Quality of life and functional vision concerns of children with cataracts and their parents.

PurposeTo identify specific health-related quality of life (HRQOL) and functional vision concerns affecting children with cataracts and common associated conditions as expressed by children or one of their parents (proxy), and HRQOL concerns affecting the parents themselves.MethodsIndividual semi-structured interviews were conducted with parents of children with cataracts (N=31) and with the children themselves (ages 5-17 years; N=16). Transcripts of recorded interviews were evaluated using NVivo software. Specific concerns were identified and coded, and broad themes were identified. The frequency of each theme was calculated, with the frequency of specific concerns within each theme.ResultsRegarding the child's experience, 6 themes were identified: Visual Function (mentioned by 16 of 16 children (100%) and by 26 of 31 parents (84%), Social (94 and 65%), Treatment (81 and 90%), Worry (75 and 10%), Emotions (63 and 68%), and Physical Discomfort (63 and 26%). Worry showed the largest discrepancy between child and their parent; although 75% children reported Worry, only 6% of parents reported that their child experienced Worry (P=0.0009). Regarding the parents' own experience, 5 themes were identified: Worry (100%), Compensation for Condition (100%), Treatment (94%), Emotions (90%), and Affects Family (52%).ConclusionsA wide range of concerns were identified from interviews of children with cataracts and their parents. Concerns reflect the impact of cataracts in physical, emotional, and social domains, and specific concerns will be used for the development of questionnaires to quantify the quality of life and functional vision effects of cataracts.

Prevalence and Serogroup Diversity of Salmonella for Broiler Neck Skin, Whole Carcass Rinse, and Whole Carcass Enrichment Sampling Methodologies following Air or Immersion Chilling.

The purpose of this study was to evaluate neck skin (NS), whole carcass rinse (WCR), and whole carcass enrichment (WCE) sampling procedures for Salmonella isolation and serogroup identification from the same broiler chicken carcass treated with air or immersion chilling. Commercially processed and eviscerated broiler carcasses were collected from a commercial processing plant, individually bagged, and transported to the pilot processing plant. In experiment 1, carcasses were air chilled to 4°C. In experiment 2, carcasses were immersion chilled with or without chlorine. After air chilling, Salmonella was detected on 78% of NS and 89% of WCE samples. Only one Salmonella serogroup was detected from each of 13 Salmonella-positive NS samples, and two serogroups were detected on 1 Salmonella-positive NS sample. Only one Salmonella serogroup was detected from each of 13 Salmonella-positive WCE samples, and two serogroups were detected from 3 Salmonella-positive WCE samples. After immersion chilling without chlorine, Salmonella was detected on 38% of NS, 45% of WCR, and 100% of WCE samples. Without chlorine, the 15 Salmonella-positive NS samples included 14 samples with one serogroup and 1 sample with two serogroups. Only one Salmonella serogroup was detected from WCR samples after immersion chilling. Of 40 Salmonella-positive WCE samples, 23 had a one, 14 had two, and 3 had three Salmonella serogroups. After immersion chilling with chlorine, Salmonella was detected on 35% of NS, 0% of WCR, and 90% of WCE samples. With chlorine, the 14 Salmonella-positive NS samples included 11 samples with one serogroup and 3 samples with two serogroups. No Salmonella serogroups were detected from WCR samples after immersion chilling with 20 mg/liter free chlorine. The 36 Salmonella-positive WCE samples included 21 samples with one serogroup and 15 samples with two serogroups. NS and WCE sampling methodologies yielded similar prevalence and serogroup diversity after air chilling. However, after immersion chilling with or without chlorine, WCE sampling yielded significantly higher (α ≤ 0.05) prevalence and serogroup diversity than either NS or WCR sampling methodologies.

Is intermittent exotropia a curable condition?

Surgical treatment of childhood intermittent exotropia (XT) is associated with high recurrence rates. In addition, the natural history of intermittent XT has not been rigorously studied and, anecdotally, some cases resolve without surgery. We compared long-term cure rates in children with surgically and non-surgically managed intermittent XT. Children undergoing surgery for intermittent XT who had 5 years follow-up were retrospectively identified. A non-surgical cohort of comparable children was selected by matching each surgical patient for age at onset and age at the 5-year examination. Cure was defined as no manifest tropia on examination or by history, no new monofixation (stereoacuity subnormal for age), and no additional surgery. Each group had 33 children (total follow-up from presentation 7.2±2.6 years in the surgical group vs 6.8±2.3 years). There were no significant differences between groups for age at onset, age at presentation, or distance or near angle of deviation at presentation (all P≥0.4). The cure rate at 5 years was 30% in the surgical group and 12% in the non-surgical group (P=0.1; difference 18%, 95% CI -1 to 37%). Only a small proportion of surgical and non-surgical patients met our definition of cure, with the vast majority demonstrating a constant or intermittent manifest deviation after an average of 7 years follow-up. In childhood intermittent XT, long-term cure is difficult to achieve with surgical intervention, and in some patients managed non-surgically the intermittent XT will spontaneously resolve.

Thoroughbred horses in race training have lower levels of subchondral bone remodelling in highly loaded regions of the distal metacarpus compared to horses resting from training.

Bone is repaired by remodelling, a process influenced by its loading environment. The aim of this study was to investigate the effect of a change in loading environment on bone remodelling by quantifying bone resorption and formation activity in the metacarpal subchondral bone in Thoroughbred racehorses. Sections of the palmar metacarpal condyles of horses in race training (n = 24) or resting from training (n = 24) were examined with light microscopy and back scattered scanning electron microscopy (BSEM). Bone area fraction, osteoid perimeter and eroded bone surface were measured within two regions of interest: (1) the lateral parasagittal groove (PS); (2) the lateral condylar subchondral bone (LC). BSEM variables were analysed for the effect of group, region and interaction with time since change in work status. The means ± SE are reported. For both regions of interest in the training compared to the resting group, eroded bone surface was lower (PS: 0.39 ± 0.06 vs. 0.65 ± 0.07 per mm, P = 0.010; LC: 0.24 ± 0.04 vs. 0.85 ± 0.10 per mm, P < 0.001) and in the parasagittal groove osteoid perimeter was higher (0.23 ± 0.04% vs. 0.12 ± 0.02%). Lower porosity was observed in the subchondral bone, reflected by a higher bone area fraction in the LC of the training group (90.8 ± 0.6%) compared to the resting group (85.3 ± 1.4%, P = 0.0010). Race training was associated with less bone resorption and more bone formation in the subchondral bone of highly loaded areas of the distal metacarpus limiting the replacement of fatigued bone. Periods of reduced intensity loading are important for facilitating subchondral bone repair in Thoroughbred racehorses.

Murray Valley encephalomyelitis in a horse.

A 5-year-old Thoroughbred mare presented with signs of severe pain and was taken to exploratory laparotomy based on suspicion of an acute abdominal lesion. A mild gastrointestinal lesion was discovered, but was considered disproportional to the severity of signs displayed. The mare was later euthanased because of intractable pain. Comprehensive postmortem examination, including polymerase chain reaction testing of central nervous system tissue samples, allowed a definitive diagnosis of Murray Valley encephalomyelitis to be made. This case demonstrates the variability of clinical presentations in horses infected with Murray Valley encephalitis virus.

Temperature-dependent developmental variation in lobster muscle myosin heavy chain isoforms.

The temperature- and developmental-regulation of myosin heavy chain (MyHC) expression and primary sequence was investigated in the abdominal musculature of developing Homarus gammarus larvae acclimated to 10, 14 and 19+/-1 degrees C. MyHC loop 1 (ATP binding) and loop 2 (actin binding) regions were sequenced and compared. The deduced amino acid sequence of MyHC loop 1 showed a development-related increase in net charge from +1 to +2 between larval stages 1 and 2, which was not temperature-dependent. In post-settled stage 9 larvae, minor shifts in amino acid sequence occurred at 19 degrees C, and corresponded to a significant up-regulation of fast myosin mRNA expression. However, no temperature-specific loop 1 isoforms were detected. The deduced amino acid sequence of MyHC loop 2 was not affected by temperature, and the net charge remained +4 throughout development. These findings contrast to previous studies using the common carp, in which temperature-specific MyHC isoform genes were expressed in response to disparate thermal regimes. This raises the question as to whether arthropods do not express specific temperature isoforms but instead rely on shifts in fibre type to accommodate alterations in thermal environment.

Comparison of the variable loop regions of myosin heavy chain genes from Antarctic and temperate isopods.

The evolutionary adaptations of functional genes to life at low temperatures are not well characterised in marine and fresh water invertebrates. Temperature has been shown to affect the functional characteristics of fish muscles, with changes in the velocity of shortening and ATPase activity being associated with myosin heavy chain (MyHC) isoform composition and the structure of the surface loop regions. Two PCR products spanning loops 1 and 2 of a MyHC gene from an Antarctic isopod (Glyptonotus antarcticus) were sequenced and compared with those of a temperate isopod (Idotea resecata), slow and fast fibres from lobster (Homarus gammarus) and a cold water amphipod (Eulimnogammarus verrucosus), revealing specific differences between the species, possibly related to fibre type and habitat temperature. The loop 2 region from G. antarcticus myosin was cloned and used for Northern analysis of total RNA from the other species. The cloned myosin cDNA hybridised specifically to a 6.6-kb transcript, in G. antarcticus muscle. In contrast, cDNA probes for lobster slow myosin and actin hybridised to muscle RNA from all species, demonstrating that a distinct MyHC isoform is expressed in the Antarctic isopod, as opposed to the temperate species. The inter- and intra-specific sequence differences in loop 2 region suggest that this may be a site for muscle adaptation to enable function at the low temperatures found in the Southern Ocean.

Initial treatment outcomes in chronic sixth nerve palsy.

INTRODUCTION: We conducted a prospective multi-center, nonrandomized, data-collection study of patients with chronic sixth cranial nerve palsy. We evaluated success rates with conservative nonsurgical management, botulinum toxin (botox) treatment, strabismus surgery, and a combination of botox treatment and surgery. METHODS: All members of the American Association for Pediatric Ophthalmology and Strabismus and the North American Neuro-Ophthalmology Society were invited to enroll patients with sixth nerve palsy or paresis of more than 6 months duration over a 2-year period (between March 1998 and February 2000). The botox and surgical groups received intervention within 3 months of enrollment. Success at 6 months from enrollment was defined as absence of diplopia in primary position and no more than 10 prism diopters (pd) distance esotropia in primary position. Patients with no follow-up were excluded. RESULTS: Fifty-six eligible patients were enrolled by 33 investigators. Eighteen (32%) were traumatic in etiology, 15 (27%) were unknown (including presumed hypertensive), 14 (25%) were neoplastic, 2 (4%) were diabetic, and 7 (13%) were other. Twenty (35%) were managed conservatively without surgery, 10 (18%) with botox treatment, 19 (33%) with surgery, and 8 (14%) with a combination of botox treatment and surgery. Success at 6 months from enrollment was 15% in the conservatively managed cases, 10% with botox alone, 39% with surgery alone, and 25% with a combination of botox and surgery. CONCLUSIONS: This study demonstrates that management of chronic sixth nerve palsy and paresis remains challenging. Spontaneous recovery occurs but is uncommon. Botox treatment alone was rarely successful, and a single surgical procedure had a lower-than-expected success rate. Care should be taken in directly comparing success rates between treatment groups because of bias in patient selection.

Computerized method of visual acuity testing: adaptation of the amblyopia treatment study visual acuity testing protocol.

PURPOSE: To report a computerized method for determining visual acuity in children using the Amblyopia Treatment Study visual acuity testing protocol. METHODS: A computerized visual acuity tester was developed that uses a programmed handheld device that uses the Palm operating system (Palm, Inc, Santa Clara, California). The handheld device communicates with a personal computer running a Linux operating system and 17-inch monitor. At a test distance of 3 m, single letters can be displayed from 20/800 to 20/12. A C program on the handheld device runs the Amblyopia Treatment Study visual acuity testing protocol. Using this method, visual acuity was tested in both the right and left eyes, and then the testing was repeated in 156 children age 3 to 7 years at four clinical sites. RESULTS: Test-retest reliability was high (r =.92 and 0.95 for and right and left eyes, respectively), with 88% of right eye retests and 94% of left eye retests within 0.1 logarithm of minimal angle of resolution (logMAR) units of the initial test. The 95% confidence interval for an acuity score was calculated to be the score +/- 0.13 logMAR units. For a change between two acuity scores, the 95% confidence interval was the difference +/- 0.19 logMAR units. CONCLUSIONS: We have developed a computerized method for measurement of visual acuity. Automation of the Amblyopia Treatment Study visual acuity testing protocol is an effective method of testing visual acuity in children 3 to 7 years of age.

Amblyopia. Current clinical studies.

Over the next two years, results from several multi-center amblyopia treatment studies will become available. These data may have a profound influence on our approach to treating this condition. This is indeed an exciting time to be taking care of children with amblyopia, as we anticipate the results of these studies.

The amblyopia treatment study visual acuity testing protocol.

OBJECTIVE: To evaluate the reliability of a new visual acuity testing protocol for children using isolated surrounded HOTV optotypes. METHODS: After initial pilot testing and modification, the protocol was evaluated using the Baylor-Video Acuity Tester (BVAT) to present isolated surrounded HOTV optotypes. At 6 sites, the protocol was evaluated for testability in 178 children aged 2 to 7 years and for reliability in a subset of 88 children. Twenty-eight percent of the 178 children were classified as having amblyopia. RESULTS: Using the modified protocol, testability ranged from 24% in 2-year-olds to 96% in 5- to 7-year-olds. Test-retest reliability was high (r = 0.82), with 93% of retest scores within 0.1 logMAR unit of the initial test score. The 95% confidence interval for an acuity score was calculated to be the score +/-0.125 logMAR unit. For a change between 2 acuity scores, the 95% confidence interval was the difference +/-0.18 logMAR unit. CONCLUSIONS: The visual acuity protocol had a high level of testability in 3- to 7-year-olds and excellent test-retest reliability. The protocol has been incorporated into the multicenter Amblyopia Treatment Study and has wide potential application for standardizing visual acuity testing in children.

The Amblyopia Treatment Index.

OBJECTIVE: To develop a questionnaire to assess the acceptability of amblyopia treatment and its effect on the child and family. METHODS: A 20-item parental survey was developed and pilot tested on 64 subjects, aged 3 to 6 years, participating in the Amblyopia Treatment Study, a randomized trial comparing patching and atropine as treatments for moderate amblyopia. The survey was administered after 4 weeks of treatment. A descriptive item analysis and an internal consistency reliability analysis were performed. RESULTS: Nineteen of the 20 items demonstrated adequate variability as evidenced by the frequency distributions for item responses. Only 4 (<1%) of 1280 possible item responses were missing, one each by 4 different respondents. Factor analysis identified 3 treatment-related factors--"adverse effects," "compliance," and "social stigma"--among 11 of the 20 items. The internal-consistency reliability alpha for the 5-item adverse effects subscale was 0.82, the 4-item compliance subscale alpha was 0.81, and the 2-item social stigma subscale alpha was 0.84. CONCLUSIONS: The Amblyopia Treatment Index appears to be a useful instrument for assessing the impact of amblyopia treatment in 3- to 6-year-old children.

Predictors of nonrecovery in acute traumatic sixth nerve palsy and paresis.

PURPOSE: To evaluate whether nonrecovery from acute traumatic sixth nerve palsy could be predicted from demographic factors or palsy characteristics. DESIGN: Prospective, observational case series SETTING: Multicenter (academic and private practices). OUTCOME MEASURE: Nonrecovery, defined as the presence of diplopia in primary position or more than 10 prism diopters of distance esotropia in primary position at 6 months after onset. METHODS: Using data from a previously described cohort of 84 eligible patients with acute traumatic sixth nerve palsy, we performed multivariate analyses of demographic factors and palsy characteristics. RESULTS: Nonrecovery at 6 months after onset was associated with a complete palsy (adjusted risk ratio, 9.11; 95% confidence interval [CI], 2.77-14.84) and with a bilateral palsy or paresis (adjusted risk ratio, 2.53; 95% CI, 0.98-4.29). The choice of conservative management (observation, prism, or patch) versus acute injection of Botulinum toxin (within 3 months of injury) did not influence final recovery. CONCLUSIONS: In acute traumatic sixth nerve palsy or paresis, failure to recover by 6 months after onset was associated independently with inability to abduct past midline at presentation and bilaterality. Although the overall recovery rate is high in acute traumatic sixth nerve palsy or paresis, a complete or bilateral case has a poor prognosis and is more likely to need strabismus surgery.

Photographic and clinical techniques for outcome assessment in sixth nerve palsy.

PURPOSE: There are few data on the reproducibility of clinical assessment of ductions and alignment. We evaluated photographic methods that may be used for masked outcome determination in a clinical trial and compared them with clinical measures. DESIGN: Interexaminer reliability study. PARTICIPANTS: Twenty-three patients with unilateral sixth nerve palsy and three control participants were clinically evaluated by two masked examiners. MAIN OUTCOME MEASURES: Abduction deficit was graded as 0 to -5. Simultaneous prism and cover tests (SPCT) and alternate cover tests (ACT) were performed at distance and near fixation. Photographs were taken of abduction and distance alignment by each examiner. The photographs were evaluated by a third masked reader, who assigned abduction grade, measured absolute abduction (mm) and relative abduction (%), and calculated alignment in prism diopters (pd). Agreement was evaluated by calculating intraclass correlation coefficients (r(i)), weighted kappa statistics (kappa), and Spearman rank correlation coefficients (r(S)). RESULTS: There was excellent agreement between the two clinicians in clinical abduction deficit (kappa = 0.86) SPCT and ACT at distance and near (r(i) 0.94-0.96), between the clinical grade and masked photographic grade (kappa = 0.83), and between the two sets of photographs for absolute abduction and relative abduction (r(i) = 0.98 and 0.97). Both photographic measures of abduction correlated well with the clinical grade (r(S) = -0.96 for each). Measurements of alignment from photographs correlated with clinical SPCT measurement (r(i) = 0.88), but had a lower level of absolute agreement (38% within 5 pd) than between two independent SPCT measurements (96% within 5 pd). CONCLUSIONS: The excellent interexaminer agreement of our new photographic abduction assessment and of masked clinical measures suggest that these methods would be useful in clinical trials. In contrast, our simple method of photographic assessment of alignment lacks excellent agreement with the clinical assessment. These data are important in planning clinical trials in strabismus.

Postnatal growth retardation exacerbates acidosis-induced retinopathy in the neonatal rat.

PURPOSE: We have previously described a metabolic acidosis-induced retinopathy in the neonatal rat, similar to retinopathy of prematurity (ROP). We also have reported exacerbation of oxygen-induced retinopathy by postnatal growth retardation, produced by raising newborn rats in 'expanded' litters. In the present study, we investigated the effect of postnatal growth retardation on the incidence and severity of acidosis-induced retinopathy. METHODS: 100 newborn Sprague-Dawley rats were randomly assigned to two expanded litters of 25 pups each and five standard control litters of 10 pups each. All rats were gavaged with 10 mM/kg NH(4)Cl twice daily from days two to seven. Following five days of recovery, retinal vasculature was assessed using ADPase staining, light microscopy, and computer-assisted image analysis. The presence of neovascularization (NV), severity of NV (clock hours), and vascularized retinal areas, were evaluated in a masked manner. RESULTS: NV occurred in 52% of rats in expanded litters versus 18% of rats in standard control litters (p = 0.005). Postnatal growth retardation of pups in expanded litters was confirmed by comparing total body weight of pups raised in expanded and standard control litters (10.8g vs 13.4g on day 8, p < 0.001; 20.8g vs 25.2g on day 13, p = 0.002). CONCLUSIONS: Postnatal growth retardation increases the incidence of acidosis-induced retinopathy in the neonatal rat. Our study provides further evidence that postnatal growth retardation is a risk factor for preretinal neovascularization in immature retinae and is consistent with the clinical observation that the smallest and sickest premature infants are more likely to suffer from ROP.

Age-appropriate HIV prevention messages for older adults: findings from focus groups in New York State.

The Emerging Issues Committee of the New York State HIV Prevention Planning Group identified that prevention messages were not including persons 50 and older and that 15 percent of the newly reported AIDS cases in 1997 in New York were in this age group. Recognizing that there may be unique needs in targeting prevention messages for this age group, a consultant conducted five focus groups throughout the state to speak with people to determine what they identified as unique themes related to HIV prevention for this age group.

Preretinal neovascularization associated with acetazolamide-induced systemic acidosis in the neonatal rat.

PURPOSE: NH4Cl gavage in the neonatal rat produces a metabolic acidosis-induced retinopathy which serves as a model for retinopathy of prematurity (ROP). Acetazolamide induces a metabolic acidosis via an alternative biochemical mechanism (bicarbonate loss versus hydrogen ion load). In the present study, the following hypothesis was tested: acetazolamide-induced acidosis is associated with preretinal neovascularization in the neonatal rat. METHODS: All studies used newborn Sprague-Dawley rats raised in expanded litters of 25. Arterial blood pH was measured to determine the level of acidosis induced by intraperitoneal (IP) acetazolamide (50 or 200 mg/kg) or saline. In a separate retinopathy study, newborn rats (n = 75) were randomized to either IP acetazolamide, 50 mg/kg (low-dose), or IP saline twice daily from days 2 to 7. After 5 days of recovery, retinal vasculature was assessed using ADPase staining and light microscopy. The presence and severity (clock hours) of neovascularization were assessed by three masked observers. In an additional retinopathy study, newborn rats (n = 100) were randomized to either IP acetazolamide, 200 mg/kg (high-dose), or IP saline twice daily from days 2 to 7. After 5 days of recovery, the retinas were similarly analyzed. RESULTS: Neovascularization occurred in 59% of rats receiving high-dose acetazolamide (200 mg/kg). High-dose acetazolamide produced a severe acidosis (pH 7.13 +/- 0.06) during drug delivery. Low-dose acetazolamide (50 mg/kg) produced a pH (7.22 +/- 0.07) that was intermediate between high-dose (200 mg/kg) acetazolamide (P < 0.001) and saline controls (7.42 +/- 0.06, P < 0.001); however, neither low-dose acetazolamide nor saline induced preretinal neovascularization. CONCLUSIONS: Acidosis induced by high-dose acetazolamide, independent of hyperoxemia or hypoxemia, is associated with preretinal neovascularization in the neonatal rat. Induction of neovascularization appears to depend on a critical threshold of acidosis severity. This study further supports a proposed independent role for acidosis in the pathogenesis of ROP.

Norian craniofacial repair system bone cement for the repair of craniofacial skeletal defects.

PURPOSE: To describe the use of the Norian Craniofacial Repair System (CRS) calcium phosphate bone cement in the restoration of craniofacial skeletal defects. METHODS: Consecutive case series. RESULTS: Calcium phosphate bone cement was used to repair craniofacial skeletal defects in three patients. Indications included repair of a posttraumatic orbital floor defect causing hypo-ophthalmos, reconstruction of frontal craniotomy and temporalis muscle donor sites in a patient who had undergone resection of an invasive squamous cell carcinoma, and augmentation of a post-traumatic anterior maxillary skeletal defect. The primary outcome measure was the restoration of bony volume and support. The use of calcium phosphate bone cement in these patients was effective and without complications. CONCLUSIONS: Norian CRS calcium phosphate bone cement is useful in the repair of craniofacial skeletal defects.

Botulinum toxin treatment versus conservative management in acute traumatic sixth nerve palsy or paresis.

PURPOSE: Botulinum toxin (BTX), injected into the ipsilateral medial rectus muscle, has been advocated for the management of acute traumatic sixth nerve palsy or paresis. We conducted a multicenter, nonrandomized, data collection study to evaluate recovery rates of patients treated with either conservative measures or BTX. METHODS: All members of the American Association for Pediatric Ophthalmology and Strabismus and the North American Neuro-Ophthalmology Society were invited to enroll patients with acute traumatic sixth nerve palsy or paresis during a 2-year period (between March 1996 and February 1998). The BTX group was defined as patients who received a BTX injection within 3 months of injury. Recovery at 6 months from injury was defined as absence of diplopia in the primary position and a distance esotropia of no more than 10 PD in the primary position. Nonrecovered patients with less than 6 months of follow-up (n = 15) were excluded. RESULTS: Eighty-four eligible patients were enrolled by 46 investigators. Sixty-two patients (74%) were treated conservatively and 22 (26%) with BTX. Sixty-two patients (74%) had unilateral palsy, and 22 (26%) had bilateral palsy. Recovery rates were similar between BTX and conservatively treated patients (overall: 73% vs 71%, P = 1.0; unilateral: 81% vs 83%, P = 1.0; bilateral: 50% vs 38%, P = 0.66, respectively). CONCLUSIONS: In this prospective multicenter study of acute traumatic sixth nerve palsy or paresis, patients treated with either BTX or conservative measures had similar high recovery rates.

Neovascularization grading methods in a rat model of retinopathy of prematurity.

PURPOSE: The method of counting cell nuclei above the internal limiting membrane in histologic sections is considered the standard when quantifying neovascularization (NV) in rodent oxygen-induced retinopathy (OIR). An alternative, more rapid method of counting clock hours in flatmounted adenosine diphosphatase (ADPase)-stained rat retinas is analogous to clinically scoring retinopathy of prematurity (ROP). In the present study, the validity of counting clock hours was evaluated by a direct comparison of these techniques. The intereye correlation of NV score and retinal vascular area were also studied. METHODS: Newborn Sprague-Dawley rats were exposed to cycles of O2 (80-10%) for 7 days, followed by 5 days of room air recovery. Preretinal NV was quantified by three masked observers counting clock hours in flatmounted ADPase-stained retinas of both eyes. Retinal vascular and total retinal areas were calculated using computer-assisted analysis. Representative retinas that had been scored positive (n = 10) and negative (n = 3) for NV and room air control retinas (n = 3) were embedded in paraffin. Each entire peripheral retinal quadrant was serially sectioned at 6 microm and stained with hematoxylin and eosin. Nuclei above the internal limiting membrane were then counted in a masked manner. The total number of nuclei counted per retina was defined as the nucleus count (704-938 sections per retina; 12,900 sections). Correlations were evaluated using Spearman rank coefficients. RESULTS: The nucleus count was 0 to 44 in room air control retinas, 0 to 40 in negative OIR retinas, and 250 to 5634 in positive OIR retinas. The nucleus count was highly correlated with the clock hour score (r(s) = 0.95, P = 0.0001). For the paired retinas, there was a significant correlation between right and left eyes in the severity of NV (clock hours; r(s) = 0.76, P = 0.0001) and the ratio of retinal vascular area to total retinal area (r(s) = 0.81, P = 0.0001). CONCLUSIONS: The more rapid method of counting clock hours in flatmounted ADPase-stained retinas is valid for quantifying NV in rat models of ROP. Incidence and severity of NV and vascularized areas were similar between left and right eyes, which permits the use of paired retinas for complementary research techniques.