Risk factors for predicted refractive error after cataract surgery in clinical practice. Retrospective observational study

OBJECTIVES

To describe the preoperative characteristics of patients undergoing cataract surgery in our hospital, to determine the final visual and refractive results and to determine the preoperative characteristics that conditioned the presence of a residual refractive error (RRE) greater than one diopter.

METHODS

Retrospective analysis of cataract surgeries performed at Araba University Hospital between February 2017 and December 2019. Sociodemographic, eye comorbidity, biometric, surgical and post-surgical characteristics were collected.

RESULTS

A total of 1419 patients and 1578 surgeries were included for analysis. Of these, 9.07% had preoperative legal blindness, 31.69% eye comorbidity and 4.18% had previous surgery. Overall, 95.82% of patients achieved a corrected final visual acuity (VA) ≥ 0.5 Snellen decimal and 63.12% ≥ 1, and 96.70% of patients improved VA after surgery. RRE was between ±0.5 diopters in 77.82% of patients and between ±1 diopter in 94.74%. The most prominent risk factors that conditioned the presence of RRE greater than 1 diopter were the use of ultrasonic contact biometer, a history of glaucoma surgery, the presence of white or hard cataract, and prior legal blindness.

CONCLUSIONS

The visual results of cataract surgery were excellent, with 63.12% of patients obtaining corrected VA ≥ 1 and an RRE of ±1 diopter in 94.74%. Different risk factors influenced the achievement of poor refractive outcomes: preoperative conditions (previous surgeries, white/hard cataract, previous VA) and biometrics.

Effect of distance vision and refractive error on the spontaneous eye blink activity in human subjects in primary eye gaze

PURPOSE

To evaluate whether visual target character and visibility affects spontaneous eye blink rate (SEBR) in primary eye gaze and silence.

METHODS

Video recordings were made of young healthy adults who were either emmetropic (n=32) or who wore spectacles for refractive error (range -4.75D and +4.50D (n=31). Emmetropes had 5min recordings made whilst seated and looking towards a distant whiteboard. For spectacle wearers, recordings were made whilst looking towards the whiteboard with a 35mm sized cross, and repeated after spectacle removal. The average number of eye blinks over 5min was assessed, and its intra-subject variability as the coefficient of variation (COV).

RESULTS

Over 5min without a distance target, an average SEBR of 10.4blinks/min was observed in emmetropes with a of COV=38.1%, and a significant increase in SEBR over the 5th minute to 13.6blinks/min. Hyperopes being asked to look towards a distant target showed the essentially same blinking rate of 11.1/min with or without spectacle wear with the intra-subject variability (COV) being 21.3%. Myopic subjects showed a slightly higher SEBR if looking towards a target without their spectacles (12.4 vs. 11.0blinks/min), with the COV being 18.8%.

CONCLUSIONS

The studies indicate that some form of visual target could be useful to promote constancy of spontaneous eye blink activity over time, but that a distance visual target (when provided) does not need to be seen clearly.

Clinical evaluation of an automated subjective refraction method implemented in a computer-controlled motorized phoropter

PURPOSE

To investigate a new algorithm to perform an automated non-cycloplegic refraction in adults.

METHODS

Fifty healthy subjects were measured twice (test-retest) with the new automated subjective refraction method and with the conventional clinician subjective refraction procedure. Objective refraction was also measured with the Grand Seiko WAM-5500 autorefractor. The new automated method was inspired on the root finding bisection algorithm and on the Euclidean distances in the power vector domain. The algorithm was implemented in a computer that was synchronized with a customized motorized phoropter. Repeatability was mainly assessed with the within-subject standard deviation (Sw) and accuracy was mainly assessed with the limits of agreement.

RESULTS

The within-subject standard deviations of the power vector components (M, J0, J45) obtained for the right eye are (±0.13, ±0.04, ±0.05)D and (±0.17, ±0.03, ±0.07)D, respectively, for the clinical and the automated subjective refraction methods. The limits of agreement (with the clinical method) for the automated and the objective methods are, respectively (±0.56, ±0.18, ±0.31)D and (±0.77, ±0.15, ±0.18)D. Similar results are obtained for the left eye.

CONCLUSIONS

The proposed automated method is repeatable and more accurate than objective techniques in healthy adults. However, it is not accurate enough to replace the clinical subjective refraction yet and it should be tested in a wider population in terms of age, refraction and different ocular conditions. Despite these important limitations, this method has been shown to be a potentially valuable method to improve the access to primary eye care services in developing countries.

The effect of spherical aberration on visual performance and refractive state for stimuli and tasks typical of night viewing

PURPOSE

The aim of this work was to examine the impact of Seidel spherical aberration (SA) on optimum refractive state for detecting and discriminating small bright lights on a dark background.

METHODS

An adaptive-optics system was used to correct ocular aberrations of cyclopleged eyes and then systematically introduce five levels of Seidel SA for a 7-mm diameter pupil: 0,±0.18, and±0.36diopters (D)mm-2. For each level of SA, subjects were required to detect one or resolve two points of light (0.54 arc min diameter) on a dark background. Refractive error was measured by adjusting stimulus vergence to minimize detection and resolution thresholds. Two other novel focusing tasks for single points of light required maximizing the perceived intensity of a bright point's core and minimizing its overall perceived size (i.e. minimize starburst artifacts). Except for the detection task, luminance of the point of light was 1000cdm-2 on a black background lower than 0.5cdm-2.

RESULTS

Positive SA introduced myopic shifts relative to the best subjective focus for dark letters on a bright background when there was no SA, whereas negative SA introduced hyperopic shifts in optimal focus. The changes in optimal focus were -1.7, -2.4, -2.0, and -9.2D of focus per Dmm-2 of SA for the detection task, resolution task, and maximization of core's intensity and minimization of size, respectively.

CONCLUSION

Ocular SA can be a significant contributor to changes in refractive state when viewing high-contrast point sources typically encountered in nighttime environments.

Influence of refractive error on pupillary dynamics in the normal and mild traumatic brain injury (mTBI) populations

PURPOSE

There have been several studies investigating static, baseline pupil diameter in visually-normal individuals across refractive error. However, none have assessed the dynamic pupillary light reflex (PLR). In the present study, both static and dynamic pupillary parameters of the PLR were assessed in both the visually-normal (VN) and the mild traumatic brain injury (mTBI) populations and compared as a function of refractive error.

METHODS

The VN population comprised 40 adults (22-56 years of age), while the mTBI population comprised 32 adults (21-60 years of age) over a range of refractive errors (-9.00D to +1.25D). Seven pupillary parameters (baseline static diameter, latency, amplitude, and peak and average constriction and dilation velocities) were assessed and compared under four white-light stimulus conditions (dim pulse, dim step, bright pulse, and bright step). The Neuroptics, infrared, DP-2000 binocular pupillometer (30Hz sampling rate; 0.05mm resolution) was used in the monocular (right eye) stimulation mode.

RESULTS

For the majority of pupillary parameters and stimulus conditions, a Gaussian distribution best fit the data, with the apex centered in the low myopic range (-2.3 to -4.9D). Responsivity was reduced to either side of the apex.

CONCLUSIONS

Over a range of dynamic and static pupillary parameters, the PLR was influenced by refractive error in both populations. In cases of high refractive error, the PLR parameters may need to be compensated for this factor for proper categorization and diagnosis.

Refraction during incipient presbyopia: The Aston Longitudinal Assessment of Presbyopia (ALAP) study

PURPOSE

To investigate non-cycloplegic changes in refractive error prior to the onset of presbyopia.

METHODS

The Aston Longitudinal Assessment of Presbyopia (ALAP) study is a prospective 2.5 year longitudinal study, measuring objective refractive error using a binocular open-field WAM-5500 autorefractor at 6-month intervals in participants aged between 33 and 45 years.

RESULTS

From the 58 participants recruited, 51 participants (88%) completed the final visit. At baseline, 21 participants were myopic (MSE -3.25±2.28 DS; baseline age 38.6±3.1 years) and 30 were emmetropic (MSE -0.17±0.32 DS; baseline age 39.0±2.9 years). After 2.5 years, 10% of the myopic group experienced a hypermetropic shift (≥0.50 D), 5% a myopic shift (≥0.50 D) and 85% had no significant change in refraction (<0.50 D). From the emmetropic group, 10% experienced a hypermetropic shift (≥0.50 D), 3% a myopic shift (≥0.50 D) and 87% had no significant change in refraction (<0.50 D). In terms of astigmatism vectors, other than J45 (p<0.001), all measures remained invariant over the study period.

CONCLUSION

The incidence of a myopic shift in refraction during incipient presbyopia does not appear to be as large as previously indicated by retrospective research. The changes in axis indicate ocular astigmatism tends towards the against-the-rule direction with age. The structural origin(s) of the reported myopic shift in refraction during incipient presbyopia warrants further investigation.

Visual deficits in Nepalese patients with oculocutaneous albinism

BACKGROUND

Albinism poses a significant threat to visual functions and causes remarkable ocular morbidity often resulting in visual disabilities. The study aimed at describing the visual status in patients with diagnosed cases of complete oculocutaneous albinism (OCA) attending to a tertiary eye hospital in Nepal.

METHODS

This was a cross-sectional descriptive hospital-based study of all diagnosed oculocutaneous albinotic cases (16 males and 9 females; mean age of 16 years) who visited the Department of Ophthalmology at the Institute of Medicine, for ocular consultation between September 1, 2011 and December 1, 2013.

RESULTS

Twenty-five cases (50 eyes) with OCA were enrolled in the study. All the participants had maximally reduced visual acuity (mean: 1.24±0.50logMAR). Myopic astigmatism was the most common refractive error (n=17; 34%). 58% of all participants had with-the-rule astigmatism. Considering the spherical equivalent power, most of the eyes (n=30; 60%) had myopia, with overall mean SE refractive error of -1.59±5.39D. Visual acuity improved significantly with refractive correction in place (paired sample t-test, p<0.05). Horizontal pendular nystagmus was the most common nystagmus (n=34 eyes; 68%). Alternating esotropia and alternating exotropia each were observed in 16% of participants who had strabismus (40% of all cases). The diaphanous iris, foveal hypoplasia and poliosis were the most consistent clinical features.

CONCLUSION

Patients with OCA present with a broad spectrum of visual deficits that impair the visual functions. Significant improvement in visual acuity following optical correction serves as an impetus to the reduction of visual disabilities in individuals with albinism.

Visual impairment attributable to uncorrected refractive error and other causes in the Ghanaian youth: The University of Cape Coast Survey

PURPOSE

To determine the prevalence of visual impairment attributable to refractive error and other causes in a youthful Ghanaian population.

METHODS

A prospective survey of all consecutive visits by first-year tertiary students to the Optometry clinic between August, 2013 and April, 2014. Of the 4378 first-year students aged 16-39 years enumerated, 3437 (78.5%) underwent the eye examination. The examination protocol included presenting visual acuity (PVA), ocular motility, and slit-lamp examination of the external eye, anterior segment and media, and non-dilated fundus examination. Pinhole acuity and fundus examination were performed when the PVA≤6/12 in one or both eyes to determine the principal cause of the vision loss.

RESULTS

The mean age of participants was 21.86 years (95% CI: 21.72-21.99). The prevalence of bilateral visual impairment (BVI; PVA in the better eye ≤6/12) and unilateral visual impairment UVI; PVA in the worse eye ≤6/12) were 3.08% (95% CI: 2.56-3.72) and 0.79% (95% CI: 0.54-1.14), respectively. Among 106 participants with BVI, refractive error (96.2%) and corneal opacity (3.8%) were the causes. Of the 27 participants with UVI, refractive error (44.4%), maculopathy (18.5%) and retinal disease (14.8%) were the major causes. There was unequal distribution of BVI in the different age groups, with those above 20 years having a lesser burden.

CONCLUSION

Eye screening and provision of affordable spectacle correction to the youth could be timely to eliminate visual impairment.

[Long-term results of lasik refractive error correction after penetrating keratoplasty in patients with keratoconus]

OBJECTIVE

To evaluate the long term results of Lasik for residual refractive errors (RE) after penetrating keratoplasty (PKP) for keratoconus (KC).

DESIGN

Retrospective cohort.

METHOD

Records of 14 consecutive patients (19 eyes) who had Lasik after PKP for KC were retrospectively reviewed. In all eyes with refractive stability and suture removed before Lasik, far distance Visual Acuity with (AVCC) and without correction (AVSC), spherical equivalent (EE), refractive (Ast) and keratometric (dK) astigmatism were analyzed pre- and post-operatively before and after one year of follow up. Data were analyzed using Shapiro-Wilk normality test, Student t test and Mann-Whitney test. A P-value of <0,05 was considered statistically significant.

RESULTS

The mean follow-up time was 3.16 months for the follow-up before one year postoperative and 5.8 years for the follow-up after one year postoperative. The best spectacle corrected visual acuity of 0,11 LogMAR (DE 0,07) before Lasik remained stable throughout the study. The SE decreased from -2.6 (DE 3.53) to -0,36 D (DE 1.33) (P<.05) for the follow-up before one year postoperative and -1.28 D (DE 1.63) (P=.07) for the follow-up after one year postop. The refractive cylinder was reduced from -3.43 (DE 1.35) preoperative to -1.37 D (DE 1.24) (P<.05) and -3.21 D (DE 2.29) (P=.36) in the long term after one year of follow-up.

CONCLUSIONS

Lasik refractive results regress one year after the operation; therefore it is not an effective long-term surgical refractive procedure for residual refractive errors after PKP for KC.

The prevalence of refractive conditions in Puerto Rican adults attending an eye clinic system

PURPOSE

To determine the prevalence of refractive conditions in the adult population that visited primary care optometry clinics in Puerto Rico.

METHODS

A retrospective cross-sectional study of patients examined at the Inter American University of Puerto Rico School of Optometry Eye Institute Clinics between 2004 and 2010. Subjects considered had best corrected visual acuity by standardized subjective refraction of 20/40 or better. The refractive errors were classified by the spherical equivalent (SE): sphere+½ cylinder. Myopia was classified as a SE>-0.50D, hyperopia as a SE>+0.50 D, and emmetropia as a SE between -0.50 and +0.50, both included. Astigmatism equal or higher than 0.25 D in minus cylinder form was used. Patients with documented history of cataract extraction (pseudophakia or aphakia), amblyopia, refractive surgery or other corneal/ocular surgery were excluded from the study.

RESULTS

A total of 784 randomly selected subjects older than 40 years of age were selected. The estimated prevalence (95%, confidence interval) among all subjects was hyperopia 51.5% (48.0-55.0), emmetropia 33.8% (30.5-37.2), myopia 14.7% (12.1-17.2) and astigmatism 69.6% (68.8-73.3). Hyperopia was more common in females than males although the difference was not statistically significant. The mean spherical equivalent values was hyperopic until 70 y/o and decreased slightly as the population ages.

CONCLUSION

Hyperopia is the most common refractive error and its prevalence and seems to increase among the aging population who visited the clinics. Further programs and studies must be developed to address the refractive errors needs of the adult Puerto Rican population.

Prevalence of correctable visual impairment in primary school children in Qassim Province, Saudi Arabia

PURPOSE

The worldwide prevalence of refractive errors (RE), which is a common cause of treatable visual impairment among children, varies widely. We assessed the prevalence of correctable visual impairment (uncorrected RE) in primary school children in Qassim, Saudi Arabia.

METHODS

A cross-sectional study was conducted in 21 primary schools. A total of 5176 children (mean age 9.5±1.8 years), 2573 boys (49.7%) and 2603 girls (50.3%), underwent a comprehensive eye examination. The examinations consisted of visual acuity, autorefraction, cover test, ocular motility, pupillary evaluation, anterior segment examination, cycloplegic auto-refraction and dilated fundus examination with direct ophthalmoscopy. The children were divided into groups based on their age and gender.

RESULTS

The overall prevalence of RE in the better eye was 18.6% (n=963), and the prevalence of uncorrected RE 16.3% (n=846), with only 2.3% (n=127) of children wearing spectacles during examination. The prevalence of uncorrected myopia (5.8%) and myopic astigmatism (5.4%) was higher compared to that of hyperopic astigmatism (2.7%), mixed astigmatism (1.7%) and hyperopia (0.7%). The anisometropia prevalence was 3.6%. Risks for astigmatism, myopia and anisometropia were positively associated with age. In addition, myopia and anisometropia risks were also associated with female gender, while risk of astigmatism was correlated with male gender. Few children with vision reducing RE wore spectacles; an additional 16.3% of children could benefit from spectacle prescription.

CONCLUSION

The prevalence of uncorrected RE in children is relatively high and represents an important public health problem in school-aged children in Qassim province. Performance of routine periodical vision screening throughout childhood may reverse this situation.

[Evaluation of predictability and refractive changes in pediatric pseudophakia]

OBJECTIVE

Evaluate the predictability of the postoperative refraction and refractive changes in pediatric pseudophakia.

METHODS

Prospective, longitudinal follow-up on patients under the age of 15 years operated on for a cataract with intraocular lens, with 5 continuous years of follow-up. The patients were divided into 4 groups according to age at the time of the surgery: group from 0 to 2 years old, from 3 to 5 years old, from 6 to 8 years old, and 9 years and over. Error prediction and refractive change were studied. Statistical analysis was performed using the Student t and ANOVA test.

RESULTS

A total of 60 eyes were included (44 patients). No significant differences were found between the unilateral and bilateral group. The prediction error in the 0 to 2 years group was 1.5±1.8 D, significantly higher than in the other groups (ANOVA P=.01). Refractive change in 5 years of the group of 0 to 2 years was -4.7±3.4 D (ANOVA P=.0002), while in the other groups it was significantly lower, with no differences between them.

CONCLUSIONS

The 0 to 2 years group was less hyperopic than expected, 100% within the accepted of 2 standard deviations, but with a high variability. The refractive change observed in this group coincides with previous reports that the largest growth and increase in axial length occurs during the first 2 years. The calculation and use of an IOL in children has a better immediate refractive prediction, and at long term in those older than 2 years of age.