Potential Acuity Research Articles

Visual function in breast-fed term infants weaned to formula with or without long-chain polyunsaturates at 4 to 6 months: A randomized clinical trial

Objective Breast-fed infants receive docosahexaenoic acid (DHA) and arachidonic acid (ARA) in their diet. Upon weaning, infants lose this dietary source of long-chain polyunsaturates because many commercial formulas do not contain these important constituents for neural membrane biogenesis. We evaluated the benefits of postweaning dietary supplementation of DHA + ARA on visual maturation. Study design Healthy term infants (n = 61) were breast-fed to 4 to 6 months, then were randomly assigned to commercial formula or formula supplemented with DHA (0.36%) + ARA (0.72%). Measurements of red blood cell (RBC) fatty acids, visually evoked potential (VEP) acuity, and stereoacuity were done before and after weaning. Results At 1 year of age, RBC-DHA in the commercial formula-fed group was reduced by 50% from the weaning level, whereas there was a 24% increase in the DHA + ARA-supplemented group. The primary outcome measure, VEP acuity, was significantly more mature in supplemented infants at 1 year of age. Elevated RBC-DHA levels were associated with more mature VEP acuity. There were no significant diet-related differences in stereoacuity. Conclusions These data extend through the first year of life the critical period in which a dietary supply of DHA and ARA can contribute in optimizing visual development in term infants. (J Pediatr 2003;142:669-77)

Quality of vision after laser in situ keratomileusis: Influence of dioptric correction and pupil size on visual function

Purpose To determine the influence of pupil size and the amount of ablation on visual performance and on the patient’s perception of glare or halo after laser in situ keratomileusis (LASIK). Setting Department of Ophthalmology, National Taiwan University Hospital, Taipei, Taiwan. Methods This study included a random cross-section of 50 eyes of 32 patients with “uniform” topography at least 6 months after LASIK and 51 eyes of 28 patients who had normal corneas. Each LASIK patient completed a survey rating adverse effects such as symptoms of night glare and halo. Pupil diameter and best spectacle-corrected visual acuity (BSCVA) were measured under photopic and scotopic conditions. Contrast sensitivity was measured with an MCT 8000 (Vistech Consultants, Inc.) under daytime and nighttime and with night glare conditions. A Technomed C-scan (Technomed Technology) was performed, and the potential corneal visual acuity (PCVA) was calculated after the settings for the pupil size were changed to the values measured under bright-light or dim-light conditions. Results No significant difference was found between the post-LASIK and normal cornea groups in photopic or scotopic BSCVA ( P>.05). In cases of moderate myopia, the post-LASIK group had decreased PCVA and contrast sensitivity ( P<.05). In cases of high myopia, the post-LASIK group had decreased contrast sensitivity at spatial frequencies of 1.5 cycles per degree (cpd) under daytime conditions and 3 cpd under nighttime conditions (P<.05). Glare or halo symptoms did not correlate with scotopic BSCVA, PCVA, or nighttime contrast sensitivity with or without glare ( P>.05). Pupil size was not significantly correlated with glare or halo symptoms, BSCVA, or contrast sensitivity under scotopic or photopic conditions ( P>.05). In moderate myopia, the amount of attempted correction of the spherical equivalent (SE) was correlated with halo symptoms ( P<.05; adjusted r 2 = 0.17). In high myopia, the amount of attempted astigmatism correction was correlated with the development of glare symptoms ( P<.05; adjusted r 2 = 0.16). Conclusions There was a decrease in contrast sensitivity in post-LASIK eyes. The amount of attempted correction of the SE or astigmatism was correlated with the development of glare and halo symptoms. Pupil size was not significantly correlated with glare or halo symptoms, BSCVA, or contrast sensitivity in post-LASIK patients with “uniform” topography who had scotopic pupils not larger than 7.0 mm.

Comparison of Subjective Visual Acuity With Visual Acuity Predicted From C-scan Topography

To compare the capability of objective measures of visual acuity (potential visual acuity from C-scan) to predict subjective visual acuity (best spectacle-corrected visual acuity [BSCVA]). Patients with BSCVA > or = 20/20 were enrolled in four groups (Group 1: normal [33 eyes]; Group 2: < -7.00 D myopia [43 eyes]; Group 3: > or = -7.00 D myopia [28 eyes]; Group 4: At least 1 month after LASIK [93 eyes]). Videokeratography was performed with the ray tracing Technomed C-scan. The potential visual acuity from C-scan was obtained with pupils undilated and intact precorneal tear films. All visual acuity was recorded in logMAR, and the significance of differences between acuities was assessed with a one-way ANOVA test. The potential visual acuity from C-scan ray tracing of normal and myopic eyes in response to both photopic and mesopic stimuli did not differ. In a given eye, the potential visual acuity from C-scan ray tracing was better than BSCVA, and the difference was statistically significant. Although the potential visual acuity from C-scan of postoperative LASIK eyes in response to photopic stimuli was the same, it decreased under mesopic conditions. Potential visual acuity from C-scan overestimates subjective visual acuity due to the inadequate assumptions in ray tracing or individual retinal resolution ability. In addition, the potential visual acuity from C-scan ray tracing varies with pupil diameter in different illumination.

Effect of artificial tears on corneal surface regularity, contrast sensitivity, and glare disability in dry eyes

Objective To investigate the effects of artificial tears on corneal surface regularity and visual function in dry eyes. Design Nonrandomized, comparative trial. Participants Forty patients (40 eyes) with dry eyes with (group 1, n = 15 eyes) or without (group 2, n = 25 eyes) punctate epithelial keratopathy and a normal control group of 20 individuals (20 eyes) with no ocular abnormalities (group 3). Methods In both dry and normal eyes, the surface regularity index (SRI), surface asymmetry index (SAI), and potential visual acuity (PVA) were measured by computer-assisted videokeratography (TMS-1; Computed Anatomy, New York, NY). Spatial-contrast sensitivity and glare disability were also measured before and 1 minute after instillation of artificial tears. Main outcome measures Differences in SRI, SAI, PVA, spatial-contrast sensitivity, and glare disability between groups, before instillation of tears, and within groups, after instillation of tears. Results Compared with group 3, eyes in group 1 had significantly worse SRI, SAI, PVA, and contrast sensitivity (incomplete glare disability data precluded analysis) before instillation of artificial tears. Differences in corneal surface regularity and visual function between groups 2 and 3 were not significant except for a significantly increased glare disability at low spatial frequency (1.5 cycles per degree [cpd]) in group 2. Significant improvement in SRI, SAI, PVA, and contrast sensitivity were observed after instillation of artificial tears in group 1. In groups 2 and 3, the only significant changes were improvement in glare disability at 1.5 cpd and worsening of the SRI, respectively. Conclusions Tear film changes in dry eye patients may lead to irregularities on the corneal surfaces, causing glare disability. However, these changes may be too subtle in the early stages of dry eyes to be detected by corneal topography or contrast sensitivity measurements. Significant improvement in SRI, SAI, PVA, and contrast sensitivity were found after instillation of artificial tears in dry eyes with punctate epithelial keratopathy.

Visual acuity and retinal function in infant monkeys fed long-chain PUFA.

Previous randomized clinical trials suggest that supplementation of the human infant diet with up to 0.35% DHA may benefit visual development. The aim of the current study was to assess the impact of including arachidonic acid (AA) and a higher level of DHA in the postnatal monkey diet on visual development. Infant rhesus monkeys were fed either a control diet (2.0% alpha-linolenic acid as the sole n-3 FA) or a supplemented diet (1.0% DHA and 1.0% AA) from birth. Visual evoked potential acuity was measured at 3 mon of age. Rod and cone function were assessed in terms of parameters describing phototransduction. Electroretinogram (ERG) amplitudes and implicit times were recorded over a wide intensity range (-2.2 to 4.0 log scot td-sec) and assessed in terms of intensity response functions. Plasma DHA and AA were significantly increased (P < 0.001) in the diet-supplemented monkeys compared with the control monkeys. There was an approximately equal effect of diet for the rod phototransduction parameters, sensitivity, and capacitance but in the opposite directions. Diet-supplemented monkeys had significantly shorter b-wave implicit times at low retinal illuminances (<-0.6 log scot td-sec). There were no significant effects of diet for visual acuity or the other 23 ERG parameters measured. The results suggest that supplementation of the infant monkey diet with 1.0% DHA and 1.0% AA neither harms nor provides substantial benefit to the development of visual acuity or retinal function in the first four postnatal months.

The Chirila Keratoprosthesis: phase I human clinical trial

Objective To undertake a preliminary safety and performance evaluation of an artificial cornea, the Chirila Keratoprosthesis, in human patients. Design A prospective, interventional case series. Participants Fourteen consecutive patients with blindness of corneal origin not treatable by repeated standard penetrating keratoplasty. Methods Keratoprostheses were manufactured and implanted. The patients, all with preoperative visual acuity of light perception to count fingers (CF), were followed clinically in adherence to a protocol. Main outcome measures Safety (keratoprosthesis retention, incidence of serious complications) and performance (visual acuity, comfort, appearance). Results Ninety-three percent of keratoprostheses were retained to the date of reporting, up to 2.5 years. One keratoprosthesis (7%) was removed in a manner that restored the patient’s preoperative condition. All but one patient maintained their preoperative level of visual acuity or improved on it, with most achieving their estimated full potential visual acuity, (range, count fingers – 20/20). Conclusions This keratoprosthesis is acceptably safe and has demonstrated an ability to restore vision in cases in which alternative management would have had a poor prognosis. More extensive trials are warranted.

The Effect of Artificial Tears on Corneal Surface Regularity in Patients with Sjögren Syndrome

Purpose: To evaluate the effect of artificial tears on the topographic parameters associated with corneal surface regularity in patients with Sjögren syndrome. Methods: A total of 38 eyes of 20 patients with Sjögren syndrome were evaluated prospectively. The mean age of the patients was 50.5 ± 15.3 years (range, 28–76). Corneal topography with the Topographic Modeling System (TMS-2, Tomey) was performed before and after the instillation of artificial tears. The surface regularity index (SRI), surface asymmetry index (SAI), potential visual acuity (PVA) and mean astigmatism were compared in dry eyes before and after the instillation of artificial tears. Results: Before the instillation of artificial tears SAI, SRI, PVA and mean antigmatism values were found to be 1.37 ± 1.47, 0.74 ± 0.42, 20/30.92 ± 20/8.12 and 1.53 ± 1.47 D, respectively. In corneal topography performed after the instillation of artificial tears SAI, SRI, PVA and mean astigmatism values were 0.71 ± 0.82, 0.43 ± 0.36, 20/25.92 ± 20/5.55 and 1.08 ± 1.18, respectively. When compared statistically, the SRI, SAI, and mean astigmatism all decreased significantly and the PVA improved (p = 0.0001). Conclusion: Irregular corneal surface in dry eye patients affects optical quality. The statistically significant improvement observed in SRI and SAI values after the instillation of artificial tears also improves the PVA that is especially related to SRI.

Topographic analysis of corneal regularity after penetrating keratoplasty.

To evaluate the accuracy of the Holladay Diagnostic Summary of the EyeSys Corneal Analysis System in predicting the corneal visual acuity potential in patients who have undergone penetrating keratoplasty (PKP). Astigmatism patterns, refractive and topographic astigmatism, best spectacle-corrected visual acuity (BSCVA), and hard contact lens (HCL) visual acuity of 54 patients were analyzed 3 months after PKP and compared with the Potential Corneal Acuity (PCA) value predicted by the Holladay Diagnostic Summary. Qualitative patterns of astigmatism (p = 0.01) and refractive (p = 0.002) and topographic (p = 0.0002) astigmatism were significantly correlated with PCA values. Using HCL visual acuities to correct the BSCVA (HCL-corrected BSCVA) for noncorneal causes of reduced vision, we found that the PCA values of 48.1% of the patients were within one line of the HCL-corrected BSCVA; 81.5% were within two lines; and 93.0% were within three lines. The Holladay PCA measurement may be useful in the postoperative evaluation of the optical quality of the central corneal surface in patients who have undergone PKP.

An expanded nystagmus acuity function: intra- and intersubject prediction of best-corrected visual acuity.

The Nystagmus Acuity Function (NAF) provides an objective measurement of the foveation characteristics of nystagmus waveforms and an assessment of potential visual acuity for subjects with congenital (CN) or latent/manifest latent (LMLN) nystagmus. It is based on the subjects' ability to maintain fixation within a physiologically based 'foveation window' of +/- 0.5 degrees and +/- 4.0 degrees/s. However, some subjects are incapable of controlling fixation well enough to remain within this window with duration sufficient for good foveation. To obtain a measure of the CN waveforms of these individuals, we are proposing an eXpanded Nystagmus Acuity Function (NAFX) that relaxes either the position limit, the velocity limit, or both. Data used in this study comes from 11 human subjects with CN (10 idiopathic and 1 with achiasma) and a Belgian sheepdog with achiasma. Visual acuity was tested with a standard Snellen chart and eye movements recorded with infrared oculography or scleral search coil. For the NAFX to be useful, it must not only be applicable for subjects who cannot maintain fixation within the standard limits of the NAF, but also must yield results equivalent to those obtained with the NAF when testing subjects who are capable of maintaining good fixation control. For the latter subjects, the amount of time when position and velocity fell within the expanded limits was measured, the standard deviations of the position and velocity during these times were calculated, and a tau-surface for the exponential function was generated to guarantee the equivalence between the NAF and the NAFX. We developed an automated NAFX equivalent to the original NAF. We demonstrated that equivalence in 10 subjects and the use of the NAFX on two additional (1 human and 1 canine) subjects who were incapable of maintaining fixation within the standard position and velocity limits. We demonstrated the effects of surgery and related the results to visual acuity. We found the results to be comparable to those seen when applying the NAF to subjects who had good fixation control. The NAFX can be determined for CN and LMLN subjects with poor control of fixation by extending the standard NAF position and/or velocity limits for foveation. The resulting function can be used along with the longest foveation domain (derived from the NAFX to measure breadth of a high-NAFX region) to identify the gaze or convergence angles with the best waveform and to predict the best-possible visual acuity that could be achieved with the reduction of their nystagmus.

Wavelet analysis for corneal topographic surface characterization

Purpose. To demonstrate a mathematical method for multi-scalar decomposition of discrete corneal topography height data into a space-scale space using wavelet analysis techniques, and to demonstrate the clinical applicability of these computations in the postkeratoplasty cornea. Methods. Fifty patients with either Fuchs' dystrophy (n = 20) or keratoconus (n = 30) were seen preoperatively, at 3 months, at 1 year (before suture removal) and again at 19 ± 3 months (after suture removal) following nonmechanical trephination with an excimer laser for penetrating keratoplasty. Patients were assessed using corneal topography analysis (TMS-1), subjective refraction, and best-corrected visual acuity (VA) at each interval. Two-dimensional biorthogonal wavelets with the order 6.8 at the scales j = 1–4 revealed the following parameters: root-mean square (RMSDEV) and mean absolute (MEANDEV) deviation and maximum absolute height of the peaks or pitches (MAXPEAK) relative to the reference surface specified with the approximation component of scale j = 4. RMSDEV was correlated with the VA at various follow-up intervals. The multiscalar basis components: roughness, waviness and form were separated and recovered from the wavelet soft thresholding techniques. Peaks and pits within the three-dimensional corneal surface topography were detected and localized using the wavelet hard thresholding techniques. Results. In patients with keratoconus, the RMSDEV and the MEANDEV increased from 4.31 ± 1.25 / 5.98 ± 1.88 µm pre-operatively to the 3 months follow-up (4.98 ± 1.41 / 6.92 ± 2.16 µm) and thereafter decreased continuously to the end of the follow-up (1.87 ± 0.63 / 2.63 ± 1.07 µm), whereas in Fuchs' dystrophy the respective values started at a higher preoperative level (6.36 ± 1.24 / 7.20 ± 2.64 µm) and decreased continuously over time (2.73 ± 1.10 / 3.71 ± 1.05 µm after suture removal). In the keratoconus group, the MAXPEAK was increased at the 3 month postoperative exam (8.78 ± 2.29 µm) when compared to the preoperative value (6.55 ± 2.56 µm); however, it decreased again and returned to the preoperative level after one year (6.34 ± 2.12 µm after suture removal). In Fuchs' dystrophy, the MAXPEAK was unchanged preoperatively (8.26 ± 2.83 µm) to the 3 months follow-up, but decreased continuously to the end of the follow-up period (4.57 ± 1.36 µm). The RMSDEV was significantly lower in keratoconus than in Fuchs' dystrophy pre-operatively (P = 0.01) and after suture removal (P = 0.005) and correlated inversely with VA preoperatively (R = -0.53, P = 0.04 / R = -0.69, P = 0.02), at the 1 year exam (R = -0.61, P = 0.02 / R = -0.52, P = 0.05) and after suture removal (R = -0.73, P = 0.01 / R = -0.66, P = 0.025) in keratoconus / Fuchs' dystrophy. Conclusions. The use of wavelet analysis can provide significant clinical information by separating the raw data into the parameters: “roughness”, “waviness”, “form” and various multiscalar peaks and pits. The RMSDEV, a quantitative measure for corneal irregularity, can be used as a new approach for the prediction of potential visual acuity after penetrating keratoplasty. The decomposition of the surface elevation into fundamental components is crucial for a subsequent mathematically based extraction of clinical parameters or for topography-based flying-spot ablation of irregular corneal astigmatism.

Accuracy of IRAS GT interferometer and potential acuity meter prediction of visual acuity after phacoemulsification: Prospective comparative study

Purpose: To assess and compare the accuracy of 2 methods of predicting visual acuity after phacoemulsification. Setting: Department of Ophthalmology, Montpellier, France. Methods: This prospective study evaluated 47 eyes of 47 patients having uneventful phacoemulsification over a 1-month period. All the patients had mild to moderate cataract. Visual acuity recovery was predicted using the white-light IRAS GT® interferometer on the 3- and 8-degree wide test area and the Guyton-Minkowski potential acuity meter (PAM). Best corrected visual acuity was evaluated 1 day before and 1 month after surgery. Results: Both the interferometer and PAM underestimated the retinal visual capacity. Three-degree white-light interferometry gave significantly better mean predicted results than 8-degree interferometry and the PAM. There was no statistically significant disparity between predicted and postoperative results with 3-degree interferometry (1.04 ± 0.57 logMAR; −0.09 ± 0.27 decimal) ( P = .0647) and a statistically significant disparity with 8-degree interferometry (0.89 ± 0.59 logMAR; −0.13 ± 0.27 decimal) and the PAM (0.66 ± 0.62 logMAR; −0.22 ± 0.24 decimal) ( P = .0001). The predicted values were widely dispersed; the correlation indices were 0.38 with the PAM ( P = .091), 0.39 with 3-degree interferometry ( P = .001), and 0.49 with 8-degree interferometry ( P = .0005). Conclusions: Three-degree white-light interferometry gave more accurate results than 8-degree interferometry and the PAM. The wide dispersion of results and unsatisfactory correlation indices show the tests are poor predictors of individual acuity. They should be used semiquantitatively and the results interpreted in relation to the clinical data. Qualitative methods may be useful in confirming or refuting visual recovery capacity ascertained by quantitative systems.

Cataract surgery after retinal surgery.

Many patients require surgery for cataract after retinal surgery. When evaluating patients preoperatively, the surgeon should pay careful attention to the assessment of visual function and potential acuity, and to the slit lamp examination of the lens, posterior capsule, anterior cortical vitreous, and zonules. The surgeon's technique must account for increased nuclear sclerosis, intraoperative miosis, a characteristically longer axial length, and fluctuations in anterior chamber depth from movement of the iris-lens diaphragm. Posterior capsule plaques are not unusual. Posterior capsule opacification is the most frequent late complication. Visual outcomes are usually good except when limited by pre-existing macular pathology. Vision-threatening complications of cataract surgery are unusual.

Corneal topography changes after a 15 second pause in blinking

Purpose To examine the effect of a short pause in blinking on the quantitative topographic parameters of the corneal surface. Setting Refractive corneal surgery unit of a university eye hospital. Methods Using a TMS-1 instrument (Computed Anatomy, Inc.), corneal topographic parameters were measured 5 and 15 seconds after a complete blink in 12 healthy subjects. The main outcome measures were changes in the surface regularity index (SRI) and the surface asymmetry index (SAI). Results During the pause in blinking, the mean SRI value increased from 0.18 ± 0.19 (SD) to 0.30 ± 0.19 ( P < .02) and the SAI from 0.21 ± 0.08 to 0.24 ± 0.10 ( P = .079, not statistically significant). There were no significant changes in the values for potential visual acuity, corneal refractive power, or astigmatism. Conclusion The results indicated a significant change in corneal topography during even a short pause in blinking. In follow-up studies using corneal topography, all measurements should be done at a fixed time after a complete blink.

Optical cylinder designs to increase the field of vision in the osteo-odonto-keratoprosthesis.

The single optical cylinders used in the osteo-odonto-keratoprosthesis (OOKP) are known to produce very small visual fields. Values of 40 degrees are typically quoted. The purpose of this paper is to present designs for new optical cylinders that significantly increase the field of view and therefore improve the visual rehabilitation of patients having an OOKP. Computer ray-tracing techniques were used to design and analyse improved one- and two-piece optical cylinders made from polymethyl methacrylate. All designs were required to have a potential visual acuity of 6/6 before consideration was given to the visual field and optimising off-axis image quality. Aspheric surfaces were used where this significantly improved off-axis image quality. Single optical cylinders, with increased posterior cylinder (intraocular) diameters, gave an increase in the theoretical visual field of 18% (from 76 degrees to 90 degrees) over current designs. Two-piece designs based on an inverted telephoto principle gave theoretical field angles over 120 degrees. Aspheric surfaces were shown to improve the off-axis image quality while maintaining a potential visual acuity of at least 6/6. This may well increase the measured visual field by improving the retinal illuminance off-axis. Results demonstrate that it is possible to significantly increase the theoretical maximum visual field through OOKP optical cylinders. Such designs will improve the visual rehabilitation of patients undergoing this procedure.

Potential acuity meter results in cataract patients.

To determine the ability of the potential acuity meter (PAM) to predict potential visual acuity through lenticular opacities in a group of cataract patients without significant other ocular pathology. This prospective study undertook PAM measurements on each eye of 84 subjects during preoperative hospital visits to either A Scan or Primary Care clinics. PAM results were compared to best corrected visual acuity findings obtained at least 6 weeks post-cataract extraction. Comparison of PAM result to visual outcome showed poor correlation (rho = 0.41, P = 0.0005). Using predictive estimates, 49% of subjects' PAM results underestimated visual outcome as determined by a difference of greater than 2 Snellen acuity lines in these results. Factors such as preoperative vision level, cataract type and pupil dilation did not significantly influence the predictive power of the PAM. Preoperative pinhole results were also correlated with visual outcome (rho = 0.42, P = 0.0006). Vison in the fellow eye of subjects with 6/9 or better was correlated to the PAM result indicating a moderate to good predictive power in 'normal' eyes. PAM results were considered to be poor for a clinical test. The results of this study indicate that this instrument has only a limited usefulness as part of the standard preoperatve examination in patients undergoing cataract extraction.

Which ocular and neurologic conditions cause disparate results in visual acuity scores recorded with visually evoked potential and Teller Acuity Cards?

Purpose: We investigated whether disparity between visually evoked potential (VEP) acuity scores and Teller Acuity Card (TAC) scores varied according to presence of ocular or neurologic conditions. Methods: Charts from 175 children (mean age, 34.8 months; range, 3 to 158 months) referred for visual acuity testing were examined. All children had been tested with pattern-alternation VEP and TAC and had undergone a complete eye examination. VEP and TAC acuity scores were relative to age-expected acuity scores for each acuity test. The absence and degree of macular abnormality, retinal abnormality, optic nerve hypoplasia, optic nerve atrophy, cortical visual impairment, developmental delay, cerebral palsy, seizures, and nystagmus were noted. Analysis of variance models were used to determine whether differences between VEP and TAC scores varied according to the presence of specific deficits. Logistic regression analysis determined whether degree of specific deficits was associated with a greater chance of inconsistency between VEP and TAC scores (>0.3 log unit difference). Results: Inconsistent scores were found in 48% of children. Developmental delay was associated with relatively poorer TAC than VEP score, and the chance of inconsistency increased with severity of developmental delay. Conclusions: Diagnosis-dependent variability exists between TAC and VEP scores. Therefore knowledge of the clinical picture is necessary in interpretation of VEP and TAC scores. It is not clear which test is more useful when a disparity exists, either from this or previous studies. When visual acuity is assessed longitudinally in a given child, then consistency in method for acuity assessment is important. (J AAPOS 2000;4:295-301)

Potential acuity meter accuracy in cataract patients

Purpose To determine potential acuity meter (PAM) accuracy in patients with cataract as the only ocular disease. Setting Hospital de Clínicas de Porto Alegre, Brazil. Methods This prospective study comprised 74 eyes with cataract. Patients with other ocular pathology diagnosed before or after surgery, as well as those with complicated surgeries, were excluded. All patients had PAM evaluation before surgery; these results were compared to the final postoperative visual acuity. Patients were divided into 4 cataract groups based on the Lens Opacity Classification System II: Group 1, early cataracts (nuclear opalescence [NO] 1 and/or posterior subcapsular cataracts [P] 1 and/or cortical opacity [C] < 2); Group 2, definite cataracts (NO2 and/or C2, with or without P1); Group 3, posterior cataracts (P2 or P3); Group 4, mature cataracts (N3 and/or C ≥ 3, with or without P1). The PAM result was considered accurate if it was within 2 lines of the postoperative best spectacle-corrected visual acuity (BSCVA) 3 months after surgery. Results All patients had a BSCVA of 20/20. Accuracy of the PAM was 58.3% in Group 1, 50.0% in Group 2, 27.8% in Group 3, and 6.7% in Group 4 ( P = .000 017). Patient age did not influence the results. Conclusions The PAM may be used as a complementary tool in evaluating early and nondense cataracts; however, patients should not be excluded as candidates for cataract surgery based solely on PAM results.

A randomized controlled trial of early dietary supply of long‐chain polyunsaturated fatty acids and mental development in term infants

The effects of dietary docosahexaenoic acid (DHA) supply during infancy on later cognitive development of healthy term infants were evaluated in a randomized clinical trial of infant formula milk supplemented with 0.35% DHA or with 0.36% DHA and 0.72% arachidonic acid (AA), or control formula which provided no DHA or AA. Fifty‐six 18‐month‐old children (26 male, 30 female) who were enrolled in the trial within the first 5 days of life and fed the assigned diet to 17 weeks of age were tested using the Bayley Scales of Infant Development, 2nd edition (BSID‐II) (Bayley 1993) at the Retina Foundation of the Southwest, Dallas, TX. These children had also been assessed at 4 months and 12 months of age for blood fatty‐acid composition, sweep visual evoked potential (VEP) acuity, and forced‐choice preferential looking (FPL) acuity (Birch et al. 1998). Supplementation of infant formula with DHA+AA was associated with a mean increase of 7 points on the Mental Development Index (MDI) of the BSID‐II. Both the cognitive and motor subscales of the MDI showed a significant developmental age advantage for DHA‐ and DHA+AA‐supplemented groups over the control group. While a similar trend was found for the language subscale, it did not reach statistical significance. Neither the Psychomotor Development Index nor the Behavior Rating Scale of the BSID‐II showed significant differences among diet groups, consistent with a specific advantage of DHA supplementation on mental development. Significant correlations between plasma and RBC‐DHA at 4 months of age but not at 12 months of age and MDI at 18 months of age suggest that early dietary supply of DHA was a major dietary determinant of improved performance on the MDI.

Perception of Purkinje vessel shadows and foveal granular pattern as a measure of potential visual acuity

PurposeTo compare perception of 2 entoptic phenomena, the Purkinje vessel shadows and the foveal granular pattern, as measures of retinal visual acuity using a transscleral illumination technique that bypasses the anterior segment. SettingRetinal Vascular Center and General Eye Clinic, Wilmer Ophthalmological Institute, Johns Hopkins Hospital, Baltimore, Maryland, USA. MethodsBoth eyes of 85 patients with clear ocular media, many with retinal disease, were tested for perception of these entoptic phenomena. Also, retinal visual acuity was measured with a Potential Acuity Meter through the current refractive correction. ResultsOf 114 eyes with retinal acuity of 20/40 or better, 99% perceived the Purkinje vessel shadows and 86% perceived the foveal granular pattern. Of 45 eyes with retinal acuity of 20/80 or worse, 73% perceived the Purkinje vessel shadows and 4% perceived the foveal granular pattern. ConclusionPerception of the Purkinje vessel shadows does not distinguish between good and poor retinal acuity, whereas nonperception of the vessel shadows strongly suggests poor acuity. Perception of the foveal granular pattern, on the other hand, provides a positive indication of good retinal acuity and will likely prove to be predictive of good vision after removal of significant media opacity.

The effects of long-term contact lens wear on corneal thickness, curvature, and surface regularity

PurposeTo evaluate the effect of long-term contact lens wear on corneal thickness, curvature, and surface regularity. DesignA prospective, clinic-based, case-control study. ParticipantsA total of 40 eyes of 20 normal subjects and 64 eyes of 35 subjects wearing contact lenses for more than 5 years were evaluated. MethodsThe Orbscan Corneal Topography System was used to evaluate the entire corneal thickness and curvature, anterior curvature and the anterior and posterior elevation topographic patterns in normal eyes and subjects wearing contact lenses on a regular basis for more than 5 years. Indices of TMS-1 Corneal Topography System were used to determine corneal surface regularity in subjects wearing contact lenses and normal eyes. All topographic examinations were performed after contact lenses had been removed for at least 2 weeks. Main outcome measuresThe entire corneal thickness, curvature, surface regularity index (SRI), surface asymmetry index (SAI), potential visual acuity (PVA) and topographic patterns were compared between normal eyes and subjects wearing contact lenses for more than 5 years. ResultsThe 64 eyes of 35 subjects evaluated by the Orbscan instrument had an average of 13.45 ± 6.42 years of contact lens wear. The mean corneal thickness in the center and in eight peripheral areas measured in contact lens wearing subjects was significantly reduced by about 30 to 50 μm compared to normal subjects (P < 0.001 for central and peripheral sites). No correlation was noted between central corneal thickness and degree of myopia in diopters (r = 0.15, 0.10 < P < 0.25). The corneal curvature, maximum keratometry (Max K) and minimum keratometry (Min K) readings, were significantly steeper in eyes wearing contact lenses than normal eyes (P < 0.01 for Max K and Min K measured by both instruments). No difference in the mean corneal astigmatism was noted between groups. The SRI and SAI, but not the PVA index, of the TMS-1 were significantly greater in contact lens wearers than in the control group (P < 0.01 for both SRI and SAI, P = 0.15 for PVA). The color-coded patterns of all curvature and elevation maps made with both instruments showed no significant difference between subjects wearing contact lenses and the control group. There was no significant difference between corneal curvature measurements taken with the Orbscan System or the TMS-1 System in both normal and contact lens groups. ConclusionsLong-term contact lens wear appears to decrease the entire corneal thickness and increase the corneal curvature and surface irregularity.