Refractive outcome in eyes with retinopathy of prematurity treated with cryotherapy or diode laser: 3 year follow up

AIMS: To compare the refractive error 1 to 3 years after cryotherapy or diode laser treatment for threshold retinopathy of prematurity. METHODS: Twenty six infants treated with diode laser and 17 infants treated with cryotherapy underwent cycloplegic refraction during follow up. RESULTS: After 3 years of follow up, 94.1% of patients had myopia (right eye if bilateral) following cryotherapy and 45.5% of patients had myopia following diode laser treatment. The difference between the two proportions was 48.7% (95% confidence interval 17.8 to 80.1, p = 0.004). In the cryotherapy group 55% of patients were highly myopic (> -6.00 dioptres) while in the laser group there were no high myopes. CONCLUSIONS: In the diode laser group there were significantly fewer myopes than in the cryotherapy group up to 3 years after the procedure. There was no trend towards increasing myopia in the laser treated group and the refraction in these eyes stabilised after 1 year. In the cryotherapy group there was a significant increase in the degree of myopia between year 1 and year 3 of follow up (p = 0.02). Diode laser treatment is thought to be as effective as cryotherapy, and has the added benefit of reducing myopia, in the treatment of ROP.     

The susceptible period for deprivation-induced myopia in tree shrew

To examine the susceptible period for deprivation-induced myopia, six groups of tree shrew pups (Tupaia glis belangeri) were monocularly deprived for 12 days with an opaque occluder starting 7, 15, 21, 33, 48, or 63 days after natural eyelid opening. Compared to the untreated fellow control eye, significant myopia and vitreous chamber elongation were produced by the deprivation in all six groups. The effect was greater in the middle three groups in comparison with the youngest and the two oldest groups and the amount of induced myopia and axial elongation was not proportional to the normal rate of axial growth. The peak period of susceptibility was between approximately 15 and 45 days after eye opening during the juvenile, slow-elongation phase of ocular development when the eye is within 7% of its adult axial length. Significant myopia and axial elongation were also induced in adult animals by 70 days of monocular deprivation. To examine recovery from deprivation-induced myopia, the occluder was removed at the end of the 12 day deprivation period. After an additional 48 days of binocular visual experience, no significant myopia was present in the previously deprived eyes in any experimental group. During the recovery period, the elongation rate of the previously deprived eyes was reduced in comparison with the control eyes while normal corneal flattening and lens development continued, thus reducing the myopia. No difference in corneal curvature, relative to the untreated control eyes, was found after deprivation or after the recovery period. Data are presented which suggests that changes in the thickness of the choroid may occur in this mammal during deprivation and recovery that are in the same direction, but of smaller magnitude, than those reported in the chicken. The results of this study provide evidence that visually guided emmetropization occurs in this mammalian species during a period of ocular development analogous to the juvenile period in humans.     

The effects of choroidal or ciliary nerve transection on myopic eye growth induced by goggles

PURPOSE: To determine the role of the choroidal and ciliary nerves and the functions they control, choroidal blood flow (CBF) and accommodation-pupil diameter, respectively, in myopia induced by form-vision deprivation. METHODS: Three groups of chicks were studied: chicks with choroidal nerves cut in the right eye, chicks with ciliary nerves cut in the right eye, and sham control chicks that received the same surgical preparation but no nerve cuts. A plastic, dome-shaped goggle was glued over the right eye of birds in all three groups after orbital surgery, and, 2 weeks later, CBF was measured using laser Doppler flowmetry. Refractive status was then measured using streak retinoscopy, and axial, nasotemporal, and dorsoventral lengths were measured using vernier calipers after enucleation. The eyes were also weighed. RESULTS: In the sham control birds, considerable ocular enlargement in all dimensions and a high degree of myopia (-14.68 diopters) was observed in the goggled eye, and CBF in the goggled eye was 66% of that in the nongoggled eye. In birds with choroidal nerve cuts, the degree of enlargement of the goggled eye was less in all dimensions, and the myopia in the goggled eye (-4.74 D) was attenuated compared to that observed in the sham controls. CBF in the goggled eye was 21% of that in nongoggled eye. Finally, in the birds with ciliary nerve cuts, nasotemporal and dorsoventral enlargement of the goggled eye were similar to that in the shams, but the axial elongation and the degree of myopia (-9.57 D) were less than observed in sham control eyes. As in the shams, CBF in the goggled eye was reduced to 59% of that in the nongoggled eye. CONCLUSIONS: These results show that although elimination of accommodation and severe reductions in CBF do affect eye growth (the latter more so), they do not prevent form-vision deprivation-induced myopia. Thus, either the mechanism of visual deprivation-induced myopia is different from that in idiopathic human myopia, or CBF levels and accommodation do not play a major role in either.     

Application of the dispersion model for description of the outflow dilution profiles of noneliminated reference indicators in rat liver perfusion studies

Recent investigations have raised the possibility that ocular diurnal rhythms might be involved in the regulation of eye growth. Specifically, the chick eye elongates with a daily rhythm, said to be absent in form-deprived eyes. The present study asks: (1) Which components of the eye have daily rhythms-only the overall eye size, or also choroidal thickness or anterior chamber depth? (2) Does the phase or amplitude of these rhythms differ in eyes growing either faster than normal (form-deprived eyes) or slower than normal (eyes recovering from form-deprivation myopia)? Using high-frequency A-scan ultrasonography that allowed fine (8-20 micron) resolution of anterior chamber depth, vitreous chamber depth, choroidal thickness and axial length, we measured normal eyes, form-deprived eyes and eyes recovering from form-deprivation myopia at 6 hour intervals for 5 days and 4 nights. All eyes showed daily rhythms in axial elongation and choroidal thickness. In both normal and form-deprived eyes, the axial length was greatest in the afternoon when the choroid was thinnest, and hence, these rhythms were approximately in anti-phase to one another; in addition, there is some evidence that the axial length rhythm in form-deprived eyes is phase-advanced relative to that of their fellow control eyes. The amplitude of the rhythm in choroidal thickness in form-deprived eyes was significantly larger than in normal eyes. In recovering eyes in which elongation is slowed, the rhythm in axial length was significantly phase-delayed relative to normal eyes (peak at 8 pm) and the rhythm in choroidal thickness was phase-advanced (peak at 8 pm); thus in these eyes, the two rhythms are in phase. In these eyes, the choroids were thickening by approximately 100 micron/day. In all three groups, the rhythm in anterior chamber depth appears to differ in phase from the rhythm in axial length (and hence from the rhythm at the posterior wall of the eye). We propose that the phase relationship between these choroidal and eye length rhythms influence the rate of growth of the eye, and conclude that diurnal ocular rhythms may be important in eye growth regulation.     

Occurrence of changes in the eye in diabetic retinopathy with significant myopia

The optic disc and retinal neovascularization are less prominent and less frequent in myopic eyes in patients suffering from diabetes mellitus. The exact mechanisms of this phenomenon are not well known, but there is some evidence that there is a reduced blood flow in myopic eyes which is associated with less damaged microcirculation in eyes of patients with diabetes mellitus. The aim of our study was to evaluate the correlation between myopic refractive error and degree of diabetic retinopathy. We conducted a retrospective study in a group of randomized patients, divided into the following groups according to their refractive error: emmetropia (30 eyes), myopia simplex (30 eyes) and high myopia, over -6.5 dsph (21 eyes). Among patients with high myopia, seven had monocular myopia. All patients suffered from non insulin dependent diabetes mellitus for more than ten years, and their average age was 52.37-3.48 years. We did not observe patients with rubeosis iridis and neovascular glaucoma or patients with myopia less than -2.0 dsph. Our results indicated that there was no significant difference in the appearance of fundus between the studied groups. In all patients the incidence rate of non proliferative and proliferative diabetic retinopathy was the same as well as the absence of retinopathy (Fisher's test). The only exception were the patients with monocular myopia over -13.o dsph who had no signs of diabetic retinopathy in myopic eye, while the other, emmetropic eye, showed various stages of retinopathy, from severe non proliferative to proliferative. Some of the risk factors which influence the incidence rate of ocular complications in diabetic patients are well known, as are duration of diabetes mellitus, blood sugar level, blood pressure, ocular pressure and eye perfusion. On the other hand, it is also known that amblyopia, optic atrophy, low blood pressure in central retinal artery and retinitis pigmentosa are ocular conditions which are not associated with proliferative diabetic retinopathy. It was also noticed that complications of diabetes in high myopic eyes are less prominent than in emmetropic eyes. This finding is in harmony with our results. Sultanov et al. observed diabetic changes in the retina in 40.9% of myopic refraction patients, 65.2% of emmetropia cases and 70.4% of hypermetropia cases. The severity of involvement was less in myopia than in other types of refraction. In medium severe myopia, no proliferative diabetic retinopathy was observed, and in high myopia (10 eyes) no diabetic involvement of the fundus oculi was found. In anisometropia diabetic symptoms on the myopic side were either absent or poorly manifest. The possible cause of such findings could be the changes in retinal perfusion in myopic eyes and eyes in patients with diabetes mellitus. In 1973 a lower blood flow was detected in the retina and the choroid, proportionally to the degree of myopia. In 1982, Perkins indicated that the circulation time and pulsation rate in the central retinal artery in myopic eyes were reduced proportionally to the degree of myopia. In cases with early diabetic retinopathy Coscas detected a lesser blood flow in retinal veins. On the other hand, it has been found that high blood pressure increases the risk of diabetic retinopathy. These data suggest that the reduced blood flow in high myopia is a protective factor regarding the occurrence of complications in diabetes. Anisometropia and amblyopia in cases with monocular myopia, which presents a particular group in our study, could be factors which also prevent the occurrence of proliferative diabetic retinopathy. Instead of conclusion, we would like to point out that pathophysiologic mechanisms of these phenomena are not discussed enough. It is, nevertheless, important to appropriately examine the fundus in patients with high myopia and diabetes mellitus, because if the complications appear, they may be disastrous and must be treated immediately.     

Multizone photorefractive keratectomy for high and very high myopia: long-term results

PURPOSE: To compare 2 year results of multizone excimer laser photorefractive keratectomy (PRK) in eyes with myopia (spherical equivalent [SE]) from 6.00 to 10.00 diopters (D) with those in eyes with myopia from 10.25 to 25.75 D. SETTING: Wellington Hospital and Laser Vision Harley Street, London, England. METHODS: Of the 281 PRK cases with an SE of at least -6.00 D, 59 eyes had a minimum follow-up of 2 years. Twenty-six of these had an SE from -6.00 to -10.00 D and 33, from -10.25 to -25.75 D. The single-pass, multizone technique was used to create ablation zones at 5.0, 5.5, and 6.0 mm. Postoperatively, patients received a minimum of 4 weeks of fluorometholone 0.1%; those exhibiting regression after corticosteroids were discontinued were restarted on a tapering regimen. RESULTS: The refraction stabilized 3 months postoperatively in the -6.00 to -10.00 D group, and the final mean SE refraction was a small undercorrection. Two years postoperatively, 88.5% of eyes had a visual acuity of 20/40 or better, and 77.0% were within +/- 1.00 D of the intended correction. In eyes with myopia greater than 10.00 D, regression continued during the 2 years and refraction did not stabilize. Forty-two percent had an uncorrected acuity of 20/40 or better, and 48.0% were within +/- 1.00 D of the intended correction. The incidence and severity of haze were higher in the group with myopia greater than 10.00 D. The overall incidence of complications was low. CONCLUSION: Two years after multizone PRK, refractive and visual acuity results in eyes with myopia from 6.00 to 10.00 D were good. Results in eyes with myopia of more than 10.00 D were not satisfactory, and refraction had not stabilized.     

Biomechanical regularities in the distribution of tension in various topographic zones of the eyelids in children in health and myopia of different degree

The authors assessed the method for life-time study of the biomechanical characteristics of ocular tissues in 281 children (562 eyes) aged 7 to 14 years. The method for assessing the biomechanics of the eyelids is described. In detail. The rates of propagation of acoustic waves in normal tissue and in 1.0 to 6.0 diopters myopia are presented. A correlation has been revealed between the increase of the velocity of acoustic surface waves, propagating in the horizontal direction in the internal segment of the orbital area of the upper eyelids, and the value of clinical refraction in myopia. The authors consider clinical signs of myopia-screwing up one's eyes and a wider lid slit-from a biomechanical viewpoint.     

Application of Raney nickel to measure adducts of styrene oxide with hemoglobin and albumin

BACKGROUND: Although peripheral cryotherapy decreases the incidence of unfavorable anatomic outcomes in threshold retinopathy of prematurity (ROP), apnea, bradycardia, and lid edema can occur. Argon laser indirect ophthalmoscope photocoagulation has been used as an alternative to cryotherapy, with fewer adverse effects. Retinal lesions placed with diode lasers are deeper than similar argon laser lesions, and it is not known whether this difference could influence the response to ablative therapy. METHODS: Patients were enrolled under a prospective, randomized protocol. One eye of each patient with symmetric, threshold ROP was treated with an 814/815 nm diode laser, while the other eye was treated with cryotherapy. Patients with asymmetric diseases also were randomized for treatment in the threshold eye. RESULTS: Nineteen infants (33 eyes) were treated, ranging from 485 to 863 g birth weight (23 to 27 weeks gestational age); 18 patients (32 eyes) were followed for 3 months or longer. Four patients (8 eyes) had bilateral zone 1 disease. Postconceptional age was 36 to 45 weeks at the time of treatment. The diode laser treatment was better tolerated than cryotherapy, and the treatment apparatus was more easily transported. Apneic episodes requiring intubation resulted from two cryotherapy sessions but no diode laser sessions. Five cryotherapy-treated eyes required retreatment because of persistent disease with adjacent skip areas. In the group followed for 3 to 15 months, 1 cryotherapy-treated eye and 1 diode laser-treated eye progressed to stage 5 retinal detachment. CONCLUSION: Compared with cryotherapy, the diode laser was more convenient, technically easier to administer, and better tolerated by the patient. Although the number of patients was too small for meaningful statistical analysis of outcome, diode laser peripheral retinal ablation appeared to be as effective as cryotherapy for the treatment of threshold ROP.     

Cryotherapy for trichiasis in ocular cicatricial pemphigoid

Trichiasis is a common and potentially sight threatening complication of ocular cicatricial pemphigoid and is usually secondary to cicatricial entropion. This study aimed to assess the success and complications of eyelid cryotherapy for trichiasis in a group of patients with long term follow up. The case records of all patients with ocular cicatricial pemphigoid that attended the external disease clinic at Moorfields Eye Hospital from 1980 to 1992 were reviewed. Each eyelid was divided into three horizontal zones. Cryotherapy was delivered with an Amoilette cryoprobe for approximately 30 seconds. Failure of the cryotherapy was defined as a regrowth of the eyelashes within the treated zone that either required epilation for symptom control or caused keratopathy. Ninety two lid zones were treated, involving 25 lids of 12 patients. The cumulative chance of success decreased rapidly to 40% over the first year. Thereafter, the chance of success declined slowly to 34% at 4 years. Complications included lid notching (n = 2), tarsal atrophy (n = 1), altered lid contour (n = 1), and temporarily raised intraocular pressure (n = 1). All patients had quiescent disease at the time of the cryotherapy and no patients showed increased conjunctival disease activity after treatment. Six patients were taking systemic immunosuppression medication. When ocular cicatricial pemphigoid is quiescent, lid cryotherapy has an acceptable complication rate. The major reason for recurrence of the trichiasis was attributed to inadequate follicle freezing.     

Treatment of oesophageal carcinoma at a small rural hospital

OBJECTIVE: For the primary treatment of pseudophakic retinal detachment, vitrectomy could be preferred to episcleral buckle because it does not induce myopia, it clears opacities of the posterior capsule and/or of the vitreous and allows a good visualization of the fundus. This study was determined to compare the anatomic and functional results of vitrectomy and episcleral buckle. METHODS: from 1990 to 1995, 93 pseudophakic eyes were operated on for retinal detachment. 75 eyes were treated with episcleral buckle (group I) and 18 eyes were treated with vitrectomy (group II). In the latter group, 4 eyes had a giant tear, and 4 other eyes had a macular hole associated with high myopia. The anatomic and functional results were analyzed retrospectively. RESULTS: The retina was reattached with one operation in 67 eyes of group I (89%) and 16 of group II (89%). More than one month after the first operation, the retina redetached in 6 eyes of Group I (8%) and one eye of group II (6%). The causes of failure were a) new or missed retinal tears [Group I: 10 eyes (13%), group II: 3 eyes (17%)] and b) vitreoretinal proliferation (group I: 4 eyes, group II: 0). The number of subsequent reoperations for failures or recurrences was higher in group I than in group II. At the final examination, the retina was attached in 73 eyes of group I (97%) and in 18 eyes of group II (100%). The Kruskal-Wallis test did not detect any difference between the two groups concerning the pre- or postoperative visual acuities. CONCLUSION: Vitrectomy seems as effective as episcleral buckle for the treatment of pseudophakic retinal detachment and offers additional advantages.     

Fornix reconstruction in ocular pemphigoid with Goretex surgical membrane

After separation of symblepharons in ocular pemphigoid, transplantation of nasal or bucal mucosa is recommended to prevent recurrent lid fusion; however, it is not always successful. BACKGROUND: An 86-year-old patient was referred to our eye clinic because of trichiasis in ocular pemphigoid. In the right eye, the only functional eye, fusion of the lower lid and the globe was present. There was severe trichiasis with multiple lesions of the cornea and beginning neovascularization. The left eye showed complete fusion of the lid fissure and neovascularization of the cornea. To prevent the right eye from suffering the fate of the left, we tried to find a simple surgical method that could easily be performed on the multimorbid patient. METHOD: Under parabulbar anesthesia we separated the lower lid from the globe until free passive motility of the lower lid was achieved. A cut-to-size piece of Gore-Tex surgical membrane was prepared and fixated with resorbable u-sutures on the inner lid. The membrane was left in place for 4 weeks until suture lysis. A silicone tube, which was transitorily fixed to the outer lower lid, had an additional ectropionizing effect. Three months later, lower-lid ectropion surgery was performed, combined with tarsectomy to obtain a long-term effect. RESULT: Six months later the lower-lid fornix had stabilized, and the lid and globe had good motility. The corneal lesions had healed. CONCLUSION: The use of 0.1 mm membrane prevents penetration of cell because of the microstructure. Similar to the "bare sclera" technique, which is used in selected cases in strabismus or pterygium surgery, the inner lid and sclera were epithelialized separately from the remaining conjunctiva. The surgical membrane prevented recurrence of the symblepharon. We think the presented technique is an easy, quick method of preventing recurrence of lid fusion after separation of symblepharons.     

The effect of topical corticosteroids on refractive outcome and corneal haze after photorefractive keratectomy

BACKGROUND: The effect of topical corticosteroids after excimer laser photorefractive keratectomy (PRK) remains a matter of some controversy. Refractive effects may be different according to the amount of myopia and timing of instillation. METHODS: Two groups of patients were studied: Study A consisted of 215 eyes (128 patients) with PRK (mean baseline myopia, -6.53 +/- 2.22 D) that received no corticosteroids (No Corticosteroid Group) unless significant regression or corneal haze appeared (Delayed Corticosteroid Group), and in Study B, we randomly assigned eyes to the Initial Corticosteroid Group (mean baseline myopia, -6.39 +/- 1.84 D) or the No/delayed Corticosteroid Group (mean baseline myopia -5.78 +/- 2.02 D). Clinical results after PRK for low-to-moderate and high myopia were compared. RESULTS: In the first group, 70.9% (73 eyes) of moderately myopic eyes (mean, -4.56 +/- 1.10 D) belonged to the No Corticosteroid Group that had a mean refraction of -5.39 +/- 1.77 D. Delayed Corticosteroid Group eyes were more myopic (mean, -7.52 +/- 2.10 D), and showed more severe haze than those in the No Corticosteroid Group. In study B, only in high myopes with more than -6.00 D (mean, -7.76 +/- 1.15 D) did refraction and corneal haze outcomes show significant difference between the Initial Corticosteroid Group and the No/delayed Corticosteroid Group. CONCLUSIONS: The effects of topical corticosteroids after PRK were less in moderate myopes compared to high myopes. Delayed instillation of corticosteroids did not reverse the regression or haze whereas initial instillation showed a beneficial effect on high myopes but not on moderate myopes.     

Reversal of the morphological effects of monocular deprivation in the kittens's lateral geniculate nucleus

1. Eleven kittens were deprived of vision in one eye until the age of between 5 and 14 weeks. Their eyes were then reverse-sutured, they were allowed to survive for a further 3-63 days, and their brains were then examined histologically. 2. Measurement of the cross-sectional area of cells in the lateral geniculate nucleus (LGN) showed that when the reversal of lid suture was performed at the age of 8 or 14 weeks, the mean cell size was smaller in laminae connected to the initially closed right eye than it was in other laminae. 3. When the reversal of lid suture took place at 5 or 6 weeks of age there was a reversal of interlaminar size differences: the initially deprived eye was then connected to laminae containing larger cells. Even within 3 days after the reversal of lid suture, most of the morphological effects of the initial suture had been abolished, and they were fully reversed within 12 days. 4. These results are compared with physiological changes in the visual cortex of these and similarly reared animals.     

The effects of topical steroids on refractive outcome and corneal haze, thickness, and curvature after photorefractive keratectomy with a 6.0-mm ablation diameter

BACKGROUND AND OBJECTIVE: To study the effect of topical prednisolone acetate after photorefractive keratectomy (PRK) using a 6.0-mm ablation diameter on the refractive and visual outcomes, corneal haze, corneal thickness, and corneal curvature in a prospective, double-masked, randomized manner. PATIENTS AND METHODS: Seventy-two eyes of 36 patients who had excimer laser PRK for correction of myopia ranging from -3.00 to -6.00 D (-4.11 +/- 0.84 D in eyes treated with steroids and -4.38 +/- 0.79 D in eyes treated with placebo; mean +/- SD) were enrolled. PRK procedures were performed using a 193-nm argon-fluoride excimer laser with 180-ml/cm2 fluence, a 10-Hz repetition rate, and a 6.0-mm ablation diameter. One eye of each patient was treated with the steroid (prednisolone acetate) and the other eye with placebo. Patients were observed for at least 12 months after PRK. RESULTS: There was no statistically significant difference between the steroid and the placebo groups with regard to refraction measurements that were taken postoperatively at 3 months (P = .39) and 12 months (P = .51). The corneas showed an increase in thickness after PRK in both groups, but the difference was not statistically significant at 12 months postoperatively (P = .45). The corneal haze score was not statistically different at any stage between groups (P = .30 at 3 months, P = .84 at 12 months). Keratometric data derived from corneal topography did not show any statistically significant difference (P = .85 at 3 months, P = .96 at 12 months). The rate of uncorrected visual acuity of 20/40 or more was 79.4% (27 eyes) in the steroid group and 70.5% (24 eyes) in the placebo group (P = .40). The rate of loss of 2 or more lines in best spectacle-corrected visual acuity was 5.85% (2 eyes) in the steroid group and 8.8% (3 eyes) in the placebo group (P = 1.0). CONCLUSION: Topical prednisolone acetate use for 3 months after PRK with a 6.0-mm ablation diameter has no effect on refractive and visual outcome, corneal haze, corneal thickness, and corneal curvature.     

Comparison of photorefractive keratectomy with excimer laser in situ keratomileusis in correcting low myopia (from -2.00 to -5.50 diopters). A randomized study

OBJECTIVE: To compare laser in situ keratomileusis (LASIK) with photorefractive keratectomy (PRK) in the correction of myopia from -2.00 to -5.50 diopters. DESIGN: Prospective, randomized, paired clinical trial. PARTICIPANTS: Fifty-two eyes of 26 myopic patients were enrolled in the study. INTERVENTION: Each patient received PRK on one eye (PRK eye) and LASIK on the other (LASIK eye); the procedure assigned to each eye, and the sequence of surgeries for each patient was randomized. MAIN OUTCOME MEASURES: Slit-lamp microscopy, manifest refraction, uncorrected and spectacle-corrected visual acuity, and videokeratography were done before operation, and 2 weeks, 6 weeks, 3 months, 6 months, and 12 months after operation. Patient satisfaction and preference were assessed by a subjective questionnaire. RESULTS: All LASIK eyes had fast, painless recovery. At 1 year, 24 patients (92.3%) were examined, the mean spherical equivalent refraction was -0.08 +/- 0.38 diopter in the PRK eyes and -0.14 +/- 0.31 diopter in the LASIK eyes, and the uncorrected visual acuity was 20/20 or better in 15 PRK eyes (62.5%) and 19 LASIK eyes (79.2%); no eye lost 2 or more Snellen lines of spectacle-corrected visual acuity. Both procedures were stable throughout the first year. One PRK eye developed dense subepithelial corneal haze. The strongest correlate to spectacle-corrected visual acuity after the two procedures was the coefficient of variation of corneal power over the pupil. Nineteen patients (79.2%) preferred the LASIK procedure because of the fast, painless recovery. CONCLUSIONS: In the current study, PRK and LASIK were found to be similarly effective, predictable, stable, and reasonably safe for the correction of myopia between -2.00 and -5.50 diopters. Laser in situ keratomileusis has the advantage of fast, painless recovery. Patients prefer LASIK.     

Retrospective comparison of photorefractive keratectomy and radial keratotomy

BACKGROUND: The efficacy and predictability of photorefractive keratectomy and radial keratotomy become increasingly relevant. This retrospective study compares one surgeon's experience with photorefractive keratectomy and radial keratotomy over a 3-year period from 1990 to 1993. METHODS: Photorefractive keratectomy was performed on 103 eyes of 76 patients that met the inclusion criteria for the phase IIb, phase III, and phototherapeutic keratectomy studies as delineated by the United States Food and Drug Administration. Radial keratotomy was performed on 117 eyes of 81 patients with up to 9.00 diopters (D) of myopia. RESULTS: In the photorefractive keratectomy group, 83% of the eyes achieved uncorrected visual acuity of at least 20/40; 37% saw 20/20; 88% had a refraction within 1.00 D of emmetropia, and 63% within 0.50 D of emmetropia. For the radial keratotomy group, 85% of the eyes achieved an uncorrected visual acuity of 20/40 or better; 27% saw 20/20; 88% had a refraction within 1.00 D of emmetropia; and 55% within 0.50 D of emmetropia. There were no serious complications, and only one single eye in each of the photorefractive keratectomy and radial keratotomy groups lost two lines or more of spectacle-corrected visual acuity. CONCLUSION: Photorefractive keratectomy and radial keratotomy are both effective procedures, and result in similar refractive outcomes for myopia of -1.00 to -9.00 D.     

Teratomas in infancy and childhood at Tygerberg Hospital, South Africa, 1973 to 1992

PURPOSE: To contribute data regarding results of reoperation with excimer laser for the treatment of residual myopia, and to improve corneal clarity following previous photorefractive keratectomy for 'moderate' (< -9 D) and 'high' (> -9 D) myopia. METHODS: Surface reablations with excimer laser (5 mm treatment diameter) were performed to correct residual myopia and remove subepithelial scars. Refraction, visual acuity, and corneal clarity were recorded with average follow-up of one and two years after reoperation. RESULTS: In 27 eyes with 'moderate' myopia before the first operation, significant improvement was obtained regarding refraction (changed from -2.3 +/- 1.56 D before retreatment to -0.58 +/- 1.31 D after retreatment (p < 10[-3])), and uncorrected visual acuity (improved to > or = 0.8 in 51.8% of the cases). All cases (6 eyes) with corneal scars improved. Six eyes with 'high' myopia showed no improvement of refraction following reoperation. Effects on corneal clarity were mixed in that group. CONCLUSION: We were able to improve the results of photorefractive keratectomy for 'moderate' myopia with a second excimer laser ablation. The risks involved in retreatments of such eyes are small. In 'high' myopia, reablations with a 5 mm treatment zone did not improve the refractive outcome on a long-term basis.     

Comparison of corneal versus through-the-lid A-scan ultrasound biometry

BACKGROUND: Accurate ultrasonography data on axial ocular dimensions in infants and toddlers are essential for understanding ocular development. Conventional methods using corneal contact with topical anesthesia but without sedation are not feasible for most of these patients. We evaluate an alternative method which places the probe on the closed eyelid. METHODS: We compared A-scan ultrasound biometry measurements taken with the probe directly on the cornea with those with the probe on the closed eyelid on the right eye of 35 young adult subjects. RESULTS: There was no significant difference between methods for mean anterior chamber depth (corneal = 3.83 mm, lid = 3.87 mm, p = 0.13, paired t-test). The mean lens thickness (corneal = 3.63 mm, lid = 3.75 mm, p = 0.0001, paired t-test) and mean vitreous chamber depth (corneal = 17.50 mm, lid = 17.68 mm, p = 0.0440, paired t-test) were significantly different. CONCLUSION: Ultrasonography through the closed eyelid appears to be a viable method with acceptable validity compared with corneal ultrasound. Poorer agreement for lens thickness and vitreous chamber depth may be undesirable, but these data should be useful for planning future studies of infants and toddlers.     

The Glenn A. Fry Award Lecture (1995). Myopia development in childhood

PURPOSE: The Orinda Longitudinal Study of Myopia is a 12-year project examining predictive factors for the onset of myopia, the underlying etiologies of myopia, and normal eye growth in school children. METHODS: This paper reports on all measurements made of the ocular components (cycloplegic refractive error, corneal curvature, crystalline lens power, and axial ocular dimensions), parental history of myopia, and near work activity in children participating in the Orinda Longitudinal Study of Myopia between 1989 and 1993. An analysis of the interaction between parental history of myopia and children's near work is conducted on the cross-sectional study data from 1993. RESULTS: The cross-sectional and longitudinal data show a gradual decrease in refractive error from low hyperopia toward emmetropia, no shift in corneal curvature, a gradual decrease in crystalline lens power, thinning of the crystalline lens, and elongation of the eye between the ages of 6 and 14 years. Parental history is more contributory to a statistical model predicting myopia than is near work, but near work is a significant factor as well. We can find no evidence of statistical interaction between parental history and near work in explaining the presence or absence of myopia. CONCLUSIONS: The emmetropization process is evident in the gradual decrease in refractive error toward emmetropia, the axial elongation of the eye, and the compensating decrease in crystalline lens power. Both nature and nurture play a role in the etiology of myopia, although the predominant role appears to belong to a positive parental history of myopia. This role does not appear to be through an interaction between parental myopia status and children's near work activity.     

Psychosocial problems in Huntington chorea. 2: Results and experiences from a 5-year project

PURPOSE: To establish the prevalence and severity of myopia among the Chinese Hong Kong students and to study the relationship between myopia and optical components. METHODS: One thousand and seventy-five freshmen of the 1993-1994 academic year in the Chinese University of Hong Kong underwent the eye examination including evaluation of refractive error, keratometry, and A-scan ultrasonic biometry. The data were analyzed with the SPSS/PC+4.01 statistical package. RESULTS: The prevalence of myopia was 91.7% with the mean refraction being -4.00 +/- 2.64D in this young adult population. The statistical analyses demonstrated a significant correlation between refractive value and axial length of the globe (r = -0.78), vitreous length (r = -0.76), anterior chamber depth (r = -0.33), lens thickness (r = 0.13) and corneal curvature (r = 0.19). CONCLUSION: The refractive status is mainly dependent on the axial length. In general, the higher the myopia was, the longer the eyeball, the deeper the anterior chamber, the steeper the cornea, and the thinner the lens would be.