Lasers

Lasers serve many functions in ophthalmology, such as the coagulation of retinal vessels, moulding of the corneal stroma and the creation of incisions. Lasers are composed of a source of energy, a medium which determines the wavelength and an optical resonator which amplifies light.

Ophthalmic excimer laser for refractive surgery By Philos2000, CC BY-SA 3.0 .

The laser hazard classification (VDE 0837) categorises these therapeutic lasers as class 4, on a scale of 1-4 where 1 is relatively harmless.

Applications

Effect	Laser	Application
Photo-ionization	Nd:YAG (1064nm)	Posterior capsulotomy Peripheral iridotomy
Photocoagulative	Frequency doubled Nd:YAG (532nm) Krypton red (647nm) Diode (810nm) Argon blue-green blue 488nm green 514nm	Diode is used mainly for retinopathy of prematurity and ciliary body treatment in glaucoma Argon is commonly used for panretinal coagulation (in retinal vascular diseases), macular treatment (macular oedema) and iridoplasty Double YAG is used in trabeculoplasty (SLT) Krypton red is used to treat subretinal neovascular membranes
Photochemical	Excimer	Corneal ablation during laser refractive surgery

Different molecules react to different wavelengths of light. For example, xanthophyll of the macula absorbs blue light (450-495nm).

Systemic Medications and the Eye

Many systemic medications have side effects which involve the eye. The important associations are summarised here.

IOP Related

Rise

Topiramate (can result in bilateral acute angle-closure secondary to ciliary body swelling
Steroids

Lower

Cannabinoids and alcohol can transiently lower IOP

Cataract Inducing

Steroids
Amiodarone
Allopurinol
Busulphan
Chlorpromazine (a thiazide): fine yellow-brown granules on anterior lens capsule
Gold: innocuous, anterior capsular deposits in 50% of patients

Vortex Keratopathy

Vortex keratopathy (also known as corneal verticillata) is a corneal deposition that has characteristic associations.
Fabry’s disease.
Amiodarone
Chloroquine
Tamoxifen
Chlorpromazine

Corneal verticillata (whorl-like pattern of cream coloured lines in the cornea) in a patient with Fabry’s disease. Alessandro P Burlina, CC BY 2.0 .

Retina Related

Cystoid Macular Oedema

Latanoprost
Adrenaline
Glitazones
Nicotine

Bull’s-eye Maculopathy

Chloroquine (also causes renal toxicity and corneal verticillata)

Crystalline Maculopathy

Tamoxifen

Optic Nerve Related

Ethambutol
Chloramphenicol
Amiodarone
Vigabatrin (also associated with binasal visual field defects)
Isoniazid

Sutures

Different ocular structures are sutured using different materials

Suture	Type	Tissue
Silk	Non-absorbable	Eyelids and sclera
Polyglactin 910 (VICRYL®)	Absorbable	Conjunctiva, cornea, and extra-ocular muscles
Nylon	Non-absorbable	Cornea, sclera and limbus
Polypropylene (PROLENE®)	Non-absorbable	Iris
Polyglycolic acid (DEXON®)	Absorbable	Limbus