Guttae is the plural form of the word gutta, from a Latin word meaning "drops." They are miniscule bumps that form and face inward on the layer of endothelium on the backside of the cornea of the eye. These tiny bumps are an indication of a genetic eye disease known as Fuchs' Endothelial Corneal Dystrophy (FECD). The disease comes in two forms: early onset from a mutation on chromosome 8A, and late onset from mutations on chromosomes 13 and 18. As the guttae accumulate, they cause vision loss and swelling of the cornea.
The cornea is the clear tissue at the front of the eye. The endothelium is a layer of translucent, hexagonal cells of bundled collagen fibers on the inside of the cornea facing the lens, stroma, and retina. The guttae cause the endothelial cells to become thinner than normal, particularly in the tops of the guttae as they elevate and spread out.
Symptoms are usually noticed after the formation of several guttae, when the eyes feel coarse or rough and vision blurs as fluids start to collect in the cornea and stroma, which are normally in a dry state. Bright lights may cause discomfort or pain in people with this condition, and the eyesight usually fluctuates throughout the day and from day to day. Most patients report poor night vision and blurry vision with poor contrast in colors, as if grease had been smeared over eyeglass lenses.
Another characteristic of corneal dystrophy is a thickening of the Descemet's membrane, which lines the endothelium and faces towards the lens and retina. Guttae will continue to form along this membrane. There are five stages of Fuchs' dystrophy, and it usually takes 10 to 20 years to progress from stage to stage. As more and more guttae form and spread, the stages become a measurement of how much of the eye surface is affected and the level of distortion of vision.
There are two surgical treatments for FECD. In an outpatient surgery called penetrating keratoplasty, the cornea is removed and replaced with a donor cornea that is sutured in place. Another possible surgery is called Descemet's stripping with endothelial keratoplasty. This surgical procedure replaces only the back half of the endothelial layers and Descemet's membrane behind the cornea with parts from a donor.