Ethical considerations related to outcome studies-based clinical practice guidelines.

Expanding demand for health services is occurring in the face of diminishing resources. Root causes for this phenomenon include advancing expensive new technology and marked variations in quality of care and patterns of practice. Practice guidelines resulting from valid and appropriate outcome studies have the potential to promote consistency and quality. Perceived drawbacks to such guidelines include over-regulation and loss of autonomy for both physicians and patients. Clinical practice guidelines are discussed in the context of major ethical theories, including deontology, utilitarianism, and contractarianism. The conflicting needs and motivations of physicians, patients, third-party carriers, and society as a whole are discussed relative to these different ethical perspectives. Although contrasting ethical foundations likely will lead to significantly different solutions to the healthcare resource problem, it is only through educated and reasoned discussion that this difficult problem can be tackled. Sound ethical discipline is imperative when considering the related issues of equity, justice, and autonomy in a society with progressively decreasing resources.

Follow-up of the original cohort with the Ahmed glaucoma valve implant.

PURPOSE: To study the long-term results of the Ahmed glaucoma valve implant in patients with complicated glaucoma in whom short-term results have been reported. METHODS: In this multicenter study, we analyzed the long-term outcome of a cohort of 60 eyes from 60 patients in whom the Ahmed glaucoma valve was implanted. Failure was characterized by at least one of the following: intraocular pressure greater than 21 mm Hg at both of the last two visits less than 6 mm Hg at both of the last two visits, loss of light perception, additional glaucoma surgery, devastating complications, and removal or replacement of the Ahmed glaucoma valve implant. Devastating complications included chronic hypotony, retinal detachment, malignant glaucoma, endophthalmitis, and phthisis bulbi; we also report results that add corneal complications (corneal decompensation or edema, corneal graft failure) as defining a devastating complication. RESULTS: The mean follow-up time for the 60 eyes was 30.5 months (range, 2.1 to 63.5). When corneal complications were included in the definition of failure, 26 eyes (43%) were considered failures. Cumulative probabilities of success at 1, 2, 3, and 4 years were 76%, 68%, 54%, and 45%, respectively. When corneal complications were excluded from the definition of failure, 13 eyes (21.5%) were considered failures. Cumulative probabilities of success at 1, 2, 3, and 4 years were 87%, 82%, 76%, and 76%, respectively. Most of the failures after 12 months of postoperative follow-up were because of corneal complications. CONCLUSIONS: The long-term performance of the Ahmed glaucoma valve implant is comparable to other drainage devices. More than 12 months after the implantation of the Ahmed glaucoma valve implant, the most frequent adverse outcome was corneal decompensation or corneal graft failure. These corneal problems may be secondary to the type of eyes that have drainage devices or to the drainage device itself. Further investigation is needed to identify the reasons that corneal problems follow drainage device implantation.

Initial clinical experience with the Ahmed Glaucoma Valve implant.

PURPOSE: We studied the Ahmed Glaucoma Valve implant, an aqueous shunting device that has a unidirectional valve mechanism designed to prevent postoperative hypotony in eyes with intractable glaucoma. METHODS: In this multicenter, prospective clinical trial, we studied 60 eyes (60 patients) with increased intraocular pressure or glaucoma that had not responded to medical treatment, laser photocoagulation, or previous glaucoma surgery, in which the Ahmed Glaucoma Valve implant was placed to decrease intraocular pressure. RESULTS: Success was defined as intraocular pressure less than 22 mm Hg and greater than 4 mm Hg for two months or longer, intraocular pressure that was lowered by at least 20% from preoperative values (in eyes with preoperative intraocular pressures less than 22 mm Hg), and no additional glaucoma surgery or visually devastating complications. Cumulative probability of success at 12 months was 78%. Eight (13%) of 60 eyes had intraocular pressure less than 5 mm Hg the first postoperative day. Two other eyes had shallow anterior chambers, which required anterior chamber reformation. The major complications associated with the use of the valve were serous choroidal detachments in 13 eyes (22%), blockage of the tube in six eyes (10%), malposition of the tube in four eyes (7%), a suprachoroidal hemorrhage in one eye (2%), and corneal graft rejections in three (19%) of 16 eyes with corneal grafts. CONCLUSIONS: Although the 12-month success with the Ahmed Glaucoma Valve implant is similar to that reported for other drainage devices, the complications associated with overfiltration in the immediate postoperative period appear to be less frequent than with other valved drainage devices. Randomized, prospective studies to compare the Ahmed Glaucoma Valve implant with other drainage devices are needed to make clinical comparisons of the different devices.

The effects of photofrin on human Tenon's capsule fibroblasts in vitro.

Pharmacological agents that modulate the wound healing process by inhibiting fibroblast proliferation may improve the success of proliferative vitreoretinopathy and glaucoma filtration surgery and may have applications in other surgical fields. It is possible that light-absorbing chemicals can be used to cause photo reactions in proliferating fibroblasts as a means of controlling this wound healing process. We present the effects of photofrin porfimer sodium (serial tenfold dilutions 1000-0.00001 micrograms/ml) on human fibroblasts from Tenon's capsule in vitro, with and without photoactivation with Argon green laser (700 mW for 1 and 5 minutes) and with bright sunlight (for 1 and 5 min). The cell density was measured on day 2 by 3H-thymidine uptake and on day 9 by means of a coulter counter, and optical density was measured in terms of the activity of the enzyme hexosaminidase. Each experiment was performed three times in quadruplicate. The counts were averaged for each drug concentration and mean cell count with a standard error as well as the 50% inhibitory doses (ID50s) were calculated. Photofrin demonstrated an inhibitory dose response curve (dark toxicity) to human fibroblasts. Concentrations greater than 100 micrograms/ml of photofrin alone completely inhibited cell growth. Concentrations less than 0.01 micrograms/ml did not have any effect on fibroblast proliferation. There was no significant log dose shift of the inhibitory effect of photofrin with the exposure to either sunlight or Argon laser. Photofrin may be used as a cytotoxic agent alone but does not appear to be activated by light to modulate subconjunctival fibroblast proliferation within the laser parameters used.

Effects of Cy to sine Arabino side-Impregnated Bioerodible Polymers on Glaucoma Filtration Surgery in Rabbits.

A prospective, randomized double-masked placebo-controlled study was performed to determine the effects of a bioerodible polymer containing cytosine arabinoside (Ara-C) on the success of full thickness filtration surgery in 21 rabbits. The polymer was a polyanhydride composed of bis(pcarboxyphenoxy) propane and sebacic acid. The polymer and Ara-C (1 mg by weight) were combined and compressed into discs 3-mm and 1-mm thick. Control polymers contained no Ara-C. Posterior lip sclerectomy surgery was performed bilaterally, with one eye randomly receiving the polymer with the Ara-C and the fellow eye receiving the control polymer. All eyes were examined on the first postoperative day and every other day thereafter. Intraocular pressures (IOPs) were found to be significantly lower (p < 0.04) in the experimental eyes during the 5th through the 15th postoperative day, with the mean difference ranging from 3.5 to 6.0 mm Hg. The median number (+/-SE) of days until failure of the filters was 10.5 (+/-0.66) days in the control group and 15.2 (+/-1.94) days in the experimental group, the difference being statistically significant. There were no significant differences between the groups with regard to conjunctival injection, corneal epithelial defects, anterior chamber inflammation, lens changes, or intraoperative or postoperative complications. This study suggests that polymer drug delivery of Ara-C may be a safe and efficacious adjunct in temporarily increasing the success rate of glaucoma filtering surgery in a rabbit model.

The effects of Nd:YAG laser iridotomy on the corneal endothelium.

We studied 18 eyes of 18 patients undergoing Nd:YAG laser peripheral iridotomy for occludable anterior chamber angles. A Q-switched laser was used for all treatments. Preoperative and postoperative pachymetry and corneal endothelial cell counts were obtained centrally, in the nontreated superonasal quadrant, and in the treated superotemporal quadrant. No significant differences were found between preoperative and postoperative corneal thickness at any site. A small decrease in endothelial cell count (95 cells/mm2) at the treated site was statistically significant (P = .04).

Biometric variables in patients with occludable anterior chamber angles.

Biometric studies of the ocular dimensions in eyes with narrow anterior chamber angles provide insight into the pathophysiology of pupillary block and may show which eyes are more prone to develop angle-closure glaucoma. We reviewed the records of 56 patients with occludable angles examined between 1980 and 1984. Initial biometric data obtained on the patients included corneal diameter, anterior chamber depth, lens thickness, and ocular axial length. The average length of follow-up was five years. Of 54 patients with complete clinical records, 20 (37%) eventually required peripheral iridectomy after a mean duration of 16 months from the initial examination. Cox's survival analysis showed a strong correlation between shortened duration to peripheral iridectomy and increasing lens thickness/ocular axial length ratio factor (P = .03). No other variables were significantly related to outcome. This suggests that the lens thickness/ocular axial length ratio may be useful as a predictor of clinical outcome in narrow-angle glaucoma.

Glaucoma in patients with uveitis.

The records of 100 patients (161 eyes) with uveitis were reviewed retrospectively to determine the prevalence of increased intraocular pressure, the forms of uveitis most commonly associated with glaucoma, and the forms that require specific glaucoma therapy. Secondary glaucoma was present in 23 patients (31 eyes): three of 24 patients with acute uveitis (three eyes, 12% of acute uveitis patients) and 20 of 76 patients with chronic uveitis (28 eyes, 26% of chronic uveitis patients). Eighteen patients (26 eyes, 78% of glaucoma patients) with chronic uveitis required long-term medical therapy to control intraocular pressure. Three patients (three eyes, 12% of glaucoma patients) with acute uveitis required short-term therapy to control intraocular pressure. The remaining two patients had transient increases in intraocular pressure that did not require treatment or that responded to treatment of intraocular inflammation alone. One patient with chronic uveitis (two eyes, 4% of glaucoma patients) required filtering surgery. At least five patients (eight eyes, 22% of glaucoma patients) had glaucomatous visual field defects. The results of this survey are consistent with the concept that secondary glaucoma is a management problem in patients with anterior segment inflammation and chronic rather than acute uveitis. An algorithm for the management of increased intraocular pressure in patients with uveitis is proposed.

Intraocular pressure measurement with the Tono-Pen through soft contact lenses.

We evaluated a miniaturized digital and electronic tonometer, the Tono-Pen, for accuracy of intraocular pressure measurement in the presence of a contact lens. In the manometric study, the Tono-Pen was used to measure a known intraocular pressure, ranging from 10 mm Hg to 60 mm Hg in a cadaver eye over soft contact lenses with different powers and a plano-T bandage lens. There was significant bias in pressure measurement over all contact lenses except for the plano-T, which had no bias at any level. In the clinical study, the intraocular pressures of 40 eyes in 20 normal patients were measured with and without a plano-T contact lens in place. Analysis of variance showed no significant interactive effect between the right and left eyes, with or without the lens. There was no significant difference in the Tono-Pen measurement of intraocular pressure over a plano-T contact lens compared with no lens.

The use of bioerodible polymers and 5-fluorouracil in glaucoma filtration surgery.

A study was performed to examine the effect of a localized and sustained delivery of 5-fluorouracil (5-FU) on the success of glaucoma filtration surgery in 18 rabbits in a prospective, randomized, double-masked and placebo-controlled fashion. A bioerodible polyanhydride composed of bis (p-carboxyphenoxy) propane and sebacic acid was used as the drug carrier. The polymer and 5-FU (20% by weight) were compressed into 3 mm diameter discs, 1 mm thick. The polymer with the 5-FU was randomized to one eye and the fellow eye received the blank polymer. The results showed that intraocular pressures (IOP) were lower in the experimental eyes during the 5th through 17th postoperative days, but eventually both experimental and control eyes returned to preoperative levels. Filtration blebs lasted longer in experimental eyes when compared to control eyes. Implant disappearance occurred after IOP elevations and bleb failure. Eventually, the filtration surgery failed in both the experimental and control rabbit eyes.

The Tono-Pen. A manometric and clinical study.

A new miniaturized, digital, electronic tonometer, the Tono-Pen (Intermedics, Pasadena, Calif), was evaluated for accuracy and reproducibility of results in the laboratory using enucleated human eyes with an indwelling pressure transducer (manometric study) and clinically using 100 eyes in 50 patients with normal corneas. Reproducibility was good in both the manometric study (SD = 1.09) and in the clinical study (SD = 1.21). Reproducibility of results was similar to that of the MacKay-Marg tonometer and the pneumotonometer in the manometric study, but less than that of the Goldmann applanation tonometer and the pneumotonometer in the clinical study. In the manometric study, the Tono-Pen had less mean error at high pressure ranges than either the MacKay-Marg tonometer or the pneumotonometer. In the clinical study, no statistically significant difference was found between the Tono-Pen and the applanation tonometer at pressures of 10 to 35 mm Hg (the extent of the data spread). In addition to being reliable and accurate, this miniaturized tonometer is portable and easy to use.

Effects of argon laser iridotomy on the corneal endothelium.

We studied 14 eyes of 14 patients undergoing argon laser peripheral iridotomy for occludable (narrow) anterior chamber angles. Preoperative and postoperative pachymetry and corneal endothelial cell counts by specular microscopy were obtained centrally and in both the treated and nontreated superior quadrants. No significant differences were found between preoperative and postoperative measurements of corneal thickness and endothelial cell counts in any area.