| Abstract |
Introduction
Keratoconus is an ophthalmic condition which leads in distortion of the corneal surface resulting in gradual optical acuity loss. Corneal cross-linking (CXL) is a new alternative, minimally invasive treating method designed to increase the rigidity, the structural integrity and the stability of the cornea, preventing the progression of keratoconus.
Purpose
a. The safety evaluation of a new therapeutic protocol in CXL (duration 10 min with intensity 9 mW/cm2).
b. The evaluation and comparison of the demarcation line’s depth in the corneal stroma using AS-OCT after CXL with two different therapeutic protocols (duration 30 mins with intensity 3mW/cm2 and duration 10 mins with intensity 9mW/cm2)
A. Safety after high intensity CXL
Sample and method
In the study participated 10 eyes (9 patients, 5 men and 4 women) with progressive keratoconus. The participation criteria were: progressive keratoconus, corneal thickness > 400 μm, lack of central or paracentral subepithilial or stromatic scar, non presense of pregnancy and breast feeding, no ophthalmic operations in anterior segment in patients’ history, absence of autoimmune diseases or collagen diseases, active ophthalmic infection and severe dry eye.
All patients underwent CXL of 10 mins duration with radiation intensity 9 mW/cm2.
Results
No intraoperative or postoperative complications occurred in any patient. Patients’ mean age was 24,9±5,24. ECD was 2688±130 preoperatively and 2640±127 three months postoperatively presenting no statistically significant change. CDVA improved from 0,19±0,20 preoperatively to 0,10±0,16 three months postoperatively, though this improvement was not statistically significant. None of the eyes lost any
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CDVA lines. Mean K steep was significantly decreased from 48,04±2,57 preoperatively to 46,51±2,81 three months postoperatively, while mean K flat was decreased from 43,88±1,67 preoperatively to 43,55±1,88 three months postoperatively, though this was not statistically significant.
B. Demarcation line of corneal stroma after the application of classic CXL protocol and high intensity CXL protocol, determined by AS-OCT.
Sample and method
In the study participated 21 eyes (16 patients, 9 men and 7 women) with progressive keratoconus. The participation criteria were: progressive keratoconus, age higher than 18 y, corneal thickness > 400 μm, no pathological findings in cornea or anterior segment, non presense of pregnancy and breast feeding.
9 eyes (7 patients) underwent CXL of 30 mins duration and radiation intensity 3mW/cm2 according to Dresden protocol (group 1), while 12 eyes (9 patients) underwent CXL of 10 mins duration and radiation intensity 9mW/cm2 (group 2). The collected data included patients’ age, gender, preoperative U/S corneal pachymetry, postoperative topography and AS-OCT examination in first postoperative month.
Results
No intraoperative or postoperative complications occurred in any patient. Mean patients’ age was 22,33±2,83 for group 1 and 23,17±3,41 for group 2. Both groups showed similarities of age, preoperative pachymetry and K steep and flat (demarcation line in corneal stroma was easily seen using AS-OCT in all eyes). Mean demarcation line depth was 350,78±49,34 μm for group 1 and 288,46±42,37 μm for group 2. The difference of the demarcation line depth between the two groups was statistically significant.
Conclusions
According to the photochemical reciprocity law of Bunsen-Roscoe it is possible to have the same photochemical result (including CXL) by decreasing the duration and respectively increasing the intensity of the radiation, so that the total energy amount remains stable. Rivoflavin application with iontophoresis for faster stroma saturation and high intensity UVA radiation usage decreases the operation
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time needed. In high intensity CXL (9 mW/cm2 for 10 mins) no significant changes in ECD were noticed, no intraoperative or primary postoperative complications. CDVA remained stable postoperatively, while no eye lost any CDVA lines. Mean K steep decreased significantly, while mean K flat was not significantly changed postoperatively.
The depth of the demarcation line in corneal stroma after CXL application shows the treatments’ efficiency. CXL of 30 mins duration and 3 mW/cm2 intensity (group 1) could be more efficient than the CXL of 10 mins duration and 10 mW/cm2 intensity (group 2). In contradiction, the deeper demarcation line in corneal stroma could increase the possibility of corneal damage and toxicity of endothelial cells. Corneal stroma demarcation line should be seen in the same depth in both groups, however our results show that there is a significant difference between the two groups.
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