[Margin reflex distance measure by computerized image processing in rigid contact lens wearers]

To measure the MRD (margin reflex distance) in rigid contact lens wearers and controls by a new method, based on computerized image processing.

The patients were selected from the Contact Lens Sector of the Ophthalmology Service at the "Complexo Hospitalar Santa Casa de Porto Alegre", and they were divided into two groups: the first was formed of rigid contact lens wearers (63 eyes) and the second of patients without previous history of contact lens wear (30 eyes). All patients were photographed with a digital camera (Nikon Coolpix 4300). The margin reflex distance was measured by a computerized image processing using the Image J program. The study excluded patients that underwent any kind of intraocular or eyelid surgery, patients with congenital ptosis and patients with giant papillae conjunctivitis.

The method utilized to measure margin reflex distance seems simple and more accurate. The average value of the margin reflex distance in the case group was 2.46 mm and in the control group 2.72 mm. The study shows that there is a tendency of decreasing the margin reflex distance with contact lens wear although the data were not statistically significant (p=0.22). The margin reflex distance values show a greater variability in the case group (41.46%) than in the control group (28.96%), that is more homogeneous.

This study introduced a new method to measure the margin reflex distance using computerized image processing. This method is accessible and could help in follow-up of the margin reflex distance in contact lens wearers, specially those rigid.