The vitreoscope significantly increased the visibility of transparent floaters, which were detected by 84.1% of subjects (score ≥ 1; Table 4). Using this method, 67.0% of participants reported strand-shaped floaters (+20.3% compared with the light box; P < 0.001, Wilcoxon signed-rank test), but the perception of cells or membranes was not significantly different from the light box method, at 31.3% and 8.8%, respectively (−1.7%, P = 0.372; +2.2%, P = 0.211). Using the vitreoscope, fewer subjects observed opaque floaters, with 4.9% of subjects reporting well-defined floaters and 1.6% reporting ill-defined floaters (Fig. 3B). No subject reported the ring-shaped morphology by either detection method.
Floater Discomfort Assessment
There was considerable variation in floater discomfort reported by participants. On the questionnaire, most subjects were found to have no floater disturbance (80.2%). The rest of the cohort reported mild disturbance (13.2%), moderate disturbance (5.5%), and manifest disturbance (1.1%). No subject recruited in the cohort had attended ophthalmic services for medical advice regarding floaters.
The findings of the light box assessment showed a small but statistically significant correlation to the questionnaire score after exclusion of 1 outlier (Pearson r = 0.323, P < 0.001; Fig. 4A). The vitreoscope assessment also showed a small correlation to the reported symptoms, again after the exclusion of 1 outlier with a floater score of 24 (Pearson r = 0.174, P < 0.001; Fig. 4B).
Finally, a generalized linear model was used to analyze the correlation between floater discomfort score and floater type detected by light box. This yielded no significant relationships (P > 0.05). Only the “cell” (C) and the “small, multiple, and well-defined” (SM) types had P values close to the significance level (P = 0.071 and P = 0.054, respectively).
Correlation with Age, Axial Length, or Refraction
The weighted binocular floater scores measured by light box increased significantly with subject age (excluding 1 outlier, Pearson r = 0.203, P = 0.006; Fig. 5A). The same was found for the floater discomfort score (r = 0.194, P = 0.009; Fig. 5B). When only right eyes were examined, no significant correlation was found between monocular floater score and axial length or spherical equivalent, even after correction for age (first-order correlation coefficient, P = 0.131, P = 0.070, respectively).
Comparing age and right eye biometry of subjects with no floater discomfort (ie, discomfort score ≤ 1) and subjects with floater discomfort (ie, score > 1) showed a significant difference for subject age (unpaired t test, P = 0.047) but not for any biometric parameter. Although in this analysis, the binocular floater discomfort score was used to separate the (monocular) right eye biometry into 2 groups for comparison, this result is still expected to be accurate given the strong correlations that are known to exist between the biometry of fellow eyes.
Visual disturbance from floaters can affect quality of life even if it does not directly affect objective visual acuity.7 The lack of correlation between patient perception and change in measureable visual acuity is a significant problem in treating symptomatic floater patients. Without a significant decline in visual acuity, surgeons are reluctant to intervene, despite the potential to alleviate symptoms.10 The failing for this situation lies not in patient perception, but in the lack of appropriate assessment tools to investigate the nature of this type of complaint, as visual acuity is ill equipped as a measure for floater-related visual impairment. This issue is also seen in a number of reports on floater interventions that use levels of patient satisfaction to gauge the outcome of the procedure.10–14 Although satisfaction is certainly an important outcome, it is difficult to quantify and highly subjective. The potential for a placebo influence is also difficult to define. There is, therefore, a need for a metric to quantify vitreous floaters. The proposed system constitutes a first step toward such a metric.
It is also important to emphasize that the light box and vitreoscope methods each present floaters to the subject in a different way, with the light box emitting diffuse light to enhance the view of floaters in close proximity to the retina and the vitreoscope visualizing floaters that pass through the cone of incident light, regardless of their distance to the retina. In practice, the field of view of the vitreoscope is relatively narrow in comparison with that of the light box, which reduces the volume of the light cone between the crystalline lens and the retina used for floater detection (Fig. 1B). This accounts for the 32.4% of subjects that reported seeing fewer floaters in the vitreoscope, although they should theoretically report more. For this reason, we recommend that both methods be used side by side to optimize floater detection.
As seen in Figure 3, perception of vitreous floaters may be considered a very common phenomenon in the general population. Using the light box and vitreoscope assessment, we found that 84% of participants detected some form of floaters. Despite this high prevalence of floaters on assessment, most subjects were either asymptomatic or not particularly disturbed by their floaters. This was also reinforced by the fact that not a single participant in this cohort felt the need to consult an ophthalmologist for floater assessment. This is in contrast with the often severe complaints of symptomatic floater patients.7
We could not confirm any correlation between floater score and biometry, which would exclude axial length and any other biometric parameter as risk factors for floaters. The increase in floater perception and floater discomfort with age, which has been suggested both theoretically5 and clinically,15 was confirmed by our results. No patients reported seeing ring-shaped floaters, for example Weiss rings, which may be because the participants recruited were from the general population and not presenting for clinical floater assessment.
Because our findings reveal such a high prevalence of floaters in the population, this study raises the question as to whether the floaters of symptomatic patients are fundamentally different to those of the general population. Symptomatic patients may have different biometry, floater density, or floater position to the asymptomatic population, although this has not yet been described. Another source of potential difference may be in patient personality, employment, everyday lighting conditions, and others. Clinical verification of the grading system in symptomatic floater patients and a comparison with fundoscopy should therefore be the subject of a follow-up study.
The authors thank Nadia Zakaria, Jeroen Claeys, and Greet Vandeweyer for their support in collecting the data.
1. Hollands H, Johnson D, Brox AC, et al. Acute-onset floaters and flashes. JAMA
. 2009; 302: 2243–2249.
2. Sebag J. Floaters and the quality of life. Am J Ophthalmol
. 2011; 152: 3–4.
3. Swann D. Biochemistry of the vitreous. In: Schepens CL, Neentens A (eds). The Vitreous and Vitreoretinal Interface
. Springer Press, New York; 1987: 59–72.
4. Bishop PN. Structural macromolecules and supramolecular organisation of the vitreous gel. Prog Retin Eye Res
. 2000; 19: 323–344.
5. Ponsioen TL, Hooymans JMM, Los LI. Remodelling of the human vitreous and vitreoretinal interface—a dynamic process. Prog Retin Eye Res
. 2010; 29: 580–595.
6. Los LI. The rabbit as an animal model for post-natal vitreous matrix differentiation and degeneration. Eye (Lond)
. 2008; 22: 1223–1232.
7. Wagle AM, Lin WY, Yap TP, et al. Utility values associated with vitreous floaters
. Am J Ophthalmol
. 2011; 152: 60–65.
8. Sinclair SH, Loebl M, Riva CE. Blue field entopic phenomenon in cataract patients. Arch Ophthalmol
. 1981; 97: 1092–1095.
9. Leibowitz H. The use and calibration of the Maxwellian view in visual instrumentation. Am J Psychol
. 1954; 67: 530–532.
10. Schiff WM, Chang S, Mandava N, et al. Pars plana vitrectomy for persistent visually significant vitreous opacities
. 2000; 20: 591–596.
11. Wilkinson CP. Safety of vitrectomy for floaters—how safe is safe? [Editorial]. Am J Ophthalmol
. 2011; 151: 919–920.
12. Tan HS, Mura M, Lesnik Oberstein SY, et al. Safety of vitrectomy for floaters. Am J Ophthalmol
. 2011; 151: 995–998.
13. Schulz-Key S, Carlsson JO, Crafoord S. Longterm follow-up of pars plana vitrectomy for vitreous floaters
: complications, outcomes and patient satisfaction. Acta Ophthalmol
. 2011; 89: 159–165.
14. de Nie KF, Crama A, Tilanus MAD, et al. Pars plana vitrectomy for disturbing primary vitreous floaters
: clinical outcome and patient satisfaction. Graefes Arch Clin Exp Ophthalmol
15. Sendrowski DP, Bronstein MA. Current treatment for vitreous floaters
. 2010; 81: 157–161.
Keywords:© 2016 by Asia Pacific Academy of Ophthalmology
vitreous floaters; vitreous opacities; ocular biometry; vitreoscope