OBJECTIVE MEASUREMENT OF CONTACT LENS-INDUCED CONJUNCTIVAL REDNESS

Ocular redness is the principal clinical sign of any inflammatory resp onse affecting the anterior segment of the eye. The aims of the curren t investigation were: (1) to develop an objective method to quantify t he severity and geographic distribution of redness, (2) to validate th at technique by determining its precision and compare its finding to c linical rating, and (3) to apply this technique to evaluating the diur nal variation in ocular redness associated with daily and extended sof t contact lens wear. The objective capture and analysis technique invo lved the following steps: (1) direct image formation on the CCD array of a high resolution, high sensitivity 3/4 inch Cohu camera via a Niko n Macrolens and (2) capture and image analysis with a PC-based dedicat ed transputer. The key steps were: filtering to accurately locate the limbus and electronic sectioning with differential intensity color ana lysis at fixed intervals away from the limbus. The technique gave a di rect measurement of the number and size of the vessels present. The re sult obtained lead to the following conclusions: (1) the digitization and analysis of video recordings of the bulbar conjunctiva provide a p recise measurement of the level of conjunctival redness, (2) subjectiv e rating of low level of conjunctival redness, using an overall nine i ncrement clinical scale, did not relate closely to the objective measu rement of conjunctival redness, (3) for non-contact lens wearers, redn ess in the evening was similar to redness measured upon waking, and gr eater than redness 2 h postwaking. In contrast, in daily soft contact lens wearers, redness was maximal in the evening and greater than befo re insertion or during wear in the morning. In extended soft contact l ens wearers, redness was maximal upon waking when it was greater than in the evening, and (4) digitization and analysis video recordings of the redness response of the bulbar conjunctiva are sufficiently sensit ive clinical research tools to monitor diurnal variation of the inflam matory response of the anterior segment of the eye.