title: Human scleral permeability. Effects of age, cryotherapy, transscleral diode laser, and surgical thinning.
abstract: OBJECTIVE
  To determine the in vitro permeability of human sclera to compounds varying in molecular weight. To evaluate the effects of age, cryotherapy, transscleral diode laser, and surgical thinning on scleral permeability.
  
  
  METHODS
  Scleral tissue from 97 human eye bank eyes was tested individually in a two-chamber Ussing apparatus with the following hydrophilic radiolabeled compounds on one side of the chamber: 5-fluorouracil, sucrose, dexamethasone, methotrexate, inulin, and three separate dextran polymers (MWt = 10,000, 40,000, and 70,000). Scleral hydration levels were obtained on 20 more scleral specimens. Additional groups of scleral specimens were treated with either a cryotherapy probe, a transscleral diode laser retinopexy probe, or partial thickness lamellar dissection, and specimens were mounted in the Ussing chambers for testing. Scleral tissue was digested to measure the amount of radioactivity present. Scleral sections were examined with electron microscopy.
  
  
  RESULTS
  Scleral hydration was maintained during the perfusion. The mean scleral permeability (cm/second x 10(-6) +/- SD) was established for each of the above compounds. Age, cryotherapy, or diode laser treatment did not alter permeability or ultrastructure of the sclera. Surgical thinning significantly increased the scleral permeability to dexamethasone (P = 0.011) and methotrexate (P = 0.037).
  
  
  CONCLUSIONS
  This study establishes baseline human scleral permeability to a series of hydrophilic compounds with various molecular weights. Age, cryotherapy, and diode laser treatment do not alter the permeability or ultrastructure of the sclera, whereas surgical thinning significantly increases permeability.
authors.affiliation: Department of Ophthalmology, Emory University, Atlanta, GA 30322, USA.
authors.forename: T W
authors.initials: TW
authors.lastname: Olsen
authors.forename: H F
authors.initials: HF
authors.lastname: Edelhauser
authors.forename: J I
authors.initials: JI
authors.lastname: Lim
authors.forename: D H
authors.initials: DH
authors.lastname: Geroski
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000378:metabolism*; D001834:Body Water; D002648:Child; D002675:Child, Preschool; D003452:Cryosurgery; D003911:Dextrans / Q000737:chemistry / Q000493:pharmacokinetics; D005472:Fluorouracil / Q000737:chemistry / Q000493:pharmacokinetics; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D007444:Inulin / Q000737:chemistry / Q000493:pharmacokinetics; D053685:Laser Therapy; D008875:Middle Aged; D008970:Molecular Weight; D010539:Permeability; D010599:Pharmacokinetics; D012590:Sclera / Q000378:metabolism* / Q000601:surgery / Q000648:ultrastructure; D013395:Sucrose / Q000737:chemistry / Q000493:pharmacokinetics
chemical_list: D003911:Dextrans; D013395:Sucrose; D007444:Inulin; D005472:Fluorouracil