Impact of Donor Age on Corneal Endothelium-Descemet Membrane Layer Scroll Formation.

OBJECTIVE: To correlate corneal endothelium-Descemet membrane (EDM) layer parameters of scroll tightness with donor age, endothelial cell density (ECD), and history of diabetes. METHODS: Endothelium-Descemet membrane layer scrolls were harvested from 26 corneoscleral buttons using the SCUBA technique by a cornea-fellowship trained ophthalmologist masked to donor age. Two independent outcome parameters were used to characterize the scrolling severity of successfully harvested tissue: scroll width and tendency for EDM scroll formation (referred to as scroll rating on a 1-4 scale: incomplete scroll formation to tightly scrolled). RESULTS: Mean donor age was 59 ± 17 (15-69) years. Mean ECD of EDM scroll was 2,451 ± 626 (range: 1,307-3,195) cells per square millimeter. Using stepwise linear regression, a significant correlation was found between scroll width and donor age (R=0.497, P<0.05). Additionally, a significant inverse correlation was found between scroll width and ECD (R=-0.605, P<0.05). There was no statistically significant correlation between a donor history of diabetes and the parameters of scrolling tendency. CONCLUSIONS: Our data suggest that using older donors reduces EDM scroll tightness.

The accuracy of the double-K adjustment for third-generation intraocular lens calculation formulas in previous keratorefractive surgery eyes.

PURPOSE: To evaluate the effect of the double-K (DK) modification on third-generation formulas. METHODS: Thirty-eight previously myopic and 24 previously hyperopic eyes that underwent phacoemulsification with intraocular lens (IOL) insertion after Laser in situ keratomileusis (LASIK) were evaluated. Pre-LASIK refraction and keratometry, post-LASIK topography, axial length (AL), IOL type and power, and 1-month postphacoemulsification refraction were recorded spherical equivalent after phacoemulsification (SE(postphaco)). Measured corneal power was adjusted using published and validated methods for postmyopic and posthyperopic LASIK. For each eye, and using SE(postphaco), different DK-IOL formulas were used to calculate the corresponding IOL power, the outcome measure, which was compared with the implanted IOL. RESULTS: DK-Holladay 1 yielded the highest Pearson correlation coefficient (PCC), 0.955 for myopes and 0.943 for high myopes (AL>26 mm). Mean error (ME) and mean absolute error (MAE) for myopes for DK Sanders-Retzlaff-Kraff theoretical formula [DK-SRK/T] were 0.44±0.84 D and 0.75±0.61 D for DK-SRK/T compared with -0.04±0.67 D and 0.52±0.40 D for DK-Holladay 1 (P<0.001 and P=0.016, respectively), and 0.03±0.88 and 0.64±0.58 for DK-Hoffer Q. For high myopes, ME and MAE were 0.75±0.81 D and 0.84±0.69 D for DK-SRK/T, and -0.05±0.74 D (P<0.0001) and 0.57±0.45 D (P=0.019) for DK-Holladay 1. About 29% of DK-SRK/T eyes with large AL had MAE>1.5 D, compared with 0% for DK-Holladay 1 and 14% for DK-Hoffer-Q. Eyes with previous hyperopic LASIK faired similarly for all formulas, with similar PCCs, and only 8% in each category with MAE>1.5 D. CONCLUSIONS: DK-SRK/T overestimates IOL power in eyes with large AL, especially with concomitant steep pre-lasik keratometry. Among third-generation formulas, DK-Holladay 1 seems more accurate to use in postmyopic LASIK eyes.

Corneal higher-order aberrations after Descemet's stripping automated endothelial keratoplasty.

PURPOSE: To compare the corneal higher-order aberration (HOA) after Descemet's stripping automated endothelial keratoplasty (DSAEK) and penetrating keratoplasty (PKP), and in age-matched controls. DESIGN: Cross-sectional, non-comparative interventional case series. PARTICIPANTS: Thirty-one eyes of 28 patients who underwent DSAEK, 20 eyes of 16 patients who underwent PKP, and 31 eyes of 31 control patients. INTERVENTION: The corneal topography and HOAs of the central 4- and 6-mm zones from anterior and posterior corneal surfaces were evaluated postoperatively with the Scheimpflug rotating imaging system (Oculus Gmbh, Wetzlar, Germany). MAIN OUTCOME MEASURES: Anterior and posterior corneal HOAs. RESULTS: The mean anterior corneal total HOAs of the central 4 and 6 mm were 0.599+/-0.288 microm and 1.215+/-0.496 microm, respectively, in eyes that underwent DSAEK; 1.730+/-0.826 microm and 3.349+/-1.490 microm, respectively, in eyes that underwent PKP; and 0.439+/-0.163 microm and 0.921+/-0.300 microm, respectively, in controls. Although the mean anterior corneal total HOAs of the central 4 and 6 mm were significantly higher in eyes that underwent PKP than in eyes that underwent DSAEK and in controls (P<0.01), there was no significant difference in anterior corneal total HOAs of the central 4 and 6 mm between eyes that underwent DSAEK and controls. The mean posterior corneal total HOAs of the central 4 and 6 mm were 3.680+/-1.586 microm and 7.142+/-3.011 microm, respectively, in eyes that underwent DSAEK; 2.957+/-1.238 microm and 5.314+/-2.095 microm, respectively, in eyes that underwent PKP; and 0.818+/-0.193 microm and 1.609+/-0.344 microm, respectively, in controls. Although there was no significant difference in posterior corneal total HOAs of the central 4 mm between the DSAEK group and the PKP group, the posterior corneal HOAs of the central 6 mm were significantly higher in the DSAEK group than in the PKP group (P<0.01). CONCLUSIONS: Although posterior corneal HOAs are significantly higher in eyes that underwent DSAEK, anterior corneal HOAs are not significantly different in eyes that underwent DSAEK than those of age-matched controls.

Effect of systane and optive on aqueous tear evaporation in patients with dry eye disease.

OBJECTIVE: To compare the effect on aqueous tear (AT) evaporation rate of Systane and Optive at 30 min postinstillation in patients with dry eye. METHODS: In a crossover study of 20 patients with keratoconjunctivitis sicca, the evaporation rate of AT was measured. Evaporometry was used at two relative humidity (RH) ranges of 25% to 35% and 35% to 45%. The measurements were made at baseline (before the instillation of the study agent) and at 30 min after the instillation of 40 µL of either Systane or Optive per randomization assignment per visit with a 1-week interval between visits. RESULTS: No significant effects on AT evaporation rates at both RHs were found between study agents. CONCLUSIONS: In our study, neither Systane nor Optive has a significant impact on AT evaporation at 30 min postinstillation in patients with dry eye.

Wavefront-guided ablation retreatment using Iris registration.

PURPOSE: To evaluate the efficacy, predictability, safety, and intraoperative and postoperative complications of laser in situ keratomileusis (LASIK) retreatment in myopic eyes using wavefront-guided ablation with iris registration (IR). METHODS: Retrospective analysis was used to evaluate wavefront-guided retreatment with IR in a consecutive cohort of 77 eyes (57 patients) after LASIK. The eyes were divided into two groups: no previous retreatment group (group 1) (n = 63) and previous LASIK retreatment group (group 2) (n = 14). The primary outcome variables assessed postoperatively at 1, 3, and 6 months were uncorrected visual acuity (UCVA), best-corrected visual acuity (BCVA), and pre- and postretreatment changes in manifest refraction. RESULTS: The mean preretreatment spherical equivalent in group 1 was reduced from -0.5 +/- 1.0 diopter (D) (range -3 to 2.4) to 0.06 +/- 0.3 (range -0.9 to 0.6) (P < 0.002) at 6 months. In group 2, the mean preretreatment spherical equivalent was reduced from -0.9 +/- 1.24D (range -3.1 to -0.5) to 0.04 +/- 0.5 (range -1.0 to 1.1) (P < 0.049) at 6 months. At 6 months, UCVA was 20/20 or better in 92% in group 1 and 64% in group 2, of patients, respectively. No eyes lost more than one line of BCVA in group 1 and one eye (7%) lost two lines of BCVA in group 2. CONCLUSION: Wavefront-guided LASIK retreatment with IR after LASIK is an effective, predictable, and safe procedure in cases requiring a single retreatment. In contrast, eyes with previous retreatments showed less predictability and lower percentage of eyes with postoperative 20/20 UCVA.

Outcomes of resident-performed laser-assisted vs traditional phacoemulsification.

PURPOSE: To compare the effectiveness of femtosecond laser-assisted cataract surgery (FLACS) and conventional phacoemulsification cataract surgery (CPS) by resident surgeons. SETTING: Parkland Memorial Health and Hospital System, Dallas, Texas, USA. DESIGN: Prospective randomized study. METHODS: All surgeries to be performed by postgraduate year 3 and year 4 residents from October 2015 through June 2017 were eligible for inclusion. Patients were required to complete postoperative day 1, week 1, month 1, and month 3 visits. Specular microscopy was performed preoperatively and postoperatively. Surgeries were filmed, and each step was timed and compared. Surgeon and patient surveys were filled out postoperatively. RESULTS: Of the 135 eyes of 96 subjects enrolled in the study, 64 eyes received FLACS and 71 eyes received CPS. There was no significant difference in corrected distance visual acuity (CDVA), either preoperatively or at the postoperative day 1, week 1, month 1, or month 3 visits (P = .469, .539, .701, .777, and .777, respectively). Cumulated dissipated energy and irrigation fluid usage were not different between FLACS and CPS (P = .521 and .368, respectively), nor was there a difference in the reduction of endothelial cell counts postoperatively (P = .881). Wound creation (P = .014), cortical cleanup (P = .009), and IOL implantation (P = .031) were faster in the CPS group. Survey results indicated that the overall patient experience was similar for FLACS and CPS. CONCLUSIONS: This first prospective randomized trial evaluating resident-performed FLACS shows that, in resident hands, FLACS provides similar results to CPS regarding visual acuity, endothelial cell loss, operative time, patient satisfaction, and surgical complication rate.

Corneal refractive power estimation and intraocular lens calculation after hyperopic LASIK.

PURPOSE: To identify key independent variables in estimating corneal refractive power (KBC) after hyperopic LASIK. DESIGN: Retrospective study. PARTICIPANTS: We included 24 eyes of 16 hyperopic patients who underwent LASIK with subsequent phacoemulsification and posterior chamber intraocular lens (IOL) implantation in the same eye. METHODS: Pre-LASIK and post-LASIK spherical equivalent (SE) refractions and topographies, axial length, implant type and power, and 3-month postphacoemulsification SE were recorded. Using the double-K Hoffer Q formula, corneal power was backcalculated for every eye (KBC), regression-based formulas derived, and corresponding IOL powers calculated and compared with published methods. MAIN OUTCOME MEASURES: The Pearson correlation coefficient (PCC) and arithmetic and absolute corneal and IOL power errors. RESULTS: Adjusting either the average central corneal power (ACCP(3mm)) or SimK based on the laser-induced spherical equivalent change (DeltaSE) resulted in an estimated corneal power (ACCP(adj) and SimK(adj)) with highest correlation with KBC (PCC=0.940 and 0.956, respectively) and lowest absolute corneal estimation error (0.37+/-0.45 and 0.38+/-0.39 diopter [D], respectively). The ACCP(adj) closely mirrored published DeltaSE-based adjustments of central corneal power on different topographers, whereas DeltaSE-based SimK adjustments varied across platforms. Using ACCP(adj) or SimK(adj) in the double-K Hoffer Q, using ACCP(3mm) or SimK in single-K Hoffer Q and adjusting the resultant IOL power based on DeltaSE, or applying Masket's formula all yielded accurate and similar IOL powers. The Latkany method consistently underestimated IOL power. The Feiz-Mannis and clinical history methods yielded poor IOL correlations and large IOL errors. CONCLUSION: After hyperopic LASIK, adjusting either corneal power or IOL power based on DeltaSE accurately estimates the appropriate IOL power.

Ocular aberrations measured by the Fourier-based WaveScan and Zernike-based LADARWave Hartmann-Shack aberrometers.

PURPOSE: To evaluate agreements in lower and higher order aberration measurements by two Hartmann-Shack wavefront-sensing devices. METHODS: Using the VISX WaveScan and Alcon LADARWave aberrometers, ocular aberrations at a fixed optical zone of 6 mm were measured on 36 eyes of 18 patients. A tunable light intensity source was used to control pupil size, which was checked using infrared pupillometry. Repeatability of measurements was evaluated using the intra-class correlation coefficient with 3 consecutive measurements on each aberrometer. RESULTS: Mean absolute defocus for WaveScan and LADARWave was 2.82 +/- 2.69 and 2.93 +/- 3.24 root-mean-square (RMS) microm, whereas astigmatism was 0.81 +/- 0.49 and 0.87 +/- 0.57 microm, respectively. Pearson correlation coefficients between the two aberrometers were 0.908 and 0.870 for defocus and astigmatism, respectively, whereas higher order aberration correlation was less tight (Pearson correlation coefficient=0.596 for coma, 0.746 for trefoil, 0.836 for spherical aberration, 0.637 for secondary astigmatism, and 0.963 for quadra-foil [P<.001 for all]). The LADARWave had a tendency to display more spherical aberration than the WaveScan, especially at high aberration values, with mean absolute difference in measurement of 0.12 +/- 0.08 microm, and only 44% of eyes having less than +/-0.10 RMS microm of difference. The mean total higher order aberration absolute difference was 0.14 +/- 0.14 microm, with only 50% of eyes within +/-0.1 RMS of agreement. Vector analysis revealed appreciable discrepancies in third- and fourth-order directional Zemike components, while showing similar values for fifth-order components. Intra-class correlation coefficient values for both aberrometers over different aberration orders showed excellent repeatability. CONCLUSIONS: The WaveScan and LADARWave share similar lower order aberration measurements, but display significantly different higher order aberration values.

Historical brief on composition of human meibum lipids.

Meibomian glands (MG) secrete an oily substance, meibum, that spreads across the ocular surface and mixes with secretions produced by other ocular structures to create a thin film. The protective efficacy of the tear film is believed to be related to the chemical composition of the lipid layer. We reviewed the literature describing the composition of human MG secretions and have provided an overview on methods of collecting meibum samples, methods of lipid analyses, and the results obtained in previous studies. The usefulness and quality of the data obtained about meibum depend on proper sampling and the analytical techniques used. Historically, several methods have been developed, which have yielded contradictory data regarding meibum sample collection and analytical techniques. Based on review of the literature, the major lipids present in meibum are of nonpolar origin: waxes, sterols, and sterol esters, followed by triacylglycerides and fatty acids. The amphiphilic lipids, diacylglycerides, were reported in fewer studies, and monoacylglycerides were reported in only two. Information on the composition of the polar lipids is more controversial. Meibum phospholipids were found in small amounts (16% or less) in some studies, but not in others. Thus, meibum is a complex mixture of lipid molecules. Historical analytical inconsistencies may be partly explained by limitations of past analytical procedures and by the consideration that the tear film lipid layer may have contributing sources other than meibum.

Assessment and impact of the time of day on aqueous tear evaporation in normal subjects.

OBJECTIVES: To determine the impact of the time of day on aqueous tear (AT) evaporation in normal subjects on two consecutive days. METHODS: In a controlled laboratory setting, morning and afternoon AT evaporation was tested in 19 normal subjects, at the same time of day on two consecutive days. Evaporometry was used at two ranges of relative humidity (RH) 25% to 35% and 35% to 45%. RESULTS: Mean AT evaporation rates were 0.069 +/- 0.024 for 25% to 35% RH and 0.049 +/- 0.018 for 35% to 45% (P = 0.001). There were significant differences for both RH between time of day (P < 0.05) on day 1, but not observed on day 2. Variation between days showed no difference for RH during the afternoon, but there was a difference during the morning (P = 0.042). CONCLUSIONS: The data are remarkably consistent between study days, but there is more fluctuation during the morning than in the afternoon. Therefore, to further standardize AT evaporation study protocol, we recommend perform evaporometry measurements during the afternoon rather than the morning, because our results showed less variability during the afternoon test between days.

Quality of life changes after myopic wavefront-guided laser in situ keratomileusis.

OBJECTIVE: To evaluate the changes in quality of life in patients undergoing wavefront-guided laser in situ keratomeilusis (WG-LASIK). METHODS: Thirty candidates undergoing WG-LASIK were enrolled in a prospective study at the University of Texas Southwestern Medical Center at Dallas, TX. The patients were asked to fill out a questionnaire which had questions pertaining to their quality of life, preoperatively and 3 months postoperatively. The average patients' age was 41.4 +/- 12.45 years, and the preoperative manifest refractive spherical equivalent was -3.62 +/- 1.60 D (-1.00 to -7.50 D). RESULTS: The total quality-of-life score improved from 3.70 +/- 0.91 to 3.90 +/- 0.97 (P = 0.01). Most of the psychologic well-being items like energy level, stress level, self-confidence, sense of safety, and the social role subscale items such as ability to communicate with others, job performance, and sex life showed significant improvement in mean scores (P < 0.05). The postoperative visual function and visual symptom scores, however, were overall similar to preoperative levels. CONCLUSIONS: Consistent with previous studies with conventional LASIK, there is a significant improvement in quality of life after WG-LASIK. The main changes pertain to psychologic well-being and social role, more than the changes in visual function per se. However, the latter did not show evidence of deterioration, nor of worsening of visual symptoms, contrary to some studies with conventional LASIK.

Tandem scanning confocal microscopy of cornea after descemet stripping automated endothelial keratoplasty.

PURPOSE: To evaluate the changes in the corneal stroma after Descemet stripping automated endothelial keratoplasty (DSAEK) using tandem scanning confocal microscopy (CM). METHODS: Thirteen eyes of 13 patients who underwent DSAEK without preoperative corneal haze or scar obvious at the slit lamp, any ocular disease, and postoperative complication were included in the study. All patients were examined clinically and by CM 6 months after DSAEK. RESULTS: Six months after DSAEK, none of the eyes had clinically significant interface haze (i.e., haze affecting quantity or quality of vision) at slit lamp. The mean best spectacle corrected visual acuity was 0.18 +/- 0.12 (range 0-0.4) logMAR (Snellen 20/30). The CM revealed highly reflective particles in interface in six eyes, particles with mild surrounding increased reflectivity in four eyes, and no discernible interface in three eyes. The mean particles density at interface was 28.6 +/- 23.4 particles/mm. No significant keratocyte activation was seen in any case at the interface. The mean anterior stromal reflectivity was 431.2 +/- 269.1 confocal back scatter units (CBU) and the mean interface reflectivity was 65.9 +/- 46.9 CBU. The mean anterior stromal reflectivity was significantly greater than the mean interface reflectivity (P<0.01). Significant keratocyte activation with high reflectivity was seen in superficial anterior stroma in 8 of 13 eyes. CONCLUSIONS: Tandem scanning CM shows the presence of highly reflective particles at the level of the DSAEK interface that are morphologically similar to a laser in situ keratomileusis interface. The stromal reflectivity is more prominent in subepithelial layers than that of interface 6 months after DSAEK. However, the areas under the mean reflectivity peaks (CBU) corresponding to the flap interface and superficial anterior stroma do not seem to correlate with best spectacle corrected visual acuity results after the procedure.

Evaluation of the role of ProKera in the management of ocular surface and orbital disorders.

OBJECTIVES: To report the efficacy and safety profile of sutureless and adhesiveless amniotic membrane device (ProKera, Bio-Tissue, Inc., Miami, FL) in the management of various ocular surface and orbital disorders. METHODS: Twenty eyes of 20 patients underwent placement of 21 ProKera implants between March 2006 and July 2007 at the University of Texas Southwestern Medical Center. Patient demographics, indications for placement, and duration of ProKera retention were recorded. Outcomes measured included corneal epithelial healing, visual acuity, patient tolerance, and adverse events. RESULTS: ProKera was most commonly used in patients with corneal neovascularization with or without limbal stem-cell deficiency (10 eyes). Other indications included recurrent pterygium or pseudopterygium (three eyes), anophthalmic orbit contraction (two eyes), persistent epithelial defects (two eyes), severe thinning in a corneal ulcer (one eye), benign hereditary intraepithelial dyskeratosis (one eye), and band keratopathy (one eye). The mean duration of ProKera retention was 25.3 days (range, 0-125) visual acuity improved in 12 eyes (60%). Immediate adverse events included residual epithelial defects after removal (five eyes) and spontaneous extrusion of the implant (four eyes). Six patients (30%) reported eye pain or headache and four eyes (20%) had recurrence of the primary pathology. CONCLUSIONS: Sutureless and adhesiveless amniotic membrane transplantation is a safe and effective method to promote healing and reconstruction of the ocular surface and orbit with minimal side effects. Recurrence of the underlying primary pathology remains a concern. The advent of a newer, softer conformer ring may improve patient tolerability and limit discomfort.

Corneal thickness association with ocular and corneal high-order aberrations.

PURPOSE: To investigate the association among central corneal thickness, peripheral corneal thickness (PCT), and wavefront aberrations in the anterior cornea, posterior cornea and the whole eye in myopia. METHODS: Sixty-four eyes of 64 myopic subjects were evaluated with a Pentacam rotating Scheimpflug camera (Oculus, Inc., WA) corneal topographer for: (1) wavefront aberrations from the anterior and posterior corneal surface, (2) corneal thickness (central and peripheral), and (3) with a wavefront aberration-supported cornea ablation wavefront analyzer (Wavescan, Visx, Inc., Santa Clara, CA) for wavefront aberrations generated in the whole eye. Relationships between the wavefront aberrations and corneal thickness were analyzed. RESULTS: The mean age of subjects was 34.75 +/- 10.08 years. The central corneal thickness was 550.5 +/- 28.459 microm. The mean peripheral thickness was 629.9 +/- 32.1 microm. Central and PCTs were not significantly correlated with corneal or ocular high-order aberrations. Intraocular pressure was significantly correlated with ocular trefoil (r = -0.307, P=0.001). CONCLUSIONS: Central and PCT were not significantly associated with either anterior or posterior corneal Zernike aberrations; in addition, no association with the whole ocular wavefront aberrations was found.

Avellino corneal dystrophy worsening after laser in situ keratomileusis: further clinicopathologic observations and proposed pathogenesis.

PURPOSE: To study the nature of the deposits in Avellino corneal dystrophy (ACD) worsening after laser in situ keratomileusis (LASIK), and suggest a mechanism for histopathogenesis. DESIGN: Interventional case report. METHODS: A 28-year-old woman previously diagnosed with bilateral ACD underwent bilateral LASIK. The corneal dystrophy progressively worsened bilaterally, one year later. A penetrating keratoplasty was subsequently performed on the right eye at 31 years of age, and in the left eye a year later. The clinical and histopathologic findings of the corneal graft of the right eye were reported in the literature, with positivity to the Masson trichrome stain, negative staining with Congo red, and heterozygosity for the Arg124His mutation by serum DNA studies. Histopathologic studies of the corneal graft of the left eye were conducted at the University of Texas Southwestern Medical Center. RESULTS: Histopathologic examination of the excised cornea showed the Masson trichrome positive deposits present from underneath the Bowman layer to the LASIK interface, with absence of deposits posterior to the latter. In contrast to the prior report describing findings in the corneal graft of the left eye, the deposits stained lightly with Congo red, but failed to show birefringence under polarized light, or fluorescence with thioflavin T. CONCLUSION: Accelerated deposits developing after LASIK in ACD eyes seem to harbor pre-amyloid features. The epithelium is likely to be the culprit, in a pathway independent of with human transforming growth hormone beta (TGF-beta), with deposits developing in the anterior stroma and the stromal interface.

Assessment of keratocyte activation following LASIK with flap creation using the IntraLase FS60 laser.

PURPOSE: To assess the response of corneal keratocytes to the IntraLase FS60 femtosecond laser using attenuated steroids. METHODS: Thirty patients (30 eyes) who underwent LASIK with the IntraLase FS60 were assessed by clinical examination and confocal microscopy 3 months postoperatively. Postoperative steroid regimen was Econopred Plus (Alcon Laboratories Inc) every hour for 1 day and four times daily for 7 days. RESULTS: No cornea had clinically significant flap interface haze. Two corneas had trace haze at the interface detected by slit-lamp examination; both showed significant keratocyte activation by confocal microscopy. Overall, some degree of keratocyte activation was detected at the flap interface in 10 of 30 eyes. The measured interface reflectivity was 328.8 +/- 85.0 confocal backscatter units (CBU) in eyes with activated keratocytes and 88.9 +/- 74.5 CBU for the remaining 19 eyes (P < .001). CONCLUSIONS: With attenuated steroids, keratocyte activation was found in a significant number of eyes, although interface haze was subclinical. A higher steroid dosage might therefore be indicated.

Intraocular lens power calculation after myopic laser in situ keratomileusis: Estimating the corneal refractive power.

PURPOSE: To derive regression-based formulas and identify essential dependent variables to estimate refractive corneal power after myopic laser in situ keratomileusis (LASIK). SETTING: University of Texas Southwestern Medical Center at Dallas, Dallas, Texas, USA. METHODS: A retrospective data review of 30 eyes (23 patients) having myopic LASIK followed by phacoemulsification and posterior chamber intraocular lens (IOL) implantation in the same eye gathered the following: pre-LASIK and post-LASIK refractions and topographies, axial length, IOL type and power, and spherical equivalent (SE) refraction 3 months after phacoemulsification. Using the double-K Holladay 1 formula, the refractive corneal power in each eye was back-calculated. Regression formulas were derived and compared with current corneal power estimation methods. RESULTS: The multiple regression formula based on the average corneal power in the central 3.0 mm area (ACCP3 mm) and the change (Delta) in SE (SEpostLASIK-SEpreLASIK) was simplified to ACCPadj=ACCP3mm-0.16DeltaSE, with the highest Pearson correlation coefficient (r=0.989) and lowest absolute corneal power estimation error (0.30 diopter [D]+/-0.30 (SD)). Regression based on ACCP3 mm alone yielded 0.980 and 0.49+/-0.40 D, respectively. Using SimK with DeltaSE resulted in a lower r value (0.971) and larger absolute corneal power estimation error (0.65+/-0.44 D) (P=.0014). The clinical history methods yielded 0.909 and 1.09+/-0.868 D, respectively (P=.0005). CONCLUSION: The regression formula based on ACCP3mm and DeltaSE was very accurate in predicting refractive corneal power after myopic LASIK followed by formulas based on ACCP3mm alone and SimK and DeltaSE, all of which consolidate the validity of similar previously suggested methods, including EffRPadjusted.

Impact on ocular surface evaporation of an artificial tear solution containing hydroxypropyl guar.

OBJECTIVE: To determine whether any acute effects on evaporative parameters are produced when using a solution containing Hydroxypropyl (HP) (Systane) versus normal saline solution in the eyes of patients with Keratoconjunctivis Sicca at 30 and 60 minutes postinstillation. METHODS: Randomized double-blinded placebo-control 2-period cross-over clinical trial. Twelve patients with a clinical diagnosis of Keratoconjunctivis Sicca were enrolled in this study. Aqueous tear evaporation was measured at baseline, i.e., before the application of drops on the eye, and at 30 and 60 minutes after instillation of one 40 microL drop of either the HP-Guar containing drop or normal saline on two separate days. Statistical analysis included descriptive data analysis and paired t test. RESULTS: Hydroxypropyl-Guar resulted in a decrease in aqueous tear evaporation at 30 minutes postinstillation under 25% to 35% relative humidity (RH) (13.2% reduction, P=0.044) and 35% to 45% RH (10% reduction, P=0.028) conditions. The effect of HP-Guar at 60 minutes postinstillation also decreased aqueous tear evaporation but to a lesser degree. Normal saline solution produced no statistically significant increases and decreases of evaporation. CONCLUSIONS: Aqueous tear evaporation contributes significantly to aqueous tear loss and is humidity dependent. An HP-guar containing solution decreased aqueous tear evaporation 30 and 60 minutes after application. The use of topical medication with known antievaporative effect may be beneficial in dry eye therapy. This effect may also be achieved in normal eyes or sub-clinical dry eyes when in low RH environments.

Severe reactive ischemic posterior segment inflammation in acanthamoeba keratitis: a new potentially blinding syndrome.

OBJECTIVE: To describe a newly recognized clinical syndrome in Acanthamoeba keratitis consisting of severe reactive ischemic posterior segment vascular inflammation. DESIGN: Noncomparative, retrospective, single-institution observational case series. PARTICIPANTS: Five eyes of 5 patients with Acanthamoeba keratitis. METHODS: A retrospective review of the records of patients diagnosed with Acanthamoeba keratitis between January 1, 1995, and December 1, 2005, was conducted to identify those who underwent eventual enucleation. Five enucleated eyes of 118 eyes with Acanthamoeba keratitis were identified. MAIN OUTCOME MEASURES: History, clinical examination results, available laboratory study results, and histopathologic examination results. RESULTS: Histopathologic examination showed Acanthamoeba cysts in the cornea in 4 eyes, whereas it failed to demonstrate amebic cysts or trophozoites in the posterior segment of all eyes studied and unexpectedly revealed chronic chorioretinal inflammation with perivascular lymphocytic infiltration and diffuse neuroretinal ischemia in 4 of 5 eyes. Retinal artery thrombosis was present in 3 of the 4 involved eyes, and central retinal artery and vein thrombosis was found in 1 eye. Hematologic studies in 3 patients showed abnormal anticardiolipin antibody levels in 1 patient and factor V Leiden deficiency in another. CONCLUSIONS: Prolonged Acanthamoeba keratitis can result in a severe sterile ischemic posterior segment inflammation that is potentially blinding, especially in patients with underlying hypercoagulation disorders.

Wavefront-guided LASIK for myopia using the LADAR CustomCornea and the VISX CustomVue.

PURPOSE: To evaluate the objective and subjective visual outcomes and refractive results of wavefront-guided LASIK with LADAR CustomCornea and VISX CustomVue. METHODS: This prospective randomized single-institution multisurgeon study comprised 100 eyes of 58 patients (50 eyes on each laser platform). Uncorrected visual acuity (UCVA), best spectacle-corrected visual acuity (BSCVA), and manifest refraction were measured postoperatively at 1 day, 1 week, 1 month, and 3 months. Contrast sensitivity, higher order aberrations measurement, and a subjective vision questionnaire were performed preoperatively and at 3 months. RESULTS: Preoperatively, the CustomCornea group had a mean manifest sphere of -3.58 +/- 1.61 diopters (D) (range: -0.50 to -7.25 D), cylinder of +0.64 +/- 0.45 D (range: 0 to +1.75 D), and manifest refractive spherical equivalent (MRSE) of -3.26 +/- 1.56 D. The CustomVue group had a manifest sphere of -4.00 +/- 1.69 D (range: -1.50 to -7.50 D), cylinder of +0.60 +/- 0.52 D (range: 0 to +2.00 D), and MRSE of -3.70 +/- 1.64 D. At 3 months, 94% of CustomCornea eyes and 84% of CustomVue eyes had UCVA > or = 20/20 (P = .20). Twenty-four percent of CustomVue eyes and 22% of CustomCornea eyes gained 1 line of BSCVA. In both groups, 96% of eyes were within 0.50 D of emmetropia. Mean CustomCornea glare contrast sensitivity improved (P = .04) whereas more eyes improved than worsened in both groups. Spherical aberration and total higher order aberrations increased, and trefoil decreased in both groups. A decrease in coma was noted in 70% of CustomCornea eyes. CONCLUSIONS: Wavefront-guided LASIK with both platforms is safe, effective, and delivers excellent visual results. CustomCornea improves contrast sensitivity under glare conditions.