Corneal sensation after cataract and refractive surgery

Abstract

Most surgical procedures involving the anterior segment of the eye disrupt the normal organization of corneal innervation. Since denervation of the cornea results in impaired epithelial wound healing, increased epithelial permeability, decreased epithelial metabolic activity, and loss of cytoskeletal structures associated with cellular adhesion, it is important to identify the factors that determine the extent of neural regeneration. Mechanisms of corneal nerve damage and studies of corneal nerve fiber loss and reinnervation after cataract and refractive surgery--epikeratophakia, cryokeratomileusis, keratomileusis in situ, photorefractive keratectomy, laser in situ keratomileusis, and phacoemulsification--are reviewed and the decrease in corneal sensitivity, as a measure of corneal destruction and corneal metabolism, after these surgical procedures is compared.

The effect of preservative-free HP-Guar on dry eye after phacoemulsification: a flow cytometric study

“…Moreover, an alteration in central corneal sensitivity has been found in patients who have undergone cataract surgery, 30 secondary to the corneal nerve section, which may potentially disrupt the neural loop, reducing tear secretion by the lacrimal gland. 31 The increase in TBUT and the improvement of the OSDI and its subscales after treatment with HP-Guar may be due to its peculiar mechanism of action. Upon binding Systane content, stored at a pH of 7.0, with tears, which have a pH between 7.5 and 7.8, borate ions meet with the HP-Guar and form a matrix, which increases the retention of compound's lubricant (PEG 400 and PG), resulting in an increase in the stability of the tear film on the ocular surface, and thus in decreased corneal desiccation 32 and permeability.…”

Evaluation of dry eye-associated symptoms and signs after microincision cataract surgery

“…Therefore, temporary dry eye symptoms might develop until the nerves regenerate again [2,10]. Most surgical procedures, especially surgical incisions that cause denervation of the cornea, also result in impaired epithelial wound healing, increased epithelial permeability, decreased epithelial metabolic activity and loss of cytoskeletal structures associated with cellular adhesion [5]. The changes in tBUT and Schirmer tests have been reported in previous studies [1,2,4,[9][10][11].…”

“…Some studies have reported aggravation of dry eye symptoms and signs after cataract surgery [1,2]. Many factors, such as topical anesthesia and eye drops containing preservatives like benzalkonium chloride, surgical incision types, exposure to light from operating microscope, disrupt to normal organization of the corneal innervation, might affect the ocular surface environment after cataract surgery [3][4][5].…”

Cataract Surgery and Dry Eye

“…It is estimated that there are approximately 7000 sensory receptors per square millimeter in the human corneal epithelium, implying that injuries to individual epithelial cells may be adequate to give a sensation (Muller et al, 2003). Traditionally, it was believed that most sensory nerves enter into the cornea along a transverse meridian (3-and 9-o'clock); this was in accordance with the clinical findings of better corneal sensation and less dry eye symptoms in patients undergoing laser in situ keratomileusis (LASIK) with a nasal hinge (Donnenfeld et al, 2003;Kohlhaas, 1998;Lee and Joo, 2003). However, the current description is that nerve bundles enter the peripheral mid-stromal cornea in a radial fashion, along different meridians and parallel to the corneal surface.…”

“…This is one of the major pathogenic pathways in induction of postoperative dry eye in patients undergoing ophthalmic surgeries. Most surgical procedures that cause denervation of the cornea result in impaired epithelial wound healing, increased epithelial permeability, decreased epithelial metabolic activity and loss of cytoskeletal structures associated with cellular adhesion (Donnenfeld et al, 2003;Kohlhaas, 1998). As mentioned earlier, the normal corneal epithelium has the highest density of sensory nerve endings throughout the human body.…”