John C. Merritt

Topical Δ9‐Tetrahydrocannabinol and Aqueous Dynamics in Glaucoma

Abstract: Systemic Δ9‐tetrahydrocannabinol (THC), administered either by smoking marihuana or as synthetic THC in soft gelatin capsules, lowers ocular tension in various glaucomas, but at the expense of significant decreases in systolic blood pressure. Topical THC in light mineral oil vehicles, though effective in laboratory animals, was not shown effective in 0.05 and 0.1% topical solutions when administered to six subjects with primary open‐angle glaucoma in a randomized, balanced, double‐masked protocol. Light mineral oil, which has an affinity for corneal epithelium, is an optimum vehicle for administering drugs whose mechanisms of action are systemic rather than local within the eye. Further glaucoma research should therefore proceed with marihuanas containing insignificant levels of THC (less than 0.4%) and with various local delivery systems of the ocular‐active cannabinoid found in Cannabis sativa.

Clinicopathological Correlation of a Solitary Choroidal Tuberculoma

In a 34-year-old black man with pulmonary tuberculosis, a rapidly enlarging choroidal tuberculoma progressed to larger size, despite appropriate systemic anti-tuberculous therapy. The eye harboring the tuberculoma became blind and painful, and was subsequently enucleated. Conventional staining of tissue sections revealed a choroidal granuloma without evidence of organisms, but tubercle bacilli were demonstrated by fluorescence microscopy.

Retrolental fibroplasia: a multifactorial disease.

Among the factors that are often thought responsible for the resurgence of cicatricial retrolental fibroplasia (RLF) in premature, low birth weight neonates, a history of oxygen therapy is often held to be of greatest importance (1-3). Indeed, a history of oxygen therapy is found in most low birth weight infants who develop the acute retinovascular changes; however, a history of oxygen therapy alone has little reliability in predicting those infants who develop the blinding cicatricial changes (4). These facts suggest that the development of RLF may be influenced by many factors that, although not always identified, may exert a summating effect on the premature retina. The following case report of a premature infant who developed blinding cicatricial RLF following an operation emphasized the importance of the multifactorial origin of this disease.

Ocular sarcoidosis. A case-control study among black patients.

A case-control study was conducted to investigate possible environmental risk factors for ocular sarcoidosis. The factors studied were exposures to pine products and occupational histories of employment in the tobacco, lumber, and textile industries. The exposure histories of 29 female and 15 male cases, patients with newly diagnosed ocular sarcoidosis that were attending the Glaucoma/Uveitis Clinic of the North Carolina Memorial Hospital, were compared to those of 110 female and 28 male controls selected from out-patient clinics. Elevated risks for sarcoidosis were detected among those females that were exposed to burning pine or were employed in the tobacco industry. For males, positive associations were observed for chewing pine products and for employment in the lumber and textile industries. These preliminary data are consistent with incomplete phagocytic clearance of nonbiodegradable foreign bodies present within our environment that may become antigenic to the immunologically susceptible host. Confirmation of refutation of these hypotheses awaits additional clinical and epidemiological research within the sarcoidosis belt.

HLA-A, -B, and -Dr Antigenic Factors in Ocular Sarcoidosis

Sarcoidosis is a multisystem, idiopathic granulomatous disease characterized by diverse immunologic abnormalities. Ocular sarcoidosis is more common in American blacks than in whites; hence, environmental and genetic factors have been investigated in evaluations of the role of immunogenetic factors.

Lensectomy-vitrectomy for stage V cicatricial retrolental fibroplasia.

Ten infants (18 eyes) blind from stage V cicatricial retrolental fibroplasia were examined from January 1978 to January 1981 at North Carolina Memorial Hospital. The early perinatal factors which may have predisposed to the binding end-stage cicatrix are identified. To increase their visual potential and to prevent secondary angle closure glaucoma, 12 lensectomy-vitrectomies were performed on 12 eyes (eight infants). One eye (one infant) had a pars plana vitrectomy without lensectomy. Seven eyes (seven infants) were not operated. Five of these eyes (five infants) had stage VRLF while two eyes (two infants) remained stable at stage II RLF. All retinas remained detached immediately after surgery. Secondary vitrectomies with air injections (three eyes, two infants) similarly failed to attach any retinas. Adherence of ciliary epithelium to clear lens and retrolental membrane as visualized within the dilated pupil (Eifrig-Merritt sign) was an intra-operative indicator of imminent surgical failure. Two eyes (two infants) developed early vitreous hemorrhages, hyphemas, secondary glaucoma, and phthisis bulbi within 12 months. Follow-up data were unavailable on two infants. Blindness secondary to cicatricial retrolental fibroplasia is increasing due to increased survival of low birthweight premature infants. Since surgical visual rehabilitation is not possible after the retrolental cicatrix has formed, the risk factors common to this high risk population should prompt preventive therapies.