Efficacy and Safety of YAG Laser Vitreolysis for Symptomatic Vitreous Floaters

INTRODUCTION

Vitreous is an extraordinary extracellular matrix containing 98% water. Only 2% of the vitreous is composed of macromolecules, despite that, these molecules are critical to the vitreous' gel state, transparency, and physiological function (s) in the eye. ¹

By maintaining collagen fibrils separate, hyaluronan preserves vitreous transparency in youth. Over time, hyaluronan separates from collagen, inducing cross-linking and collagen aggregation with fibrous structures that scatter light. ²

The association between collagen and hyaluronan is changed by myopia and ageing, resulting in concurrent gel liquefaction and fibrous degeneration. The most prevalent reasons for the vitreous floaters visual phenomenon are vitreous opacification and vitreous body collapse, which occur during posterior vitreous detachment (PVD). ³

It ranks among the most common complaints made to ophthalmologists. ⁴ The majority of patients could tolerate their symptoms, but a significant minority consider floaters to be bothersome. Floaters are particularly problematic for myopes, pseudophakes, and individuals whose jobs demand precision detail work. ⁵ 

Vitreous floaters could be extremely annoying, interfere with perceptions and day-to-day visual comfort, and cause a person to become physically and psychologically exhausted. ⁴ Previously, these vitreous opacities were thought to be innocious, but occasionally they can impair vision, make difficulity to read or drive, and generally have a negative influence on quality of life. ³

According to a utility analysis, patients having symptomatic floaters became willing to take a 7% risk of blindness and an 11% risk of mortality to get rid of the symptoms. Floaters had utility values that were equivalent to those of ARMD and comparable to those of glaucoma, mild angina, strokes, and asymptomatic HIV. ⁶

The medical community has up until now largely neglected the suffering of people having vision-degrading myodesopsia, perhaps as a result of floaters' ubiquity. Better disease staging and more precise detection of severe cases that require treatment were made possible by improved diagnostics.¹

Until recently, patients with annoying floaters had just two choices: either learn to bear with them or have a vitrectomy. PPV effectively eliminates the symptoms linked to floaters, but it is an extremely invasive operation with a high risk of complications. ⁵

A lot of attention has been paid to the usage of the YAG laser for vitreolysis in recent years for the therapy of bothersome vitreous floaters.⁷

Laser vitreolysis works by photodisrupting vitreous aggregates, which reduces opacity and shifts them off the optical axis. ⁴

The publication of studies with contradictory findings and possibly sight-threatening consequences, however, has stoked controversy and might have prevented the technique from being widely used. As a result, the technique is still highly contentious.⁷

The study aimed to evaluate the safety and effectiveness profile of YAG laser vitreolysis as a modality of therapy for symptomatic vitreous floaters.

PATIENTS AND METHODS

Fifty eyes from fifty patients having symptomatic vitreous floaters were selected from Al-Azhar University Hospitals' outpatient ophthalmology clinics (Al Hussein and Sayed Galal). This non-randomized prospective study took place between January 2019 and February 2022.

Inclusion criteria: Symptomatic floaters (a self-rated visual disturbance that is at least assessed as 4 on a 0–10 scale (0 = no symptoms, 10 = debilitating symptoms), symptoms duration of at least 3 months and stable, absence of flashes of light suggesting an incomplete PVD, vitreous opacities that are at least 3 mm from the retina and 4 mm away from the crystalline lens's posterior lens capsule, as assessed on a B-scan, and PVD that is confirmed by a clinical evaluation, a B-scan, and an Optical Coherence Tomography.

Exclusion criteria: Snellen best-corrected visual acuity (BCVA) less than 20/40 in the other eye, history of retinal tear or detachment, active retinal pathology such as diabetic retinopathy, uveitis, aphakia in the studied eye, and history of glaucoma or high eye pressure.

Ethical consideration:

The protocol was submitted for the Research Ethics Committee's approval. All patients received a complete explanation of the procedure with its own benefits and possible complications. According to the Medical Ethics Committee of the Faculty of Medicine at Al-Azhar University, informed written agreement has been obtained from all patients prior to the initiation of the procedure.

Preoperative Evaluation

Detailed history taking including: Age, gender, past or present eye problems, history of cataract or refractive surgery, history of elevated IOP, glaucoma drops, history of intraocular inflammation, retinal tear and detachment. A family history of RD or hereditary conditions affecting collagen such as Stickler or Marfan syndrome, history of psychiatric problems. Floater history: for how long the patient had these symptoms? presence of flashes of light, number of the floaters, how do these floaters look like? Cob webs or flying particles? severity of symptoms, on 0-10- point scale and in what activities does the floater bother the patient.

Examination of the eyes including: Best corrected visual acuity (BCVA) and refraction. Examination of the anterior segment and measurement of IOP with a Goldmann applanation tonometer. Fundus examination using the indirect ophthalmoscope with Volk 20 diopters lens and scleral depression and fundus biomicroscopy with a non-contact lens (Volk 90 diopters lens), presence or absence of PVD, morphology of the floaters: The floaters or vitreous opacities correlated with the patient’s symptoms.

Figure (1): fundus photo shows Weiss ring opacity (patient no. 20)

B-scan US:  using Scanmate Flex B-scan (DGH Technology, Inc. USA): For detection of PVD, measure the locations of the opacities from the retina.

Figure (2): B scans of patients no. (7 and 9).

Figure (3): B scans of patients no. (18 and 35).

Optical coherence tomography (OCT): macular morphology, central subfield thickness, and existence of PVD utilizing the DRI Triton plus OCT system (Topcon Co., Japan).

Figure (4): OCT scan of patient no. 15 shows complete PVD.

YAG vitreolysis procedure: The procedure done using Ultra Q Reflex™ (Ellex Medical Lasers, Adelaide, Australia).

The pupil was dilated with tropicamide 1% and phenylephrine 2.5%. Topical anesthetic with benoxinate 0.4%. Ocular Karickhoff 21 mm Vitreous Lens for floaters in the optic axis centre and Ocular Karickhoff Off-Axis Vitreous Lens for floaters off the optic axis. The initial energy setting was 2.5 mJ with a single pulse per shot. The laser energy was titrated to a suitable level, where plasma formation with gas bubble formation was observed. The laser shots given per patient will be ceased after vaporization of the visually significant floaters or a maximum of 500 shot per treatment session. Other treatment sessions was considered after 2 weeks if there were more residual floaters and the symptoms were still present.

Follow up: On the first postsurgical day, the first week, the first month, the third month, and the sixth month, all patients underwent repeated assessment with BCVA, IOP by applanation tonometry, slit-lamp examination, and indirect ophthalmoscopy with scleral depression. Patients have been questioned about their floater symptoms compared to before the laser procedure and asked to rate their post-operative improvement as one of the following at each follow-up visit: (a) Failure: floaters are the same or worse. (b) Partial success: There has been some improvement, but there are still some moderate annoyances. (c) Significant success: substantial improvement with minor inconvenience. (d) Complete success: all floaters have been resolved. Any developed complications were assessed and managed.

Outcome measure: subjective change in floater symptoms. The incidence of complications leading to alterations in the eye's structure or reduced vision both immediately following therapy and up to 6 months post-interventional. Changes in BCVA and IOP following the laser procedure.

Statistical analysis: Version 8 of GraphPad Prism was utilised to conduct the statistical analysis. The BCVA and IOP were compared pre and post therapy using the Wilcoxon matched pairs signed rank test. Statistical significance was defined as p-values less than 0.05.

RESULTS

This study was performed on fifty eyes of fifty patients. All of them had symptomatic vitreous floaters with established PVD and underwent YAG laser vitreolysis.

Table (1): Demographic characteristics of the studied patients

The patients' ages varied from 38 to 68 years, with an average age (±SD) of 58 ± 6.8 years. Thirty-eight patients (76%) were women, and twelve patients (24%) were men. The right eye was impacted in 27 cases (54%), whereas the left eye was affected in 23 cases (46%) (Table 1).

Table (2): characteristics of floaters

The duration of floaters symptoms ranged from 3 months to 18 months with the mean of 6.5. The severity of symptoms on (0-10) scale ranged from 5 to 9 (7.1 ± 0.8). 18 patients (36%)  were affected more when they were performing near tasks like reading, 11 patients (22%) were affected more in distant vision like driving while the remaining 21 patients (42%) were annoyed by their floaters all of the time (Table 2).

Figure (5): correlation between the patient age and severity of symptoms.

The patient's age and the severity of their symptoms had a significant negative association, p = 0.0015** (Figure 5).

Table (3): previous ocular conditions in the treated eyes.

27 (54%) patients had previous cataract surgery. 4 (8%) patients underwent LASIK surgery, 3 (6%) for myopia and 1 (2%) for Hyperopia.  1 (2%) patient had refractive lens exchange (RLE) for high myopia. 18 (36%) patients had unremarkable ophthalmic history (Table 3).

Table (4): Descriptive analysis of the studied patients according to ametropia.

Of the 50 patients of this study, 3 patients were high myopes with a refraction spherical equivalent ≥ -6 diopters, 21 patients were low to moderate myopes with a spherical equivalent < 6 diopters, while 18 patients were hypermetropes, and 8 patients were emmetropes (Table 4).

Figure (6): The pie chart shows the total number of sessions required for vitreolysis completion.

Targeted floaters were classified into; Weiss ring floaters (27(54%) patients) and mid-vitreal opacity (23(46%) patients).

The number of sessions varied between one and three. A single therapy session was necessary for 34 cases, two sessions for 13 cases, and three sessions for the remaining three  patients (Figure 6).

Figure (7): Patient satisfaction level.

The YAG laser's energy levels used for vitreolysis varied from 2.8–6.3 mJ, with the mean energy being 4.6 mJ.

Regarding patient satisfaction following YAG laser vitreolysis, 14% of patients reported complete success, 46% of patients reported significant success, 34% of patients reported partial success whereas 6% of the patients reported failure of the treatment (Figure 7).

When comparing the satisfaction level between patients with Weiss ring opacities vs those with mid-vitreal opacitie, we found that: patients with weiss ring opacities showed ; 25.9% complete success, 51.9% significant success, 18.5% partial success and 3.7% failure. Whereas patients with mid-vitreal opacities showed 39.1% significant success, 52.2% partial success and 8.7% failure of the treatment (Table 5).

Table (5): Patient satisfaction level in patients with weiss ring opacities vs mid-vitreal opacitie

IOP and BCVA (Log MAR) did not statistically differ before or up to six months following therapy (Table 6).

Table (6): The difference between BCVA (Log MAR) and IOP before and after surgery.

No complications occurred during the procedure or recorded in postoperative 6 months follow up period.