Pre-term delivery and the growth of the eye. An oculometric study of eye size around term-time

Wide-field digital imaging system for assessing ocular anterior segment development in very preterm infants

Purpose

This study aims to longitudinally investigate developments of the anterior segment in very preterm infants who exhibit normal retinal development outcomes by utilizing a wide-field digital imaging system.

Methods

Between June 2021 and June 2022, neonates with a birth weight of <1500 g and/or a gestational age (GA) of less than 32 weeks were included in this study. The participants underwent regular ocular examinations, including sequential evaluations of the anterior segment and the retina, at intervals of 2-5 weeks, starting from birth and continuing until they reached a corrected GA of 48 weeks. Term neonates were selected as normal controls for the study. The study recorded the weight and GA of subjects at the time of examination, as well as indicators of abnormal development in the anterior segment.

Results

A total of 48 very preterm infants with normal retinal developmental outcomes were enrolled. The control group included 59 full-term infants. Common anterior segment eye abnormalities such as persistent hyperplasia of primary vitreous, persistent pupillary membranes, iris vessels, and anterior chamber angle vessels gradually subsided with the period in very preterm infants. The vascularity of the iris was substantially higher than in term controls (P < 0.05) at term gestation. The imaging of iris vessels and anterior chamber angle vessels in very preterm infants exhibited a decline at 46 and 47 weeks, respectively, which occurred slightly later compared to term infants.

Conclusion

In very preterm infant s with normal outcomes, although the developmental process is delayed, they may form a normal anterior segment structure similar to that of full-term infants in the late stages, which is followed up by the wide-field digital imaging system.

[Ophthalmic care of adults born preterm and full-term-results from the Gutenberg Prematurity Eye Study (GPES) : Premature birth and ophthalmological care]

BACKGROUND

Prematurity and the presence of retinopathy of prematurity (ROP) increase the risk for the occurrence of amblyogenic risk factors in childhood and adolescence.

AIM

The aim of the present study was to evaluate ocular morbidities and the ophthalmological care of former preterm and full-term persons in adulthood.

MATERIAL AND METHODS

The Gutenberg prematurity eye study (GPES) is a retrospective cohort study with a prospective ophthalmological examination of individuals formerly born preterm and full term between 1969 and 2002 (now aged 18-52 years). All participants underwent a detailed ophthalmological examination and were asked about the frequency of ophthalmological care. Participants were grouped into those with normal gestational age (GA) ≥ 37 weeks (control group), preterm individuals without ROP and GA 33-36 weeks (group 2), GA 29-32 weeks (group 3), GA ≤ 28 weeks (group 4), and those with ROP without treatment (group 5) and with ROP with treatment (group 6). All participants were asked if they had an ophthalmological examination within the last 12 months.

RESULTS

In total, data from 140 term and 310 preterm adults were included in the present study. Strabismus was present in 2.1 % (3/140), 6.6 % (9/137), 17.4 % (16/92), 11.1 % (2/18), 27.1 % (13/48) and 60 % (9/15) in groups 1-6, respectively. The proportion of subjects with an ophthalmological examination within the last 12 months was highest in the groups of extremely preterm persons with and without ROP compared with the control group. Overall, 33.3 % (1/3) of the term and 57.1 % (28/49) of the preterm subjects with strabismus and 0 % (0/3) of the term and 46.9 % (15/32) of the preterm individuals with amblyopia had an ophthalmological examination within the past 12 months.

DISCUSSION

Extremely preterm adults with and without postnatal ROP showed the highest rate of eye diseases as well as the highest rate of ophthalmological check-ups within the last 12 months. This suggests that extremely preterm adults particularly with the occurrence of postnatal ROP perceive more frequent ophthalmological check-ups throughout their lives.

Congenital Cataracts in Preterm Infants: A Review

A congenital cataract is one of the most treatable causes of visual impairment during infancy. Preterm infants who are born alive before 37 weeks of pregnancy need special care, including proper age documentation, preoperative assessment, and monitoring postoperatively for at least 24 hours. Management of cataracts in preterm infants is critical as regards the timing of cataract surgery and the challenges associated with cataract surgery and posterior segment management for retinopathy of prematurity (ROP). This narrative review aims to provide comprehensive insight and up-to-date clinical research findings regarding the pathophysiology and management of congenital cataracts in preterm infants.

Emmetropization and nonmyopic eye growth

Most eyes start with a hypermetropic refractive error at birth, but the growth rates of the ocular components, guided by visual cues, will slow in such a way that this refractive error decreases during the first 2 years of life. Once reaching its target, the eye enters a period of stable refractive error as it continues to grow by balancing the loss in corneal and lens power with the axial elongation. Although these basic ideas were first proposed over a century ago by Straub, the exact details on the controlling mechanism and the growth process remained elusive. Thanks to the observations collected in the last 40 years in both animals and humans, we are now beginning to get an understanding how environmental and behavioral factors stabilize or disrupt ocular growth. We survey these efforts to present what is currently known regarding the regulation of ocular growth rates.

Refractive development I: Biometric changes during emmetropisation

PURPOSE

Although there are many reports on ocular growth, these data are often fragmented into separate parameters or for limited age ranges. This work intends to create an overview of normal eye growth (i.e., in absence of myopisation) for the period before birth until 18 years of age.

METHODS

The data for this analysis were taken from a search of six literature databases using keywords such as "[Parameter] & [age group]", with [Parameter] the ocular parameter under study and [age group] an indication of age. This yielded 34,409 references that, after screening of title, abstract and text, left 294 references with usable data. Where possible, additional parameters were calculated, such as the Bennett crystalline lens power, whole eye power and axial power.

RESULTS

There were 3422 average values for 17 parameters, calculated over a combined total of 679,398 individually measured or calculated values. The age-related change in refractive error was best fitted by a sum of four exponentials (r²  = 0.58), while all other biometric parameters could be fitted well by a sum of two exponentials and a linear term ('bi-exponential function'; r² range: 0.64-0.99). The first exponential of the bi-exponential fits typically reached 95% of its end value before 18 months, suggesting that these reached genetically pre-programmed passive growth. The second exponentials reached this point between 4 years of age for the anterior curvature and well past adulthood for most lenticular dimensions, suggesting that this part represents the active control underlying emmetropisation. The ocular components each have different growth rates, but growth rate changes occur simultaneously at first and then act independently after birth.

CONCLUSIONS

Most biometric parameters grow according to a bi-exponential pattern associated with passive and actively modulated eye growth. This may form an interesting reference to understand myopisation.

Anterior Chamber Angle and Anterior Segment Structure of Eyes in Children With Early Stages of Retinopathy of Prematurity

PURPOSE

To compare structural differences in the anterior chamber angle (ACA) and related optic components in children with or without retinopathy of prematurity (ROP).

DESIGN

Prospective cross-sectional study.

METHODS

Setting: A referred medical center in Taiwan.

STUDY POPULATION

The patients included preterm children with a history of ROP who had undergone laser therapy. The controls included age-matched healthy full-term children.

OBSERVATION PROCEDURE

The ACA structures were evaluated using gonioscopy.

MAIN OUTCOME MEASURES

The angularity of the anterior chamber and associated anatomic changes.

RESULTS

We examined 54 eyes of 29 preterm children with ROP and 134 eyes of 67 children born at term. The eyes of the ROP children exhibited a narrower ACA, steeper iris curvature, and more anteriorly inserted iris than those of the full-term children (P < .001, P = .002, and P = .08, respectively). The eyes of the ROP children also exhibited steeper corneas, shallower anterior chamber depths, thicker lenses, and higher degrees of refractive errors (all P < .001) than those of the full-term children. The axial lengths did not differ between the 2 groups (P = .15).

CONCLUSIONS

The eyes of the ROP children presented a narrower ACA and a more anteriorly curved and inserted iris than those of the full-term children. A steeper cornea, shallower anterior chamber, and greater lens thickness were the main structural changes in the anterior segment components of these patients. Further research is needed to investigate the association between these structural changes and the development of certain ocular diseases, such as glaucoma, in these patients.

Evaluation of structural contributors in myopic eyes of preterm and full-term children

PURPOSE

We conducted a cross-sectional study to test the hypothesis that the structural contributions to myopia in preterm and full-term born children are different.

METHODS

In this study, 93 children ranging from ages 2 to 13 who had myopia ≥ -3 diopters in at least one eye were examined with A-scans. The following data was collected and analyzed: history of birth, refractive error (RE), cornea thickness (CT) and average corneal curvature (AVK), depth of anterior chamber (ACD), lens thickness (LT), and axial length (AL) of the eye.

RESULTS

Eyes were tested and categorized into four groups: myopic eyes in full-term children (group 1), myopic eyes in premature children (group 2), non-myopic eyes in full-term children (group 3), and non-myopic eyes in preterm children (group 4). The RE were similar between group 1 and group2, and between group 3 and group 4. Myopic eyes in group 2 had higher AVK as compared to group 3; 45.4 ± 0.4 D vs. 43.5 ± 0.7 D, p = 0.008. The ACD in group 2 was shallower than that in group 1 (2.5 ± 0.5 vs. 3.2 ± 0.3, p = 0.01). The LT measurements in group 2 were thicker than those in group 1 (mean LT = 4.9 ± 1.0 vs 4.1 ± 0.3 mm, p = 0.001, respectively). Finally, AL of myopic eyes in group 1 was longer than that of group 2, p = 0.01.

CONCLUSION

These results suggest that increased axial length plays an important role in myopia in full-term children, whereas corneal curvature and lens thickness are major contributors to myopia in preterm children.

Eye growth in term- and preterm-born eyes modeled from magnetic resonance images

PURPOSE

We generated a model of eye growth and tested it against an eye known to develop abnormally, one with a history of retinopathy of prematurity (ROP).

METHODS

We reviewed extant magnetic resonance images (MRIs) from term and preterm-born patients for suitable images (n = 129). We binned subjects for analysis based upon postmenstrual age at birth (in weeks) and ROP history ("Term" ≥ 37, "Premature" ≤ 32 with no ROP, "ROP" ≤ 32 with ROP). We measured the axial positions and curvatures of the cornea, anterior and posterior lens, and inner retinal surface. We fit anterior chamber depth (ACD), posterior segment depth (PSD), axial length (AL), and corneal and lenticular curvatures with logistic growth curves that we then evaluated for significant differences. We also measured the length of rays from the centroid to the surface of the eye at 5° intervals, and described the length versus age relationship of each ray, L(ray)(x), using the same logistic growth curve. We determined the rate of ray elongation, E(ray)(x), from L(ray)dy/dx. Then, we estimated the scleral growth that accounted for E(ray)(x), G(x), at every age and position.

RESULTS

Relative to Term, development of ACD, PSD, AL, and corneal and lenticular curvatures was delayed in ROP eyes, but not Premature eyes. In Term infants, G(x) was fast and predominantly equatorial; in age-matched ROP eyes, maximal G(x) was offset by approximately 90°.

CONCLUSIONS

We produced a model of normal eye growth in term-born subjects. Relative to normal, the ROP eye is characterized by delayed, abnormal growth.

The rat with oxygen-induced retinopathy is myopic with low retinal dopamine

PURPOSE

Dopamine (DA) is a neurotransmitter implicated both in modulating neural retinal signals and in eye growth. Therefore, it may participate in the pathogenesis of the most common clinical sequelae of retinopathy of prematurity (ROP), visual dysfunction and myopia. Paradoxically, in ROP myopia the eye is usually small. The eye of the rat with oxygen-induced retinopathy (OIR) is characterized by retinal dysfunction and short axial length. There have been several investigations of the early maturation of DA in rat retina, but little at older ages, and not in the OIR rat. Therefore, DA, retinal function, and refractive state were investigated in the OIR rat.

METHODS

In one set of rats, the development of dopaminergic (DAergic) networks was evaluated in retinal cross-sections from rats aged 14 to 120 days using antibodies against tyrosine hydroxylase (TH, the rate-limiting enzyme in the biosynthesis of DA). In another set of rats, retinoscopy was used to evaluate spherical equivalent (SE), electoretinography (ERG) was used to evaluate retinal function, and high-pressure liquid chromatography (HPLC) was used to evaluate retinal contents of DA, its precursor levodopamine (DOPA), and its primary metabolite 3,4-dihydroxyphenylacetic acid (DOPAC).

RESULTS

The normally rapid postnatal ramification of DAergic neurons was disrupted in OIR rats. Retinoscopy revealed that OIR rats were relatively myopic. In the same eyes, ERG confirmed retinal dysfunction in OIR. HPLC of those eyes' retinae confirmed low DA. Regression analysis indicated that DA metabolism (evaluated by the ratio of DOPAC to DA) was an important additional predictor of myopia beyond OIR.

CONCLUSIONS

The OIR rat is the first known animal model of myopia in which the eye is smaller than normal. Dopamine may modulate, or fail to modulate, neural activity in the OIR eye, and thus contribute to this peculiar myopia.

Next-generation sequencing analysis of gene regulation in the rat model of retinopathy of prematurity

PURPOSE

The purpose of this study was to identify the genes, biochemical signaling pathways, and biological themes involved in the pathogenesis of retinopathy of prematurity (ROP).

METHODS

Next-generation sequencing (NGS) was performed on the RNA transcriptome of rats with the Penn et al. (Pediatr Res 36:724-731, 1994) oxygen-induced retinopathy model of ROP at the height of vascular abnormality, postnatal day (P) 19, and normalized to age-matched, room-air-reared littermate controls. Eight custom-developed pathways with potential relevance to known ROP sequelae were evaluated for significant regulation in ROP: The three major Wnt signaling pathways, canonical, planar cell polarity (PCP), and Wnt/Ca(2+); two signaling pathways mediated by the Rho GTPases RhoA and Cdc42, which are, respectively, thought to intersect with canonical and non-canonical Wnt signaling; nitric oxide signaling pathways mediated by two nitric oxide synthase (NOS) enzymes, neuronal (nNOS) and endothelial (eNOS); and the retinoic acid (RA) signaling pathway. Regulation of other biological pathways and themes was detected by gene ontology using the Kyoto Encyclopedia of Genes and Genomes and the NIH's Database for Annotation, Visualization, and Integrated Discovery's GO terms databases.

RESULTS

Canonical Wnt signaling was found to be regulated, but the non-canonical PCP and Wnt/Ca(2+) pathways were not. Nitric oxide signaling, as measured by the activation of nNOS and eNOS, was also regulated, as was RA signaling. Biological themes related to protein translation (ribosomes), neural signaling, inflammation and immunity, cell cycle, and cell death were (among others) highly regulated in ROP rats.

CONCLUSIONS

These several genes and pathways identified by NGS might provide novel targets for intervention in ROP.

Alterations of the tunica vasculosa lentis in the rat model of retinopathy of prematurity

PURPOSE

To study the relationship between retinal and tunica vasculosa lentis (TVL) disease in retinopathy of prematurity (ROP). Although the clinical hallmark of ROP is abnormal retinal blood vessels, the vessels of the anterior segment, including the TVL, are also altered.

METHODS

ROP was induced in Long-Evans pigmented and Sprague Dawley albino rats; room-air-reared (RAR) rats served as controls. Then, fluorescein angiographic images of the TVL and retinal vessels were serially obtained with a scanning laser ophthalmoscope near the height of retinal vascular disease, ~20 days of age, and again at 30 and 64 days of age. Additionally, electroretinograms (ERGs) were obtained prior to the first imaging session. The TVL images were analyzed for percent coverage of the posterior lens. The tortuosity of the retinal arterioles was determined using Retinal Image multiScale Analysis (Gelman et al. in Invest Ophthalmol Vis Sci 46:4734-4738, 2005).

RESULTS

In the youngest ROP rats, the TVL was dense, while in RAR rats, it was relatively sparse. By 30 days, the TVL in RAR rats had almost fully regressed, while in ROP rats, it was still pronounced. By the final test age, the TVL had completely regressed in both ROP and RAR rats. In parallel, the tortuous retinal arterioles in ROP rats resolved with increasing age. ERG components indicating postreceptoral dysfunction, the b-wave, and oscillatory potentials were attenuated in ROP rats.

CONCLUSIONS

These findings underscore the retinal vascular abnormalities and, for the first time, show abnormal anterior segment vasculature in the rat model of ROP. There is delayed regression of the TVL in the rat model of ROP. This demonstrates that ROP is a disease of the whole eye.

Refractive Development in the "ROP Rat"

Although retinopathy of prematurity (ROP) is clinically characterized by abnormal retinal vessels at the posterior pole of the eye, it is also commonly characterized by vascular abnormalities in the anterior segment, visual dysfunction which is based in retinal dysfunction, and, most commonly of all, arrested eye growth and high refractive error, particularly (and paradoxically) myopia. The oxygen-induced retinopathy rat model of ROP presents neurovascular outcomes similar to the human disease, although it is not yet known if the "ROP rat" also models the small-eyed myopia characteristic of ROP. In this study, magnetic resonance images (MRIs) of albino (Sprague-Dawley) and pigmented (Long-Evans) ROP rat eyes, and age- and strain-matched room-air-reared (RAR) controls, were examined. The positions and curvatures of the various optical media were measured and the refractive state (℞) of each eye estimated based on a previously published model. Even in adulthood (postnatal day 50), Sprague-Dawley and Long-Evans ROP rats were significantly myopic compared to strain-matched controls. The myopia in the Long-Evans ROP rats was more severe than in the Sprague-Dawley ROP rats, which also had significantly shorter axial lengths. These data reveal the ROP rat to be a novel and potentially informative approach to investigating physiological mechanisms in myopia in general and the myopia peculiar to ROP in particular.

Refractive status and ocular axial length in preterm infants without retinopathy of prematurity with regard to birth weight and gestational age

PURPOSE

To obtain ultrasonographic measurements of ocular axial length (AL) in preterm infants without retinopathy of prematurity (ROP) but with different refractive power in regard to birth weight (BW) and gestational age (GA).

METHODS

Refraction was measured after cycloplegia (at 6 months of life) in 350 eyes of 180 preterm (non-astigmatic) infants without ROP. Subjects were grouped according to the refractive error: A [above -6.0 dioptres (D)]; B (-3.1 to -6.0 D); C (0 to -3.0 D); D (0.1 to +3.0 D); E (+3.1 to +6.0 D); F (above +6.0 D). The AL measurement was performed by ocular A-scan ultrasound biometry (10 MHz probe).

RESULTS

The longest AL was found in group B (20.62 mm) compared to group D and E (19.35, 19.28 mm; P< or =0.01) and group F and A (19.63, 19.39 mm; P< or =0.05). Only regressive correction for BW was statistically significant. Correlations between AL and BW (Rs=0.23) or GA (Rs=0.17) were found only in group E.

CONCLUSIONS

AL of myopic eyes was significantly longer. In general, hyperopia was positively correlated with BW, whereas correlation between myopia and BW or GA was not found.

Ocular hemorrhages in neonatal porcine eyes from single, rapid rotational events

PURPOSE

To characterize ocular hemorrhages from single, rapid head rotations in the neonatal pig.

METHODS

Three- to 5-day-old anesthetized piglets (n=51) underwent a single, rapid (117-266 rad/s) head rotation in the sagittal (n=13), coronal (n=7), or axial (n=31) planes. Six hours after injury, the animals were euthanatized and perfusion fixed, and the brain and eyes were harvested for gross and histopathologic examination by masked neuro- and ocular pathologists.

RESULTS

Ocular hemorrhage was found in 73% of animals (51% bilateral). Intraocular hemorrhage was primarily located near the vitreous base (70% of injured animals had ciliary body hemorrhage, and 11% had peripheral retinal hemorrhage). Hemorrhages were also found in the anterior chamber (11%), vitreous (5%), and optic nerve (disc, 8%; nerve sheath, 57%). Rapid axial head rotations resulted in a higher incidence of intraocular hemorrhage than coronal or sagittal head rotations, but the difference did not reach statistical significance (P=0.06). Control eyes had no injuries.

CONCLUSIONS

Optic nerve sheath and ciliary body hemorrhages were common in piglets that experienced a single, rapid head rotation. Retinal hemorrhage was present in a smaller number of animals. Most intraocular hemorrhages were located in regions of strong vitreous attachment, suggesting that this animal model will be useful in investigating the effect of vitreoretinal adhesion on ocular hemorrhage caused by inertial head rotations. Extrapolation of this model to the human infant should not be made until the effect of anatomic differences between the human and pig on the occurrence and patterns of ocular injuries is further investigated.

The neurovascular retina in retinopathy of prematurity

The continuing worldwide epidemic of retinopathy of prematurity (ROP), a leading cause of childhood visual impairment, strongly motivates further research into mechanisms of the disease. Although the hallmark of ROP is abnormal retinal vasculature, a growing body of evidence supports a critical role for the neural retina in the ROP disease process. The age of onset of ROP coincides with the rapid developmental increase in rod photoreceptor outer segment length and rhodopsin content of the retina with escalation of energy demands. Using a combination of non-invasive electroretinographic (ERG), psychophysical, and image analysis procedures, the neural retina and its vasculature have been studied in prematurely born human subjects, both with and without ROP, and in rats that model the key vascular and neural parameters found in human ROP subjects. These data are compared to comprehensive numeric summaries of the neural and vascular features in normally developing human and rat retina. In rats, biochemical, anatomical, and molecular biological investigations are paired with the non-invasive assessments. ROP, even if mild, primarily and persistently alters the structure and function of photoreceptors. Post-receptor neurons and retinal vasculature, which are intimately related, are also affected by ROP; conspicuous neurovascular abnormalities disappear, but subtle structural anomalies and functional deficits may persist years after clinical ROP resolves. The data from human subjects and rat models identify photoreceptor and post-receptor targets for interventions that promise improved outcomes for children at risk for ROP.

Higher order monochromatic aberrations of the human infant eye

The monochromatic optical aberrations of the eye degrade retinal image quality. Any significant aberrations during postnatal development could contribute to infants' immature visual performance and provide signals for the control of eye growth. Aberrations of human infant eyes from 5 to 7 weeks old were compared with those of adult subjects using a model of an adultlike infant eye that accounted for differences in both eye and pupil size. Data were collected using the COAS Shack-Hartmann wavefront sensor. The results demonstrate that the higher order aberrations of the 5-to-7-week-old eye are less than a factor of 2 greater than predicted for an adultlike infant eye of this age. The data are discussed in the context of infants' visual performance and the signals available for controlling growth of the eye.

Refraction and keratometry in 40 week old premature (corrected age) and term infants

AIM

To compare refraction and keratometry readings between premature and term babies at 40 weeks' postconceptional age (PCA), and the possible effect of birth weight (BW) and gestational age (GA) on ocular parameters.

METHODS

33 preterm babies hospitalised in the neonatal unit between January and March 2002 were matched with 33 term babies born within the same period and hospitalised in the same unit. The preterm group underwent funduscopy at 4-5 weeks after delivery. Ophthalmic examination at 40 weeks' PCA included cycloplegic retinoscopy, funduscopy, and keratometric measurements. Mean and standard deviation of refraction, astigmatic power (plus cylinder), axis of astigmatism, and keratometric reading were calculated and compared between groups and correlated with BW and GA in the premature babies.

RESULTS

Retinopathy of prematurity (ROP) stage 1 or 2 was noted in 88% of the premature babies on the first funduscopy examination, but only in 36% by the corrected age of 40 weeks. Statistically significant between groups differences were found for cycloplegic refraction (p = 0.02 for both eyes) and keratometry (p = 0.001 for both eyes). GA and BW had no impact on the refractive and keratometric findings in the preterm babies.

CONCLUSIONS

Babies with mild ROP at the corrected age of 40 weeks have mild hypermetropia compared to the moderate hypermetropia found in term babies (a difference of 50%), and they have higher and steeper keratometric values. The greater corneal curvature may contribute to the development of myopia. Ophthalmologists and parents need to be aware of the possibility of visual dysfunction already very early in life even in relatively older premature infants.

Emmetropisation following preterm birth

BACKGROUND/AIMS

Even in the absence of retinopathy of prematurity (ROP), premature birth signals increased risk for abnormal refractive development. The present study examined the relation between clinical risk factors and refractive development among preterm infants without ROP.

METHODS

Cycloplegic refraction was measured at birth, term, 6, 12, and 48 months corrected age in a cohort of 59 preterm infants. Detailed perinatal history and cranial ultrasound data were collected. 40 full term (plus or minus 2 weeks) subjects were tested at birth, 6, and 12 months old.

RESULTS

Myopia and anisometropia were associated with prematurity (p<0.05). More variation in astigmatic axis was found among preterm infants (p<0.05) and a trend for more astigmatism (p<0.1). Emmetropisation occurred in the preterm infants so that at term age they did not differ from the fullterm group in astigmatism or anisometropia. However, preterm infants remained more myopic (less hyperopic) than the fullterm group at term (p<0.05) and those infants born <1500 g remained more anisometropic than their peers until 6 months (p<0.05). Infants with abnormal cranial ultrasound were at risk for higher hyperopia (p<0.05). Other clinical risk factors were not associated with differences in refractive development. At 4 years of age 19% of the preterm group had clinically significant refractive errors.

CONCLUSION

Preterm infants without ROP had high rates of refractive error. The early emmetropisation process differed from that of the fullterm group but neither clinical risk factors nor measures of early refractive error were predictive of refractive outcome at 4 years.

Intraocular lenses in children: changes in axial length, corneal curvature, and refraction

AIM

To assess changes in axial length, corneal curvature, and refraction in paediatric pseudophakia.

METHODS

35 eyes of 24 patients with congenital or developmental lens opacities underwent extracapsular cataract extraction and posterior chamber intraocular lens implantation. Serial measurements were made of axial length, corneal curvature, objective refraction, and visual acuity.

RESULTS

For patients with congenital cataracts (onset < 1 year age) the mean age at surgery was 24 weeks. Over the mean follow up period of 2.7 years, the mean increase in axial length of 3.41 mm was not significantly different from the value of an expected mean growth of 3.44 mm (paired t test, p = 0.97) after correction for gestational age. In the developmental cataract group (onset > 1 year of age) the mean age at surgery was 6.4 years with a mean follow up of 2.86 years. This group showed a mean growth in axial length of 0.36 mm that was not significantly different from an expected value of 0.47 mm (paired t test, p = 0.63). The mean preoperative keratometry was 47.78 D in the congenital group and 44.35 D in the developmental group. At final follow up the mean keratometry in the congenital group was 46.15 D and in the developmental group it was 43.63 D. In eyes followed for at least 2 years, there was an observed myopic shift by 24 months postoperatively of 3.26 D in the congenital cases (n = 10) and 0.96 D in the developmental cases (n = 18).

CONCLUSION

The pattern of axial elongation and corneal flattening was similar in the congenital and developmental groups to that observed in normal eyes. No significant retardation or acceleration of axial growth was found in the eyes implanted with IOLs compared with normal eyes. A myopic shift was seen particularly in eyes operated on at 4-8 weeks of age and it is recommended that these eyes are made 6 D hypermetropic initially with the residual refractive error being corrected with spectacles.

Scleral buckling surgery in stage 4 retinopathy of prematurity

BACKGROUND

Technical advances in neonatal intensive care have significantly increased the number of very low birth-weight babies that survive the perinatal period. Some of these infants develop severe retinopathy of prematurity that may lead to retinal detachment.

METHODS

Between November 1988 and January 1994, 28 eyes from 15 preterm babies underwent scleral buckling for stage 4 retinopathy of prematurity at a mean age of 4.2 months. Cryotherapy was performed preoperatively on 12 eyes and intraoperatively in the remaining 16 eyes. The mean follow-up period was 35 months.

RESULTS

Scleral buckling produced retinal reattachment in 13 eyes (46.4%). Severe myopia (-5 D to -15 D) was found in all 13 of these eyes, 12 also presented convergent strabismus. Mean visual acuity, measured in 6 eyes from children over the age of 3 years was 20/40. In 7/28 eyes of the younger children of this group we found a fix and follow the light capability. No light perception was detected in 11/28 eyes; in the remaining 4/28 eyes there was only light perception. Scleral buckling failed to prevent the progression to stage 5 in 15 eyes (53.6%). Additional surgery was excluded for 9 of these eyes based on ultrasonography findings; the other 6 eyes underwent vitrectomy, which led to macular reattachment in 4 cases.

CONCLUSIONS

Clinical experience shows that scleral buckling is not always capable of preventing progression of the disease to stage 5. Furthermore, even when the anatomic results of this procedure are good, the functional outcome is often complicated by severe visual impairment.

Refractive outcome following diode laser versus cryotherapy for eyes with retinopathy of prematurity

The refractive error in 15 eyes with threshold retinopathy of prematurity treated with diode laser photocoagulation was compared with 25 eyes with the same disease severity treated by cryotherapy. Myopia was present in 40% (six eyes) of the first group ranging from -1.50 to -3.50 dioptres; while 92% (23 eyes) showed myopia which ranged from -0.50 to -8.00 dioptres in the cryotherapy group. Sixty per cent (nine eyes) were hypermetropic at less than +3.0 dioptres in the laser group, while only 8% (two eyes) of the cryotherapy group showed hypermetropia. There was no significant difference in astigmatism between the two groups. Eyes with threshold disease treated with diode laser photocoagulation developed significantly less myopia than those treated with cryotherapy (p = 0.0006, two tailed value).