Prevalence of bacillary layer detachment in diabetic macular edema and response to 3 anti-vascular endothelial growth factor treatment.

Spectral-domain optical coherence tomography is widely used in maculopathy, including diabetic macular edema (DME). Bacillary layer detachment (BALAD) is a novel optical coherence tomography finding, defined as the separation of the intraretinal layer between the inner segment myoids and ellipsoids. A total of 161 treatment-naïve eyes with centrally involved DME that underwent 3 monthly loading doses of anti-vascular endothelial growth factor (anti-VEGF) intravitreal injections were enrolled and analyzed retrospectively. BALAD was found in 6.2% of eyes with concurrent subretinal fluid (SRF). All eyes were divided into 3 groups: no either group had neither SRF or BALAD; the SRF only group had SRF but no BALAD; and the BALAD group had both SRF and BALAD. A significant increase in baseline central foveal thickness (CFT) in the BALAD group was observed (no either vs SRF only vs BALAD, baseline CFT: 387.6 ±â€…74.29 vs 440.6 ±â€…106.79 vs 642.0 ±â€…188.86; P < .01). Total resolution of BALAD was noted after anti-VEGF therapy, along with a significant decrease in CFT in all groups (CFT decrease: 82.4 ±â€…87.07 vs 187.6 ±â€…138.88 vs 252.1 ±â€…127.63; P < .01). Eyes with BALAD tended to have the worst baseline visual acuity (baseline logarithm of the minimum angle of resolution VA: 0.76 ±â€…0.353 vs 0.63 ±â€…0.303 vs 1.15 ±â€…0.300; P = .046) but showed the most improvement after treatment (logarithm of the minimum angle of resolution VA change: -0.14 ±â€…0.235 vs -0.22 ±â€…0.275 vs -0.27 ±â€…0.250; P = .079). After resolution of BALAD, all eyes in the BALAD group exhibited ellipsoid zone and/or interdigitation zone disruption corresponding to the BALAD area. BALAD is a novel optical coherence tomography finding associated with a spectrum of diseases including DME. With anti-VEGF therapy, total resolution of BALAD and a significant decrease in CFT can be obtained. However, ellipsoid zone/interdigitation zone disruption tended to develop.

Effectiveness of Topical Ganciclovir 2% Monotherapy Versus Combined Steroid Therapy in Cytomegalovirus Endotheliitis.

We aimed to report the clinical manifestations of cytomegalovirus (CMV) corneal endotheliitis and the results of long-term treatment with topical ganciclovir 2% with and without steroids. This retrospective, interventional study included 15 eyes of 13 patients diagnosed with CMV corneal endotheliitis by positive CMV DNA and treated with long-term topical ganciclovir 2% eye drops at a tertiary referral center and the median follow-up period was 17 months. Ocular manifestations included keratic precipitates (KPs) (100%), elevated IOP (93.3%), iritis (60%), corneal edema (60%), and moth-eaten iris atrophy (60%). After long-term treatment, corneal edema, iritis, and KPs significantly decreased (effect size: 72%, 76% and 70%, respectively; p = 0.024, p = 0.006 and p < 0.001, respectively). Both the logMAR acuity and IOP significantly improved (median logMAR was 0.52 before treatment and 0.22 after treatment; median IOP was 42 mmHg before treatment and 12 mmHg after treatment; p = 0.001 and p < 0.001, respectively). The ECD was maintained (effect size: 80%), and the percentage of hexagonal cell ratio of endothelial cells significantly improved after treatment (effect size: 82%; p = 0.035). Fewer anti-glaucoma medications were used in the non-steroid group (effect size: 79%; p = 0.034). Long-term maintenance treatment with topical ganciclovir 2% monotherapy not only provides effective therapy and reduces recurrence, but also decreases the high IOP related to the combination of steroids used.

Optical coherence tomography as a useful adjunct in the early detection of meningioma with optic nerve compression.

A 48-year-old woman presented with persistent clouding vision in her lower field in the right eye for 5 months. A small retinal hemorrhage was initially reported. Her visual acuity was 20/30 in the right eye and 20/20 in the left, with normal color vision and pupil response. Fundus examination did not reveal any retinal hemorrhage. Although optical coherence tomography (OCT) showed normal macula and retinal nerve fiber layers in both eyes, asymmetric thinning of the ganglion cell inner plexiform layer was found in the superior macula of the right eye in ganglion cell analysis (GCA). Visual field examination revealed a subtle inferonasal scotoma. Compressive optic neuropathy (CON) was suspected. The visual evoked potential test revealed delayed P100 latency. A tuberculum sellae meningioma was found with right medial optic canal extension. The visual acuity of the right eye returned to 20/25 after decompression surgery. OCT can be used to differentiate between retinopathy and optic neuropathy. GCA can help in the early detection of CON and achieve a good visual outcome after surgery.

Late intraocular lens exchange in dissatisfied patients with multifocal intraocular lens implantation.

Intraocular lens (IOL) exchange may be required after multifocal IOL implantation due to dissatisfaction. Late IOL exchange is more challenging when it is done with capsulotomy. We presented a retrospective case series study enrolling four consecutive eyes reviewing late IOL exchange due to decreased vision and dysphotopsia. High residual hyperopia, astigmatism, and IOL tilt occurred in 3 eyes, respectively. The mean time to the IOL exchange was 15.8 ± 10.63 months. After separation of the adhesions by visco-dissection assisted with a 27-gaze needle and sinskey hook, IOL was explanted. One-piece IOL was implanted in the bag in two eyes without posterior capsulotomy, whereas three-piece IOL was implanted in the sulcus after viscoelastic tamponade in the other 2 eyes with capsulotomy. No complication occurred and dysphotopsia disappeared. The mean logarithm of the minimum angle of resolution best-corrected visual acuity significantly improved from 0.33 ± 0.12 preoperatively to 0.11 ± 0.13 postoperatively. In conclusion, late IOL exchange could be safely performed with proper technique and achieve good results.

HYPERREFLECTIVE FOCI AS IMPORTANT PROGNOSTIC INDICATORS OF PROGRESSION OF RETINITIS PIGMENTOSA.

PURPOSE: To investigate the presence and clinical relevance of hyperreflective foci (HRFs) in retinitis pigmentosa. METHODS: Seventy seven retinitis pigmentosa cases were retrospectively reviewed. The 10-mm wide cross-line macular scans in optical coherence tomography were acquired. Hyperreflective foci were classified according to the location in optical coherence tomography: outer layers within the macula (HRF-outer-central), macular border beyond the central 3 mm (HRF-outer-perifoveal), and choroid (HRF-choroidal). The visual acuity at baseline, at 12 months, and other fundus characteristics were collected. RESULTS: The mean logMAR best-corrected visual acuity decreased from 0.59 ± 0.66 (20/78 in Snellen) to 0.74 ± 0.81 (20/106 in Snellen) in 1 year. Sixty-six (42.9%), 105 (68.2%), and 98 (63.6%) eyes were classified to HRF-outer-central, HRF-outer-perifoveal, and HRF-choroidal group, respectively. Hyperreflective foci were positively correlated with poorer vision, central macular thinning, and ellipsoid zone disruption (all P < 0.001). Worse vision was associated with older age, macular involvement, and the coexistence of two or three HRF groups (P = 0.014, 0.047, 0.019, <0.001, respectively). Hyperreflective foci developed more frequently in patients with thick choroid than in those with thin choroid. The coexistence of three HRF groups was correlated with quicker visual deterioration (P = 0.034). CONCLUSION: Hyperreflective foci are common in retinitis pigmentosa and can be a negative prognostic indicator of macular thickness and visual preservation. Thick choroid was associated with all groups of HRFs, especially HRF-choroidal.

Leber's Congenital Amaurosis: Current Concepts of Genotype-Phenotype Correlations.

Leber's congenital amaurosis (LCA), one of the most severe inherited retinal dystrophies, is typically associated with extremely early onset of visual loss, nystagmus, and amaurotic pupils, and is responsible for 20% of childhood blindness. With advances in molecular diagnostic technology, the knowledge about the genetic background of LCA has expanded widely, while disease-causing variants have been identified in 38 genes. Different pathogenetic mechanisms have been found among these varieties of genetic mutations, all of which result in the dysfunction or absence of their encoded proteins participating in the visual cycle. Hence, the clinical phenotypes also exhibit extensive heterogenicity, including the course of visual impairment, involvement of the macular area, alteration in retinal structure, and residual function of the diseased photoreceptor. By reviewing the clinical course, fundoscopic images, optical coherent tomography examination, and electroretinogram, genotype-phenotype correlations could be established for common genetic mutations in LCA, which would benefit the timing of the diagnosis and thus promote early intervention. Gene therapy is promising in the management of LCA, while several clinical trials are ongoing and preliminary success has been announced, focusing on RPE65 and other common disease-causing genes. This review provides an update on the genetics, clinical examination findings, and genotype-phenotype correlations in the most well-established causative genetic mutations of LCA.

Review, analysis, and education of antiseptic related ocular injury in the surgical settings.

Preoperative skin antiseptic preparation is the gold standard for prevention of surgical infection. However, improper use of antiseptics may lead to severe ocular damage. Currently, the most common surgical antiseptics can be divided into aqueous-based and alcohol-based disinfectants, with chlorhexidine and iodine/iodophors being the two major components. Chlorhexidine has a persistent antimicrobial effect and is resistant to neutralization by blood or organic products in surgical wounds. Nevertheless, due to its toxicity to the ears, meninges, and eyes, application of chlorhexidine should be prohibited in these surgical fields. Iodine/iodophor is better tolerated by the ocular surface and is the recommended antiseptic for ophthalmic or head and neck surgeries close to the periocular area. Alcohol is less pricey and has a rapid antiseptic effect, though its desiccating effect and flammability restrict the use in mucosal or laser surgeries. The single or combined use of these antiseptics may inadvertently induce severe ocular damage, especially during time-consuming head and neck surgeries with prone, hyperextension, or lateral tilt positions, or surgeries under general anesthesia. Apart from the choice of antiseptics, appropriate selection and attachment of bio-occlusive dressings are key to avoiding antiseptic-related ocular injuries. In this review, we provided a comprehensive summary of the characteristics of antiseptics used in surgical settings and the possible mechanisms and outcomes of antiseptic-related ocular injuries. The prevention, diagnosis, and acute management of these complications were also discussed.

Use of white light in vivo confocal microscopy for the detection of spatial changes in the corneal nerves in cases of early-stage Acanthamoeba keratitis with radial keratoneuritis.

Purpose: Radial keratoneuritis (RK) is a common feature of Acanthamoeba keratitis (AK). In vivo confocal microscopy (IVCM) is noninvasive and provides real-time images for the diagnosis of corneal diseases by allowing the visualization of corneal structures and morphologies of living organisms at the cellular level. Images of AK with RK obtained using commercial white light IVCM devices have not been frequently evaluated. In the present study, a white light IVCM device was used to evaluate the corneal findings and describe spatial changes in the corneal nerves at different depths in cases of early-stage AK with RK. Methods: In this retrospective, observational study, white light IVCM images focused on RK were evaluated for Acanthamoeba cysts/trophozoites, corneal deposits, and altered corneal nerves, with special emphasis on three-dimensional spatial changes in the corneal nerves at different depths. Results: Seventeen eyes of 17 patients exhibiting early-stage AK with RK were included in the study. Acanthamoeba cysts/trophozoites were observed in the corneal epithelium of 13 eyes and stroma of 7 eyes. Alterations in the corneal nerve morphology and density were observed from the basal epithelial layer to the stromal layer in 12 eyes. Acanthamoeba trophozoites were attached to the corneal stromal nerves in five eyes. Conclusion: These findings suggest that white light IVCM can identify consistent corneal findings, particularly spatial changes in the corneal nerves, in cases of early-stage AK with RK.

Clinical features and outcomes of Acanthamoeba keratitis in a tertiary hospital over 20- year period.

PURPOSE: To analyze the outcomes of Acanthamoeba keratitis (AK) in terms of different clinical presentations in a tertiary hospital in Taiwan over a 20- year period. METHODS: This is a retrospective case series. Patients with AK diagnosed at the National Taiwan University Hospital between January 1996 and December 2015 were identified. A diagnosis of AK was made on the basis of positive Acanthamoeba smear/cultures or pathological identification of Acanthamoeba cysts on keratoplasty specimens. Patient demographics, clinical presentations, treatment courses, and final visual outcomes were collected and analyzed. Visual acuity, postoperative complications and graft survivals were measured as outcomes. RESULTS: Of the 62 patients with AK in our study, 64.5% were medically treated while 35.5% underwent surgical treatment. In those with ring infiltrate, 52.4% patients could be successfully treated with medications. In eyes receiving penetrating keratoplasty, postoperative complications were more common in therapeutic penetrating keratoplasty (TPK) than those in optical penetrating keratoplasty (OPK) group (82.4% versus 40%, p = 0.04). The graft size was larger in TPK than that in OPK group (8.56 versus 7.83 mm, p = 0.002). Furthermore, post-operative glaucoma, which was the major complication, was found to be associated with larger graft size (p = 0.02) and dilated pupil/iris atrophy (p = 0.01). CONCLUSION: Even in advanced cases with ring infiltrate, eradication of infection with anti-amoebic drugs is possible. In those requiring keratoplasty, the surgical timing should be made meticulously considering graft size and signs of dilated pupil/iris atrophy in terms of post-operative glaucoma.

Therapeutic penetrating keratoplasty for microbial keratitis in Taiwan from 2001 to 2014.

PURPOSE: To study the surgical outcome of therapeutic penetrating keratoplasty (TPK) for medically uncontrolled microbial keratitis at a tertiary hospital in Taiwan over a 14-year period. METHODS: This is a retrospective case series study. Patients who underwent TPK at National Taiwan University Hospital in 2001-2014 were included. Patients were divided into 3 diagnostic groups: bacterial keratitis, fungal keratitis, and acanthamoeba keratitis. Each of the following criteria was evaluated: graft clarity at 1 month and 1 year postoperatively, cure of the disease, and anatomical success rate. RESULTS: A total of 107 TPKs were included. TPK eradicated the infection in 57/62 (91.9%) of bacterial keratitis, 33/41 (80.5%) of fungal keratitis, and 9/10 (90.0%) of acanthamoeba keratitis. 22/57 grafts (38.6%) of bacterial keratitis, 22/38 grafts (57.9%) of fungal keratitis, and 5/10 grafts (50.0%) of acanthamoeba keratitis remained clear at 1 year postoperatively. The 1-year graft survival rate did not significantly differ among these 3 groups. The leading causes of graft failure were late endothelial decompensation and graft reinfection. A higher percentage of graft clarity was achieved in grafts <8.5 mm in diameter than in larger grafts (55.4% vs. 31.4%, P = 0.027). Of the 14 patients with endophthalmitis at the time of TPK, the infection was successfully treated in 13 patients except 1 patient required evisceration. CONCLUSION: TPK is valuable in the management of medically uncontrolled microbial keratitis, although the 1-year graft survival rate is unsatisfactory. TPK combined with intravitreal antibiotics and vitrectomy is also a beneficial treatment strategy for patients with endophthalmitis secondary to microbial keratitis.

Bilateral corneal melting associated with topical diclofenac 0.1% after cataract surgery in a patient with Sjögren's syndrome.

A 79-year-old female with Sjögren's syndrome (SS) underwent phacoemulsification and lens implantation in both eyes within 2 days. Postoperatively, topical diclofenac 0.1% and tobramycin 0.3% were applied. She presented 10 days later with photophobia, large central corneal melting, and visual acuity of counting finger in both eyes. Diclofenac was discontinued, and systemic doxycycline and steroids were administered. Amniotic membrane transplantation was performed in the left eye with topical steroid and autologous serum 20%. Corneal melting gradually healed in 3 weeks, but the centers of both corneas became thin and opaque. Hyperopic shift and irregular corneal surface were more significant in the right eye than in the left eye. Vision recovered to 0.05 and 0.1 in the right and left eyes, respectively. Topical nonsteroidal anti-inflammatory drugs should be used with caution in cataract surgery in patients with SS.

Recurrent corneal erosion caused by retained sutures in blepharoplasty.

PURPOSE: To present recurrent corneal erosion (RCE) caused by late suture exposure after blepharoplasty. METHODS: Four patients who have unilateral RCE were found to have previous blepharoplasty. The RCE was associated with late suture exposure. The clinical courses, characteristics, methods to identify the suture exposure and treatment were presented. RESULTS: The clinical presentations including local erosion of upper bulbar conjunctiva, corneal abrasion lines, local corneal epithelial defects with rough border, and subepithelial opacity were noticed in all four patients. RCE symptoms exaggerated in eye blinking and did not respond to artificial tears treatment. Erosion recurred soon after the removal of therapeutic contact lenses. They underwent blepharoplasty 1-10 years before RCE emerged, and the RCE lasted 1-8 months before suture exposure was found. RCE healed within 1 week after suture removal. CONCLUSIONS: Suture exposure may occur several years after blepharoplasty and could cause RCE. Thorough exploration of the fornix by double eyelid eversion can identify the hidden sutures in such patients.

Reappraisal of the suitability of corneas from bacteremic donors for use in corneal transplants.

BACKGROUND: This study examined whether corneas from bacteremic donors could be used for corneal transplant. METHODS: Corneas donated to the National Eye Bank of Taiwan between 1 January 2014 and 30 June 2017 were included in this study. All the corneas had corneoscleral rim cultures during the retrieval process and were hypothermic preserved in the Optisol-GS storage medium. A microbial work-up flow chart was used for the sterility check of all grafts. Bacteremic donors were defined as those whose last blood culture before corneal donation was positive. The microbial contamination rates, the endothelial cell densities, the tissue utility rates and early complications after transplants were compared between the corneas from bacteremic versus non-bacteremic donors. RESULTS: 697 corneas from 356 donors were analysed, 70 of which were from bacteremic donors. The microbial contamination rates of the corneas from bacteremic and non-bacteremic donors (7.1% vs 9.1%)(p=0.30) were close. None of the contaminated corneas grew the same bacterial strains as those from their blood cultures. The corneas from bacteremic donors and non-bacteremic donors have similar endothelial cell densities (2931±297 cells/mm2 vs 2903 ± 470 cells/mm2) (p=0.63). Corneas from bacteremic and non-bacteremic donors shared a similar utility rate (98.6% vs 99.4%)(p=0.41). None of the corneas caused infectious complications after transplants. CONCLUSION: Our study showed that corneas from bacteremic and non-bacteremic donors have equally low contamination rates and are of the same quality in terms of endothelial cell density and safety.

Clinicopathologic correlation of ocular surface squamous neoplasia from a university hospital in North Taiwan 1994 to 2014.

BACKGROUND/PURPOSE: To describe the clinical and histologic characteristics of ocular surface squamous neoplasia (OSSN) and evaluate factors significant in recurrence at a university hospital in North Taiwan. METHODS: Patient charts, clinical features, and pathology records were retrospectively reviewed in patients with pathology-proved OSSN from January, 1994 to December, 2014. Clinicopathologic correlation was analyzed. RESULTS: Thirty-six patients were recruited. Mean age was 63.4 ± 13.0 (ranging from 23 to 87) years old. OSSN was predominant in men (21/36). Clinical appearances included papilliform in 17 eyes, gelatinous in 11 eyes, leukoplakic in 3 eyes, and 5 eyes in corneal intraepithelial neoplasia (CIN). Of 31 conjunctival OSSN, there were 4 in CIN I, 11 in CIN II, 13 in CIN III, and 3 in squamous cell carcinoma. Superior location was associated with higher-grade OSSN. Although statistical analysis was not significant, papilliform and multifocal lesions showed a trend of high-grade OSSN. The stages of tumor were 4, 5, 26, and 1 eye(s) in T1 to T4, respectively. Recurrence of disease occurred in 9 cases (25%) with mean recurrence time of 20.6 (range: 4 to 65) months. Multifocal lesion has a higher tendency for recurrence. CONCLUSION: Superior location was associated with high-grade OSSN, and papilliform OSSN might have a tendency of severe and invasive lesions. Multifocal lesions might be associated with higher-grade OSSN and higher recurrence rates.

Analysis of SmartPlug Insertion-Related Complications.

PURPOSE: To evaluate the complications and the treatment results of SmartPlug-related complications. METHODS: Retrospective review of all patients from a single medical hospital who received SmartPlug (Medennium, Inc., Irvine, CA) insertions from October 2007 to February 2014. All patients who developed SmartPlug-related canaliculitis and pyogenic granuloma were analyzed. Lacrimal irrigation with antibiotics was performed in most patients. RESULTS: Six hundred thirty-one eyes received SmartPlug insertion and 18 eyes developed SmartPlug-related complications (14 canaliculitis and 4 pyogenic granuloma). The mean time interval from insertion to development of the complications is 3.0 (0.5-6.9) years. Sixteen eyes received lacrimal irrigation with antibiotics, and all the eyes showed improvement without recurrence. The other two eyes had recurrence of granuloma pyogenica only after surgical excision. CONCLUSIONS: SmartPlug-related complications, including canaliculitis and granuloma pyogenica, required long-term follow-up. Most of the complications can be cured by lacrimal irrigation of antibiotics.

Postoperative intraocular lens opacification.

Intraocular lens (IOL) opacification is rare but may occur after non-Descemet stripping automated endothelial keratoplasty (n-DSAEK) or intravitreal air injection after pars plana vitrectomy (PPV). We reported two cases of IOL opacification within the pupillary region. Chart was retrospectively reviewed. The predisposing factors and the visual acuity were analyzed. The opacification was evaluated by anterior segment optical coherence tomography (AS-OCT). A 68-year-old healthy woman with pseudophakic bullous keratopathy underwent uneventful n-DSAEK in the right eye. Postoperative vision was 20/40. Nine months after surgery, fine granular deposits were seen in the anterior surface of IOL. The vision decreased to 20/50 but remained stable during 3-year follow-up. A 61-year-old man with diabetes mellitus received PPV and silicone oil tamponade for retinal detachment and vitreal hemorrhage after cataract surgery in the right eye. Removal of silicone oil and intravitreal air injection was performed, and postoperative vision was 20/100. Granular deposits were observed in hydrophobic acrylic IOL 1 month after surgery. The visual acuity decreased to 20/120. AS-OCT revealed hyperreflective materials in the anterior surface of IOL in both cases. An uncommon phenomenon of IOL opacification in the pupil region may occur after n-DSAEK or PPV, which may be associated with intraocular air injection or systemic diseases.

Mini-Scleral Lenses for Correction of Refractive Errors After Radial Keratotomy.

OBJECTIVE: To evaluate the factors affecting clinical outcomes of correcting cumulative refractive errors or irregular astigmatism after radial keratotomy (RK) using mini-scleral lenses. METHODS: We retrospectively analyzed 36 eyes receiving mini-scleral lenses after RK from July 2011 to June 2016. Analyses included age, refractive errors, best spectacle-corrected visual acuity (BSCVA), best contact lens-corrected visual acuity (BCLCVA), topographic indices, RK treatment zone diameter (TZD), power difference (PrD) within the RK treatment zone, and decentration distance (DD) of the RK treatment zone center. An increase of three lines or more of Snellen visual acuity was considered a successful fitting. RESULTS: Of the eyes fitted with mini-scleral lenses, the BCLCVA (logarithm of the minimum angle of resolution [logMAR] 0.19±0.22) was significantly better than the BSCVA (logMAR 0.47±0.30). Twenty-three patients (64%) had a successful fitting. There was no statistically significant difference between successful and unsuccessful fittings with regard to age, prefitting refractive error, BSCVA, corneal astigmatism, simulated steep/flat K values, surface regularity index, TZD, or PrD. However, successful fittings had better centration of treatment zones with an average DD of 0.54±0.44 mm compared with a DD of 0.92±0.53 mm in the unsuccessfully fitted eyes. In addition, our case series showed that there was a negative impact on fitting outcomes in the presence of small central clear zones resulting from central incisions or scars. CONCLUSIONS: Although decentration of the RK treatment zone and small central clear zones were related to less optimal fitting results, mini-scleral lenses are a feasible option to correct cumulative refractive errors and irregular astigmatism in post-RK patients.

Combination of phototherapeutic keratectomy and wavefront-guided photorefractive keratectomy for the treatment of Thiel-Behnke corneal dystrophy.

Phototherapeutic keratectomy (PTK) has been used to treat anterior corneal dystrophy but may cause hyperopic shift or corneal high-order aberration. We describe the successful treatment of a case of a 43-year-old female with Thiel-Behnke corneal dystrophy, using PTK followed by wavefront-guided photorefractive keratectomy (PRK). The patient had high corneal aberration and hyperopic shift after PTK in both eyes. The corneal surface regularity index and surface asymmetric index increased after PTK and decreased after wavefront-guided PRK. Vision improved from preoperative 20/400 and 20/60 to postoperative 20/20 and 20/25 in the right eye and the left eye, respectively. Additional wavefront-guided PRK may enhance the effects of PTK by reducing irregular corneal surfaces and by correcting PTK-induced hyperopic shift.