Ronald N Gaster

University of California, Irvine, Irvine, California, United States

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Publications (17)57.36 Total impact

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    ABSTRACT: Evaluate the usefulness of toric intraocular lens (IOL) implantation during cataract surgery in patients after penetrating keratoplasty (PKP). Retrospective case review. A total of 21 eyes of 16 patients with prior PKP and moderate to high regular astigmatism after full suture removal underwent phacoemulsification and implantation of a single-piece acrylic toric IOL (SN6AT series; Alcon, Fort Worth, TX). Patients underwent comprehensive examinations at standard intervals, including visual acuity, manifest refraction, and corneal topography. Uncorrected distance visual acuity (UDVA) and corrected distance visual acuity (CDVA) expressed as the logarithm of the minimum angle of resolution (logMAR) and manifest refraction astigmatism. From preoperatively to the last visit (mean, 14.7 ± standard deviation 12.8 months), the 21 eyes had significant improvement in UDVA (logMAR, 0.90±0.48 to 0.23±0.25; P = 0.0001) and CDVA (logMAR, 0.31±0.14 to 0.08±0.13; P = 0.0001). A total of 14 of 21 eyes (67%) and 17 of 21 eyes (81%) had UDVA and CDVA of ≥20/30, respectively. Preoperative topographic astigmatism was 4.57±2.05 diopters (D). Postoperative manifest refraction astigmatism was 1.58±1.25 D overall, but lower (0.75±0.54 D) in the T7-T9 subgroup (excluding 1 outlier whose corneal astigmatism doubled after surgery) than in the T4-T6 subgroup (1.88±1.28 D; P = 0.013). A total of 16 of all 21 eyes (76.2%) and 8 of 9 eyes (89%) in the T7-T9 subgroup were within 1 D of postoperative manifest astigmatism as predicted or better. Toric IOLs placed during cataract surgery after PKP and full suture removal can reduce manifest refraction cylinder to predictably low levels with corresponding improvement in UDVA and CDVA in patients with moderate to high regular preoperative topographic astigmatism. The author(s) have no proprietary or commercial interest in any materials discussed in this article.
    Ophthalmology 12/2013; DOI:10.1016/j.ophtha.2013.10.011 · 6.17 Impact Factor
  • Ronald N Gaster, Amir Pirouzian
    International ophthalmology clinics 01/2013; 53(1):15-26. DOI:10.1097/IIO.0b013e3182713487
  • International ophthalmology clinics 01/2013; 53(1):79-90. DOI:10.1097/IIO.0b013e3182773ab4
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    ABSTRACT: This paper will compare the visual outcomes of two different penetrating keratoplasty (PKP) techniques in patients with keratoconus. It is a retrospective comparative surgical case series of 116 keratoconus patients (137 eyes) who had PKP at the Cornea Eye Institute, Beverly Hills, California, USA. 56 keratoconus patients (66 eyes) underwent femtosecond laser-enabled keratoplasty (FLEK) with a zig-zag incision configuration. Their visual parameters were compared with those of 60 patients (71 eyes) who had traditional blade mechanical trephination PKP. The range of follow-up was between 3 and 6 months. The main outcome measures included uncorrected visual acuity and best spectacle-corrected visual acuity (BSCVA), manifest refractive spherical equivalent and topographically determined astigmatism. BSCVA was significantly better as early as 3 months postoperatively (p=0.001) in the FLEK group. Visual recovery to 20/40 after 3 months was significantly better in the FLEK group (p<0.001). Topographic astigmatism was lower in the FLEK group, but the difference between the two groups reached significance only at 3 months of follow-up (p=0.001). Postoperative complications noted were not different between the two groups. Faster visual recovery and better long-term outcomes were observed in keratoconus patients who had FLEK compared with those who had the mechanical PKP procedure with 6 months of postoperative follow-up.
    The British journal of ophthalmology 07/2012; 96(9):1195-9. DOI:10.1136/bjophthalmol-2012-301662 · 2.81 Impact Factor
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    ABSTRACT: To evaluate and compare corneal higher-order aberrations (HOAs) after Descemet stripping automated endothelial keratoplasty (DSAEK), femtosecond laser-assisted penetrating keratoplasty (FLAK), and conventional penetrating keratoplasty (PKP). A retrospective comparison of consecutive surgical series of 67 eyes of 59 patients between 1.5 and 19 months after corneal transplant surgery (22, 34, and 11 corneas underwent DSAEK, FLAK, and PKP, respectively, by a single surgeon). The main outcome measures were anterior and posterior corneal surface HOAs (Zernike polynomials, third to eighth order) determined with Scheimpflug photography at 4.0- and 6.0-mm optical zones and best spectacle-corrected visual acuity (BSCVA) (logarithm of the minimum angle of resolution equivalents). DSAEK had fewer total anterior HOAs compared with FLAK [P = 5.27 × 10(-5) (4.0 mm) and P = 1.02 × 10(-5) (6.0 mm)] and PKP [P = 1.82 × 10(-4) (4.0 mm) and P = 1.56 × 10(-4) (6.0 mm)] but greater total posterior HOAs than FLAK [P = 0.001 (4.0 mm) and P = 0.007 (6.0 mm)] and PKP [at 4.0-mm optical zone (P = 0.047)]. FLAK had fewer total anterior and posterior HOAs than PKP, but differences were not statistically significant. DSAEK grafts exhibited statistically significantly greater posterior HOAs than either type of PKP. The magnitude of anterior and posterior HOAs weakly correlated with BSCVA. DSAEK induces fewer anterior surface HOAs but greater posterior surface HOAs than FLAK or PKP. Differences between FLAK and PKP are not statistically significant. Anterior and posterior HOAs correlate weakly with poorer visual outcome and likely contribute to decreased BSCVA after keratoplasty.
    Cornea 09/2011; 31(1):6-13. DOI:10.1097/ICO.0b013e3182151df2 · 2.36 Impact Factor
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    ABSTRACT: Corneal collagen cross-linking (CXL) by the use of riboflavin and ultraviolet-A light (UVA) is a promising and novel treatment for keratoconus and other ectatic disorders. Since CXL results in enhanced corneal stiffness, this study tested the hypothesis that CXL-induced stiffening would be proportional to the collagen autofluorescence intensity measured with nonlinear optical (NLO) microscopy. Rabbit eyes (n = 50) were separated into five groups including: (1) epithelium intact; (2) epithelium removed; (3) epithelium removed and soaked in riboflavin, (4) epithelium removed and soaked in riboflavin, with 15 minutes of UVA exposure; and (5) epithelium removed and soaked in riboflavin, with 30 minutes of UVA exposure. Corneal stiffness was quantified by measuring the force required to displace the cornea 500 μm. Corneas were then fixed in paraformaldehyde and sectioned, and the collagen autofluorescence over the 400- to 450-nm spectrum was recorded. There was no significant difference in corneal stiffness among the three control groups. Corneal stiffness was significantly and dose dependently increased after UVA (P < 0.0005). Autofluorescence was detected only within the anterior stroma of the UVA-treated groups, with no significant difference in the depth of autofluorescence between different UVA exposure levels. The signal intensity was also significantly increased with longer UVA exposure (P < 0.001). Comparing corneal stiffness with autofluorescence intensity revealed a significant correlation between these values (R(2) = 0.654; P < 0.0001). The results of this study indicate a significant correlation between corneal stiffening and the intensity of collagen autofluorescence after CXL. This finding suggests that the efficacy of CXL in patients could be monitored by assessing collagen autofluorescence.
    Investigative ophthalmology & visual science 06/2011; 52(7):4231-8. DOI:10.1167/iovs.10-7105 · 3.66 Impact Factor
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    ABSTRACT: To report the results of penetrating keratoplasty (PK) in active Acanthamoeba keratitis (AK). Nine patients with deep stromal infiltrates because of AK were treated with intensive antiamoebic medical therapy followed by PK during the acute infectious phase because of poor clinical response or poor compliance. Antiamoebic therapy was tapered after PK. Visual acuity ranged from 20/15 to 20/50 after an average of 17 months after PK with no signs of recurrences. Patients had rapid resolution of symptoms. PK is a viable option for active AK not responding to maximum medical treatment.
    Cornea 09/2010; 29(9):1000-4. DOI:10.1097/ICO.0b013e3181cc79a1 · 2.36 Impact Factor
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    ABSTRACT: To evaluate visual outcomes and astigmatism in patients who underwent penetrating keratoplasty (PK) with 2 different incision techniques. Retrospective comparison of a consecutive surgical series. Fifty-seven consecutive patients who underwent PK at the University of California, Irvine, academic referral practice. A comparison of 49 eyes of 43 patients that underwent femtosecond laser zig-zag incision pattern PK versus 17 eyes of 14 patients that underwent conventional Barron suction trephination PK performed contemporaneously. All PKs were closed with an identical, 24-bite running nylon suture technique. Topographically determined astigmatism, best spectacle-corrected visual acuity (BSCVA), and recovery of full visual potential. The postoperative follow-up ranged from 1 to 12 months. There was a significant difference in average astigmatism between the groups at postoperative month 1 (P = 0.013) and 3 (P = 0.018). By month 3, the average astigmatism was 3 diopters (D) in the zig-zag group and 4.46 D in the conventional group. Of the patients with normal macular and optic nerve function (n(ZZ) = 32; n(con) = 14), a significant difference in BSCVA was seen at month 1 (P = 0.0003) and month 3 (P = 0.006) with 81% of the zig-zag group versus 45% of the conventional group achieving BSCVA of > or =20/40 by month 3 (P = 0.03). The femtosecond laser generated zig-zag-shaped incision results in a more rapid recovery of BSCVA and induces less astigmatism compared with conventional blade trephination PK. Proprietary commercial disclosure may be found after the references.
    Ophthalmology 07/2009; 116(9):1638-43. DOI:10.1016/j.ophtha.2009.05.003 · 6.17 Impact Factor
  • Amy Lin, Ronald N Gaster
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    ABSTRACT: We present a case of suction loss during a femtosecond laser incision for penetrating keratoplasty in the host cornea. This case illustrates a technique for completing the procedure with no further complications.
    Cornea 05/2009; 28(3):362-4. DOI:10.1097/ICO.0b013e31818c2b0d · 2.36 Impact Factor
  • Ronald N Gaster, Joseph F Collins
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    ABSTRACT: To compare at two, three, and four years after surgery the effect on best-corrected visual acuity (BCVA) of anterior chamber (AC) intraocular lenses (IOLs) and posterior chamber (PC) IOLs implanted after vitreous presentation (VP) during extracapsular cataract extraction in patients having sufficient capsular support for a nonsutured PC IOL. The study was a randomized prospective, long-term, clinical trial. Patients at 19 Department of Veterans Affairs Medical Centers having VP during cataract surgery with sufficient capsular support were randomized to receive either a PC IOL (230 patients) or an AC IOL (208 patients). Patients having insufficient capsular support (ICS; 143 patients) and a 5% random sample of nonvitreous presentation patients (NVP; 521 patients) were prospectively followed in the same fashion. There was no significant difference on the major outcome measure of BCVA of 20/40 or better between the PC IOL and AC IOL groups at two (88.7% vs 82.2%; P = .23), three (82.5% vs 91.8%; P = .18), and four (88.6% vs 92.6%; P = .69) years of follow-up. The ICS patients had significantly worse (P < .0083) or a trend to be worse (P < .05) BCVA of 20/40 or better than the other three groups at two and four years. The significant difference that the PC IOL was better than the AC IOL on the major outcome measure at one year reported previously was not maintained in later years. The poor results for ICS patients reported previously at one year continue at two and four years.
    American Journal of Ophthalmology 08/2007; 144(2):186-194. DOI:10.1016/j.ajo.2007.04.023 · 4.02 Impact Factor
  • Raja Narayanan, Ronald N Gaster, M Cristina Kenney
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    ABSTRACT: To review the pathological mechanisms and treatments for pseudophakic corneal edema (PCE), one of the most common indications for penetrating keratoplasty. The literature was examined for the molecular biology associated with PCE and for the surgical and medical treatments for this disorder. The incidence of PCE has recently been decreasing because of improved surgical instrumentation, including improvements in intraocular lens designs that cause less trauma to the corneal endothelium. Extracellular matrix and growth factor abnormalities occur in PCE corneas and recently, the role of aquaporins, which are involved in the regulation of fluid movement across cells, has been investigated. Although newer treatment options have been suggested, penetrating keratoplasty still remains the most definitive treatment and has the highest success rate.
    Cornea 11/2006; 25(9):993-1004. DOI:10.1097/01.ico.0000214225.98366.83 · 2.36 Impact Factor
  • Joseph F Collins, Ronald N Gaster, William F Krol
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    ABSTRACT: The study's purpose was to determine the effect that lack of capsular support for a nonsutured posterior chamber (PC) intraocular lens IOL has on 1-year postoperative vision in patients suffering vitreous presentation (VP) during extracapsular cataract surgery. The study was a prospective, long-term clinical trial. The study was conducted at 19 Department of Veterans Affairs medical centers. Patients having VP during cataract surgery with sufficient capsular support for a nonsutured PC IOL were randomized to receive either a PC IOL (230 patients) or an anterior chamber (AC) IOL (208 patients). Patients having insufficient capsular support (ICS) for a nonsutured PC IOL (143 patients) were prospectively followed in the same fashion. Best-corrected visual acuity (BCVA) at 1 year was obtained by a masked, certified examiner. The ICS group had considerably fewer patients with BCVA of 20/40 or better at 1 year (P < .0001) than the randomized PC IOL group (66.7% vs 91.1%) with a trend (P = .04) for having fewer patients than the randomized AC IOL group (66.7% vs 79.0%). The ICS group had significantly poorer rating of vision at 1 year by study raters, and the patients themselves than either of the randomized VP groups. The lack of capsular support for the placement of a nonsutured PC IOL after VP during extracapsular cataract surgery or the severity of the complication of VP associated with lack of capsular support would appear to cause visual problems beyond that related to the type of intraocular lens implanted.
    American Journal of Ophthalmology 01/2006; 141(1):71-78. DOI:10.1016/j.ajo.2005.08.042 · 4.02 Impact Factor
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    ABSTRACT: The purpose of this study was to determine the effects that vitreous presentation (VP) during extracapsular cataract surgery has on patients' 1-year postoperative vision. The study was a prospective, long-term, clinical trial. The study took place at 19 Department of Veterans Affairs medical centers. Patients having VP during cataract surgery and receiving a posterior chamber (PC) intraocular lens (IOL) (230 patients) were prospectively compared with a 5% random sample of nonvitreous presentation (NVP) cataract surgery patients (521 patients). Best-corrected visual acuity (BCVA) at 1 year was obtained by a masked, certified examiner. There was no statistical difference (P = .089) between the VP patients receiving PC IOL and the NVP patients in percentage of patients having BCVA of 20/40 or better at 1 year (91.1% vs 94.9%). There were significantly more PC IOL VP patients than NVP patients with BCVA of 20/50 or worse at some time during the first postoperative year (21.6% vs 10.9%; P = .0003), significantly fewer with BCVA of 20/20 or better at 1 year (27.8% vs 38.8%; P = .013), and significantly more with cystoid macular edema (11.5% vs 3.6%; P = .0002), retinal detachment (4.3% vs 0.2%; P = .0002), and uveitis (3.4% vs 0.6%; P = .012). The NVP patients rated their vision as very good or excellent significantly more often than the VP patients (71% vs 58%; P = .025). Vitreous presentation during extracapsular cataract surgery leads to somewhat worse overall outcomes in patients, although the majority of patients with VP do reasonably well.
    American Journal of Ophthalmology 11/2004; 138(4):536-42. DOI:10.1016/j.ajo.2004.04.050 · 4.02 Impact Factor
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    ABSTRACT: Corneas with edema-related diseases lose transparency, which causes significant vision loss. This study analyzed seven aquaporins (AQPs) in normal corneas, pseudophakic/aphakic bullous keratopathy (PBK/ABK) corneas, Fuchs' dystrophy corneas, keratoconus corneas, post-cataract surgery (PCS) corneas, and normal organ-cultured corneas. RNA levels for AQP1, AQP4, and beta2-microglobulin were measured by RT-PCR. AQP1 antibody localized to stromal cells of all corneas. PBK/ABK and Fuchs' dystrophy corneas had decreased endothelial cell staining compared with normal. AQP1 mRNA was found in whole corneas and cultured stromal fibroblasts but not in isolated epithelial cells. AQP3 staining was found in basal epithelial cells of the normal, Fuchs' dystrophy, and keratoconus corneas but throughout the entire epithelium of PBK/ABK corneas. AQP4 antibody localized to endothelial cells of all corneas and in stromal cells of PBK/ABK corneas. AQP4 mRNA was identified in whole human corneas. AQP5 was found in epithelial cells of all corneas. AQP0, AQP2, and AQP9 were not found in any corneas. Normal AQP distributions were found in PCS and organ-cultured corneas, although they showed signs of swelling. Our study demonstrates that AQP abnormalities are found in PBK/ABK corneas (decreased AQP1, increased AQP3 and AQP4) and Fuchs' dystrophy corneas (decreased AQP1). Although both have vision-disrupting corneal edema, the mechanisms of fluid accumulation may be different in each disease.
    Journal of Histochemistry and Cytochemistry 11/2004; 52(10):1341-50. DOI:10.1369/jhc.4A6385.2004 · 2.40 Impact Factor
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    ABSTRACT: To report a patient with severe corneal and conjunctival toxicity from long-term, habitual use of hydrogen peroxide as an eye wash. Observational case report. INTERVENTION AND TESTING: Serial examinations of the cornea, conjunctiva, and ocular adnexa were done. Penetrating keratoplasty with amniotic membrane transplantation was performed. Ocular inflammation, pain, and visual acuity outcome. Bilateral corneal and conjunctival inflammation and scarring mimicking ocular-cicatricial pemphigoid were noted. Formation of a descemetocele after starting treatment with low-dose topical steroids required emergent penetrating keratoplasty with amniotic membrane transplantation. This is the first reported case of ocular surface toxicity in a patient after deliberate chronic use of high-dose hydrogen peroxide. It highlights the value of obtaining a thorough medical and social history and the importance of direct questioning about the use of any medications or agents on the eyes before making a diagnosis or initiating therapy.
    Ophthalmology 09/2004; 111(8):1546-9. DOI:10.1016/j.ophtha.2004.01.027 · 6.17 Impact Factor
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    ABSTRACT: In ophthalmic surgery, corneal transplantation (penetrating keratoplasty) may be employed when the clarity of the cornea has been significantly compromised by conditions such as scarring, edema, and variable corneal thickness. Irregularities in corneal curvature can occur postoperatively. This astigmatism is of concern, because it can impair visual acuity despite an otherwise good surgical result. Different suturing techniques have been developed to minimize astigmatism. The purpose of this study was to evaluate an opposing 10-0 nylon double running suture technique for penetrating keratoplasty. A retrospective study was undertaken of 91 records of patients who underwent penetrating keratoplasty performed by one surgeon (RNG). This represents 54.8% of 166 consecutive cases. Every eye with an opposing double running suture and a 1- to 3-month postsuture removal followup was selected and evaluated for best corrected visual acuity and astigmatism, excluding eyes that developed graft failure or corneal ulcer or that had lack of adequate followup. The cases were divided into five groups by preoperative diagnosis: pseudophakic bullous keratopathy (n = 43), aphakic bullous keratopathy (n = 5), keratoconus (n = 17), Fuchs dystrophy (n = 12), and miscellaneous (n = 14). The mean standard followup period was 13.7 months after penetrating keratoplasty. Thirty percent of the eyes had an extensive followup, with a mean of 33 months after penetrating keratoplasty. Eighty-two percent of the patients had a significant improvement of their visual acuity postoperatively, defined by a five-line improvement of best corrected visual acuity or a best corrected visual acuity of 20/40 or better. The mean astigmatic keratometric reading was 3.98 diopters, with a manifest refraction cylinder of 3.42 diopters at the 1- to 3-month postsuture removal visit. This study also shows that there is no statistically significant change in keratometric astigmatism or manifest refraction cylinder from the 1- to 3-month postsuture removal measurements to the more extensive followup of 18 to 66 months after penetrating keratoplasty (p > 0.10). This suture technique allows for excellent longterm stability of the wound with visual and astigmatic results that are comparable to those of previous studies. The use of the opposing double running suture is a viable alternative to some of the other widely used techniques and may be considered more stable and secure.
    Journal of the American College of Surgeons 12/2003; 197(6):991-9. DOI:10.1016/j.jamcollsurg.2003.07.016 · 4.45 Impact Factor
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    ABSTRACT: To compare the efficacy and safety of anterior chamber (AC) intraocular lenses (IOLs) and posterior chamber (PC) IOLs implanted after vitreous presentation during extracapsular cataract extraction (ECCE). The study was a prospective, long-term, randomized clinical trial conducted at 19 Department of Veterans Affairs medical centers across the United States. There were 438 eyes (438 patients) that met preliminary eligibility criteria, suffered vitreous presentation during ECCE (phacoemulsification or classical extracapsular technique), and had sufficient capsular support for a PC IOL without sutures after anterior vitrectomy randomized to either a PC IOL (230 patients) or an AC IOL (208 patients). Patients were examined at 3, 6, and 12 months post-surgery and yearly thereafter. Minimum follow-up was 1 year. The primary outcome measure of best-corrected visual acuity at 1 year was obtained by a masked certified examiner. More PC IOL patients (91%) achieved visual acuity of 20/40 or better at 1 year than AC IOL patients (79%), a highly significant difference (P =.003). There was no significant difference between the two groups for patient's rating of vision or adverse events. Over 84% of the PC IOL patients and over 77% of the AC IOL patients rated their vision as good or better at 1 year as opposed to only 7% giving such ratings before surgery. For at least one rating period during the first year, 13.2% of the combined study patients had cystoid macular edema, 8.5% had posterior capsule opacification, 5.7% had glaucoma, and 3.7% had retinal detachment. In the presence of sufficient capsular support, a PC IOL should be implanted after vitreous presentation during ECCE.
    American Journal of Ophthalmology 08/2003; 136(1):1-9. DOI:10.1016/S0002-9394(02)01924-4 · 4.02 Impact Factor