Modified technique of haptic externalization for scleral fixation of dislocated posterior chamber lens implants.

PURPOSE: To describe a modified technique of haptic externalization during repositioning of dislocated posterior chamber lens implants, which facilitates placement of scleral fixation sutures around the haptic for implant stabilization. METHODS: We describe a technique of repositioning a dislocated posterior chamber implant with scleral fixation sutures, which uses a small, clear corneal incision for externalization of the haptic. After a loop of 10-0 Prolene suture (Ethicon, Inc., Somerville, New Jersey) is placed around the externalized haptic, the sutures are retrieved through a sclerotomy 1.0 mm posterior to the limbus. The haptic is reimplanted into the ciliary sulcus. A separate scleral fixation bite closes the sclerotomy, and it is tied to the 10-0 Prolene sutures looped around the haptic. RESULTS: The dislocated implant was stable and fixated in good position 5 months after surgery using this technique. CONCLUSION: This externalization technique minimizes the extensive intraocular manipulations necessary to create a suture loop around a haptic of a dislocated implant. The clear corneal incision allows for clear visualization during externalization of the haptic.

The Micro-Reflux Test: a new test to evaluate nasolacrimal duct obstruction.

OBJECTIVE: The authors describe a new and simple procedure, the Micro-Reflux Test (MRT), to screen for primary acquired nasolacrimal duct obstruction (PANDO). This study sought to determine the reliability of this new test in the diagnosis of complete nasolacrimal duct obstruction. DESIGN: A nonrandomized, prospective, self-controlled, comparative case series. PARTICIPANTS: Two hundred eyes of 100 patients with documented unilateral complete PANDO were examined. INTERVENTION: The MRT was performed by a masked examiner on both eyes of each patient. Two drops of 0.25% sodium fluorescein dye were instilled in the inferior cul-de-sac and the patient made to blink five times to activate the lacrimal pump mechanism. Excess fluorescein dye was blotted away using tissue paper. The patient was positioned at the slit lamp, and observation of the inferior punctum with the cobalt blue filter was done using 5x magnification. The tissue overlying the lacrimal sac was massaged in a counterclockwise direction with moderate pressure using the index finger. The test was considered positive if there was continued observed reflux of fluorescein-stained tears from the inferior punctum after the initial counterclockwise massage to empty the inferior canaliculus. The validity of the MRT was measured by sensitivity and specificity as well as positive- and negative-predictive values. MAIN OUTCOME MEASURE: The MRT was considered positive if there was continued reflux of fluorescein-stained tears from the inferior punctum after the initial digital massage to empty the dye from the inferior canaliculus. RESULTS: The MRT used for the evaluation of complete PANDO has a sensitivity of 97% and a specificity of 95%. It has a positive-predictive value of 95% and a negative-predictive value of 97%. CONCLUSION: The MRT is a reliable screening test for presence of complete nasolacrimal duct obstruction.

Surgical removal of extensive peripapillary choroidal neovascularization associated with presumed ocular histoplasmosis syndrome.

OBJECTIVE: This study aimed to report the visual outcome of surgical removal of extensive peripapillary choroidal neovascularization (CNV) due to presumed ocular histoplasmosis syndrome (POHS). DESIGN: Retrospective review of the records of all patients seen at the Barnes Retina Institute who underwent surgical removal of extensive peripapillary CNV associated with POHS and who had at least 12 months of follow-up. PARTICIPANTS: Seventeen consecutive eyes (in 14 patients) undergoing surgical removal of extensive peripapillary CNV associated with POHS were studied. INTERVENTION: Pars plana vitrectomy and surgical removal of CNV were performed. MAIN OUTCOME MEASUREMENTS: Best-corrected Snellen visual acuity, funduscopic examination, and intravenous fluorescein angiography were obtained before surgery and at regular intervals after surgery. RESULTS: In 14 of 17 eyes, the peripapillary CNV was subfoveal, and in 3 eyes, it was extrafoveal. All three eyes with extrafoveal CNV were not eligible for laser treatment according to Macular Photocoagulation Study guidelines because treatment would have spared less than 1.5 contiguous clock-hours of retina temporal to the optic disc. Follow-up ranged from 17 to 57 months, with a median of 32 months. In eyes with subfoveal CNV, best-corrected preoperative Snellen visual acuity ranged from 20/25 to counting fingers at 2 feet with a median of 20/200, and best-corrected final Snellen visual acuity ranged from 20/25 to 20/200 with a median of 20/40. In 7 (50%) of 14 eyes, a final Snellen acuity of 20/40 or better was achieved, and in all cases except 1, visual acuity improved or did not change with surgery. In the three eyes with extrafoveal CNV, best-corrected preoperative Snellen visual acuity ranged from 20/20 to 20/400 with a median of 20/200, and best-corrected final Snellen visual acuity was 20/20 in all cases. In addition, visual acuity improved with surgery. CONCLUSIONS: The data from this small retrospective study suggest that surgical removal may provide visual benefit in selected cases of extensive peripapillary CNV due to POHS.

Efficacy of anterior chamber paracentesis and Carbogen in treating acute nonarteritic central retinal artery occlusion.

PURPOSE: To determine whether anterior chamber paracentesis and Carbogen inhalation therapy (95% oxygen, 5% carbon dioxide) produce a significant difference in final visual acuity in eyes with acute nonarteritic central retinal artery occlusion (CRAO), compared with untreated eyes. METHODS: In this retrospective study, the records of 89 consecutive patients seen at the Retina Vascular Unit of Wills Eye Hospital with acute CRAO who received either both anterior chamber paracentesis and Carbogen therapy, or neither anterior chamber paracentesis or Carbogen therapy, were reviewed. Forty patients were treated with both therapies, whereas 49 received neither modality. Visual acuities before treatment and at subsequent follow-up visits were measured. All patients seen within 24 hours of the onset of symptoms were treated, whereas most of those seen after 24 hours were not treated. RESULTS: Stratified Wilcoxon analysis showed no statistically significant difference between the treated and untreated groups (P = 0.87) after adjusting for initial vision. A posthoc power analysis for the difference between two proportions showed that the study had adequate power (0.80) to detect a difference of the proportion of improved patients of 10% versus 25% between that treated and untreated groups. CONCLUSION: The data suggest that anterior chamber paracentesis and Carbogen therapy offer little benefit for treating acute nonarteritic CRAO.

A quantitative animal model of traumatic iridodialysis.

The impact velocities and kinetic energies necessary to create a particular form of ocular injury, traumatic iridodialysis, were quantitatively studied by experimentally traumatizing enucleate porcine eyes. Thicknesses and tensile strengths of porcine and human iris tissue were measured in order to allow for predictions of human results to be made from the animal model. Application of blunt trauma at an impact angle of 30-35 degrees with respect to the iris plane with striking of the eye at the corneolimbal junction was found to optimize tearing of the iris from the root. Using this vector, the minimum velocity for the creation of an iridodialysis at least 6 mm in length in the human eye is predicted to be 14 m/sec for impact with a projectile of 13.4 g with a 6 mm diameter tip.

An optical model to describe image contrast with bifocal intraocular lenses.

We attempted to quantify the decrease in contrast associated with the concentric-style bifocal intraocular lens by using a model eye and bifocal intraocular lens, with a model unifocal intraocular lens as a control. When imaging near objects, pupils smaller than 2.5 mm produced image contrast of 100% of the control; larger pupils degraded contrast to 25% for a 6-mm pupil. For distant objects, pupils smaller than 2.5 mm produced image contrast of 70% to 95% because of the pinhole effect; larger pupils engaged the distance portion of the intraocular lens and maintain 80% contrast on average. Thus, the bifocal intraocular lens produced image contrast greater than 70% in all situations tested, except when imaging near objects with a pupil larger than 3.5 mm. The data suggest that image contrast is highly dependent on pupil size and object distance.

The optical quality of the peripheral cornea.

The cornea can be considered to be an organ divided into a central and peripheral zone. Although the central cornea is responsible for producing a sharp retinal image, our experiments suggest that areas of isolated peripheral cornea can produce retinal images compatible to 20/30 visual acuity.

The role of the limbal cornea in vision.

The eagle retina is bifoveal. The temporal fovea, which can resolve targets subtending half a minute or less must depend upon its peripheral cornea for such sharp resolution. Our studies showed the eagle cornea to be thinner, scatter less light and be more spherical than the human cornea. Further experimental studies determined the resolving power of the human peripheral cornea. Using, normal subjects, pinholes placed at the edge 8 mm dilated pupils yielded 20/30 visual acuity and normal contrast sensitivity measurements. Thus it is recommended that optical iridectomy be considered, in appropriate cases of corneal blindness with patches of clear peripheral cornea when no donor corneal material is available.