Vascular Disease

The presence of systemic vascular disease should be ascertained during the preoperative evaluation to determine the level of risk associated with refractive surgery. We discuss hypertension and diabetes mellitus, the most common vascular diseases. Other vascular conditions must be considered on an individual basis, with special attention to potential intraoperative and postoperative complications.

HYPERTENSION Hypertension in refractive candidates is usually mild, well controlled, and rarely associated with significant ocular disease.

Preoperative Considerations

DIABETES MELLITUS Patients with diabetes may be good candidates for refractive procedures if the diabetes is well controlled and the patient’s ocular health is good.

Preoperative Considerations

Surgical Considerations

Postoperative Considerations

• slower wound healing (because of lower rates of corneal re-epithelialization)
  
• refractive shifts (require strict blood glucose control and postponement of enhancement procedures until the refractive shifts are stabilized)
  
• reduced rate of tear secretion and increased risk of dry eye and related symptoms (may require lubricant therapy)

Autoimmune or Collagen Vascular Diseases

This group includes a wide spectrum of diseases with most refractive patients exhibiting minimal signs or symptoms. Preoperative evaluation of the severity of the autoimmune disease as well as the number of medications required is important.

Preoperative Considerations

• decreased tear production because of lymphocytic infiltration and destruction of the lacrimal glands (most collagen diseases)

Surgical Considerations

• absolute contraindications (because of abnormal collagen cross-linking and abnormal and often unpredictable healing processes)
  
  
  
  • scleroderma
    
  • Marfan’s syndrome
    
  • osteogenesis imperfecta
    
  • Ehlers-Danlos syndrome
    
  • documented history of keloid formation [only for procedures like radial keratotomy (RK) and photorefractive keratectomy (PRK), in which there is a prolonged healing process, to prevent permanent haze formation]
  
  
• moderate relative contraindications (approach with extreme caution and only after complete patient education about the potential risks of surgery and the long-term visual outcome)
  
  
  
  • rheumatoid arthritis
    
  • systemic lupus erythematosus (SLE)
    
  • Wegner’s granulomatosis
    
  • polyarteritis nodosa
    
  • relapsing polychondritis
  
  
• low relative contraindications (recommend surgery only after complete patient education about possible effects on the healing process and the long-term visual outcome)
  
  
  
  • multiple sclerosis (warrants discussion on long-term prognosis for visual function)
    
  • conditions that cause iridocyclitis, including ankylosing spondylitis, Reiter’s syndrome, and Crohn’s or ulcerative colitis (control the condition or wait for latency prior to surgical intervention)

Postoperative Considerations

• increased risk for poor or abnormal healing processes of the ocular surface

Infectious Diseases

Infectious diseases should be treated or stable prior to proceeding with an elective refractive procedure.

HUMAN IMMUNODEFICIENCY VIRUS AND AQUIRED IMMUNODEFICIENCY SYNDROME Many human immunodeficiency virus (HIV)-positive patients are quite healthy and have normal ocular status so they may still be good candidates for refractive surgery.

Preoperative Considerations

Surgical Considerations

• need for universal precautions (the Centers for Disease Control provides guidelines) (although no documented cases of transmission of HIV from the tear film or through airborne vaporized particles from laser ablation)

Postoperative Considerations

• need for prophylaxis against postoperative bacterial or herpetic viral infection [fluoroquinolone, as well as trifluridine (Viroptic, Allergan, Irvine CA)], depending on the patient’s immune status.

HERPES SIMPLEX Herpetic keratitis often recurs, and residual corneal scarring affects visual performance so careful evaluation and education of these patients are essential.

Preoperative Considerations

• a complete ocular examination and history regarding previous ocular infection
  
• patient education about proper postoperative hygiene (to reduce risk of ocular contamination and infection for patients with a positive systemic history)

Surgical Considerations

HERPES ZOSTER AND VARICELLA ZOSTER

Herpes zoster and varicella zoster recur less often but may be confused with herpes simplex infections so precautions are still required.

Preoperative Considerations

• see Herpes Simplex

Surgical Considerations

• latent systemic zoster infection (a relative contraindication ; advisable to delay surgical correction until the systemic disease is controlled)
  
  
  
  • possible initiation of prophylactic systemic antiviral therapy 1 week before surgical intervention
    
  • need for universal precautions to prevent contamination (although no documented cases of transmission of virus during laser ablation)
    
  • increased risk for reactivation and transmission of the viral disease by incisional procedures

BACTERIAL INFECTIONS

Preoperative Considerations

Surgical Considerations

• possible postponement of elective surgical correction until signs of systemic disease abate and refractive stability and patient comfort return to normal
  
• high risk for sedative cross-reaction with systemic antibiotics

Postoperative Considerations

• systemic infection effects on refractive error
  
• rare medication effects on the refractive error (many medications may cause changes in accommodation)
  
• effect of sinusitis on patient comfort and tear film (decongestants often decrease normal tear production)

Endocrine and Metabolic Disorders

Few endocrine disorders have a dramatic effect on the eyes and refractive error. Abnormal thyroid function and the intricate hormonal changes associated with pregnancy and lactation are the most common endocrine conditions that may have a notable effect on refractive error and the postoperative healing process. These conditions are discussed in this section.

THYROID EYE DISEASE Patients with mild thyroid eye disease but without significant ocular complications may still be reasonable candidates for refractive surgery.

Preoperative Considerations

• signs or symptoms of thyroid eye disease (displayed by hyperthyroid, hypothyroid, or euthyroid patients)
  
  
  
  • exophthalmos
    
  • lid lag
    
  • exposure keratitis
    
  • diplopia
  
  
• binocular status (if binocular abnormalities are noted, educate the patient about possible progression and the potential need for prismatic correction to maintain single binocular vision)
  
• tear film status (increased likelihood of decreased aqueous secretion secondary to lymphocytic infiltration and destruction of the lacrimal gland)

Surgical Considerations

• refractive instability (an absolute contraindication)

Postoperative Considerations

PREGNANCY AND LACTATION Patients’ refractive stability is often unpredictable during pregnancy and lactation.

Surgical Considerations

• temporary postponement of surgical correction (until after the pregnancy or, if the mother is breast feeding, until three months after weaning)
  
• potential systemic adverse effects of sedatives and topical prophylactic therapies on the fetus

Postoperative Considerations

• abnormal wound healing
  
• refractive instability
  
• tear films abnormality

Epithelial Disorders

The surgeon and clinician should document various disorders of the corneal epithelium before undertaking surgical intervention. Epithelial basement membrane dystrophy (EBMD) or other epithelial defects may lead to poor or prolonged healing and increased risk for epithelial ingrowth or epithelial defects.

These three processes may lead to patient discomfort during the early postoperative period and increase the risk that further surgery will be necessary. Some surgeons and patients may prefer refractive procedures such as PRK if epithelial disease is present, to prevent postoperative complications and, if possible, treat the ocular surface disease.

EPITHELIAL BASEMENT MEMBRANE DYSTROPHY EBMD is an abnormal maturation and production of epithelial basement membrane with associated abnormal epithelial adhesions.

Preoperative Considerations

• small, cystic, subepithelial, isolated or linear arrangement of subtle opacities (may be observed by focal illumination or high-lighted by retroillumination)
  
• negative staining patterns over abnormal basement membrane

Surgical Considerations

RECURRENT CORNEAL EROSION Recurrent corneal erosions (RCEs) are most commonly caused by traumatic injury or other ocular surface disorders that affect the adhesive characteristics of epithelium and its basement membrane to Bowman’s membrane.

Preoperative Considerations

Surgical Considerations

• poor epithelial adherence in the area of the keratectomy edge or incision
  
• safety of refractive range (for removal of the area of damaged weak epithelium and basement membrane with PRK)
  
• preference for PRK or PTK (phototherapeutic keratectomy) over LASIK especially for low myopia with anterior basement membrane dystrophy (allows formation of new epithelial basement membrane and development of normal attachments to the underlying Bowman’s membrane or anterior stroma)

Postoperative Considerations

• epithelial ingrowth
  
• intermittent corneal defects
  
• poor tear film stability
  
• patient discomfort

PANNUS OR VASCULARIZATION Corneal hypoxia or inflammation often leads to corneal micropannus or vascularization anterior to the limbus. This vascularization is common in those who overwear their contact lenses or in the presence of other ocular surface diseases.

Preoperative Considerations

Surgical Considerations

Surgical Considerations

• need for a lamellar or full thickness corneal graft in advanced stages to decrease the fibrillar material that has replaced Bowman’s membrane (an absolute contraindication for lamellar refractive surgery)

Stromal Disorders

Most stromal disorders are relative contraindications for refractive surgery, though patients with some stromal dystrophies may benefit to some degree from lamellar surgery. A few stromal disorders, including ectatic disorders such as keratoconus are absolute contraindications for refractive surgery.

KERATOCONUS The etiology of keratoconus is unknown, but the progressive thinning of the central cornea associated with this disorder presents obvious challenges to successful refractive surgery.

Preoperative Considerations

THIN CORNEAS Corneal thickness measurements are critically important for determining risk for both incisional and lamellar refractive surgery. The surgeon must both rule out preoperatively and prevent the development postoperatively of corneal ectasia.

Preoperative Considerations

• assessment of corneal thickness by pachymetry (average corneal thickness in normal myopic patients = 545−555 μm)
  
  
  
  • minimization of postoperative risk for iatrogenic keratoconus (from lamellar surgery)
    
  • minimization of postoperative risk for full-thickness perforations and endophthalmitis (from incisional surgery)
  
  
• estimated postoperative stromal bed thickness (for lamellar surgery)
  
  
  
  • ideal = ≥ 300 μm
    
  • borderline = 250 μm
    
  • absolute minimum = 200 μm
  
  
• variations in lamellar flap thickness (flat corneal curvature may result in an abnormally thin cap)

Surgical Considerations

• incisional surgery
  
  
  
  • number of incisions (affected by corneal thickness)
    
  • corneal thickness determines depth of incisions (perforations at any location during surgery suggest excessive incisional depth)
  
  
• lamellar surgery
  
  
  
  • estimation of postoperative corneal thickne’ss (preoperative corneal thickness- thickness of stromal tissue ablated), which determines ablation profile and multizone vs. single zone considerations
    
  • thin cap or a perforation in the corneal cap

Postoperative Considerations

STROMAL OPACIFICATION OR SCARS Stromal scars may be insignificant if completely off the visual axis or very significant if within the visual axis. Scars in the visual axis may cause a loss of BCVA and often lead to a suboptimal postoperative result.

Preoperative Considerations

Postoperative Considerations

• wound healing
  
  
  
  • irregular healing and/or increased fibrosis (effect of opacity or fibrosis depth)
    
  • irregular healing at fibrosis location (effect of opacity or fibrosis location)
    
  • potential increase in fibrosis density if incision passes through fibrosis (effect of opacity or fibrosis density)
  
  
• visual acuity (development of irregular astigmatism or surface changes)
  
  
  
  • irregular healing with potential irregular astigmatism (effect of opacity or fibrosis depth)
    
  • effect of opacity or fibrosis density (see above)
  
  
• partial-thickness lamellar graft (may eliminate the opacity and enhance unaided visual acuity)

STROMAL DYSTROPHIES The three primary stromal dystrophies (lattice, macular, granular) are not contraindications for refractive surgery but may pose difficulty in both presurgical evaluation and surgical performance.

Preoperative Considerations

• evaluation of cornea to identify stromal dystrophy
  
• effects of stromal dystrophy
  
• refractive error (more difficulty getting a refractive endpoint)
  
  
  
  • visual acuity (BCVA may be reduced because of stromal opacities)
    
  • potential for reduced preoperative BCVA
  
  
• patient education
  
  
  
  • risks of surgery
    
  • diagnosis of stromal dystrophy
    
  • potential effect on visual acuity
    
  • risk for disease progression and long-term visual acuity

Surgical Considerations

Postoperative Considerations

• delay in healing response
  
• initial reduction in visual acuity because of poor healing response
  
• ocular surface abnormalities

Endothelial Disorders

Although less common, endothelial corneal dystrophies comprise a complex group of conditions that may significantly impact the results of refractive surgery. Patients should be carefully screened for these conditions before undergoing any refractive discussion.

ENDOTHELIAL GUTTATA OR FUCHS’ DYSTROPHY A few endothelial guttata are commonly found in patients older than 60 years of age and represent a premature aging process involving the corneal endothelium. Fuchs’ dystrophy is the association of guttata with frank corneal edema indicating endothelial decompensation (an absolute contraindication to refractive surgery).

Preoperative Considerations

• dewdrop or wartlike endothelium excrescences in the central cornea
  
  
  
  • indicates an overall weakness of the corneal endothelium
    
  • must be differentiated from endothelial pigment that is often deposited in the same location
    
  • endothelial cell counts should be considered prior to any refractive procedure [if >10 guttata or if an intraocular procedure, such as phakic intraocular lens (IOL) insertion or clear lens extraction, is being considered]
  
  
• presence and status of corneal edema

Surgical Considerations

• good visual acuity and good prognosis for corneal integrity (then not a contraindication for refractive surgery)
  
• presence or severity of guttata

Postoperative Considerations

• visual acuity (edema and excessive corneal hydration may produce a myopic shift)
  
• corneal edema (minimize with hypertonics)
  
• damage to ocular surface integrity
  
  
  
  • artificial tears or lubricating ointment
    
  • bandage hydrogel lens (if necessary)

Other Corneal Disorders

Preoperative identification of other rare corneal dystrophies is important because they may impact surgical planning and results of refractive procedures.

Preoperative Considerations

• examination to exclude posterior polymorphous dystrophy and iridocorneal endothelial dystrophies

Surgical Considerations

• absolute contraindications
  
  
  
  • posterior polymorphous dystrophy
    
  • iridocorneal endothelial dystrophies
    
  • infectious keratitis with active herpetic infection or active fungal infection
  
  
• relative contraindications
  
  
  
  • active bacterial infection (postpone surgery until the ocular surface is clear)
    
  • past history of herpetic infection (surgery carries a risk of reactivation; provide prophylactic treatment)

Postoperative Considerations

Eyelids

Eyelid abnormalities must be evaluated, documented, and managed properly to ensure the best possible surgical outcome. Ptosis, blepharitis, and appositional or meibomian gland disorders may affect patients’ intra- and postoperative status and are discussed in the following sections.

PTOSIS Mild ptosis (eyelid droop < 1 mm should be documented whenever noted preoperatively.

Preoperative Considerations

• proper assessment and documentation of preexisting ptosis (useful as a reference if its preexisting status is questioned after surgery)
  
• history of lid surgery or trauma (may indicate reason for ptosis and document that refractive procedure did not cause it)
  
• decreased levator function (may be associated with poor lid closure and exposure after refractive procedures)
  
• narrowing of the palpebral fissure (more difficult access to the eye for procedures)

Surgical Considerations

• proper and careful speculum placement (may cause further damage to the lid muscles, particularly if there was recent lid surgery)

Postoperative Considerations

• temporary ptosis (levator function usually returns within a few days but necessitates education of patient about cause and duration)
  
• permanent but rare ptosis (may warrant surgical repair for the following reasons)
  
  
  
  • cosmetically unacceptable
    
  • incomplete lid closure causing exposure keratitis
    
  • reduction of visual field or blocking of visual access by lid

BLEPHARITIS Blepharitis is a very common eyelid condition often associated with dry eyes and meibomian gland dysfunction.

Preoperative Considerations

Postoperative Considerations

• incisional surgery
  
  
  
  • endopthalmitis induced by corneal perforation (treat aggressively)
    
  • corneal ulceration (treat aggressively with fluoroquinolones and monitor daily)
  
  
• lamellar surgery
  
  
  
  • intrastromal keratitis caused by bacterial endotoxin (treat with topical antibiotics, steroids, or both; usually clears within a few weeks, even if left untreated)
    
  • corneal ulceration (treat aggressively with fluoroquinolones)

MEIBOMIAN GLAND DYSFUNCTION Abnormal production, constitution, or secretion of lipid from the meibomian glands characterizes meibomian gland dysfunction (MGD).

Preoperative Considerations

• indentification of chalazion

Surgical Considerations

• presence of chalazion (an absolute contraindication)
  
  
  
  • may alter corneal structure and refractive status
    
  • may affect patient comfort during and after surgery
    
  • treat appropriately before surgical intervention
  
  
• careful speculum placement to avoid excess lipid excretion or patient discomfort
  
• proper irrigation to eliminate lipid deposits in the lamellar interface in LASIK and PRK

Postoperative Considerations

• ocular surface inflammation
  
• mild intrastromal keratitis
  
• patient discomfort

Conjunctival Abnormalities

Preoperative Considerations

Extraocular Muscles

Phorias and tropias present an interesting challenge to the refractive surgeon because they are often corrected with a prism in the patient’s glasses. Patients often assume that the refractive procedure can also eliminate this prism, which is not possible. Preoperative counseling and potential treatment of the phoria or tropia is required.

Preoperative Considerations

Postoperative Considerations

• aggravation of the binocular status of some patients can result in subjective or objective diplopia
  
• reduction or elimination of certain binocular problems by elimination of the refractive error for some patients
  
• postoperative diplopia secondary to removal of prismatic or accommodative effect of the spectacle lens with tropia
  
  
  
  • visual therapy (if indicated)
    
  • prismatic spectacle correction
    
  • surgical correction of the tropia (misalignment) in rare cases

Large Pupils

Preoperative Considerations

• evaluation of pupil size (using scotopic and photopic illumination, to avoid postoperative complaints about glare)
  
• choice of ablation zone of the laser (should be at least as big as the scoptic pupil size)
  
• preoperative perception of glare (thorough history with and without correction)
  
• patient counseling about the risk of postoperative glare

Surgical Considerations

• proper alignment of the visual axis and the pupil (essential to successful surgical and visual outcome)
  
• choice of the biggest zone possible

Postoperative Considerations

• “off-axis” treatment of persistent complaints of diplopia or scotopic glare
  
• spectacle tint or specialized contact lens to decrease glare

Orbital Configuration and Palpebral Opening

INCOMPLETE EYELID CLOSURE Patients may have nocturnal lagophthalmos and are often unaware that they have the condition. A careful preoperative examination allows anticipation and postoperative treatment of exposure problems if necessary.

Preoperative Considerations

• inferior band staining greater in the morning
  
• visible scleral show when eyelids are gently closed

Surgical Considerations

• proper speculum selection (allows for proper positioning with minimal patient discomfort)
  
• minimal anesthesia
  
• copious lubrication

Postoperative Considerations

• exposure keratitis (occurs often but is treatable with lubricants)
  
• use of ocular lubricants
  
• punctal plugs
  
• taping of eyelid at night for first week after procedure

SMALL FISSURE SIZE Hyperopic eyes in particular are associated with small fissures. The smaller opening makes any surgical procedure more difficult because visualization is more difficult and the equipment is a standard size.

Preoperative Considerations

• appropriate measurement of fissures to assess preoperative interpalpebral opening size (for LASIK, test the fit of the suction ring in the eye)
  
• patient education about difficulty of surgery on eyes with small fissures

Surgical Considerations

• proper speculum selection to increase patient comfort
  
• keratome selection for ease of passage

Postoperative Considerations

• usually minimal postoperative visual effects

Retinal Disorders

Retinal disorders should be evaluated and treated so that they are completely stable for any elective refractive procedure.

Preoperative Considerations

• identification of retinal tears, holes, detachment, or retinal scars
  
• history of retinal detachment
  
• history of previous retinal surgery

Surgical Considerations

• absolute contraindication
  
  
  
  • visually threatening retinopathy
  
  
• relative contraindications (preoperative repair indicated)
  
  
  
  • untreated retinal breaks
    
  • retinal holes
    
  • retinal tears
  
  
• careful placement of suction ring detachment to ensure adequate suction (if previous scleral buckle for retinal detachment)

Postoperative Considerations

Doane JF, Slade SG. ALK, LASIK, and hyperopic LASIK. In: Wu H, Steiner R, Slade S, Thompson V, ed. Refractive Surgery. New York: Thieme; 1999:393-406.

Machat JJ. Preoperative myopic and hyperopic LASIK evaluation. In: Machat JJ, Slade SD, Probst LE, ed. The Art of LASIK. Thorofare, NJ: Slack Inc.; 2000:127-138.

Slade SG, Doane JF, Ruiz LA. Laser myopic keratomileusis. In: Elander R, Rich LF, Robin JB, ed. Principles and Practice of Refractive Surgery. Philadelphia: W.B. Saunders; 1997: 357-366.

Thompson VM, Wallin D. Patient selection and preoperative considerations. In: Wu H, Steiner R, Slade S, Thompson V. Refractive Surgery. New York: Thieme; 1999:41-52.