Glauco Reggiani Mello

Association between the percent tissue altered and post-laser in situ keratomileusis ectasia in eyes with normal preoperative topography.

PURPOSE To investigate the association of a novel metric, percent tissue altered, with the occurrence of ectasia after laser in situ keratomileusis (LASIK) in eyes with normal corneal topography and to compare this metric with other recognized risk factors. DESIGN Retrospective case-control study. METHODS The study included 30 eyes from 16 patients with bilateral normal preoperative Placido-based corneal topography that developed ectasia after LASIK (ectasia group) and 174 eyes from 88 consecutive patients with uncomplicated LASIK and at least 3 years of postoperative follow-up. The following metrics were evaluated: age, preoperative central corneal thickness, residual stromal bed, Ectasia Risk Score System scores, and percent tissue altered, derived from [PTA = (FT + AD)/CCT], where FT = flap thickness, AD = ablation depth, and CCT = preoperative central corneal thickness. RESULTS In the ectasia group, percent tissue altered ≥40 was the most prevalent factor (97%), followed by age <30 years (63%), residual stromal bed ≤300 μm (57%), and ectasia risk score ≥ 3 (43%) (P < .001 for all). Percent tissue altered ≥ 40 had the highest odds ratio (223), followed by residual stromal bed ≤ 300 μm (74) and ectasia risk score ≥ 4 (8). Stepwise logistic regression revealed percent tissue altered ≥ 40 as the single most significant independent variable (P < .0001). CONCLUSIONS Percent tissue altered at the time of LASIK was significantly associated with the development of ectasia in eyes with normal preoperative topography and was a more robust indicator of risk than all other variables in this patient population.

Detection of Subclinical Keratoconus Using an Automated Decision Tree Classification

PURPOSE To develop a method for automatizing the detection of subclinical keratoconus based on a tree classification. DESIGN Retrospective case-control study. METHODS setting: University Hospital of Bordeaux. participants: A total of 372 eyes of 197 patients were enrolled: 177 normal eyes of 95 subjects, 47 eyes of 47 patients with forme fruste keratoconus, and 148 eyes of 102 patients with keratoconus. observation procedure: All eyes were imaged with a dual Scheimpflug analyzer. Fifty-five parameters derived from anterior and posterior corneal measurements were analyzed for each eye and a machine learning algorithm, the classification and regression tree, was used to classify the eyes into the 3 above-mentioned conditions. main outcome measures: The performance of the machine learning algorithm for classifying eye conditions was evaluated, and the curvature, elevation, pachymetric, and wavefront parameters were analyzed in each group and compared. RESULTS The discriminating rules generated with the automated decision tree classifier allowed for discrimination between normal and keratoconus with 100% sensitivity and 99.5% specificity, and between normal and forme fruste keratoconus with 93.6% sensitivity and 97.2% specificity. The algorithm selected as the most discriminant variables parameters related to posterior surface asymmetry and thickness spatial distribution. CONCLUSION The machine learning classifier showed very good performance for discriminating between normal corneas and forme fruste keratoconus and provided a tool that is closer to an automated medical reasoning. This might help in the surgical decision before refractive surgery by providing a good sensitivity in detecting ectasia-susceptible corneas.

Outcomes of deep anterior lamellar keratoplasty for keratoconus: learning curve and advantages of the big bubble technique.

Purpose: To evaluate retrospectively the outcomes of a case series of deep anterior lamellar keratoplasties by air dissection (DALK-AD) using the big bubble (BB) technique, in the surgical treatment of keratoconus (KC). Methods: Forty-four consecutive keratoplasties of 42 patients for KC were performed at the French National Reference Center for KC from January 2008 to June 2010 by the same surgeon with the aim of systematically performing DALK-AD with the BB technique. The outcomes of the DALK-AD not converted to penetrating keratoplasty were analyzed, and a learning curve was established to successfully achieve the DALK-AD using the BB technique. Results: Thirty-two DALK-AD procedures were successfully performed among 44 consecutively operated keratoplasties, with 12 being converted to penetrating keratoplasty during the surgical procedure. At 12 months, the mean best-corrected logarithm of the minimum angle of resolution visual acuity was 0.88 ± 0.14 with 93.3% seeing best-corrected visual acuity ≥20/30 and 100% seeing best-corrected visual acuity ≥20/40. The mean gain of visual acuity in logarithm of the minimum angle of resolution lines at 6 and 12 months was 6.12 ± 3.97 (P < 0.0001) and 6.94 ± 4.18 (P < 0.005), respectively. The rate for intraoperative and postoperative complications was 31.8% and 4.5%, respectively. Conclusion: Despite a learning period needed to successfully perform deep lamellar anterior keratoplasty with the BB technique, this approach is safe and provides very good visual outcomes when adequate baring of Descemet membrane is achieved. The learning curve showed that complications related to this technique decrease significantly after the first 10 cases.

Influence of the Reference Surface Shape for Discriminating Between Normal Corneas, Subclinical Keratoconus, and Keratoconus

PURPOSE To compare the discriminating ability of corneal elevation generated by a dual Scheimpflug analyzer calculated with different reference surfaces for distinguishing normal corneas from those with keratoconus and subclinical keratoconus. METHODS A total of 391 eyes of 208 patients were prospectively enrolled in the study and divided into three groups: 167 eyes of 113 patients with keratoconus, 47 contralateral topographically normal eyes of patients with clinically evident keratoconus in the fellow eye, and 177 eyes of 95 refractive surgery candidates with normal corneas. All eyes were measured with a dual Scheimpflug analyzer (GALILEI Analyzer; Ziemer Ophthalmic Systems AG, Port, Switzerland). Maximum elevation values were recorded within the central 5-mm diameter in both anterior and posterior elevation maps. Discriminating ability of corneal elevation measurements obtained by best-fit toric and aspheric (BFTA) and best-fit sphere (BFS) reference surfaces were compared by receiver operator characteristic (ROC) curves. RESULTS ROC curve analysis showed that corneal elevation measured by BFTA had a significantly better ability than with BFS for distinguishing normal corneas from those with keratoconus and forme fruste keratoconus (P = .01). Posterior elevation measured by BFTA had a significantly higher predictive accuracy for forme fruste keratoconus than anterior elevation with an area under ROC curves of 0.88 and 0.80, respectively (P = .01). The sensitivity and specificity achieved with the maximum posterior elevation for detecting keratoconus and forme fruste keratoconus were 99% and 99% for keratoconus and 82% and 80% for forme fruste keratoconus with the cut-off value at 16 and 13 μm, respectively. CONCLUSIONS The ability to discriminate between normal cornea and forme fruste keratoconus with elevation parameters was significantly improved by using BFTA instead of BFS reference surface.

Applications of wavefront technology

&NA; This review of wavefront technology looks at 2 major aspects. The first is the basics and principles of the optics of the eye, how to decompose the wavefront in a more adequate way for interpretation, and how these aberrations affect the visual acuity. It also addresses the diversity and complexity of wavefront sensors; how these devices transform the principles into clinically useful data, with the advantages and limitations of each system. The second major aspect is the clinical uses of the technology: wavefront‐guided and newer and enhanced profiles related to wavefront as well as the limitations of the technology. Finally, recent innovations made possible by wavefront technology that are not limited to refractive surgery are reviewed. Financial Disclosure No author has a financial or proprietary interest in any material or method mentioned.

Response of the posterior corneal surface to myopic laser in situ keratomileusis with different ablation depths.

PURPOSE: To evaluate the posterior corneal surface response at a very early stage after myopic laser in situ keratomileusis (LASIK) with different ablation depths. SETTING: Cole Eye Institute, Cleveland Clinic, Cleveland, Ohio, USA. DESIGN: Cohort study. METHODS: Healthy myopic eyes were divided based on the achieved ablation depth as follows: Group 1, more than 100 μm; Group 2, between 50 μm and 99 μm; Group 3, less than 50 μm. Posterior eccentricity and central (0.0 to 4.0 mm), paracentral (4.0 to 7.0 mm), and peripheral (7.0 to 10.0 mm) posterior corneal curvatures were measured with the Galilei system preoperatively and postoperatively after 1 day, 1 week, and 1 and 3 months. RESULTS: Eighty eyes were evaluated. Posterior surface steepening and a shift toward prolateness occurred in all groups, with a peak within the first week before returning toward the original level after 1 month. The maximum change in the central posterior cornea occurred after 1 day in Group 1 and reached −0.106 diopter (D). This change was statistically significant (P=.03) and statistically greater than the change in Group 2 (mean −0.042 D; P=0.02) and Group 3 (mean −0.026 D; P<.01). This change was not significant after 3 months (P=.5). CONCLUSIONS: Posterior steepening and a shift toward prolateness of the posterior surface were observed very early after myopic LASIK, with a tendency to return toward the preoperative level between 1 month and 3 months. The degree of change was related to the amount of anterior tissue severed. Financial Disclosure: No author has a financial or proprietary interest in any material or method mentioned.

Modulation transfer function and optical quality after bilateral implantation of a +3.00 D versus a +4.00 D multifocal intraocular lens

PURPOSE: To determine whether the improvement in intermediate vision after bilateral implantation of an aspheric multifocal intraocular lens (IOL) with a +3.00 diopter (D) addition (add) occurs at the expense of optical quality compared with the previous model with a +4.00 D add. SETTING: Department of Ophthalmology, University of São Paulo, São Paulo, Brazil. DESIGN: Prospective randomized double‐masked comparative clinical trial. METHODS: One year after bilateral implantation of Acrysof Restor SN6AD1 +3.00 D IOLs or Acrysof Restor SN6AD3 +4.00 D IOLs, optical quality was evaluated by analyzing the in vivo modulation transfer function (MTF) and point‐spread function (expressed as Strehl ratio). The Strehl ratio and MTF curve with a 4.0 pupil and a 6.0 mm pupil were measured by dynamic retinoscopy aberrometry. The uncorrected and corrected distance visual acuities at 4 m, uncorrected and distance‐corrected near visual acuities at 40 cm, and uncorrected and distance‐corrected intermediate visual acuities at 50 cm, 60 cm, and 70 cm were measured. RESULTS: Both IOL groups comprised 40 eyes of 20 patients. One year postoperatively, there were no statistically significant between‐group differences in the MTF or Strehl ratio with either pupil size. There were no statistically significant between‐group differences in distance or near visual acuity. Intermediate visual acuity was significantly better in the +3.00 D IOL group. CONCLUSION: Results indicate that the improvement in intermediate vision in eyes with the aspheric multifocal + 3.00 D add IOL occurred without decreasing optical quality over that with the previous version IOL with a +4.00 D add. Financial Disclosure: No author has a financial or proprietary interest in any material or method mentioned.

Impact of collagen crosslinking on corneal sensitivity in keratoconus patients.

Purpose: To evaluate changes in corneal sensitivity after corneal collagen crosslinking in patients having progressive keratoconus. Methods: Thirty-six consecutive patients having progressive keratoconus were included in the study. The crosslinking surgery was performed in one eye of each patient (study group) and the opposite eye was used as control (control group). The following steps were done in the procedure: central cornea epithelial debridement, riboflavin solution dropping (1 drop every 5 minutes) for 30 minutes, and subsequently, corneal surface irradiation with Ultraviolet A for 30 minutes, keeping the riboflavin instillation while irradiating. The analysis of corneal tactile sensitivity in each patient was performed using the Cochet–Bonnet aesthesiometer at 5 time points: preoperative and 7, 30, 90, and 180 days after surgery. Results: The study enrolled 72 eyes of 36 patients. Considering the eyes submitted to crosslinking, there was a significant statistical difference concerning the tactile corneal sensitivity at all 5 evaluated moments. The median sensitivity at each time point studied was: preoperative, 52.5 mm (range, 25–60 mm); 7 days, 20.0 mm (range, 5–60 mm); 30 days, 32.5 mm (range, 5–60 mm); 90 days, 40.0 mm (range, 10–60 mm) and 180 days, 45.0 mm (range, 25–60 mm) (P < 0.001). The control group showed no statistical difference among all 5 time points (P = 0.160). Conclusions: Corneal crosslinking performed in keratoconus patients induced a considerable decrease in corneal sensitivity. This decrease was more intense at the first week after the procedure, with a progressive recovery up to 6 months.

Corneal Higher Order Aberrations After Myopic Wavefront-optimized Ablation

PURPOSE To analyze the induced corneal higher order aberrations (HOAs) after wavefront-optimized ablation. METHODS Sixty-four myopic eyes that underwent wavefront-optimized myopic LASIK were divided into three groups based on spherical equivalent (SE): low myopia group (23 eyes with SE <-3.00 diopters [D]); moderate myopia group (27 eyes with SE between -3.00 and -6.00 D); and high myopia group (14 eyes with SE >-6.00 D). Total corneal HOA, corneal spherical aberrations, corneal coma through a 6-mm pupil size, and corneal eccentricity were measured with a dual Scheimpflug imaging device preoperatively and 3 months after surgery. RESULTS An overall increase in total corneal HOA was observed with a mean of 0.18±0.18 μm (P<.01), although this induction was not statistically significant in the low myopic group with a mean of 0.006±0.15 μm (P=.85). Root-mean-square spherical aberration varied the most after myopic ablation, with an overall induction of positive spherical aberration of 0.27±0.25 μm (P<.001). CONCLUSIONS Although the wavefront-optimized profile was designed to preserve the preoperative HOAs of the total eye, a significant induction of the corneal HOAs after myopic treatment was observed. The magnitude of the induced corneal HOA was related to the amount of intended correction. Corneal wavefront profiles do not reflect the visual performance; however, they provide relevant information, which may help in optimizing new laser treatment algorithms.

Femtosecond laser photodisruption of the crystalline lens for restoring accommodation.

Presbyopia is defined by the progressive loss of accommodation and subsequently reduced ability to achieve a near focus when distance corrected. This progressive change, despite beginning in childhood, is almost universally clinically relevant after the fifth decade, being responsible for a significant decrease in quality of life. The number of people affected by presbyopia is growing fast due to aging of the population. The mechanism of accommodation is very complex, and the adequate understanding of how it actually works is the first step toward the development of an effective procedure to reverse it. The most widely accepted theory was proposed by Helmholtz and confirmed by more recent studies in primates. It states that the movement of the equatorial edge of the lens is away from the sclera during accommodation and toward the sclera during disaccommodation. To accommodate, a contraction of the ciliary muscle releases the resting tension on the zonular fibers. It releases the equatorial tension on the lens capsule and allows the elasticity of the lens proteins and capsule to change its shape. This causes a decrease in the circumferential lens diameter and increases the curvature of the anterior and posterior lens surfaces. When the ciliary muscle relaxes (ceasing the accommodative effort), it moves toward the sclera pulling the zonular fibers and increasing the tension