Specular Microscopy Underestimates Corneal Endothelial Cell Count In Presence Of Phakic Artisan Lens Implant?

The specular microscope is an optical reflection microscope where a slit of light is focussed on the corneal endothelial surface and specularly (mirror-like) reflected light rays are focussed onto film plane for viewing on a real-time monitor. Errors can arise in the quantitative evaluation of corneal endothelium. The fixed frame method can have large errors in the presence of a higher number of border cells

Corneal endothelial cell loss is known to occur following any eye surgery especially with phakic lens implants. 50 patients who had undergone explantation of phakic artisan lens (iris-fixated) implants were recruited in this study to analyse the behaviour of their corneal endothelial cells

All patients underwent phakic artisan/artiflex lens implants surgery to correct high myopia between the periods 2000 to 2007 at the Optimax/Ultralase Eye Clinics, UK

Normal corneal endothelial cell density (CED) at birth ranges between 4000 and 5000 (cells/mm²) that declines with aging at a rate of 0.3–0.6% per year with an approximate value of 2000–3000 cells/mm² in a normal adult eye. Thus, when the endothelial cell count goes below 700 cells/mm ², the functional reserve is minimum and corneal oedema is likely to occur

Corneal endothelial cell count was measured before implantation, during follow up visits and post explantation

Retrospective analysis of the corneal endothelial cell count was done in all 50 patients who had underwent phakic artisan/artiflex lens (ICL) explantation. The ICL has remained in the eye for 15 to 23 years. 70% of the patients were females. Average age during implantation was 23, and during explantation was 48. Corneal endothelial cell count was measured using a "non-contact" specular microscope (Tomey). Average pre-operative cell count was 2500.

Cell count immediately prior to explant ranged from 900 to 1900 with clear cornea. 40% of patients showed a dramatic increase in their corneal endothelial cell count post explant surgery as early as within 3 weeks

Diabetes and chronic kidney disease patients, certain systemic medications  such as amantadine, prescribed for movement disorders/Parkinsonism have been implicated in causing gradual loss of endothelial cells. As the endothelial imaging is based on specular reflex, any optical hindrances in front of the endothelial monolayer will affect the quality of the image to delineate the endothelial cells, Various conditions that interfere with the quality of endothelial imaging are a poor ocular surface tear film, epithelial haze, stromal scarring, and alterations in the Descemet's membrane

It is important to consider all the factors in evaluating the corneal endothelial cell count in ICL patients to avoid unnecessary explantations