[Biomechanical properties of the cornea as predictors of the effectiveness of selective laser trabeculoplasty]

[Comparative evaluation of hypotensive effectiveness of topical monotherapy and selective laser trabeculectomy]

PURPOSE

Comparison of the hypotensive effects of selective laser trabeculoplasty (SLT) and drug therapy in patients with newly diagnosed primary open-angle glaucoma (POAG) and ocular hypertension.

MATERIAL AND METHODS

Thirty patients (30 eyes) with newly diagnosed ophthalmic hypertension or POAG were observed. Patients of the 1st group (15 eyes) underwent standard SLT as a starting treatment, patients of the 2nd group (15 eyes) were prescribed monotherapy with a prostaglandin analog. Corneal compensated intraocular pressure (IOPcc) was measured for each patient using Ocular Response Analyzer («Reichert Technologies», USA). The observation period lasted 6 months.

RESULTS

During the 6-months follow-up, tafluprost was found to effectively reduce IOP in 93.3% of cases, SLT - in 73.3% of cases. There were no statistically significant differences in hypotensive effectiveness between the two compared treatments, which amounted to 27.9-28.5% reduction from the baseline values.

CONCLUSION

Selective laser trabeculectomy and topical drug therapy have shown similar hypotensive effectiveness during the 6-months follow-up when used as the initial therapy for POAG.

[Coefficient of biomechanical stress in assessment of the degree of intraocular pressure compensation]

Intraocular pressure is the one modifiable factor, which correct assessment and normalization initiates the treatment of glaucoma. The accuracy of its measurement by traditional methods depends on biomechanical properties of the fibrous tunic of the eye, which in modern clinical practice are most successfully studied by the method of bidirectional applanation of the cornea using the Ocular Response Analyzer (ORA). Mathematical integration of the parameters it measures makes it possible to calculate the coefficient of biomechanical stress (K_bs) that characterizes changes in the fibrous tunic of the eye induced by intraocular pressure, and serves as a criterion for intraocular pressure compensation.

PURPOSE

To determine the range of normal values of the K_bs coefficient, and to evaluate its specificity and sensitivity as a criterion for the degree of intraocular pressure compensation.

MATERIAL AND METHODS

Two consecutive studies on representative clinical material were used to determine the range of normal K_bs values in patients without significant ophthalmic pathologies (400 patients, 800 eyes) and establish the sensitivity and specificity of the coefficient in the diagnosis of glaucoma in patients with newly diagnosed glaucoma (673 patients, 1346 eyes). The age and gender composition of patients in both study groups was similar.

RESULTS

The cut-off value for K_bs is 1.0. In the range of values from 1.0 to 1.09, additional risk factors for glaucoma progression must be taken into account to assess intraocular pressure compensation. In cases when K_bs is equal to or exceeds 1.1, the intraocular pressure is considered elevated and a high risk of disease development or progression is predicted. In glaucoma patients with uncompensated intraocular pressure, the specificity of K_bs is 81.5%, the relative specificity (including the borderline range) is 98%. With K_bs values over 1.1, its specificity reaches 100%.

CONCLUSION

The performed clinical and statistical analysis demonstrates high sensitivity and specificity of the biomechanical stress coefficient in the diagnosis and treatment of glaucoma.

Factors affecting the corneal endothelium after selective laser trabeculoplasty in primary open angle and angle closure glaucoma

Purpose

To study the factors affecting the corneal endothelium after selective laser trabeculoplasty (SLT) in primary open angle glaucoma (POAG) and primary angle closure glaucoma (PACG).

Method

This prospective interventional study included 56 patients (56 eyes) with POAG and 55 patients (55 eyes) with PACG. All participants received a standard SLT session. Patients with PACG were pretreated with laser peripheral iridotomy for at least 2 months before SLT. Corneal endothelium cell count (ECC), pleomorphism and polymegathism were measured before SLT, as well as at the increments of 1 hour, 1 day, 1 week, 1 month, 3 months and 6 months following SLT using confocal microscopy. A multiple regression analysis was applied to detect the factors affecting the ECC in the long-term post-SLT period.

Results

In both groups, the mean ECC significantly decreased from the baseline after SLT. While in POAG, corneal endothelium recovered within 1 month, in PACG, its damage persisted throughout the whole follow-up period.

According to the multiple analysis, baseline ECC (β=0.891, p=0.000 in POAG and β=0.706, p=0.000 in PACG) and age (β=−0.227, p=0.000 in POAG and β=−0.196, p=0.000 in PACG) were the common risk factors affecting ECC in both glaucoma forms, while the initial anterior chamber depth (β=0.254, p=0.000), only in PACG. The duration of glaucoma treatment (β=−0.317, p=0.043 in POAG and β=−0.302, p=0.047 in PACG) and pigmented deposits on the corneal endothelium in PACG (β=−0.326, p=0.019) were the risk factors determined in the univariate analysis.

Conclusion

Age and the baseline ECC are the risk factors for corneal endothelium damage after SLT in POAG and PACG. Shallow anterior chamber may affect corneal endothelium in PACG. These data should be considered when choosing an algorithm for glaucoma treatment.