Interventional procedure overview of YAG laser vitreolysis for symptomatic vitreous floaters

Indications and current treatment

Vitreous floaters are microscopic clumps of collagen fibres in the vitreous that cast shadows on the retina, appearing as floaters. The most common cause of vitreous floaters is posterior vitreous detachment (PVD), when the posterior hyaloid face separates from the retina.

Vitreous floaters can be primary or secondary. Primary vitreous floaters originate from the vitreous body. Secondary floaters originate from outside the vitreous body, generally from proteins, amyloid or cells.

Vitreous floaters usually do not threaten vision and can be managed conservatively. When they do affect vision, treatment options include vitrectomy and vitreolysis with YAG laser.

What the procedure involves

This procedure aims to improve vision and reduce symptoms by removing or reducing the size of floaters.

The pupil is dilated and anaesthetic eye drops are administered. A specialised contact lens is placed on the cornea. Coaxial illumination is used. A laser microscope focuses on the front surface of the floater and creates short bursts of energy (nanosecond pulses). The laser energy heats the collagen and hyaluronic acid molecules in the floater, converting them into a gas, which then dissolves into the vitreous. It usually starts with a low level of energy, which is increased until it is high enough to destroy the floaters. The laser is stopped once all visually significant floaters are evaporated.

YAG laser vitreolysis is done as an outpatient procedure. Depending on the characteristics and numbers of floaters, more than 1 session may be needed.

Outcome measures

Contrast sensitivity is the ability to detect subtle differences in shading and patterns. It can be measured using the Pelli-Robson chart by finding the lowest contrast letters a person can read correctly. The chart uses a single large letter size (6/18 optotype), with contrast varying across groups of letters. A Pelli-Robson score of 2.0 indicates normal contrast sensitivity of 100%. Scores less than 2.0 signify poorer contrast sensitivity. Pelli-Robson contrast sensitivity score of less than 1.5 is consistent with visual impairment and a score of less than 1.0 represents visual disability.

Visual acuity refers to a person's ability to see small details and reflects the clarity or sharpness of vision. Visual acuity is often measured according to the size of letters viewed on a Snellen chart, or the size of other symbols, such as the Landolt C or the E Chart. 'Normal' distance visual acuity is often quantified using the Snellen chart, at 6/6 (metre), 20/20 (feet). This means the person can read at 6 metres (or 20 feet) what someone with normal vision can read at 6 metres. A vision of 6/12 means the person can see at 6 metres what someone with normal vision can see at 12 metres, so representing worse vision. A visual acuity of 6/6 can also be expressed as 1.00 decimal and is equivalent to 0.0 logMAR (with higher logMAR values representing worse vision). The Early Treatment Diabetic Retinopathy Study (ETDRS) letter score is another means of testing visual acuity, in which 85 letters approximates 6/6 Snellen, with lower letter scores representing worse vision.

The National Eye Institute Visual Function Questionnaire (NEI VFQ) measures visual functioning in 11 domains: general vision, ocular pain, near activities, distance activities, vision-specific social functioning, vision-specific mental health, vision-specific role difficulties, vision-specific dependency, driving, colour vision, and peripheral vision. It has different versions, such as 25-item and 39-item versions. Each domain is scored from 0 to 100 points, with higher scores representing better functioning.

The State-Trait Anxiety Inventory (STAI) is a psychological inventory based on a 4-point Likert scale (from 0 to 3 points) and consists of 40 questions. The STAI measures 2 types of anxiety – state anxiety (anxiety about an event) and trait anxiety (anxiety level as a personal characteristic). Higher total scores indicate greater anxiety levels.