Biomedical subjects
Publications and source records attributed to Harry H Mark.
An 83-year- old man with squamous cell carcinoma of the conjunctiva and cornea is presented. Ocular surface carcinomas, though rare, are readily apparent to the practicing clinician, leading to early diagnosis and treatment on the road to preventing serious ocular damage, and occasionally loss of life. They may become more common as they often occur in immunocompromised individuals.
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Solutes concentration in the aqueous humor of the eye is highest near the ciliary processes in the posterior chamber (p.c.) and lowest near the trabecular meshwork in the anterior chamber (a.c.). The high osmotic gradient across the semipermeable iris causes it to easily move forward at this location and occasionally occlude the iridocorneal angle. Vector analysis of the forces generated by miosis helps explain on osmotic grounds why it reduces the intraocular pressure, while at the same time the analysis elucidates the reason for the higher frequency of angle closure glaucoma when the anterior chamber is shallow.
PURPOSE: To investigate the clinical applicability of a physical principle that suggests that a large globe offers less resistance to applanation than a smaller one. SETTING: Referral practice, Bridgeport, Connecticut, USA. METHODS: The correlation between axial length and applanation tonometry in 513 adult eyes, arbitrarily chosen from a referral practice, was examined using regression analysis. RESULTS: A statistically significant negative correlation was found; that is, for every 1.0 mm increase in axial length, the tonometry value was 0.29 units lower (P =.0002). In women, the mean axial length was 1.04 mm shorter and the mean intraocular pressure 0.54 mm Hg higher than in men. CONCLUSIONS: Globe size influenced applanation tonometry readings. Hence, when the tonometry record does not fit the clinical findings, axial length measurement may help interpret its significance.