Klaus Trier

Effect of Day Length on Eye Growth, Myopia Progression, and Change of Corneal Power in Myopic Children

OBJECTIVE Because of the northern location of Denmark, the length of the day over the year varies from 7 to 17.5 hours. Experimental and clinical results suggest that the development of myopia may be related to ambient light exposure. The purpose of current study was to investigate whether axial eye growth, myopia progression, or corneal power change in Danish myopic children varies with the length of the day. DESIGN Cross-sectional study. PARTICIPANTS Two hundred thirty-five children 8 to 14 years of age found to have myopia during screening for a clinical trial (ClinicalTrial.gov identifier, NCT00263471; accessed December 6, 2005). All children found to have any value of spherical equivalent that was myopic (<0 diopters [D]) at the first of 2 visits were included. METHODS Cycloplegic refraction was measured using an autorefractor, axial eye length, and corneal power using an automatic combined noncontact partial coherence interferometer and keratometer. The accumulated number of daylight hours during the measurement period was calculated for each participant using an astronomical table. MAIN OUTCOME MEASURES Change over 6 months in axial length, refraction, and corneal power. RESULTS Accumulated hours of daylight ranged from 1660 to 2804 hours. Significant correlations were found between hours of daylight and eye elongation (P = 0.00), myopia progression (P = 0.01), and corneal power change (P = 0.00). In children with an average of 2782 ± 19 hours of daylight, axial eye growth was 0.12 ± 0.09 mm, myopia progression was 0.26 ± 0.27 D, and corneal power change was 0.05 ± 0.10 D per 6 months, whereas in children with an average of 1681 ± 24 hours of daylight, axial eye growth was 0.19 ± 0.10 mm, myopia progression was 0.32 ± 0.27 D, and corneal power change was -0.04 ± 0.08 D per 6 months. CONCLUSIONS Eye elongation and myopia progression seem to decrease in periods with longer days and to increase in periods with shorter days. Children should be encouraged to spend more time outside during daytime to prevent myopia. FINANCIAL DISCLOSURE(S) The author(s) have no proprietary or commercial interest in any materials discussed in this article.

Biochemical and ultrastructural changes in rabbit sclera after treatment with 7-methylxanthine, theobromine, acetazolamide, or L-ornithine

AIMS To examine a possible effect of 7-methylxanthine, theobromine, acetazolamide, orl-ornithine on the ultrastructure and biochemical composition of rabbit sclera. METHODS Groups of pigmented rabbits, six in each group, were dosed during 10 weeks with one of the substances under investigation, and one untreated group was the control. Samples of anterior and posterior sclera were taken for determination of hydroxyproline, hydroxylysine, proline, proteoglycans, uronic acids and dermatan sulphate, chondroitin sulphate, and hyaluronic acid. Sections were examined with electron microscopy, and the diameter of the individual collagen fibrils was measured. RESULTS Treatment with theobromine produced a significant increase in the contents of hydroxylysine, hydroxyproline, and proline in both anterior and posterior sclera, while 7-methylxanthine increased the contents of hydroxyproline and proline selectively in posterior sclera. Acetazolamide, on the other hand, significantly decreased the contents of hydroxyproline and proline in samples from anterior sclera. Uronic acids in both anterior and posterior sclera were significantly reduced by treatment with 7-methylxanthine, and l-ornithine significantly reduced uronic acids in posterior sclera. An inverse correlation between contents of hydroxyproline and uronic acids was found. The mean diameter of collagen fibrils was significantly higher in the posterior sclera from rabbits treated with 7-methylxanthine or theobromine, and significantly lower in rabbits treated with acetazolamide or l-ornithine compared with controls. In the anterior sclera, fibril diameter was significantly reduced in all treatment groups compared with controls. A positive, significant correlation between fibril diameter and content of hydroxyproline and proline was found in posterior sclera. CONCLUSION 7-Methylxanthine, a metabolite of caffeine, increases collagen concentration and the diameter of collagen fibrils in the posterior sclera, and may be useful for treatment or prevention of conditions associated with low level and/or inferior quality of scleral collagen, such as axial myopia, chronic open angle glaucoma, and possibly neovascular age related macular degeneration. The apparent loss of collagen induced by chronic treatment with acetazolamide should be taken into consideration as a potentially harmful side effect. These results may indicate that scleral biochemistry and ultrastructure are influenced by the retinal pigment epithelium. One possible explanation is that the scleral fibroblasts which produce the collagen are sensitive to changes in the physiological electric field created by the retinal pigment epithelium.

Glycosaminoglycans in human breast cancer

Abnormal concentrations of glycosaminoglycans (GAG) have been reported for various types of tumors, suggesting that they may play a role in neoplasia. The correlation between the content of individual GAGs was studied in breast tumor tissues. The total content of GAG was estimated by uronic acid analysis. The relative distributions of dermatan sulphate, heparan sulphate, hyaluronic acid and chondroitin sulphate were measured after cellulose acetate electrophoresis. Mammary tissue samples were obtained at the time of surgery from 11 women, 6 with fibroadenomata and 5 with carcinoma. From each patient, biopsies were obtained centrally in the tumor and perilesional areas adjacent to the tumor, and also from clinically uninvolved tissue in the same region. In the central areas, it was found that carcinoma had a significant increase in chondroitin sulphate and uronic acid content, and a significant decrease in dermatan sulphate content, as compared with fibroadenoma. The chondroitin sulphate content in perilesional carcinomatous tissue was significantly greater than in clinically uninvolved tissue.

Effects of 7-methylxanthine on the sclera in form deprivation myopia in guinea pigs

Purpose:  The aim of this study was to determine the effect of the adenosine receptor antagonist 7‐methylxanthine (7‐MX) on form deprivation myopia in 3‐week‐old guinea pigs.

Adenosine receptor protein changes in guinea pigs with form deprivation myopia.

Acta Ophthalmol. 2010: 88: 759–765

The effect of hyaluronic acid on cartilage in the immobilized rabbit knee

Out of 30 adult rabbits, 20 had one knee immobilized with a plaster of Paris cast for 6 or 12 weeks, and 10 rabbits were used as untreated controls. Prior to immobilization, 10 knees were injected with high-molecular weight hyaluronic acid. The articular cartilage of the femoral condyles was studied by light microscopy, whereas that of the patella and tibia was analyzed biochemically. Degenerative changes of the articular cartilage similar to those seen in arthrosis were observed after 6 weeks. The intraarticular injection of hyaluronic acid did not prevent these changes; instead, the reparative processes seemed inhibited.

Latanoprost eye drops increase concentration of glycosaminoglycans in posterior rabbit sclera.

PURPOSE Glycosaminoglycans are important components of ocular tissues such as the sclera. The pressure reducing effect of a new antiglaucoma drug, latanoprost, is based on an increase in the uveo-scleral outflow by way of modulation of the intracellular matrix of the ciliary body. The purpose of the study was to test the effect of latanoprost on the content of glycosaminoglycans in rabbit cornea and sclera. METHODS Twelve rabbits were studied. Six rabbits were treated for 12 weeks with latanoprost eye drops and 6 with hydroxypropylmethylcellulose, dextran 70 eye drops for control. Samples were taken from cornea and anterior, lateral, and posterior sclera. Glycosaminoglycans were determined quantitatively by spectrophotometry (uronic acids). RESULTS A significant increase in the concentration of uronic acids was found in all three localisations of sclera from latanoprost-treated animals. The increase was 26%, 24%, and 20% in anterior, lateral, and posterior sclera, respectively. CONCLUSIONS Long-term treatment with latanoprost induces biochemical changes in sclera. The results indicate that topically applied latanoprost reaches the posterior parts of the rabbit eye.

Biochemical changes in rabbit sclera following destruction of pigment epithelium

Abstract The long‐term effect of destruction of the pigment epithelium by sodium iodate on the biochemistry of rabbit sclera was studied in one group with intravenous injection of sodium iodate, and in a second group with injection of sodium iodate into the right eye. Intravenous treatment produced a non‐significant increase in the uronic acid concentration. In the second group the untreated fellow eye was microscopically intact, but was shown (as the treated eye) to alter the concentration of uronic acid in different parts of the sclera. All eyes from treated animals exhibited changes in the relative content of the various glycosaminoglycans and in the content of hydroxyproline, hydroxylysine and proline. This work indicates that the pigment epithelium may play a key role in the control mechanism of the scleral connective tissue, and this again has major implications in terms of a possible medical treatment of axial myopia.