Changes in diadenosine polyphosphates during alignment-fit and orthokeratology rigid gas permeable lens wear.
OBJECTIVE
To evaluate the levels of dinucleotides diadenosine tetraphosphate (Ap(4)A) and diadenosine pentaphosphate (Ap(5)A) in tears of patients wearing rigid gas permeable (RGP) contact lenses on a daily wear basis and of patients wearing reverse-geometry RGP lenses overnight for orthokeratology treatment.


METHODS
Twenty-two young volunteers (10 females, 12 males; 23.47 ± 4.49 years) were fitted with an alignment-fit RGP lens (paflufocon B) for a month, and after a 15-day washout period they were fitted with reverse-geometry RGP lenses for corneal reshaping (paflufocon D) for another month. During each period, tears were collected at baseline day 1, 7, 15, and 28. Ap(4)A and Ap(5)A were measured by high-pressure liquid chromatography (HPLC). Additionally, corneal staining, break-up time (BUT), Schirmer test, and dryness symptoms were evaluated.


RESULTS
Ap(4)A concentrations increased significantly from baseline during the whole period of daily wear of RGP lenses (P < 0.001); concentration was also significantly higher than in the orthokeratology group, which remained at baseline levels during the study period except at day 1 (P < 0.001) and day 28 (P = 0.041). While BUT and Schirmer remained unchanged in both groups, discomfort and dryness were significantly increased during alignment-fit RGP daily wear but not during the orthokeratology period.


CONCLUSIONS
Daily wear of RGP lenses increased the levels of Ap(4)A due to mechanical stimulation by blinking of the corneal epithelium, and this is associated with discomfort. Also, orthokeratology did not produce symptoms or signs of ocular dryness, which could be a potential advantage over soft contact lenses in terms of contact lens-induced dryness.
Department of Optics II (Optometry and Vision), School of Sciences, University of Minho, Braga, Portugal. gonzalocarracedo@gmail.com
Gonzalo
G
Carracedo
José Manuel
JM
González-Méijome
Jesús
J
Pintor
D000328:Adult; D002851:Chromatography, High Pressure Liquid; D003261:Contact Lenses; D003315:Cornea / Q000378:metabolism; D015226:Dinucleoside Phosphates / Q000378:metabolism*; D005260:Female; D015590:Fluorophotometry; D006801:Humans; D008297:Male; D054158:Orthokeratologic Procedures; D010975:Platelet Aggregation Inhibitors / Q000378:metabolism*; D017755:Prosthesis Fitting; D013666:Tears / Q000378:metabolism*; D014662:Vasoconstrictor Agents / Q000378:metabolism*; D055815:Young Adult
D015226:Dinucleoside Phosphates; D010975:Platelet Aggregation Inhibitors; D014662:Vasoconstrictor Agents; C012275:P(1),P(5)-di(adenosine-5'-)pentaphosphate; C020733:diadenosine tetraphosphate