Assessment of a Novel Semi-Automated Algorithm for the Quantification of the Parafoveal Capillary Network.

Introduction: We present a novel semi-automated computerized method for the detection and quantification of parafoveal capillary network (PCN) in fluorescein angiography (FA) images. Material and Methods: An algorithm detecting the superficial parafoveal capillary bed in high-resolution grayscale FA images and creating a one-pixel-wide PCN skeleton was developed using MatLab software. In addition to PCN detection, capillary density and branch point density in two circular areas centered on the center of the foveal avascular zone of 500µm and 750µm radius was calculated by the algorithm. Three consecutive FA images with distinguishable PCN from 56 eyes from 56 subjects were used for analysis. Both manual and semi-automated detection of the PCN and branch points was performed and compared. Three different intensity thresholds were used for the PCN detection to optimize the method defined as mean(I)+0.05*SD(I), mean(I) and mean(I)-0.05*SD(I), where I is the grayscale intensity of each image and SD the standard deviation. Limits of agreement (LoA), intraclass correlation coefficient (ICC) and Pearson's correlation coefficient (r) were calculated. Results: Using mean(I)-0.05*SD(I) as threshold the average difference in PCN density between semi-automated and manual method was 0.197 (0.316) deg-1 at 500µm radius and 0.409 (0.562) deg-1 at 750µm radius. The LoA were -0.421 to 0.817 and -0.693 to 1.510 deg-1, respectively. The average difference of branch point density between semi-automated and manual method was zero for both areas; LoA were -0.001 to 0.002 and -0.001 to 0.001 branch points/degrees2, respectively. The other two intensity thresholds provided wider LoA for both metrics. The semi-automated algorithm showed great repeatability (ICC>0.91 in the 500µm radius and ICC>0.84 in the 750µm radius) for both metrics. Conclusion: This semi-automated algorithm seems to provide readings in agreement with those of manual capillary tracing in FA. Larger prospective studies are needed to confirm the utility of the algorithm in clinical practice.

Perifoveal capillary network quantification in young diabetic patients with subclinical or no retinopathy.

OBJECTIVE: To assess the morphology of perifoveal capillary network with quantitative parameters in young patients with diabetes mellitus type I (DM I) using an algorithm. METHODS: Fifty-three images (33 eyes of 33 DM I patients and 20 eyes of 20 non-DM controls) were chosen retrospectively from the University Hospital of Heraklion digital fluorescein angiography database. An additional group consisting of patients with advanced DR abnormalities was included in our analysis to investigate whether our method detects alterations when they are present. The developed algorithm allows the user to manually trace the perifoveal capillary network by selecting with the cursor in a 5° × 5° subimage field of the original image, including the foveal avascular zone (FAZ), and provides measurements of the capillary density, the branch point density, and the FAZ surface in this subarea. RESULTS: The age in the patient group was 19 ± 5 years; age was 21 ± 8 years for the control group. Patients had a history of DM I for 11 ± 5 years. The mapping revealed a perifoveal capillary density of 2.494 ± 0.559 deg-1 in the DM I group versus 2.974 ± 0.442 deg-1 in the control group (p = 0.005). The branch point density was 3.041 ± 0.919 branch points/deg2 and 3.613 ± 1.338 branch points/deg2 in each group, respectively (p = 0.128). The FAZ area was 0.216 ± 0.061 deg2 in the diabetic group and 0.208 ± 0.060 deg2 in the control group (p = 0.672). CONCLUSIONS: The selected quantitative parameters tend to increase or decrease in diabetic patients, in agreement with previous studies. Among the parameters, capillary density may represent the most sensitive metric for the detection of very early diabetic changes. Further improvement of the method could contribute to the development of an automated processing tool for capillary network quantitative assessment.

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.

Quantification of parafoveal capillary network using a semi-automated algorithm.

OBJECTIVE: The quantification of the morphology of the parafoveal capillary network (PCN) in fluorescein angiography (FA) images using a novel semi-automated computerized method. MATERIAL AND METHODS: Using the MatLab R2011 a software we developed an algorithm that detects automatically the parafoveal capillary bed and its branch points as depicted in FA images creating simultaneously an one-pixel-wide skeleton of it. The detection process starts after delineating manually the foveal avascular zone in a cropped 1500µm*1500µm subimage resulting from the original FA image. Thereafter the algorithm calculates the capillary density and the branch points in a circle area with 1000µm radius. The method was also applied on FA images from subjects without diabetes mellitus, diabetics without diabetic retinopathy (DR) signs, patients with non-proliferative DR and patients with proliferative DR in order to assess the PCN morphology metrics for the studied groups. RESULTS: The PCN density and the parafoveal capillary branch points were estimated for the mentioned subject groups and any significant differences among them were assessed as well. CONCLUSIONS: The described method could serve as a potential tool for the diagnosis and monitoring of PCN diseases and subclinical abnormalities. The assessed metrics reflect the capillary abnormalities in the central 1000µm area across different DR stages.

Anterior segment applications of in vivo confocal microscopy.

PURPOSE: To review the current literature on in vivo confocal microscopy anterior segment applications (cornea, conjunctiva, and glaucoma) and discuss its advantages in different pathological conditions. METHODS: Review of selected relevant literature on in vivo confocal microscopy and its different applications. RESULTS: In vivo confocal microscopy can be used to visualize most layers of the cornea and conjunctiva, providing excellent resolution. In the past, it was mainly utilized as a research tool; lately there seems to be an increasing interest for clinical applications; confocal microscopy aids the diagnosis and follow-up of many anterior segment disorders, such as corneal dystrophies, corneal and conjunctival inflammatory and neoplastic diseases, glaucoma patients, and assessment of surgical procedures. CONCLUSION: In vivo confocal microscopy is an important addition to the ophthalmic diagnostic tools with several anterior segment applications. Its clinical applications are being continuously explored and are quickly expanding to cover many new pathological aspects.

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.

Macular retinal and nerve fiber layer thickness in early glaucoma: clinical correlations.

PURPOSE: Previous studies have evaluated macular retinal thickness (RT) and nerve fiber layer thickness (RNFLT) changes in early glaucoma using elaborate optical coherence tomography (OCT) scanning protocols. MATERIALS AND METHODS: This study examines RT and RNFLT using standard scanning protocols in early glaucoma. In this prospective, nonrandomized case series, 95 eyes of 95 patients were evaluated, including 29 nonglaucomatous subjects (control group), 34 glaucoma suspects, and 32 early manifest glaucoma patients. RT and RNFLT were measured using scanning fast macular thickness map and Fast RNFLT (3.4) protocols on a 1.70 mm radius around the macular center (respectively) in all four quadrants. The fast RNFLT (3.4) protocol was transposed on the macula from the peri-papillary area. Data were statistically analyzed for differences between groups, and for correlations between parameters. P<0.5 was statistically significant. RESULTS: Both early manifest glaucoma patients and glaucoma suspects had significantly lower RT than controls in all quadrants. RNFLT differences in all quadrants were not statistically significant (P>0.05). RT was significantly inversely correlated with axial length in early manifest glaucoma patients and glaucoma suspects but not in controls. CONCLUSIONS: The finding that RT was significantly lower in early manifest glaucoma patients and glaucoma suspects indicates that the transposition of the OCT fast RNFL thickness (3.4) protocol from the peri-papillary area to the peri-macular area can be used for early glaucoma diagnosis. Intraretinal changes in early glaucoma, likely precede nerve fiber changes.

Posterior linear stromal haze formation after simultaneous photorefractive keratectomy followed by corneal collagen cross-linking.

PURPOSE: To report the development of posterior linear stromal haze after simultaneous photorefractive keratectomy (PRK) followed by corneal collagen cross-linking (CXL). METHODS: Combined simultaneous customized PRK followed by corneal collagen cross-linking was performed in 23 patients (28 eyes) with keratoconus. Corneas were examined biomicroscopically and by means of confocal microscopy before surgery and 1, 3, 6, 9, and 12 months after surgery. RESULTS: Posterior linear stromal haze was observed clinically (slit lamp biomicroscopy) one month after surgery in 13 of 28 eyes (46.42%). No corneal edema or anterior haze formation was evident. Confocal microscopy revealed in those 13 eyes a hyperreflective area at the level of the posterior stroma 1 month after combined treatment. Both slit lamp examination and corneal confocal microscopy follow-up demonstrated a gradual anterior movement and a decrease in reflectance of this finding. At 12 months this posterior linear stromal haze, despite its anterior movement and decreased density, did not completely disappear at slit lamp and confocal microscopy analysis. CONCLUSIONS: Posterior linear stromal haze formation may appear after simultaneous PRK followed by CXL in patients with keratoconus. This finding seems to gradually become less dense and slowly moves toward the anterior stroma.

Interface Haze Formation After Ultra Thin Flap Laser in Situ Keratomileusis.

In this case series, five patients (10 eyes) underwent laser in siter keratomileusis (LASIK) for the correction of moderate myopia and astigmatism with the Schwind Carriazo Pendular microkeratome 90 mum head. Flap (superior hinged) thickness measured intraoperatively was assessed less than 70 mum in all eyes. On first month's postoperative examination, subepithelial mild corneal haze with consequent myopic regression was found in all patients. A significant improvement of haze formation and residual refractive error were observed during the following postoperative months. In conclusion, post-LASIK subepithelial corneal haze after thin flap creation is a temporarily potential complication that could affect patient's refractive error during the first postoperative month.

Nine-year follow-up of intacs implantation for keratoconus.

PURPOSE: To present a case of nine- year bilateral Intacs (Addition Technology, Inc, Fremont, California, USA) implantation for early stage keratoconus. METHODS: A 25-year-old male underwent bilateral Intacs implantation for the management of keratoconus and hardcontact-lens intolerance (stage 1) in 1999. RESULTS: Nine years postoperatively, spherical equivalent refraction changed from preoperative -0.75 and -2.25 to +0.75 and -1.25 for the right and the left eye, respectively. UCVA was improved from 20/50 to 20/25 in the right and from 20/200 to 20/32 in the left eye. BSCVA of 20/20 in the right eye maintained stable in comparison with the Pre-Intacs BSCVA, while BSCVA was improved from 20/25 to 20/20 in the fellow eye. No early or late complications were observed. CONCLUSIONS: Nine years after bilateral Intacs implantation for the management of early stage keratoconus, there was a significant improvement and postoperative stability in patient's visual acuity. No long-term, sight-threatening complications were identified during follow-up.

Diffuse lamellar keratitis after corneal crosslinking in a patient with post-laser in situ keratomileusis corneal ectasia.

A 27-year-old man presented with corneal ectasia in his left eye 4 years after myopic laser in situ keratomileusis (LASIK) and was treated with riboflavin-ultraviolet-A (crosslinking). During the first post-treatment days, diffuse lamellar keratitis (DLK) (stage III) developed. The microbiology culture was negative. After intensive treatment with topical corticosteroids, the DLK resolved during the following 2 weeks. Crosslinking for post-LASIK corneal ectasia may induce DLK. Early diagnosis and appropriate treatment with intensive topical corticosteroids is essential to successfully manage this post-crosslinking complication.

Nine-year follow-up of a posterior chamber phakic IOL in one eye and LASIK in the fellow eye of the same patient.

PURPOSE: To compare the long-term results (9 years) of LASIK in one eye and phakic intraocular lens (implantable contact lens [ICL]) implantation in the fellow eye of the same patient. METHODS: A patient with high myopia underwent LASIK with a MEL 60 excimer laser in one eye (spherical equivalent refraction -9.75 diopters [D], 5-mm optical zone with no transition zone) and phakic intraocular lens (STAAR Collamer implantable contact lens [ICL]) implantation (spherical equivalent refraction -9.50 D) in the fellow eye. RESULTS: At 9 years postoperatively, the mean spherical equivalent refraction was -1.00 in the eye with the ICL and -1.75 D in the eye that underwent LASIK. During the first 6 postoperative months in the LASIK eye, refraction regressed, but remained stable during the remainder of follow-up. Uncorrected visual acuity was 20/25 in the eye with the ICL and 20/30 in the LASIK eye, whereas best spectacle-corrected visual acuity was 20/20 in both eyes. Less night vision problems (glare and halos) were experienced in the eye with the ICL compared to the LASIK eye. Although the patient initially preferred the LASIK procedure, at last follow-up 9 years postoperatively, increased overall satisfaction was reported for the eye with the ICL compared to the LASIK eye. CONCLUSIONS: Nine years after treatment of high myopia with the ICL and LASIK in the same patient, better quality of vision, stability, and satisfaction score were achieved in the eye with the ICL compared to the eye that had undergone LASIK. No long-term sight-threatening complications were found during followup.

Fifteen-year follow-up after LASIK: case report.

PURPOSE: To present 15-year follow-up of one of the first LASIK-treated patients. METHODS: A 40-year-old woman underwent LASIK in the left eye for myopia in July 1991. RESULTS: Fifteen years after LASIK, spherical equivalent error was statistically significantly reduced from preoperative -8.75 -3.75 x 025 degrees to postoperative -4.25 -2.75 x 010 degrees. Six months postoperatively, refractive and topographic stability was obtained and remained stable during follow-up with no significant changes between interval mean time (-3.75 -3.00 x 020 degrees 6 months postoperatively to -4.25 -2.75 x 010 degrees 15 years postoperatively). No early or late postoperative complications were observed, and confocal microscopy revealed a regenerated nerve plexus and normal cornea. However, increased scattering and presence of debris were observed at the flap interface even after 15 years. Despite moderate predictability (residual refractive error) and small optical zone, the patient was satisfied with final outcome. CONCLUSIONS: One of the first LASIK-treated patients was presented 15 years after surgery. LASIK in this patient had low predictability, although refractive and topographic stability occurred after the sixth postoperative month. No long-term, sight-threatening complications were identified during follow-up.

Endothelial cell density after photorefractive keratectomy for moderate myopia using a 213 nm solid-state laser system.

PURPOSE: To evaluate whether photorefractive keratectomy (PRK) for moderate myopia using a solid-state laser with a wavelength of 213 nm alters the corneal endothelial cell density. SETTING: University refractive surgery center. METHODS: The corneal endothelium was analyzed preoperatively and 1, 6, and 12 months postoperatively using corneal confocal microscopy (modified HRT II with a Rostock Cornea Module, Heidelberg Engineering) in 60 eyes (30 patients). Patients were randomized to have myopic PRK using a 213 nm wavelength solid-state laser (study group) or a conventional 193 nm wavelength excimer laser (control group). Three endothelial images were acquired in each of 30 preoperative normal eyes to evaluate the repeatability of endothelial cell density measurements. Repeated-measures analysis of variance was used to compare the variations in endothelial cell density between the 2 lasers and the changes in endothelial cell density over time. RESULTS: There were no statistically significant differences in sex, age, corneal pachymetry, attempted correction, preoperative endothelial cell density, or postoperative refractive outcomes (uncorrected visual acuity, best spectacle-corrected visual acuity, and spherical equivalent refraction) between the 2 groups (P>.05). The coefficient of repeatability of endothelial cell density was 131 cells/mm(2). The measured endothelial cell count per 1.0 mm(2) did not significantly change up to 1 year postoperatively in either group (both P>.05). No statistically significant difference was found between the 2 groups in any postoperative interval (P>.05). CONCLUSION: Photorefractive keratectomy for moderate myopia using a 213 nm wavelength solid-state laser or a conventional 193 nm wavelength excimer laser did not significantly affect corneal endothelial density during the 1-year postoperative period.

Herpetic keratitis with iritis after corneal crosslinking with riboflavin and ultraviolet A for keratoconus.

A 21-year-old woman had crosslinking for keratoconus in the right eye; the left eye was scheduled for penetrating keratoplasty. Five days postoperatively, she presented with geographic epithelial keratitis and iritis. Analysis of tear samples by polymerase chain reaction confirmed the diagnosis. The patient was treated with oral steroids and acyclovir, with significant improvement. Two months postoperatively, the visual acuity was improved and there was no evidence of herpetic disease recurrence. Crosslinking can induce herpetic keratitis with iritis even in patients with no history of herpetic disease. Early diagnosis and proper treatment are essential for a favorable outcome.

Idiopathic recurrence of diffuse lamellar keratitis after LASIK.

PURPOSE: To report a case of late recurrence of bilateral diffuse lamellar keratitis (DLK) after LASIK. METHODS: A 39-year-old woman presented in the early postoperative period with bilateral DLK after hyperopic LASIK and was treated with topical steroids. One year after and with no obvious cause (idiopathic), recurrence of the same stage (stage III) of disease was observed. RESULTS: Slit-lamp examination revealed diffuse, multifocal, and granular haze in the interface. The microbiology culture was negative. Confocal microscopy demonstrated multiple activated keratocytes, debris, and inflammatory cells adjacent to the flap interface. After intense treatment with topical corticosteroids, DLK resolved and corneal transparency was achieved with complete restoration of visual acuity. CONCLUSIONS: Diffuse lamellar keratitis may recur in LASIK patients with previous episodes without an obvious cause (idiopathic). Early diagnosis and treatment with topical corticosteroids can achieve complete resolution without visual loss--even in advanced stages of DLK.

Long-term results of thin corneas after refractive laser surgery.

PURPOSE: To report the long-term refractive results of photorefractive keratectomy (PRK) and laser in situ keratomileusis (LASIK) in patients with thin corneas. DESIGN: A long-term, retrospective, non-randomized follow-up study. METHODS: Sixty-three patients (124 eyes) (28 males and 35 females), who had a preoperative central corneal thickness (CCT) of less than 500 microns and completed at least one year of follow-up examinations after surgery. Thirty-five patients (68 eyes) underwent PRK and 28 patients (56 eyes) underwent LASIK. RESULTS: Mean preoperative corneal pachymetry was 484.95 +/- 6.65 microm (range, 470 to 498 microm) and 482.38 +/- 10.73 microm (range, 453 to 499 microm) for LASIK and PRK, respectively. No intraoperative complications were found in both groups. None of the included eyes developed postrefractive corneal ectasia. The mean predictability for the PRK group was 0.08 diopters (D) with a standard deviation of 0.40 D (range, -1.38 to 1.00 D), and the mean predictability for the LASIK group was 0.14 D with a standard deviation of 0.55 D (range, -1.25 to 1.33 D). CONCLUSIONS: Refractive laser surgery with LASIK or PRK in patients with thin corneas (less than 500 microm) seems to be a safe and predictable technique for myopic refractive corrections.

One-year results of photorefractive keratectomy and laser in situ keratomileusis for myopia using a 213 nm wavelength solid-state laser.

PURPOSE: To study the long-term results of photorefractive keratectomy (PRK) and laser in situ keratomileusis (LASIK) in low to moderate myopic corrections using the Pulzar Z1 system (CustomVis), a 213 nm wavelength solid-state laser. SETTING: University refractive surgery center. METHODS: This prospective noncomparative case series comprised 20 patients (40 eyes) who had refractive surgery using the Pulzar Z1 laser system. Manifest refraction, uncorrected visual acuity, best spectacle-corrected visual acuity (BSCVA), safety, predictability, stability, and confocal microscopy images were evaluated. RESULTS: Ten patients (20 eyes) had PRK and 10 patients (20 eyes) had LASIK. The mean follow-up was 13.9 months +/- 1.1 (SD) (range 12 to 17 months) and 14.6 +/- 1.2 months (range 12 to 18 months) in the PRK group and LASIK group, respectively. No eye lost a line of Snellen BSCVA during the follow-up period; 2 eyes (10%) gained 2 Snellen lines. There was a statistically significant decrease in spherical equivalent manifest refraction postoperatively in both groups (P<.05). Refractive stability was obtained during the first postoperative month and remained stable during the follow-up period, with no significant changes between any interval in both groups (P>.05). At the last follow-up, 95% of all eyes were within +/-1.00 diopter of emmetropia. No late postoperative complications were observed. CONCLUSION: Refractive surgery using the Pulzar Z1 213 nm wavelength solid-state laser was a safe, effective procedure in the treatment of low to moderate myopia.

Unilateral corneal ectasia after laser in situ keratomileusis in a patient with uncomplicated photorefractive keratectomy in the fellow eye.

We report a patient treated for low myopia with laser in situ keratomileusis (LASIK) in one eye and photorefractive keratectomy (PRK) in the fellow eye. Corneal ectasia developed in the LASIK-treated eye. Preoperative corneal pachymetry, topography, and attempted correction were similar in both eyes. In patients whose corneas may be predisposed to instability, PRK may be a safer alternative procedure than LASIK.