Carl-Gustaf Laurell

Comparison of endothelial cell loss and phacoemulsification energy during endocapsular phacoemulsification surgery

Abstract We counted central corneal endothelial cells and measured corneal thickness in 64 human eyes before and three months after cataract extraction and posterior chamber lens implantation. Cataract surgery was the same in all patients and included capsulorhexis and posterior chamber phacoemulsification of the nucleus. Total phacoemulsification energy and time were recorded. A heparin‐surface‐modified intraocular lens or a regular poly(methyl methacrylate) lens, both having the same design and a 5.0 mm optic, was implanted in the capsular bag with the aid of sodium hyaluronate (Healon®). Mean endothelial cell loss was 4%. However, the change in cell density did not correlate with the total phacoemulsification energy used during surgery. Three months after surgery, the central corneal thickness was the same as it had been preoperatively. The results suggest that phacoemulsification in the posterior chamber is a safe procedure even in cases with a hard nucleus.

Inflammatory response in the rabbit after phacoemulsification and intraocular lens implantation using a 5.2 or 11.0 mm incision

Purpose: To study the effect of two incision sizes, 5.2 and 11.0 mm, on the inflammatory response in rabbit eyes after lens extraction with phacoemulsification. Setting: S:t Erik’s Eye Hospital, Stockholm, and Pharmacia, Uppsala, Sweden. Methods: Bilateral endocapsular phacoemulsification was performed on 32 rabbits. The wound was enlarged to 5.2 mm, and a poly(methyl methacrylate) intraocular lens (IOL) was implanted in the capsular bag. In each rabbit, one eye was selected at random and the wound in that eye enlarged to 11.0 mm. In both eyes the wound was sutured with a 9‐0 polypropylene continuous suture. The number of white blood cells (WBCs) and prostaglandin E2 (PGE2) in the aqueous humor were measured at days 1, 3, 7, and 28 postoperatively. Corneal thickness was also measured by pachymetry. Results: The number of WBCs at day 3 and the PGE2 levels at days 1, 3, and 7 were significantly higher in eyes with 11.0 mm incisions than in eyes with 5.2 mm incisions. One week after surgery, the corneas in the eyes with 11.0 mm incisions were significantly thicker than in those with 5.2 mm incisions. Conclusion: The results indicate that incision size is an important factor in the inflammatory response following phacoemulsification and IOL implantation in the rabbit eye.

Posterior capsule opacification after phacoemulsification in patients with postoperative steroidal and nonsteroidal treatment

Purpose: To evaluate the effect of dexamethasone, diclofenac, and a placebo given for 3 weeks after phacoemulsification and intraocular lens (IOL) implantation on the formation of posterior capsule opacification (PCO). Setting: St. Eriks Eye Hospital, Stockholm, Sweden. Methods: In a 2‐year prospective randomized double‐blind study, a laser flare meter was used to measure aqueous flare intensity preoperatively and 3 days, 2 weeks, and 2 years after phacoemulsification and IOL implantation. Posterior capsule opacification was evaluated 2 years postoperatively using retroillumination images taken with a Scheimpflug camera. The Evaluation of Posterior Capsule Opacification system was used to score the areas of PCO density. Results: The median rate of PCO 2 years after phacoemulsification was 0.72 (range 0.32 to 1.57) in the dexamethasone group, 0.78 (range 0.19 to 2.14) in the diclofenac group, and 0.70 (range 0.35 to 1.70) in the placebo group. The differences were not statistically significant (P>.05; Kruskal‐Wallis analysis of variance, multiple comparisons). The rate of neodymium:YAG laser posterior capsulotomy during the 2 years after surgery was not statistically different between groups (P>.05, chi‐square test). There was no correlation (Spearman rank coefficient) between laser flare measurements and PCO formation in any group during the study (P>.05). Conclusion: Topical instillation of diclofenac, dexamethasone, or a placebo in the immediate period after phacoemulsification and IOL implantation did not seem to influence the formation of PCO 2 years after cataract surgery.

Phacoemulsification and lens implantation in rabbit eyes: Capsular bag versus ciliary sulcus implantation and 4.0 versus 7.0 mm capsulorhexis

Purpose: To compare the effects of intraocular lens (IOL) implantation in the capsular bag versus the ciliary sulcus and of a 4.0 versus 7.0 mm continuous curvilinear capsulorhexis (CCC) on postoperative inflammation and after‐cataract formation. Setting: St. Erik’s Eye Hospital, Karolinska Institute, Stockholm, Sweden. Methods: Trial 1 comprised 40 rabbits that had CCC, endocapsular phacoemulsification, and a poly(methyl methacrylate) 10L implanted in the capsular bag in one eye and the ciliary sulcus in the fellow eye. In Trial 2,‐40 rabbits had a 4.0 mm CCC in one eye and a 7.0 mm CCC in the fellow eye followed by phacoemulsification and IOL implantation in the capsular bag. White blood cell (WBC) counts and prostaglandin E2 (PGE2) concentrations in aqueous humor were determined at 1, 3, 7(8), 28, and 56 days postoperatively. Wet mass of the dissected after‐cataract was measured at day 56. In Trial 1, wet mass of the iris‐ciliary body was measured at each observation. Results: In Trial 1, WBC counts at day 1 were higher with a sulcus‐fixated IOL (P = .05). The median wet mass of the dissected after‐cataract was 108.5 mg in eyes with a sulcus‐fixated IOL and 62.5 mg in eyes with a capsule‐fixated IOL (P = .01). In Trial 2, WBC counts at day 8 were significantly higher in eyes with a 7.0 mm CCC than in those with a 4.0 mm CCC (P < .05) There was no significant difference in the amount of after‐cataract. Conclusions: The results indicate that IOL implantation in the capsular bag causes less inflammation and after‐cataract formation than sulcus fixation and that using a large CCC does not affect the total amount of after‐cataract but may enhance the inflammatory response.

Computer-simulated phacoemulsification improvements

A simulator for phacoemulsification cataract extraction is developed. A three-dimensional visual interface and foot pedals for phacoemulsification power, x-y positioning, zoom and focus were established. An algorithm that allows real time visual feedback of the surgical field was developed. Cataract surgery is the most common surgical procedure. The operation requires input from both feet and both hands and provides visual feedback through the operation microscope essentially without tactile feedback. Experience demonstrates that the number of complications for an experienced surgeon learning phacoemulsification, decreases exponentially, reaching close to the asymptote after the first 500 procedures despite initial wet lab training on animal eyes. Simulator training is anticipated to decrease training time, decrease complication rate for the beginner and reduce expensive supervision by a high volume surgeon.

Performance index for virtual reality phacoemulsification surgery

We have developed a virtual reality (VR) simulator for phacoemulsification (phaco) surgery. The current work aimed at developing a performance index that characterizes the performance of an individual trainee. We recorded measurements of 28 response variables during three iterated surgical sessions in 9 subjects naive to cataract surgery and 6 experienced cataract surgeons, separately for the sculpting phase and the evacuation phase of phacoemulsification surgery. We further defined a specific performance index for a specific measurement variable and a total performance index for a specific trainee. The distribution function for the total performance index was relatively evenly distributed both for the sculpting and the evacuation phase indicating that parametric statistics can be used for comparison of total average performance indices for different groups in the future. The current total performance index for an individual considers all measurement variables included with the same weight. It is possible that a future development of the system will indicate that a better characterization of a trainee can be obtained if the various measurements variables are given specific weights. The currently developed total performance index for a trainee is statistically an independent observation of that particular trainee.

Computer-simulated phacoemulsification

Phacoemulsification makes the cataract operation easier for the patient but involves a demanding technique for the surgeon. It is therefore important to increase the quality of surgical training in order to shorten the learning period for the beginner. This should diminish the risks of the patient. We are developing a computer-based simulator for training of phacoemulsification. The simulator is built on a platform that can be used as a basis for several different training simulators. A prototype has been made that has been partly tested by experienced surgeons.

Evaluation of response variables in computer-simulated virtual cataract surgery

We have developed a virtual reality (VR) simulator for phacoemulsification (phaco) surgery. The current work aimed at evaluating the precision in the estimation of response variables identified for measurement of the performance of VR phaco surgery. We identified 31 response variables measuring; the overall procedure, the foot pedal technique, the phacoemulsification technique, erroneous manipulation, and damage to ocular structures. Totally, 8 medical or optometry students with a good knowledge of ocular anatomy and physiology but naive to cataract surgery performed three sessions each of VR Phaco surgery. For measurement, the surgical procedure was divided into a sculpting phase and an evacuation phase. The 31 response variables were measured for each phase in all three sessions. The variance components for individuals and iterations of sessions within individuals were estimated with an analysis of variance assuming a hierarchal model. The consequences of estimated variabilities for sample size requirements were determined. It was found that generally there was more variability for iterated sessions within individuals for measurements of the sculpting phase than for measurements of the evacuation phase. This resulted in larger required sample sizes for detection of difference between independent groups or change within group, for the sculpting phase as compared to for the evacuation phase. It is concluded that several of the identified response variables can be measured with sufficient precision for evaluation of VR phaco surgery.

Virtual reality phacoemulsification: a comparison between skilled surgeons and students naive to cataract surgery

Virtual reality phacoemulsification : A comparison betweeen skilled surgeons and students naive to cataract surgery

Virtual cataract surgery: clinical evaluation

We have developed a simulator for phacoemulsification cataract extraction. In the current project, modules for clinical evaluation were developed. The system was structured into a processing computer and an administrator interface and a trainee interface. The simulation is defined by administrator adjustable parameters and trainee adjustable parameters. The parameters may be categorized as session characteristic parameters, patient characteristic parameters and trainee characteristic parameters. The simulation is measured in variables. Further an air bubble generator was created. We believe that simulator training in future will be required for becoming cataract surgeons.