Neil J. Friedman

Femtosecond laser capsulotomy.

PURPOSE: To evaluate a femtosecond laser system to create the capsulotomy. SETTING: Porcine and cadaver eye studies were performed at OptiMedica Corp., Santa Clara, California, USA; the human trial was performed at the Centro Laser, Santo Domingo, Dominican Republic. DESIGN: Experimental and clinical study. METHODS: Capsulotomies performed by an optical coherence tomography–guided femtosecond laser were evaluated in porcine and human cadaver eyes. Subsequently, the procedure was performed in 39 patients as part of a prospective randomized study of femtosecond laser‐assisted cataract surgery. The accuracy of the capsulotomy size, shape, and centration were quantified and capsulotomy strength was assessed in the porcine eyes. RESULTS: Laser‐created capsulotomies were significantly more precise in size and shape than manually created capsulorhexes. In the patient eyes, the deviation from the intended diameter of the resected capsule disk was 29 μm ± 26 (SD) for the laser technique and 337 ± 258 μm for the manual technique. The mean deviation from circularity was 6% and 20%, respectively. The center of the laser capsulotomies was within 77 ± 47 μm of the intended position. All capsulotomies were complete, with no radial nicks or tears. The strength of laser capsulotomies (porcine subgroup) decreased with increasing pulse energy: 152 ± 21 mN for 3 μJ, 121 ± 16 mN for 6 μJ, and 113 ± 23 mN for 10 μJ. The strength of the manual capsulorhexes was 65 ± 21 mN. CONCLUSION: The femtosecond laser produced capsulotomies that were more precise, accurate, reproducible, and stronger than those created with the conventional manual technique. Financial Disclosure: The authors have equity interest in OptiMedica Corp., which manufactures the femtosecond laser cataract system.

Femtosecond Laser–Assisted Cataract Surgery with Integrated Optical Coherence Tomography

An image-guided, femtosecond laser can create precisely placed, accurate cuts in the eye to improve cataract surgery. The Power of Light As Star Wars fans know, a lightsaber fares better against the Dark Force than does a metal sword. Ophthalmologists, who battle the darkening forces of eye disease, have also learned this lesson, replacing steel scalpels with lasers for creating precise, controlled incisions in the eye. Laser-assisted in situ keratomileusis—commonly known as LASIK surgery—corrects myopia (nearsightedness) and other refractive errors in millions of people each year. Now, Palanker et al. used this approach to devise a more precise, reproducible and automated way to remove cataracts. The authors combine the precise cuts of a laser with the imaging sophistication of optical coherence tomography, a method that uses interference of coherent light scattered by biological tissues to create three-dimensional images of their internal structure. On the basis of the individual patient’s eye anatomy, the laser system calculates the optimal set of cutting patterns for cataract removal and directs the laser to execute these slices, resulting in fast, clean surgery. Two light-based methods made this surgical advance possible. The first, the femtosecond laser, is ideal for use deep inside a fragile eye. Unlike longer pulse lasers, which melt and boil their targets away, producing significant collateral damage to adjacent structures, femtosecond light pulses can turn the material in the focal spot into ionized plasma, allowing dissection of transparent tissues without heat accumulation and minimal disturbance to the surroundings. The resulting cut is smooth and precise. The second method—optical coherence tomography (OCT)—takes advantage of slight variations in the refractive properties of living tissues. Coherent light scattered by structures within the eye allows reconstruction of a 3D image of the live tissue. Palanker et al.’s instrument uses this imaging technique to map the cornea, iris and crystalline lens within the patient’s eye and precisely position the various laser cuts. The laser makes a circular opening in the lens capsule (the membrane that surrounds the lens itself), sections the opaque lens into small pieces that are easily removed, and carves a partial incision in the cornea for later completion of surgery and insertion of the artificial lens under sterile conditions. The laser-created edges in the lens capsule are stronger than those made manually, so they better resist damage when the opaque lens is removed or the new lens is implanted. All the laser cuts are produced without perforating the cornea, so that the procedure can be performed outside the operating room. The laser can also be used to cut the corneal surface for correction of astigmatism and for creating a port for surgical instruments in the operating room. Although the new instrument plans and performs incisions much more accurately than do currently available tools, a surgeon still must remove the lens manually. The benefits of the more precise surgical incisions on visual acuity in patients with various types of intraocular lenses will need to be ascertained in a larger prospective trial, although the preliminary data in the paper are promising and indicate that the laser procedure is safe for ocular tissues. This new instrument will arm surgeons with a precise and automated lightsaber with which to battle the darkening forces of cataracts. About one-third of people in the developed world will undergo cataract surgery in their lifetime. Although marked improvements in surgical technique have occurred since the development of the current approach to lens replacement in the late 1960s and early 1970s, some critical steps of the procedure can still only be executed with limited precision. Current practice requires manual formation of an opening in the anterior lens capsule, fragmentation and evacuation of the lens tissue with an ultrasound probe, and implantation of a plastic intraocular lens into the remaining capsular bag. The size, shape, and position of the anterior capsular opening (one of the most critical steps in the procedure) are controlled by freehand pulling and tearing of the capsular tissue. Here, we report a technique that improves the precision and reproducibility of cataract surgery by performing anterior capsulotomy, lens segmentation, and corneal incisions with a femtosecond laser. The placement of the cuts was determined by imaging the anterior segment of the eye with integrated optical coherence tomography. Femtosecond laser produced continuous anterior capsular incisions, which were twice as strong and more than five times as precise in size and shape than manual capsulorhexis. Lens segmentation and softening simplified its emulsification and removal, decreasing the perceived cataract hardness by two grades. Three-dimensional cutting of the cornea guided by diagnostic imaging creates multiplanar self-sealing incisions and allows exact placement of the limbal relaxing incisions, potentially increasing the safety and performance of cataract surgery.

Limbal relaxing incisions with cataract surgery.

Purpose: To evaluate the effectiveness of limbal relaxing incisions (LRIs) for correcting corneal astigmatism during cataract surgery. Setting: Cullen Eye Institute, Houston, Texas, USA. Methods: In 12 eyes of 11 patients, cataract surgery was combined with LRIs. The LRIs were made according to a modified Gills nomogram and were based on preoperative corneal astigmatism determined with standard keratometry and computerized videokeratography (EyeSys Corneal Analysis System™ Version 3.2). Results: The mean preoperative keratometric cylinder was 2.46 ± 0.81 diopters (D). At 1 month postoperatively, mean arithmetic reduction in keratometric cylinder was 1.12 ± 0.74 D, and the with‐the‐wound (WTW) change (calculated by Holladay, Cravy, Koch vector analysis formula) was ‐0.70 ± 0.44. From 1 day to 1 month postoperatively, there was 0.55 D of WTW regression with minimal change in the mean cylindrical axis. There were no overcorrections. Conclusion: Limbal relaxing incisions are a practical, simple, and forgiving approach to the correction of astigmatism during cataract surgery.

Optical patient interface in femtosecond laser-assisted cataract surgery: Contact corneal applanation versus liquid immersion

Purpose To compare 2 optical patient interface designs used for femtosecond laser–assisted cataract surgery. Setting Optimedica Corp., Santa Clara, California, USA, and Centro Laser, Santo Domingo, Dominican Republic. Design Experimental and clinical studies. Methods Laser capsulotomy was performed during cataract surgery with a curved contact lens interface (CCL) or a liquid optical immersion interface (LOI). The presence of corneal folds, incomplete capsulotomy, subconjunctival hemorrhage, and eye movement during laser treatment were analyzed using video and optical coherence tomography. The induced rise of intraocular pressure (IOP) was measured in porcine and cadaver eyes. Results Corneal folds were identified in 70% of the CCL cohort; 63% of these had areas of incomplete capsulotomies beneath the corneal folds. No corneal folds or incomplete capsulotomies were identified in the LOI cohort. The mean eye movement during capsulotomy creation (1.5 sec) was 50 μm with a CCL and 20 μm with an LOI. The LOI cohort had 36% less subconjunctival hemorrhage than the CCL cohort. During suction, the mean IOP rise was 32.4 mm Hg ± 3.4 (SD) in the CCL group and 17.7 ± 2.1 mm Hg in the LOI group. Conclusions Curved contact interfaces create corneal folds that can lead to incomplete capsulotomy during laser cataract surgery. A liquid interface eliminated corneal folds, improved globe stability, reduced subconjunctival hemorrhage, and lowered IOP rise. Financial Disclosure Drs. Talamo, Culbertson, Batlle, Feliz, and Palanker are consultants to and Messrs. Gooding, Angeley, Schuele, Marcellino, and Andersen, and Ms. Essock‐Burns are employees of Optimedica Corp., Sunnyvale, California, USA.

Evaluation of relationships among refractive and topographic parameters

PURPOSE To examine the relationships among several refractive and topographic parameters. SETTING Cullen Eye Institute Department of Ophthalmology, Baylor College of Medicine, Houston, Texas, USA. METHODS Using computerized videokeratography (EyeSys Corneal Analysis System), 287 corneas of 150 patients were retrospectively analyzed. The Holladay Diagnostic Summary (HDS) refractive maps were used to evaluate relationships among variables of the HDS and refractive error. RESULTS Myopic spherical equivalent refraction (P = .0003) and more negative asphericity (Q-values) (P = .0119) were correlated with steeper corneas. The Q-values were less negative in eyes with moderate myopia (2.0 to 6.0 diopters [D]) than in those with hyperopia (1.0 D or greater). The Q-values below -0.3 were correlated with less favorable values for predicted corneal acuity and corneal uniformity index values. Mean corneal curvature measurements obtained by computerized videokeratography and standard keratometry showed a strong degree of correlation (P = .0001). CONCLUSION As the degree of myopia and negative asphericity increased, the corneal radius of curvature decreased. Corneal Q-values less than -0.3 were associated with reduced optical performance of the cornea.

Preoperative screening of contact lens wearers before refractive surgery

PURPOSE To evaluate corneal stability, measured by computerized videokeratography (CVK) after discontinuation of contact lens wear in preoperative refractive surgery candidates. SETTING Baylor College of Medicine, Cullen Eye Institute, Houston, Texas, USA. METHODS Topographic differences were analyzed in 136 noncontact lens wearers (NCLW) and 76 contact lens wearers (CLW) (18 rigid gas-permeable contact lenses [RGPCL], 58 soft contact lenses [SCL]) using EyeSys CVK after discontinuation of SCL wear for 2 weeks and RGPCL wear for 5 weeks. RESULTS There were no differences in CVK patterns between the NCLW and the CLW groups. There were no statistically significant differences between the 2 groups in topographic symmetry, asphericity, corneal uniformity index, predicted corneal acuity, and irregular astigmatism. The dioptric range for the axial and the profile difference maps in the CLW group was slightly lower than in the NCLW group. CONCLUSIONS For patients whose manifest refraction and CVK maps were within 0.5 diopters of earlier values, discontinuation of SCL wear for 2 weeks and RGPCL wear for 5 weeks was adequate for the cornea to return to its baseline topographic state.

Corneal Topographic Changes Induced by Excision of Perilimbal Lesions

BACKGROUND AND OBJECTIVES To evaluate corneal topographic changes induced by excision of two pterygia and a perilimbal dermoid. MATERIAL AND METHODS Using the EyeSys Corneal Analysis System, we retrospectively analyzed the changes in astigmatism, mean central corneal power, and other topographic parameters of three corneas before and after surgical removal of two pterygia and a perilimbal dermoid. RESULTS Marked corneal steepening occurred along the preoperative flat meridian after the excision of the pterygia and dermoid cyst. For each patient, surgery increased the mean central corneal curvature and decreased total astigmatism. CONCLUSION Surgical excision can ameliorate abnormal corneal topographic changes produced by limbal lesions.

Dehiscence of a radial keratotomy incision during clear corneal cataract surgery

Abstract We report a case of dehiscence of a radial keratotomy (RK) incision caused by clear corneal cataract surgery. The patient had had eight‐incision RK in both eyes 9 months previously with enhancement surgery in the left eye 1 month later. Cataract surgery through a clear corneal incision was performed in the right eye and 1 month later, in the left. Surgery in the right eye was uneventful. However, during surgery in the left eye, dehiscence of one radial incision occurred. The wound dehiscence was closed with interrupted sutures, and the patient achieved 20/20 uncorrected visual acuity 1 week after surgery.

Corneal topography classification in myopic eyes based on axial, instantaneous, refractive, and profile difference maps.

PURPOSE To refine and develop systems for classifying the topography of myopic corneas using axial, instantaneous, refractive, and profile difference maps. SETTING Baylor College of Medicine, Cullen Eye Institute Houston, Texas, USA. METHODS Using the EyeSys Corneal Analysis System, computerized videokeratographs of 153 corneas of 78 myopic patients were retrospectively analyzed. Patterns were defined with respect to the mid-dioptric green color. Relationships among pattern types, refractive power, corneal power, corneal uniformity index (CU index), and predicted corneal visual acuity (PC acuity) were calculated. RESULTS Six types of patterns for axial, instantaneous, and refractive maps and 3 types of patterns for the profile difference map were defined. For a given cornea, there was a weak correlation among the patterns in the axial, instantaneous, and profile difference maps. The circular with central irregularity pattern in auto-scale refractive maps and the irregular pattern in profile difference maps and axial maps were correlated with lower CU index and PC acuity values. Clinical classification of instantaneous maps did not contribute substantially to the information provided by axial maps. CONCLUSION Patterns of computerized videokeratographs varied according to the type of topographic map. The classification systems used provide a baseline for analyzing the response of the cornea to various interventions.

Peripheral radial incisions to treat inferior contact lens edge lift after penetrating keratoplasty for keratoconus

Abstract A patient with marked corneal astigmatism and inferior contact edge lift after penetrating keratoplasty for keratoconus had corneal relaxing incisions‐(CRIs) op the donor button and radial incisions on the host cornea. Results were evaluated by computerized videokeratography and by refitting the contact lens. Two pairs of CRIs decreased astigmatism from 11.00 to 4.25 diopters but did not alleviate the contact lens edge lift, which was caused by excessive steepness in the keratoconic host cornea. After 6 radial incisions were made to flatten the inferior host cornea, the peripheral cornea flattened and the patient was successfully refitted with a contact lens.