Phaco slice and separate.

Phaco slice and separate retains the advantages of the chopping techniques of Nagahara, Koch, and Fukasaku but replaces chopping or snapping with slicing across the center of the phaco-tip-stabilized nucleus using a Nagahara chopper and then repositioning the chopper to optimally separate the divided lens halves. As the lens is rotated in the capsular bag, small pieces of the nuclear pie are sliced off, separated, emulsified, and aspirated. Emulsification and aspiration can alternatively be left until most or all the slices have been made. This technique works with a broader range of lens densities than other chopping techniques and uses no sculpting and very little phaco time. The phaco time required for this technique is relatively independent of nuclear density compared with a sculpting technique.

Dispersive-cohesive viscoelastic soft shell technique.

Based on their physical properties, ophthalmic viscoelastic agents can be divided into 2 groups: higher-viscosity cohesive and lower-viscosity dispersive. Higher-viscosity cohesive agents are best at creating and preserving space, while lower-viscosity dispersive agents are retained better in the anterior chamber and are capable of partitioning spaces. The viscoelastic soft shell technique maximizes the advantages and minimizes the disadvantages of both groups by using dispersive and cohesive agents together in sequence based on the desired surgical goal.

Quantitative method to determine the cohesion of viscoelastic agents by dynamic aspiration.

PURPOSE: To quantitatively determine the cohesion of ophthalmic viscoelastic agents using an in vitro method based on dynamic aspiration kinetics. SETTING: Alcon Laboratories, Inc., Fort Worth, Texas, USA. METHOD: Five viscoelastic agents were tested: Healon GV (sodium hyaluronate 1.4%); Provisc (sodium hyaluronate 1.0%); Healon (sodium hyaluronate 1.0%); Amvisc Plus (sodium hyaluronate 1.6%); Viscoat (sodium hyaluronate 3.0%-chondroitin sulfate 4.0%). Samples were placed into a tared polypropylene container using a positive displacement pipette. Calibrated vacuum was applied for 2 seconds to a polypropylene tip (inner diameter 0.5 mm) lowered into the viscoelastic sample. The quantity of viscoelastic agent remaining in the container after aspiration was determined gravimetrically. The procedure was repeated at various vacuum levels between 100 and 700 mm Hg. The percentage of viscoelastic agent aspirated was plotted against vacuum pressure. The slopes of these curves indicate the relative cohesion of the viscoelastic sample. RESULTS: The cohesion-dispersion indices (percentage viscoelastic agent aspirated/100 mm Hg) were Healon GV (72.3) > Provisc (46.0) > Healon (31.2) = Amvisc Plus (21.4) > Viscoat (3.4). CONCLUSION: The method provided a quantitative basis for the clinical classification of viscoelastic materials as cohesive or dispersive. The aspiration kinetics profile (curve shape), maximum rate of removal, and vacuum levels at which the bolus removal of the viscoelastic agent started (break point) were useful in characterizing the viscoelastic agents. Because the results agree with the clinical impression of cohesion/dispersion, this method may be used to predict the surgical performance of viscoelastic agents.

Prospective, randomized trial comparing Micro Visc Plus and Healon GV in routine phacoemulsification.

PURPOSE: To compare the safety and efficacy of two sodium hyaluronate viscoelastics--MicroVisc Plus and Healon GV--in routine phacoemulsification and evaluate whether these more viscous and cohesive agents offer benefits compared to viscoelastics of standard viscosity and cohesion. SETTING: York Finch Eye Associates and York Finch General Hospital, Toronto, Canada. METHODS: An unmasked, randomized, prospective clinical trial of 100 eyes of 100 patients having routine phacoemulsification with intraocular lens implantation was conducted comparing the safety and efficacy of MicroVisc Plus with those of Healon GV. Preoperative and 6 hour, 1 and 5 days, and 1 and 6 month postoperative assessments included acuity, corneal thickness, intraocular pressure, and surgeon assessment of the task-facilitating efficacy of the viscoelastics. Results were compared with those of a similar trial of MicroVisc and Healon. RESULTS: There were no statistically significant differences between the two treatment groups at any follow-up. The surgeon judged the two viscoelastics to be equivalent, although somewhat different in facilitating surgery. There was significantly less transient postoperative corneal thickening in the Healon GV/MicroVisc Plus group than in the Healon/MicroVisc group. CONCLUSIONS: Healon GV and MicroVisc Plus were safe and provided equal outcomes based on the parameters assessed. MicroVisc Plus' higher zero-shear viscosity caused it to behave slightly differently than Healon GV during surgery. More viscous, cohesive viscoelastics may increase surgical safety.

New method to measure the retention of viscoelastic agents on a rabbit corneal endothelial cell line after irrigation and aspiration.

PURPOSE: To quantify the surface retention of several ophthalmic viscoelastic agents following irrigation and aspiration (I/A) using a new in vitro method. SETTING: Alcon Laboratories, Inc., Fort Worth, Texas, USA. METHODS: A rabbit corneal endothelial cell line was cultured to confluency in 24-well plates, and the cells were labeled quantitatively with internalized neutral red dye. Five ophthalmic viscoelastic agents were applied to cover the monolayer of cells: sodium hyaluronate (Healon, Provisc, and Amvisc Plus), Formulation A (a dispersive, nonproteinaceous, synthetic polymer), and sodium chondroitin sulfate, sodium hyaluronate (Viscoat). Irrigation and aspiration (with fluid turbulence similar to that encountered in phacoemulsification surgery) were performed on each well for 3 minutes, using 120 mL of balanced salt solution with bicarbonate. dextrose, and glutathione (BSS Plus). The cells were treated with an acidified ethanol solution to extract the dye from the cells left without a viscoelastic cover. The extracted dye was measured by spectrophotometry and compared with the total dye recovered from control cells. RESULTS: The retention value, which represented the percentage of cells with viscoelastic retained on the surface, was calculated as follows: Healon, 7; Provisc, 16; Amvisc Plus, 17; Formulation A, 55; Viscoat, 90. On a nonadsorptive, non-cell surface, the retention values of the five viscoelastics were significantly less than those on cells. CONCLUSION: The results of this experimental model suggest that cohesive viscoelastics are readily removed from the cells, while dispersive viscoelastics are highly retained. In addition, mutual surface interaction (electrical charge and other properties) plays a significant role in determining the retention of viscoelastics on the corneal endothelial cell surface following I/A.

HsS versus a balanced salt solution as a corneal wetting agent during routine cataract extraction and lens implantation.

PURPOSE: To evaluate HsS (elastoviscous hylan surgical shield, 0.45%) as an alternative to repeated corneal irrigation with a balanced salt solution during cataract surgery. SETTING: York Finch General Hospital, Toronto, Ontario (Center A), and Centre Hospitalier de St. Laurent, St. Laurent, Quebec (Center B), Canada. METHODS: This dual-center, randomized, prospective clinical trial comprised 60 patients (40 at Center A; 20 at Center B) who had routine small incision cataract surgery (Center A, endolenticular phacoemulsification; Center B, Khoury manual phacofragmentation) with in-the-bag implantation of a posterior chamber intraocular lens. The corneal irrigating fluid was randomly assigned to be HsS or a balanced salt solution. The frequency of required applications, duration of efficacy of each application, and assessment of corneal moisture, clarity, transparency, and reflection in the HsS and balanced salt solution groups were recorded and compared. RESULTS: Mean frequency of applications was 13.9 per procedure in the balanced salt solution group and 1.3 per procedure in the HsS group (P = .0001). Mean duration of effectiveness per application was 23.4 minutes for HsS and 2.0 minutes for balanced salt solution (P = .0001). No significant differences in safety or effect on corneal health were observed between the two solutions. CONCLUSION: The HsS was significantly more effective than a balanced salt solution in maintaining corneal moisture, clarity, and transparency. The use of HsS may be a safer, more effective option in ophthalmic surgery because it minimizes the obstructed visualization of the surgical field caused by frequent corneal irrigation and loss of surgeon concentration.

Prospective, randomized trial of Microvisc and Healon in routine phacoemulsification.

PURPOSE: To compare the safety and efficacy of the new sodium hyaluronate viscoelastic, Microvisc, with those of Healon in routine phacoemulsification. SETTING: York Finch Eye Associates and York Finch General Hospital, Toronto, Ontario, Canada. METHODS: An unmasked, prospective, randomized clinical trial of 100 eyes in 100 patients having routine phacoemulsification and intraocular lens implantation was conducted to compare the safety and efficacy of Microvisc with those of Healon. Visual acuity, corneal thickness, and intraocular pressure were assessed preoperatively and at 6 hours, 1 and 5 days, and 1 and 6 months postoperatively. RESULTS: There were no statistically significant differences between the two treatment groups at any follow-up CONCLUSION: Based on the parameters assessed, both viscoelastic products were safe and provided comparable outcomes.

Pharmacotherapy of photorefractive keratectomy.

PURPOSE: To compare the pharmacotherapeutic practices of high-volume photorefractive keratectomy (PRK) surgeons with suggested practices gleaned from the current literature. SETTING: York Finch Eye Associates, Toronto, Canada. METHODS: Seventy-five ophthalmic surgeons believed by the authors to do a high-volume of PRKs were surveyed over the summer of 1994 about their pharmacotherapeutic practices. The results were compared with suggested practices extracted from a review of the current literature. RESULTS: Relatively consistent approaches to the management of post-PRK pain and prevention of acute post-PRK subepithelial infiltrative keratitis were reported. The administration of topical steroids after PRK was almost universally employed. Post-PRK analgesia was most commonly achieved with nonsteroidal anti-inflammatory drugs (NSAIDs) and a soft contact lens, but surgeons were not convinced of the benefits of long-term NSAID administration to control myopic regression and haze. There seemed to be no agreed-on solution to the infrequent problems of severe haze and regression and steroid-induced elevated intraocular pressure after PRK; however, many useful suggestions for the management of these problems were proposed. CONCLUSION: In general, high-volume PRK surgeons use topical steroids, NSAIDs, and a soft contact lens in the immediate postoperative period, although they are uncertain about the long-term effectiveness of NSAIDs in controlling regression and haze.

Corneal subepithelial infiltrates following excimer laser photorefractive keratectomy.

Corneal subepithelial opacification associated with pain, photophobia, and injection has been reported in the first to third day following photorefractive keratectomy (PRK). Regardless of treatment, the resolution has generally left the patient with permanent corneal scarring and a one to two line reduction in visual acuity. We surveyed 50 PRK surgeons and received responses from 17 on 30 cases of this complication, which occurs in approximately one in 300 cases. The etiology is unknown. Cases were first reported when nonsteroidal anti-inflammatory drugs, with or without occlusive contact lens, were substituted for conventional bandage occlusion in the postoperative protocol for PRK.

Use of topical nonsteroidal anti-inflammatory drugs in excimer laser photorefractive keratectomy.

Nonsteroidal anti-inflammatory drugs (NSAIDs) produce potent analgesic, antipyretic, and anti-inflammatory effects. We studied postoperative pain in 97 consecutive patients having photorefractive keratectomy (PRK) by an excimer laser with different topical NSAID protocols. Treatment with topical homatropine hydrobromide, either diclofenac sodium (Voltaren Ophthalmic) or ketorolac tromethamine (Acular), and a soft contact lens was most effective in achieving post-PRK analgesia. We also studied post-PRK myopic regression in 68 consecutive patients and found that flurbiprofen sodium (Ocufen), when added to topical steroid protocols, significantly reduced myopic regression for one year postoperatively more than steroids alone or steroids and diclofenac sodium. Diclofenac, used with topical steroids, had less of an additive effect on myopic regression than did flurbiprofen. Topical NSAIDs are useful adjuncts to PRK therapy, both to eliminate postoperative pain and to control post-PRK myopic regression.

Determination of haptic position of transsclerally fixated posterior chamber intraocular lenses by ultrasound biomicroscopy.

Transscleral fixation of posterior chamber intraocular lenses has become an increasingly popular procedure in eyes lacking adequate posterior capsular support. The assumption is generally made that these lenses are fixated in the ciliary sulcus. To test this assumption, 17 cases with transsclerally fixated posterior chamber intraocular lenses were examined with ultrasound biomicroscopy, a new method of producing subsurface images in living eyes at microscopic resolution. All lens haptics were easily visualized with this technique. Of 34 haptics in 17 patients, 13 were adequately located in the sulcus region, eight were located posterior to the ciliary processes, and 13 were located anterior to the sulcus region, accompanied by some degree of angle closure. Haptics with a more posterior scleral exit of the suture tended to be located more posteriorly. The cases in which the haptics were located anteriorly had scleral exit points from 1 mm to 2 mm from the limbus. The surgical placement of transsclerally fixated lenses is a blind procedure in most cases. Our series demonstrates the difficulty in reliably placing the haptics in the ciliary sulcus.

Mechanics of capsulorhexis.

Continuous (central, circular) curvilinear capsulorhexis (CCC), first introduced by Gimbel and Neuhann, has become increasingly popular, especially for endolenticular phacoemulsification with intracapsular intraocular lens implantation. The principles of simple mechanics are used to facilitate teaching the procedure and to reduce the incidence of complications. A safe and simple method of performing CCC based on these principles is described.