الفهرس 
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Abstract
Collagen cross linking is an established treatment for keratoconus and other ectatic corneal disorders, with proven efficacy in slowing or halting disease progression. In the procedure, the induction of cross-links between intrastromal collagen fibrils by photosensitizer riboflavin and ultraviolet A (UV-A) irradiation confers added corneal rigidity and strength, thereby stabilizing the ectatic process.
There has been extensive research on expanded indications and various modifications of the procedure evolved from the original “Dresden protocol” for conventional crosslinking, including accelerated protocols with increased irradiance over shorter duration, treatment through an intact epithelium (“epi-on”), as well as combination therapy with intracorneal ring segments and refractive surgery across different crosslinking platforms.
Of interest, accelerated or high-fluence protocols present a promising alternative to the time-consuming conventional crosslinking. The potential advantages include reduced exposure time, better patient compliance and lower infection risk. According to Bunsen-Roscoe’s law of reciprocity, an increased intensity of UV-A irradiation coupled with reduced exposure time theoretically delivers a total energy dose to the tissue equivalent to that in conventional treatment, with similar biological effect.
This study aimed to evaluate the changes in corneal and lenticular density following corneal cross-linking (CXL) with conventual vs. enhanced protocol.
This is a prospective randomized controlled clinical trial including all patients with keratoconus undergoing corneal cross-linking. 20 eyes with conventional vs 20 eyes with enhanced method. All patients attended to out patients clinic unite, Menoufia university hospital, Shebin El Kom during the period study from August 2019 till June 2020.
Inclusion Criteria: included age between 15 and 40 years, phakic patients with clear lenses, confirmed bilateral KC based on clinical and topography findings, bilateral minimum corneal thickness of 400 μm as measured with the pentacam and maximum keratometry of 60 D in each eye based on pentacam readings.
Exclusion criteria: included non-progressive keratoconus, Pseudophakic or cataract, corneal thinnest point <400 μm, corneal scarring in either eye, previous eye surgery, ocular surface or tear problems and coexistence of ocular pathology other than KC.
All of the patients were subjected to the following:
Preoperative evaluation: All patients were subjected to:
Full clinical history
Ophthalmic examination: included the best corrected visual acuity, Slit-lamp biomicroscopy and Fundus examination.
The Pentacam Scheimpflug system was used to measure corneal thickness, thinnest location, steepest k and measure objectively the corneal and lens densitometry values. The CXL procedure was performed using CCL-365 vario and VEGA.
Summary
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Post-operative evaluation: During the follow-up visits at 1 and 3 months UDVA, CDVA were clinically assessed, slit lamp examination, cornea and lens densitometry. Also, the Pentacam K-max, thinnest pachymetry and the contrast sensitivity were recorded.
Results of the current study could be summarized as follow:
There were no statistically significant differences between the studied groups regarding age, sex and eye side (p>0.05).
The preoperative spherical equivalence was decreased after 3 and 6 months postoperatively, in group I and II, respectively. K max was decreased after 3 and 6 months postoperatively, in group I and II, compered preoperative. The corneal thinnest location thickness was decreased after 3 and 6 months postoperatively, in group I and II, compered preoperative.
There were no statistically significant differences between the two studied groups regarding corneal densitometry and lens density (p>0.05). The correlation between thinnest location and K max not reached to statistically significant level (p>0.05). Exception in group I, thinnest location was significantly negative correlated with K max preoperative (p=0.008) and 1month postoperatively (p=0.046). As well as thinnest location was significantly positive correlated with corneal density 180 at 6 months postoperative (p=0.001).
Regarding, contrast sensitivity. The average one-month CS for all patients was increased after three months postoperatively and then increased at the final follow up examination after 10 min than 30 min.
Contrast sensitivity was not significant difference throughout the study period among the studied groups.