Jean-Luc Febbraro

Laser in situ keratomileusis for the correction of residual ametropia after penetrating keratoplasty

Purpose: To evaluate the safety, efficacy, and predictability of excimer laser in situ keratomileusis (LASIK) to correct residual myopia and astigmatism after penetrating keratoplasty (PKP). Setting: Buzard Eye Institute, Las Vegas, Nevada, USA. Methods: Twenty‐six eyes had LASIK at least 1 year after PKP. All eyes were followed for at least 6 months after LASIK; 22 eyes were followed for 12 months. Sutures were removed at a mean of 13 months post PKP. Laser in situ keratomileusis was performed with the Chiron Automated Corneal Shaper® microkeratome (Bausch & Lomb) and the Visx Star excimer laser. Before LASIK, the mean spherical equivalent (SE) was −4.94 diopters (D) ± 2.79 (SD) and the mean astigmatism was 2.71 ± 2.33 D; all eyes had regular astigmatism or slightly decentered, irregular astigmatism. Results: At the last follow‐up, the mean postoperative uncorrected visual acuity (UCVA) was 20/30, the mean SE was −0.35 ± 0.65 D, and the mean residual astigmatism was 1.06 ± 0.67 D. Eighty‐six percent of patients had an SE within ±1.00 D of emmetropia and a UCVA of 20/40 or better. Ten eyes (39%) had 1 or more enhancements, which were performed a mean of 6 months after the primary LASIK. Significant complications such as wound dehiscence, epithelial ingrowth, and corneal decompensation did not occur. At the last follow‐up, 18% of patients lost 1 line of best corrected visual acuity and 27% gained 1 line. Conclusion: Laser in situ keratomileusis appeared to be a reliable and safe procedure to correct residual myopia and astigmatism after PKP.

Treatment of mild to moderate keratoconus with laser in situ keratomileusis

PURPOSE To evaluate the effectiveness, stability, and complications of laser in situ keratomileusis (LASIK) to treat myopic astigmatism in patients with keratoconus. SETTING Buzard Eye Institute, Las Vegas, Nevada, USA. METHODS This study included 16 eyes of 9 patients who had keratometric and/or clinical evidence of keratoconus. Mean age was 45 years, and refraction was stable for at least 2 years. Two treatment approaches were evaluated. RESULTS Mean preoperative spherical equivalent was -4.23 diopters (D) +/- 2.14 (SD) with a mean steep keratometry of 46.81 +/- 3.07 D. Mean preoperative keratometric cylinder was 3.08 +/- 2.22 D. Mean postoperative keratometric cylinder was 3.00 +/- 4.78 D and mean spherical equivalent, -0.44 +/- 0.86 D. Mean postoperative steep keratometry was 44.12 +/- 7.17 D. Two eyes lost 1 line of best corrected visual acuity (BCVA), 1 eye lost 3 lines, and 2 lost 4 lines. Penetrating keratoplasty (PKP) was scheduled in 3 eyes 1 to 2 years after the primary LASIK. CONCLUSION The initial visual results appear promising; but longer term results revealed regression of the refractive outcome in some cases. Moreover, despite improvement in the postoperative spherical equivalent and uncorrected visual acuity in most cases, the risk of loss of BCVA and the necessity of performing PKP in 3 cases lead us not to consider LASIK as a primary solution for keratoconus.

Assessment of corneal biomechanical properties in normal tension glaucoma and comparison with open-angle glaucoma, ocular hypertension, and normal eyes.

Purpose:To assess the biomechanical properties of corneas in patients with normal tension glaucoma (NTG) and to compare them with those of patients with primary open-angle glaucoma (POAG), ocular hypertension (OHT), and normal controls (N). Methods:Corneal hysteresis (CH), corneal resistance factor (CRF), Goldmann intraocular pressure (IOPg), and corneal compensated IOP (IOPcc) were obtained using an ocular response analyzer for 28 eyes in 14 patients with NTG, 75 eyes in 38 patients with chronic POAG, 53 eyes of 27 patients with OHT, and 44 eyes of 22 N controls. IOP using Goldmann applanation tonometry (IOPGA) and ultrasonic central corneal thickness (CCT) were also measured for each eye. Analysis of variance test was used for statistical analysis. Results:CH was significantly lower in the NTG group (9.88±2.02 mm Hg) compared with the N group (11.05±1.53 mm Hg; P<0.01). CRF was significantly lower in the NTG group (9.5±1.89 mm Hg) compared with the POAG group (11.15±2.35 mm Hg; P<0.01) and to the N group (11.00±1.75 mm Hg; P<0.01). CCT was not considered significantly different between the 4 groups. However, IOPcc was found to be significantly lower in NTG group compared with the POAG group and OHT group (P<0.001). Conclusion:NTG was associated with significantly lower CRF than chronic POAG and N patients. CH and CRF could be a useful tool in early diagnosis of NTG.

Detection of static cyclotorsion and compensation for dynamic cyclotorsion in laser in situ keratomileusis

PURPOSE: To evaluate the degree of static and dynamic cyclotorsion using a rotational eye tracker in laser in situ keratomileusis (LASIK) to correct myopic astigmatism. SETTING: Rothschild Foundation, Paris, France. DESIGN: Cohort study. METHODS: Laser in situ keratomileusis with active iris registration using a Zyoptix 100 Hz excimer laser with Advanced Control Eyetracking was performed in eyes with myopic astigmatism. In all cases, iris registration was used to evaluate the degree of static cyclotorsion preoperatively and the degree of dynamic cyclotorsion and intraoperatively. The direction, mean values, and ranges of static and dynamic cyclotorsion were recorded. The amplitude of intraoperative cyclotorsion was reported. RESULTS: The study included 74 consecutive eyes (38 patients). The direction of cyclotorsion was not statistically significant. The mean static cyclotorsion was 3.08 degrees ± 2.68 (SD) (range −7.0 to 14.0 degrees) and the mean dynamic cyclotorsion, 3.39 ± 2.94 degrees (range −10.3 to 13.5 degrees). During photoablation, the mean amplitude of cyclotorsion was 2.69 ± 1.63 degrees (range 0.0 to 9.2 degrees). The magnitude of dynamic cyclotorsion was less than 5 degrees in 66% of eyes, 5 degrees or more in 34% of eyes, and 10 degrees or more in 4% of eyes. CONCLUSIONS: Static and dynamic cyclotorsion was detected with a dynamic eye tracker in eyes having LASIK. Rotational movements were mainly static but had significant amplitude during photoablation. Financial Disclosure: No author has a financial or proprietary interest in any material or method mentioned.

One year clinical results of photoastigmatic refractive keratectomy for compound myopic astigmatism

PURPOSE To evaluate the efficacy, predictability, and safety of excimer laser photoastigmatic refractive keratectomy (PARK) to correct compound myopic astigmatism. SETTING Departments of Ophthalmology, Robert Debré Hospital and Rothschild Foundation, Paris, France. METHODS This retrospective study included 27 eyes with compound myopic astigmatism treated with a Nidek EC 5000 excimer laser. The refractive results were measured at 1 year, and the cylindrical component was analyzed by the Alpins method. Mean preoperative myopia was -4.50 diopters (D) (range -0.75 to -4.00 D) and mean preoperative cylinder, -1.64 D (range -0.75 to -4.00 D). RESULTS At 1 year, the spherical equivalent was -0.47 D (range +1.00 to -3.00 D) and residual subjective astigmatism, -0.40 (range -0.25 to -1.50 D). Uncorrected visual acuity of 20/40 or better was obtained in 22 of the 27 eyes; 21 eyes were within +/- 1.0 D of emmetropia. Vector analysis showed a mean coefficient adjustment of 1.50 D +/- 0.53 (SD), a mean axis shift of 2.64 +/- 12.10 degrees, and a mean magnitude of error of 0.45 +/- 0.56 D. Haze was absent in 22 eyes and grade 1+ in 5 eyes. Five eyes gained 1 line of best corrected visual acuity and 3 lost 1 line. No patient lost more than 1 line. CONCLUSION Excimer laser PARK successfully corrected low and moderate myopia combined with up to 4.0 D of astigmatism with a low mean angle of error. To increase the accuracy of toric ablation, specific algorithms for the cylinder component are needed.

Use of Toric IOLs in the Correction of Astigmatism with Cataract Surgery

Toric IOLS provide a safe and effective means of correcting astigmatism at the time of cataract surgery. Little additional risk is involved. Careful surgical planning involves precise preoperative evaluation of the ocular surface, refractive characteristics, and the use of alignment systems. Improvements in IOL design and materials have reduced the need for postoperative enhancements due to IOL rotation. Alignment remains an area of rapid technologic development with intraoperative guidance using microscope-integrated or “heads-up” displays becoming available.

Ten Key Points to Optimize Surgical Correction of Astigmatism

Preoperative measurements of corneal astigmatism need to be sufficiently accurate to reduce preexisting astigmatism to within 0.50 (multifocal IOLs)–0.75 D (monofocal IOLs). Our diagnostic tools include manual or autokeratometers, optical biometry, and, importantly, topography or tomography. A prerequisite condition to guarantee the quality of the measurements is a healthy cornea, without any surface irregularities caused by either deficient tear film or corneal pathology: Corneal astigmatism can be identified with manual and autokeratometers in a repeatable manner. However, these instruments are insufficient because they only measure four points in the central 3 mm of the cornea and are unable to detect astigmatic asymmetries, irregularities, posterior corneal, nor lenticular astigmatism. Optical biometry provides magnitude and axis measurements at various optical zones (1.65, 2.3, or 3.3 mm depending on the instrument) with variable numbers of points (6, 18, and 32). Corneal topography has become a mandatory test prior to toric implantation as it allows for the detection of asymmetric and irregular astigmatism. Comparative studies between manual and automated keratometry, Placido-type topography, and simulated keratometry of Scheimpflug systems showed similar results in terms of anterior corneal magnitude, but axis differences were noted [1–3]. Corneal topographers may usually be considered as the final judge in terms of axis, pending verification of the image quality. Total corneal astigmatism includes anterior and posterior components of the cylinder. Previous methods measured the anterior component only, whereas slit-scanning technology, optical coherence tomography, and Scheimpflug imaging systems allow for the measurement of both anterior and posterior astigmatism. These newer systems use true refractive indices to calculate the anterior and posterior corneal powers (1.376 for the cornea and 1.336 for the aqueous), instead of a standardized corneal refractive index of 1.3375 [4]. Accuracy is still suboptimal, but these devices hold the promise that they can be used to reliably measure posterior astigmatism and optimize the estimation of total corneal astigmatism.

Excimer Laser Correction of Astigmatism: Principles and Clinical Results

Excimer laser photorefractive keratectomy (PRK) was first introduced by Trokel in 1983 to correct myopia [1]. Seiler and coauthors in 1988 proposed this technology to correct astigmatism with T cuts, but the refractive results were not superior to incisional techniques [2]. In 1991, McDonnell published promising clinical results with photoastigmatic refractive keratectomy (PARK) using toric ablation [3]. Since then, more than 20 million excimer laser procedures have been performed, and this technology has become the method of choice to correct both spherical and astigmatic errors. As a result, corneal refractive surgery is the second most frequently performed ocular procedure worldwide, just after cataract surgery.

Cataract Wound Size and Astigmatism

In two decades, the size of sutureless cataract incisions has decreased from an average of 4 mm to less than 2 mm. It is known that clear corneal cataract incisions flatten the incised meridian with steepening 90° away. The magnitude of this surgically induced astigmatism (SIA) is primarily linked to the incision size. In this chapter, we describe the astigmatic effects of 3.2-, 2.2-, and 1.8-mm cataract incisions. A randomized prospective study of 190 eyes undergoing superior clear corneal incision (SCCI) was divided into three groups: 61 eyes with a control 3.2-mm SCCI; 66 eyes with a 2.2-mm SCCI; and 63 eyes with a 1.8-mm SCCI. The with-the-wound (WTW), against-the-wound (ATW), and WTW-ATW changes were calculated using the Holladay-Cravy-Koch formula. The WTW, ATW, and WTW-ATW changes were significantly higher for the control 3.2-mm SCCI than for the 2.2- and 1.8-mm SCCI, and no difference was found between the 2.2- and 1.8-mm SCCI incision groups. In another randomized prospective study of 121 eyes, which compared temporal and superior 2.2-mm CCI, no statistically significant difference of the astigmatic effects between the two incision locations was found. The different SIA found with various incision sizes may lead the surgeon to consider a specific strategy in terms of incision location, particularly for sizes close to 3 mm. Mini 2.2-mm and micro 1.8-mm incisions induce less astigmatism and therefore offer more flexibility in terms of incision placement independently from the steep preoperative astigmatic meridian.

130 - Reproductibilité et valeurs seuils du Système d’Analyse de la Qualité Optique Oculaire (OQAS).

Objectif Verifier la reproductibilite des mesures effectuees par l’Optical Quality Analysing System (OQAS) et obtenir des valeurs seuils chez les sujets normaux. Materiels et Methodes L’OQAS est un instrument qui repose sur l’analyse par double passage de l’image retinienne d’un point source. Il permet de quantifier l’importance de la diffusion oculaire (reduction de la transparence des milieux) et d’obtenir des valeurs. Le Ratio de Strehl (SR), la Fonction de Transfert de Modulation (MTF), et l’Index de Diffusion Oculaire (OSI) ont ete mesures 10 fois de suite dans 11 yeux de 6 sujets normaux et le coefficient de reproductibilite a ete calcule. Un echantillon de 69 yeux de 35 sujets candidats a la chirurgie refractive a egalement subi les mesures de SR, MTF et OSI. Resultats La reproductibilite des mesures concernant la MTF et le SR etait meilleure que celle de l’OSI. La moyenne du SR dans l’echantillon etait de 0.191 +/− 0.057, celle de la MTF (aire sous la courbe) etait de 0.089 +/− 0.036 et celle de l’OSI etait de 1.113 +/− 0.851. Discussion La variabilite des mesures chez les sujets sains est faible et leur valeur eloignee au regard de celles que nous avons obtenues chez des sujets presentant diverses pathologie (cataracte, haze corneen, etc…). Conclusion Les mesures de l’OQAS chez les sujets normaux sont fiables et reproductibles. Les valeurs obtenues permettent de caracteriser l’importance de la diffusion oculaire d’une population de reference. Des etudes complementaires sont necessaires pour etudier la reproductibilite de l’instrument en cas d’alteration des milieux transparents.