Philip P. Ellis

The cornea and disorders of lipid metabolism.

Disorders of lipid metabolism, either hyperlipidemia or hypolipidemia, are associated with the formation of corneal opacities. Corneal arcus, the most commonly encountered peripheral corneal opacity, is frequently associated with abnormal serum lipid levels, but may occur without any predisposing factors. Reports also have linked corneal arcus with alcoholism, diabetes mellitus and atherosclerotic heart disease. Unilateral arcus is a rare entity that is associated with carotid artery disease or ocular hypotony. Diffuse corneal opacities associated with hypolipidemic disorders such as LCAT deficiency, fish eye disease and Tangier disease, may be the initial manifestation of these disorders and puts the ophthalmologist in a position to make an early diagnosis. Corneal arcus, along with a central corneal opacity, is seen in Schnyders crystalline stromal distrophy. The association of the disorder with a dyslipidemia remains controversial. A review of lipid metabolism, corneal arcus and several disorders of lipid metabolism that affect the cornea are presented.

High-performance liquid chromatographic assay for antiinflammatory agents diclofenac and flurbiprofen in ocular fluids

An HPLC assay for diclofenac (DC) and flurbiprofen (FP) in a 100-microliters sample of aqueous humour is presented. After acetonitrile extraction, the residue is analyzed using a reversed-phase octyl column and ultraviolet detection. The method is simple and reproducible. Excellent selectivity and resolution are achieved using an acetic acid-acetonitrile-triethylamine mobile phase. The lower limit of detection, defined as the amount of drug required to produce a peak twice the threshold, was ca. 0.3 ng DC on column and ca. 0.4 ng on column FP. The utility of the method is demonstrated by determining drug levels in aqueous humour of normal rabbits and of patients undergoing cataract surgery. The assay should be applicable to other antiinflammatory agents.

Outpatient sedation for ocular examination

Outpatient sedation of infants, uncooperative children and, rarely, adults provides an opportunity to perform certain ophthalmologic diagnostic procedures such as tonometry, ophthalmoscopy and various electrophysiological studies (e.g., electroretinography and visual evoked response testing) without the expense and usage of an operating room. Many drugs have been recommended and used; all have limitations. The advantages and disadvantages of the more commonly used agents are reviewed. The known effects of these drugs on ocular function are presented.

Determination of acetazolamide in biological fluids by high-performance liquid chromatography

A high-performance liquid chromatographic (HPLC) assay for acetazolamide is presented. A 100-microliter sample is mixed with an aliquot of the internal standard solution and the mixture, buffered at pH 4.5, is extracted with ethyl acetate. The extract is evaporated to dryness and the residue is analyzed by HPLC, using a reverse-phase octadecylsilane column. The wavelength of the detection is 254 nm. The coefficient of variation (CV) in the within-day analysis of replicate 10-microgram/ml acetazolamide samples in human blood plasma was 6.5%, while the between-day CV was 7.1%. The procedures was developed for the 1-25 microgram/ml acetazolamide concentration range. The internal standard used is similar in chemical structure to acetazolamide and can be readily prepared in one step from a commercially available precursor. In addition to blood serum or plasma, the assay can also use aqueous and vitreous humor samples. Theophylline and acetaminophen interfere in the assay. The technique was used to determine the concentration of acetazolamide in the blood serum of human volunteers after an oral dose of the drug, and in the aqueous and vitreous humors of rabbits after an intravenous dose of acetazolamide.

Prolonged Aqueous Humor Levels of Subconjunctival Antibiotics After Treatment With Acetazolamide and/or Timolol

Many ophthalmologists routinely administer subconjunctival antibiotics at the end of cataract surgery for prophylaxis against bacterial endophthalmitis. Additionally they use acetazolamide and/or timolol to control intraocular pressure in the first 24-hour postoperative period. An animal study was undertaken to learn whether treatment with the aqueous humor suppressants, acetazolamide, and timolol prolongs the concentrations of antibiotics in the aqueous humor after subconjunctival administration of the antibiotic. Treatment with acetazolamide significantly increased concentrations of piperacillin; it had less consistent effects on tobramycin levels. Timolol treatment did not produce increased piperacillin concentrations at six hours; however, concentrations at 12 and 24 hours were significantly higher than in the controls. Timolol treatment increased tobramycin concentrations only at six hours. The combined use of timolol and acetazolamide produced significantly higher concentrations of piperacillin, but not of tobramycin.