Tissue inhibitor of metalloproteinase 4 in aqueous humor of patients with primary open angle glaucoma, pseudoexfoliation syndrome and pseudoexfoliative glaucoma and its role in proteolysis imbalance.

BACKGROUND: To quantify the levels of tissue inhibitor of metalloproteinase 4 (TIMP4) and its ratios with free metalloproteinases (MMP) in the aqueous humor of patients with primary open angle glaucoma (POAG), pseudoexfoliation syndrome (PXS) and pseudoexfoliative glaucoma (PXG) and to evaluate a possible imbalance between MMPs and TIMPs in these samples. METHODS: Free MMP2, MMP3, MMP9, TIMP1, TIMP2, TIMP4 concentrations and active levels of MMP2 and MMP3 were determined with immunoassay ELISA and activity assay kits in 168 aqueous samples. RESULTS: TIMP4 was elevated in glaucoma patients(POAG: 0.95 ± 0.49 PXG: 1.28 ± 1.38 pg/ml. p < 0.001). POAG, PXS and PXG samples demonstrated higher MMP2, TIMP1 and TIMP2 concentrations (p < 0.001). Samples from the PXS and PXG groups had a lower total/active MMP2 ratio (p < 0.004 and p < 0.008 respectively). Stoichiometric analysis showed an overbalance of TIMPsover MMPs in both POAG & PXG groups,especially of TIMP4. CONCLUSION: TIMP4 elevation is a novel finding in glaucomatous eyes. A disregulation of extracellular matrix homeostasis is suggested in POAG, PXS and PXG.

Comparison between Pascal dynamic contour tonometer and Goldmann applanation tonometer after different types of refractive surgery.

BACKGROUND: To evaluate and compare the recorded IOP values of the Pascal dynamic contour tonometer (PDCT) and the Goldmann applanation tonometer (GAT) after photorefractive keratectomy (PRK) and laser in situ keratomileusis (LASIK). METHODS: Three groups of 84, 182 and 43 patients each were treated by PRK for myopia, LASIK for myopia and LASIK for hyperopia respectively. Intraocular pressure (IOP) measurements were performed in all eyes 1 day before and 1, 3, 6 and 12 months after treatment with PDCT and GAT. Ultrasound pachymetry was performed in all eyes preoperatively and at 1st month postoperatively. RESULTS: Preoperatively and postoperatively, GAT readings were lower than PDCT in all groups (all p < 0.05). Postoperatively in the PRK group, compared to the preoperative value, the mean differences of IOP recorded with GAT at 1st, 3rd, 6th and 12th month were -1.4 mmHg, -1.7 mmHg, -1.7 mmHg and -1.9 mmHg respectively (all p < 0.05). In the myopic LASIK group; the corresponding values with GAT were -3.6 mmHg, -3.6 mmHg, -3.6 mmHg and -3.5 mmHg (all p < 0.05), while in the hyperopic LASIK group the corresponding values were -1.1 mmHg, -0.7 mmHg, -1.1 mmHg and -0.9 mmHg (all p < 0.05). The mean IOP difference (GAT-PDCT) for myopic PRK, myopic LASIK and hyperopic LASIK were respectively -3.8 mmHg, -4.1 mmHg and -1.5 mmHg at the 12-month follow-up. No statistically significant changes were found for any group with the PDCT. CONCLUSIONS: GAT-determined IOP values were significant lower at all time-points after hyperopic LASIK, as well as myopic PRK or LASIK. The Pascal tonometry values remained unaffected for all groups.

Evaluation of the retinal nerve fiber layer measurements, after photorefractive keratectomy and laser in situ keratomileusis, using scanning laser polarimetry (GDX VCC).

BACKGROUND: To evaluate the impact of photorefractive keratectomy (PRK) and laser in situ keratomileusis (LASIK), on retinal nerve fiber layer (RNFL) measurements, by means of scanning laser polarimetry (SLP) GDx VCC (with variable corneal compensation). METHODS: Two groups of 119 myopic patients each were treated by PRK and LASIK respectively; one eye of each patient was randomly selected for the study. RNFL measurements (around the entire calculation circle) was performed in all eyes 1 day before and 1, 3, 6 and 12 months after treatment by using SLP GDx VCC. Corneal compensation was performed in all eyes preoperatively, and in every examination step postoperatively, in order to neutralize the new corneal birefringence. RESULTS: No statistical differences were found between the PRK and LASIK groups, in all preoperative and postoperative RNFL measurements. Only the p values for CCT and mean K-readings preoperatively were statistically significant. CONCLUSIONS: PRK and LASIK do not seem to influence the RNFL measurements at 1st, 3rd, 6th and 12th postoperative months when measured with SLP GDx VCC. The corneal compensation reset is necessary in every step of the examination in order to have reproducible results.

Combined photorefractive keratectomy and cross-linking. Pushing the limits.

Correction of refractive error through laser-assisted means has soared in popularity in recent years, allowing it to become an increasingly routine surgical procedure. Technique refinement and adjustments resulted in laser-assisted refractive surgery to be combined with treatments such as collagen cross linking (CXL). This has broadened safety parameters and widened the treatment boundaries. Laser correction combined with CXL has been advocated in the treatment of high refractive errors as a safe option for full refractive correction while increasing corneal biomechanical stability. We present a complicated case where a young female patient with a preoperative best-corrected visual acuity (BCVA) of 20/20 in each eye was fully corrected by excimer laser followed by CXL. Factors potentially leading to inflammation, such as ocular surface disease, in addition to laser treatment and CXL, resulted in persistent epithelial defect followed by corneal melt and subsequent thinning. After the treatment, the patient relies on rigid gas-permeable contact lenses, achieving a BCVA of 20/25 and 20/23 in the right eye and left eye, respectively.