Title: Two Year Outcomes After Corneal Collagen Crosslinking For Keratoconus and Ectasia
Session Title: Corneal Biomechanics, Keratoconus and Collagen Cross Linking
Paper:
Purpose: To investigate clinical outcomes two years after corneal collagen crosslinking (CXL) for keratoconus (KC) and ectasia.
Methods: 50 eyes (38 patients) underwent CXL for keratoconus (n=34) or ectasia (n= 16) in a prospective, randomized controlled trial. CXL was performed with a UVX system (Peschke Meditrade GmbH) using standard technique. Clinical outcomes including uncorrected visual acuity (UCVA), best corrected visual acuity (BCVA), maximum keratometry (Kmax), CXL associated corneal haze, and corneal thickness were assessed and analyzed at baseline, 1 month, 3 month, 6 month, 1 year, and 2 year follow up visits. Corneal haze was measured by Scheimpflug densitometry.
Results: In the entire cohort, mean UCVA preoperatively was 20/151 (logMAR 0.88±0.35) and improved at 2 years to 20/136 (logMAR 0.83±0.38, p=0.2). BCVA was significantly improved from 20/46 (logMAR 0.36±0.24) to 20/35 (logMAR 0.24±0.19) (p<0.001). On topography, Kmax flattened significantly by 2.0±4.7D (p=0.004). Pachymetry values at 2 years were not significantly different from baseline (p=0.3). Corneal haze remained slightly increased at 2 years compared to baseline (+1.33±3.8, p=0.02). Between 1 and 2 years, the change in UCVA (change=-0.02±0.30, p=0.7), BCVA (change=-0.04±0.16, p=0.08), and Kmax (change=-0.05±2.9D, p=0.9) were not statistically significant. Mean corneal haze (change=-1.17±4.7), and pachymetry (change=+3.4±21.8μm), both continued to return toward baseline measurements, but these changes failed to reach statistical significance as well (phaze=0.09, ppachymetry=0.3). A similar clinical course was found in the analysis of stratified KC and ectasia subgroups.
Conclusions: At 2 years, CXL was effective at improving visual acuity and topographic outcomes. Clinical outcomes remained stable between 1 and 2 years after CXL.
Title: Corneal Thickness Effects using Riboflavin/Dextran versus Hypotonic Riboflavin during Corneal Collagen Crosslinking
Session Title: Corneal Biomechanics Keratoconus and UV Crosslinking
Paper:
Purpose: To investigate the use of Riboflavin 0.1% in 20% dextran solution versus its hypotonic formulation during ultraviolet light exposure in corneal collagen crosslinking (CXL) for keratoconus (KC) and ectasia.
Methods: In a prospective, controlled clinical trial, 21 eyes underwent CXL for KC or ectasia (14 and 7 eyes respectively). CXL was performed using the UVX system (Peschke Meditrade GmbH). All eyes underwent pre-treatment with Riboflavin 0.1% in 20% dextran solution every 2 minutes for 30 minutes. If the cornea was <400 microns thick, then hypotonic riboflavin was administered until the cornea swelled beyond 400 microns. Eyes were then randomized to receive either Riboflavin 0.1%/dextran (RIBO) or hypotonic (HYPO) riboflavin every 2 minutes for the 30 minute duration of UV exposure (UVA 365nm light for 30 minutes at an irradiance of 3mW/cm2). Corneal thickness was measured using ultrasound pachymetry (Sonogage).
Results: Mean initial corneal thickness was 435.7μm (ranging 318 to 526) and 445.4μm (ranging 327 to 532) for RIBO and HYPO eyes respectively. Following debridement, mean thickness was 392.1μm (ranging 304 to 463) for RIBO eyes and was 402.9μm (ranging 330 to 454) for HYPO eyes. After pre-treatment with riboflavin 0.1%/dextran, mean thickness was 417.2μm (ranging 323 to 535) for RIBO eyes and 417.0μm (ranging 317 to 468) for HYPO eyes. Three eyes (2 RIBO; 1 HYPO) required the use of hypotonic riboflavin to achieve the minimum corneal thickness of 400μm prior to UV irradiance. Mean corneal thinning during UV exposure was 133.8μm (SD 33.2)(p<0.0001) and 94.6μm (SD 48.0)(p=0.002) for RIBO and HYPO eyes respectively. Mean corneal thinning with UV exposure was significantly greater for RIBO eyes compared to HYPO eyes (p=0.04) At the conclusion of CXL treatment, mean thickness was 294.4μm (ranging 238 to 345) and 335.3μm (ranging 271 to 398) in RIBO and HYPO eyes respectively.
Conclusions: The use of hypotonic riboflavin appears to better maintain consistent corneal thickness during UV administration. Whether better maintenance of corneal thickness potentially may result in improved consistency, reproducibility and/or safety of the CXL procedure requires further follow-up.
Title:Corneal Collagen Crosslinking Outcomes With and Without Stromal Swelling with Hypotonic Riboflavin
Session Title: Corneal Biomechanics Keratoconus and UV Crosslinking
Paper:
Purpose: It has been suggested that hypotonic riboflavin can be used to swell the corneal stroma to a safe level in order to perform corneal collagen crosslinking (CXL). In this investigation, we compare 1 year CXL clinical outcomes, using hypotonic riboflavin for corneal swelling vs. standard riboflavin dextran solution only.
Methods: 103 eyes underwent CXL for keratoconus (n=68) or ectasia (n= 35) in a prospective, randomized controlled trial. Riboflavin (0.1% in 20% dextran T500 solution) was administered topically for 30 minutes. If the cornea was <400µm after this dosing, hypotonic riboflavin (0.1% in sterile water) was given, 1 drop every 10 seconds for 2 minute rounds, and ultrasonic pachymetry (U/S) was performed until the stroma had swollen to >400µm. Uncorrected visual acuity (UCVA), best corrected visual acuity (BCVA), maximum keratometry (Kmax), corneal haze, and thinnest pachymetry (Pthin) were compared between riboflavin groups.
Results: In the riboflavin dextran only group (n=42), UCVA (logMAR change=-.07±0.19,p=.04), BCVA (logMAR change=-.09±0.17,p<.01), and Kmax (change=-1.2±1.9D,p<.01) significantly improved, and corneal haze returned to baseline at 1 year (p=.1). Preoperative Pthin was 468.2±48.2µm, and at 1 year was slightly thinner (458.2±47.5µm,p<.01). In the hypotonic group (n=61), preoperative U/S, U/S after 30 minutes of riboflavin dextran administration, and U/S after hypotonic riboflavin administration, was 423.9±53.7µm, 340.9±45.1µm, and 413.6±11.1µm, respectively. On average, 3.1±2.2 rounds of hypotonic drops were required to swell the cornea ≥400µm. In this group, UCVA (logMAR change=-.09±0.28,p=.01), BCVA (logMAR change=-.1±0.18,p<.01), and Kmax (change=-1.9±4.0D,p<.01) significantly improved, and corneal haze remained slightly above baseline at 1 year (p<.01). Preoperative Pthin was 423.1±51.1µm, and at 1 year returned to preoperative measurement (420.9±51.7µm,p=.4). There was no significant difference between the two riboflavin groups, when comparing the changes in any of these clinical outcomes at 1 year (PUCVA =.5, PBCVA =.6, PKmax = .2, PHaze =.1, PPthin = .1).
Conclusions: Administration of hypotonic riboflavin to swell the corneal stroma does not appear to affect 1 year clinical outcomes compared to standard riboflavin/dextran alone.
Title: Simultaneous versus Sequential Intacs and Cornea Collagen Crosslinking for Keratoconus and Ectasia
Session Title: Corneal Biomechanics, Keratoconus and Collagen Cross Linking
Paper:
Purpose: To investigate the optimum timing of Intacs combined with corneal collagen crosslinking (CXL) (simultaneous vs. sequential) for keratoconus and ectasia.
Methods: In a prospective, controlled clinical trial, 31 eyes were randomized to receive Intacs followed by CXL on the same day (Sim group) (15 eyes) or Intacs followed by CXL at 3 months postoperatively (Seq group) (16 eyes). All eyes received symmetric 350 micron Intacs segments (Addition Technology Inc.) and CXL was performed using the UVX system (Peschke Meditrade GmbH). Clinical outcomes including UCVA, BCVA, MRSE, manifest cylinder, and topographic changes (Kmax) using the Pentacam were assessed pre- and postoperatively.
Results: Thirteen eyes in the Sim group and 7 eyes in the Seq group have data collected to 3 months postoperatively. For Sim eyes, mean UCVA preoperatively was 20/171 and was 20/162 three months postoperatively. Mean BCVA changed from 20/44 preoperatively to 20/47 at 3 months postoperatively. MRSE improved by 0.94D and manifest cylinder remained the unchanged. Topographically, Kmax flattened by 0.91D. All outcomes failed to reach statistical significance. Similarly, Seq eyes, showed no significant changes in UCVA and BCVA which improved from 20/175 to 20/153 and 20/36 to 20/28 at 3 months postoperatively respectively. MRSE improved by 0.68D, but failed to reach statistical significance. Manifest cylinder remained unchanged as well as topographically measured mean Kmax. No significant differences between Sim and Seq cohorts were observed.
Conclusions: Early results show no differences in Sim compared to Seq Intacs and CXL. Studies suggest that the beneficial effects of CXL are not achieved until 6 months postoperatively which indicate early healing may be confounding results. The optimal method timing of Intacs combined with CXL remains to be elucidated with further follow-up.
Title: Patient Satisfaction and Subjective Visual Function after Corneal Collagen Crosslinking
Session Title: Corneal Biomechanics Keratoconus and UV Crosslinking
Paper:
Purpose: To assess patient satisfaction and subjective visual function, using a patient questionnaire, one year after corneal collagen crosslinking (CXL) for keratoconus and corneal ectasia.
Methods: 107 eyes of 76 patients underwent CXL for keratoconus (n=71) or ectasia (n= 36) in a prospective, randomized controlled trial. Patients completed a subjective questionnaire concerning their visual symptoms, administered preoperatively and at 1 year. Patients ranked symptoms on a scale from 1 to 5 (1= none, 2= mild, 3=moderate, 4=marked, 5= severe). Reported symptoms of photophobia, difficulty night driving, difficulty reading, diplopia, fluctuations in vision, glare, halo, starburst, dryness, pain, and foreign body sensation were analyzed using a student’s t-test. Additionally, improvements in maximum keratometry (Kmax) and best corrected visual acuity (BCVA) were correlated with each of the subjective visual symptoms using Pearson’s correlation.
Results: Preoperative to 1 year changes in symptoms were: photophobia 2.7±1.3 to 2.5±1.1; night driving 3.2±1.5 to 2.8±1.5; reading 3.1±1.5 to 2.9±1.3; diplopia 2.5±1.3 to 2.1±1.2; fluctuations in vision 2.6±1.2 to 2.4±1.1; glare 3.1±1.4 to 2.7±1.2; halo 2.9±1.4 to 2.5±1.3; starburst 2.6±1.5 to 2.4±1.4; dryness 2.1±1.2 to 2.0±.1.1; pain 1.6±0.9 to 1.6±0.9; and foreign body sensation 1.8±1.1 to 1.6±0.9. The improvements in night driving (p<.01), difficulty reading (p=.01), diplopia (p<.01), glare (P<.01), halo (P<.01), starbursts (p=.02), and foreign body sensation (p=.01) were statistically significant. All other changes, at 1 year failed to reach statistical significance pphotophobia=.2, pfluctuation=.1, pdryness=.4, ppain=.9). There was no significant difference between the keratoconus and ectasia subgroups. There was a weak, but significant, association between the change in Kmax, and the change in night driving (r=.3, p<.01), pain (r=.2, p=.04), and foreign body sensation (r=.3, p<.01) ratings. There was no association between the change in BCVA and the change in any of the questionnaire ratings at 1 year.
Conclusions: One year after CXL, patients note subjective improvement in a number of visual symptoms; specifically, night driving, difficulty reading, diplopia, glare, halo, starbursts, and foreign body sensation
