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PubMed2003

Update on nonexcimer laser refractive surgery technique: conductive keratoplasty.

Excimer laser-based refractive surgery techniques have been the most popular forms to correct myopia, hyperopia, and astigmatism. However, development of non-excimer based refractive surgery such as thermal techniques provides a viable alternative to laser vision correction. Earlier forms of thermal techniques showed a lack of predictability and stability, resulting in the abandonment of the further development of these techniques. Recently, conductive keratoplasty, a laserless, radiofrequency-based technique, has been approved by the FDA for the correction of low to moderate hyperopia. Preliminary data showed that conductive keratoplasty seems to be safe, effective, and showed good refractive stability. This review will discuss recent studies on conductive keratoplasty technique in terms of its efficacy, safety, refractive predictability, and stability.

Astigmatism↗
PubMed2005

Stapes ankylosis in a family with a novel NOG mutation: otologic features of the facioaudiosymphalangism syndrome.

OBJECTIVE: To report the phenotype-genotype correlation in a Belgian family that was ascertained to have a novel missense mutation in the NOG gene mapping to chromosome 17q22. STUDY DESIGN: To describe the phenotype, a retrospective case study was performed based on the otologic, audiologic, ophthalmologic, and radiologic data of the mutation carriers of the NOG gene. SETTING: Tertiary referral center. PATIENTS: All members of a Belgian kindred who carried the novel missense mutation in the NOG gene (NOG, Trp205Cys [W205C]; 1426G>C). INTERVENTIONS: Diagnostic otologic and ophthalmologic examination, audiometric analysis, and radiologic imaging. MAIN OUTCOME MEASURES: Phenotype-genotype correlations. RESULTS: All five mutation carriers had a typical facies. Bilateral proximal symphalangism and hyperopia were present in 80%. Five of 10 ears also had progressive early-onset conductive hearing loss caused by stapes ankylosis. CONCLUSIONS: So far, 14 independent NOG mutations have been identified. The autosomal dominant disorder described in the present family was caused by a novel NOG missense mutation (NOG, Trp205Cys [W205C]; 1426G>C). The phenotype correlated well with the facioaudiosymphalangism syndrome. The mutation carriers demonstrated progressive multiple joint fusions, hyperopia, early-onset conductive deafness, and a typical facies.

Abnormalities, Multiple↗
PubMed2005

Ametropia and ocular biometry in a U.K. university student population.

PURPOSE: The prevalence of myopia is known to vary with age, ethnicity, level of education, and socioeconomic status, with a high prevalence reported in university students and in people from East Asian countries. This study determines the prevalence of ametropia in a mixed ethnicity U.K. university student population and compares associated ocular biometric measures. METHODS: Refractive error and related ocular component data were collected on 373 first-year U.K. undergraduate students (mean age = 19.55 years +/- 2.99, range = 17-30 years) at the start of the academic year at Aston University, Birmingham, and the University of Bradford, West Yorkshire. The ethnic variation of the students was as follows: white 38.9%, British Asian 58.2%, Chinese 2.1%, and black 0.8%. Noncycloplegic refractive error was measured with an infrared open-field autorefractor, the Shin-Nippon NVision-K 5001 (Shin Nippon, Ryusyo Industrial Co. Ltd, Osaka, Japan). Myopia was defined as a mean spherical equivalent (MSE) less than or equal to -0.50 D. Hyperopia was defined as an MSE greater than or equal to +0.50 D. Axial length, corneal curvature, and anterior chamber depth were measured using the Zeiss IOLMaster (Carl Zeiss, Jena, GmBH). RESULTS: The analysis was carried out only for white and British Asian groups. The overall distribution of refractive error exhibited leptokurtosis, and prevalence levels were similar for white and British Asian (the predominant ethnic group) students across each ametropic group: myopia (50% vs. 53.4%), hyperopia (18.8% vs. 17.3%), and emmetropia (31.2% vs. 29.3%). There were no significant differences in the distribution of ametropia and biometric components between white and British Asian samples. CONCLUSION: The absence of a significant difference in refractive error and ocular components between white and British Asian students exposed to the same educational system is of interest. However, it is clear that a further study incorporating formal epidemiologic methods of analysis is required to address adequately the recent proposal that juvenile myopia develops principally from "myopiagenic" environments and is relatively independent of ethnicity.

Adolescent↗
PubMed2002

Dynamic impedance measurements during radio-frequency heating of cornea.

Hyperopia affects approximately 25% of the population. The aim of different heating modalities for the treatment of hyperopia is to steepen the central curvature of the cornea. Conductive keratoplasty (CK) involves the placement of radio-frequency (RF) lesions around a 7-mm-diameter ring concentric with the pupil of the eye. Dynamics of lesion formation during CK depend on corneal electrical impedance, which is expected to change during each 600-ms-long macropulse. The purpose of this study was to measure impedance dynamics during CK. RF lesions were made in in vitro porcine eyes at different power settings. Voltage and current measurements were acquired using a high-speed computer-based data acquisition system. Root-mean-square voltages (VRMS) and curre (IRMS) were calculated for each micropulse, and impedance was determined by calculating the quotient VRMS/IRMS. Initial corneal impedance in vitro was approximately 2000 ohms. During the macropulse, impedance decreased initially due to increased mobility of conductive ions. At higher power settings (e.g., > 70%, or maximum peak-to-peak voltage of 233 V), impedance increased after the initial decrease, indicative of local water vaporization and/or tissue coagulation. Preliminary impedance data obtained for in vivo porcine eyes were similar in magnitude to the in vitro values.

Animals↗
PubMed2005

Persistent posterior globe flattening after orbital cavernous haemangioma excision.

A 54-year-old man presented with left intraconal cavernous haemangioma resulting in globe compression and hyperopia. The tumour was excised completely via lateral orbitotomy approach. Complete excision of tumour did not result in resolution of globe flattening and hyperopia after 21 months. Persistent globe flattening despite removal of a longstanding orbital tumour may be caused by remodelling of the sclera from long-term compression.

Choroid Diseases↗
PubMed1983

Photorefraction: A useful tool to detect refraction errors.

A simple photorefraction method using simultaneous photography of corneal and fundus reflexes have been used to screen 239 children aged 10 to 15 months for significant refraction errors. The photorefraction results were calibrated to those of cycloplegic retinoscopy. A good agreement was found between the 2 sets of values. The frequency distribution of refraction errors were similar to those presented by Ingram (1979). The aim to detect hyperopia greater than or equal to +2 or myopia greater than or equal to -4 diopters together with significant anisometropia or astigmatism was fulfilled with high reliability. Low degrees of hyperopia, myopia and astigmatism might be missed. Photorefraction therefore is considered to be a reliable, simple and cheap tool with high sensitivity and specificity in screening small children for significant refraction errors.

Astigmatism↗
PubMed2005

Retinal dysfunction and refractive errors: an electrophysiological study of children.

AIMS: To evaluate the relation between refractive error and electrophysiological retinal abnormalities in children referred for investigation of reduced vision. METHODS: The study group comprised 123 consecutive patients referred over a 14 month period from the paediatric service of Moorfields Eye Hospital for electrophysiological investigation of reduced vision. Subjects were divided into five refractive categories according to their spectacle correction: high myopia (< or = -6D), low myopia (>-6D and < or = -0.75D), emmetropia (>-0.75 and <1.5D), low hyperopia (> or = 1.5 and <6D), and high hyperopia (> or = 6D). Patients with a specific diagnosis at the time of electrophysiological testing were excluded. Only the first member of any one family was included if more than one sibling had been tested. All tests were performed to incorporate ISCEV standards, using gold foil corneal electrodes where possible. In younger patients skin electrodes and an abbreviated protocol were employed. RESULTS: The mean age of patients was 7.1 years with an overall incidence of abnormal electrophysiological findings of 29.3%. The incidence of abnormality was higher in high ametropes (13/25, 52%) compared to the other groups (23/98, 23.5%). This difference was statistically significant (chi2 test, p = 0.005). There was also a significant association between high astigmatism (>1.5D) and ERG abnormalities (18/35 with high astigmatism v 20/88 without, chi2 test, p = 0.002). There was no significant variation in frequency of abnormalities between low myopes, emmetropes, and low hyperopes. The rate of abnormalities was very similar in both high myopes (8/15) and high hyperopes (5/10). CONCLUSIONS: High ametropia and astigmatism in children being investigated for poor vision are associated with a higher rate of retinal electrophysiological abnormalities. An increased rate of refractive errors in the presence of retinal pathology is consistent with the hypothesis that the retina is involved in the process of emmetropisation. Electrophysiological testing should be considered in cases of high ametropia in childhood to rule out associated retinal pathology.

Adolescent↗
PubMed2000

Outcome in refractive accommodative esotropia.

AIM: To examine outcome among children with refractive accommodative esotropia. METHODS: Children with accommodative esotropia associated with hyperopia were included in the study. The features studied were ocular alignment, amblyopia, and the response to treatment, binocular single vision, requirement for surgery, and the change in refraction with age. RESULTS: 103 children with refractive accommodative esotropia were identified. Mean follow up was 4.5 years (range 2-9.5 years). 41 children (39.8%) were fully accommodative (no manifest deviation with full hyperopic correction). The remaining 62 children (60.2%) were partially accommodative. At presentation 61.2% of children were amblyopic in one eye decreasing to 15.5% at the most recent examination. Stereopsis was demonstrated in 89.3% of children at the most recent examination. Mean cycloplegic refraction (dioptres, spherical equivalent) remained stable throughout the follow up period. The mean change in refraction per year was 0.005 dioptres (D) in right eyes (95% CL -0. 0098 to 0.02) and 0.001 D in left eyes (95% CL -0.018 to 0.021). No patients were able to discard their glasses and maintain alignment. CONCLUSIONS: Most children with refractive accommodative esotropia have an excellent outcome in terms of visual acuity and binocular single vision. Current management strategies for this condition result in a marked reduction in the prevalence of amblyopia compared with the prevalence at presentation. The degree of hyperopia, however, remains unchanged with poor prospects for discontinuing glasses wear. The possibility that long term full time glasses wear impedes emmetropisation must be considered. It is also conceivable, however, that these children may behave differently with normal and be predestined to remain hyperopic.

Amblyopia↗
PubMed2002

Development of myopia as a hazard for workers in pneumatic caissons.

BACKGROUND/AIM: Pneumatic caisson engineering has been developed for large civil engineering constructions. Because of complaints of blurred vision by personnel working in pneumatic caissons, the development of myopia was suspected. The aim of this study was to determine the cause of the blurred vision and the mechanism underlying the changes. METHODS: 12 caisson workers underwent a complete ophthalmological examination after completing up to 11 weeks of work (4 days/week) in a pneumatic caisson. Six months later, nine of the workers were examined again. RESULTS: Nine subjects were myopic at the initial examination, and seven of these were considered to have developed the myopia after starting to work in the pneumatic caisson. Six months after completion of the work, the mean refractive change was significantly towards hyperopia. CONCLUSIONS: The blurred vision in pneumatic caisson workers was in all likelihood due to the development of myopia. The refractive shift towards hyperopia after completion of work in the pneumatic caisson supports this and demonstrates that the changes were temporary. The myopia is similar to the myopia seen in patients treated by hyperbaric oxygen. Careful monitoring of the refraction of caisson workers should be performed for industrial health control.

Adult↗
PubMed2005

Comparison of ocular component growth curves among refractive error groups in children.

PURPOSE: To compare ocular component growth curves among four refractive error groups in children. methods Cycloplegic refractive error was categorized into four groups: persistent emmetropia between -0.25 and +1.00 D (exclusive) in both the vertical and horizontal meridians on all study visits (n = 194); myopia of at least -0.75 D in both meridians on at least one visit (n = 247); persistent hyperopia of at least +1.00 D in both meridians on all visits (n = 43); and emmetropizing hyperopia of at least +1.00 D in both meridians on at least the first but not at all visits (n = 253). Subjects were seen for three visits or more between the ages of 6 and 14 years. Growth curves were modeled for the persistent emmetropes to describe the relation between age and the ocular components and were applied to the other three refractive error groups to determine significant differences. results At baseline, eyes of myopes and persistent emmetropes differed in vitreous chamber depth, anterior chamber depth, axial length, and corneal power and produced growth curves that showed differences in the same ocular components. Persistent hyperopes were significantly different from persistent emmetropes in most components at baseline, whereas growth curve shapes were not significantly different, with the exception of anterior chamber depth (slower growth in persistent hyperopes compared with emmetropes) and axial length (lesser annual growth per year in persistent hyperopes compared with emmetropes). The growth curve shape for corneal power was different between the emmetropizing hyperopes and persistent emmetropes (increasing corneal power compared with decreasing power in emmetropes). conclusions Comparisons of growth curves between persistent emmetropes and three other refractive error groups showed that there are many similarities in the growth patterns for both the emmetropizing and persistent hyperopes, whereas the differences in growth lie mainly between the emmetropes and myopes.

Adolescent↗
PubMed1976

Relationship of serum glucose concentration to changes in refraction.

The effect of chronic changes in serum glucose concentration on refraction was studied by increasing the dose of insulin or chlorpropamide in 10 diabetic patients who initially had relatively high glucose concentrations. In every case when serum glucose concentration was reduced the vision became less myopic or more hyperopic. To assess acute changes. 10 diabetics (including four with aphakic eyes) were given an intravenous injection of glucose. In patients with intact lenses the vision became more myopic or less hyperopic following the administration of glucose, but in the aphakic eyes hyperopia increased. It is concluded from both the acute and chronic studies that higher levels of serum glucose concentration produce myopia and lower levels produce hyperopia. Furthermore, these changes are related to changes in the optical properties of the crystallin lens.

Blood Glucose↗
PubMedDate not supplied

Bilateral hypermetropic amblyopia.

A retrospective analysis was performed on the records of 184 children who had hyperopia of at least 4.0 diopters in each eye to see if bilateral amblyopia was more than just a rare occurrence and to evaluate how well it responded to treatment. Twelve patients were found to have bilateral amblyopia of 20/50 or worse. The mean age at diagnosis was four and a half years (two and a half to six and a half) and mean follow-up was 22 months (five months to seven years, four months). Ten of 12 patients showed improvement of vision to 20/40 or better in both eyes. Treatment consisted of full cycloplegic correction in all cases. Six patients had accommodative esotropia but this did not account for the bilateral nature of the amblyopia. Bilateral amblyopia should be considered in patients with large amounts of hyperopia. It responds well to treatment with standard amblyopia therapy.

Accommodation, Ocular↗
PubMedDate not supplied

Hexagonal keratotomy--should we still be trying?

BACKGROUND: I present my limited but positive experience with hexagonal keratotomy for hyperopia. METHODS: Eighteen consecutive eyes of 12 patients underwent hexagonal keratotomy during 1993. In addition to the primary procedures, 14 enhancements were required in seven eyes for both astigmatism and undercorrection. Surgical planning was based on refractive data only. All surgeries were performed by one surgeon using the open hexagonal keratotomy pattern. RESULTS: The patients' average age was 56 years (range, 38 to 67 years). Fourteen eyes were corrected for emmetropia. They had an average preoperative refraction of +2.22 +/- 0.64 diopters (D) and an average postoperative refraction of +0.11 +/- 0.49 D. Four eyes were corrected for near vision (-2.00 D). They had an average preoperative refraction of -0.53 +/- 0.83 D, and postoperatively their average refraction was -1.78 +/- 0.50 D. All four could read J1 without correction postoperatively. No eye lost more than one line of spectacle-corrected visual acuity; none had a major sight-threatening complication. CONCLUSIONS: Hexagonal keratotomy can correct 3.50 D or less of hyperopia. Conservative surgery with one major reoperation procedure is suggested. Because of the highly variable results noted in the literature and several reports of significant complications, I no longer perform or recommend hexagonal keratotomy.

Adult↗
PubMedDate not supplied

The suction bridge for radial keratotomy may avoid late hyperopic shift.

BACKGROUND: Radial keratotomy may induce late hyperopic shift. We present data on 140 consecutive eyes with a follow-up of up to 3 years that underwent radial keratotomy with the RK suction bridge. METHODS: We conducted a retrospective study of 140 consecutive eyes that had radial keratotomy between 1987 and 1994. Mean preoperative spherical equivalent was -5.21 D (range -2.00 to -9.75 D). All operations were performed by one surgeon (JHK) with the RK suction bridge. A suction ring maintaining physiological intraocular pressure immobilized the eye and left a peripheral rim of uncut cornea. The ring incorporated an eccentric bridge that guided the radial keratotomy knife. The knife setting was 90% of the central corneal thickness, measured by pachymetry. Spherical equivalent refraction and spectacle corrected visual acuity were measured at 1 week, 1, 3, 6 months, 1 year, and 3 years after radial keratotomy. RESULTS: The mean preoperative spherical equivalent refraction of -5.21 D dropped to -0.43 D at 1 week (n = 136), -0.71D at 1 month (n = 120), -0.85 D at 3 months (n = 95), -0.74 D at 6 months (n = 73), -0.77 D at 12 months (n = 79), and -0.85 D at 3 years (n = 67). Compared to 1 month spherical equivalent, at 3 years three eyes (4.4%) had moved > = or 1.00 D toward hyperopia. One eye (1.4%) shifted by 1.25 D. Paired t-tests of mean spherical equivalent refraction did not reveal significant shifts toward hyperopia. Mean preoperative spectacle-corrected visual acuity was slightly diminished at 1 week and was equal or better thereafter. CONCLUSIONS: Our 3-year data suggest that a late hyperopic shift following radial keratotomy may be prevented if an intact peripheral rim is maintained and cutting depth does not exceed 90% of the lowest corneal thickness.

Adolescent↗
PubMedDate not supplied

Laser in situ keratomileusis enhancement after radial keratotomy.

PURPOSE: To present results of laser in situ keratomileusis (LASIK) enhancement after radial keratotomy (RK). METHODS: Sixteen eyes of 10 patients were treated with LASIK for residual myopia and hyperopia after RK. Mean preoperative spherical equivalent refraction was -3.14+/-3.04 D (range, -6.675 to +6.00 D). Best spectacle-corrected visual acuity was 20/20 in 9 eyes, 20/25 in 6 eyes, and 20/30 in 1 eye. Uncorrected visual acuity was better than 20/40 in only 2 eyes. Patients were followed at 1 day, 1 week, 1, 3, and 6 months, and 1 year. Mean follow-up was 8.3 months (range, 1 to 17 mo). RESULTS: All eyes received one LASIK enhancement. Mean final spherical equivalent refraction was +0.16+/-0.68 D (range, -1.00 to +1.75 D). No eyes experienced any visual loss. Five eyes gained 1 line of best spectacle-corrected visual acuity. Uncorrected visual acuity was 20/20 in 9 eyes, 20/25 in 6 eyes, and 20/30 in 1 eye. Two eyes of one patient had the previous RK incisions open. CONCLUSION: LASIK was an effective treatment for correction of residual myopia and hyperopia after RK.

Adult↗
PubMedDate not supplied

A retrospective study of laser in situ keratomileusis after radial keratotomy.

PURPOSE: This is a retrospective study designed to present results of laser in situ keratomileusis (LASIK) after radial keratotomy (RK). METHODS: Eighty eyes of 56 patients underwent LASIK for residual myopia, astigmatism, and hyperopia after RK. Absolute mean preoperative spherical equivalent refraction was 2.36 +/- 1.17 D. Best spectacle-corrected visual acuity (BSCVA) was 20/20 in 56% of eyes, 20/25 in 25%, 20/30 in 13%, 20/40 in 5%, and 20/60 in 1%. Uncorrected visual acuity was better than 20/40 in four eyes. Follow-up ranged from a minimum of 1 day after surgery to a maximum of 2 years, with an average of 6 months. RESULTS: Mean final absolute spherical equivalent refraction was 0.62 +/- 0.611 D. Six eyes experienced a loss of BSCVA of one line, one eye lost two lines, and one lost more than two lines. Three eyes had one line of improvement and one eye had two lines of improvement. Uncorrected visual acuity was 20/20 in 21 eyes, 20/25 in 20 eyes, and 20/30 in 19 eyes. There was stromal opacity in two eyes, epithelial defects in two eyes, and epithelial ingrowth in four eyes. CONCLUSION: LASIK may be an effective treatment for myopia, astigmatism, and hyperopia in patients with residual refractive error after RK. Extreme caution should be exercised due to the complexity of this group of patients.

Astigmatism↗
PubMedDate not supplied

Laser intrastromal keratoplasty--case report.

PURPOSE: To evaluate the feasibility of correcting high hyperopia by means of intrastromal implantation of a laser shaped corneal lenticule prepared from a human donor eye. METHODS: A female patient with high hyperopia and irregular astigmatism resulting from multiple laser in situ keratomileusis procedures and lamellar keratoplasty underwent laser intrastromal keratoplasty. Her preoperative uncorrected visual acuity (UCVA) was 20/300 and best spectacle-corrected visual acuity (BSCVA) was 20/100 with a refraction of +8.00 -1.00 x 130 degrees. Corneal topography showed a highly irregular corneal surface. Central corneal thickness was 398 microm. Lenticule preparation included mechanical de-epithelialization of a human donor eye, keratectomy with a microkeratome, user-designed software combining a photorefractive keratectomy (PRK) treatment for +8.00 D sphere, an ablation zone of 7.0 mm, and a circumferential cut (internal diameter of 6.5 mm) for tissue ablation. Implantation involved re-lifting the flap, positioning the lenticule onto the corneal bed, and repositioning of the flap. RESULTS: The operation was uneventful as was the early postoperative follow-up. BSCVA improved to 20/50 with +1.00 -2.25 x 120 degrees at 2 months postoperatively. Corneal topography showed a more regular cornea with increased curvature in all meridians. Central corneal thickness increased to 600 microm. CONCLUSION: Laser intrastroma keratoplasty may be an option for correcting high hyperopa and irregular astigmatism in eyes with a thin corneal bed.

Adult↗
PubMedDate not supplied

Videokeratography in conductive keratoplasty.

PURPOSE: We used EyeSys videokeratography to evaluate corneal shape changes induced by conductive keratoplasty, a procedure that utilizes radio frequency energy to alter corneal shape to correct hyperopia. METHODS: Follow-up data were available for 19 eyes (out of 24 eyes of 13 patients). Preoperative spherical hyperopia ranged from +0.75 to +3.25 D with astigmatism <0.75 D. Manifest refractive spherical equivalent refraction (MRSE), uncorrected visual acuity (UCVA), best spectacle-corrected visual acuity (BSCVA), topographical parameter predicted corneal acuity (PCA), corneal uniformity index (CU Index), regular astigmatism, total astigmatism, average simulated keratometry (Avg Sim K), effective refractive power, and asphericity were measured preoperatively and at 6 and 12 months postoperatively. RESULTS: Twelve months postoperatively, mean PCA, CU Index, and BSCVA were maintained at preoperative levels. Mean UCVA (LogMAR) improved from 0.53+/-0.21 to 0.10+/-0.19 (P<.05) with a mean MRSE change from +1.62+/-0.76 D to -0.06+/-0.84 D (P<.05) from preoperative to 12 months postoperative. Mean asphericity increased +0.044+/-0.24 D (P>.05), mean Avg Sim K increased 1.88+/-0.72 D (P<.05), mean effective refractive power increased 1.71+/-0.79 D (P<.05), mean cylinder (cycloplegic refraction) increased 0.19+/-0.36 D (P<.05), mean regular astigmatism increased 0.25+/-0.49 D (P>.05), and mean irregular astigmatism decreased 0.01+/-0.13 D (P>.05) from preoperative to 12 months after conductive keratoplasty. CONCLUSIONS: Avg Sim K and effective refractive power changes support the refractive results; 12-month postoperative maintenance of BSCVA, PCA, and CU Index suggest the procedure is safe. Conductive keratoplasty induced a slight regular astigmatism in some eyes, which decreased with time. The increase in mean corneal asphericity indicated possible induction of central and peripheral cornea changes.

Adult↗