Biomedical subjects
Publications and source records attributed to M B Abelson.
Tear pH was measured in 44 normal subjects by immersing the lip of a microcombination glass pH probe in the tear fluid in the inferior cul-de-sac. The normal pH range was 6.5 to 7.6; the mean value was 7.0. This method provides a rapid and accurate measure of tear pH and may better our understanding of tear physiology and tear buffering capacity.
Ten normal human volunteers participated in a two-part study of H2-receptor activity in the ocular surface. Dimethylaminopropylisothiourea (trivial name, dimaprit dihydrochloride), a highly selective H2-receptor agonist, produced vasodilation without itch. Pretreatment with the H2-receptor antagonist, cimetidine, significantly blocked the vasodilatory effect of dimethylaminopropylisothiourea, whereas pretreatment with the H1-receptor antagonist, antazoline phosphate, did not. We conclude that H2-receptors are present in the human ocular surface.
Topical application of the nonimmune selective mast-cell degranulating agent, compound 48/80, produced the signs and symptoms of ocular allergy (itching, injection, chemosis, and mucous discharge) in eight guinea pigs, eight rabbits, and nine humans. The histamine H1 receptor antagonist, antazoline phosphate, blocked itching but not vasodilation in five humans pretreated with compound 48-80. This suggests that histamine was one of the mediators released by compound 48-80-induced degranulation. Compound 48-80 may be helpful in evaluating the effects of therapeutic agents capable of modifying mast-cell degranulation and in the study of mediators involved in external ocular inflammation.
We measured the levels of major basic protein and Charcot-Leyden crystal protein in tears from patients with ventral keratoconjunctivitis or miscellaneous inflammatory or noninflammatory ocular conditions, and from normal subjects. Patients with vernal keratoconjunctivitis had significantly increased levels of both proteins in their tears compared with the other subjects tested; levels of major basic protein seemed to correlate with the severity of the disease. The levels of Charcot-Leyden crystal protein paralleled those of major basic proteins.
Explore the source record for details and available documents.
Eight widely used commercially available ocular decongestants were compared on the basis of vasoconstrictive effectiveness. The ability of these preparations to counteract histamine-induced erythema and to block its recurrence when rechallenged after one hour was evaluated in six human subjects in seven sessions. All vasoconstrictors tested were effective. No preparation was statistically different from 0.02% naphazoline hydrochloride in vasoconstrictive effect. In fact, this intermediate concentration of naphazoline (0.02%) was found to be significantly better that the other nonprescription decongestant preparations tested as a group and not significantly different from a group of higher concentrations of naphazoline.
In two independent studies including 25 subjects each, naphazoline caused significant whitening (but did not prevent itching) in the histamine-induced red, itchy eye. Antazoline inhibited itching (but not redness) to a significant degree in the same model. The combination of naphazoline and antazoline produced significant whitening and inhibition of itching in all eyes challenged by histamine. The combination of the two drugs was more effective than either component alone in preventing redness. The antihistamine and combination of antihistamine/vasoconstrictor were equally effective in arresting itching.
A 35-year-old woman who had undergone bilateral penetrating corneal grafts for keratoconus had keratoconus in the eye that had received a graft 16 years earlier. A second penetrating keratoplasty was performed, and the excised button was examined with light and electron microscopy. Both the light and electron microscopic findings were consistent with the clinical diagnosis of keratoconus. Keratoconus in a graft for the same disease should be added to the list of late complications of successful keratoplasties.
We evaluated various technical aspects of tear collection to assess their influence on the measurement of tear histamine levels. We included several methods of collecting tears, storage of tears with and without freezing, storage for three vs ten days, and removal vs nonremoval of cells before freezing. We assayed tear samples in various groups of people with inflamed eyes. None of the various means of collecting or storing the tear samples influenced the histamine measured. The measuring technique is a stable one that requires minimal treatment of samples before assay. To date, we have found that only patients with vernal conjunctivitis have elevated tear histamine levels. Any increase of tear histamine over 10 ng/ml (geometric mean plus 2 S.D.) or any significant decrease is probably related to the disease itself and not to factors related to the technique used to measure tear histamine.
We compared the tear pH values of 44 normal, healthy volunteers, 20 patients with ocular disorders other than rosacea, seven patients with untreated, active ocular rosacea, and five patients with tetracycline-treated ocular rosacea. The group with untreated, active ocular rosacea had significantly more alkaline tear pH values than the other groups tested. In patients with tetracycline-treated ocular rosacea, tear pH values were not significantly different from those of normal subjects.
Histamine levels were measured in tears from normal volunteers (geometric mean, 5 ng/ml), patients with vernal conjunctivitis (16 ng/ml), and patients with a wide variety of external ocular inflammatory disease (3 ng/ml). Histamine levels were significantly higher in patients with vernal conjunctivitis than in normal subjects (P < 0.01) or patients with other types of ocular inflammation (P < 0.001). We postulate that histamine is an important mediator in the expression of the inflammatory response in vernal conjunctivitis, and that its elevation may be caused by abnormalities in the number of mast cells, the stability of the mast cells or in the system that regulates histamine.
Tear samples from 13 normal volunteers and nine patients with vernal conjunctivitis were assayed for histamine. Tears in both groups contained histamine. The normal subjects had values ranging from 2.2 to 36 ng/ml with a mean of 10.3 ng/ml. The vernal patients had histamine values ranging from 0 to 125 ng/ml with a mean of 3,.2 ng/ml. The presence of histamine in tears indicates a role for this important mediator in both the physiologic and immunologic processes of the external eye.
We analyzed the blinking motions of ten patients with inferior punctate keratopathy and ten normal subjects by means of time-lapse motion pictures. We also determined the frequency of blinking during one-minute intervals for each individual. Four types of blinking were distinguished: complete, incomplete, twitch, and forced blink. The average blinking frequency was about the same for both groups: 16 to 17 blinks per minute. The relative proportion of complete blinks, however, was much lower in patients with inferior punctate keratopathy than in normal subjects. The impaired blinking motion may be responsible for the punctate staining of the inferior corneal epithelium by producing exposure and inadequacies in the tear film. For this reason, these patients may benefit from blink training, application of tear substitutes, or soft contact lenses more than from the customary prescription of topical cortisone eyedrops.
A case of recurrent herpes simplex virus keratouveitis was studied using both electron microscopic and viral culture techniques. We describe a patient who had a particularly violent course, including three failed grafts, endophthalmitis, and wound leak. We report the identification of virus in a quiescent failed corneal graft and retrocorneal membrane; persistence of virus enabling its culture from the vitreous; and electron microscopic identification in the cornea removed at the third transplant. The identification of cases in which viral proliferation occurs is necessary for a greater understanding of the pathogenesis of herpetic corneal disease and for determining in which particular patient steroid therapy should be avoided.
The size, weight, and plasma cell content of main and accessory lacrimal glands were examined and compared to the number of plasma cells in the conjunctiva. There were from four to 35 accessory lacrimal glands in the upper conjunctiva and a rare accessory gland in the lower conjunctiva. The total accessory gland mass was approximately one tenth of the lacrimal gland mass although the number of plasma cells was approximately 1/20 of the mass. The number of plasma-cells in the lacrimal gland was estimated to be 3,200,000; in the conjunctiva, 2,100,000; and for the accessory glands, 180,000. Because of the many plasma cells in the relatively inaccessible lacrimal gland, cells of the lymphatic series may home to the lacrimal gland by non-antigenic mechanisms.
Explore the source record for details and available documents.
A multicenter open-label study investigated the clinical effectiveness and economic feasibility of switching 142 patients from dual therapy to twice-daily monotherapy with brimonidine for glaucoma or ocular hypertension. Evaluations were performed at baseline and 2 (visit 2) and 8 (visit 3) weeks after the switch. Patients completed a questionnaire that rated medication-related visual function and satisfaction (comfort, convenience, vision, ease of remembering to use drops) at each visit. At visit 3, investigators, taking into account IOP measurements, safety, and responses on the questionnaire, recommended whether the patient should remain on brimonidine. A pharmacoeconomic analysis, including the number of visits, cost of medication, and success rates, compared the cost of dual therapy with that of switching to brimonidine monotherapy. Of the 131 patients who completed the study, 77 (59%) had no change or a decrease in IOP from baseline, and 53 (41%) had an increase. Investigators recommended that 77% of the study completers continue to take brimonidine monotherapy. Extending treatment with brimonidine for 12 months would achieve a significant cost savings of 16%. Brimonidine monotherapy is an efficacious and cost-effective alternative to dual therapy for glaucoma and ocular hypertension. Appropriate monotherapy may be as effective as dual therapy for many patients, and a clinically relevant trial such as this may be economically advantageous for testing a switch.