Keratokonuslu Hastaların Göz Yaşı Lizozomal Enzim Düzeyleri ve Konfokal Mikroskopi Bulgularının Kontrol Grubu ile Karşılaştırılması
Özet
Özturan İ. Comparison of Lysosomal Enzyme Levels in Tear Fluid and Confocal Microscopy Findings in Patients with Keratoconus with a Control Group, Ankara 2024.
The aim of this study is to compare the lysosomal enzyme levels in tear samples and corneal findings in confocal microscopy in patients diagnosed with keratoconus with a healthy control group. A total of 51 patients with keratoconus aged between 18- 45 years, who had not undergone penetrating keratoplasty and had no other ocular or systemic diseases, and 51 healthy controls were evaluated.
Tear samples were applied to Guthrie paper. In these samples, the enzymes glucocerebrosidase, lysosomal acid α-glucosidase, galactocerebrosidase, alpha- galactosidase A, alpha-L-iduronidase, and acid sphingomyelinase were studied using the Liquid Chromatography-Mass Spectrometry (LC-MS/MS) method. In vivo confocal microscopy findings were evaluated.
The two groups were similar in terms of age and gender. Corneal epithelial cell density, total nerve density, and long nerve fiber count in patients with keratoconus were lower compared to the healthy control group, but this difference was not statistically significant (p=0.196, p=0.251, and p=0.211, respectively). The percentage of epithelial polymorphism was higher in keratoconus patients compared to the healthy control group, but this result was not statistically significant (p=0.332).
Among the lysosomal enzymes evaluated in the tear fluid of keratoconus patients, glucocerebrosidase was significantly higher than in the control group (p=0.020). Lysosomal acid α-glucosidase, galactocerebrosidase, alpha-galactosidase A, and alpha-L-iduronidase were higher in keratoconus patients compared to the control group, but these differences were not statistically significant (p=0.058, p=0.271, p=0.130, p=0.175, respectively). Acid sphingomyelinase was significantly higher in the control group compared to keratoconus patients (p=0.027).
In keratoconus patients with a family history, the levels of glucocerebrosidase and galactocerebrosidase in tear fluid were higher compared to those without a family history, but this result was not statistically significant (p=0.673, p=0.464,
respectively). In the group with corneal cross-linking surgery, all tear enzymes (lysosomal acid α-glucosidase, galactocerebrosidase, acid sphingomyelinase, glucocerebrosidase, alpha-galactosidase A, alpha-L-iduronidase) were lower in those who had undergone the operation ≤20 months ago compared to those who had it >20 months ago, but this difference was not statistically significant (p=0.723, p=0.465, p=0.662, p=0.723, p=0.491, p=0.917, respectively).
The anterior stromal keratocyte density in the group with corneal cross-linking surgery >20 months ago was higher compared to the group with ≤20 months, but this result was not statistically significant (p=0.431). Posterior stromal keratocyte density was higher in the group with corneal cross-linking surgery >20 months ago compared to the other group, and this result was statistically significant (p=0.04).
In advanced stage keratoconus patients (stage 2, 3, 4 according to the Amsler- Krumeich Classification), the percentage of epithelial and endothelial polymorphism was higher compared to early-stage keratoconus patients (stage 1 according to the Amsler-Krumeich Classification), but this difference was not statistically significant (p=0.126 and p=0.126, respectively). Long nerve fiber, total nerve fiber, total nerve fiber density, and nerve tortuosity were lower in advanced stage keratoconus patients compared to early stage keratoconus patients, but this difference was not statistically significant (p=0.746, p=0.496, p=0.772, p=0.277, respectively). When all participants in the study were considered, glucocerebrosidase (enzyme 4), which was found to be significantly elevated in the patient group, showed a positive correlation with the percentage of endothelial polymegatism (r=0.220, p=0.026). In the patient group, acid sphingomyelinase (enzyme 3), which was found to be significantly lower, showed a positive correlation with the number of long nerve fibers (r=0.198, p=0.046). When all participants in the study were considered, glucocerebrosidase (enzyme 4), which was found to be significantly elevated in the patient group, showed a positive correlation with the percentage of endothelial polymegatism (r = 0.220, p = 0.026). In the patient group, acid sphingomyelinase (enzyme 3), which was found to be significantly decreased, showed a positive correlation with the number of long nerve fibers (r = 0.198, p = 0.046).
The changes in lysosomal enzyme levels in the tear fluid of eyes with keratoconus support the changes in degradative enzymes, which are thought to be responsible for the etiopathogenesis of keratoconus. These enzymes can be useful in evaluating the genetic background of keratoconus, early diagnosis, and treatment targets. Although confocal microscopy is not primarily used in the diagnosis of keratoconus, it provides clues that keratoconus affects all layers of the cornea and can be a non-invasive examination method that can be preferred as an alternative to basic diagnostic/follow-up methods.
