Review: Measurement Techniques for Intraocular Pressure

The literature on intra-ocular pressure dynamics is reviewed, including tonometer design and calibration, the influence of corneal-scleral mechanics, and scleral rigidity factors. Drugs that influence the outflow facility of the trabecular mesh work (TM) are discussed. Transmural pressure drop across the lamina cribosa (LC) is an important parameter, in terms of quantifying potential glaucoma damage to the optic nerve.

It is important to determine the intra-ocular pressure, the fluid pressure inside the eye, in order to evaluate for patients at risk from glaucoma, because of potential damage to the optic nerve. Tono meters are calibrated to measure pressure in millimeters of mercury [mmHg]. There are many different types of tonometers, including Schiotz, Goldmann, Perkins, Marg-MacKay, Air-Puff (American Optical), and the new “Triggerfish” wireless contact lens (Sensimed AG). Preliminary mechanics and development work in this area was presented by Friedenwald. 

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Interpupillary Distance Measurements among Students in the Kumasi Metropolis

Interpupillary distance has been defined by various authors as the distance between the centres of the pupils in millimetres. It is abbreviated as PD, or more correctly, IPD. Normal values of IPD for the Ghanaian student population have been established. The IPD values are relevant for the manufacture of spectacles corrections for the Ghanaian student population. Different experimental techniques, differences in sample sizes, differences in age ranges and limited background information about study subjects hinder the generalization of IPD values for different sets of people from different ethnic backgrounds.

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