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May 31, 2002
Sonic phacoemulsification
J Cataract Refract Surg June 2002;28:1054-1060
| The coiled SuperVac tubing limits surge flow resulting from occlusion breakage in a dynamic way. |
The Staar Wave also allows improved stability of the anterior chamber with coiled SuperVac tubing, which increases vacuum capability up to 650 mm Hg (Figure). The key to chamber maintenance is a positive fluid balance between infusion flow and aspiration flow. When occlusion is broken, vacuum previously built in the aspiration line generates a high aspiration flow that can be higher than the infusion flow. This results in anterior chamber instability. The coiled SuperVac tubing limits surge flow resulting from occlusion breakage in a dynamic way. The continuous change in direction of flow through the coiled tubing increases resistance through the tubing at high flow rates such as on clearance of occlusion of the tip. This effect only takes place at high flow rates (greater than 50 cc/min). The fluid resistance of the SuperVac tubing increases as a function of flow, and unoccluded flow is not restricted.
Posted by dastjerdi at 01:10 AM
May 28, 2002
Close-up microkeratome blades reveal variation
Eurotimes May 2002
A close-up look at a number of different disposable microkeratome blades using electron microscopy revealed considerable variation in size and cutting edge between both different manufacturers and among blades made by the same manufacturer. Researchers examined ten different microkeratome blade types, comparing five blades of each type. They studied scanning electron microscopic images up to a magnification of 700x the original size and measured blade length, width, and cutting edge. The researchers also examined the blades for any irregularities. The researchers looked at blades manufactured by Bausch & Lomb, Nidek, Moria, Allergan, Oasis, Schwind, Beaver, Alcon, and Asclepion-Meditec. They found variations between the ten different blade groups and among the five blades within each microkeratome blade group. The differences noted included length, width and cutting edge. They expressed concern about the diversity of size and cutting edge seen in blades created by different manufacturers for the same microkeratome, which could potentially compromise the procedure's precision. The blades studied also revealed different degrees of impurities and surface smoothness. These were readily visible at a magnification of 175x. Some blades were coated with impurities or showed deposits. The cutting edge of a particular blade was left relatively unsharpened by some manufacturers. Other blades revealed an additional cutting edge, while the same blade made by another manufacturer lacked it. They noted that some blades were fine, revealing no irregularities along the length of the cutting edge, no impurities or deposits on the blade surface and no variations in size. Such smoothness and consistentency were particularly evident with Amadeus (Allergan) microkeratome blades.
Posted by dastjerdi at 01:11 AM
Tecnis IOL; the IOL that has been designed to counteracts higher-order aberrations
The Tecnis IOL (Pharmacia Corp.), to be launched at this year’s American Society of Cataract and Refractive Surgery symposium, has FDA approval. This is the first foldable IOL that counteracts the spherical aberration of the cornea. It has been designed to take into account higher-order aberrations, in particular the spherical aberration of the cornea. The Tecnis IOL more closely resembles the youthful crystalline lens and compensates for the spherical aberration of the cornea, decreasing total optical aberration. While this may have some benefit for Snellen visual acuity, the real benefit is in terms of contrast sensitivity.
Posted by dastjerdi at 12:41 AM
Cold Phacoemulsification
Several new phacoemulsification systems can perform cold phacoemulsification. The Dodick Photolysis System is available and the Asclepion-Meditec Phacolase and the Paradigm Photon Laser are under investigation. These three systems use a laser to destroy nuclear material. They’ve all shown themselves to be safe and effective, but only for relatively soft nuclei.
Another available cold phaco system is the STAAR Sonic Wave. The tip vibrates in sonic rather than ultrasonic frequencies, so there is no frictional force in the tip creating thermal energy. It is capable of addressing all grades of nuclei, although it is less efficient for harder grades.
The Alcon Aqualase is another non-ultrasound system. Still in the investigational stage, this system uses pulsed warm balanced salt solution.
Modifications have also been made to existing systems to allow them to use cold phaco. White Star technology on the Allergan Sovereign uses short pulses or bursts of phaco energy.
The Alcon Legacy has also made some improvements with NeoSonix and AdvanTec software. AdvanTec software is totally digitized. It makes for more efficient cutting and more efficient fluidics. The Neosonix technology dramatically enhances efficiency in phaco.
Posted by dastjerdi at 12:10 AM
May 23, 2002
Hyperopic LASIK on ocular alignment and stereopsis in patients with accommodative ET
Ophthalmology June 2002; 109 (6): 1148-1153
Treatment of accommodative esotropia (AET) has traditionally consisted of full optical correction of hyperopia using glasses or contact lenses. Eye muscle surgery is performed for residual esotropia. In this study the effects of refractive surgery on ocular alignment and stereopsis in patients with hyperopia and esodeviation were evaluated.
| Theoretically, any means of reducing hyperopia should relax accommodation and thus decrease accommodative convergence and accommodative strabismus. |
Twenty seven patients (mean age, 33.3 years; range, 10-52 years) with comitant esophoria or esotropia and hyperopia underwent bilateral LASIK for correction of refractive error. Mean preoperative cycloplegic refraction was +7.28 D for right eyes and +7.44 D for left eyes. Mean postoperative refraction obtained a minimum of 6 months after surgery was +2.17 D for right eyes and +2.10 D for left eyes.
| Hyperopia and AET should be considered relatively permanent conditions in the adult and older child, and surgical correction of hyperopia may be reasonable in an attempt to reduce dependence on glasses and contact lenses. |
In conclusion, LASIK was relatively safe and effective in reducing the esodeviation in AET, but at this time we are unable to identify presurgically those patients who are most likely to benefit from the procedure.
Posted by dastjerdi at 05:47 AM
May 22, 2002
Enzymatic Sclerostomy
Arch Ophthalmol May 2002;120:548-553
The potential of collagenase to act as a "biological knife" to selectively digest collagen inspired researchers to develop a treatment modality for glaucoma "enzymatic sclerostomy". For this purpose, highly purified collagenase (nucleolysine) is used to create deep focal scleral digestion, possibly enabling micropercolation of aqueous humor.
Enzymatic sclerostomy was performed in 15 blind symptomatic eyes of 15 patients with primary open-angle glaucoma under topical or peribulbar anesthesia. A specially designed polymethylmethacrylate enzyme applicator filled with a mean of 123 µg of collagenase was introduced through a 5-mm peritomy, and affixed to the limbus by means of cyanoacrylate tissue glue. After 22 to 24 hours, the applicators were removed and the patients were followed up for 1 year.
| By causing an overall decrease of 43.0% in the IOP immediately after treatment and a sustained lowering effect of 20.0% at 1 year without antiglaucoma medication, enzymatic sclerostomy has demonstrated its potential as a treatment for open-angle glaucoma. |
| Patients were equally comfortable under topical anesthesia or with peribulbar block, suggesting that enzymatic sclerostomy could be performed as an office procedure. |
Controlled thinning of the treated sclera associated with aqueous percolation and shallow filtration bleb was seen in all eyes in the immediate postoperative period. The mean IOP decreased from 43.5 mm Hg (with antiglaucoma medications) preoperatively to 24.8 mm Hg (a 43.0% decrease from baseline with no antiglaucoma medication) on the first postoperative day and to 34.8 mm Hg (a 20.0% decrease from baseline with no antiglaucoma medication) at the end of 1 year. Sustained lowering of the IOP was achieved despite the absence of a detectable filtering bleb in most eyes beyond 1 month and in all eyes beyond 3 months. It is possible that enzymatically induced alterations in the walls of Schlemm canal and the trabecular architecture, could contribute to the IOP–lowering effect. Ophthalmic adverse effects were limited to the treated area and included immediate postoperative transient conjunctival reaction ranging from mild chemosis to conjunctival maceration. No systemic complications were noted. None of the patients reported pain or discomfort during and after the procedure.
In summary, enzymatic sclerostomy has demonstrated its potential as a relatively simple surgical treatment for glaucoma. It demonstrated immediate and sustained IOP reduction and provided symptomatic relief in blind eyes with primary open-angle glaucoma. The procedure, however, needs further technical refinement.
Posted by dastjerdi at 07:24 AM
May 20, 2002
Acute Psychosis Following the Use of Topical Ciprofloxacin
Arch Ophthalmol 2002 May;120(5):669-70
A healthy 27-year-old woman came to the emergency eye clinic with a 3-day history of bilateral reddened eyes associated with ecchymosis and swelling of the eyelids. The patient had no history of any systemic complaints, was taking no medication for therapeutic or recreational use, did not have alcoholism, and did not smoke. Conjunctival swabs were taken and sent for microbial isolation and sensitivity assays and the patient was prescribed ciprofloxacin eye drops, 1 drop hourly, in each eye. About a half hour after the third dose, the patient complained of dizziness and light-headedness. Following this, family members noted a distinct change in the behavior of the patient, who began to have well-defined visual hallucinations, ill-defined auditory hallucinations, and irrational conversation. The next day, the patient was seen in the emergency eye department with increasing behavioral problems. The patient was deemed to have had an acute psychotic reaction secondary to topical ciprofloxacin. The patient was advised to stop using ciprofloxacin eye drops (nearly 24 hours after initiation of treatment) and began taking teicoplanin (1%) eye drops. Within about 12 hours of changing the treatment, the patient and family members noted an improvement in behavior and within a further 12 to 14 hours, the hallucinations and behavioral disturbances disappeared completely. The patient was later able to describe her visual and auditory hallucinations in detail. The conjunctivitis responded completely to the teicoplanin regimen.
Ciprofloxacin hydrochloride is a fluoroquinolone antimicrobial frequently used in both ophthalmic and general medical practice. Whereas adverse effects of this drug are not uncommon following its systemic use, they are uncommon following its topical use. Central nervous system adverse effects, such as dizziness and lightheadedness, acute psychosis, and other neuropsychiatric disorders, have been described following its systemic use. Whereas psychotic reactions are well known after the use of atropine and cyclopentolate eye drops, this is the first reported case of such a reaction after the use of ciprofloxacin eye drops. Therefore, the possibility of such an adverse effect should always be kept in mind in patients using these drops, particularly in young women, who seem to be especially sensitive to these effects.
Posted by dastjerdi at 06:48 PM
May 17, 2002
Conjunctiva most likely source of organisms in endophthalmitis
J Cataract Refract Surg 2002 May;28(5):826-33
This study shows that an extremely low bacterial contamination rate of the anterior chamber can be achieved after cataract extraction using phacoemulsification with IOL implantation. Additional findings support the conjunctiva as being the primary source of bacteria causing postoperative endophthalmitis and the ability of povidone-iodine to reduce the conjunctival bacterial load.
Povidone-iodine solution has broad antibiotic activity and has been shown to significantly decrease conjunctival and perilimbal flora. More important, povidone-iodine decreases the incidence of culture-positive postoperative endophthalmitis. The most common bacteria isolated from the conjunctiva were corynebacteria, followed by coagulase-negative staphylococci, the most common cause of infectious endophthalmitis, and Propionibacterium acnes. Corynebacteria, previously regarded as nonpathogenic, have more recently emerged as important causes of ocular disease, including being implicated in cases of endophthalmitis after cataract surgery. In this study, the number of eyes yielding coagulase-negative staphylococci, corynebacteria, and P acnes decreased from 65% preoperatively to 16% postperatively most likely the result of the action of the povidone-iodine. This study was consistent with the previous finding that povidone-iodine is particularly effective in reducing Propionibacterium acnes. Although P acnes was cultured from the conjunctiva in 20 patients before preparation for surgery with povidone-iodine, only 1 patient's conjunctiva remained culture positive postoperatively. This is of interest as P acnes has increasingly become recognized as a pathogen responsible for more chronic forms of postoperative endophthalmitis.
Posted by dastjerdi at 10:46 PM
Treatment of Painful Bullous Keratopathy with PTK
Br J Ophthalmol August 2001;85:912-915
PTK can be a useful therapeutic measure in painful bullous keratopathy with poor visual potential. Deep PTK (8 mm central zone with a 1 mm blend zone and 25% stromal depth ablation) appears to be more successful in pain management than superficial treatment. The deeper treatment is thought to ablate the main sensory plexus in the stroma. The preterminal neural plexus of the cornea is located just deep to Bowman's membrane. It was hypothesised that a moderately deep ablation may have a superior effect on decreasing pain by the ablation of this neural plexus. It may also decrease swelling of the corneal stroma by decreasing the quantity of mucopolysaccharide and hence osmotic load. The increased scarring associated with a deeper ablation may also result in increased stability of the epithelium. This procedure is relatively inexpensive and quick, and it provides another alternative for patients to PKP.
Posted by dastjerdi at 07:56 AM
Association Between Sleep Apnea Syndrome and Nonarteritic Anterior Ischemic Optic Neuropathy
Arch Ophthalmol May 2002;120:601-605
The pathophysiologic characteristics of Nonarteritic anterior ischemic optic neuropathy (NAION) remains unclear. Risk factors include aging, a small optic nerve head, and microvascular changes associated with diabetes and systemic hypertension. No treatment is available since neither steroids nor surgical optic nerve sheath fenestration has proved to be effective. Prevention with aspirin has not been demonstrated to be effective, although it is recommended.
| SAS is now recognized as an important risk factor for cardiovascular and neurovascular diseases. |
| Approximately 75% of all patients with NAION discover visual loss on first awakening in the morning. This might indicate that SAS could play an important role in the pathogenesis of NAION. |
This study showed that 71% of patients with NAION had SAS. The prevalences were significantly higher than in age- and sex-matched controls (24%). It was hypothesize that SAS may cause NAION in some cases, the damage may result from impaired optic nerve head blood flow autoregulation, secondary to repetitive prolonged apneas. Since there is no proven treatment of NAION, further studies are needed to clarify whether repetitive nocturnal upper airway obstructions might directly damage the optic nerve, whether continuous positive airway pressure treatment might help affected patients recover from NAION, and whether long-term treatment might help prevent involvement of the second eye.
Posted by dastjerdi at 01:53 AM
May 16, 2002
Accommodative IOLs
Review of Ophthalmology Vol. No: 9:04 Issue: 4/15/02
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| The CrystaLens flexes at the junctions between the optic and the haptics, allowing it to move forward during accommodative effort. |
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Contraction of the ciliary body may cause vaulting of the IOL, either by direct action or by displacing the vitreous body anteriorly. The forward movement of the vitreous body may carry the IOL anteriorly.The lens’s hinges take advantage of this purported anterior movement of the lens. Placing a hinge between the haptic and the optic makes it easier for the lens to move, and the use of longer haptics increases the amplitude of movement.
The implantation technique is similar to that with other IOLs, though the surgeon has to pay a bit more attention to the loops at the end of the haptics.
Early clinical reports from the USA, Mexico and Canada indicate that CrystaLens can achieve excellent visual acuity and improvements in accommodation in presbyopic patients.
Posted by dastjerdi at 09:40 AM
Quiz
Arch Ophthalmol May 2002;120:659-661
An 8-year-old boy was referred with reduced vision and a pale left optic nerve disc. He was noted to have occasional yellow-brown macules of varying diameter on the left chest wall. Corrected visual acuities were 20/15 OD and 20/30 OS, with left optic atrophy. MRI scanning is shown in Figure. A full systemic evaluation was performed, but no treatment was initiated. Visual acuity remained stable during the next 2 years, and then gradually improved to 20/20 OS. Five years after the initial visit, he had developed segmental myelination of the peripapillary retinal nerve fibers in the left eye (fundus photo). These findings have remained unchanged for 2 years.You make the diagnosis and explain the cause of spontaneous improvement in visual function preceded the retinal myelination.
Posted by dastjerdi at 03:53 AM
May 14, 2002
Corneal endothelial cytotoxicity of diluted povidone-iodine
Am J Ophthalmol 2002 May;133(5):737
J Cataract Refract Surg June 2001;27:941-947
In an in vitro study, cultured bovine corneal endothelial cells were exposed to diluted povidone-iodine (PI). In an in vivo study, a single dose of diluted PI was injected into the anterior chamber of rabbit eyes, completely replacing the aqueous humor. In vitro, PI concentrations of 0.05% or less did not induce endothelial cell damage. Significant damage was observed with a PI concentration of 0.1%. In vivo, PI concentrations of 0.1% or less did not induce changes in corneal endothelium morphology or function as assessed by specular microscopy and pachymetry. A PI concentration of 1% served as a positive control, causing corneal edema and endothelial cell loss as demonstrated by pachymetry, histopathology, and elevated intraocular pressure. The authors conclude that concentrations of PI tolerated by the animal endothelium in vitro and in vivo were higher than the reported bactericidal levels. These findings justify further investigation of the safety and efficacy of PI for intracameral prophylaxis during surgery.
Posted by dastjerdi at 03:41 AM
May 10, 2002
Botulinum Toxin Injection Effective for Graves' Ophthalmopathy
EyeNet May 2002
Botulinum toxin type A injections using a subconjunctival approach may be effective in the treatment of upper eyelid retraction associated with thyroid eye disease (Graves' ophthalmopathy). Eleven patients with superior scleral exposure associated with thyroid eye disease underwent one or more treatments with injections of Botox into the subconjunctival space at the superior margin of the tarsal plate. All patients developed some improvement in the amount of lid retraction after the injections, with the effect lasting from one to 40 months.
Posted by dastjerdi at 06:47 AM
May 09, 2002
FDA accepts first custom wavefront-guided application
Ocular Surgery News
U.S. regulators have accepted Alcon's pre-market approval application for its custom wavefront-guided laser eye surgery device, the LadarWave surgical system.
The LadarWave measures the optical aberrations of the entire eye, which are then interpreted by the company's LadarVision excimer laser to reshape the cornea, according to a company press release. Alcon executives noted this is the first marketing application accepted by the Food and Drug Administration for custom wavefront-guided devices.
Posted by at 10:27 AM
Minimizing risk to the capsule during surgery for posterior polar cataract
J Cataract Refract Surg May 2002; 28:742–744
An important clinical feature of posterior polar cataract is a significant incidence of extreme capsule weakness (or perhaps even absence) in the area of polar opacity. 26% incidence of posterior capsule rupture was reported in these cases.
Hydrodissection of the cortex, particularly cortical cleaving hydrodissection in the presence of a weakened or deficient posterior capsule, is hazardous and can result in blowout of the posterior capsule with loss of the nucleus into the vitreous. Here is a report of a technique that is helpful in cases of a weak or deficient posterior capsule. The goal is to leave the posterior cortex undisturbed until the very last moment.
The initial preparation stages of the surgery are unchanged up to and including the capsulorhexis. Gentle hydrodelineation (Figure A) is then performed, attempting to separate the nucleus from the epinucleus/cortex. Extreme care is taken not to inject until the cannula is deeply embedded in the lens. The nucleus is then carefully removed by gentle phacoemulsification, avoiding rotation, with the aim of disturbing the cortex as little as possible. A reduced flow rate and bottle height are used to minimize fluid flow and turbulence through the eye. Next, an ophthalmic viscosurgical device (OVD) is used to create a viscodissection plane between capsule and cortex (Figure B). Viscodissection is safe in this context because it is gentle and controlled and can be stopped when part way around the posterior capsule. If this is applied in 4 quadrants, a shell of cortex/epinucleus can be made to fold in on itself toward the center of the lens while the posterior pole remains undisturbed. The shell is gently removed from each quadrant with the I/A handpiece (Figure C) using a low-flow, low-vacuum technique. This leaves a small posterior plaque (Figure D) containing cortex and the posterior polar plug. The plaque can be gently peeled from the capsule with gentle aspiration or the OVD. If there is a hole in the capsule at this stage, little cortex and no nucleus is left to complicate the management and the chances of extending the defect or experiencing vitreous loss are greatly reduced. If the preoperative diagnosis of posterior polar cataract is incorrect and a dense posterior subcapsular cataract is found at this stage, there is often a "fibrotic" plaque remaining on the posterior capsule. In some cases, the plaque can be carefully peeled from the posterior capsule after an edge is defined or the existing edge lifted. If the plaque cannot be peeled and is sufficiently dense to potentially reduce vision, a posterior curvilinear capsulorhexis can be performed. This preserves the anterior vitreous face and reduces the risk of later retinal complications. The technique is useful in cases of zonular weakness, preexisting capsule tears, or similar surgically induced problems arising perioperatively.
Posted by dastjerdi at 06:56 AM
May 07, 2002
Cidofovir 1% as a topical treatment of acute adenoviral keratoconjunctivitis
Ophthalmology May 2002; 109: 845-850
Cidofovir has a therapeutic effect in the treatment of AKC in the 1% dosage. In particular, cidofovir is the first drug that is targeted at the cause of the development of corneal opacities. The researchers saw no severe corneal opacities in any of the cidofovir groups compared to 30% with severe opacities in the control group. Its clinical use, however, is limited by severe dose-dependent local toxicity (conjunctivitis, conjunctival pseudomembranes, and erythematosus inflammation of eyelids skin) that may be overcome by an improved pharmaceutical preparation of cidofovir eyedrops, by applying a concentration of cidofovir between 0.2% and 1%, by reducing the frequency of administration, or by reducing the overall treatment period.
It is the corneal involvement that sets AKC apart from other forms of viral conjunctivitis. During the course of the infection, approximately 10 days after onset of symptoms, corneal subepithelial opacities frequently develop. These nummular opacities or infiltrates can impair visual function and can persist for months to years.The pathogenesis of the nummular opacities most likely includes a persisting viral replication in subepithelial keratocytes, triggering an immunologic host reaction. This hypothesis is supported by the clinical observation that opacities usually resolve with topical steroid treatment but recur when steroids are discontinued.
Posted by dastjerdi at 11:49 PM
PDT may be helpful for chronic central serous chorioretinopathy treatment
OCULAR SURGERY NEWS EUROPE/ASIA-PACIFIC EDITION May 2002
A 55-year-old man complained of decreased vision in his left eye for one year, worsening 1 month before PDT (left) and two months after PDT, fluorescein angiogram of the same eye show clearing of the central serous chorioretinopathy (right).
Patients with central serous chorioretinopathy reported subjective improvements, sustaining 6 months after receiving photodynamic therapy treatments, in a small study presented at the American Academy of Ophthalmology meeting in New Orleans. All seven eyes in the study had at least two lines of visual improvement in Snellen acuity. All patients had chronic central serous chorioretinopathy symptoms with either no improvement or a decline in status for more than 6 months prior to PDT.
The etiology of central serous chorioretinopathy is unclear. Often management of the disease is subjective, with disagreement among colleagues that can result improper patient management. A larger prospective study is needed to establish the individual characteristics of central serous chorioretinopathy, as well as to assess the true efficacy of photodynamic therapy on the condition. Photodynamic therapy has been applied successfully in the treatment of choroidal neovascularization in a number of conditions. Recently, a study reported that at least part of the PDT effect on the closure of the choroidal neovascular membrane may lead to decreased choroidal blood flow. It is hypothesized that PDT may be effective in decreasing the state of hyperperfusion in affected areas of the choriocapillaris during the course of central serous chorioretinopathy.
Posted by dastjerdi at 02:35 AM
May 05, 2002
IOLs donated for Ridley Day
Ocular Surgery News
Rayner Intraocular Lenses Limited, has donated a day s production of lenses to charity, with half going to Sight Savers International and the other half to Impact Foundation, which will use them to restore sight to people around the world blinded by cataract.
The lenses are donated as part of the 2001 Ridley Day celebrations on November 29, held to mark the world s first operation to implant an IOL by the late Sir Harold Ridley on Nov. 29, 1949. Mr. Ridley worked closely with Rayner to develop the first IOL more than 50 years ago.
Rayner donated 1,000 PMMA lenses to these two charities.
Posted by at 07:34 PM
ASCRS appoints advisory board on LVC education
Ocular Surgery News
The American Society of Cataract and Refractive Surgery has appointed a medical advisory board to oversee the organization s laser eye surgery education initiative, scheduled to launch in June. The panel, which comprises four ophthalmologists, will advise and support the ASCRS in its endeavor to educate the public about the risks and benefits of laser eye surgery, with a focus on the importance of active discussion between patients and their physicians. The medical advisory board s function is to review all campaign activity, provide medical expertise, and ensure scientific accuracy.
Posted by at 07:34 PM
Very Elderly Should Not Be Excluded From Cornea Donation
Br J Ophthalmol 2002;86:404-411
Corneas procured from very old donors have a graft survival rate and visual acuity score similar to that of corneas procured from younger donors, according to a report in the April issue of the British Journal of Ophthalmology.
Dr. Philippe Gain, of the University Hospital Center of Saint-Etienne, France, and colleagues studied 419 corneas stored in organ culture to assess the suitability of corneas from very old donors for grafting after banking.
There were 330 corneas from donors under 85 years of age (group 1) and 89 corneas from donors at least 85 years of age (group 2). "Endothelial cell density (ECD) before and after organ culture, discard rate before and after storage, and clinical and endothelial outcomes of the 196 penetrating keratoplasties (PKP) (158 in group 1 and 38 in group 2) were compared in a prospective longitudinal study."
Group 2 had a lower baseline ECD than group 1, at 2022 cells/mm squared and 2217 cells/mm squared, respectively (p = 0.011). The rate of elimination for low ECD was 38% in group 2, compared with 20.2% in group 1 (p = 0.001).
"At the end of storage, because very old corneas lost fewer endothelial cells than younger ones (respectively 4.2% versus 9.5%, p = 0.022), ECD was comparable between the two groups," the authors explain.
"The corneas of very old donors had a poorer macroscopic appearance at procurement and during surgery," Dr. Gain and colleagues report. However, overall graft survival was 87.4% in group 1 and 80.6% in group 2, a nonsignificant difference. After 25 months of follow-up, visual acuity and ECD was similar between the groups.
Considering the aging of the population, "the very elderly should not be deemed off limits for corneal procurement," the investigators conclude."
Posted by at 01:28 PM
May 03, 2002
RK marker can guide capsulorrhexis
Ocular Surgery News 5/1/02
Marking the cornea at the beginning of cataract surgery can make it easier to size and center the capsulorrhexis. When the marker was used, the capsulorrhexis was more frequently found to be postoperatively centered and correctly overlapping the anterior IOL circumference. if the capsulorrhexis exactly overlaps the 5-mm corneal mark, its true diameter is 4.2 mm on average, with a standard deviation of 0.1 mm. The variability depends upon corneal power and anterior chamber depth.
Posted by dastjerdi at 05:25 AM
Intraocular lens power calculation software
J Cataract Refract Surg May 2002; Volume 28, Issue 5: 735-736
Online calculation of intraocular lenses is being offered by the ultrasound laboratory of the University Eye Clinic Wurzburg as a novel and special free service. Calculations may be performed for two user-defined intraocular lenses on the basis of different algorithms. At present, the SRK II formula , the HOFFER Q formula as well as the calculation according to Haigis are implemented. It is planned to add further lens calculation algorithms in the future. IOL calculation according to HAIGIS may be carried out in several ways. In default mode the calculation is based on the A or ACD constants entered for the individual IOLs. For an individual calculation surgeon-specific constants are used, which are derived from an analysis of the respective surgeon's postoperative results.
Standard calculation Extended calculation
Posted by dastjerdi at 12:15 AM
May 02, 2002
Optimized IOL constants for the Zeiss IOLMaster
Every IOL constant depends on axial length L, corneal radius R, IOL power P, refraction X, and on the preop anterior chamber depth d. Any change in one of the variables L, R, P, X or d will cause a corresponding change in the respective IOL constant. If a new axial length measuring device is bought, it may measure e.g. 0.3 mm longer than the old one. This change DL=0.3 mm in axial length determination will be responsible for a change in the respective IOL constant. Likewise, if a new keratometer consistently gave 0.10 mm steeper radii than an old one, this shift of DR=0.10 mm will again be reflected in a change of the respective IOL constant. So measurement conditions (optical vs ultrasound) influence on IOL constants. Accordingly, the new (IOL Master) constants are calculated from the old constants as follows:
SRK II: IOLMaster Aconstant = old Aconstant + 0.91 D
SRK/T: IOLMaster Aconstant = old Aconstant + 0.87 D
HofferQ: IOLMaster pACD = old pACD + 0.65 mm
Holladay-1: IOLMaster sf = old sf + 0.60 mm
Haigis: IOLMaster a0 = old a0 + 0.81 mm
Also the following rules of thumb may be applied as a starting point to estimate new IOL constants for optical biometry with the Zeiss IOLMaster:
A(IOLMaster) = A(Ultrasound)+ 3 x [AL(IOLMaster) - AL(Ultrasound)]
Posted by dastjerdi at 11:23 PM
Comparison of iris-fixed Artisan lens implantation with excimer laser in situ keratomileusis in correcting myopia between -9.00 and -19.50 diopters
Ophthalmology May 2002; 109: 955-964
In this study, Artisan lens implantation and LASIK were found to be similarly effective, stable, and reasonably safe for the correction of myopia between -9.00 and -19.50 diopters. Better uncorrected and spectacle-corrected visual acuity and contrast sensitivity, a lower enhancement rate, and exchangeability are the main advantages of Artisan lens implantation.
At 1 year, the mean spherical equivalent refraction was -0.64 ± 0.8 D in Artisan eyes and -0.87 ± 0.8 D in LASIK eyes, which does not represent a statistically significant difference. At 1 year, the mean refractive cylinder was 0.83 ± 0.6 D in Artisan eyes and 0.41 ± 0.3 D in LASIK eyes. At 1 year, the uncorrected visual acuity was 20/20 or better in 20.9% Artisan eyes and in 12.2% LASIK eyes; 20/30 or better in 69.8% Artisan eyes and 46.3% LASIK eyes, and 20/40 or better in 88.4% Artisan eyes and 58.5% LASIK eyes. There was a statistically significant difference in the final uncorrected and corrected visual acuity after the two procedures at 1 year. No Artisan eyes and five LASIK eyes (12.2%) lost two or more lines of Snellen visual acuity. Seven Artisan eyes (16.3%) and one LASIK eye (2.4%) gained two or more lines. At 1 year, there was no statistically significant difference between the endothelial cell loss in both groups. Severe night glare in one eye (2.2%) of the Artisan group and seven eyes (14.6%) of the LASIK group was the most prominent complication in this study. Thirteen (72.2%) of the 18 patients who received the Artisan lens in one eye and LASIK in the other preferred the Artisan lens to the LASIK, mainly because of the better quality of vision. The significantly better uncorrected and corrected visual acuity in the Artisan group 1 year after the surgery can be explained at least partly by the magnification of the retinal image and the preservation of the corneal asphericity after Artisan implantation. On the other hand, every eye that receives LASIK ends with an oblate cornea that increases the optical aberrations. LASIK procedure was easier and less technically demanding, whereas the Artisan implantation was more complex and more strenuous for both the surgeon and the patient. Patient tolerance during and immediately after the surgery was generally better with the LASIK procedures. LASIK has the known advantage of correcting astigmatism, whereas commercially available Artisan lenses have only spherical powers.
Posted by dastjerdi at 01:46 AM