Ronald N Gaster

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

Are you Ronald N Gaster?

Claim your profile

Publications (8)20.97 Total impact

  • [Show abstract] [Hide abstract]
    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; · 5.56 Impact Factor
  • International ophthalmology clinics 01/2013; 53(1):79-90.
  • Ronald N Gaster, Amir Pirouzian
    International ophthalmology clinics 01/2013; 53(1):15-26.
  • [Show abstract] [Hide abstract]
    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. · 2.92 Impact Factor
  • [Show abstract] [Hide abstract]
    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. · 1.75 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    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 01/2011; 52(7):4231-8. · 3.43 Impact Factor
  • [Show abstract] [Hide abstract]
    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. · 5.56 Impact Factor
  • Amy Lin, Ronald N Gaster
    [Show abstract] [Hide abstract]
    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. · 1.75 Impact Factor