly after PRK and LASIK using laser or mechanical flap creation. However, LASIK using femtosecond laser flap creation caused a significantly more predictable change in corneal biomechanics, which correlated strongly with AD, than the change with PRK and LASIK with microkeratome flap creation.

Corneal biomechanical measurements before and after laser in situ keratomileusis.

PURPOSE: To study the correlation between corneal biomechanical properties and surgical parameters in myopic patients before and after laser in situ keratomileusis (LASIK). SETTING: UCLA Laser Refractive Center of the Jules Stein Eye Institute, Los Angeles, California, USA. METHODS: In 43 eyes of 43 patients, the Ocular Response Analyzer was used to measure corneal hysteresis (CH), corneal resistance factor (CRF), Goldmann-correlated intraocular pressure (IOPg), and corneal-compensated IOP (IOPcc) before and 1 month after LASIK. Manifest refraction spherical equivalent (MRSE), preoperative central corneal thickness (CCT), flap thickness (FT), and ablation depth (AD) were also recorded. Changes in these parameters after LASIK were calculated and the correlations between the change in CH (DeltaCH), change in CRF (DeltaCRF) and the AD, change in MRSE (DeltaMRSE), and CCT were examined. The relationship between DeltaCRF and DeltaMRSE was examined by linear regression analysis. RESULTS: The preoperative mean CH and mean CRF (11.52 mm Hg +/- 1.28 [SD] and 11.68 +/- 1.40 mm Hg, respectively) were significantly higher than postoperative values (9.48 +/- 1.24 mm Hg and 8.47 +/- 1.53 mm Hg, respectively) (P < .0001). A higher attempted correction was correlated with a larger DeltaCH and DeltaCRF (AD, r = 0.47 and r = 0.65, respectively; DeltaMRSE, r = 0.51 and r = 0.66, respectively). No correlation was found between DeltaCH, DeltaCRF, and preoperative CCT. CONCLUSIONS: Changes in CH and CRF after LASIK suggest alteration in corneal biomechanics correlating with attempted correction. The CRF parameter may be more useful than the CH parameter in assessing biomechanical changes resulting from LASIK.

Recalcitrant epithelial ingrowth in patients with compromised eyelid function.

PURPOSE: To report recalcitrant unilateral epithelial ingrowth in two patients with ipsilateral weak eyelid closure. METHODS: Two patients with weak eyelid closure who underwent simultaneous, uncomplicated LASIK developed unilateral epithelial ingrowth. RESULTS: Eight months postoperatively, one patient presented with right-sided epithelial ingrowth. One month after removal, more extensive epithelial ingrowth was noted and removed, and the flap gutters were sealed with fibrin adhesive. Epithelial ingrowth recurred 1 week later. The epithelial ingrowth was removed and the flap was secured with concurrent placement of radial 10-0 nylon sutures. No further epithelial ingrowth recurred. In the second patient, epithelial ingrowth was noted in the left eye 4 months postoperatively. Eight months later, the ingrowth was removed with subsequent recurrence in 2 weeks. CONCLUSIONS: Weak eyelid closure may be a predisposing factor to poor flap adhesion and epithelial ingrowth. Close attention to lid function may be of importance in deciding between LASIK and photorefractive keratectomy, particularly in patients with other risk factors for epithelial ingrowth.

Identification of scanning slit-beam topographic parameters important in distinguishing normal from keratoconic corneal morphologic features.

PURPOSE: To identify morphologic parameters obtained using scanning slit-beam topography that help distinguish normal from keratoconic corneal morphologic features. DESIGN: Observational, retrospective, cross-sectional study. METHODS: This retrospective review examined 207 normal eyes of patients undergoing an initial consultation for primary refractive surgery and 42 eyes with clinical keratoconus (KCN). The following parameters were examined and compared between the two groups: astigmatism, central corneal power, irregularity indices at 3 mm (II3) and 5 mm (II5), maximal posterior elevation (MPE) magnitude and location, thinnest optical pachymetry (TOP) magnitude and location, anterior elevation best-fit sphere (ABFS), posterior elevation best-fit sphere (PBFS), the ratio of ABFS to PBFS, the difference between average inferior and average superior K values at 3 mm and 5 mm in both keratometric (I-S K3 and I-S K5) and tangential (I-S T3 and I-S T5) topographic maps, and skewed radial axis at 3 mm (SRAX3) and 5 mm (SRAX5) of the keratometric topography map. RESULTS: The II3, II5, MPE magnitude, TOP magnitude, ABFS, PBFS, ABFS-to-PBFS ratio, I-S K at both 3 mm and 5 mm, I-S T at both 3 and 5 mm, and SRAX at 3 mm and 5 mm values were significantly different among the two groups (P < .001). The least-correlated parameters were SRAX3, TOP magnitude, and II3 in the KCN group and I-S K3, amount of astigmatism and MPE magnitude in the normal group. CONCLUSIONS: Parameters obtained using scanning slit-beam topography may allow improved differentiation of keratoconic from normal corneal shapes, especially when the poorly correlated intragroup parameters are used.

Cataract surgery in patients with prior refractive surgery.

As the number and types of keratorefractive procedures increase and as the baby boomer population moves into the "cataractous decades," the number of patients requiring cataract surgery following refractive surgery grows larger each year. While technological advances in surgical instrumentation and intraocular lens (IOL) design allow us to perform cleaner, faster, and more reliable cataract extractions, the ultimate postoperative refraction depends primarily on calculations performed before surgery. Third-generation IOL formulas ( Haigis, Hoffer Q, Holladay 2, or SRK/T) provide outstanding accuracy when used for eyes with physiologic, prolate corneas. In addition, most instruments used today for measuring corneal curvature and power were designed before the era of refractive surgery. These formulas and instruments make assumptions about the anatomy and refractive properties of the cornea that are no longer valid following most keratorefractive procedures. These breakdowns in IOL calculation often result in a "refractive surprise" after cataract surgery, which may require subsequent surgical correction. This article examines recent publications of modeling studies of various methods for estimating effective K values for IOL calculation, cataract surgery case series following refractive surgery, new corneal topography technologies and methods for correcting "refractive surprises" postoperatively.