Mutual comparative analysis:a new topography-guided custom ablation protocol referencing subjective refraction to modify corneal topographic data

Background:Several planning algorithms have been developed for topography-guided custom ablation treatment(T-CAT),but each has its own deficiencies.The purpose of this study is to demonstrate the potential of a novel mutual comparative analysis(MCA)informed by manifest refraction and corneal topographic data and the patient’s subjective perception in correcting ametropia.Methods:This retrospective review included patients with significant preoperative differences in the power or axis of astigmatism according to the manifest refraction and corneal topographic data(power>0.75 D and/or axis>10°).T-CAT planning was designed using MCA.Follow-ups were conducted for at least 6 months.Results:Seventy-nine patients(121 eyes)were included.The mean preoperative deviation in the astigmatic power and axis were 0.72±0.43 D and 20.18±23.68°,respectively.The average oculus residual astigmatism(ORA)was 0.81±0.32 D(range:0.08–1.66 D).Six months postoperatively,the mean spherical equivalent refraction was 0.04±0.42 D,and the mean cylinder was−0.27±0.24 D.The mean efficacy and safety indices were 1.10 and 1.15,respectively.The uncorrected distance visual acuity in 92%of the eyes was the same or better than the corrected distance visual acuity.The angle of error was±5°in 61%of eyes and±15°in 84%of eyes.Residual astigmatism was≤0.5 D in 91%of eyes.Optical quality and photopic contrast sensitivity did not change significantly(p>0.05),and the scotopic contrast sensitivity decreased at 3,6,and 12 cpd(p<0.05).The vertical coma and horizontal coma of the anterior corneal surface significantly decreased postoperatively but increased during follow-up.Conclusions:The MCA demonstrated safety,efficacy,accuracy,predictability,and stability and can be used as a complementary and feasible method for T-CAT.

Mutual comparative analysis:a new topography-guided custom ablation protocol referencing subjective refraction to modify corneal topographic data

Background:Several planning algorithms have been developed for topography-guided custom ablation treatment(T-CAT),but each has its own deficiencies.The purpose of this study is to demonstrate the potential of a novel mutual comparative analysis(MCA)informed by manifest refraction and corneal topographic data and the patient's subjective perception in correcting ametropia.Methods:This retrospective review included patients with significant preoperative diferences in the power or axis of astigmatism according to the manifest refraction and corneal topographic data(power>0.75 D and/or axis>10°).T-CAT planning was designed using MCA.Follow-ups were conducted for at least 6 months.Results:Seventy-nine patients(121 eyes)were included.The mean preoperative deviation in the astigmatic power and axis were 0.72±0.43 D and 20.18±23.68°,respectively.The average oculus residual astigmatism(ORA)was 0.81±0.32 D(range:0.08-1.66 D).Six months postoperatively,the mean spherical equivalent refraction was 0.04±0.42 D,and the mean cylinder was-0.27±0.24 D.The mean efficacy and safety indices were 1.10 and 1.15,respectively.The uncorrected distance visual acuity in 92%of the eyes was the same or better than the corrected distance visual acuity.The angle of error was±5°in 61%of eyes and±15°in 84%of eyes.Residual astigmatism was≤0.5 D in 91%of eyes.Optical quality and photopic contrast sensitivity did not change significantly(P>0.05),and the scotopic contrast sensitivity decreased at 3,6,and 12 cpd(P<0.05).The vertical coma and horizontal coma of the anterior corneal surface significantly decreased postoperatively but increased during follow-up.Conclusions:The MCA was demonstrated safety,ficacy,accuracy,predictability,and stability and can be used as a complementary and feasible method for T-CAT.

Target Z-axis Optimized LASIK for 2 Cases with Decentered Ablation

Purpose: To report target z-axis optimized LASIK treating for two eyes from two patients with decentered ablation. Methods: The LaserSight AstraPro2.2 Z software is a topography-guided custom ellipsoid ablation platform. LASIK with target z-axis optimization was performed to restore pre-operative visual axis using a LaserSight SLX excimer laser (version 5.3,300 Hz). Results: During preoperative examination, the uncorrected visual acuity (UCVA) was 0.5 in both eyes, and the best spectacle-corrected visual acuity(BSCVA) was 1.0 and 0.8. The decentered ablation zones were diagnosed with LaserSight AstraMax topography. Following target z-axis microtranslation, fifteen and eight μm of central corneal tissues were preserved in the two eyes respectively,the UCVA was 1.2 in both eyes, and secondary ablation zones were both centered on the visual axis.Topography maps and UCVA were stable in both eyes at the time of final follow-up. Conclusions: Using target z-axis optimized LASIK with the LaserSight AstraPro Planner 2.2 Z customized ablation software was an effective method to modify decentered ablation and restore the visual axis.

Assessment of refractive astigmatism and simulated therapeutic refractive surgery strategies in coma-like-aberrations- dominant corneal optics

Background:The aim of the study is to raise the awareness of the influence of coma-like higher-order aberrations(HOAs)on power and orientation of refractive astigmatism(RA)and to explore how to account for that influence in the planning of topography-guided refractive surgery in eyes with coma-like-aberrations-dominant corneal optics.Methods:Eleven eyes with coma-like-aberrations-dominant corneal optics and with low lenticular astigmatism(LA)were selected for astigmatism analysis and for treatment simulations with topography-guided custom ablation.Vector analysis was used to evaluate the contribution of coma-like corneal HOAs to RA.Two different strategies were used for simulated treatments aiming to regularize irregular corneal optics:With both strategies correction of anterior corneal surface irregularities(corneal HOAs)were intended.Correction of total corneal astigmatism(TCA)and RA was intended as well with strategies 1 and 2,respectively.Results:Axis of discrepant astigmatism(RA minus TCA minus LA)correlated strongly with axis of coma.Vertical coma influenced RA by canceling the effect of the with-the-rule astigmatism and increasing the effect of the against-the-rule astigmatism.After simulated correction of anterior corneal HOAs along with TCA and RA(strategies 1 and 2),only a small amount of anterior corneal astigmatism(ACA)and no TCA remained after strategy 1,while considerable amount of ACA and TCA remained after strategy 2.Conclusions:Coma-like corneal aberrations seem to contribute a considerable astigmatic component to RA in eyes with coma-like-aberrations dominant corneal optics.If topography-guided ablation is programmed to correct the corneal HOAs and RA,the astigmatic component caused by the coma-like corneal HOAs will be treated twice and will result in induced astigmatism.Disregarding RA and treating TCA along with the corneal HOAs is recommended instead.

Higher incidence of steroid-induced ocular hypertension in keratoconus

Background:To compare intraocular pressure(IOP)changes following topical dexamethasone administration for 1 month in keratoconic versus normal eyes.Methods:This is a retrospective,single-center,non-randomized case series evaluation of 350 eyes.Two groups were formed:normal/control Group A(n_(A)=73),eyes that underwent excimer laser photorefractive keratectomy;and keratoconic(KCN)Group B(n_(B)=277),eyes that were subjected to partial laser photorefractive keratectomy combined with collagen cross-linking(The Athens Protocol).All eyes received the same post-operative regimen of topical dexamethasone 0.1%for at least 1 month.Goldmann applanation tonometry IOP readings and central corneal thickness(CCT)measurements were monitored.Cases with induced ocular hypertension(OHT,defined as post-operative IOP higher than 21 mmHg),were identified and correlated to refractive procedure,gender,and corneal thickness.Results:At 4 weeks postoperatively,OHT was noted on 27.4%(20/73 eyes)in Group A,and 43.7%(121/277 eyes)in KCN Group B,(p<0.01).Six months post-operatively(following 5-months of discontinuing topical dexamethasone treatment and commencing treatment of IOP-lowering medications),OHT rate was 1.8%in Group A and 3.9%in the KCN Group B.Conclusion:This study demonstrates a potentially significant pre-disposition of keratoconic eyes to the development of steroid-induced OHT.