Cornea (Wills Eye Institute Atlas Series)

Keratoconus 103

● Later ■ Vogt striae: fine vertical deep stromal tension lines that disappear temporarily with digital pressure applied to the limbus ( Fig. 4-1I) ■ Abnormal “oil droplet” red reflex ■ Rizzuti sign: conical light reflection on the nasal limbus when light is shone from the temporal side ■ Variable corneal scarring, depending on severity ( Fig. 4-1J–O ). May develop an ele vated apical nodule ( Fig. 4-1P, eFig. 4-1I–L) ■ Munson sign: bulging of the lower eyelid in downgaze ■ Acute hydrops: severe corneal edema resulting from a tear in Descemet mem brane ( Fig. 4-1Q–U, eFig. 4-1P and Q) Associated Problems ● Ocular: vernal disease, blue sclera, retinitis pigmentosa, Leber congenital amaurosis, floppy eyelid syndrome ● Systemic: Down syndrome, sleep apnea, Ehlers–Danlos syndrome, Apert syndrome, ocular allergies, osteogenesis imperfecta Differential Diagnosis ● Pellucid marginal degeneration: inferior peripheral corneal thinning with protrusion of the cornea above the area of maximal thinning Treatment ● Mild cases: glasses and soft contact lenses ● Moderate cases: rigid gas-permeable con tact lens (RGPCL), hybrid lens, or scleral lens ● Severe and contact lens–intolerant cases: ■ Lamellar keratectomy with a blade or excimer laser for anterior nodules ■ Placement of intracorneal ring segments ■ Corneal stromal addition procedure ■ Deep anterior lamellar keratoplasty ■ Penetrating keratoplasty ■ Epikeratoplasty and thermokeratoplasty are rarely performed.

■ Refractive surgery in patients with keratoconus is unpredictable and generally not recommended, except under special protocols. ● Acute hydrops: generally resolves on its own over weeks to months ■ Sodium chloride 5% drops q.i.d. and/or sodium chloride 5% ointment once daily to q.i.d. ■ Photophobia may be helped by cycloplegia (e.g., cyclopentolate 1% t.i.d.). ■ Consider an aqueous suppressant if intraocular pressure is somewhat elevated (e.g., brimonidine 0.1% b.i.d. to t.i.d.). ■ Intracameral air, or nonexpansile concen trations of SF 6 or C 3 F 8 , may be helpful in resolving edema more quickly than medical therapy alone but has risks, including elevated intraocular pressure and cataract formation. ■ Full-thickness corneal suturing in an attempt to close the gap in Descemet mem brane may be helpful in resolving edema more quickly than medical therapy alone but has risks, including persistent leaking from the suture tracks. ● Corneal cross-linking: indicated for pro gressive disease in eyes with sufficient corneal thickness and minimal to no corneal scarring with the objective of halting progression. Gen erally performed by placing riboflavin drops on the cornea and then treating the cornea with ultraviolet light to “strengthen” the cornea to prevent worsening of keratoconus. Approved by the U.S. Food and Drug Administration to treat progressive keratoconus and postrefrac tive surgery ectasia. Short- and medium-term results are promising for stopping progres sion. Best results are obtained when treating keratoconus at a relatively early stage. Prognosis ● Most patients do well with RGPCLs or scleral lenses. Corneal cross-linking is usually successful at preventing progression. The success rate with corneal transplantation in keratoconus is high.

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