Keratoconus can cause substantial distortion of vision, with multiple images, streaking and sensitivity to light all often reported by the patient. It is typically diagnosed in the patient's adolescent years. If afflicting both eyes, the deterioration in vision can affect the patient's ability to drive a car or read normal print.
Large epithelial plugs may cause more scattering of light, leading to the appearance of visual phenomena such as flares and starbursts — especially in situations such as night driving, where the stark light of car headlights abounds. These dark conditions cause the pupil to dilate, maximizing the amount of scattered light that enters the eye. In cases where large epithelial plugs lead to such aggravating symptoms, patients may seek further surgical treatment to alleviate the symptoms.
A conceptually opposite technique of using hexagonal incisions in the periphery of the cornea is known has Hexagonal Keratotomy (HK, described by Antonio Mendez of Mexicali, Mexico), which was used to correct low degrees of Hyperopia. The idea behind HK was to make six peripheral incisions forming a hexagon around the central cornea to steepen the hyperopic flat cornea and, thereby, focus the rays of light more precisely onto the retina. These incisions can be of two types, either connecting or non-connecting.
RK may be performed with different types, numbers, and patterns of incisions. They can have 4, 8, 12, 16 or 32 incisions made in a number of patterns and orientations based on refractive errors, surgeon style and surgeon training. Many of these patients have had additional incisional surgeries like Astigmatic Keratotomy (AK), where incisions are placed at the steepest points of the cornea in people with astigmatism to relax and transform the cornea to a more spherical shape. Some people have had a combination of intraocular surgeries, such as Pseudophakia or Phakic implants, along with their keratotomies and many underwent "purse-string" suturing to control over-correction (Dr. Green’s Lasso suture).