Ординатура / Офтальмология / Английские материалы / Moorfields Manual of Ophthalmology_Jackson_2007

Side effects and precautions Occlusion of the nasolacrimal duct may help to reduce the incidence of the side effects shown in the Table 7.1. For drug use in pregnancy, see page 702.

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Pharmacology of intraocular pressure-lowering drugs

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Chapter7GLAUCOMA

History

History

Ask about:

■Active problems, mode of presentation, and the patient’s worries.

■Presenting IOPs, if recorded at source of referral.

■Past ophthalmic history (e.g. uveitis, trauma). Surgery and complications, especially glaucoma, cataract, retinal procedures, and refractive surgery (alters corneal thickness and IOP measurements). Refractive error. Contact lens usage (may be affected by surgery and influence choice of medication).

■Medical history for conditions linked with glaucoma (hypotensive crises, migraine, Raynaud’s phenomenon) and those affecting the choice of medication (bradyarrhythmias, asthma, renal stones, sickle cell disease).

■Medication used previously and currently, especially: systemic beta blockers; other antihypertensive medication; systemic, inhaled, or topical steroids; and bronchodilators. Any side effects of ocular medications.

■Ethnic/racial group and preferred language.

■Family history of glaucoma or blindness.

■Occupation. Are driving authorities aware of the diagnosis?

■Social support and care arrangements.

Optic Disc Examination

Background Identification of characteristic optic disc changes enables a diagnosis of glaucoma to be made, and the detection of disease progression.

Examination Measure the vertical disc size by reducing the height of the focused light beam to the same size as the disc. Note the beam height (mm) and lens used (magnification factor). Measure the cup-to-disc ratio (CDR). Normal CDR varies with disc size (Fig. 7.1). Assess the rim for focal thinning or notches. Check the ‘ISNT rule’: normal rim thickness inferior > superior > nasal > temporal.

Other features : tilting, parapapillary atrophy, disc haemorrhages, and ‘bayoneting’ (double angulation) or ‘baring’ (exposing) of blood vessels. Nerve fibre layer defects are best seen using either white or red-free light, carefully focused, particularly in superotemporal or inferotemporal nerve fibre bundles. Record all observations. Asymmetric CDR is suspicious of glaucoma if the discs are the same size.

Imaging A baseline record of disc appearance (photograph or scanning laser ophthalmoscope image) aids detection of change.

Vertical disc diameter measured with 78 D lens

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Gonioscopy

Gonioscopy

Background Examine the drainage angle of all patients with suspected glaucoma or ocular hypertension, both at diagnosis and periodically thereafter.

Equipment Goldmann oneor two-mirror lenses are steeper than corneal curvature (K) and require a coupling medium. Fourmirror lenses (Zeiss, Posner, Sussman) are flatter than K.

Steeper-than-K lenses provide a stable, clear view and are easier to use. They can be used to perform dynamic (compression) examination. Four-mirror lenses are superior for difficult dynamic examinations.

Examination Dim ambient illumination and ensure adequate topical anaesthesia. Apply a low-viscosity coupling fluid (e.g. Viscotears or hypromellose 0.5%) to the Goldmann lens. Use a narrow slit beam, 1 mm long to avoid pupil constriction and widening of the angle. Identify Schwalbe’s line at the apex of the corneal wedge reflex (Fig. 7.2). The trabecular meshwork lies immediately posterior to this. Estimate the geometric width of the angle (in degrees) between the surface of the trabecular meshwork and a line tangential to the peripheral one-third of the iris. Note the profile of the iris (plateau, concave, regular, steep), its first point of contact with corneoscleral coat and its point of true insertion (modified Spaeth classification). The angle width is often recorded as 1 = 10 degrees, 2 = 20 degrees. Care is necessary with shorthand notation, as this may lead to confusion with the inferior grading system that describes the angle structures visible (I, II, III and IV; IV being the widest, most open angle). The angle structures visible are heavily influenced by orientation of the eye and gonioscope. It is preferable to include a short explanatory note.

After assessing the angle width, widen the beam and examine the four quadrants again for the presence of pigment (intratrabecular, diffuse or geographic, blotchy deposits on trabecular surface), Sampaolesi’s line (granular pigment on Schwalbe’s line), and abnormalities such as neovascularization, membranes, angle recession or iridodialysis. Peripheral anterior synechiae are identified by using a Goldmann lens; ask the patient to look towards the mirror and gently indent the cornea with the edge of the lens. If the angle does not open, perform indentation gonioscopy with a four-mirror lens to differentiate between appositional and synechial angle closure. A normal angle is shown on page 297.

Intraocular pressure (IOP)

Intraocular Pressure (IOP)

Background IOP is the cardinal modifiable risk factor for glaucoma. The prevalence of glaucoma rises with IOP but 30– 50% of cases have normal IOP. Mean IOP rises with age in Caucasians, and tends to be highest in the morning. Glaucoma is associated with greater IOP fluctuations. IOP is measured by flattening or indenting the cornea, hence corneal abnormalities (scars, extremes of thickness) may significantly influence results. Inaccuracies of ±6 mmHg may occur at the extremes of corneal thickness. The use of correction tables and formulae to adjust for the effect of corneal thickness is controversial.

Equipment Goldmann (routine use), Perkins applanation tonometer (for immobile patients), and Tonopen (may offer advantages in scarred/abnormal corneas).

Goldmann tonometer Ensure adequate corneal anaesthesia and that the prism is clean and free from contaminants. Avoid excess fluorescein. If corneal astigmatism is >3.0 D, rotate the prism so the minus cylinder axis on the prism graduation corresponds to the red mark on the prism holder. If necessary, hold the lids against the orbital rim but avoid pressure on the globe. Be aware, breath-holding increases IOP. If the mires pulsate, measure at the midpulse amplitude. Note the time of measurement.

Calibration : mount the tonometer on the slit lamp with the prism inserted. Fit the calibration bar into the socket on the side of the tonometer. Graduations on the bar correspond to different IOPs: centre (0 = 0 mmHg), second (2 = 20 mmHg), third (6 = 60 mmHg). The longer part of the calibration bar is on the side opposite the prism (Fig. 7.3). Dialing the appropriate reading should cause the bar to pivot with adjustments ±2 mmHg either side of the correct reading.