Penny McAllum

University of Toronto, Toronto, Ontario, Canada

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Publications (20)48.77 Total impact

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    ABSTRACT: To assess the prognostic factors influencing visual prognosis and length of treatment after acanthamoeba keratitis (AK). Forty-two AK eyes of 41 patients treated between 1999 and 2006 were included. A diagnosis of AK was made on the basis of culture results with a corresponding clinical presentation. We calculated the prognostic effect of the various factors on final visual acuity and the length of treatment. Multivariate regression analysis was used to adjust for the simultaneous effects of the various prognostic factors. Mean follow-up was 19.7 ± 21.0 months. Sixty-four percent of cases had > 1 identified risk factor for AK, the most common risk factor being contact lens wear (92.9% of eyes). At presentation, median best spectacle corrected visual acuity (BCVA) was 20/200 (20/30 to Hand Motion [HM]) that improved after treatment to 20/50 (20/20 to Counting Fingers [CF]). Infection acquired by swimming or related to contact lenses had significantly better final BCVA (p = 0.03 and p = 0.007, respectively). Neuritis and pseudodendrites were also associated with better final BCVA (p = 0.04 and p = 0.05, respectively). Having had an epithelial defect on presentation and having been treated with topical steroid were associated with worse final best spectacle corrected visual acuity (BSCVA) (p = 0.0006 and p = 0.04). Multivariate regression analysis found a good initial visual acuity (p = 0.002), infections related to swimming (p = 0.01), the absence of an epithelial defect (p = 0.03), having been treated with chlorhexidine (p = 0.05), and not having receive steroids (p = 0.003) to significantly forecast a good final BCVA. We identified several prognostic factors that can help clinicians evaluate the expected visual damage of the AK infection and thus tailor treatment accordingly.
    No preview · Article · Jun 2012 · Canadian Journal of Ophthalmology
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    ABSTRACT: To evaluate the outcomes of femtosecond laser in situ keratomileusis (LASIK) compared to combined LASIK and astigmatic keratotomy in the treatment of refractive errors following penetrating keratoplasty. A retrospective review was performed on 18 eyes of 16 patients who underwent LASIK for visual rehabilitation after penetrating keratoplasty. Seven eyes (38.8%) had undergone paired relaxing incisions with topographic guidance prior to LASIK performance. Preoperative uncorrected visual acuity was 20/100 or worse in 13 eyes (72.2%) and best-corrected visual acuity (BCVA) was 20/40 or better in 15 eyes (83.3%). After LASIK, uncorrected visual acuity was 20/40 or better in 10 eyes (55.5%) and BCVA was 20/40 or better in 17 eyes (94.4%). Three eyes (16.6%) had a loss of 1 to 2 lines of BCVA. No difference in visual outcomes was noted in eyes undergoing LASIK and astigmatic keratotomy versus LASIK alone. An increased complication rate was noted in patients who also underwent astigmatic keratotomy and was associated with flap creation. Femtosecond LASIK is effective in reducing ametropia after penetrating keratoplasty. Astigmatic keratotomy might complicate flap creation in LASIK; therefore, photorefractive keratectomy should be considered for patients who had previous astigmatic keratotomy to reduce astigmatism.
    No preview · Article · Mar 2010 · Ophthalmic Surgery Lasers and Imaging
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    ABSTRACT: The purpose of this study was to assess the incidence and risk factors of Acanthamoeba keratitis (AK) over an 8-year period in a Canadian tertiary care setting. We retrospectively reviewed the medical records of 41 patients (42 eyes), who were diagnosed as having AK between January 1999 and December 2006 in the cornea clinic at the Toronto Western Hospital. The incidence and risk factors of AK were evaluated. The number of cases per year increased from between 0 and 4 in the first 5 years to 9, 14, and 8 in the last 3 years. The annual increasing trend was statistically significant (P = 0.04). The month of onset of disease symptoms showed a trend toward onset in summer and fall and was statistically significant for the difference between January and August (P = 0.0094). The season of onset of disease symptoms showed a trend toward summer onset, and the difference between winter and summer was statistically significant (P = 0.02). 92.9% of cases occurred in contact lens wearers, particularly in soft contact lens wearers (82.1%). The incidence of AK in Canada may be increasing since 2004. There is a seasonal trend toward disease onset in the warmer months.
    No preview · Article · Feb 2009 · Cornea
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    ABSTRACT: To compare the degree of conjunctival autograft inflammation, subconjunctival haemorrhage (SCH) and graft stability following the use of sutures or fibrin glue (FG) during pterygium surgery. Prospective, observer masked, clinical trial. 40 eyes of 40 patients undergoing primary pterygium surgery with conjunctival autograft were allocated into two groups. Group 1 (n = 20) had FG (Tisseel) for attaching the conjunctival autograft, whereas group 2 (n = 20) had sutures. Standardised digital slit-lamp photographs were taken at 1 week, 1 month and 3 months postoperatively. Sutures were masked using commercially available photo-editing software. Two masked observers objectively graded the digital photographs for degree of inflammation, SCH and graft stability. 34 of the 40 patients completed the study. When using FG, the degree of inflammation was significantly less than with sutures at 1 month (p = 0.019) and 3 months (p = 0.001) postoperatively. No significant difference was found for inflammation at 1 week postoperatively (p = 0.518). Conjunctival grafts secured with FG were as stable as those secured with sutures (p = 0.258, p = 0.076 and p = 0.624, at 1 week, 1 month and 3 months, respectively). No significant difference was found in degree of postoperative SCH between the groups (p = 0.417, p = 1 and p = 1, at 1 week, 1 month and 3 months, respectively). This is the first prospective clinical trial confirming that conjunctival grafts secured with FG during pterygium surgery not only are as stable as those secured with sutures, but also produce significantly less inflammation.
    Full-text · Article · Dec 2008 · The British journal of ophthalmology
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    ABSTRACT: To compare a new insertion method using a suture with the standard forceps-assisted insertion of the lamellar corneal graft in Descemet stripping automated endothelial keratoplasty (DSAEK). Interventional, comparative case series. DSAEK was performed on 28 consecutive eyes of 28 patients (mean age +/- standard deviation, 72.5 +/- 9.7 years; 12 males). The donor tissue was prepared using the Moria automated lamellar therapeutic keratectomy microkeratome head with a 300-mm blade depth on a Moria artificial anterior chamber (Moria, Antony, France). The central 9 mm of the recipient's Descemet membrane were stripped through a superior limbal incision. In eight consecutive unselected patients, a 10-0 monofilament suture on a long straight needle was used to insert the folded donor lenticula into the recipient's eye, whereas in the other 20 patients, a standard insertion forceps was used. During the suture insertion, an anterior chamber maintainer was used to fill the anterior chamber continuously with balanced salt solution to prevent its collapse. Suture-assisted DSAEK did not differ significantly from forceps-assisted DSAEK in any of the preoperative parameters. No significant differences were noted in the intraoperative or postoperative complications. Six months after surgery, there were no significant differences in endothelial cell counts (1804 vs 1935 cells/mm(2), respectively), visual acuity (20/40 vs 20/36, respectively), or refraction (spherical equivalent, 0.93 vs 1.05 diopters, respectively). Suture-assisted DSAEK is a valid alternative to forceps insertion; however, it does not seem to offer a significant advantage.
    No preview · Article · Jul 2008 · American Journal of Ophthalmology
  • Penny McAllum · Igor Kaiserman · Irit Bahar · David Rootman
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    ABSTRACT: To investigate the pressure required to rupture femtosecond laser top hat configuration corneal dissections with incomplete dissections. Twenty corneoscleral buttons underwent femtosecond laser top hat configuration dissections. Group A had complete dissections; group B, 100-microm gaps in the anterior side cut; group C, 50-microm gaps in the anterior side cut; group D, 100-microm gaps in the lamellar cut; and group E, 50-microm gaps in the lamellar cut. The pressure required to rupture each cornea was measured. The mean (SD) pressure required to rupture the corneas was 111 (74) mm Hg for group A, 1565 (509) mm Hg for group B, 747 (209) mm Hg for group C, 550 (303) mm Hg for group D, and 392 (166) mm Hg for group E (P = .03 for all compared with group A). Incomplete femtosecond laser top hat dissections are highly resistant to rupture by direct pressurization. Gaps in the anterior side cuts are stronger than comparably sized gaps in the lamellar cuts. Clinical Relevance Undertaking femtosecond laser keratoplasty in a 2-site setting should, theoretically, have a high level of safety. Burst pressures are high enough to resist an inadvertent sudden increase in intraocular pressure providing that incomplete recipient laser dissections are undertaken.
    No preview · Article · Jul 2008 · Archives of ophthalmology
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    ABSTRACT: To compare the outcomes of manual top hat penetrating keratoplasty (PK) versus traditional PK. We reviewed the charts of 71 consecutive patients who underwent manual top hat (n = 36) or traditional (n = 35) PK at our institute. Main outcome measures included best-corrected Snellen visual acuity (BCVA), topographic and refractive results, high-order ocular aberrations, endothelial cell counts, and complication rate. No difference in mean BCVA between the 2 groups was noted after 12 months of follow-up. The mean spherical equivalent power was mild myopia, and the mean astigmatism was <4.2 D cylinder in both groups. There was no difference in total high-order aberrations, except spherical aberrations: 0.88 +/- 0.74 microm in the top hat versus 0.49 +/- 0.41 microm in the traditional PK (P = 0.01). Endothelial cell count was significantly higher in top hat PK group (1978 +/- 277 vs. 1449 +/- 516/mm2 in traditional PK; P < 0.0001), and time to all suture removal was shorter (3.9 +/- 1.5 vs. 9.7 +/- 1.1 months in traditional PK; P < 0.0001). BCVA and refractive results are similar after manual top hat and traditional PK. Top hat PK speeds up suture removal and contributes to higher endothelial cell counts in the grafts 1 year after surgery.
    No preview · Article · Jun 2008 · Cornea
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    ABSTRACT: To compare the long-term outcomes and recurrence rate of extensive versus limited subconjunctival pterygium excision with conjunctival autograft. This retrospective study included 135 consecutive patients (161 eyes) who had pterygium excision with conjunctival autograft at the cornea performed at the cornea service of the Toronto Western Hospital. Ninety-one had limited pterygium excision, and 70 had extensive pterygium excision with conjunctival sparing. Main outcome measures included the recurrence rate. The recurrence rate in the limited excision group was 12.1% compared with only 4.3% in the extensive pterygium excision group (p = 0.14). The mean time to recurrence was shorter with limited excision compared to extensive excision (4.0 vs. 5.3 months, respectively, p = 0.16). Limited pterygium excision had a hazard ratio of recurrence of 3.2 compared with the extensive excision method. Recurrence-free survival analysis showed a significant advantage for the extensive excision group (p = 0.045, log-rank test). Cox proportional hazards regression found that younger age (p = 0.0003), larger area of corneal involvement (p = 0.004), worse preoperative visual acuity (p = 0.01), and limited pterygium excision (p = 0.04) significantly increased the risk for recurrence. Both limited and extensive pterygium excision groups had low recurrence rates. The extensive subconjunctival pterygium excision group tended toward fewer recurrences, which occurred later.
    No preview · Article · Jun 2008 · Current eye research
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    ABSTRACT: To describe the visual outcomes and intraoperative and postoperative complications after penetrating keratoplasty (PK), deep lamellar endothelial keratoplasty (DLEK), Descemet stripping endothelial keratoplasty (DSEK), and Descemet stripping automated endothelial keratoplasty (DSAEK) and to compare the results with those of previously reported series. Prospective, comparative, nonrandomized study. One hundred seventy-seven eyes of 161 consecutive patients who had corneal edema resulting from Fuchs endothelial dystrophy, pseudophakic bullous keratopathy, aphakic bullous keratopathy, failed graft or iridocorneal endothelial syndrome. All patients underwent either PK, DLEK, DSEK, or DSAEK at the Cornea Service of the Toronto Western Hospital. Uncorrected visual acuity (UCVA), best spectacle-corrected visual acuity (BSCVA), manifest refraction, corneal endothelial counts, and postoperative complications. The average 12-month postoperative BSCVA was 20/53 in the PK group, 20/80 in the DLEK group, 20/56 in the DSEK group, and 20/44 in the DSAEK group. The mean spherical equivalent was similar between groups, but tended toward hyperopia in the DSEK and DSAEK groups. The average refractive astigmatism was 3.78+/-1.91 diopters (D) in the PK group and 1.61+/-1.26 D, 1.86+/-1.1 D, and 1.36+/-0.92 D in the DLEK, DSEK, and DSAEK groups, respectively (P<0.0001). Early postoperative donor disc dislocations occurred in 6 (8.8%) patients in the DLEK group, 2 (12.5%) in the DSEK group, and 7 (15.6%) in the DSAEK group (P = 0.0004). Detached grafts were reattached and repositioned by injecting an air bubble to press the donor against the recipient cornea. Primary graft failure occurred in 1 (2.1%) of the PK cases, 2 (2.9%) of the DLEK cases, and 1 (2.2%) of the DSAEK cases; all underwent the same procedure successfully. Average cell loss at 1 year after surgery was 40.11% and was similar in the 4 groups. The DSAEK surgery enabled rapid and better UCVA and BSCVA when compared with PK, DLEK, and DSEK, with significantly lower astigmatism. Endothelial cell loss was similar, but the dislocation rate was significantly higher in the DSAEK group.
    No preview · Article · May 2008 · Ophthalmology
  • Irit Bahar · Igor Kaiserman · Penny McAllum · David Rootman
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    ABSTRACT: To evaluate the stability of different wound configurations for full-thickness penetrating keratoplasty (PK) by using the femtosecond laser in a laboratory model. Twenty-two human corneoscleral rims were mounted on an artificial anterior chamber and underwent full-thickness keratoplasty with the femtosecond laser to create different wound configurations. Five samples were assigned to the traditional PK group, 5 to the "top hat" group, 4 to the "mushroom" group, 4 to "zig zag," and 4 to the "Christmas tree" wound configuration. Wound bursting pressure was evaluated after placement of 4, 8, and 16 interrupted sutures. In the traditional PK group, leakage occurred at 0 +/- 0, 21.6 +/- 2.5, and 49 +/- 6.6 mm Hg after placement of 4, 8, and 16 sutures, respectively. No statistically significant difference was noticed in burst pressure with the zig zag and Christmas tree wound configuration compared with the traditional PK group. In the top hat and mushroom groups, burst pressure was 102 +/- 16.8 (P = 0.008) and 65.8 +/- 5.3 (P = 0.03) mm Hg, respectively, after placement of the 16 sutures. The femtosecond laser-assisted top hat wound configuration for PK was found to be the most mechanically stable compared with the traditional method and mushroom, zig zag, and Christmas tree configurations.
    No preview · Article · Mar 2008 · Cornea
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    ABSTRACT: To report on the clinical use of subconjunctival bevacizumab in patients with corneal neovascularization. The charts of 10 consecutive patients with corneal neovascularization who received subconjunctival injections of bevacizumab (2.5 mg/0.1 mL) were reviewed. Digital photographs of the cornea were graded by 2 masked observers for density, extent, and centricity of corneal vascularization. Image analysis was used to determine the area of cornea covered by neovascularization as a percentage of the total corneal area. No significant ocular or systemic adverse events were observed during 3.5 +/- 1.1 months of follow-up. Seven patients showed partial regression of vessels. The extent decreased from 6.0 +/- 1.2 (SD) clock hours before the injection to 4.6 +/- 1.0 clock hours after bevacizumab injection (P = 0.008). Density decreased from 2.7 +/- 0.2 to 1.9 +/- 0.3, respectively. (P = 0.007). No change was noticed in the centricity of corneal vessels. Corneal neovascularization covered, on average, 14.8% +/- 2.5% (SD) of the corneal surface before the injections, compared with 10.5% +/- 2.8% (P = 0.36, t test) after bevacizumab injection. Therefore, bevacizumab decreased corneal neovascularization by 29%. Short-term results suggest that subconjunctival bevacizumab is well tolerated and associated with a partial regression of corneal neovascularization.
    Full-text · Article · Mar 2008 · Cornea
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    ABSTRACT: We report on the use of subconjunctival bevacizumab on corneal vessel density in recurrent pterygia. The charts of 5 patients with recurrent pterygium, who received subconjunctival injections of bevacizumab (2.5 mg/0.1 ml) were retrospectively reviewed. Ophthalmic evaluation included Snellen visual acuity (VA), tonometry and complete examination before the injection and at 1 week and 1 and 3 months thereafter. Digital photographs of the eyes were analyzed by image analysis software to determine the area of cornea covered by new vessels as a percentage of the total corneal area. No ocular or systemic adverse events were observed. No change in visual acuity was noted in any patient following the injection. The mean change in corneal vascularization after one bevacizumab injection was 0.03%+/-0.45, while after two injections the change was 0.025%+/-0.19 (both not statistically different than zero, t-test). Short-term results suggest that subconjunctival bevacizumab is well tolerated but does not cause regression of corneal vessels in recurrent pterygium.
    No preview · Article · Feb 2008 · Current Eye Research

  • No preview · Article · Jan 2008 · Cornea
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    ABSTRACT: To evaluate the advantages of fibrin glue for opposing wound edges in Top Hat penetrating keratoplasty (PKP). Twenty human corneoscleral rims were mounted on an artificial anterior chamber. Eight corneas underwent traditional PKP, 6 underwent Top Hat PKP, and 6 underwent Top Hat PKP by using fibrin glue for opposing wound edges. Mechanical stability was evaluated after placement of 8 and 16 interrupted sutures. Wound bursting pressure and induced astigmatism were evaluated. In the traditional PKP group, wound bursting pressure was 25.2 and 59.1 mm Hg after placement of 8 and 16 sutures, respectively. In the Top Hat PKP, leakage occurred at 57.6 and 103.8 mm Hg after placement of the 8 and 16 sutures, respectively. In the Top Hat PKP + fibrin glue group, wound leakage occurred at 144.6 mm Hg after placement of the 8 sutures and at >158 mm Hg after placement of 16 sutures. The Top Hat PKP + fibrin glue group induced astigmatism of 2.5 D, whereas the traditional PKP group and the Top Hat PKP group showed an induced astigmatism of 3.1 D each. The use of fibrin glue in Top Hat PKP was found to be more mechanically stable than traditional sutures.
    No preview · Article · Jan 2008 · Cornea
  • Penny McAllum · Allan Slomovic

    No preview · Article · Sep 2007 · Canadian Journal of Ophthalmology
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    ABSTRACT: To evaluate visual acuity, topography, and endothelial cell density 1 year after deep lamellar endothelial keratoplasty (DLEK) for endothelial dysfunction. This is a prospective, comparative, interventional case series. Thirty-five eyes of 35 patients who had undergone DLEK with a 5-mm incision and had a minimum of 1-year follow-up were included. Main outcome measures were best spectacle-corrected visual acuity (BSCVA), uncorrected visual acuity (UCVA), astigmatism, topographic regularity and symmetry, and endothelial cell density. : One year postoperatively, BSCVA was 0.33 +/- 0.12 (mean, 20/60; range, 20/40-20/400) compared with 0.15 +/- 0.15 preoperatively (mean, 20/200; range, 20/70-20/800). Six patients did not reach an acceptable visual acuity and were not included in the mean BSCVA, 2 had a primary failure, and the others had preexisting glaucoma or macular disease. Spherical equivalent was -0.04 +/- 1.2 D, refractive astigmatism was 1.76 +/- 1.69 D, surface regularity index was 0.97 +/- 0.54, and surface asymmetry index was 1.25 +/- 0.78 1 year after surgery. Mean endothelial cell count from the donor was 2904 +/- 559 (range, 4694-2111) and 1 year after surgery was 1595 +/- 662 (range, 702-3040), equating to 45% cell loss (range, 15%-77%). DLEK is a newer method to replace the endothelium in patients with Fuchs dystrophy. Results showed minimal astigmatism, good topographic parameters, and acceptable visual acuity. Endothelial cell loss at 1 year was significant.
    No preview · Article · Jul 2007 · Cornea
  • Penny J McAllum · Fani Segev · Sheldon Herzig · David S Rootman
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    ABSTRACT: To describe 2 cases of post-laser in situ keratomileusis (LASIK) ectasia managed with deep anterior lamellar keratoplasty (DALK). Clinical findings, surgical interventions, and outcomes are reported. The surgical technique of DALK is described. Two patients developed progressive loss of vision after LASIK surgery with enhancement procedure(s). Corneal ectasia was diagnosed on the basis of clinical findings, progressive central corneal thinning on pachymetry, and topographical changes with irregular astigmatism and inferior corneal steepening. Both patients underwent uneventful DALK surgery, in which the anterior 80% of the central corneal stroma was replaced by a donor button and sutured in place. The postoperative recovery was uneventful, except for mild interface haze in 1 case, which resolved within 2 weeks of surgery. However, 1 patient underwent additional surgery, including clear lens extraction with intraocular lens placement, astigmatic keratotomies, and photorefractive keratectomy (PRK) to achieve good unaided visual acuity. At last follow-up, at least 2 years after DALK, both patients were satisfied with their vision. Their uncorrected visual acuity (UCVA) was 20/60+ and 20/40- in their operated eyes, improving to 20/40+ and 20/30- with minimal refractive corrections. The grafts and lamellar interfaces were clear. We believe that DALK should be considered as an alternative to penetrating keratoplasty for the surgical management of post-LASIK ectasia.
    No preview · Article · Jun 2007 · Cornea
  • Penny McAllum · David Rootman

    No preview · Article · May 2007 · Clinical and Experimental Ophthalmology
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    ABSTRACT: We report a case of severe bilateral simultaneous Achromobacter xylosoxidans keratitis following penetrating keratoplasty (PKP) in a patient with graft-versus-host disease. The predisposing factors, clinical features, treatment options, and final visual outcome are reviewed. To our knowledge, this is the first report of bilateral A xylosoxidans keratitis following PKP.
    No preview · Article · Jan 2007 · Journal of Cataract and Refractive Surgery
  • Srinivasan S · McAllum P · Poutanen SM · Slomovic AR

    No preview · Article · Jan 2006 · Journal of Cataract and Refractive Surgery

Publication Stats

617 Citations
48.77 Total Impact Points


  • 2007-2012
    • University of Toronto
      • Department of Ophthalmology and Vision Sciences
      Toronto, Ontario, Canada
  • 2007-2008
    • Toronto Western Hospital
      Toronto, Ontario, Canada