Ehud I. Assia

Temporal parameters of low energy laser irradiation for optimal delay of post-traumatic degeneration of rat optic nerve

Compression injury of a central nerve results in its degeneration with irreversible loss of function due to the inability of the mammalian central nervous system (CNS) to regenerate. In contrast, the CNS of lower vertebrates has a high capacity to regenerate. Recently, low energy laser irradiation was shown to attenuate degeneration in injured CNS nerves. The optic nerves of rats were subjected to moderate crush, calibrated so that some electrophysiological activity was preserved. The nerves were then subjected to low energy laser irradiation (10.5 mW, 2 min daily) for various periods. The electrical activity of the nerves, distal to the site of injury, was determined by measuring the compound action potential at the termination of the experiment. Two weeks of irradiation begun immediately after injury and continued daily thereafter, resulted in a compound action potential which was significantly higher (mean +/- S.E.M. 1856 +/- 535 microV) than that of non-irradiated injured nerves (351 +/- 120 microV). The effect was temporary and subsided within a week. This two-week irradiation was slightly more effective than a treatment lasting one week (1406 +/- 225 microV) and was significantly more effective than 4 days of irradiation (960 +/- 133 microV). The number of treatments is therefore important. The time at which the treatment commences relative to the injury is also critical. Irradiation initiated two hours after the crush was about half as effective as immediate irradiation (810 +/- 42 microV). No apparent effect was evident when the laser was applied for the first time 5 h, or longer, after the crush.(ABSTRACT TRUNCATED AT 250 WORDS)

Removal of viscoelastic materials after experimental cataract surgery in vitro

ABSTRACT The one significant complication of viscoelastic materials is that they may cause postoperative intraocular pressure rise. We investigated the rate and ease of removal of various viscoelastics using the Miyake video technique. Five viscoelastics were investigated: sodium hyaluronate (Healon®), Healon GV®, chondroitin sulfate‐sodium hyaluronate (Viscoat®), hydroxypropylmethylcellulose (Occucoat®), and polyacrylamide (Orcolon®). The viscoelastics were dyed with fluorescein and, after filling the capsular bag with a viscoelastic material, a posterior chamber intraocular lens (IOL) was implanted. The viscoelastic was then aspirated using an automated irrigation/aspiration device. Healon and Healon GV were completely removed within 20 to 25 seconds. Viscoat adhered to the lens capsule and to the posterior surface of the IOL and cooplete removal required approximately 3.5 minutes. Most Occucoat and Orcolon was aspirated within one minute; however, removal was completed only after three minutes. Removal of Healon and Healon GV was faster and more complete than removal of the other viscoelastics. Whether a small amount of viscoelastic left in the eye or trapped behind the IOL optic has any clinical significance has to be studied.

Inhibition of posterior capsule opacification: The effect of colchicine in a sustained drug delivery system

ABSTRACT We investigated the effect of colchicine in a sustained drug delivery system on posterior capsule opacification (PCO) in rabbit eyes. A polymer matrix wafer, which diffused colchicine at a steady rate, was implanted in the capsular bag of 34 eyes after the lens material was removed by endocapsular phacoemulsification. Three different drug concentrations were used in the rabbit eyes, which were compared with control eyes containing the polymer matrix wafer without colchicine. The mean PCO score was highest in the control group without colchicine and increased steadily over 12 weeks. The rate of PCO formation in all eyes treated with colchicine was significantly lower than in the control group. There was no statistically significant improvement in PCO inhibition with the higher colchicine dosages. Side effects included inflammatory anterior chamber reaction and corneal and retinal complications and were most notable with the highest drug concentration. Slow release of colchicine reduces PCO formation in the rabbit. The optimal biocompatible dosage must be carefully determined and warrants further investigation.

The Elastic Properties of the Lens Capsule in Capsulorhexis

We investigated the ability of the anterior lens capsule to stretch and allow removal of lens substance and intraocular lens implantation through a continuous circular capsulorhexis. Capsulorhexis of various sizes (2.5 to 7.5 mm) were performed in 50 eyes obtained post mortem from 31 patients. The nucleus and cortex were removed by either phacoemulsification (35 eyes) or manual extracapsular cataract extraction (15 eyes). The opening of the capsule was then gradually enlarged, using a modified caliper with two pins attached to its tips, until the margins were torn. The capsule was torn when the circumference at the time of rupture was 1.6 times larger than the circumference of the original circular capsulectomy or 5.0 times larger than the diameter of the capsulectomy. Manual extraction of a lens nucleus with profile circumference (sagittal or anteroposterior) of 18.0 to 22.0 mm can be performed through a 5.5-mm opening and a 6.0- to 7.0-mm optic intraocular lens (profile circumference of 13.0 to 17.0 mm) can be implanted through a 4.5-mm capsulectomy.

Topical anesthesia using lidocaine gel for cataract surgery.

PURPOSE To assess the safety and efficacy of topical anesthesia using lidocaine gel in cataract surgery. SETTING Department of Ophthalmology, Meir Hospital, Sapir Medical Center, Kfar-Saba, Israel. METHODS One hundred cataract procedures (48 manual extracapsular cataract extraction [ECCE] and 52 phacoemulsification) were performed using lidocaine 2% gel as the sole anesthetic agent. The gel was applied 3 to 5 times prior to surgery. Intraoperative and postoperative data were recorded, and patients were asked to grade the pain on a scale of 0 (no pain) to 10 (unbearable pain). RESULTS Sixty-two percent of patients having manual ECCE and 74% having phacoemulsification reported no pain during surgery (score 0). The mean pain score in the manual ECCE group was 0.99 +/- 1.64 (SD); 3 patients required an additional intracameral lidocaine injection. The mean score in the phacoemulsification group was 0.72 +/- 1.47; no patient required additional anesthesia. CONCLUSIONS Topical application using lidocaine 2% gel is safe and highly effective, especially in clear corneal phacoemulsification. The gel also provides prolonged lubrication, further facilitating surgery.

MECHANISM OF RADIAL TEAR FORMATION AND EXTENSION AFTER ANTERIOR CAPSULECTOMY

The mechanisms of anterior capsular radial tear formation and extension around the equator onto the posterior capsule were investigated in 57 eyes obtained postmortem. Experimental radial tears were created by gradual opening of a caliper. In 95% of cases, the tear immediately reached the equator but none extended to the posterior capsule. The elastic forces of the zonules attached to or crossing the edges of the tear resisted a widening of the gap between the edges and thus limited the radial progression of the rupture. A significantly stronger force and severing of the zonules were necessary for a tear to extend around the equator. The authors have determined that radial tears in the anterior capsule seldom extend around the equator, providing the zonules bridging the tear are intact. There is a diminution of the tearing force when the flaps are widely open. Careful surgery with preservation of the integrity of the capsular-zonular apparatus is a major factor in preventing major complications such as posterior capsular ruptures.

Management of Descemet's membrane detachment

Abstract Detachment of Descemet’s membrane is a rare but serious complication of cataract surgery. Most surgeons attempt to reposition the membrane by injecting air, slow‐reabsorbing gases, or viscoelastic substances into the anterior chamber. We describe five cases of subtotal detachment without rolled scroll. These cases recovered spontaneously after two to three months. We believe that conservative treatment in such cases is indicated and has a good a chance of favorable outcome.

Small-incision manual extracapsular cataract extraction using selective hydrodissection.

Hydrodissection is a technique in which balanced salt solution is injected through a cannula into various layers of a cataractous lens to separate the lens lamella in a nonspecific location. Selective hydrodissection allows separation of the lens lamella at different desired anatomical layers. The technique allows the smallest possible nucleus, ie, the hard-core nucleus, to be hydroexpressed as a separate entity, requiring, correspondingly, a relatively small capsulorhexis and limbal incision. Then, in a second maneuver, the epinucleus, which engulfs the hardcore nucleus to form the adult nucleus, also can be aspirated or hydroexpressed as a whole. Selective hydrodissection permits scleral incision and stitchless surgery in planned extracapsular cataract extraction and also may serve as an intermediate step for surgeons who wish to convert to or learn phacoemulsification techniques.

Clinicopathologic Study of the Effect of Radial Tears and Loop Fixation on Intraocular Lens Decentration

PURPOSE The purpose of this study is to determine the effect of loop fixation and anterior capsular tears on intraocular lens (IOL) decentration. METHODS A retrospective measurement of IOL decentration was performed on 144 human eyes with posterior chamber (PC) IOLs obtained after death. RESULTS Decentration in eyes with asymmetrical bag-sulcus fixation (mean +/- standard deviation, 0.64 +/- 0.39 mm) was significantly higher than eyes with symmetrical fixation. In the presence of radial tears, symmetrically fixated IOLs in either the capsular bag or the ciliary sulcus decentered to a similar degree, 0.35 +/- 0.25 mm and 0.4 +/- 0.26 mm, respectively. The least decentration was observed with capsular fixation and no radial tears (0.18 +/- 0.09 mm). This was significantly less decentration than with any other form of fixation in the presence of radial tears. CONCLUSION This study shows that capsular fixation with no radial tears, as can be achieved by using the continuous curvilinear capsulorhexis, is associated with the least decentration.

Effect of aspirin intake on bleeding during cataract surgery

Purpose: To study the association between chronic intake of aspirin and intraoperative bleeding during cataract surgery and the effect of discontinuing the medication before surgery. Setting: Department of Ophthalmology, Meir Hospital, Sapir Medical Center, KfarSaba, Israel. Methods: Sixty‐one patients having cataract surgery and receiving aspirin to prevent thromboembolic events were divided into 3 groups: Group A, continuation of the medication; Group B, cessation of aspirin intake for 2 to 5 days before surgery; Group C, cessation of medication for 7 to 10 days before surgery. Blood tests of coagulation parameters, a detailed questionnaire, and 1 day and 1 week follow‐up were evaluated. Results: There were no significant differences in blood tests and the amount and incidence of intraoperative bleeding among the 3 groups. Diathermy was used somewhat more in Group A; however, there was no difficulty stopping the bleeding in any case and discontinuation of the medication had no effect on the intraoperative course or postoperative outcome. Conclusions: Aspirin intake was not associated with significant intraoperative bleeding; thus, discontinuation of aspirin is usually not indicated. Clear corneal phacoemulsification is advantageous in patients receiving antiplatelet therapy.