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• W2062877993 abstract "Purpose: To evaluate corneal curvature, pachymetry, and endothelial cell density (ECD) in Marfan syndrome (MFS). Methods: A case–control study in which K values, pachymetry, and ECD were compared in 39 MFS eyes and 40 control eyes matched for age and refraction was conducted. MFS eyes with lens subluxation also were compared with eyes without subluxation. Results: The mean Kmed value in MFS eyes was lower than in the control eyes, 42.2 ± 1.9 versus 43.4 ± 1.4 dioptres (D), respectively (p = 0.02). Fifteen MFS eyes (38%) and three control eyes (8%) had Kmed values below 41.5 D (p = 0.0012). MFS eyes had generally more corneal astigmatism than control eyes, 1.1 ± 0.9 versus 0.8 ± 0.4 D (p = 0.035), and MFS eyes with lens subluxation had more corneal astigmatism than those without, 1.6 ± 1.1 versus 0.6 ± 0.3 D (p = 0.0002). Nine MFS eyes with corneal astigmatism exceeding 1.5 D also had a subluxated lens. No eyes had keratoconus. The mean pachymetry value was lower in MFS eyes compared to the controls, 485 ± 54.5 versus 514 ± 37.3 μm (p = 0.007); 24 MFS eyes (62%) and 10 control eyes (25%) had measurements below 500 μm (p = 0.01). The mean ECD values were similar in MFS and control eyes, 2815 ± 430 versus 2858 ± 458 cells/mm2 (p = 0.66). The mean K value, pachymetry, and ECD values did not differ between MFS eyes with and without lens subluxation. Conclusion: Decreased K values and pachymetry could indicate MFS regardless of subluxation. High corneal astigmatism is associated with subluxation in MFS. Subluxation should be identified in MFS eyes with high corneal astigmatism. Marfan syndrome (MFS), a systemic connective tissue disorder that typically involves the cardiovascular, skeletal, and ocular systems (De Paepe et al. 1996; Judge & Dietz 2005), causes laxity in the connective tissue and overgrowth of the long bones. The typical symptoms include deformities of the thorax, scoliosis, arachnodactyly (long fingers and toes), spontaneous pneumothorax, and dilatation, or dissection, of the ascending aorta. MFS has a strong association with a mutation in the gene encoding for extracellular matrix protein fibrillin 1, an important component of the connective tissue. However, not all individuals with the diagnosis carry this mutation, and the diagnosis is in many cases based on the clinical findings. Accurate and early diagnosis of MFS is important, because both cardiovascular and visual complications may be severe. Spontaneous subluxation of the crystalline lens (Fig. 1) is the only major ocular criterion of MFS, and it is known to be strongly associated with the diagnosis (Maumenee 1981; Hamod et al. 2003). The minor criteria include increased axial length, an abnormally flat cornea, and hypoplastic iris or ciliary muscle (De Paepe et al. 1996; Judge & Dietz 2005). Previous studies of corneal changes in MFS have reported K values (Heur et al. 2008) and pachymetry values (Sultan et al. 2002) that can be used as diagnostic tools. However, there is no consensus on threshold values for these changes to confirm or rule out MFS. Further studies of the ocular changes in MFS are needed to establish a more precise diagnosis. The right eye of a 25-year-old woman with Marfan syndrome has a superiorly subluxated lens. The pupil is dilated with a mydriatic agent. The aims of the current study were to measure mean K value, pachymetry, and endothelial cell density (ECD) in MFS eyes and to compare the values with that of unaffected control eyes matched for age and refraction. MFS eyes with subluxation then were compared with MFS eyes without subluxation. This study was performed in co-operation with the departments of Cardiology and Clinical Genetics at the Karolinska University Hospital in Stockholm, Sweden. Those departments store the records of a majority of the known cases of MFS around Stockholm, which had a population of 1.9 million in 2007. At the time of the study, these departments had records of 116 known cases of MFS, but 16 of the cases had deceased or moved to other regions. Thus, our colleagues at these departments sent 100 letters in total that described the study to possible candidates who were asked to contact the study group if they were interested in participating. A second reminder letter was sent to those who did not contact us in due time. Also, family members of patients with MFS were invited to participate. The inclusion criteria were a diagnosis of MFS based on the Ghent criteria (De Paepe et al. 1996) and age 12 or older. According to the Ghent criteria, major criteria in two or more different organ systems and involvement of a third organ system are required for the diagnosis, if the family, or genetic, history is not contributory. If a mutation known to cause Marfan syndrome in others is identified, one major criterion in an organ system and involvement of a second organ system are required. For ocular involvement, at least two of the minor criteria are required. The exclusion criteria were previous intraocular or corneal surgery. The more myopic eye of each participant was included in the study. Fifty six candidates were examined, and 39 of these met the inclusion criteria. The control group was comprised of individuals without MFS recruited from among the hospital staff and their families. As in the MFS group, the more myopic eye was included, and the exclusion criteria were the same as for the patients. This study was approved by the local ethics committee, and the data accumulation was in adherence to the tenets of the declaration of Helsinki. All participants received oral and written information about the study, and each participant provided written informed consent. For participants under 18 years, a parent or guardian provided written informed consent. This clinical case–control study was conducted at St. Erik’s Eye Hospital in Stockholm, Sweden, from January to December 2007. Before the measurements were performed, the manifest refraction and best spectacle-corrected visual acuity (BSCVA) were measured, and slit-lamp examination was performed. The Kmin and Kmax and pachymetry were assessed using the Orbscan II Segment Analyzer (Bausch & Lomb Inc.). Orbscan II has been report to be accurate for measuring corneal test surfaces (Cairns et al. 2002; Gonzalez Perez et al. 2004). The Kmed value was calculated as the mean values of Kmin and Kmax in dioptres (D), and the corneal astigmatism was the difference between Kmax and Kmin (D). The corneal thickness was measured using Orbscan, and the values at the thinnest point were recorded in micrometres (μm). The endothelial cell layer was imaged using Topcon IMAGEnet-640, and the ECD in cells per mm2 was assessed using a semi-automated method. An ophthalmic nurse who was specially trained in the use of the device performed all assessments. Statistical analyses were performed using the Student’s t-test for most parameters. For sphere, the Mann–Whitney U test was applied because the data were not normally distributed. For cross-tabulations, the chi-square test or the two-tailed Fisher’s exact test was used. A p value <0.05 was considered statistically significant. Odds ratio (OR) for some suggested diagnostic values in corneal changes and their association with MFS were also calculated. Of the 56 possible subjects with MFS who contacted us, 39 met the inclusion criteria. Five subjects were excluded because of unconfirmed MFS, 11 because of previous intraocular or corneal surgery, and one because of epilepsy that prevented an Orbscan examination from being performed owing to the flickering light inside the device. Forty unaffected individuals served as the control group. The baseline characteristics of the MFS subjects and controls are shown in Table 1. The mean age (p = 0.83) and spherical refraction (p = 0.18) of the two groups did not differ significantly. The MFS group was divided into subgroups: those with a subluxated lens (n = 18) and those without (n = 21). Those groups also did not differ in either age (p = 0.95) or spherical refraction (p = 0.06) (Table 1). The mean Kmed value in the MFS eyes was significantly lower than in the control eyes (p = 0.02) (Table 2). Fifteen MFS eyes (38%) had a Kmed value below 41.5 D compared to three (8%) controls, which was significantly different (p = 0.0012). However, we found no significant difference in the mean Kmed value between the MFS eyes with and without lens subluxation (p = 0.87). MFS eyes had more corneal astigmatism compared to control eyes (p = 0.035) (Table 2). Nine MFS eyes (23%) but only two control eyes (5%) had corneal astigmatism exceeding 1.5 D (p = 0.025). The same nine MFS eyes also had a subluxated lens, and eight of them had with-the-rule astigmatism (minus cylinder in 0 ± 15 degrees or 180 ± 15 degrees) not correlated with age (range 13–71 years). One eye had oblique astigmatism. MFS eyes with a subluxated lens had generally significantly (p =0.0002) more corneal astigmatism than those without a subluxated lens (Table 2). Despite high corneal astigmatism, no MFS or control eyes had keratoconus, which was determined by conventional slit-lamp examination and corneal topography imaged with Orbscan (Krumeich & Kezirian 2009). The mean corneal thickness at the thinnest point was significantly decreased in MFS eyes compared to control eyes (p = 0.007) (Table 2). The number of MFS eyes with a corneal thickness below 500 μm was significantly higher than control eyes (24 MFS eyes (62%) versus 10 control eyes (25%) (p = 0.01). However, the difference in the mean corneal thickness at the thinnest point between the MFS eyes with and without a subluxated lens was not significant (p = 0.29) (Table 2). Thirteen MFS eyes with a subluxated lens (72%) and 11 MFS eyes without a subluxated lens (52%) had corneal thickness below 500 μm at the thinnest point (p = 0.32). No significant difference in ECD was found between the MFS eyes and control eyes (p = 0.66) (Table 2). There was no significant difference in the ECD between MFS eyes with and without a subluxated lens (p = 0.22). Some suggested diagnostic values in corneal changes and their association with MFS (Table 3) show that a Kmed value below 41.5 D and pachymetry below 500 μm were significantly associated with MFS. The association of the same findings with lens subluxation in MFS eyes is shown in Table 4, which showed that these changes had no significant association with lens subluxation in MFS eyes. This study showed that both K value and corneal thickness are decreased in MFS. However, the ECD did not differ significantly from the control population. These three parameters did not differ significantly between MFS eyes with and without lens subluxation. Even though a flat cornea is a minor criterion of MFS, the K value required for the diagnosis has not been well defined. Our results showed significantly decreased K values in MFS eyes, whereas the control eyes had K values similar to those in previous studies of healthy populations (Liu et al. 1999; Goto et al. 2001). Previous studies have shown that MFS eyes in many cases have Kmed values below 41.5 (Maumenee 1981; Sultan et al. 2002; Heur et al. 2008). In the current study, a significantly higher number of MFS eyes had Kmed values below 41.5 D than in the control group. Our results and the previous ones implied that Kmed value of 41.5 D or less could be a positive sign of MFS. Interestingly, we also found higher corneal astigmatism in the MFS eyes than in the control eyes. Furthermore, all MFS eyes with high corneal astigmatism had a subluxated lens, but the association between these two findings is unclear. It has been suggested that a deviation of the eye might cause measurements with higher values of corneal astigmatism. A subluxated lens could cause this kind of deviation. However, in a study on refractive changes owing to oblique viewing, clinically insignificant changes were seen on total refraction, as well as astigmatism or higher grade of aberrations (Radhakrishnan & Charman 2007). We therefore hypothesize that the same eyes with defects affecting zonular stability (Heur et al. 2008) also have defects in the connective corneal tissue, causing increased corneal astigmatism. In normal populations, the dominant astigmatism in the higher age groups is against the rule (Baldwin & Mills 1981; Lam et al. 1999; Gudmundsdottir et al. 2000; Asano et al. 2005). In the light of our results, however, it seems that the typical corneal astigmatism in MFS is with the rule, with vertical corneal steepening, regardless of age. This is an interesting finding, because the typical subluxation in MFS also is in superior direction. This could mean that in MFS eyes with lens subluxation, there are some structural changes in the same corneal meridians and zonular system. Keratoconus is at times reported to be associated with MFS, but a few case reports have been published (Shah et al. 2005), and to the best of our knowledge, no studies have reported a clear association between these two diagnoses. No MFS eyes with high corneal astigmatism in the current study had eccentric steepening or corneal changes typical of keratoconus on slit-lamp examination or corneal topography, which agreed with the findings of Maumenee in a group of 160 patients with MFS (Maumenee 1981). Unlike a flat cornea, decreased corneal thickness is not currently a criterion of MFS. Some previous studies did not report abnormalities in corneal thickness (Maumenee 1981; Setala et al. 1988), whereas recent studies reported decreased corneal thickness in MFS (Sultan et al. 2002; Heur et al. 2008). We also found significantly lower pachymetry values among MFS eyes and, in many cases, corneal thicknesses below 500 μm. These corneas were generally thin with no local thinning as in keratoconus. Further studies are needed to confirm the decreased corneal thickness to determine whether it is a positive sign of MFS. Setala et al. (1988) previously assessed ECD in MFS and reported results similar to ours, with no significant difference in ECD in MFS eyes, regardless of the presence or absence of lens subluxation. Some studies also have reported alterations in endothelial morphology in MFS (Setala et al. 1988; Sultan et al. 2002; Iordanidou et al. 2007). In the current study, we did not study cell morphology indices, but we did not find a significant difference in ECD values between MFS eyes and control eyes, which could imply that measuring ECD does not aid in the diagnosis of MFS. Decreased K value and corneal thickness occurred as often in MFS eyes independently of lens subluxation. This could indicate that these corneal changes are connected to MFS itself rather than lens subluxation. We have reported previously that also accommodation in MFS eyes is independent of subluxation (Konradsen et al. 2009). Considering that about 40% of eyes with MFS do not show signs of lens subluxation, the corneal changes we reported in the current study could be positive markers of MFS, which could enable earlier and more accurate diagnosis of the syndrome. Even though the number of participants in the current study was small, this group represented a relatively large proportion of the known cases in the region with this rare disease. Our study confirmed the results of many previous studies of MFS and also provided some indication of diagnostic values for corneal changes in MFS eyes. The subjects with MFS in the current study were matched for age and refraction with the controls, which should eliminate the differences we found caused by age- or refraction-related factors. Our results showed that both K values and corneal thickness are significantly decreased in MFS compared to controls independent of lens subluxation. Because the cardinal ocular finding, lens subluxation, is not present in all MFS cases, these corneal findings could be positive signs of the syndrome, enabling earlier and more accurate diagnosis. It also seems that high corneal astigmatism is associated with lens subluxation in MFS. We suggest that signs of subluxation should be identified in individuals with known or suspected MFS with high corneal astigmatism, especially with with-the-rule astigmatism." @default.
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• W2062877993 date "2010-09-09" @default.
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• W2062877993 title "Corneal curvature, pachymetry, and endothelial cell density in Marfan syndrome" @default.
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