Ординатура / Офтальмология / Английские материалы / Moorfields Manual of Ophthalmology_Jackson_2007

Endothelial rejection Carries potential for irreversible damage to the endothelium and subsequent corneal decompensation (Fig. 5.35). Two patterns occur:

■Focally progressive (25–45% of rejections): begins at the graft host junction. Cytotoxic lymphocytes from marginal vessels then form an advancing demarcation line (Khodadoust line) with clear cornea centrally and stromal oedema behind it. KPs, cells and flare are present. The differential diagnosis includes diffuse rejection, suture abscess, and epithelial ingrowth (usually occurs later and without uveitis or stromal swelling behind the line).

■Diffuse (25–45% of rejections): tends to occur later than focally progressive cases. Variable severity. Cytotoxic lymphocytes from the uvea result in AC cells and flare. KPs are confined to the graft endothelium. The graft may be oedematous or remain clear if there is only mild rejection. The differential diagnosis includes anterior uveitis (KPs not confined to graft, more AC cells), herpes simplex keratitis, raised IOP (no new KPs, AC quiet). Treat as follows:

1.Admit if compliance with treatment is likely to be poor.

2.Intensive topical steroids (e.g. G. prednisolone 1.0% hourly 0600 to 2400 hours, then Oc. dexamethasone 0.1% nocte, or hourly day and night for severe cases).

CORNEA 5 Chapter

Anterior Segment Trauma

Background Common traumatic ocular injuries described elsewhere include corneal abrasion (p. 150), angle recession (p. 313), uveitis (p. 335), retinal commotio, tears and ruptured

globe (p. 551), and optic neuropathy (p. 661). If an injury results from an alleged assault or workplace injury, carefully document the timing and circumstances of the injury and measure or preferably photograph all wounds. Consider tetanus prophylaxis.

Conjunctival laceration

Look for a laceration with rolled or retracted edges and foreign bodies (FBs). Prolapsed Tenon’s capsule appears white and oedematous. Brown pigment suggests a scleral laceration and prolapse of uveal tissue. Be aware of the potential for involvement of the extraocular muscles or of a scleral perforation obscured by subconjunctival haemorrhage. Remove FBs and prolapsed Tenon’s capsule. Small, clean conjunctival lacerations require no suturing. Prescribe Oc. chloramphenicol q.d.s. 1 week. Larger (>15 mm,) more complex lacerations may require suturing with interrupted 8/0 Vicryl. Avoid suturing the plica or caruncle. Be careful to appose the conjunctiva rather than Tenon’s capsule. If sutured, review at 1 week.

Corneal laceration

History Pain, red eye, foreign body sensation, watering eye, and reduced vision.

Examination If the globe is ruptured, pressure on the globe may risk further ocular injury, so avoid tonometry, gonioscopy, and indented fundoscopy. Note the site, location, extent, and depth of the corneal wound. Siedel testing (p. 147) may be negative with full-thickness shelving wounds that self-seal. Note the anterior chamber depth, cellular activity, and any hyphaema. Look for pupil irregularity or iris prolapse through the wound. Traumatic mydriasis is common. Test for an RAPD due to traumatic optic neuropathy or retinal detachment. The IOP may be low, normal, or elevated. Dilate and examine the posterior pole and periphery.

Management

CORNEA 5 Chapter

Anterior segment trauma

■Full thickness : apply a protective shield and prescribe antiemetic if required. Treat clean, self-sealing, full-thickness lacerations with prophylactic oral antibiotics (ciprofloxacin 750 mg b.d. p.o. for adults; co-amoxiclav t.d.s. for children)

and topical G. chloramphenicol 0.5% q.d.s. for five days. Treat minimally leaking lacerations with a bandage contact lens and G. unpreserved chloramphenicol 0.5% q.d.s. Leaking fullthickness lacerations require debridement and suturing (10/0 Nylon) in theatre. Admit, nil by mouth, except for prophylactic oral antibiotics. For more extensive damage, treat as a ruptured globe (p. 553).

Follow-up Review daily until the epithelium heals. Stop topical and oral antibiotics at 1 week if settled. Explain the symptoms of retinal detachment, endophthalmitis, and sympathetic ophthalmia, with advice to attend promptly if these develop.

Contact Lenses

Background The fitting and review of contact lenses for low refractive errors is predominantly carried out by community optometrists. In the UK, hospitals generally review contact lens problems or fit lenses for more complex indications such as:

■Refractive: high myopia (>10 D); aphakia; postcorneal graft; anisometropia; anisekonia; high hypermetropia (>5.00 D); irregular astigmatism (keratoconus); postinfective keratitis; postrefractive surgery.

■Therapeutic: ‘bandage lenses’ are used for pain relief by covering rough or unstable epithelium, to mechanically protect the ocular surface, maintain corneal hydration, or tamponade leaking wounds. Common examples include recurrent erosion syndrome, bullous keratopathy, keratinized lids, misdirected eye lashes, and corneal exposure.

■Cosmetic: aniridia; scars; albinism; iris coloboma; unable to wear glasses due to facial deformity.

Abbreviations

■RGP rigid gas permeable (hard) contact lens.

■BVD back vertex distance.

■BVP back vertex power.

■BOZR back optical zone radius (back radius).

■TD total diameter (diameter).

History Ask about:

1.Lens type:

■Material : RGP or soft. Soft lenses are usually hydrogel but silicone hydrogel (SiH) and silicone rubber (SiR) are sometimes used.

■Size : corneal or scleral.

■Mode of wear: daily disposable, frequent replacement (e.g. weekly, monthly or 3 monthly) or longer use.

2.Pattern of wear: average wearing time per day (in hours) and number of days per week, any overnight wear and if so the number of nights, maximum wearing time per day, contact lens wearing time on the day of consultation and/or if the lens

CORNEA 5 Chapter

209

Chapter5CORNEA

210

Contact lenses

Contact lenses

Central alignment with slight pooling

Edge clearance with tear meniscus

Fig. 5.36: Rigid contact lens fitting example.

document the VA. The final contact lens power will be the sum of contact lens power + spectacle power. If the latter is ≥4.0 D, correct for BVD using standard tables.

Special situations

■High myopia : patients usually have large flat corneas; use lenses with a high oxygen transmissibility (e.g. Boston XO) or high water content. Silicone hydrogels are currently not available in high powers.

■Adult aphakia : negative RGP lenses may drop so negative edge carriers, high axial edge lift designs, larger diameters, etc. are frequently needed. Use lenses with high oxygen transmissibility (e.g. Boston XO) or high water content. Silicone hydrogels are currently not available in high positive powers.

■Keratoconus : consider corneal topography, degree of corneal toricity, and degree of ametropia. The corrected VA must be balanced with lens tolerance and effect on corneal integrity. Start with an RGP designed for keratoconus (e.g. Woodward KC3 or Rose K). Look for a good fit with fluorescein but some apical touch is likely. With highly protrusive or markedly decentred cones, some compromise is likely, but look for a lens that offers good VA, stays in on most gaze excursions, avoids indenting the cornea, and minimizes corneal contact. Figures 5.37–5.40 show examples of lens fits and management options in keratoconus.

■Following penetrating keratoplasty : use the flatter K for initial estimate of base curve. Bespoke multi-curve RGP lenses frequently 10 mm to 12 mm in diameter are usually used. ‘Reverse-geometry’ RGP lenses are sometimes required for