Daniele Giammaria

Comparison of Optical Low Coherence Reflectometry and Ultrasound Pachymetry in the Measurement of Central Corneal Thickness Before and After Photorefractive Keratectomy

PURPOSE To compare an ultrasound pachymeter with an optical low coherence reflectometry (OLCR) pachymeter for measuring pre- and postoperative central corneal thickness of patients undergoing photorefractive keratectomy (PRK). METHODS In a prospective, noncomparative, interventional study, 48 myopic eyes (mean manifest refractive spherical equivalent: -4.93 +/- 2.93 diopters [D]) of 30 healthy patients underwent PRK. Pre- and postoperative central corneal thickness was measured by two examiners (E1, E2) with an ultrasound pachymeter and an OLCR pachymeter. Agreement and inter-rater repeatability were determined using the comparison method described by Bland and Altman. RESULTS The limits of agreement between the two devices ranged from 17.8 microm (E1) to 20.5 microm (E2) preoperatively and from 22.4 microm (E1) to 16.9 microm (E2) postoperatively. The coefficient of inter-rater repeatability ranged from 9.1 microm (ultrasound pachymeter) to 5.4 microm (OLCR pachymeter) preoperatively and from 7.1 microm (ultrasound pachymeter) to 4.7 microm (OLCR pachymeter) postoperatively. CONCLUSIONS The OLCR pachymeter seems to show better pre- and postoperative repeatability compared to the ultrasound pachymeter. The agreement between the two devices should be considered acceptable for clinical practice. Photorefractive keratectomy did not affect the postoperative agreement and repeatability of the pachymeters.

Comparison of macular thickness measurements between time-domain and spectral-domain optical coherence tomographies in eyes with and without macular abnormalities.

Purpose: To compare Stratus time-domain optical coherence tomography (OCT) with Cirrus spectral-domain HD-OCT for measuring macular thickness in eyes with and without macular abnormalities. Methods: Seventy-five eyes of 48 patients were included in the study. Forty-one eyes of 29 patients had a normal macular thickness, and 34 eyes of 26 patients had an abnormal macular thickness. Macular scans were performed by 2 examiners (E1 and E2) with both OCTs. The agreement between the two OCT systems and interrater repeatability of each OCT system were determined using the Bland-Altman method. Results: Mean agreement between the 2 OCTs as 1.96 × standard deviation of the mean difference between the measurements of central macular subfield was 21 μm in normal eyes and 36.8 μm in abnormal eyes. In five macular subfields, the agreement was significantly better in normal eyes. Cirrus HD-OCT repeatability was significantly better than Stratus in five macular subfields in normal eyes and in six macular subfields in abnormal eyes. The repeatability was significantly better in normal eyes in five macular subfields for Stratus and in three macular subfields for Cirrus HD-OCT. Conclusion: The agreement between the two OCTs is low and varies in each macular subfield. Cirrus HD-OCT has shown a better repeatability than Stratus OCT, especially when measuring eyes with a thickened macula.

Corneal wound healing after laser vision correction

Any trauma can trigger a cascade of responses in tissues, with the purpose of safeguarding the integrity of the organ affected by the trauma and of preventing possible damage to nearby organs. Subsequently, the body tries to restore the function of the organ affected. The introduction of the excimer laser for keratorefractive surgery has changed the treatment landscape for correcting refractive errors, such as myopia, hyperopia, and astigmatism. In recent years, with the increased understanding of the basic science of refractive errors, higher-order aberrations, biomechanics, and the biology of corneal wound healing, a reduction in the surgical complications of keratorefractive surgery has been achieved. The understanding of the cascade of events involved in the corneal wound healing process and the examination of how corneal wound healing influences corneal biomechanics and optics are crucial to improving the efficacy and safety of laser vision correction.

Necrotic uveal melanoma with orbital inflammation.

Purpose Extraocular extension of uveal melanoma can be accompanied by proptosis and signs of orbital inflammation but this clinical presentation is an uncommon feature if the tumor is solely intraocular. Methods Case report. Results The authors describe a patient with a medium-sized necrotic uveal melanoma, without extraocular spread, presenting with the clinical picture of orbital cellulitis. Conclusions The ophthalmologist needs to be aware of this uncommon presentation of uveal melanoma, and not assume the presence of proptosis and orbital inflammation as signs of extraocular extension.

Under-air staining of the anterior capsule using Trypan blue with a 30 G needle

The original technique of staining the anterior capsule of the lens with Trypan blue involves the injection of an air bubble in the anterior chamber. A drawback of this technique is the possible instability of the anterior chamber caused by the sudden exit of air when the dye is injected with the cannula through the side-port incision. Other staining techniques that use viscoelastic substances to increase the stability of the anterior chamber and to dose the injected dye have been described. The authors present an under-air staining technique of the anterior capsule using one drop of Trypan blue injected with a 30 G needle through the peripheral cornea. This procedure prevents the air bubble from escaping the anterior chamber and allows fast and selective staining of the capsule.

Anti–vascular endothelial growth factor activity in the bevacizumab and triamcinolone acetonide combination for intravitreal use

Purpose To find out if the combination for intravitreal use of the antibody bevacizumab (AvastinTM; Genentech, Inc., San Francisco, CA) and triamcinolone acetonide (TA) (Kenacort®; Bristol-Myers Squibb, Anagni, Italy) could affect over time the anti–vascular endothelial growth factor (VEGF) activity of bevacizumab. Methods Two different combined preparations were obtained, drawing up together 1.25 mg/0.05 mL of bevacizumab and 2 mg/0.05 mL (B+TA2mg) or 4 mg/0.05 mL (B+TA4mg) of TA into insulin syringes with 29-G needle. Control preparations were obtained with bevacizumab and an injectable solution (B). The syringes were stored refrigerated at 4°C. The bevacizumab concentration was measured, through its binding to VEGF-165 isoform, at 48 hours and at 1 week. Results No preparations showed statistically significant changes in bevacizumab concentration with time (p=0.74 for B+T2mg, p=0.92 for B+T4mg, p=0.57 for B). The B+TA2mg preparations showed a larger percentage of degradation of bevacizumab than the B+TA4mg preparations (28.4% versus 17.6% at 48 hours; 26.4% versus 18% at 1 week). The B control preparations showed the lowest drug degradation: 9.6% at 48 hours and 14.8% at 1 week. Conclusions After storage at 4°C for 48 hours and 1 week, the combined preparations showed a larger reduction in bevacizumab concentration than the control preparations. No significant change was observed with the length of storage. The preparations obtained mixing 4 mg/0.05 mL of TA and 1.25 mg/0.05 mL of bevacizumab maintained the highest anti-VEGF activity over time. (Eur J Ophthalmol 2009; 19: 842–7)

Corneal Wound Healing and Laser Refractive Surgery

The introduction of the excimer laser for keratorefractive surgery has changed the treatment landscape for correcting refractive errors, such as myopia, hyperopia, and astigmatism. Laser refractive techniques act on the cornea altering its optical properties, and their results are closely related to tissue healing. In recent years, with the increased understanding of the basic science of refractive errors, higher-order aberrations, biomechanics, and the biology of corneal wound healing, a reduction in the surgical complications of keratorefractive surgery has been achieved. The understanding of the cascade of events involved in the corneal wound healing process and the examination of how corneal wound healing influences corneal biomechanics and optics are crucial to improving the efficacy and safety of laser vision correction.