title: Tear-film lipid layer morphology and corneal sensation in the development of blinking in neonates and infants.
abstract: The aim of the study was to evaluate the role of lipid layer thickness and corneal sensation in the development of blinking in neonates. The study group comprised sixty-four neonates and infants (mean age 27.5 +/- 15 (sd) weeks, range 3.4-52) whose mothers were attending a general practice healthy baby clinic. Spontaneous eye-blink activity was determined from digital videographic recordings; tear film lipid layer morphology wasexamined using interference patterns produced by the Keeler Tearscopetrade mark Plus over a five-point grading scale (higher grades are associated with thick and stable lipid films); corneal sensation threshold was assessed with the Non-Contact Corneal Aesthesiometer (NCCA), using the eye-blink response as an objective indication that the cooling stimulus had been felt; palpebral aperture dimensions were measured using calibrated digital still images of the eye in the primary position. The overall mean spontaneous blink-rate was found to be 3.6 (+/- 0.3) blinks min(-1), and the mean interblink time was 21.6 (+/- 2.8) s. The lowest blink-rates were observed in the 0-17-week age group (average 2 blinks min(-1)). The blink-rate showed a highly significant correlation with age (r = 0.46, P < 0.01). The overall mean lipid layer grading was 3.6 (+/- 0.2 SE) arbitrary units. Higher grades were found in the newborn and the mean grading score reduced with age (P < 0.01). The mean sensation threshold to blink (TTB) was 0.69 (0.04 SE) mbar, which did not differ from a control group of older subjects (P > 0.05). There was a rapid increase in palpebral aperture length and width from birth to 1 year old, with surface area increasing by 50% over the same period. We concluded that the low rate of spontaneous eye blink activity in neonates is associated with a thick stable lipid layer that may be a function of a small palpebral aperture. Furthermore, neonates appear to have the capacity to detect ocular surface cooling, which is a major trigger for spontaneous blinking.
authors.affiliation: Henry Wellcome Laboratories for Visual Science, Department of Optometry and Visual Science, City University, London, UK.
authors.forename: John G
authors.initials: JG
authors.lastname: Lawrenson
authors.forename: Rosalind
authors.initials: R
authors.lastname: Birhah
authors.forename: Paul J
authors.initials: PJ
authors.lastname: Murphy
mesh_terms: D001767:Blinking / Q000502:physiology*; D002657:Child Development; D003080:Cold Temperature; D003315:Cornea / Q000294:innervation*; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D008055:Lipids / Q000502:physiology*; D009475:Neurons, Afferent / Q000502:physiology*; D012684:Sensory Thresholds; D013666:Tears / Q000502:physiology*; D014741:Video Recording
chemical_list: D008055:Lipids
references.citation: Cornea. 1999 May;18(3):333-42
references.pmid: 10336038
references.citation: Pain. 1979 Aug;7(1):1-14
references.pmid: 503550
references.citation: Optom Vis Sci. 1997 Jan;74(1):8-13
references.pmid: 9148269
references.citation: Prog Retin Eye Res. 1998 Oct;17(4):565-96
references.pmid: 9777650
references.citation: Exp Eye Res. 1998 Dec;67(6):681-6
references.pmid: 9990332
references.citation: Am J Ophthalmol. 1997 Jul;124(1):24-30
references.pmid: 9222228
references.citation: Adv Neurol. 1988;49:25-37
references.pmid: 2964173
references.citation: Am J Ophthalmol. 1997 Dec;124(6):729-35
references.pmid: 9402818
references.citation: Adv Exp Med Biol. 1998;438:281-95
references.pmid: 9634898
references.citation: Acta Paediatr Acad Sci Hung. 1980;21(1):55-6
references.pmid: 7446087
references.citation: Exp Neurol. 1999 Jul;158(1):214-20
references.pmid: 10448434
references.citation: Acta Ophthalmol (Copenh). 1989 Oct;67(5):525-31
references.pmid: 2589051
references.citation: J Craniofac Genet Dev Biol. 1982;2(3):239-42
references.pmid: 7166598
references.citation: Brain Res. 1999 Oct 2;843(1-2):136-44
references.pmid: 10528120
references.citation: Br J Ophthalmol. 1996 Jun;80(6):553-5
references.pmid: 8759269
references.citation: Adv Exp Med Biol. 1998;438:305-8
references.pmid: 9634900
references.citation: Cont Lens Anterior Eye. 1998;21 Suppl 1:S31-40
references.pmid: 16303394
references.citation: Early Hum Dev. 2001 Oct;65(1):21-37
references.pmid: 11520626
references.citation: Ophthalmology. 2002 Mar;109(3):526-9
references.pmid: 11874756
references.citation: Dev Med Child Neurol. 1990 Feb;32(2):142-50
references.pmid: 2338178
references.citation: Brain. 1983 Sep;106 (Pt 3):643-53
references.pmid: 6640274
references.citation: Ophthalmic Physiol Opt. 1996 Mar;16(2):101-7
references.pmid: 8762770
references.citation: Acta Ophthalmol (Copenh). 1973;51(3):325-34
references.pmid: 4800597
references.citation: J Pediatr. 1978 May;92(5):787
references.pmid: 641630
references.citation: Ophthalmology. 2003 Jul;110(7):1408-11
references.pmid: 12867400
references.citation: Int Ophthalmol. 1994;18(1):15-9
references.pmid: 7960410
references.citation: IEEE Trans Biomed Eng. 2000 Feb;47(2):249-58
references.pmid: 10721632
references.citation: Ann Neurol. 1979 May;5(5):453-7
references.pmid: 223495
references.citation: Ophthalmology. 1987 Oct;94(10):1276-80
references.pmid: 3684205