Dipak N. Parmar

Visual prognostic value of the pattern electroretinogram in chiasmal compression

BACKGROUND/AIMS The visual loss associated with compression of the optic chiasm by pituitary tumours may be transient or permanent, possibly related to the extent of irreversible retrograde degeneration to the retinal ganglion cells. The pattern electroretinogram (PERG) N95 component is thought to rise in relation to retinal ganglion cell function and hence may be a potential prognostic indicator for visual function following decompressive surgery. METHODS The notes and electrodiagnostic records of 72 eyes from 36 patients with chiasmal compression were retrospectively analysed. RESULTS The postoperative change in visual field was found to be associated with the PERG N95:P50 ratio (p=0.01). Improvement in visual field was shown by a greater proportion of eyes with a normal N95:P50 ratio (65%) than with an abnormal ratio (27%). No change in visual field occurred in 26% of the eyes with a normal N95:P50 ratio compared with 67% of those with an abnormal ratio. Only 8% of eyes showed a worsening of visual field following surgery, in similar proportions for eyes with normal and abnormal N95:P50 ratios. There was no significant relationship with visual acuity. CONCLUSION The PERG is a useful visual prognostic indicator in the preoperative assessment of chiasmal compression.

Advances in the Diagnosis and Treatment of Acanthamoeba Keratitis

This paper aims to review the recent literature describing Acanthamoeba keratitis and outline current thoughts on pathogenesis, diagnosis, and treatment as well as currently emerging diagnostic and treatment modalities.

Corneal intrastromal gatifloxacin crystal deposits after penetrating keratoplasty.

Background. An 85-year-old man developed faint crystallike white precipitates in the mid peripheral stroma of his left cornea 3 weeks after undergoing penetrating keratoplasty. The patient had been initially treated with 1% prednisolone acetate ophthalmic suspension and 0.3% gatifloxacin eyedrops to his left eye from the first day postoperatively. Three weeks later, the precipitates were more numerous, larger, and diffuse in distribution. Gatifloxacin was discontinued and substituted with a neomycin–polymixin B–dexamethasone ophthalmic ointment. Methods. A detailed history, physical examination, laboratory workup, and tandem scanning confocal microscopy were performed. Results. Tandem scanning corneal confocal microscopy confirmed the presence of crystals in the cornea. Conclusions. Gatifloxacin, a fourth-generation fluoroquinolone, can cause intrastromal macroscopic crystalline deposits through a compromised corneal epithelium, similar to what has been described for ciprofloxacin, a second-generation fluoroquinolone.

Confocal assessment of the corneal response to intracorneal lens insertion and laser in situ keratomileusis with flap creation using IntraLase

PURPOSE: To assess the response of the cornea to hydrogel intracorneal lens (ICL) insertion or laser in situ keratomileusis (LASIK) with IntraLase (IntraLase Corp.) at the cellular level. SETTING: Department of Ophthalmology, University of Texas Southwestern Medical Center, Dallas, Texas, USA. METHODS: Twenty patients (29 eyes) were evaluated by in vivo confocal microscopy 1 to 6 months postoperatively: 20 eyes had LASIK with flap creation by IntraLase, and 9 eyes had ICL insertion (8 following IntraLase). RESULTS: For LASIK with IntraLase, keratocyte activation and/or interface haze was detected in 8 of 20 eyes. The remaining eyes had interface particles but no cell activation. Keratocyte activation was generally limited to a few cell layers adjacent to the interface. However, 2 patients exhibited multiple layers of activation and increased extracellular matrix (ECM) reflectivity (haze) surrounding the interface by confocal microscopy. Both patients also had clinical haze and photophobia. For ICLs, following insertion, 5 of 9 eyes had activated keratocytes adjacent to the implant surfaces. The largest amount of cell activation and ECM haze detected by confocal microscopy was in 2 patients with significant clinical haze. Structures with an epithelioid morphology were detected on some implant surfaces. Epithelial thickness was 33.3 μm ± 2.3 (SD) in the ICL eyes and 49.2 ± 6.5 μm in the LASIK with IntraLase eyes. CONCLUSIONS: Both LASIK with IntraLase and ICL insertion following IntraLase induced keratocyte activation, which may underlie clinical observations of haze in some patients. Intracorneal lens implant also induced thinning of the overlying corneal epithelium.

Intraocular Lens Opacification following Intracameral Injection of Recombinant Tissue Plasminogen Activator to Treat Inflammatory Membranes after Cataract Surgery

Purpose. To report 7 cases of intraocular lens (IOL) opacification following treatment of postoperative anterior chamber fibrin with recombinant tissue plasminogen activator (rtPA) after cataract surgery. Methods. Retrospective case series of 7 eyes in 7 patients who developed IOL opacification after receiving rtPA for anterior chamber inflammatory membrane formation resulting from phacoemulsification cataract surgery. Three explanted IOLs were investigated with light microscopy, histochemical analysis, scanning electron microscopy, and X-ray spectrometry. Results. All patients underwent uncomplicated cataract surgery and posterior chamber hydrophilic IOL implantation. Anterior chamber inflammatory membranes developed between 1 and 4 weeks of surgery and were treated with intracameral rtPA. IOL opacification was noted between 4 weeks and 6 years after rtPA treatment with reduced visual acuity, and IOL exchange was carried out in 3 patients. Light microscopy evaluation revealed diffuse fine granular deposits on the anterior surface/subsurface of IOL optic that stained positive for calcium salts. Scanning electron microscopy (SEM) and energy-dispersive X-ray spectrometry (EDS) confirmed the presence of calcium and phosphate on the IOL. Conclusions. Intracameral rtPA, though rapidly effective in the treatment of anterior chamber inflammatory membranes following cataract surgery, may be associated with IOL opacification.

Contact Lens-based Expansion and Transplantation of Autologous Epithelial Progenitors for Ocular Surface Reconstruction: Crossover Control

Di Girolamo N, 2009, TRANSPLANTATION, V87, P1571, DOI 10.1097-TP.0b013e3181a4bbf2; Ozbek Z, 2006, CORNEA, V25, P245, DOI 10.1097-01.ico.0000176602.49258.ea; Parmar DN, 2006, AM J OPHTHALMOL, V141, P299, DOI 10.1016-j.ajo.2005.09.008

Management of patients with herpes simplex virus eye disease having cataract surgery in the United Kingdom

&NA; To standardize the management of patients with herpetic eye disease scheduled for cataract surgery, a questionnaire was sent to each fellow of the Royal College of Ophthalmologists registered as a consultant with a subspecialty interest in cornea. Most respondents agreed that disease stability was required before cataract surgery was offered; 62.3% would operate on patients in whom the disease had been quiescent for 3 to 6 months. The decision to prescribe prophylactic antivirals divided the respondents, with 58.8% in favor of starting antiviral treatment. Most respondents (72.46%) did not start topical antiviral treatment. In regard to changing topical steroid use postoperatively, 80.9% would not change their routine regimen. Oral acyclovir was the first line of treatment for 92.5%. The conclusions were that a significant period of inactivity should be considered before cataract surgery is performed in patients with herpes simplex virus eye disease. Oral antiviral prophylaxis is common clinical practice, but no change in routine postoperative steroid use is needed. Financial Disclosure No author has a financial or proprietary interest in any material or method mentioned.

Caution essential in quick-pull technique

Caution essential in quick-pull technique Coelho et al. have described a novel approach to rescuing a peripheral capsulorrhexis tear out during cataract surgery. A discontinuous curvilinear capsulorrhexis can compromise the integrity of the capsular bag, with serious consequences for the rest of the procedure. This technique is a useful addition to the surgical repertoire, but we believe it should be used with caution. This procedure is particularly aggressive, with associated anterior capsule stretch and potential zonular weakening and damage. There is a known relationship between the stretching capacity of the anterior capsule and the zonular fibers, so we would recommend using this new technique as an absolute last resort and totally avoiding it in cases in which the zonule may be compromised, such as denser cataracts of elderly patients, pseudoexfoliation cases, or history of trauma. The demographic and clinical information of the 50 cataract cases performed by Coelho et al. are unknown so it is impossible to know whether the technique was used in any patient with the abovementioned characteristics. Additionally, the authors mention and show in their video that they could not perform Little et al.’s technique or the other rescue techniques because of the poor visualization of the capsule root, which is a problem that could be dealt with using iris hooks. Theauthors also suggest that traineeor inexperienced surgeons may not have sufficient skills to carry out this procedure; however, this cohort of surgeons are perhaps the oneswho have a higher likelihood of capsulorrhexis tear outs. Again, the authors do not provide information regarding how many different surgeons and of what level this technique was performed by. Finally, avoiding peripheral tear out with the use of a heavier cohesive ophthalmic viscosurgical device (OVD) such as Healon GV or a viscoadaptive OVD such as Healon V and greater control is the ultimate goal with efforts directed at prevention of these difficult situations.

Bevel-up versus bevel-down phacoemulsification tip.

phaco and concluded, “. . . we do not recommend emulsifying a cataractous lens with the phaco tip in the bevel-down position.” Unfortunately, this study did not select a tip specifically designed for beveldown phaco. Kim et al. compared 3 tips including the reverse miniflared 30-degree Kelman tip and confirmed the “relative safety of the bevel-down technique” and the advantages of using this tip. I would, however, like to politely correct Kim et al., who state that “the reverse miniflared 30-degree Kelman configuration tip was designed to aid surgeons in positioning their wrist during the bevel-down technique.” Actually, the tip was developed for other reasons as I co-designed this tip with Alcon Laboratories, Inc. (Figure 1). My original thinking was that reducing the curve on the tip to 12 degrees would combine efficient torsional cutting with better phaco aspiration than the 45-degree tip because the curve of the needle would be 50% less extreme. I also reasoned that a beveldown tip could be easily buried in the central cortex at the beginning of the phaco procedure when I prefer to use higher power and vacuum. The cornea is better protected when ultrasound energy is directed away from the endothelium and when the ophthalmic viscosurgical device (OVD) cannot find its way into the tip, remaining undisturbed in the anterior chamber. After a divot or partial-depth groove is made, the bevel is rotated upward, providing an excellent angle for deeper sculpting. The lower vacuum prevents the OVD from being aspirated. The nucleus is divided into hemispheres and chopped, followed by safe removal of the quadrants in the posterior chamber. The bevel faces upward since the slashing motion of the tip should never be perpendicular to the anterior capsule edge. In conclusion, the authors of both articles are to be congratulated for bringing attention to tip design. The surgeon should strive to adopt a specific tip and a surgical technique that ensure safe, gentle, and efficient phacoemulsification.