Posterior corneal astigmatism changes in cases with keratoconus

Background: keratoconus is bilateral [usually asymmetrical], progressive, non inflammatory, cone like anterior protrusion of the cornea involving the central and the inferior para central areas that results in corneal ectasia, astigmatism and diminution of vision. It usually seen after puberty, with incidence of 1 in 2000 of general population, the major benefit of corneal tomography is the measurement of the posterior corneal surface, because the posterior surface contributes minimally to the overall refractive power of the eye [due to the minimal difference between the index of refraction of the cornea and aqueous] it was considered less important both diagnostically and therapeutically. The posterior cornea, however, is an earlier indicator of ectatic change or ectasia susceptibility

Aim of the Work: to determine the changes of posterior corneal astigmatism in cases with keratoconus

Patients and Methods: one hundred eyes of 50 patients were included in this retrospective, case control study which adhered to the tenets of the Declaration of Helsinki and was approved by the Ethics Committees of the Ain Shams University Hospitals. All patients included in the study provided informed consent, these cases were divided into: 1- Keratoconus group: comprised 50 eyes of 25 patients with keratoconus diagnosed on the basis of clinical and topographic signs and 2- Control group comprised 50 eyes of 25 normal candidates for refractive surgery

Results: the mean magnitudes posterior corneal astigmatism[PCA] were approximately 1 D, and The PCA values were significantly associated with the severity ofKeratoconus[KC], the posterior corneal surface was more affected in the early stages of KC

Conclusion: we found that the mean magnitudes PCA were approximately 1 D, and The PCA values were significantly associated with the severity of KC, the posterior corneal surface was more affected in the early stages of KC

Q value based ablation profile versus topography-guided lasik: a contralateral comparative study

Background: laser in situ keratomileusis [LASIK] has become the most widely used form of refractive surgery. The objective of this surgical technique was to modify the anterior corneal shape by ablating tissue from the stroma by means of the excimer laser after creating a hinged corneal flap. By this way, we were able to change the refractive status of the patient and provided better unaided vision. Continuous improvements in the original technique made the surgical procedure safer, more accurate and repeatable. These progressions are due to the development of novel technologies that are responsible for new surgical instrumentation, which makes the surgical procedure easier for the surgeon and better excimer laser ablation algorithms, which increase the optical quality of the ablation and thus the safety of the vision correction procedure

Aim of work: the aim of this study was to compare between Q value based ablation and topography-guided LASIK as regards safety, visual acuity, contrast sensitivity and high order aberration HOAs [spherical, coma and trefoil]

Patients and methods: this study was conducted on 60 eyes of 30 patients, thirty eyes of them underwent topography guided LASIK and the other 30 underwent Q value based ablation. Preoperative CDVA [corrected distant visual acuity] was done. Postoperative UDVA and CDVA were measured. Postoperative high order aberrations were measured 3 months postoperatively

Results: our results showed that there was no statistically significant difference between both groups as regards UDVA, spherical equivalent, high order aberrations and Strehl ratio point spread function

Conclusion: topographic guided ablation and Q value based groups provided essentially equivalent outcomes after myopic LASIK, with statistically insignificant difference between both profiles, although both laser profiles have been found to be effective, safe and predictable

Recommendations: we recommended doing more research regarding this study with larger number of cases and doing further investigations

Study of accuracy of corneal flap thickness by using femtosecond laser technology

Background: LASIK is the most popular surgery to correct the refractive errors nowadays. It is proved to be safe, effective and well predictable. It is important to produce a uniform flap with a narrow SD from the intended thickness. The Integrated optical pachymetry is a convenient and useful feature of the EX500 excimer laser which can be used to measure flap thickness intraoperatively

Objectives: this study aimed to detect the accuracy of Allegretto Wave light FS200[TM] platform in creation of different corneal flap thicknesses

Patients and Methods: sixty eyes of 30 myopic patients were included in our study, the patients were operated by 2 different surgeons from June 2017 till December 2017. The patients were distributed randomly into 3 studied groups. Group I [20 eyes with intended fs flap 100um], group II [20 eyes with intended fs flap 110um] and group III [20 eyes with intended fs flap 120um]. All participants were subjected to full medical history taking, uncorrected distance visual acuity, slit-lamp microscopy, corneal topography using oculus[registered] pentacam device, manifest and cycloplegic refraction, corrected distance visual acuity, fundus bio-microscopy examination using 90 D lens

Results: in this study 100 micro m thickness group [Group A] showed the lowest difference between the mean result and the intended flap [-0.35um] followed by the 120 micro m group [Group C] with difference of [-2.9um] between the mean result and the intended flap thickness followed by the 110 micro m group [group B] with the highest difference [-3.45um] from the intended flap thickness

Conclusion: the flaps made with the Wavelight FS200 femtosecond laser were predictable and uniform more predictable in group A than in group C and B, but with no statistical significance between the three studied groups [P=0.402]

Visual outcomes after topography-guided femtosecond LASIK in virgin eyes

Background: Laser vision correction has been established over the last 2 decades as a safe and effective intervention, with Laser-assisted in situ keratomileusis [LASIK], being one of the main techniques practiced globally. Femtosecond laser-assisted LASIK has become a popularized modification over the last decade and over the standard LASIK technique utilizing mechanical microkeratomes. A spherical ablation profiles performed by "wave front optimized" have been employed to reduce spherical aberration associated with myopic corrections

Aim of the Work: To evaluate the quality and efficacy of topography-guided femtosecond lasik in virgin eyes with myopia, hypermetropia and astigmatism

Patients and Methods: This comparative prospective study was conducted on 60 eyes of 30 Egyptian patients with comparing preoperative and postoperative outcomes. Eyes with myopia [-1.0 up to -8.0 diopters] or hypermetropia [+1.0 up to +5.0 diopters] or astigmatism [up to 5.0 diopters] or less. Eyes with central corneal thickness [CCT] of 500 microns or more. Eyes at risk for developing post-refractive corneal ectasia, such as keratoconus, keratoconus suspect, previous refractive surgery, corneal dystrophy, corneal guttae or opacities, any previous eye surgery e.g: pseudophakic patients, retinal detachment surgery, all eyes were normal for example no cataract, no glaucoma, no retinal pathology and no previous trauma

Results: Our study was performed on sixty eyes of thirty Egyptian patients. Sixty eyes of thirty patients underwent LASIK using T-CAT. Seventeen patients were females and thirteen were males. The average age of the patients was 24.8 year +/-5.45 standard deviation [SD]. The average spherical error was -3.09 D +/-2.33 SD. The average cylinder error was -1.02 D +/-1.02 SD

Conclusion: The results showed that there was statistically significant differences between preoperative BCVA and postoperative UCVA with a good safety and efficiacy profile with T-CAT lasik as no patient loss even one line and 80% of cases gaining at least one line postoperative. The surgery was associated with higher values of high order aberrations after surgery than before surgery

Effective phacoemulsification time in femto cataract in comparison to conventional cataract

Background: cataract surgery is one of the most commonly performed surgery in the world and the number of individuals with cataracts is predicted to reach 30 million by the year 20201. This number will continue to grow as the population ages. More and more patients pursue surgery at the early stage of cataract in order not to endure visual impairment. Phacoemulsification is the standard surgery procedure for cataract in the developed countries. In recent years, femtosecond laser [FSL] has been introduced into phacoemulsification cataract surgery to perform corneal incisions, capsulorhexis, and nuclear fragmentation. Numerous clinical studies have reported that using FSL to perform nuclear fragmentation before phacoemulsification significantly reduces the amount of ultrasound energy and effective phacoemulsification time [EPT] required in the surgery

Purpose: the goal of the present study is to assess the effect of FSL on effective phaco time in comparison to conventional phacoemusification procedure

Patients and Methods: a comparative study included 40 patients with senile cataract [nuclear cataract grade III or more] based on lens opacification classification system III [LOCSIII]. The patients were subdivided into 2 groups; group [A] included 20 patients with senile cataract underwent Femtosecond laser-assisted phacoemulsification [CATALYS FSL system [Abbott Medical Optics]] and group [B] included 20 patients with senile cataract underwent conventional phacoemulsification [ INFINTI phacoemulsification platform [Alcon]]. Effective phaco time had monitored and recorded in all patients

Results: as regarding conventional phaco group, mean EPT was 19.80+/-24.33 and in femto group, mean EPT was 1.05+/-1.28 with [p-value 0.001] which shows highly significant difference between the two groups

Conclusion: femto-second laser assisted cataract surgery reduces effective phacoemulsification time for grade 3 or more of nuclear cataract in comparison to manual procedure

Compliance with prescribed optical correction in cases of monocular aphadka in children

Compliance with prescribed optical corrections for monocular aphakia was investigated in 76 children aged below 15 years. In 56 children, contact lenses only had been prescribed; in 5, monocular aphakic glasses only; and in 15, both methods. Thus, contact lenses had been prescribed in 71 cases and monocular aphakic glasses had been prescribed in 20 cases. Only 44% of the children prescribed contact lenses and 55% of those prescribed aphakic glasses were wearing their optical correction when they attended the eye clinic. The parents of 27% of the contact lens group and 10% of the monocular aphakic glasses group indicated that there were no problems with the optical correction [s] for their children. Reasons given for failure to comply with contact lens wear included frequent falling out of lenses, loss of lenses, ocular redness and irritation, and others. In the case of patients prescribed monocular aphakic glasses, reasons included breakage of the glasses and refusal by the child to wear them most or all of the time. One factor in non-compliance is the concurrent requirement for occlusion of the good eye. The study also showed that there was often a significant delay between cataract surgery and obtaining the optical correction