الفهرس 
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Abstract
Keratoconus is the most common ectatic disorder that affects the cornea and leads to progressive thinning and steepening with refractive changes in the form of increasing myopia and irregular astigmatism resulting in compromised vision.
Corneal collagen cross-linking CXL introduced in 1998 and approved by FDA in 2016 is considered the main treatment designed to increase the rigidity of the cornea and prevent progression of ectatic disorders to preserve visual acuity.
Intrastromal corneal ring segments (ICRS) are pieces of synthetic material inserted into corneal stroma to modify corneal curvature and produce intended refractive changes. It is believed that ICRS implantation improves the refractive and visual outcomes. The combination of ICRS with CXL is important to ensure long-term stability and maintain the visual and refractive gain.
The aim of this study is to evaluate the short and long-term outcomes of simultaneous corneal collagen cross-linking and Femtosecond laser-assisted intracorneal stromal ring segments implantation for the management of keratoconus.
The current study was conducted on 2 groups; group A (retrospective group) contains 50 eyes of 37 patients; 16 males and 21 females with mean age of 28.04 ± 5.38. in group A we revised the data records of the patients with follow-ups for at least 5 years. group B (prospective group) contains 10 eyes of 8 patients; 3 males and 5 females with mean age 29.69 ± 6.27 with keratoconus treated with ICRs with CXL and followed for 6 months.
In group A, the majority (82%) of patients needed two ring segments. There was statistically significant improvement of both UCVA & BCVA after three months and stable after five years as compared to preoperative data. The differences in VA between three months and five years follow-up visits were statistically significant regarding BCVA while it was insignificant statistically regarding BCVA.
It was found that both cylindrical error, spherical equivalent, and keratometric readings (K1, K2) were improved significantly after three months and five years while the changes between both periods were insignificant except for K2 which showed a statistically significant decrease between after five years
Corneal thickness was found to show a statistically significant decrease in 3 months follow-up. The changes after three months and up to five years were statistically insignificant.
In group B (Prospective group) also the majority (80%) of patients needed two ring segments. There was a statistically significant improvement of both UCVA & BCVA after six months follow-up.
It was found that both cylindrical error, spherical equivalent, and keratometric readings (K1, K2) were improved significantly after six months follow-up period. Corneal thickness was found to show a statistically significant decrease in six months follow-up.
We found that changes in the Q value of the corneal front, as a measure of corneal asphericity, were not statistically significant. The changes in the coma, as an important example of higher-order aberrations, were found to be improved with statistically significant values indicating improvement of higher-order aberrations by ICRS implantation.
In conclusion, we found that combined corneal collagen cross-linking with ICRS was able to increase corneal rigidity and prevent the progression of keratoconus. ICRS was found to be effective in improving visual outcome, refractive error, keratometric readings, and higher-order aberrations. The positive outcomes of combined ICRS with CXL appear to be stable for five years follow-up.