Biomedical subjects

Caitriona Kirwan

Publications and source records attributed to Caitriona Kirwan.

6 recordsLinked to original sources

PubMed2006

Corneal hysteresis and intraocular pressure measurement in children using the reichert ocular response analyzer.

PURPOSE: To examine corneal hysteresis in children with normal eyes and congenital glaucoma and assess intraocular pressure (IOP) measurement with the Reichert Ocular Response Analyzer (RORA). DESIGN: Observational, cross-sectional study. METHODS: setting: Clinical practice. patients: Corneal hysteresis and intraocular pressure (Goldmann correlated [IOPg] and corneal compensated [IOPcc]) were recorded with RORA. IOP was also measured by Goldmann applanation tonometry. RESULTS: Mean corneal hysteresis of 12.5 mm Hg was recorded in 81 [corrected] normal eyes of 42 children. It was markedly lower (mean 6.3 mm Hg) in 11 eyes of eight children with congenital glaucoma. No correlation was found between age and corneal hysteresis (r = -0.08). IOPg did not differ significantly from Goldmann applanation tonometry (P = .27). IOPcc was statistically significantly greater than IOPg (P = .014). RORA measurement was not possible in the presence of nystagmus but was possible with applanation tonometry. Cooperation with IOP measurement was much higher with RORA (89.8%) compared with applanation tonometry (78.7%). CONCLUSIONS: Corneal hysteresis in children is similar to that reported in adults. No correlation was found with age. In the presence of nystagmus, IOP measurement was possible with Goldmann applanation tonometry but not RORA. Cooperation with IOP measurement was better with RORA than with Goldmann applanation tonometry.

Adolescent↗

PubMed2006

Higher-order aberrations in children.

PURPOSE: To quantify and characterize higher order aberrations in children and to investigate the influence of refractive error and cycloplegia. DESIGN: Observational cross-sectional study. METHODS: setting: Clinical practice. patients: One hundred sixty-two eyes of 82 children were examined. The mean age of the children was 6.7 years (range, 4 to 14 years), and the mean manifest refractive spherical equivalent was 2.39 +/- 3.35 diopters (range, -8.98 to +8.45 diopters). Aberrometry was performed with a wavefront analyzer (after cycloplegia and mydriasis with cyclopentolate 1%). Aberrometry was also conducted on a subgroup of 52 eyes of 27 children, both before and 30 minutes after the instillation of cyclopentolate 1% to investigate the effect of paralysis of accommodation. RESULTS: Mean root mean square values of total-, third-, fourth-, and fifth-order aberrations were 0.37 +/- 0.13 microm, 0.23 +/- 0.12 microm, 0.16 +/- 0.11 microm, and 0.08 +/- 0.12 microm, respectively. Mean root mean square values of total coma (Z(3)(-1), Z(3)(1), Z(5)(-1), Z(5)(1)) and total trefoil (Z(3)(-3), Z(3)(3), Z(5)(-3), Z(5)(3)) were 0.27 +/- 0.31 microm and 0.21 +/- 0.29 microm, respectively. Myopes had statistically significant greater levels of total (P = .005) and fourth order (P = .002) aberrations and Zernicke terms (Z(3)(-3), Z(3)(-1), Z(3)(3), Z(4)(-4), and Z(4)(2)) compared with hyperopes. Cycloplegia had minimal influence on higher-order aberrations. CONCLUSION: Significant levels of higher-order aberrations were found in these children. They were influenced by refractive error, because myopes had significantly greater levels compared with hyperopes. Paralysis of accommodation with cyclopentolate appeared to have little effect on higher-order aberrations.

Accommodation, Ocular↗

PubMed2006

Stereopsis in refractive surgery.

PURPOSE: To examine stereopsis in myopic refractive surgery patients undergoing sequential bilateral and unilateral treatment. DESIGN: Prospective, observational, cohort study. METHODS SETTING: Clinical practice. PATIENTS: Eighty-three patients were studied; 55 had sequential bilateral and 28 had unilateral treatment. Mean age was 32 years. Stereopsis was measured using a multitarget red-green anaglyph stereo vision test. Only patients with fine preoperative stereopsis were included in the study. Repeat measurements were taken one week laser-assisted in situ keratomileusis (LASIK) or three weeks laser epithelial keratomileusis (LASEK) after treatment of one eye in all patients. Further measurements were taken at six and 12 weeks in unilaterally treated patients and after treatment of the fellow eye in bilaterally treated patients. RESULTS: A total of 38.6% of patients retained fine stereopsis (28 to 41 seconds of arc) over a range of anisometropia from 0.625 to 4.375. Moderate stereopsis (66 to 526 seconds of arc) was recorded 28.9% in the presence of 1.375 to 5.525 diopters of anisometropia. Poor/absent stereopsis (< or =2000 seconds of arc) was found in 32.5% in the presence of 2.1 to 8.0 diopters of anisometropia. A strong correlation was found between stereopsis and anisometropia, but interpatient variability was found. Uncorrected visual acuity (UCVA) in the untreated eye of > or =20/200 was associated with retention of fine stereopsis. Unilaterally treated patients showed improvement in stereopsis at six weeks after surgery. Sequential bilateral treatment had no deleterious effect on stereopsis. CONCLUSIONS: Loss of stereopsis was strongly correlated with anisometropia. UCVA in the untreated eye was a good indicator of postoperative stereopsis. Stereopsis improved during the postoperative adaptation period in unilateral treatments. Bilateral sequential treatment has no long-term effect on stereopsis.

Adult↗

PubMed2006

Paediatric aphakic glaucoma.

CONTEXT: Aphakic glaucoma is a serious, sight-threatening complication in children who remain aphakic following congenital cataract surgery. The reported incidence varies from 15% to 45% and it has a higher incidence in small eyes and in babies who undergo surgery before 4 weeks of age. Most cases take the form of open-angle glaucoma. Despite careful monitoring, diagnostic difficulties in children may lead to delayed treatment. Aphakic children require ongoing monitoring, including examinations carried out under general anaesthesia. MANAGEMENT: Contrary to earlier optimism, it is unlikely, according to current clinical information, that intraocular lenses provide protection against the development of glaucoma. It is likely that the lower incidence of glaucoma in pseudophakic eyes results from selection bias for lens insertion. Both medical and surgical treatments have a role in glaucoma management. Trabeculectomy with mitomycin C or Seton implantation (glaucoma drainage device) form the mainstay of surgical treatment. The success rate with Seton implants is better in the short term and more promising in the longer term than that of trabeculectomy. Cyclodestructive procedures play a role in refractory glaucoma. Success rates for surgery range from 14% to 44% and many children require additional medical treatment. Children with aphakic glaucoma need lifelong care. Despite our best efforts, many have poor vision, poor glaucoma control and ultimately become blind.

Aphakia, Postcataract↗

PubMed2005

Central corneal thickness and corneal diameter in premature infants.

BACKGROUND: Central corneal thickness is significantly greater in full-term infants than in adults. Very little is known about corneal thickness in premature infants. METHODS: Measurements of central corneal thickness and horizontal corneal diameter were carried out in 35 premature babies (70 eyes) undergoing screening for retinopathy of prematurity. Initial measurements were taken at approximately 31 weeks gestational age and at intervals until term was reached. RESULTS: Babies born at approximately 31 weeks have very thick corneas which show a progressive and statistically significant decrease to term. Conversely, horizontal corneal diameter shows a progressive significant increase to term. A very strong inverse correlation was found between these two parameters. CONCLUSION: We demonstrate that premature infants have thick corneas and small corneal diameters. Central corneal thickness decreases dramatically from approximately 31 weeks to term and is mirrored by a significant increase in corneal diameter.

Birth Weight↗

PubMedDate not supplied

Pediatric refractive surgery.

Refractive surgery in children is controversial; it is mainly performed when conventional treatment has failed. The primary indications are anisometropic amblyopia and bilateral high myopia. The major areas of concern are unstable refraction due to ongoing growth of the eye, and long-term implications. The most popular procedures are photorefractive keratectomy or laser-assisted subepithelial keratomileusis followed by laser-assisted in situ keratomileusis. There are technical difficulties involved in performing these procedures because of smaller palpebral apertures and the need for general anesthesia in younger children. Reports of minimal haze and regression in children who have undergone photorefractive keratectomy for high myopia are of interest, as this is contrary to what occurs in adults. Additional study may result in better long-term data and further indications for refractive surgery in children.

Child↗