Anvil-profiled penetrating keratoplasty: load resistance evaluation.

The aim of this study was to qualitatively evaluate the biomechanical load resistance of different surgical wound configurations (mushroom, zig-zag, anvil and conventional trephination) in penetrating keratoplasty (PK) by designing a 2D and a 3D finite-element biomechanical model of the cornea. A mathematical model of the human cornea was developed, and different geometric configurations for PK were designed. The internal pressure was raised until the wound misaligned; wound prolapse then occurred. Better wound resistance was found in all the laser trephined profiles tested in comparison with the conventional straight one. The anvil profile was more resistant to the increasing internal pressure than was the mushroom or the zig-zag pattern. Thanks to its greater mechanical load resistance, the anvil profile made possible the apposition of a restricted number of sutures and early suture removal. These advantages can contribute to a faster visual recovery in patients undergoing penetrating keratoplasty.

Three-dimensional mapping of the orientation of collagen corneal lamellae in healthy and keratoconic human corneas using SHG microscopy.

Keratoconus is an eye disorder that causes the cornea to take an abnormal conical shape, thus impairing its refractive functions and causing blindness. The late diagnosis of keratoconus is among the principal reasons for corneal surgical transplantation. This pathology is characterized by a reduced corneal stiffness in the region immediately below Bowman's membrane, probably due to a different lamellar organization, as suggested by previous studies. Here, the lamellar organization in this corneal region is characterized in three dimensions by means of second-harmonic generation (SHG) microscopy. In particular, a method based on a three-dimensional correlation analysis allows to probe the orientation of sutural lamellae close to the Bowman's membrane, finding statistical differences between healthy and keratoconic samples. This method is demonstrated also in combination with an epi-detection scheme, paving the way for a potential clinical ophthalmic application of SHG microscopy for the early diagnosis of keratoconus. SHG image acquired with sagittal optical sectioning (A) of a healthy cornea and (B) of a keratoconic cornea. Scale bars: 30 µm.

ESPRESSO: A novel device for laser-assisted surgery of the anterior eye segment.

INTRODUCTION: Merging robotics with laser eye surgery could enhance precision, repeatability and automation. During some eye laser procedures the patient is awake, thus eye stabilization is desired to avoid movements that could affect the treatment. MATERIAL AND METHODS: The ESPRESSO platform has a two-stage actuation system to position a stabilization tool on the eye, a proximity sensing unit to monitor the stabilization tool position, and a sensing unit to monitor the pressure exerted on the eye. The platform is tested in-vitro and ex-vivo with clinicians. A maximum pressure to be exerted on the eye is defined with expert ophthalmic surgeons to be 22 mmHg: physiological intraocular pressure (IOP) range is 10-21 mmHg. This pressure corresponds to a force of 0.3 N. RESULTS: The necessary contact force to have eye fixation (according to the clinicians' feedback) is evaluated: maximum values resulted always below 0.3 N. A maximum IOP increase of 4.67 mmHg is observed, that is a slight variation with respect to the performance of other platforms (IOP elevations up to 328 mmHg). CONCLUSION: Design and initial assessment of the platform is presented. Eye stabilization is performed without exceeding the critical contact force value and causing large/sudden IOP increases.

Bifocal refractive corneal inlay implantation to improve near vision in emmetropic presbyopic patients.

PURPOSE: To evaluate the safety and effectiveness of the Flexivue Microlens corneal inlay for the improvement of near vision in emmetropic presbyopic patients. SETTING: Ophthalmology Department, Misericordia e Dolce Hospital, Prato, Italy. DESIGN: Prospective interventional case series. METHODS: Corneal inlay implantation was performed in nondominant eyes using a 150 kHz femtosecond laser (iFS). Refraction, uncorrected (UNVA) and corrected (CNVA) near visual acuities, uncorrected (UDVA) and corrected (CDVA) distance visual acuities, slitlamp evaluation, wavefront aberrometry, photopic and mesopic contrast sensitivity, anterior segment optical coherence tomography, endothelial cell density, and central corneal thickness measurements were assessed preoperatively and at each postoperative visit. RESULTS: The study evaluated 81 eyes. In 26 eyes, the mean preoperative UNVA and UDVA were 0.76 logMAR and 0.00 logMAR, respectively, compared with 0.10 logMAR and 0.15 logMAR, respectively, 36 months postoperatively. Sixteen (62%) of 26 treated eyes lost more than 1 line of UDVA, and 5 (19%) lost more than 2 lines of UDVA. Two eyes (8%) lost more than 1 line of CDVA at 36 months. The mean binocular UDVA was 0.00 logMAR preoperatively and 0.02 logMAR at 36 months. The mean spherical aberration increased after surgery. Statistically significant differences in the mean mesopic and photopic contrast sensitivities at higher spatial frequencies were found between treated eyes and nontreated eyes. Explantation was performed in 6 treated eyes because of halos, glare, and a reduced UDVA. CONCLUSION: The corneal inlay might be a safe and effective method of improving UNVA in emmetropic presbyopic patients. FINANCIAL DISCLOSURE: Dr. Fantozzi is a member of the Presbia medical advisory board. No other author has a financial or proprietary interest in any material or method mentioned.

An "All-laser" Endothelial Transplant.

The "all laser" assisted endothelial keratoplasty is a procedure that is performed with a femtosecond laser used to cut the donor tissue at an intended depth, and a near infrared diode laser to weld the corneal tissue. The proposed technique enables to reach the three main goals in endothelial keratoplasty: a precise control in the thickness of the donor tissue; its easy insertion in the recipient bed and a reduced risk of donor lenticule dislocation. The donor cornea thickness is measured in the surgery room with optical coherence tomography (OCT), in order to correctly design the donor tissue dimensions. A femtosecond laser is used to cut the donor cornea. The recipient eye is prepared by manual stripping of the descemetic membrane. The donor endothelium is inserted into a Busin-injector, the peripheral inner side is stained with a proper chromophore (a water solution of Indocyanine Green) and then it is pulled in the anterior chamber. The transplanted tissue is placed in the final and correct location and then diode laser welding is induced from outside the eyeball. The procedure has been performed on more than 15 patients evidencing an improvement in surgery performances, with a good recovery of visual acuity and a reduced donor lenticule dislocation event.

Laser-assisted penetrating keratoplasty: 1-year results in patients using a laser-welded anvil-profiled graft.

PURPOSE: To describe a new laser-assisted penetrating keratoplasty technique combining a femtosecond anvil-like trephination pattern with the laser welding procedure. DESIGN: Cohort prospective study with 1 year of follow-up (June 2011 through January 2013). METHODS: This study was performed at Misericordia e Dolce Public Hospital, Prato, Italy. Twenty-four eyes of 22 patients underwent penetrating keratoplasty: 4 had granular dystrophy, 12 had keratoconus in its final stages, 3 had post-herpetic leukoma, and 5 had corneal scars. A femtosecond laser was used to create anvil-profiled cuts in donor and recipient corneas. Diode laser welding was performed, supporting standard suturing. All patients were evaluated for corrected distance visual acuity, pachymetry, manifest astigmatism, and endothelial cell density after 1, 3, 6, and 12 months. RESULTS: Mean ± standard deviation postoperative corrected visual acuity was 0.48 ± 0.23 logarithm of the minimal angle of resolution (logMAR), 0.30 ± 0.18 logMAR, 0.18 ± 0.13 logMAR, and 0.13 ± 0.16 logMAR at 1, 3, 6, and 12 months, respectively. At the same follow-up times, mean pachymetry was 537 ± 57 µm, 533 ± 74 µm, 528 ± 72 µm, and 529 ± 58 µm, respectively; and mean endothelial cell density was 1945 ± 371 cells/mm(2), 1881 ± 410 cells/mm(2), 1781 ± 401 cells/mm(2), and 1730 ± 376 cells/mm(2), respectively. Mean manifest and topographic postoperative astigmatism were: 3.6 ± 2.5 diopters (D) and 4.65 ± 2.57 D at 1 month, 2.93 ± 2.34 D and 4.79 ± 2.85 D at 3 months, 2.82 ± 1.75 D and 3.44 ± 2.28 D at 6 months, and 2.08 ± 1.25 D and 2.73 ± 2.01 D at 12 months, respectively. All surgical operations were successful and without intraoperative complications. CONCLUSIONS: The use of the anvil trephination profile was effective for performing laser-assisted penetrating keratoplasty. The large donor-recipient interface enables the laser welding procedure and good preservation of the recipient's endothelial cell pool.

Morphologic study of the cornea by in vivo confocal microscopy and optical coherence tomography after bifocal refractive corneal inlay implantation.

PURPOSE: To evaluate the biocompatibility of the Flexivue Microlens intracorneal inlay based on healing of corneal wounds and analysis of corneal structural features using in vivo confocal microscopy (IVCM) and anterior segment optical coherence tomography (AS-OCT). SETTING: Ophthalmology Department, Misericordia e Dolce Hospital, Prato, Italy. DESIGN: Case series. METHODS: The intracorneal inlay was inserted in a stromal pocket created in the nondominant eye of emmetropic presbyopic patients using a femtosecond laser. In vivo confocal microscopy and AS-OCT examinations were performed preoperatively and 1, 6, and 12 months postoperatively. RESULTS: The mean follow-up was 7.6 months. In the early postoperative period, IVCM showed intense cellular activity in the stroma around the inlay, edema, inflammation, and degenerative material deposition but normal regularity after 12 months. Anterior segment OCT showed a regular planar shape of the corneal pocket in all eyes. The mean of the side-cut angles was 30.7 degrees. The mean difference between the measured and planned pocket depth was 9.77 µm. At 1 month, hyperreflective areas beneath the inlay and microfolds were observed in 21 of the 52 eyes. After 12 months, the anterior segment profile was regular and interface pocket reflectivity decreased over time. Six patients had inlay removal postoperatively (3 before 6 months; 3 before 12 months); after removal, IVCM and AS-OCT showed clear corneas without signs of irregularity. CONCLUSION: In vivo confocal microscopy and AS-OCT analysis showed that the inlay elicited a low-level wound-healing response in its immediate vicinity with no alteration in the corneal structures. FINANCIAL DISCLOSURE: Dr. M. Fantozzi is a member of the Presbia medical advisory board. No other author has a financial or proprietary interest in any material or method mentioned.

Improving Boston type 1 keratoprosthesis procedure: one-touch femtosecond-assisted preparation and centration of donor carrier tissue.

PURPOSE: We describe a technique to avoid decentration of the visual axis of the Boston type 1 keratoprosthesis (Kpro), performing 2 concentric trephinations with femtosecond laser. METHODS: Two concentric side cuts were performed in a donor cornea using the 150-kHz Intralase FS laser. Within the same applanation procedure, an 8.5-mm-diameter anterior side cut was performed, followed by a concentric 3-mm-diameter anterior side cut. RESULTS: The technique was successfully replicated in 7 cases. CONCLUSIONS: Femtosecond laser-assisted double trephination results in a correctly prepared donor cornea, and in an inner side precisely matched with the prosthesis. At the end of the surgery, the Kpro was correctly centered.

Laser welding in penetrating keratoplasty and cataract surgery in pediatric patients: early results.

PURPOSE: To evaluate the efficacy of diode laser welding to close corneal wounds in penetrating keratoplasty (PKP) and cataract surgery in pediatric patients. SETTING: Ophthalmology Department, Bambino Gesù Children's Hospital, Rome, Italy. DESIGN: Prospective observational study. METHODS: Patients had surgery for congenital cataract (Group 1) or femtosecond laser-assisted PKP (Group 2). The surgery was followed by corneal wound closure using diode laser welding of the stroma. In Group 1, no standard suturing was used. In Group 2, the donor button was sutured onto the recipient using 8 single nylon sutures or a 10-0 nylon running suture (12 passages). Laser welding was then used as an adjunct to the traditional suturing procedure. RESULTS: Group 1 comprised 7 eyes (7 patients; mean age 8.1 years ± 5.3 [SD], range 1 to 15 years) and Group 2, 5 eyes (5 patients; mean age 10.6 ± 3.3 years, range 6 to 15 years). The adhesion of the laser-welded tissues was perfect; there were no collateral effects, and restoration of the treated tissues was optimum. Seidel testing showed no wound leakage during the follow-up. Postoperative astigmatism did not change significantly from the first day after cataract surgery and shifted moderately 3 months after PKP. CONCLUSION: Laser welding of corneal tissue appeared to be safe and effective in children for whom a sutureless surgical procedure is important to reduce the use of anesthesia for suture management, prevent endophthalmitis, and improve the antiamblyopic effect.

Photothermal effects in connective tissues mediated by laser-activated gold nanorods.

We report a study on the application of laser-activated nanoparticles in the direct welding of connective tissues, which may become a valuable technology in biomedicine. We use colloidal gold nanorods as new near-infrared chromophores to mediate functional photothermal effects in the eye lens capsules. Samples obtained ex vivo from porcine eyes are treated to simulate heterotransplants with 810-nm diode laser radiation in association with a stain of gold nanorods of aspect ratio approximately 4. This stain is applied at the interface between a patch of capsule from a donor eye and the capsule of a recipient eye. Then, by administration of laser pulses of 40 msec and approximately 100-140 J/cm(2), we achieved the local denaturation of the endogenous collagen filaments, which reveals that the treated area reached temperatures above 50 degrees C. The thermal damage is confined within 50-70 mum in a radial distance from the irradiated area.

A new technique for the closure of the lens capsule by laser welding.

A new method is presented for the closure of the lens capsule based on laser welding of suitably prepared patches of anterior capsular tissue. Experiments were performed in freshly enucleated porcine eyes. The patches were previously stained with a solution of indocyanine green in sterile water and then welded on the recipient capsule by means of diode laser radiation at 810 nm. The welded tissue revealed mechanical properties comparable to those of healthy tissue. This technique is proposed to repair capsular breaks and to provide the closure of the capsulorhexis in lens refilling procedures.

Laser tissue welding in ophthalmic surgery.

Laser welding of ocular tissues is an alternative technique or adjunct to conventional suturing in ophthalmic surgery. It is based on the photothermal interaction of laser light with the main components of the extracellular matrix of connective tissues. The advantages of the welding procedure with respect to standard suturing and stapling are reduced operation times, lesser inflammation, faster healing and increased ability to induce tissue regeneration. The procedure we set up is based on the use of an infrared diode laser in association with the topical application of the chromophore Indocyanine Green. Laser light may be delivered either continuously or in pulses, thus identifying two different techniques that have been applied clinically in various types of transplants of the cornea.

Microscopic characterization of collagen modifications induced by low-temperature diode-laser welding of corneal tissue.

BACKGROUND AND OBJECTIVE: Laser welding of corneal tissue that employs diode lasers (810 nm) at low power densities (12-20 W/cm(2)) in association with Indocyanine Green staining of the wound is a technique proposed as an alternative to conventional suturing procedures. The aim of this study is to evaluate, by means of light (LM) and transmission electron microscopy (TEM) analyses, the structural modifications induced in laser-welded corneal stroma. MATERIALS AND METHODS: Experiments were carried out in 20 freshly enucleated pig eyes. A 3.5 mm in length full-thickness cut was produced in the cornea, and was then closed by laser welding. Birefringence modifications in samples stained with picrosirius red dye were analyzed by polarized LM to assess heat damage. TEM analysis was performed on ultra-thin slices, contrasted with uranyl acetate and lead citrate, in order to assess organization and size of type I collagen fibrils after laser welding. RESULTS: LM evidenced bridges of collagen bundles between the wound edges, with a loss of regular lamellar organization at the welded site. Polarized LM indicated that birefringence properties were mostly preserved after laser treatment. TEM examinations revealed the presence of quasi-ordered groups of fibrils across the wound edges preserving their interfibrillar spacing. These fibrils appeared morphologically comparable to those in the control tissue, indicating that type I collagen was not denatured during the diode laser corneal welding. CONCLUSIONS: The preservation of substantially intact, undenatured collagen fibrils in laser-welded corneal wounds supported the thermodynamic studies that we carried out recently, which indicated temperatures below 66 degrees C at the weld site under laser irradiation. This observation enabled us to hypothesize that the mechanism, proposed in the literature, of unwinding of collagen triple helixes followed by fibrils "interdigitation" is not likely to occur in the welding process that we set up for the corneal suturing.

Laser-assisted corneal welding in cataract surgery: retrospective study.

PURPOSE: To evaluate the efficacy of laser welding to close corneal wounds in cataract surgery. SETTING: Department of Ophthalmology, Hospital of Misericordia e Dolce, Prato, Italy. METHODS: This retrospective nonrandomized interventional case series included 20 eyes of 20 patients. All eyes had cataract with visual acuity worse than 20/200. Ten patients had phacoemulsification surgery, and 10 had extracapsular cataract extraction (ECCE). Surgeries were followed by laser-assisted closure of the corneal wounds by diode laser welding of the stroma using a technique established in animal models. Preoperative and postoperative (1, 3, 7, 30, and 90 days) astigmatism, level of inflammation, Seidel testing, and endothelial cell counts were obtained. RESULTS: There were minor differences in preoperative and postoperative astigmatism except in 1 eye in the ECCE group. The Seidel test showed no wound leakage during the follow-up examinations, and endothelial cell loss was similar to that published for standard surgical cataract procedures. No collateral effects of the laser welding were detected, nor was postoperative inflammation. CONCLUSIONS: Astigmatism was slightly affected by the use of laser welding for corneal wound closure after phacoemulsification and ECCE. The laser-assisted corneal sealing procedure was rapid and safe and could serve as an alternative to corneal suturing, with significant potential applications for the closure of longer incisions, such as those used in penetrating keratoplasty.

Experimental and model analysis on the temperature dynamics during diode laser welding of the cornea.

Corneal laser welding is a technique used clinically to induce the immediate sealing of corneal wounds. We present an experimental and model analysis of the temperature dynamics during diode laser-induced corneal welding, which is aimed at characterizing the mechanism of tissue fusion. Ex vivo tests were performed on porcine eyes in the typical irradiation conditions used for laser-induced suturing in cornea transplant. Three laser power densities (12.5 W/cm(2), 16.7 W/cm(2), 20.8 W/cm(2)) were tested. The superficial temperature of the cornea was measured by means of an infrared thermocamera. Experimental data were compared with the results of a three-dimensional (3D) model of a laser-welding process in the cornea, solved by the use of the Finite Element Method (FEM). The model solution and experimental results showed good agreement. The model was thus used to estimate the temperature enhancement inside the corneal wound and to calculate the thermal damage inside the tissue. The results indicated a selective, spatially confined heating effect that occurred at operative temperatures (59 to 66 degrees C) close to intermediate denaturation points of the stromal collagen, before its complete disorganization. No significant heat damage to the region of the laser-treated wound was evidenced in the operative irradiation conditions of corneal welding.

Experimental study on the healing process following laser welding of the cornea.

An experimental study evaluating the application of laser welding of the cornea and the subsequent healing process is presented. The welding of corneal wounds is achieved after staining the cut walls with a solution of the chromophore indocyanine green, and irradiating them with a diode laser (810 nm) operating at low power (60 to 90 mW). The result is a localized heating of the cut, inducing controlled welding of the stromal collagen. In order to optimize this technique and to study the healing process, experimental tests, simulating cataract surgery and penetrating keratoplasty, were performed on rabbits: conventional and laser-induced suturing of corneal wounds were thus compared. A follow-up study 7 to 90 days after surgery was carried out by means of objective and histological examinations, in order to optimize the welding technique and to investigate the subsequent healing process. The analyses of the laser-welded corneas evidenced a faster and more effective restoration of the architecture of the stroma. No thermal damage of the welded stroma was detected, nor were there foreign body reactions or other inflammatory processes.

Carbonic anhydrase inhibitors: topically acting antiglaucoma sulfonamides incorporating esters and amides of 3- and 4-carboxybenzolamide.

Reaction of 3- and 4-carboxybenzenesulfonyl chloride with 5-amino-1,3,4-thiadiazole-2-sulfonamide/5-imino-4-methyl-delta(2)-1,3,4-thiadiazoline-2-sulfonamide afforded two series of benzolamide analogues to which the carboxyl moiety has been derivatized as esters or amides, in order to reduce their very polar character. The new derivatives showed low nanomolar affinity for three carbonic anhydrase (CA) isozymes, CA I, II and IV, and were effective as topical antiglaucoma agents in normotensive rabbits. Efficacy of several of the new sulfonamides reported was better than that of the standard drugs dorzolamide and brinzolamide, whereas their duration of action was prolonged as compared to that of the clinically used drugs.

Carbonic anhydrase inhibitors with strong topical antiglaucoma properties incorporating a 4-(2-aminopyrimidin-4-yl-amino)-benzenesulfonamide scaffold.

Reaction of 4-(2-amino-pyrimidin-4-yl-amino)-benzenesulfonamide with alkyl/aryl-sulfonyl halides, acyl halides or arysulfonyl isocyanates afforded a series of derivatives which were tested for inhibition of three carbonic anhydrase (CA) isozymes. These compounds were designed in such a way as to (i) strongly inhibit several CA isozymes involved in aqueous humor secretion within the eye (such as CA II and CA IV), and (ii) to possess a pharmacological profile that allows easy penetration through the cornea, when administered as eye drops in solution or suspension, constituting thus a valuable therapeutic approach for glaucoma. Several of the obtained inhibitors showed low nanomolar affinities for the two isozymes involved in aqueous humor secretion, CA II and CA IV. Furthermore, in normotensive and hypertensive rabbits, some of them showed an effective and prolonged intraocular pressure (IOP) lowering when administered topically, as 2% suspensions/solutions.

Carbonic anhydrase inhibitors. A general approach for the preparation of water-soluble sulfonamides incorporating polyamino-polycarboxylate tails and of their metal complexes possessing long-lasting, topical intraocular pressure-lowering properties.

Reaction of polyamino-polycarboxylic acids or their dianhydrides with aromatic/heterocyclic sulfonamides possessing a free amino/imino/hydrazino/hydroxy group afforded mono- and bis-sulfonamides containing polyamino-polycarboxylic acid moieties in their molecule. The acids/anhydrides used in synthesis included IDA, NTA, EDDA, EDTA and EDTA dianhydride, DTPA and DTPA dianhydride, EGTA and EGTA dianhydride, and EDDHA, among others. All the newly prepared derivatives showed strong affinity toward isozymes I, II, and IV of carbonic anhydrase (CA). Metal complexes of the new compounds have also been prepared. Metal ions used in such preparations included di- and trivalent main-group and transition cations, such as Zn(II), Cu(II), Al(III), etc. Some of the new sulfonamides/disulfonamides obtained in this way, as well as their metal complexes, behaved as nanomolar CA inhibitors against isozymes II and IV, being slightly less effective in inhibiting isozyme I. Some of these sulfonamides as well as their metal complexes strongly lowered intraocular pressure (IOP) when applied topically, directly into the normotensive/glaucomatous rabbit eye, as 1-2% water solutions/suspensions. The good water solubility of these sulfonamide CA inhibitors, correlated with the neutral pH of their water solutions used in the ophthalmologic applications and the long duration of action of the IOP-lowering effect, makes them interesting candidates for developing novel types of antiglaucoma drugs devoid of serious topical side effects.

Carbonic anhydrase inhibitors: synthesis of water soluble sulfonamides incorporating a 4-sulfamoylphenylmethylthiourea scaffold, with potent intraocular pressure lowering properties.

Reaction of thiophosgene with 4-aminomethyl-benzenesulfonamide afforded 4-isothiocyanatomethyl-benzenesulfonamide, which by reaction with amines, amino acids and oligopeptides, lead to a series of new sulfonamides incorporating a 4-sulfamoylphenylmethylthiourea scaffold. These new thioureas showed strong affinities towards isozymes I, II and IV of carbonic anhydrase (CA, EC 4.2.1.1). In vitro inhibitory potency was good (in the low nanomolar range) for the derivatives of: amino-benzoic acids, beta-phenyl-serine, alpha-phenyl-glycine, for those incorporating hydroxy- and mercapto-amino acids (Ser, Thr, Cys and Met), hydrophobic amino acids (Val, Leu, Ile), aromatic amino acids (Phe, His, Trp, Tyr; DOPA); dicarboxylic amino acids as well as di-/tri-/tetrapeptides among others. Such CA inhibitors displayed very good water solubility (in the range of 2-3%) as sodium (carboxylate) salts, with pH values for the solutions obtained of 6.5-7.0. Furthermore, in normotensive rabbits, some of them showed an effective and prolonged intraocular pressure (IOP) lowering when administered topically, as 2% solutions.