Michael O’Keefe

Characterization of changes in blood vessel width and tortuosity in retinopathy of prematurity using image analysis

Many retinal diseases are characterised by changes to retinal vessels. For example, a common condition associated with retinopathy of prematurity (ROP) is so-called plus disease, characterised by increased vascular dilation and tortuosity. This paper presents a general technique for segmenting out vascular structures in retinal images, and characterising the segmented blood vessels. The segmentation technique consists of several steps. Morphological preprocessing is used to emphasise linear structures such as vessels. A second derivative operator is used to further emphasise thin vascular structures, and is followed by a final morphological filtering stage. Thresholding of this image is used to provide a segmented vascular mask. Skeletonisation of this mask allows identification of points in the image where vessels cross (bifurcations and crossing points) and allows the width and tortuosity of vessel segments to be calculated. The accuracy of the segmentation stage is quite dependent on the parameters used, particularly at the thresholding stage. However, reliable measurements of vessel width and tortuosity were shown using test images. Using these tools, a set of images drawn from 23 subjects being screened for the presence of threshold ROP disease is considered. Of these subjects, 11 subsequently required treatment for ROP, 9 had no evidence of ROP, and 3 had spontaneously regressed ROP. The average vessel width and tortuosity for the treated subjects was 96.8 microm and 1.125. The corresponding figures for the non-treated cohort were 86.4 microm and 1.097. These differences were statistically significant at the 99% and 95% significance level, respectively. Subjects who progressed to threshold disease during the course of screening showed an average increase in vessel width of 9.6 microm and in tortuosity of +0.008. Only the change in width was statistically significant. Applying a simple retrospective screening paradigm based solely on vessel width and tortuosity yields a screening test with a sensitivity and specificity of 82% and 75%. Factors confounding a more accurate test include poor image quality, inaccuracies in vessel segmentation, inaccuracies in measurement of vessel width and tortuosity, and limitations inherent in screening based solely on examination of the posterior pole.

Visual outcomes and complications of posterior chamber intraocular lens implantation in the first year of life

Purpose: To document the visual outcome and postoperative complications in infants who had congenital cataract surgery with posterior chamber intraocular lens (PC IOL) implantation in the first year of life. Setting: The Childrens Hospital, Dublin, Ireland. Methods: Twenty‐seven eyes of 20 infants were reviewed. Seven infants (14 eyes) had bilateral congenital cataract and 13 (13 eyes), uniocular cataract. The mean age at surgery was 4 months (range 3 weeks to 11 months). A standard surgical technique involved anterior capsulorhexis, phacoemulsification with or without posterior capsulorhexis with in‐the‐bag PC IOL implantation, and no anterior vitrectomy. Surgery was performed by 1 surgeon. The mean follow‐up was 41 months (range 6 to 88 months). Results: The main complication was lens reproliferation into the visual axis. Of the 11 eyes that did not have a primary posterior capsulorhexis, 10 had 1 or more capsulotomies. Seven required a neodymium:YAG (Nd:YAG) laser capsulotomy a mean of 6 months postoperatively, and 2 had 2 Nd:YAG capsulotomies. Six eyes also had a surgical capsulotomy when the membrane was deemed too thick for further laser treatment. Fourteen of 25 eyes had a primary posterior capsulorhexis; 8 had no further intervention. Four eyes had persistent hyperplastic primary vitreous (PHPV), 3 required a surgical capsulotomy, 2 had an Nd:YAG laser capsulotomy, 2 had an anterior vitrectomy, and 1 developed open‐angle glaucoma. There was a mean refractive shift of 6.0 diopters after a mean follow‐up of 41 months, with most of the myopic shift occurring in the first 24 months. Conclusions: Visual axis reopacification was the main complication of IOL implantation in infants, with PHPV leading to more complications and repeat procedures. Anterior vitrectomy appeared to reduce the reoperation rate. Results indicate that primary posterior capsulorhexis is important and Nd:YAG capsulotomy is not satisfactory in infants. In addition, the reduction in glaucoma with IOL implantation, if borne out over the long term, is a significant advantage in cases of congenital cataract.

Primary posterior capsulorhexis without anterior vitrectomy in pediatric cataract surgery : Longer term outcome

PURPOSE To assess the effectiveness of primary posterior capsulorhexis without anterior vitrectomy in preventing posterior capsule opacification (PCO) in pediatric cataract surgery. SETTING Childrens Hospital, Dublin, Republic of Ireland. METHODS The study comprised 32 eyes of 22 pediatric patients who had cataract extraction between 1994 and 1998. Extracapsular cataract extraction was performed using radiofrequency diathermy capsulorhexis to the anterior and posterior capsules without an anterior vitrectomy. Posterior chamber intraocular lens implantation was performed in 20 eyes. There were 23 congenital, 6 developmental, and 3 traumatic cataracts. RESULTS Patient age ranged from 1 month to 12 years. Mean follow-up was 19 months (range 6 to 50 months). Twenty-seven of 32 eyes (84.4%) had a clear visual axis at last follow-up. Five eyes required a neodymium: YAG capsulotomy, which was performed a mean of 5 months postoperatively (range 1 to 9 months). The incidence of PCO requiring capsulotomy was 15.6%. CONCLUSION Primary posterior capsulorhexis without anterior vitrectomy was safe and effective, with a low reopacification rate. Long-term follow-up of this patient cohort is necessary.

Visual outcome and complications of bilateral intraocular lens implantation in children

Purpose: To determine the safety and efficacy of bilateral intraocular lens (IOL) implantation in children. Setting: Tertiary referral pediatric ophthalmology department. Methods: This retrospective study comprised 13 children (26 eyes) who had bilateral cataract surgery with IOL implantation. Patients were divided into 2 groups: congenital cases, diagnosed during the first year of life, and developmental cases, diagnosed after 1 year of age. All patients had small incision phacoemulsification with primary implantation of a poly(methyl methacrylate) or a foldable acrylic IOL. Primary posterior capsulotomy was performed in 16 eyes (61.5%). Results: Age at surgery ranged from 1 week to just under 8 years. Seven patients (53.8%) had a systemic diagnosis: Downs syndrome (n = 4); developmental delay or cerebral atrophy (n = 3). Five children with systemic problems could not cooperate with formal vision testing; 2 could fix and follow bilaterally, and 3 had central, steady, and maintained vision bilaterally. In the congenital group, 37.5% of eyes attained a visual acuity of 20/20 and 87.5%, 20/120 or better. In the developmental group, formal vision testing was possible in 4 children. Five eyes (83.3%) attained a visual acuity of 20/40 or better. Thirteen eyes (50.0%) required posterior capsulotomy. Primary posterior capsulotomy reduced the incidence of posterior capsule opacification (PCO), but there was no correlation between PCO and IOL material. One patient developed glaucoma bilaterally. Conclusion: Bilateral IOL implantation was safe and produced good visual results in children of all ages with bilateral cataract.

Myopic and hyperopic laser in situ keratomileusis retreatments : Indications, techniques, limitations, and results

Purpose: To assess the efficacy of myopic and hyperopic laser in situ keratomileusis (LASIK) retreatment procedures. Setting: Mater Private Hospital, Dublin, Ireland. Methods: Retreatment was defined as either lifting the previously created flap or when this was not possible, cutting a new flap. Fifty‐six patients were retreated, 17 with hyperopia (Group 1) and 39 with myopia (Group 2). The mean preoperative spherical equivalent in Group 1 was +3.79 diopters (D) ± 1.53 (SD) (range +1.75 to +8.12 D) and in Group 2, −5.46 ± 2.87 D (range −0.38 to −15.25 D). Results: The indications for retreatment were undercorrection, decentration, epithelial ingrowth, and central island. Postoperatively, the mean spherical equivalents in Groups 1 and 2 were +1.11 ± 2.02 D (range −1.75 to +5.50 D) and −1.02 ± 2.20 D (range +4.75 to −9.00 D), respectively. In Group 1, the uncorrected visual acuity (UCVA) was 6/12 or better in 5.8% preoperatively and in 35% postoperatively. In Group 2, the UCVA was 6/12 or better in 5.1% preoperatively and in 59.0% postoperatively. Although 29% of the hyperopic eyes and 8% of the myopic eyes lost 1 Snellen line of best corrected visual acuity (BCVA), there was an improvement (of 1 or more lines) in BCVA in 12% and 49%, respectively. In cases that were decentered preoperatively, the postoperative optical zone ablation centration was better in 85.7% of Group 1 eyes and 61.5% of Group 2 eyes. Corneal complications following retreatment included peripheral scarring, epithelial ingrowth, Bowmans folds, and keratectasia. Conclusions: Both myopic and hyperopic retreatments resulted in a stable refractive outcome. Myopic retreatments were superior to hyperopic retreatments in both efficacy and safety.

Preloaded refractive-addition corneal inlay to compensate for presbyopia implanted using a femtosecond laser: one-year visual outcomes and safety.

Purpose To report the results of the Icolens corneal inlay 12 months after implantation. Setting Department of Refractive Surgery, Mater Private Hospital, Dublin, Ireland. Design Prospective case series. Methods The inlay was implanted in the nondominant eye of emmetropic patients through a femtosecond laser–created corneal pocket. Results The mean uncorrected near visual acuity (UNVA) in the surgical eye (n = 52) improved from N18/N24 preoperatively to N8 postoperatively (P = .000); all patients had a UNVA of N16 or better and 9 (17%), of N5 or better. The uncorrected distance visual acuity (UDVA) in the surgical eye increased from 0.05 logMAR ± 0.12 (SD) preoperatively to 0.22 ± 0.15 logMAR postoperatively (P = .000). There was a mean loss of 1.67 ± 1.77 lines of UDVA (P = .000). Binocularly, there was a mean gain of 0.48 ± 1.16 lines of UDVA postoperatively (P = .000), with 22 patients (42%) gaining more than 1 line. The mean loss of corrected distance visual acuity postoperatively was 1.78 ± 1.04 lines (P = .000). There was no significant change in corneal topography or endothelial cell count. On the satisfaction survey, 90% of patients reported being happy (“yes” or “rather yes”) with the overall procedure in general. Eleven implants were explanted because of minimal improvement in UNVA. No significant adverse events were reported throughout the study. Conclusion The new refractive‐addition corneal inlay effectively corrected presbyopia in emmetropic presbyopic patients. Financial Disclosure No author has a financial or proprietary interest in any material or method mentioned.

Complications and Visual Prognosis in Children with Aniridia

PURPOSE To characterize the ophthalmological findings, assess surgical outcomes, and review visual outcomes in aniridia. METHODS A retrospective case review was performed and data were collected, including patient demographics, incidence of aniridia-associated keratopathy, glaucoma, cataract, retinal breaks or detachments, optic nerve hypoplasia, macular hypoplasia, poor vision, and nystagmus. All outcomes from surgery, including penetrating keratoplasty, trabeculectomy, Ahmed valve insertion, and cataract extraction, were recorded. RESULTS Six children (12 eyes) had corneal abnormalities, 4 had optic nerve hypoplasia, 9 had nystagmus, and 2 had retinal detachments. Four patients (7 eyes) required penetrating keratoplasty. Five patients (9 eyes) developed glaucoma and only 1 of the 4 trabeculectomies performed succeeded. Of the 6 Ahmed valve procedures performed, all succeeded in maintaining a satisfactory intraocular pressure but some required needling and 5-fluorouracil. Eight patients developed cataract and 7 required surgery. Visual outcomes were poor despite treatment. Nine patients had Snellen acuity of 6/60 or less and required low visual aids to function. CONCLUSION Aniridia is a disorder that requires multiple surgeries. It has a poor visual prognosis despite early diagnosis and aggressive management. Newer techniques such as Ahmed valves and Boston keratoprostheses offer hope, but its proliferative nature makes treatment difficult.

Foldable iris‐fixated intraocular lens implantation in children

Purpose:  To describe the results of foldable iris‐fixated intraocular lens (IOL) implantation in children.

Ten year follow up of laser in situ keratomileusis for all levels of myopia

and 3, respectively, at the initial tonometry session, with all cases exceeding the cut-off of 1.6 mmHg determined by Golnik and Miller, although the suitability of this cut-off value has not been tested in DCT. In cases with a CSDAVF, intrasinus thrombi and thickening of the sinus wall caused by abnormal arteriovenous flow could occlude the existing venous drainage routes. In case 2 with a relatively longstanding left CSDAVF was accompanied by blood reflux to the opposite SOV through the ICS. Accordingly, gradual development of an ICS channel toward the contralateral CS because of a continuous hemostatic pressure increase in the ipsilateral CS of the fistula, which is augmented by subsequent occlusion of physiologic drainage routes of CS, may explain the gradual decrease in OPA OS and reciprocal increase of the OPA OD after the initial tonometry session in case 1. In addition, drainage of the postcanalitic venous system, i.e. the episcleral veins, and the choroidal venous system, i.e. the vortex veins, the status of which mostly reflect the IOP and OPA (Bynke & Schéle 1967), respectively, into the SOV could be affected to varying degrees in each subject. Thus, the discrepancy in the kinetics between the preoperative IOP and OPA in case 1 may be explained by the difference in blood reflux between the postcanalitic and choroidal venous systems. Accordingly, the OPA may be an independent indicator from the IOP for assessing the hemodynamic status of CSDAVFs.

Tear Osmolarity in Premature Infants

PURPOSE To measure and report tear osmolarity in premature infants and to assess the change, if any, that occurs with increasing maturity. METHODS In a prospective study of consecutive infants born at less than 37 weeks gestational age undergoing screening for retinopathy of prematurity, serial measurements of tear osmolarity were obtained at preterm, term, and 3 months post-term. Mean ± standard deviation tear osmolarity and percentage of infants with tear osmolarity value greater than 308 and greater than 316 mOsm/L were calculated at each stage of maturity. RESULTS Twenty-five premature infants of mean post-conceptional age 33.5 weeks and mean birth weight 1,159 ± 259 g were tested. Mean tear osmolarity was 296 ± 19.1, 302.8 ± 18, and 301.1 ± 20.9 mOsm/L at pre-term, term, and post-term, respectively. There was no significant effect for time on tear osmolarity values (P = .59). Tear osmolarity was greater than 308 mOsm/L in 32% and greater than 316 mOsm/L in 16%. CONCLUSION Mean tear osmolarity in premature infants is within the expected normal range for adults and shows no significant change at term or post-term. More than two-thirds of premature infants have tear osmolarity values below the suggested diagnostic cut-offs for dry eye disease in adults. Most preterm infants do not have a dry eye based on assessment of tear osmolarity.