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Tariq M. Almudhaiyan, Sawsan R. Nowilaty, Arif O. Khan, Mohamed A. Aldahmesh, Khalid F. Tabbara, Fowzan S. Alkuraya; Biometric and Molecular Correlations in Posterior Microphthalmos. Invest. Ophthalmol. Vis. Sci. 2012;53(14):1542.
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© ARVO (1962-2015); The Authors (2016-present)
Posterior microphthalmos (PM) can be clinically defined as a normal-appearing anterior segment, characteristic papillomacular folds, a cycloplegic refraction >8.00 diopters (D), and an axial length (AL) <20 mm. The purpose of this study is to biometrically and molecularly analyze our clinically-diagnosed cases of PM.
Prospective IOLmaster biometry, keratometry, corneal pachymetry and candidate gene analysis (MFRP, PRSS56) in 25 patients (50 eyes) clinically-diagnosed with non-syndromic PM by experienced ophthalmologists (SRN, AOK).
25 patients (14 males, 11 females; 2-47 years old [median 16]) from 13 families (12 Saudi, one Indian) had best-corrected visual acuity ranging from 20/30 to 20/160. Right eye mean data were as follows: cycloplegic refraction +15.09 D (9.88-18.75), keratometry 48.89 D (41.91-52.25), horizontal corneal diameter 11.42 mm (10- 13.25), corneal pachymetry 564 microns [469 to 624] and AL 16.25 mm (14.88-19.88). AL had a strong inverse correlation with keratometry (Pearson coefficient -0.88, p <0.001) and a positive correlation with corneal diameter (Pearson 0.64, p =0.001). Left eye data were similar. 19/25 patients (8/13 families) harbored 4 different homozygous PRSS56 mutations, the one Indian patient harbored a homozygous MFRP mutation, and 5/25 patients (4/13 families) had no mutation in either gene. The phenotype of the patient with the MFRP mutation was not distinguishable from the rest of the series. The severity of PRSS56 mutation seemed to correlate with the severity of phenotype: severe mutations were associated with shorter axial lengths (mean 15.72mm), steeper corneas (mean 49.63D), smaller corneal diameters (mean 11.12mm) and higher hyperopia(mean +16.42D), than eyes with less severe mutations (16.37mm, 48.37D, 11.69mm, and +14.55D respectively) or no identified mutation (17.19mm, 47.93D, 11.64mm and +13.58D, respectively).
A strong inverse correlation between axial length and keratometry characterizes PM. The fact that corneal diameter decreases as AL decreases in PM suggests that PM and nanophthalmos represent different degrees of high hyperopia rather than distinct entities. PRSS56 mutations are the major cause for PM in the Saudi population, but genetic heterogeneity exists. PRSS56 mutation severity seems to correlate with PM phenotypic severity.
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