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abstracts Edited by C. William Silllcoe, M.J).
British Journal of Physiological Optics
Tucker and Rabie (BrJ Physiol Optics 34:12, 1980) investigated the ability of some pseudophakic patients to read both distant and near without a reading addition. One possible explanation lies in the fact that the pupil is often fairly small which would make the depth-of-focus relatively large and might extend considerably the range of clear vision. If the patient is slightly myopic, typically about 1 diopter, and is therefore relatively overcorrected for distance and undercorrected for near, this depth-.of-focus might allow him to see both distant and near without additional correction. This is most likely to occur if the near fixation distance is on the order of 40 - 50 cm rather than 24 - 35 cm. Other possibly significant factors could be any lens shift or a forward shift of the nodal points inherent in the pseudophakic condition.
Bulletin de la Societe BeIge d'Ophtalmologie
Fram.;ois and Verbraeken (Bull Soc Belge Ophtalmol 187:59, 1980) reported a series of 1,000 consecutive intracapsular cataract extractions and found that most important intraoperative complications involved rupture of the capsule (6.5%) and vitreous loss (3%). The most important immediate postoperative complications were delayed wound closure (2.7%), iritis (2.9%) and ocular hypertension (3.4%). Late complications were Irvine-Gass syndrome (2.8%), epithelial down growth in the anterior chamber (0.6%) and retinal detachment (2.0%). Alpha chymotrypsin often caused a temporary ocular hypertension (at least 25.2%). Functional results were very good where no preexisting ocular pathology existed; in 90% of cases the vision was 7/10 or more.
Palestra Oftalmologie Panamericana
Levy et al (Palestra Of tal mol Panamer 4:21, 1980) discussed the importance of having a deep anterior chamber following extraction of the cataract, especially when intraocular lens implantation is to be performed. A deep anterior chamber prevents vitreous loss, makes placement of an intraocular lens easier and helps to protect the endothelium. Their study indicated that the excellent akinesia and patient relaxation produced by general anesthesia resulted in deeper anterior chambers than with local anesthesia and ocular compression. In contradistinction to a commonly held view that ocular rigidity is important with regard to vitreous loss and intraoperative anterior chamber depth, they found no evidence to support
AM INTRA-OCULAR IMPLANT SOC J-VOL. 7, FALL 1981 385
any predictive relationship between these two parameters. It is well known that injection of a local anesthetic increases volume and pressure within the orbit and thereby exerts pressure on the globe. This pressure in an open eye need not be very great to indent the wall of the globe and cause protrusion of the vitreous. Even with use of a balloon compressor on the eye at a periocular pressure of 100 mm Hg for ten minutes prior to surgery, anterior chambers were still shallower than with general anesthesia.
Canadian Journal of Ophthalmology
Cooper and Newfield (Can] Ophthalmol 16:1, 1981) described premarket review of intraocular lenses in Canada. Medical devices in Canada are subject to the Food and Drug Act which is administered by the Health Protection Branch of the Department of National Health and Welfare. There has been considerable cooperation between the Bureau of Medical Devices and the Canadian Ophthalmological Society (COS); the activities of the Bureau have been molded to a large extent by the opinions of COS. A bureau representative has attended meetings of the intraocular and contact lens committee, and many suggestions have been made to the bureau. The bureau's testing program for intraocular lenses is the result of a COS request. Visual inspection of surface finish during manufacture is difficult because of the size of the lens and shallow field of conventional magnifiers and microscopes. A rapid, economical, reliable and nondestructive method of inspection that can be used during manufacture, for complete inspection oflenses has yet to be devised, although promising techniques using laser scattering are being developed in the United States. Lenses were examined in the author's study by projection, optical microscopy and scanning electron microscopy. The latter technique has the advantage of greater depth of field and, because the sample appears opaque, good rendering of surface texture. However, the method is too time-consuming and expensive for a large-scale sampling program and cannot be used in a quality controlled program since the metallic coating required would render the lens unusable for implantation. Lens power is tested on an optical bench. The uncertainty in locating the position for best focus can be greatly reduced by stopping down the lens to exclude the marginal rays, which are brought to a different focus. Lens power in aqueous is then calculated from conversion formulas involving the indices of refraction of the lens and the surrounding medium. Because of the small dimensions involved, lens gauges are impractical for measuring radius of curvature. Commercial instruments such as the radius cope and the toposcope, used for measuring
the radius of contact lenses, could not be used without modifications. However, the radius of curvature of a typical intraocular lens can be measured with fair accuracy by observing the angle of reflection of a laser beam incident on the surface. This technique is similar to the study of Purkinje images of the eye by means of a phakoscope. A spot laser beam is reflected from the lens surface onto a screen. Movement of the lens moves the reflected spot on the screen and the radius of curvature can be calculated from the displacement of the spot as a function of lens position. Because most lens shapes are now fairly standard (plano-convex), the measurement of resolving power is therefore useful as an indication of finished quality rather than good optical design. Also, such figuring defects as cylinder distortion can be detected (though not easily measured) by checking for astigmatism. The apparatus used for measuring focal length (lens power) can also be used for testing resolVing power. A suitable target, such as the United States Air Force 1951 Lens Resolution Target is mounted so that the middle groups on the chart are imaged by the lens as spatial frequencies in the range of 200 to 300 line pairs per mm. The acuity of the retina is typically about 200 line pairs per mm.
Transactions of the Ophthalmological Societies
of the United Kingdom
Galin et al (Trans Ophthalmol Soc UK 100:229, 1980) discussed the mechanism of inflammation after IOL implantation, noting that the additional steps required lead to greater inflammation in the immediate postoperative period than simple cataract extraction. This is further demonstrated by the higher incidence of sterile hypopyon in the implanted eye but late inflammatory syndromes as well as the increased incidence of hypopyon suggest that more than trauma of insertion is involved. PMMA lenses with nylon-6 loops can activate the complement system and such activation occurs primarily at the loops. Mechanical trauma permits protein and cells to enter the eye. Some of these proteins are components of complement, others are also present which can be activated and generate inflammatory mediating substances such as kallikrein and plasminogen activators. The complement components which are in a precursor state are activated by a variety of substances, one of which may be the molecular configuration of the implant or its haptics. White blood cells are then attracted to the site and stimulated to aggregate and adhere to the offending substance. An attempt at phagocytosis occurs and lysosmal enzymes are discharged which can cause destructive effects on the surrounding tissues, including the cornea, vitreous and retina.
386 AM INTRA-OCULAR IMPLANT SOC J-VOL. 7, FALL 1981
Investigative Ophthalmology and Visual Science
Barzam et al (Invest Ophthalmol Vis Sci 19:1348, 1980) compared the intraocular concentrations of oxacillin given by continuous intravenous infusion, subconjunctival injection, or a combination in a rabbit model of Staph aureus endophthalmitis. Both methods produced high levels in the cornea and aqueous and moderate concentrations in the choroid-retina, but vitreous penetration was poor with both. Combined therapy offered little advantage. The optimal therapy of bacterial endophthalmitis may require direct intravitreal injection of antibiotic.
Klinische Monatsblaetter fur Augenheilkunde
Merte and Merkle (Klin Monatsbl Augenheilkd 177:437, 1980) tested the long term lOP-lowering effect of the beta-blocker Propranolol 0.5% drops over six years on 27 patients. These included angle-closure (8), open-angle glaucoma (14), congenital glaucoma (2), pigmentary glaucoma (2), and aphakic glaucoma (1). Propranolol decreased lOP without causing miosis, accommodative spasm or other irritating side effects. In seven patients, however, pressure was not lowered sufficiently with each treatment. During the examination period the pulse rate was slowed and blood pressure reduced to a relatively minor extent which did not seriously affect circulation.
Clemente (Klin Monatsbl Augenheilkd 177:455, 1980) described goniotrapenation with a triangular scleral flap. The size of the usual 20 mm2 flap was reduced by about one-half. Instead of the quadrangular flap, a lamellar triangular flap of 5 mm side length was prepared. The reduction of the flap and accordingly the scleral wound did not lead to any disadvantages. Advantages were a significant shortening of the filtration path with less scarring tendency and a simpler way of preparing the flap. Also, in the combination of cataract and glaucoma operations the triangular flap was found to be useful.
Demmler (Klin Monatsbl Augenheilkd 177:523, 1980) studied the effect of Bupranolol eye drops on ten patients with open-angle glaucoma over six months. Bupranolol eye drops lowered lOP by about 15% over a prolonged period. Some patients needed treatment in .combination with miotics. Visual acuity and visual fields remained constant. As a rule, Bupranolol was tolerated well by the patients.
American Journal of Ophthalmology
Berger and Streeten (Am] Ophthalmol 91:630, 1981) reported two cases of fungal growth in aphakic hydrophilic contact lenses, and discussed other series, some of which had as high as 14% positive cultures for fungi after home sterilization. Both cases, and one previously reported, occurred with thicker aphakic contact lenses. Both patients had symptoms that cleared up rapidly after they discontinued wearing the contact lenses, but in neither case was there any evidence of fungal infection of the eye. This confirms the surprisingly small effect a continuous fungal inoculum has on the eye. Fungi often seem to be in the matrix of the contact lens and not on its surface, which offers the eye a margin of safety. In both cases, however, surface fungi were present so that the possibility of infection after abrasion was real. No conclusion can be drawn regarding the susceptibility of soft contact lenses to specific fungi as several different fungi have been found. Evidence suggests that thicker contact lenses are more susceptible to fungal growth, especially when they are used for extended wear.
Eiferman (Am] Ophthalmol 92:328, 1981) studied the effect air has on human corneal endothelium by filling the anterior chamber completely with air during cataract extraction. This produced an average loss of 18.5% endothelial cells compared to 8.5% in a control group. The same surgeon did the identical procedure, except for the air injection, in all cases. A pseudoguttata or "peau d' orange" appearance of the corneal endothelium was seen with air but disappeared with resorption of the bubble.
Berkowitz et al (Am] Ophthalmol92:332, 1981) did fluorophotometric determination of the corneal epithelial barrier after penetrating keratoplasty and found that healed corneal transplants showed a permeability 3.3 times that of normal eyes that had not undergone surgery. Partially healed corneal transplants were 67 times more permeable than control eyes and 20 times more than the healed transplants. This increase in permeability could result in intraocular damage from topically applied medications. Topical corticosteroids can induce posterior subcapsular cataracts and glaucoma in susceptible people. Topical antibiotics are well tolerated in an eye with an intact epithelium, but could cause endothelial cell toxicity in an unhealed cornea. On the other hand, it could be worthwhile to lower required concentration of topical anti glaucoma eye drops in patients with epithelial defects. This could decrease systemic and ocular side effects while remaining as effective therapeutically. Cardiac side effects with epinephrine and timolol could be increased in susceptible people.
AM INTRA-OCULAR IMPLANT SOC J-VOL. 7, FALL 1981 387
Krey (Am J Ophthalmol 92:378, 1981) found aberrations of polarized light at the fixation points of the posterior loops as well as in the optical portion itself and in the haptic loops of six styles of IOLs from four manufacturers . These represented changes of orientation in the molecular arrangement at locations subjected to mechanical stress. Small cracks at the loop fixation points in lenses implanted in two patients confirmed these polarized light findings .
Cobo and Forster (Am J Ophthalmol 92:59, 1981) observed that understanding of the dynamics of intravitreal gentamicin, as well as other antibiotics, has been based on data from studies in phakic, un inflamed rabbit eyes. This could be misleading as the establishment of a communication between the vitreous and the anterior chamber might cause more rapid clearance of the antibiotic from the vitreous into the aqueous circulation . This study showed that intravitreal gentamicin cleared more rapidly from the uninflamed aphakic rabbit eye (12 hour half-life) than the phakic control (32 hour half-life). A similar difference was noted with experimental Staph aureus endophthalmitis. Presumably, removal of the lens allows faster diffusion into the anterior chamber where such drugs may be more rapidly cleared through the aqueous circulation. Human data from nine aphakic infected eyes undergoing reinjection or vitrectomy indicated that therapeutic levels of gentamicin are not consistantly found 48 hours or more after the initial intravitreal injection. An optimal time for reinjection may be between 36 and 48 hours. Since clearance is slower in phakic eyes, it may be reasonable to postpone reinjection for 72 to 96 hours .
Ophthalmology Rao et al (Ophthalmol 88:386, 1981) studied long
term changes in corneal endothelium following intraocular lens implantation. They compared 52 eyes with intraocular lenses and 35 eyes with simple cataract extractions using clinical specular microscopy. The endothelial photographs were obtained preoperatively, and at least four times in the postoperative period of each case, ranging from 16 to 43 months. The implanted cases produced more endothelial cell damage and the deleterious effect was greatest with irissupported lenses as compared with anterior chamber lenses. Seventy-one percent had precipitates on the endothelium with 16% developing guttata-like areas. All changes progressed with time and none occurred in eyes with simple cataract extraction. The progressive damage may be a result of chronic, smoldering uveitis associated with intraocular implants. (Ed. note: all cases reported had intracapsular cataract extraction. A comparison with extracapsular extraction/capsule-supported IOLs would have been interesting).
Knolle (OphthalmoI88:407 , 1981) described a modification of McCannel's suturing technique for dislocated IOLs wherein the initiallimbal corneal incision for passage of the suture needle was omitted. Instead, needle entry through the cornea and iris and then around the lens loop, and exiting through the cornea were performed first. The incision for suture retrieval was performed later. This avoided chamber shallowing the endothelial injury, as confirmed by endothelial cell counts .
Wilkinson (Ophthalmol 88:410, 1981) reviewed 70 pseudophakic retinal detachments and found that they were similar in characteristics to those following routine cataract extraction, but were somewhat more difficult to manage than the phakic variety, primarily because of difficulty in visualizing the peripheral retina. Also, there was some mild tendency for periretinal membrane formation in pseudophakic cases. Despite these problems, the repair rate closely approximated that for aphakic eyes. Visual results in pseudophakic eyes were somewhat lower than in comparable aphakic eyes . The presence of an IOL makes placement of intraocular gases at the time of vitrectomy for massive preretinal proliferation (MPP) much more difficult. Profound scleral indentation at the time of surgery is frequently necessary to bring the peripheral retina of the pseudophakic eye into view. More cryotherapy and more extensive buckles are frequently required in pseudophakic eyes than in aphakic cases.
Mackool (Ophthalmol 88:414, 1981) described the use of closed vitrectomy techniques on pseudophakic eyes to remove retropseudophakic membranes, to remove vitreous strands that surrounded IOLs or that were adherent to the corneoscleral incision and iris in cases with persistent cystoid macular edema, to relocate IOLs which were dislocated into vitreous, and to relieve pseudophakic pupillary block. These techniques were also performed to remove vitreous in the anterior chamber prior to secondary IOL implantation. Closed vitrectomy was effective in improving visual acuity and reducing or eliminating CME in the five pseudophakic eyes. However, no patient achieved a final visual acuity of more than 20/40. Corneal edema did not occur when closed vitrectomy was performed prior to IOL insertion. This is in contrast to cases of "open-sky" approach in which superior corneal edema for one to three weeks following surgery was almost invariably present.
Polack et al (OphthalmoI88:425, 1981) used sodium hyaluronate (Healon) to restore the anterior chamber and replace vitreous following anterior vitrectomy in 30 penetrating keratoplasties. Balanced saline solution was used as control in 20 keratoplasties. It was
388 AM INTRA-OC ULAR IMPLANT SOC J-VOL. 7, FALL 1981
found that the Healon facilitated surgery in aphakic eyes and reduced the degree of endothelial trauma by decreasing the amount of manipulation of the graft when it is being sutured. Similar graft protection was observed in phakic eyes and in cases of combined graft with cataract surgery and 10L implantation. Corneal transplants were significantly thinner in the Healontreated eyes than in the control eyes . The authors felt that corneal thickness measurements are the best indicator of endothelial function and these measurements are probably more important than cell count which at best samples a very small portion of the corneal tissue. In 33 Healon-treated eyes, lOP was increased in only two cases (40 mm Hg). These were early cases in which 0.5 ml or more was injected and since then they have removed Healon and exchanged BSS through a 27-gauge needle.
Hoffer et al (OphthalmoI88:729, 1981) reported results of the UCLA clinical trial of radial keratotomy. Patients excluded were those under the age of 18, those with myopia less than 2 diopters or progressive myopia, those with astigmatism over 4 diopters, and those with a history of any eye disease other than mild amblyopia. Data was collected on 52 eyes of the first 43 patients three months after surgery. No patients were excluded or lost to follow-up. All had preoperative, uncorrected visual acuity less than 20/200; postoperative uncorrected acuity was 20/20 or better in 25% and 20/40 or better in 52%. Twentyseven percent had uncorrected acuity between 20/50 and 20/100. Best-corrected acuity decreased in 20% but the maximum decrease in any eye was one line of Snellen letters. Preoperative mean refractive error was - 4.9 diopters and postoperatively, the mean decrease ill myopia was 3.4 diopters. Postoperatively, 25% had hyperopia of + 0.25 to + 3.25 diopters but all could accommodate to 20/20 without glasses. Decrease in myopia achieved did not correlate with steepness of corneal curvature, corneal diameter, or scleral rigidity. Significant glare was present in 20% and annoying variable visual acuity in 10%.
Perl et al (Ophthalmol 88:774, 1981) studied 180 consecutive corneal transplants performed by one surgeon to determine the benefit obtained by using a 0 .5 mm oversize (OS) graft. Same size (SS) grafts were compared to OS grafts. Refractive error, recovery of visual acuity, and lOP were similar, but astigmatism was found to be significantly greater in the OS group. OS grafts did not protect against postkeratoplasty glaucoma or decrease recovery time.
Kramer (Ophthalmol 88:782, 1981) studied cystoid
macular edema after aphakic penetrating keratoplasty and found that transpupillary anterior vitrectomy at the time of penetrating keratoplasty, as compared with no vitreous manipulation, seemed to contribute to a high incidence of postoperative persistent CME. Whenever possible the vitreous should remain undisturbed during CPKP. Appropriate surgical measures include: use of a scleral support firmly sutured to the sclera; preoperative or intraoperative administration of carbonic anhydrase inhibitors and/or osmotic diuretics; digital massage after completion of a trephine groove but before entrying the anterior chamber; the use of an oversize donor corneal button, and constant care to maintain the anterior chamber throughout surgical manipulations. In addition, non pupillary routes for excision of vitreous should be considered when vitreous excision is made unavoidable by vitreous prolapse or anticipated prolapse. These include aspiration of fluid vitreous through the pars plana and/or pars plana vitrectomy with a vitreous cutting instrument before or after extraction. Finally, extracapsular cataract extraction in CPKP may help by maintaining an intact posterior capsular boundary while protecting the anterior vitreous face .
Abbott (Ophthalmol 88:788, 1981) studied patients with unilateral corneal edema and clinically normal fellow eyes, with specular microscopy. Clinically unrecognized endothelial disease was proposed as a cause for this unilateral corneal edema and was verified by light and electron microscopic studies. The pathologic findings varied somewhat from Fuch's dystrophy and may represent either a variant or a form of endothelial cell degeneration of as yet undetermined etiology. The fellow eyes had endothelial pleomorphism and reduced counts in the nonedematous cornea, and no history of previous eye disease, trauma, inflammation or surgery. These conditions were not detectable in the nonedematous cornea by standard high magnification biomicroscopy and required the clinical specular microscope to confirm the diagnosis.
Foulks (Ophthalmol 88:801, 1981) described treatment of recurrent corneal erosion and corneal edema with topical osmotic colloidal solution. These were well tolerated and effective in treating corneal erosion but did not reduce symptoms or improve vision in cases of corneal edema due to endothelial decompensation. This suggests that the solutions have a significant dehydrating effect when edema results solely from epithelial abnormalities .
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