A longitudinal study of the relationship between intraocular and blood pressures.

The relationship between intraocular and systemic blood pressures was investigated in a prospective study of 572 middle-aged men. There was no consistent relationship between intraocular pressure at first visit and age. Subjects with an intraocular pressure greater than 20 mm Hg had a significantly higher systolic blood pressure than controls matched for age. An autoregressive model was used to examine the relationship between change in intraocular pressure and initial intraocular pressure, age, and blood pressure. When the authors compared data obtained 1 or 2 years apart, a change in intraocular pressure was positively correlated with a change in systolic blood pressure. Thus, the results of this study indicate that changes in intraocular pressure over time are associated with changes in systolic blood pressure and that intraocular pressure does not necessarily increase with age.

Stimulation of tyrosinase in human melanocytes by pro-opiomelanocortin-derived peptides.

Human melanocytes, maintained on bovine corneal endothelium-derived extracellular matrix for at least 4 days in the absence of phorbol 12-myristate 13-acetate (PMA) and cholera toxin (CT), displayed increased tyrosinase activity when exposed to several pro-opiomelanocortin-derived (POMC) peptides. Melanocytes from 9 of 14 donors showed significantly increased tyrosinase activity after treatment with adrenocorticotropic hormone (ACTH; mean increase 320 +/- 107 (S.E.M.)% of control, P < 0.005), while melanocytes from 8 of 13 donors increased tyrosinase in the presence of diacetyl-melanocyte stimulating hormone (di-MSH; mean increase 223 +/- 31 (S.E.M.)% of control, P < 0.005). Maximal increases in tyrosinase were seen after treatment with 10(-10) M ACTH and with 10(-6) M di-MSH. In two cell cultures which showed tyrosinase stimulation, melanin synthesis was similarly increased in the presence of added POMC peptides. PMA but not CT increased tyrosinase activity in melanocytes cultured under these conditions. In the presence of staurosporine, an inhibitor of protein kinase C (PKC), the magnitude of the increase in tyrosinase due to PMA, ACTH and di-MSH was significantly reduced. These results indicate that tyrosinase activity in melanocytes from most human donors, under appropriate conditions, is susceptible to the stimulatory effects of POMC peptides, that ACTH is considerably more potent than di-MSH in this test system and that in human cells the PKC pathway may be important in modulating melanogenesis.

Knowledge or noise. Scientific publication and the electronic journal.

Over the last few years, the Internet has grown exponentially and is developing a role in the exchange of scientific information. However, a number of problematic issues are associated with electronic publications, including limited transmission speed, undependable file longevity, poorly documented postpublication editing, copyright infringement, and cultural impediments to acceptance. By measure of citation frequency, electronic journals seem to have limited influence within scientific discourse, but this medium is as yet in its infancy. Since electronic publication enjoys many potential advantages over traditional print publication, it is expected to gain far greater influence over time. The American Medical Association group of publications recognizes this and intends to develop its electronic publications with attention to maintaining traditional critical scientific standards.

Benign lymphoid hyperplasia of the conjunctiva in children.

Benign lymphoid hyperplasia of the conjunctiva occurs infrequently in children, and its presentation, clinical course, and appropriate management are not well established. We describe 2 children with nasal conjunctival masses that on pathological examination demonstrated benign lymphoid hyperplasia. Local irradiation of residual tissue was deferred, and the lesions remained stable for 1 year in one case and for 3 1/2 years in the other case. No systemic involvement had occurred. Although the natural history of extranodal lymphoid hyperplasia in children is poorly documented, most cases of nodal lymphoid hyperplasia in children are at very low risk of malignant transformation. Careful observation for local and systemic disease is indicated for ocular adnexal lymphoid hyperplasia in children until a more complete understanding of its natural history is available.

Effects of estrogens on human melanocytes in vitro.

Subjects with elevated serum estrogen concentrations, such as those who are pregnant or ingesting estrogen-containing contraceptive medication, may develop increased skin pigmentation. As little information is available on the mechanism(s) underlying this relationship, the in vitro effects of estrogens on melanocytes cultured from normal human skin were examined. Physiological concentrations of 17 beta-estradiol (10(-11) to 10(-9) M) significantly increased the activity of tyrosinase in melanocytes from 15 of 23 subjects. The observed increases ranged from 1.2- to 2.4-fold. Melanin synthesis, which correlated with tyrosinase activity (r = 0.98, P < 0.001) was increased to a similar extent. Melanin extrusion was also increased by 17 beta-estradiol (10(-9) M). The estrogens, estriol (10(-9) M) and estrone (10(-9) M) stimulated tyrosinase activity and melanin extrusion to a lesser extent than 17 beta-estradiol. The analogue 17 alpha-estradiol (10(-9) M) was shown to have effects on melanocyte tyrosinase activity and melanin extrusion that were equivalent to those of 17 beta-estradiol. The pure estrogen antagonist ICI 164384 (10(-6) M) also stimulated tyrosinase activity. Cycloheximide (50 micrograms/ml) inhibited 17 beta-estradiol-induced tyrosinase stimulation (P < 0.001). These results indicate that several aspects of melanocyte function respond directly to estrogenic stimulation. The equivalent effects of the 17 alpha-analogue and a "pure" anti-estrogen suggest that the 17 beta-estradiol response may be mediated through a non-classical mechanism which is similar to that described in other tissues of neural crest origin.

A dual optic accommodating foldable intraocular lens.

AIM: To design an accommodating intraocular lens with extended accommodative range that can be adapted to current standard phacoemulsification and endocapsular implantation technique. METHOD: Ray tracing analysis and lens design; cadaver eye implantation. RESULTS: Ray tracing analysis indicated that axial movement of an exaggerated converging anterior optic linked by spring loaded haptics to a compensatory static diverging posterior optic produced greater change in conjugation power of the eye compared to axial movement of a single optic lens. A dual optic one piece foldable silicone lens was constructed and implanted via a 4 mm corneal incision into the capsular bag of two cadaver eyes. CONCLUSION: A dual optic intraocular lens design can increase the optical effect of a given displacement and suggests improvements for accommodating intraocular lenses.

Bilateral diffuse lamellar keratitis following bilateral simultaneous versus sequential laser in situ keratomileusis.

AIM: To determine the difference in the incidence of bilateral diffuse lamellar keratitis (DLK) in patients undergoing simultaneous versus sequential laser in situ keratomileusis (LASIK) as an indication of intrinsic risk for inflammation. METHODS: A retrospective non-comparative case series of 1632 eyes that had undergone bilateral, simultaneous or sequential LASIK between April 1998 and February 2001 at a university based refractive centre by three surgeons. All cases that developed clinically evident DLK were identified and reviewed. In order to identify isolated cases and exclude those caused by environmental factors, when more than one patient in a given session developed DLK, the session was excluded. The main outcome measure was the incidence of unilateral and bilateral isolated, non-epidemic DLK. RESULTS: Of 1632 eyes, 126 eyes (7.7%) of 107 patients developed at least grade 1 DLK. In six operating sessions, DLK was observed in more than one patient per session, and on this basis 13 patients were excluded. 16 of the 94 remaining patients developed DLK in both eyes (17.0%). Six of 41 patients (14.6%) in the simultaneous group, versus 10 of 53 patients (18.9%) in the sequential group developed bilateral DLK (p >0.5). CONCLUSION: In isolated, non-epidemic bilateral DLK, a similar incidence was observed regardless of whether the surgery was simultaneous or sequential, suggesting an underlying intrinsic cause for DLK.

Evaluation of intraocular lens power calculation formulas in the triple procedure.

PURPOSE: To determine whether the choice of intraocular lens (IOL) power formula improves IOL power predictions and whether personalized constants within the IOL power formula are critical factors in improving refractive predictions after combined penetrating keratoplasty, cataract extraction, and IOL implantation. METHODS: Records of 46 patients who had the triple procedure between January 1988 and December 1992 were evaluated using the SRK II, SRK/T, Holladay, and Hoffer Q formulas to predict the postoperative spherical equivalent refractions for implanted lens power. Calculations were carried out with and without the use of personalized constants. The predictive accuracy of each formula was assessed by comparing the actual postoperative spherical equivalent refractive error with that predicted by the formulas. The predictive error and the distribution of predictive errors were used to assess predictive accuracy. RESULTS: There was no difference in the mean absolute predictive errors and the distribution of predictive errors for the four formulas evaluated (P > .05). The use of personalized formula constants significantly reduced the mean absolute predictive error for the SRK II, SRK/T, and Holladay formulas (P < .05) and approached significance for the Hoffer Q formula. CONCLUSION: The findings suggest that the choice of IOL power formula does not affect IOL power predictions in the corneal triple procedure; however, personalized constants within a formula appears to be a critical factor in improving postoperative refractive predictions.

Changing indications for penetrating keratoplasty, 1989-1993.

The purpose of this study was to identify new trends in the changing indications for penetrating keratoplasty. We retrospectively reviewed the clinical and pathologic diagnoses of 1,104 corneal buttons that had been submitted to the Estelle Doheny Eye Pathology Laboratory, Los Angeles, during the 5-year period 1989-1993. The leading indications, in order of decreasing frequency, were pseudophakic corneal edema (24.8%), regrafts (21.3%), scarring with or without chronic inflammation (11.1%), keratoconus (7.1%), aphakic corneal edema (6.4%), and ulcerative conditions (5.8%). The incidence of pseudophakic corneal edema remained stable over the study period and was actually surpassed by regraft in the last year of the study. Although pseudophakic corneal edema remains the predominant indication for penetrating keratoplasty, our findings suggest that its occurrence rate has begun to level off.

Phakic intraocular lenses.

Because of the potential risks associated with phakic IOL implantation, the current use of these devices is mainly in the treatment of high and extreme myopia which are expected to respond poorly to keratorefractive procedures. Overall, in this setting, the outcomes of phakic IOL implantation have been rather favorable, with significant improvement in uncorrected visual acuity, and tolerable visual symptoms in terms of glare and halo.

Evaluating the human optical system: corneal topography and wavefront analysis.

In this article we review three different systems for evaluating the human optical system: placido-disc based corneal topography, scanning slit topography, and wavefront sensors. We briefly describe the principles of each system, and discuss the strengths and weakness. We suspect all three will be used by ophthalmologists in the coming decade.

Excimer laser photorefractive keratectomy.

The excimer laser has proved to be a precise and versatile tool for treating refractive errors. Excimer laser photorefractive keratectomy for myopia is now an established safe and effective alternative to contact lenses and glasses, and should be part of the ophthalmologist's standard armamentarium for treating this condition. This article provides a brief overview of the basic principles underlying excimer laser technology, as well as the surgical technique and postoperative management of myopic correction.

Predictors of outcome in fungal keratitis.

PURPOSE: To analyse predictors of clinical outcome in fungal keratitis. METHODS: Data was collected during a prospective, randomized, controlled, double-masked clinical trial of treatment for fungal keratitis. Clinical features at presentation and demographics were collected at the enrollment visit for all patients. Pre-specified clinical outcomes included 3-month visual acuity and infiltrate/scar size, time to re-epithelialization, and corneal perforation. A separate multivariable model with each outcome as the dependent variable included all predictor variables. RESULTS: Predictors for worse 3-month visual acuity include older age (P=0.024), worse presentation visual acuity (P<0.001), larger infiltrate size at presentation (P<0.001), and pigmented ulcer (P=0.030). Larger infiltrate size at presentation was a significant predictor of worse 3-month infiltrate/scar size (P<0.001). Larger epithelial defect size was a significant predictor of perforation (P=0.0013). Predictors of longer time to re-epithelialization include infiltrate size at presentation (P<0.001) and older age (P=0.025). CONCLUSION: Ulcer severity at presentation is highly predictive of worse outcomes. Presentation of clinical characteristics such as baseline acuity and infiltrate scar can provide important information to clinicians about prognosis, and may help guide management and treatment decisions. Prevention of corneal ulcer remains important, as it is difficult to change the course of the ulcer once it has begun.

Microbiological cure times in acanthamoeba keratitis.

AIMS: The purpose of this study was to estimate the duration of treatment necessary for sequential acanthamoeba laboratory tests from corneal scrapings to become negative, and to assess predictors that affect this duration period. METHODS: We included all patients with at least one positive acanthamoeba culture or Giemsa stain at the F.I. Proctor Foundation Microbiology Laboratory from 1996 to 2009. A parametric survival analysis was performed among patients with repeat cultures to assess significant predictors for extended clearance time. Simulations were performed to estimate clearance time in the entire patient population, assuming imperfect sensitivity. RESULTS: Thirty-seven patients with laboratory evidence of acanthamoeba had testing at 69 time points. The median clearance time among eyes with repeat cultures was 42.5 days (interquartile range (IQR) 22.0-82.0 days; unadjusted parametric model). Initial visual acuity was the only predictor significantly associated with clearance time in univariate analyses (P<0.0001). Using initial visual acuity as a predictor for clearance time among the entire patient population, the estimated clearance time decreased to 38.7 days (95% confidence interval (CI) 27.9-53.5 days). When the imperfect sensitivity of the culture technique was also taken into account, the estimated clearance time was 44.1 days (95% CI 31.9-61.0 days). CONCLUSION: The duration of infection with acanthamoeba keratitis undergoing treatment has not been well characterized. In this report we estimate a median clearance time of approximately 6 weeks, with an IQR of 22-82 days.