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Biomedical subjects

D R Chow

Publications and source records attributed to D R Chow.

7 recordsLinked to original sources
PubMed2000

Effect of perifoveal tissue dissection in the management of acute idiopathic full-thickness macular holes.

OBJECTIVE: To evaluate the efficacy of perifoveal tissue dissection (PTD) on patients undergoing pars plana vitrectomy for idiopathic macular holes of less than 1-year's duration. METHODS: Pars plana core vitrectomy was performed on 107 eyes of 104 consecutive patients with acute idiopathic macular holes. One cohort had routine PTD. In the other cohort, no attempt was made to strip preretinal tissue. Follow-up was longer than 6 months (follow-up range, 6 to 36 months). RESULTS: Overall, 95 (89%) of all macular holes were closed. Visual acuity improved 2 lines or more of the Snellen letter chart in 91 eyes (85%). A postoperative visual acuity of 20/50 or better was achieved in 79 eyes (74%). A transient increase in intraocular pressure (230 mm Hg) developed in 25 eyes (23.4%). In 6 eyes (5.6%) a retinal detachment developed. One eye had retinal pigment epithelial changes and 1 patient reported peripheral field loss. No statistically significant differences were noted between eyes having PTD and those without PTD for any outcome measure. CONCLUSION: In this series, no beneficial or adverse effect could be demonstrated by performing PTD in eyes undergoing pars plana core vitrectomy for acute idiopathic macular holes.

Acute Disease↗
PubMed2000

External versus internal approach to the removal of metallic intraocular foreign bodies.

OBJECTIVE: To review the management of metallic intraocular foreign bodies (IOFB) at a single institution and to compare the use of internal and external approaches for their removal. SUBJECTS AND METHODS: A retrospective review was conducted on 70 eyes from 70 patients who underwent surgical removal of a metallic IOFB with either an internal (vitrectomy followed by forceps or internal magnet use) or external approach (large electromagnet) by seven vitreoretinal surgeons at a single institution between 1973 and 1996. Visual acuity and complications occurring with the two approaches were the main outcome measures studied. RESULTS: Overall, patients showed significant improvement in visual acuity following surgical intervention (P < 0.001) despite widely varying surgical techniques. When the authors compared patients treated with an external versus an internal approach they found no statistically significant difference with regard to visual outcome and a trend toward a higher rate of postoperative endophthalmitis in the external approach group. CONCLUSION: Surgical removal of metallic IOFB results in significant visual improvement. The external approach to the removal of magnetic metallic IOFB remains a viable treatment option in select cases.

Adolescent↗
PubMed1999

Successful closure of traumatic macular holes.

PURPOSE: To establish the efficacy of vitreoretinal surgery without the use of transforming growth factor-beta or autologous platelet concentrate in the repair of traumatic macular holes. METHODS: This retrospective review consisted of 16 eyes from 16 consecutive patients treated by five vitreoretinal surgeons at a single institution between 1993 and 1997. Intervention included pars plana vitrectomy with creation of posterior vitreous detachment, placement of 14% to 16% C3F8 gas, and postoperative face-down positioning. Ten eyes received intraoperative autologous plasmin to facilitate formation of posterior vitreous detachment. Main outcome measures were anatomic closure rate and visual outcome. RESULTS: Anatomic closure of the macular holes was achieved in 15 (94%) of 16 eyes, with an average follow-up of 7 months. Six (38%) eyes achieved visual acuity of 20/40 or better. Visual acuity improved by 2 or more lines in 11 (69%) of 16 eyes. The average preoperative logMAR-converted visual acuity of 20/175 improved to 20/60 postoperatively. CONCLUSION: Traumatic macular holes can be closed successfully with substantial visual recovery without the use of transforming growth factor-beta or platelet concentrate.

Adolescent↗
PubMed1998

Refractive changes associated with scleral buckling and division in retinopathy of prematurity.

OBJECTIVE: To examine the refractive changes that occur in infant eyes with retinopathy of prematurity (ROP) retinal detachments that are subjected to scleral buckling and subsequent division of the scleral buckle. METHODS: A retrospective medical record review of infants with ROP who were managed with an encircling scleral buckle that was subsequently divided and who underwent refraction evaluation during and after division of the scleral buckle. RESULTS: Seven eyes from 6 patients had scleral exo-plants placed for stage 4 ROP retinal detachments at a mean postconceptional age of 48 weeks. The mean refractive error in eyes with the scleral buckle was -11 diopters (D) (range, -5 to -25 D) with an induced mean anisometropia of -9.5 D. After division of the scleral buckle at a mean of 36 weeks postoperatively, the average post-scleral buckle refractive error was -5.68 D, resulting in a mean myopic reduction of 5.5 D. CONCLUSIONS: Scleral buckling in infants with ROP results in large myopic shifts, which are significantly reduced after division of the scleral buckle. This highlights the importance of repeated refraction testing in infants after placement and division of the scleral buckle to avoid refractive amblyopia.

Birth Weight↗
PubMed1998

Visual field defect after pars plana vitrectomy.

OBJECTIVE: This study aimed to report the occurrence of visual field defects after pars plana vitrectomy (PPV) for the treatment of each of the following conditions: macular hole (MH), subretinal neovascular membrane (SRNVM), and epiretinal membrane proliferation (EMP). This study also aimed to speculate on the pathogenic mechanisms for the observed field defects. DESIGN: Noncomparative case series. PARTICIPANTS: The study included 48 subjects (50 eyes). Twenty-one of the 50 eyes had stage III MH, 13 eyes had SRNVM, and 16 eyes had EMP. TESTING: Goldmann kinetic perimetry was performed postoperatively. MAIN OUTCOME MEASURE: Visual field defects. RESULTS: Nine (18%) of the 50 eyes had visual field defects. Four (19%) of the 21 eyes with MH and 5 (38%) of the 13 eyes with SRNVM had visual field defects. Of the 16 patients who had epiretinal membrane peeling, none had a visual field defect. An air-fluid exchange had been performed in all patients found to have a postvitrectomy field defect. The difference in rate of visual field defects in eyes that had air-fluid exchange (EMP group) was statistically significant (P < 0.05, chi-square). No significant correlation was found between visual field defect and preoperative intraocular pressure, postoperative intraocular pressure, patient's age, and iatrogenic detachment of the vitreous cortex. The field defects identified were altitudinal (2 eyes), baring of the blind spot (1 eye), inferotemporal (3 eyes), inferonasal (2 eyes), and superonasal (1 eye). CONCLUSIONS: Central and peripheral visual field defects may occur after PPV for the treatment of MHs or SRNVMs. Air-fluid exchange procedure was the common denominator in all of the patients found to have visual field deficit. The etiology is likely to be trauma to the optic nerve region during the air-fluid exchange procedure.

Adult↗
PubMedDate not supplied

Microbubble retention and failed macular hole surgery.

This case reports a possible new cause of failed macular hole surgery. Standard macular hole surgery with removal of epiretinal membranes, 16% C3F8, and strict postoperative prone positioning was performed on a patient with stage 4 macular hole. Macular hole surgery failed with retention of a microbubble of C3F8 within the macular hole during the follow-up period. Retention of a microbubble within a macular hole may prevent closure of the hole and be a previously unrecognized cause of failed macular hole surgery.

Epiretinal Membrane↗