Biomedical subjects
Amir Pirouzian
Publications and source records attributed to Amir Pirouzian.
Ahmed glaucoma valve implants in the pediatric population: the use of magnetic resonance imaging findings for surgical approach to reoperation.
PURPOSE: To describe and to evaluate a novel application of magnetic resonance imaging (MRI) in determining the Ahmed glaucoma valve (AGV) function after implantation. METHODS: Retrospective interventional case series of all surgical glaucoma patients in one practice were identified and orbital MRI series were performed. Orbital MRI findings were evaluated in all children who had undergone Ahmed glaucoma valve insertion. RESULTS: A total of six patients were identified, ranging in age from 1 to 14 years. Mean follow-up time ranged from 1 to 3 years from the time of first tube insertion. Gadolinium enhancement MRIs showed an enhanced large cystic cavity over the plate in five patients, indicating partial to complete patency of the outflow of the tube. One MRI failed to show an enlarged enhanced bleb over the plate region, indicating potential obstruction of outflow. Surgical irrigation of the tube displayed obstruction. Ahmed tube exchange was performed. Enhanced cystic bleb showed compression of the extraocular muscles in four patients. These patients exhibited mild to moderate restrictive strabismus. No lenticular opacification was noted in the four phakic patients. CONCLUSIONS: Early and late AGV failure and subsequent intraocular pressure rise are of great concern after pediatric glaucoma shunt surgery. Orbital MRI series should be considered in the cases of possible AGV drainage failure. In cases of reoperation, orbital MRI findings could be of great clinical value to evaluate for functional patency as well as for the EOM surgical intervention approach. To avoid unnecessary surgical exploration/explantation, orbital MRIs with gadolinium-dye enhancement should be considered in evaluating postshunt glaucoma surgical patients.
One-year outcomes of a bilateral randomized prospective clinical trial comparing laser subepithelial keratomileusis and photorefractive keratectomy.
PURPOSE: To compare laser subepithelial keratomileusis (LASEK) and photorefractive keratectomy (PRK) in different eyes of the same patients in terms of visual acuity, refractive error, and complications over 1 year. METHODS: This prospective, randomized, double-masked study comprised 30 active-duty military personnel with myopia who underwent LASEK in one eye and PRK in the other eye. RESULTS: Twenty-eight patients' results were available for 1-year follow-up. The primary outcome measures were visual acuity and refractive error. The mean visual acuity for the LASEK group was 1.56 and 1.67 for the PRK group (z = -0.18, P = .15). The mean spherical equivalent refraction for the LASEK group was -0.007 D and +0.124 D for the PRK group (t = 0.982, P = .40). No significant differences were noted in visual acuity or refractive error in the eyes that had LASEK versus the eyes that had PRK. CONCLUSIONS: After 1-year follow-up, LASEK and PRK show similar levels of visual acuity and refractive error.
A randomized prospective clinical trial comparing laser subepithelial keratomileusis and photorefractive keratectomy.
OBJECTIVE: To compare laser subepithelial keratomileusis (LASEK) and photorefractive keratectomy (PRK) in different eyes of the same subjects for subjective pain level, visual acuity, and corneal epithelial healing. DESIGN: Prospective, randomized, double-masked study. SETTING: David Grant US Air Force Medical Center, Travis Air Force Base, Calif. PARTICIPANTS: A convenience sample of 30 active-duty military members with mild to moderate myopia. METHODS: All patients had LASEK performed in one eye and PRK performed in the contralateral eye; the order of surgical procedures (ie, right eye first or left eye first) and the choice of procedures (ie, PRK in the right eye and LASEK in the left eye or LASEK in the right eye and PRK in the left eye) were determined in advance using a block randomization table. MAIN OUTCOME MEASURES: The primary outcome measures were subjective pain level and the rate of corneal epithelial defect recovery. Postoperatively, subjects were evaluated for their subjective pain level, visual acuity, and corneal healing (ie, epithelial defect size) during the first week and up to 30 days after undergoing the surgical procedures. RESULTS: There were no significant differences in subjective pain levels between the LASEK- and PRK-treated eyes on postoperative days 1, 2, or 3 (P>.05) or in visual acuity on postoperative days 3, 7, or 30 (P>.05). There was a statistically significant (P<.001) smaller median epithelial defect in the LASEK-treated group (1.0 mm(2)) compared with the PRK-treated group (16.0 mm(2)) on postoperative day 1. However, by postoperative day 3, the PRK-treated group (0.0 mm(2)) showed significantly (P<.001) smaller epithelial defects compared with the LASEK-treated group (4.0 mm(2)). By postoperative day 7, epithelial defects were undetectable in any subjects in either group. CONCLUSIONS: Laser subepithelial keratomileusis and PRK have similar postoperative pain thresholds and visual acuity recordings. However, the epithelial healing pattern for LASEK and PRK differs. No additional clinical benefit is seen from the LASEK procedure relative to the PRK procedure.
Inferior rectus pulley hindrance: a mechanism of restrictive hypertropia following lower lid surgery.
PURPOSE: This article describes a new mechanism of restrictive strabismus associated with inferior rectus (IR) pulley hindrance complicating lower eyelid surgery. METHODS: We studied five patients who developed hypertropia in infraduction after bilateral lower eyelid surgery. Complete ophthalmologic examination and multipositional, high-resolution orbital imaging by computed X-ray tomography (CT), or magnetic resonance imaging (MRI) was performed. Comparison was made with MRI in normal volunteers. RESULTS: There was restriction to passive infraduction of the involved eyes. Sagittal MRI images showed hindrance to normal posterior shift of the IR pulley from central to infraducted gaze. Intraoperative findings of contracture of the inferior fornix and dense fibrous scar tissue from the inferior orbital rim to the IR pulley complex correlated with restricted infraduction and imaging findings. Release of the scar tissues around the IR pulley improved infraduction, reducing or eliminating diplopia. CONCLUSION: Scar formation hindering anteroposterior travel of the IR pulley system is a novel mechanism of restrictive hypertropia in infraduction following lower eyelid surgery. This restrictive strabismus, the iatrogenic equivalent of retroequatorial myopexy, is distinct from paralytic strabismus and must be managed differently. Avoidance and treatment of this complication of lower eyelid surgery requires knowledge of anatomical relationship between the IR pulley and lower eyelid.