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November 28, 2002
Eye Word
Peripheral iridectomies may be unnecessary in trabeculectomy cases
Mohen Tabrizi. MD
Peripheral iridectomy may not be needed for a trabeculectomy for primary open-angle glaucoma [POAG], except in phakic eyes that are hyperopic with an axial length of less than 22.5 mm, according to researchers who presented two award-winning papers at the annual meeting of the American Society of Cataract and Refractive Surgery. Additionally, peripheral iridectomy may not be necessary in most cases of phacotrabeculectomy for POAG.
Certain techniques in surgery can be modified to improve the safety and success rate of filtering surgery without an iridectomy. Modifications include the creation of a fistula more anteriorly into clear cornea. This increases the distance of the ostium from the iris and creates a valve-like effect that reduces the likelihood of postoperative shallowing of the anterior chamber, Ahmed said.
To determine whether a trabeculectomy or a phacotrabeculectomy can be safely performed without a routine peripheral iridectomy in patients at low risk for early complications, Ahmed and his colleagues at the Moran Eye Center conducted a study. Another goal of the study was to compare the success of peripheral iridectomies vs. the lack of them.
Patients were given topical or retrobulbar anesthesia, and physicians made a fornix-based conjunctival flap. Then a 4-mm by 3-mm rectangular or trapezoidal scleral flap was fashioned. This was dissected quite far anteriorly into clear cornea, past the vascular arcades, Ahmed said. “An antimetabolite was then applied when needed after the sclera dissection.�. For phacotrabeculectomy, physicians used a two-site approach with a polyacrylic foldable intraocular lens, and viscoelastic was removed from the anterior chamber after the scleral sutures were placed, Ahmed said.
Peripheral iridectomies were not performed routinely for combined procedures unless there was significant intraoperative iris prolapse. Iridectomies were performed routinely in trabeculectomies for angle-closure glaucoma, hyperopia, eyes that had a short axial length, or in cases of significant intraoperative iris prolapse.
During the study period, 112 trabeculectomies were performed with a mean follow-up of approximately two years: 76 cases were done without peripheral iridectomies and 36 were done with peripheral iridectomies. Additionally, 158 phacotrabeculectomies were performed with similar follow-up: 120 were done without iridectomies and 38 with iridectomies..
The group that did not receive peripheral iridectomies had reported no cases of pupillary block or iris incarceration. There was increased hyphema formation and increased inflammation in the iridectomy group,� Ahmed said.
However, eyes in the phacotrabeculectomy group that required iridectomies generally had shorter axial lengths. “There were no cases of iris incarceration or pupil block in the 120 cases that were done as a combined procedure without an iridectomy,� Ahmed said. “Of note, there was increased hyphema formation in the group that required or had iridectomies.�
IOP results during the two years were similar between the groups that had iridectomies and those that did not. “As far as success, there was a trend for increased success when the filtering surgery was done without an iridectomy,� he said.
If there is significant iris prolapse intraoperatively, it behooves the practitioner to perform an iridectomy, Ahmed said.
Posted by at 10:57 PM
OSN Supersite
TOP STORIES 11/19/02
Allergy can affect corneal shape
Mohsen Tabrizi. MD
BEER-SHEBA, Israel — Patients with vernal keratoconjunctivitis show more abnormalities on corneal topography than normal patients, according to a study. The abnormalities include an increase in corneal steepening in VKC patients.
Corneal topography may help clinicians decide how best to manage the disease, the study authors suggest.
Ruth Lapid-Gortzak, MD, and colleagues here at Soroka University Medical Center examined 40 patients with vernal keratoconjunctivitis (VKC) and 36 control subjects, comparing EyeSys videokeratography, numerical corneal indices and spherical equivalent refraction.
The patterns of corneal topography were abnormal in nearly 71% of the VKC group compared with 40% of the control group. Maximal corneal power was significantly higher in the VKC group compared with the control group as well.
Pediatric patients with vernal keratoconjunctivitis had a “statistically significant increase in keratoconus patterns� over control patients, according to the study.
Patients with VKC had significantly more abnormal corneal videokeratography patterns, higher maximal corneal dioptric power and increased superior-to-inferior asymmetry, with a trend to more superior corneal steepening. Nine eyes with VKC had keratoconus; none of the eyes in the control group did. Thirteen more eyes in the VKC group had patterns with a topographic trend to keratoconus, as compared to five eyes of five patients in the control group.
Superior steepening patterns were found to be common in VKC patients, although superior keratoconus is considered rare.
The study is published in the November issue of "Ophthalmology".
Posted by at 10:29 PM
OSN Supersite
TOP STORIES 11/11/02
Sclerotomy not effective for presbyopia, can cause complications
Mohsen Tabrizi.MD
LOS ANGELES — Anterior ciliary sclerotomy did not restore accommodation in eyes with presbyopia and caused significant complications in a small study here.
Surgeons at the Jules Stein Eye Institute performed anterior ciliary sclerotomy in one eye each of nine presbyopic patients. None of the patients had had any previous ocular surgery except corneal refractive procedures. The contralateral eye served as a control. Follow-up was 6 months for all patients.
The researchers used both a primary and a secondary control to assess changes in accommodative amplitude and near vision through best distance correction.
Two complications were encountered. In one eye, an anterior chamber perforation resolved without sequelae after suturing. In another, a mild case of anterior segment ischemia was seen, manifested by sectoral iris akinesis.
“The intraoperative complication of a perforation is not a surprising occurrence, given that the goal of the anterior ciliary sclerotomy technique used here was to make an incision that is as near full scleral thickness as possible to achieve a maximal therapeutic result,� the study authors reported in the November issue of Ophthalmology.
“We found no short-term or long-term effect from anterior ciliary sclerotomy,� the authors concluded. They note that their findings are in “sharp distinction� to previous reports.
“In this study, the lack of efficacy of anterior ciliary sclerotomy and the potential for significant complications calls into question whether this or any other scleral surgical technique is an appropriate treatment for the correction of presbyopia. Better controlled studies are needed before widespread adoption of these techniques,� they conclude.
Posted by at 10:00 PM