Long-Term Comparison of Simultaneous Topography-Guided Photorefractive Keratectomy Followed by Corneal Cross-linking versus Corneal Cross-linking Alone.

PURPOSE: To compare the results of corneal collagen cross-linking (CXL) alone with combined simultaneous topography-guided photorefractive keratectomy plus CXL (tPRK-CXL) for progressive keratoconus for a 3-year interval. DESIGN: Prospective, comparative interventional case series. PARTICIPANTS: Forty-eight patients (60 eyes) with progressive keratoconus. METHODS: Thirty eyes underwent combined tPRK with a solid-state laser (maximum ablation depth, 50 µm) followed by CXL, and 30 eyes underwent CXL alone. Groups were matched in terms of age and keratoconus stage. MAIN OUTCOME MEASURES: Corrected distance visual acuity (CDVA), uncorrected distance visual acuity (UDVA), keratometry, and corneal confocal microscopy. RESULTS: Mean follow up was 39±11 months. Mean age at operation was 28±5.82 years. Before surgery, average CDVA in the tPRK-CXL group was 0.26±0.17 logarithm of the minimum angle of resolution (logMAR), and in the CXL group was 0.24±0.18 logMAR (P = 0.58). At last follow-up, CDVA was 0.09±0.10 logMAR in the tPRK-CXL group and 0.15±0.12 logMAR in the CXL group (P < 0.05). In both groups, no patient lost more than 2 lines of Snellen visual acuity, whereas 19 eyes and 8 eyes in the tPRK-CXL group and in the CXL group, respectively, gained 2 or more lines of CDVA. Before surgery, average UDVA was 0.83±0.54 logMAR in the tPRK-CXL group and 0.86±0.62 logMAR in the CXL group (P = 0.79). At last follow-up, UDVA was 0.27±0.25 logMAR in the tPRK-CXL group and 0.69±0.58 logMAR in the CXL group (P < 0.001). Before surgery, steep and flat keratometry had no significant differences between groups, and at last follow-up, both steep and flat keratometry readings were significantly flatter in the tPRK-CXL group compared with the CXL group. Depth of CXL treatment, as evaluated by confocal microscopy, was 269.8±31.8 µm in the CXL group and 299.7±29.8 µm in the tPRK-CXL group (P < 0.001). No differences were found in endothelial cell density. CONCLUSIONS: Simultaneous tPRK followed by CXL in this series of keratoconus patients offered significantly improved vision to treated patients in comparison with CXL alone, and similar results regarding postoperative stability. Safety concerns regarding corneal thickness were taken into account in treatment planning.

Corneal collagen cross-linking (CXL) combined with refractive procedures for the treatment of corneal ectatic disorders: CXL plus.

PURPOSE: To discuss current combined corneal collagen cross-linking (CXL) and refractive surgical techniques (herein termed "CXL plus") for the treatment of corneal ectatic disorders to improve functional visual acuity in addition to corneal stability from CXL alone. METHODS: Literature review. RESULTS: Efficacious combined treatments with CXL include: photorefractive keratectomy, transepithelial phototherapeutic keratectomy, intrastromal corneal ring segments implantation, phakic intraocular lens implantation, and multiple combined procedures. Some uncertainty remains as to the optimal strategies for each patient. A decision tree is proposed to facilitate optimal patient management. CONCLUSIONS: With multiple adjuvant techniques, CXL plus is likely to benefit many patients with corneal ectatic disorders. The appropriate combined procedure will depend on multiple factors, such as refraction, corneal thickness, and degree of irregular astigmatism.

Femtosecond laser-assisted astigmatic keratotomy for postoperative trabeculectomy-induced corneal astigmatism.

PURPOSE: To describe a case of postoperative trabeculectomy-induced corneal astigmatism treated with femtosecond laser-assisted astigmatic keratotomy. METHODS: After trabeculectomy, the patient demonstrated change in manifest refraction from -0.5 diopters preoperatively to mixed astigmatism of -3.5 + 5.25@100 postoperatively and a decrease in uncorrected distance visual acuity from 20/60 preoperatively to 20/200 at 1 month postoperatively. Because the patient was intolerant to spectacle use, she underwent femtosecond laser-assisted astigmatic keratotomy. RESULTS: After astigmatic keratotomy there was improvement in corneal topographic astigmatism from 4.15 to 0.81 diopters with uncorrected distance visual acuity of 20/60(-2) and manifest refraction of -0.75 + 1.0@90 at 3 months postoperatively. There were no intraoperative or postoperative complications. CONCLUSIONS: Femtosecond laser-assisted astigmatic keratotomy may be considered in eyes with postoperative trabeculectomy-induced mixed astigmatism.

Refractive and topographic fluctuations due to intracorneal ring segments motility.

PURPOSE: To describe a patient with refractive and topographic fluctuations 5 years after intracorneal ring segments (ICRS) implantation for the management of corneal ectasia after LASIK. METHODS: Case report. RESULTS: A 48-year-old woman presented complaining of intermittent decreased vision over 1 year that improved with eye rubbing. Slit-lamp and optical coherence tomography (OCT) examinations revealed overriding ring segments that could be restored to normal position after minor corneal massage. Topographic and refractive findings were significantly influenced by the ICRS positioning and caused decreased visual function when overriding. To avoid ICRS override, surgical dissection of the corneal tunnel along with ring segment repositioning was performed. A suture was placed through the ring's positioning hole to stabilize the ICRS at its optimal position and to avoid recurrence of this phenomenon. CONCLUSIONS: Patients undergoing femtosecond laser-assisted ICRS implantation may experience ring segment migration and override of the segments that could lead to decreased visual function. Proper surgical repositioning and ring segment fixation may address this complication and offer satisfactory visual and refractive outcomes along with avoidance of ICRS migration and override.

Simultaneous conventional photorefractive keratectomy and corneal collagen cross-linking for pellucid marginal corneal degeneration.

PURPOSE: To present the results after simultaneous conventional photorefractive keratectomy combined with corneal collagen cross-linking for pellucid marginal corneal degeneration. METHODS: In this prospective, interventional case series, 6 patients (8 eyes) with pellucid marginal corneal degeneration were enrolled. All patients underwent simultaneous conventional photorefractive keratectomy combined with corneal collagen cross-linking; corneal epithelium was removed by transepithelial phototherapeutic keratectomy during treatment (Cretan protocol plus conventional photorefractive keratectomy). Visual and refractive outcomes were evaluated along with endothelial cell density preoperatively and at 1, 3, 6, and 12 months postoperatively. RESULTS: No intraoperative or postoperative complications were observed in any of the patients. LogMAR mean uncorrected distance visual acuity improved significantly from 1.05 ± 0.33 preoperatively to 0.41 ± 0.27 (P = .018) at 12 months postoperatively. Mean corrected distance visual acuity did not change significantly (P > .05) postoperatively. Mean spherical equivalent improved significantly from -3.52 ± 2.29 diopters preoperatively to -1.57 ± 1.76 diopters (P = .028) at last follow-up. Mean corneal astigmatism was significantly reduced from -6.83 ± 2.33 diopters preoperatively to -4.71 ± 1.89 diopters (P = .018) at the last follow-up. No endothelial cell density alterations were observed throughout the follow-up period (P > .05). CONCLUSIONS: Simultaneous conventional photorefractive keratectomy combined with corneal collagen cross-linking seems to be an effective, safe, and promising treatment for the management of pellucid marginal corneal degeneration.

Corneal confocal microscopy findings in sporadic cases of pre-descemet corneal dystrophy.

PURPOSE: To present corneal confocal microscopy (CCM) findings in a series of patients with pre-Descemet corneal dystrophy (PDCD). METHODS: A 28-year-old man, a 50-year-old man, a 30-year-old woman, and a 31-year-old man were clinically diagnosed with PDCD on slit lamp microscopic evaluation. All patients were evaluated by means of CCM. The parents of the patients were clinically evaluated. Two of the patients underwent photorefractive keratectomy. RESULTS: In all the patients, CCM revealed highly reflective stromal particles and pleomorphic structures that included particles in the deep stroma, immediately anterior to the Descemet membrane extending up to 60 µm from endothelium. No evidence of PDCD was observed clinically in the parents of the patients. Postoperative course of photorefractive keratectomy was uneventful for both of the patients. CONCLUSIONS: With the use of CCM, a specific pattern of findings seemed to be related with PDCD in this series of sporadic cases.

Effect of corneal collagen cross-linking on corneal innervation, corneal sensitivity, and tear function of patients with keratoconus.

PURPOSE: To evaluate the effect of corneal collagen cross-linking (CXL) on corneal innervation, corneal sensitivity, and tear function in patients with keratoconus. DESIGN: Prospective, interventional case series. PARTICIPANTS: Twenty-four patients with bilateral keratoconus (30 eyes) who presented to the Institute of Vision and Optics, University of Crete, from May 2008 to October 2008. METHODS: Patients underwent CXL. Confocal microscopic analysis of corneal sub-basal nerve plexus (total nerve length per image), corneal sensitivity (assessed with the Cochet-Bonnet esthesiometer), basic tear secretion (assessed with Schirmer's I test with anesthesia), and tear film stability (evaluated by means of tear film break-up time [TFBUT]) were assessed preoperatively and at 1, 3, 6, 9, 12, 18, and 24 months postoperatively. MAIN OUTCOME MEASURES: Comparisons between preoperative and each postoperative value of total nerve length per image, corneal sensitivity, Schirmer's I test results, and TFBUT. RESULTS: Total nerve length per image and corneal sensitivity were significantly decreased until postoperative month 6 (for both parameters: P<0.05 paired-samples t test at 1, 3, and 6 months postoperatively). Total nerve length per image tended to increase up to 2 years postoperatively, when it reached the preoperative level, but differences with the preoperative values after the sixth post-CXL month were insignificant. The results of Schirmer's I test and TFBUT had no statistically significant difference at any time point. CONCLUSIONS: A transient decrease in corneal innervation and corneal sensitivity can be observed up to 6 months after CXL. No significant effect of CXL could be detected on basic tear secretion and tear film stability in our group of patients. FINANCIAL DISCLOSURE(S): The author(s) have no proprietary or commercial interest in any materials discussed in this article.

Anterior and posterior corneal stroma elasticity after corneal collagen crosslinking treatment.

The purpose of this project was to assess anterior and posterior corneal stromal elasticity after corneal collagen cross linking (CXL) treatment in human cadaver eyes using Atomic Force Microscopy (AFM) through indentation. Twenty four human cadaver eyes (12 pairs) were included in this study and divided into 2 groups (6 pairs per group). In both groups, the left eye (OS) served as a control (no riboflavin or CXL treatment was performed) and the right eye (OD) underwent CXL treatment (30 min of riboflavin pretreatment followed by 30 min of exposure to 3 mW/cm(2) of ultraviolet light). In group 1, the anterior stroma was exposed by manual delamination of approximately 50 µm of the corneal stroma including Bowman's membrane. In group 2, the posterior stroma was exposed by delamination of the anterior 50% of the corneal stroma including Bowman's membrane. Delamination was performed after crosslinking treatment in the case of the treated eyes. In all eyes, the stromal elasticity was quantified using AFM through indentation. Young's modulus of elasticity for the anterior cornea (group 1) was 245.9 ± 209.1 kPa (range: 82.3-530.8 kPa) for the untreated control eyes, and 467.8 ± 373.2 kPa (range: 157.4-1126 kPa) for the CXL treated eyes. Young's modulus for the posterior cornea (group 2) was 100.2 ± 61.9 kPa (range: 28.1-162.6 kPa) for the untreated control eyes and 66.0 ± 31.8 kPa (range: 31.3-101.7 kPa) for the CXL treated eyes. Young's modulus of the anterior stroma significantly increased after CXL treatment (p = 0.024), whereas the posterior stroma did not demonstrate a significant difference in Young's modulus after CXL treatment (p = 0.170). The anterior stroma was stiffer than the posterior stroma for both the control and CXL treatment groups (p = 0.077 and p = 0.023, respectively). Our findings demonstrate that stiffness of the anterior corneal stroma after CXL treatment seems to increase significantly, while the posterior stroma does not seem to be affected by CXL.

Complications of femtosecond laser-assisted re-treatment for residual refractive errors after LASIK.

PURPOSE: To report complications of femtosecond laser-assisted re-treatment by the creation of side cuts within the old flaps for residual refractive error after primary LASIK in two patients. METHODS: Case report. RESULTS: Three eyes of two patients had complications with a circumferential sliver of stromal tissue displaced during surgery due to overlap of old and new side cuts. The displaced tissue was repositioned and corneal anatomy was restored. Two of three eyes demonstrated improvement in the uncorrected visual acuity, whereas one eye lost two lines of corrected visual acuity due to loss of tissue at side cut resulting from flap manipulation, which was done at 1 week. CONCLUSIONS: These cases demonstrate a complication of femtosecond laser-enabled side-cut for LASIK enhancement and factors that may lead to this complication and precautions to avoid it.

Three-Year Results of Simultaneous Transepithelial Phototherapeutic Keratectomy and Conventional Photorefractive Keratectomy (Cretan Protocol Plus) Followed by Corneal Crosslinking for Keratoconus.

PURPOSE: The aim of this study was to present the 3-year outcomes after simultaneous transepithelial phototherapeutic keratectomy (t-PTK) and conventional photorefractive keratectomy (PRK) followed by corneal crosslinking (CXL) for keratoconus. METHODS: In this prospective, interventional case series, patients with progressive keratoconus underwent simultaneous t-PTK and conventional PRK followed by CXL (Cretan protocol plus). Visual, refractive, and topographic outcomes were evaluated along with endothelial cell density (ECD) preoperatively and at 1, 2, and 3 years postoperatively. RESULTS: Twenty-two patients (31 eyes) were enrolled. No intraoperative or postoperative complications were observed in any of the patients. Logarithm of the minimum angle of resolution (logMAR) mean uncorrected and mean corrected distance visual acuity improved from 0.81 ± 0.40 and 0.18 ± 0.21 preoperatively to 0.38 ± 0.33 ( P < 0.001) and 0.06 ± 0.12 ( P < 0.001) at 3-year follow-up. Mean spherical equivalent improved from -5.39 ± 3.89 diopters (D) preoperatively to -2.29 ± 2.65 D ( P < 0.001) at 3 years postoperatively. Mean corneal astigmatism reduced from -4.70 ± 2.86 D preoperatively to -3.55 ± 2.45 D ( P = 0.001) at 3 years postoperatively. No ECD alterations were observed throughout the 3-year follow-up ( P > 0.05). CONCLUSIONS: Simultaneous t-PTK and conventional PRK followed by CXL seems to be an effective and safe treatment for progressive keratoconus over 3-year follow-up.

Femtosecond laser technology in corneal refractive surgery: a review.

PURPOSE: To discuss current applications and advantages of femtosecond laser technology over traditional manual techniques and related unique complications in corneal refractive surgical procedures, including LASIK flap creation, intracorneal ring segment implantation, astigmatic keratotomy, presbyopic treatments, and intrastromal lenticule procedures. METHODS: Literature review. RESULTS: From its first clinical use in 2001 for LASIK flap creation, femtosecond lasers have steadily made a place as the dominant flap-making technology worldwide. Newer applications are being evaluated and are increasing in their frequency of use. CONCLUSIONS: Femtosecond laser technology is rapidly becoming a heavily utilized tool in corneal refractive surgical procedures due to its reproducibility, safety, precision, and versatility.

Outcomes of refractive surgery in patients with topographic superior corneal steepening.

PURPOSE: To evaluate the outcomes of refractive surgery in patients with topographic superior corneal steepening. METHODS: This retrospective, noncomparative, interventional, clinical study included 16 patients (29 eyes) with persistent superior corneal steepening as a variation of corneal curvature (inferior to superior topographic corneal difference of at least 1.00 diopter [D] at a 3-mm zone) not related to any underlying disease or condition who underwent corneal refractive surgery. Refractive, keratometric, and visual outcomes were evaluated preoperatively and at 1, 3, 6, 12, and 24 months postoperatively. RESULTS: Twenty-two eyes underwent photorefractive keratectomy and 7 eyes underwent LASIK. Mean follow-up was 27.38±2.37 months (range: 25 to 32 months). Mean preoperative inferior to superior keratometric difference was 1.61±0.36 D (range: 1.20 to 2.63 D). Mean preoperative spherical equivalent refraction was -4.45±1.66 D (range: -2.25 to -8.00 D), which decreased to -0.09±0.61 D (range: +0.75 to -1.38 D) (P<.05) at last follow-up. Mean preoperative topographic corneal astigmatism was 1.44±0.79 D (range: 0.52 to 3.83 D), which decreased to 0.66±0.39 D (P<.05) 3 months postoperatively and remained stable during follow-up (P<.54). Mean preoperative uncorrected distance visual acuity and corrected distance visual acuity in logMAR units were 1.57±0.62 and 0.02±0.06, respectively, which improved at last follow-up to 0.00±0.05 and -0.02±0.04, respectively. No intra- or postoperative complications were noted; specifically, no patients developed postoperative ectasia. CONCLUSIONS: Corneal refractive surgery in patients with isolated topographic superior corneal steepening provided acceptable refractive and visual outcomes without any intra- or postoperative complications. Diligence is required to screen for the potential of ectatic corneal disorders in this population. Photorefractive keratectomy may be a safer option for these patients than LASIK.

Small incision lenticule extraction retreatment in a patient with high residual refractive error after photorefractive keratectomy: A case report.

A 36-year-old male underwent uneventful small incision lenticule extraction (SMILE) for the correction of his high residual refractive error 12 years after photorefractive keratectomy (PRK). Preoperatively, uncorrected distance visual acuity (UDVA) was counting fingers in both eyes. Corrected distance visual acuity was 20/20 in the right and 20/30 in the left eye due to amblyopia. One month after SMILE, UDVA was 20/20 and 20/30 in the right and left eye, respectively; post-PRK corneal haze had reduced. During the 4-year follow-up, UDVA remained stable and there were no complications. SMILE could be a good alternative approach for retreatment in post-PRK patient.

CIRCLE Software for Management of Epithelial Ingrowth After SMILE.

PURPOSE: To report a novel therapeutic use of CIRCLE software (Carl Zeiss Meditec) to manage visually significant epithelial ingrowth following small incision lenticule extraction surgery (SMILE). METHODS: Case series. RESULTS: In this case series, the authors describe three eyes with progressive and visually significant epithelial ingrowth following an uneventful SMILE procedure. The management of epithelial ingrowth following SMILE is challenging, given the small access incision to the interface and the risk of incomplete removal. All cases were successfully managed by converting the SMILE cap into a flap using the CIRCLE software, which provided the necessary access to the original SMILE interface. Once the flap was lifted, the epithelial in-growth was completely debrided from the underlying stroma and undersurface of the flap, followed by a thorough interface wash. Postoperative recovery was uneventful, with no recurrence noted in any of the eyes. CONCLUSIONS: Use of CIRCLE software provides a novel and unique approach to successfully treating vision-threatening epithelial ingrowth after SMILE. [J Refract Surg. 2021;37(11):776-780.].

Corneal cross-linking (CXL) combined with refractive surgery for the comprehensive management of keratoconus: CXL plus.

The past two decades have witnessed an unprecedented evolution in the management of keratoconus that demands a holistic approach comprising of inhibiting the ectatic progression as well as visual rehabilitation. The advent of corneal cross-linking (CXL) in the late 1990s resulted in long-term stabilization of the ectatic cornea along with limited reduction in corneal steepening and regularization of corneal curvature. However, CXL as a standalone procedure does not suffice in rehabilitating the functional vision especially in patients who are unwilling or intolerant towards contact lenses. The concept of "CXL plus" was proposed which incorporates adjunctive use of refractive procedures with CXL in order to overcome the optical inefficiency due to corneal irregularity, decrease the irregular astigmatism, correct the residual refractive error and improve functional visual outcome in keratoconus. Several refractive procedures such as conductive keratoplasty (CK), photorefractive keratectomy (PRK), transepithelial phototherapeutic keratectomy (t-PTK), intrastromal corneal ring segments (ICRS) implantation, phakic intraocular lens (PIOL) implantation and multiple other techniques have been combined with CXL to optimize and enhance the CXL outcome. This review aimed to summarize the different protocols of CXL plus, provide guidelines for selection of the optimum CXL plus technique and aid in decision-making for the comprehensive management of cases with primary keratoconus in addition to discussing the future and scope for innovations in the existing treatment protocols.

Femtosecond-Assisted Big Bubble: A Feasibility Study.

PURPOSE: To evaluate the feasibility of femtosecond laser-assisted (FA) tunnel creation as a pretreatment for creating a big bubble (BB) to pneumo-dissect the corneal stroma from Descemet membrane. METHODS: Five human cadaver eyes received pretreatment using a femtosecond laser. An intrastromal tunnel, along with a side cut, was achieved using customized femtosecond corneal disruption (custom mask). Before treatment, optical coherence tomography was performed and the intrastromal tunnel was intended to achieve a parallel orientation with respect to the corneal endothelial cell layer (50 µm above the endothelium). Surgical dissection of the side cut using a Sinskey hook was performed, followed by insertion of a deep anterior lamellar keratoplasty cannula into the tunnel and pneumo-dissection (BB). All corneas after treatment were prepared for histologic evaluation (light microscopy). RESULTS: FA pretreatment was successful in all 5 cadaveric corneas, and the BB was achieved in all eyes as well. Histologic evaluation of the corneas revealed complete separation of Descemet membrane and stroma in all eyes, with no remaining stroma attached to Descemet membrane and no signs of perforation. CONCLUSIONS: FABB seems feasible because pneumo-dissection of the corneal stroma from Descemet membrane was achieved in all human cadaver corneas of this experimental study. Optical coherence tomography, corneal histology, and macroscopic evaluation revealed complete Descemet-stromal separation.