Erroneous automated refraction in a case of asteroid hyalosis

Asteroid Hyalosis: An Update on Prevalence, Risk Factors, Emerging Clinical Impact and Management Strategies

Asteroid hyalosis (AH) is a benign clinical entity characterized by the presence of multiple refractile spherical calcium and phospholipids within the vitreous body. First described by Benson in 1894, this entity has been well documented in the clinical literature and is named due to the resemblance of asteroid bodies on clinical examination to a starry night sky. Today, a growing body of epidemiologic data estimates the global prevalence of asteroid hyalosis to be around 1%, and there is a strong established association between AH and older age. While pathophysiology remains unclear, a variety of systemic and ocular risk factors for AH have recently been suggested in the literature and may provide insight into possible mechanisms for asteroid body (AB) development. As vision is rarely affected, clinical management is focused on differentiation of asteroid hyalosis from mimicking conditions, evaluation of the underlying retina for other pathology and consideration of vitrectomy in rare cases with visual impairment. Taking into account the recent technologic advances in large-scale medical databases, improving imaging modalities, and the popularity of telemedicine, this review summarizes the growing body of literature of AH epidemiology and pathophysiology and provides updates on the clinical diagnosis and management of AH.

Spotlight on Asteroid Hyalosis: A Clinical Perspective

Asteroid hyalosis is a benign degenerative condition of the vitreous that is often asymptomatic. Our purpose with this narrative review is to provide a current overview of asteroid hyalosis from a clinical perspective. We review the epidemiology and risk factors, the clinical diagnosis and differential diagnoses, clinical challenges in eyes with asteroid hyalosis, and the treatment of asteroid hyalosis. Many clinical questions remain unanswered, and the current evidence to guide clinical practice is largely based on anecdotal evidence and clinical experience. More studies on asteroid hyalosis from a clinical perspective are warranted.

Asteroid hyalosis-a comprehensive review

Asteroid hyalosis is a relatively common cause of vitreous opacities, which is possibly associated with diabetes mellitus and hereditary pigmentary retinopathies. We review the history, epidemiology, and biochemistry of asteroid hyalosis, as well as its relationship with ocular and systemic conditions. We describe imaging modalities used for diagnostic evaluations in cases of severe asteroid hyalosis and propose hypotheses regarding its lack of significant effects on vision. We discuss cataract surgery in patients with asteroid hyalosis and the selection of intraocular lenses for implantation.

Asteroid Hyalosis Masquerading as Vitreous Hemorrhage on Point-of-Care Sonography

Point-of-care ocular sonography is frequently used in the emergency department to evaluate patients with vision disorders. We describe a case series of 3 patients who ultimately had a diagnosis of asteroid hyalosis, a lesser-known condition that on point-of-care sonography may be mistaken for vitreous hemorrhage. Asteroid hyalosis is considered a benign degenerative condition. In contrast, vitreous hemorrhage may be an ocular emergency that warrants an urgent ophthalmologic consultation if there is an underlying retinal tear or detachment. Although similar in appearance on sonography, recognition of the subtle pathognomonic sonographic features along with their clinical presentations can differentiate these diseases, with vastly different management strategies and dispositions.

The Precision of Wavefront Refraction Compared to Subjective Refraction and Autorefraction

PURPOSE

To determine the precision (repeatability) of several methods of calculating refraction from higher-order wavefront aberration data and to compare these wavefront refractions with lower-order (LO) wavefront refraction, subjective refraction, and autorefraction.

METHODS

Four clinicians refracted 16 normal participants aged 23.6 +/- 1.2 years, 69% female with an average spherical equivalent refractive error of -3.03 +/- 2.55 D, median sphere -2.50 D (minimum -7.50, maximum +4.75), and median cylinder -0.50 D (minimum -3.00, maximum 0). Participants were cyclopleged and underwent subjective refraction, autorefraction on two machines (Nidek AR-800, Topcon KR-8000), and wavefront sensing using the Wavefront Sciences Complete Ophthalmic Analysis System. Wavefront error was used to calculate: LO refraction, refractions that incorporated higher-order spherical and astigmatism terms from up to the 4th, 6th, and 10th orders (PCM4, PCM6, and PCM10), and a method based on optimizing image quality metrics [wavefront analysis technology (WAT) refraction]. Within and between examiner agreements for total dioptric difference were determined using Bland-Altman limits of agreement (LOA).

RESULTS

The interexaminer LOA for individual measurements for M, J0, J45 were: Topcon (+/-0.18, +/-0.10, +/-0.06), Nidek (+/-0.28, +/-0.16, +/-0.09), LO (+/-0.17, +/-0.10, +/-0.06), PCM4 (+/-0.26, +/-0.09, +/-0.06), PCM6 (+/-0.37, +/-0.17, +/-0.34), PCM10 (+/-0.54, +/-0.32, +/-0.40), WAT (+/-0.28, +/-0.20, +/-0.15), and subjective refraction (+/-0.48, +/-0.20, +/-0.13) and averaging across three measures LOA: Topcon (+/-0.15, +/-0.08, +/-0.05), Nidek (+/-0.21, +/-0.13, +/-0.07), LO (+/-0.12, +/-0.06, +/-0.04), PCM4 (+/-0.16, +/-0.05, +/-0.04), PCM6 (+/-0.23, +/-0.09, +/-0.19), PCM10 (+/-0.29, +/-0.19, +/-0.24), and WAT (+/-0.18, +/-0.12, +/-0.10). The within-examiner LOA for M, J0, J45 were: Topcon (+/-0.08, +/-0.04, +/-0.02), Nidek (+/-0.13, +/-0.07, +/-0.05 D), LO (+/-0.11, +/-0.07, +/-0.04), PCM4 (+/-0.17, +/-0.07, +/-0.04 D), PCM6 (+/-0.28, +/-0.12, +/-0.24 D), PCM10 (+/-0.42, +/-0.24, +/-0.32 D), and WAT (+/-0.19, +/-0.14, +/-0.09 D).

CONCLUSIONS

All objective refractions except for PCM10 were more repeatable across clinicians than subjective refraction. The precision of all refractions were improved by an expected amount through averaging over multiple measurements. Wavefront refractions were not as precise as standard autorefractions, although not clinically significantly worse.

Autorefraction as an outcome measure of laser in situ keratomileusis

PURPOSE

To determine the limits of agreement between subjective refraction and autorefraction before and after laser in situ keratomileusis (LASIK) to assess whether autorefraction is a valid refractive outcome measure of refractive surgery.

SETTING

Ultralase, Leeds, United Kingdom.

METHOD

The prospective study involved consecutive preoperative normal patients and post-LASIK patients who had autorefraction using the Nidek ARK 700A autorefractor and careful subjective refraction (masked to autorefraction). Inclusion criteria were age greater than 18 years and healthy eyes with a visual acuity better than 0.1 logMAR (6/7.5) with or without previous LASIK. Refractions were compared by spherical equivalent (SE) using Bland-Altman limits of agreement and astigmatic vector difference using the median and the 95th percentile. The effect of time after treatment and treatment strength were explored.

RESULTS

Data were collected from 208 preoperative patients and 237 post-LASIK patients. Preoperatively, the agreement between subjective refraction and autorefraction for the SE was -0.10 diopter (D) +/- 0.35 (SD) and the median difference for the astigmatic vector was 0.28 D with a 95th percentile of 0.72 D. Post-LASIK, the SE agreement was similar, -0.09 +/- 0.39 D, but the astigmatic vector agreement decreased slightly with a median of 0.31 D and a 95th percentile of 1.02 D. This decrease reflected poorer agreement in patients whose pre-LASIK refractive error was greater than +4.00 D. Removing this group brought the median astigmatic difference post-LASIK to 0.27 D with a 95th percentile of 0.87 D, similar to that in the preoperative normals. The percentage within +/-0.50 D and +/-1.00 D of the attempted correction was 56.1% and 78.5%, respectively, with subjective refraction and 51.2% and 78.1%, respectively, with autorefraction.

CONCLUSIONS

Autorefraction showed excellent agreement with subjective refraction and was unaffected by refractive surgery except after LASIK for high hyperopia. Most outcomes were correctly classified in the standard categories (+/-0.50 D, +/-1.00 D), illustrating that autorefraction is a valid outcome measure of refractive surgery.

A Comparison of Autorefractor Performance

PURPOSE

To compare the agreement between subjective refraction and autorefraction using two commercially available autorefractors.

METHODS

Prospective data were collected for 190 subjects using either the Nidek ARK-700A (Fremont, CA) or the Topcon KR-8000 (Paramus, NJ) and subjective refraction (masked to autorefraction). Refractions were compared in terms of spherical equivalent using Bland-Altman limits of agreement and astigmatic vector difference using median and 95th percentile.

RESULTS

The two groups were similar for age, gender, spherical equivalent, and astigmatic power. The differences in spherical equivalent between subjective and autorefraction were significantly different (mean +/- SD; Nidek, -0.03 +/- 0.36 D; Topcon, +0.11 +/- 0.34 D; analysis of variance, F = 7.84; p < 0.01). However, the 95% limits of agreement were similar: Nidek, -0.74 to +0.68 D; Topcon, -0.55 to +0.77 D. The median differences in astigmatic vector difference were also similar: Nidek, 0.27 D and Topcon, 0.25 D. However, the 95th percentile was 0.67 D for Nidek and 1.09 D for Topcon. There was a low frequency of large (>1.00 D) differences in spherical equivalent, 1.1% with each autorefractor. There were five cases with astigmatic vector difference >1 D, all with the Topcon KR-8000 (5.3%).

CONCLUSIONS

Both autorefractors show excellent agreement with subjective refraction. Despite a statistically significant difference in mean spherical equivalent (0.14 D), near identical limits of agreement (0.10 D difference) suggest clinical equivalence. Conversely, for astigmatism, despite similar median scores, major outliers were more likely with the Topcon, reflected in a 0.42 D larger 95th percentile, which suggests a small advantage for the Nidek for avoiding large astigmatic errors.