Effect of pharmacological dilation and constriction of pupil on corneal topography.

A prospective study was undertaken to investigate the effect of pharmacological pupillary dilation and constriction on corneal topography. Corneal topography was performed using the EyeSys system on 28 normal subjects before and after pupil dilation, constriction, and then with the pupil intact (no medication). Our results show that both flattening and steepening of the corneal curvature were found in all three examination periods. The numbers of corneas with flattening and steepening in each examination period were compared and found not to be statistically different. Mean change of corneal flattening was compared with mean change of corneal steepening in each examination period and again no significant difference was found. These results indicate that the slight changes in corneal power and radius following pharmacological pupillary dilation or constriction may be due to either the inability to repeat by the subjects, or error by observers or instrument.

The 20-prism-dioptre base-out test: an indicator of peripheral binocularity.

OBJECTIVE: To assess the ability of the 20-prism-dioptre base-out test to detect the presence of peripheral fusion in children too young to undergo formal sensory testing. DESIGN: Case series. SETTING: Pediatric ophthalmology service at the Children's Hospital of Western Ontario, London. PATIENTS: Eighty orthophoric patients (mean age at presentation 19 months [range 4 to 50 months]) with a family history of strabismus or with a diagnosis of pseudostrabismus, blocked tear duct or chalazion, followed for an average of 36 (range 6 to 129) months, and 41 patients with surgically corrected infantile esotropia (mean age at testing with the 20-PD base-out test 21 months [range 9 to 50 months]), followed for an average of 53 (range 14 to 117) months. INTERVENTIONS: Twenty-PD base-out test and red-green Worth four-dot test at near (0.3 m). OUTCOME MEASURE: Presence of peripheral fusion. RESULTS: The 20-PD base-out test had a positive predictive value of 100% in detecting peripheral fusion in the orthophoric patients and 93% (95% confidence interval [CI] 82% to 100%) in the patients with surgically corrected infantile esotropia. CONCLUSIONS: Although the 20-PD base-out test had a negative predictive value of 21% (95% CI 0% to 43%), a positive response remains a useful indicator of peripheral binocular single vision in children too young to undergo more formal sensory testing.

Comparison of laser and manual removal of corneal epithelium for photorefractive keratectomy.

BACKGROUND: Photorefractive keratectomy relies on precise ablation of cornea stromal tissue to achieve a desired change in refraction. The routine technique for photorefractive keratectomy has been manual debridement of the epithelium prior to performing excimer laser ablation. We investigated whether laser ablation versus manual debridement of the corneal epithelium influences the refractive result. METHODS: A retrospective matched controlled study analyzing the refractive outcome of 46 eyes after excimer laser photorefractive keratectomy was performed. Half of the eyes had the corneal epithelium ablated with the excimer laser, while the other half had mechanical removal. Topical postoperative corticosteroid dosing was different in the two groups. All photorefractive keratectomies were performed by the same surgeon (H.V.G.). The two groups were analyzed for statistical differences in refractive outcomes and corneal haze after 6 months. RESULTS: The mean preoperative spherical equivalent refraction in the laser removal group was -5.11 diopters (D), and -5.09 D in the manual group. At 6 months postoperatively, the mean spherical equivalent refraction in the laser group was +0.03 D and -0.40 D for the manual group (p = .21). At no point postoperatively was there any significant difference in the mean refractive outcome or variance of the refractive results between the two groups, although there was a trend toward greater correction with laser ablation of epithelium. There was no statistical difference in the amount of stromal haze by slit-lamp microscopy in the two different debridement groups. There was no significant difference in final uncorrected visual acuity, rate of reepithelialization, or reported incidence of halos or glare between the two groups. CONCLUSION: There was a tendency toward greater refractive correction at 6 months using the laser for corneal epithelial removal than manual debridement, although the difference was not statistically significant. The trend toward slightly higher correction emphasizes the need for care when removing epithelium with the laser to prevent concomitant stromal ablation.

Pneumococcal endophthalmitis associated with nasolacrimal obstruction.

Pneumococcal endophthalmitis can be a devastating postoperative infection after cataract extraction or penetrating keratoplasty. Streptococcus pneumoniae was isolated as the causative agent in three of the 124 patients (2%) who were treated for endophthalmitis at our institution between 1984 and 1990. Two of the three patients lost light perception in the affected eye. All three patients had previously unrecognized or untreated chronic nasolacrimal obstruction of varying causes. We studied the role of pneumococcal lacrimal conjunctivitis in the pathogenesis of the postoperative pneumococcal endophthalmitis in these patients.