Jonathan M. Holmes

Improved stereoacuity: An indication for unilateral cataract surgery

Purpose: To determine whether stereoacuity is an objective indicator of functional improvement following unilateral cataract surgery. Setting: Department of Ophthalmology, Loyola University Chicago, Maywood, Illinois. Methods: Seventeen consecutive patients with unilateral cataracts (8 pseudophakic, 9 phakic in contralateral eye) were studied prospectively. Best corrected distance visual acuity in the eye with cataract ranged from 20/40 to 20/400. Distance acuity in the eye without cataract was 20/20 or 20/25. All patients had cataract surgery with posterior chamber intraocular lens implantation. Stereoacuity was measured preoperatively and postoperatively; at near by Titmus test (TT) and at distance by B‐VAT BVS random dot E (BVRDE) and contour circles (BVC). Nonparametric Spearman rank correlation and Wilcoxon rank tests were used for analysis. Results: Preoperatively, reduced near visual acuity in the cataractous eye correlated with reduced near stereo (TT), r = .6, P = .01. Postoperatively, near stereoacuity improved in all but one patient, from a median of 200 seconds of arc (sec arc) to 40 sec arc (P = .004); distance stereoacuity improved in all but two patients from a median of unrecordable to 120 sec arc (BVC) (P = .006). Preoperatively none of the patients could see the largest distance BVRDE target, whereas postoperatively 4 of 17 had BVRDE stereoacuity of 120 to 240 sec arc (P = .06). Conclusions: Patients with unilateral cataracts have reduced stereoacuity, correlating with their reduced monocular visual acuity. In this study, distance and near stereoacuity improved postoperatively. Decreased stereoacuity may provide an indication for unilateral cataract surgery.

The effect of litter size on normal retinal vascular development in the neonatal rat

Many animal models of retinal disease use the neonatal rat. Raising rat pups in large litters has been shown to result in postnatal growth retardation. We investigated the effect of litter size on the normal postnatal vascularization of the neonatal rat retina. Sixty-six newborn rat pups were divided among 5 nursing mothers into 3 small litters (n = 10) and 2 large litters (n = 18). On day 6 of life the rats were sacrificed and total retinal and vascularized retinal areas analyzed. The total retinal area was reduced in the rats raised in larger litters (28.6 mm2 vs. 25.9 mm2 p < 0.001) but there was a more pronounced reduction in vascularized retinal area (67% vascularized vs. 54% vascularized, p < 0.001). Postnatal vascularization of the normal rat retina may be influenced by litter size.

The effect of raised inspired carbon dioxide on developing rat retinal vasculature exposed to elevated oxygen

Hyperoxia is a risk factor for retinopathy of prematurity (ROP), a blinding disease in infants. However, ROP develops in human infants without raised arterial oxygen levels, such as in cyanotic congenital heart disease. In these infants raised pCO2 may be a risk factor. We investigated the effect of inspired CO2 on oxygen induced retinopathy in the rat. 56 newborn Sprague-Dawley rats were exposed to high cyclical O2 for seven days. In a control group, 27 rats were exposed to negligible CO2 by the use of soda lime. In the high CO2 group, 29 rats were exposed to elevated CO2 by omitting soda lime from their chambers. Rats in both groups had a recovery period of three days in room air following cyclical O2 exposure. On the eleventh day all rats were sacrificed after intracardiac injections of fluorescein under deep anesthesia and the retinae were dissected and flat mounted for fluorescent microscopy. The ratio of vascularized:total retinal area was calculated using computer assisted image analysis. In the high CO2 group 62% +/- 7% SD of the retina was vascularized vs. 81% +/- 7% in low CO2 group (p < 0.001). Elevated inspired CO2 results in pronounced retardation of retinal vascular development in neonatal rats exposed to fluctuating raised oxygen.

Randomized clinical trial of surfactant prophylaxis in retinopathy of prematurity

Prophylactic lung surfactant is commonly used to reduce the severity of neonatal respiratory distress syndrome in premature infants. There is disagreement in the literature regarding the effect of prophylactic lung surfactant on the incidence of retinopathy of prematurity (ROP). Sixty-four infants, gestational age 23 to 32 weeks, birth weight 610 to 1250 g, were randomized to receive either intratracheal bovine surfactant prophylaxis or air control, at our institution, as part of a national double-masked multicenter trial. Forty-eight of these infants survived and underwent complete ophthalmologic examinations by a single masked examiner. ROP data were gathered retrospectively. ROP developed in 19 of the 23 (83%) who received surfactant and 15 of the 25 (60%) controls (P = .1). Analysis of the worst stage of ROP for each infant also revealed no difference between the surfactant and control groups (P = .4). Our retrospective analysis of ROP data in a prospective double-masked randomized study revealed no significant effect of surfactant on the incidence or severity of ROP.

Vernier acuity cards: a practical method for measuring Vernier acuity in infants

The feasibility of a practical preferential looking technique, similar to Teller acuity cards, was investigated for the assessment of vernier acuity in preverbal infants. Forty-two infants ages 1 to 13 months were tested with cards having vernier offsets of 2 to 64 minutes of arc and spatial frequencies of 0.25 to 2.0 cycles per degree. All infants showed a robust preferential looking response to the largest vernier offsets. Vernier thresholds decreased with age from 64 minutes of arc at 1 month to 4 minutes of arc at 13 months. Smaller vernier offsets were more readily detectable when embedded in higher spatial frequency gratings. Vernier acuity can be assessed in preverbal infants using a preferential looking technique similar to that employed with the Teller acuity cards. Vernier acuity is known to be more sensitive to amblyopia than grating acuity; therefore, this technique may prove useful in the assessment of amblyopia.

The kinetics of anterior chamber ofloxacin penetration

Thirty-five patients received topical ofloxacin 0.3% before routine cataract surgery. Ofloxacin was administered one drop every 2 h for five doses 1 day before surgery and one drop every 5 min for five doses immediately before surgery. Aqueous sampling was performed at variable periods 30–150 min after the last topical dose. The mean aqueous ofloxacin concentration was 793 ± 516 ng/ml (range, 143–2,400 ng/ml). A significant correlation between time from last dose and aqueous humor concentration was found (r = 0.39, p = 0.025). The mean ofloxacin concentration was greater in those patients who received their last dose > 1 h before aqueous aspiration (957 ± 559 ng/ml versus 554 ± 338 ng/ml, p = 0.02). From a best-fit scatter plot of concentration versus time, the maximal aqueous concentration of 1,000 ng/ml occurs at ∼2 h after topical administration.

Effects of topical suprofen and flurbiprofen on the miosis produced by anterior chamber irrigation with cholinergic agonists

ABSTRACT Pretreatment with topical nonsteroidal anti‐inflammatory drugs is common practice to maintain maximal pupil dilation for cataract surgery. Most surgeons also inject a cholinergic agent intracamerally for miosis after intraocular lens insertion. We evaluated the effects of topical suprofen and flurbiprofen on the miosis induced by anterior chamber irrigation with either acetylcholine or carbachol. One eye of 30 pigmented rabbits was dilated with cyclopentolate HCl and phenylephrine HC1. Three groups, each composed of ten eyes, received flurbiprofen, suprofen, or a control. In each group, five eyes received acetylcholine by anterior chamber irrigation and five received carbachol. Pupil diameters were measured with calipers before and five minutes after irrigation by an observer unaware of the treatment regimen. Irides irrigated with carbachol constricted less than those irrigated with acetylcholine (P = .016). In anterior chambers irrigated with carbachol, suprofen was associated with less miosis than either tears (P = .005) or flurbiprofen (P = .0091; however, if the infusion was performed with acetylcholine, no differences between the three groups were noted (P = .44).

The effect of preoperative flurbiprofen on miosis produced by acetylcholine during cataract surgery

Sustained pupillary dilation during cataract surgery may be achieved with preoperative noncorticosteroidal anti-inflammatory agents such as flurbiprofen. However, these agents may interfere with miosis after injection of acetylcholine. Thirty patients for extracapsular cataract extraction were randomly assigned in a double-masked fashion to receive either a placebo or preoperative 0.03% flurbiprofen every 30 minutes for four doses. All patients also received three doses of 2.5% phenylephrine and 2% cyclopentolate. Pupillary diameter was measured the day before surgery, immediately before the surgical incision, immediately before and five minutes after acetylcholine injection, and the morning after surgery. The flurbiprofen group had a larger mean pupillary diameter before injection of acetylcholine (P less than .001), five minutes after acetylcholine (P less than .001), and on the first postoperative day (P less than .005).

Assessment of visual acuity in children with trisomy 18

Although 90% of children with trisomy 18 (Edwards syndrome) die in the first year of life, a small proportion survive into the second and third decade. Many do not have associated ocular abnormalities that might affect vision. Measurable visual acuity has not been reported in these profoundly developmentally delayed individuals. Five children with trisomy 18, aged six months to eight years, underwent complete eye examination including assessment of binocular grating acuity with Teller acuity cards and assessment of binocular vernier acuity with vernier cards. All children were nonverbal with profound developmental delay. Binocular grating acuity ranged from 0.9 cycles per degree (cpd) to 2.2 cpd. This represents a reduction of 1.9 to 5.1 octaves (mean 3.5 octaves, SD 1.3 octaves) compared to age matched norms. None of the children responded to any of the vernier offsets, including the largest of 64 minutes of arc. All children with trisomy 18 demonstrated a measurable grating acuity that was well below normal for age, consistent with profound developmental delay.

Recovery of phorias following monocular occlusion

Fourteen nonstrabismic volunteers were monocularly patched for 2 and 24 hours in separate experiments. Horizontal and vertical phorias were measured at 6 m and 30 cm, at 30-second intervals, for at least 30 minutes, following removal of the patch. After 24 hours of monocular occlusion, the initial change from baseline at 6 m ranged from 9.5 prism diopters exo to 7 delta eso and 6.5 delta hyper to 3 delta hypo. At 30 cm, the initial change ranged from 7.5 delta exo to 4 delta eso and 1 delta hyper to 1 delta hypo. In all but three subjects, phorias returned to within 2 delta of baseline by 3 minutes, and in all subjects by 25 minutes. After 2 hours of monocular occlusion, the range of initial change from baseline was similar to 24 hours of occlusion, but all phorias returned to within 2 delta of baseline by 2.5 minutes. Therefore, we suggest that ocular alignment should not be routinely measured within 3 minutes of removing a patch. If patched for 24 hours, a few individuals will require up to 25 minutes for stabilization of their deviation. Further studies might address these effects in patients with subnormal fusion and stereopsis.