• Federico Bech, Omar González-González, Enol Artime, Joana Serrano, Ignacio Alcalde, Juana Gallar, Jesús Merayo-Lloves, and Carlos Belmonte.
• Instituto Universitario Fernández-Vega, Universidad de Oviedo & Fundación de Investigación Oftalmológica, Oviedo, Spain.
• Invest. Ophthalmol. Vis. Sci. 2018 May 1; 59 (6): 2281-2292.

PurposeTo define the characteristics and time course of the morphologic and functional changes experienced by corneal sensory nerves after photorefractive keratectomy (PRK).MethodsUnilateral corneal excimer laser photoablation was performed in 54 anesthetized 3- to 6-month-old mice; 11 naïve animals served as control. Mice were killed 0, 3, 7, 15, and 30 days after PRK. Excised eyes were placed in a recording chamber superfused at 34°C. Electrical nerve impulse activity of single sensory terminals was recorded with a micropipette applied onto the corneal surface. Spontaneous and stimulus-evoked (cold, heat, mechanical, and chemical stimuli) nerve terminal impulse (NTI) activity was analyzed. Corneas were fixed and stained with anti-β-Tubulin III antibody to measure nerve density and number of epithelial nerve penetration points of regenerating subbasal leashes.ResultsNerve fibers and NTI activity were absent in the injured area between 0 and 7 days after PRK, when sparse regenerating nerve sprouts appear. On day 15, subbasal nerve density reached half the control value and abnormally responding cold-sensitive terminals were recorded inside the lesion. Thirty days after PRK, nerve density was almost restored, active cold thermoreceptors were abundant, and polymodal nociceptor activity first reappeared.ConclusionsMorphologic regeneration of subbasal corneal nerves started shortly after PRK ablation and was substantially completed 30 days later. Functional recovery appears faster in cold terminals than polymodal terminals, possibly reflecting an incomplete damage of the more extensively branched cold-sensitive axon terminals. Evolution of postsurgical discomfort sensations quality may be associated with the variable regeneration pattern of each fiber type.

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