Ophthalmology – Nanophthalmos

Basics

Description

Nanophthalmos is a rare congenital developmental disorder in which the eye is globally small but otherwise relatively well formed.

Typical features include:

• Short axial length, often approximately 14.5–20 mm
• Marked hyperopia
• Shallow anterior chamber
• Crowded anterior segment
• Thick sclera
• Normal-sized or relatively large lens
• Increased lens-to-eye volume ratio
• Crowded optic disc with apparent disc elevation or pseudopapilledema
• Increased risk of angle-closure glaucoma
• Increased risk of uveal effusion and exudative retinal detachment

Unlike many forms of microphthalmia, nanophthalmos generally lacks major congenital structural malformations such as coloboma.

Epidemiology

Nanophthalmos is uncommon.

Men and women are affected approximately equally.

Risk Factors

Nanophthalmos is congenital, so there is no acquired environmental risk factor.

The major clinical risk relates to the anatomy of the small eye, particularly:

• Short axial length
• Shallow anterior chamber
• Crowded angle
• Thick sclera

These predispose to glaucoma and uveal effusion.

Genetics

Most cases are sporadic.

Familial disease can occur with:

• Autosomal dominant inheritance
• Autosomal recessive inheritance

Reported genes and loci include:

• MFRP – associated particularly with autosomal recessive nanophthalmos
• Autosomal dominant loci historically described on chromosome 11

Genetic heterogeneity is substantial.

Pathophysiology

Nanophthalmos is thought to result from abnormal or arrested ocular growth after closure of the embryonic fissure.

The eye remains disproportionately small.

Important anatomic consequences include:

• Reduced axial length
• Thickened sclera
• High lens-to-globe volume ratio
• Shallow anterior chamber
• Narrow or occludable drainage angle

Thick Sclera

The sclera is characteristically:

• Thick
• Abnormally rigid
• Histologically disorganized

This may impair normal transscleral fluid movement and vortex vein drainage.

As a result, nanophthalmic eyes are predisposed to:

• Choroidal congestion
• Choroidal detachment
• Uveal effusion
• Serous retinal detachment

Lens–Eye Disproportion

Although the globe is small, the lens is usually normal in size or relatively thick.

Therefore, the lens occupies a disproportionately large portion of the eye.

This pushes the:

• Iris
• Lens
• Iris-lens diaphragm

forward, producing a shallow anterior chamber and increasing the risk of:

Angle-closure glaucoma

Commonly Associated Ocular Conditions

Nanophthalmos may be associated with:

• High hyperopia
• Angle-closure glaucoma
• Optic disc crowding
• Optic nerve head drusen
• Retinal folds
• Macular folds
• Yellow macular pigmentation
• Macular hypoplasia
• Pigmentary retinal changes
• Retinal dystrophy
• Retinitis pigmentosa-like changes
• Acquired retinoschisis
• Uveal effusion
• Exudative retinal detachment

Systemic Associations

Most patients have isolated ocular disease.

Rare reported associations include:

• Cryptorchidism
• Hallermann–Streiff syndrome

Systemic findings should prompt consideration of a syndromic form rather than isolated nanophthalmos.

Diagnosis

Diagnosis is based on the combination of:

• Short axial length
• High hyperopia
• Shallow anterior chamber
• Thick sclera
• Crowded anterior and posterior segments

History

Typical history may include:

• Thick hyperopic spectacle lenses since childhood
• Longstanding high hyperopia
• Reduced vision from amblyopia
• Family history of glaucoma
• Intermittent headaches or ocular discomfort from angle closure
• Sudden blurred vision from acute angle closure or uveal effusion

Refractive Error

Marked hyperopia is typical.

Historical ranges include approximately:

+7 to +20 D

although severity varies.

Rare patients may be:

• Emmetropic
• Mildly myopic

because increased corneal or lenticular refractive power can partially offset the short axial length.

Amblyopia

Children with severe uncorrected hyperopia are at risk of:

• Bilateral ametropic amblyopia
• Anisometropic amblyopia
• Strabismic amblyopia

Early optical correction is therefore essential.

Slit-Lamp Examination

Typical findings include:

• Shallow anterior chamber
• Forward-positioned iris-lens diaphragm
• Crowded anterior segment
• Usually normal corneal diameter

The cornea is often near normal in size, which helps distinguish nanophthalmos from some other microphthalmic conditions.

Gonioscopy

Gonioscopy commonly demonstrates:

• Narrow angles
• Occludable angles
• Peripheral anterior synechiae in more advanced disease

Angle configuration should be reassessed periodically.

Intraocular Pressure

IOP may be:

• Normal
• Intermittently elevated
• Chronically elevated

Patients are at substantial lifetime risk of angle-closure glaucoma.

Fundus Examination

Typical posterior segment findings include:

• Crowded optic nerve head
• Apparent disc swelling or pseudopapilledema
• Optic disc drusen in some patients
• Macular folds
• Pigmentary retinal abnormalities
• Choroidal thickening
• Uveal effusion in complicated cases

Pseudopapilledema

A crowded optic disc in a very short eye can appear elevated.

This should be distinguished from true papilledema.

Helpful clues include:

• Small crowded disc
• Absence of other signs of true optic nerve edema
• Possible optic disc drusen
• Stable appearance over time

Diagnostic Testing

A-Scan Ultrasonography

A-scan is useful for measuring:

• Axial length

A short axial length strongly supports the diagnosis.

B-Scan Ultrasonography

B-scan can evaluate:

• Thickened sclerochoroidal wall
• Choroidal detachment
• Uveal effusion
• Serous retinal detachment
• Optic nerve head drusen in some cases

Ultrasound Biomicroscopy

UBM may help assess:

• Anterior chamber depth
• Ciliary body configuration
• Iris-lens relationship
• Angle crowding

This is particularly useful when mechanism of angle closure is uncertain.

OCT

Optical coherence tomography can demonstrate:

• Macular folds
• Retinoschisis
• Subretinal fluid
• Retinal architecture
• Optic nerve head crowding

Orbital MRI

MRI is usually unnecessary for straightforward nanophthalmos.

It may occasionally be useful in complex cases to evaluate:

• Globe size
• Choroidal thickening
• Choroidal detachment
• Associated orbital abnormalities

Pathology

Histologic abnormalities may include:

• Markedly thick sclera
• Abnormal collagen arrangement
• Altered extracellular matrix
• Reduced glycosaminoglycan content
• Increased fibronectin

These abnormalities contribute to poor scleral permeability.

Differential Diagnosis

Important differential diagnoses include:

• Microphthalmia
• Anterior segment microphthalmos
• Posterior microphthalmos
• High hyperopia without nanophthalmos
• Phthisis bulbi

Nanophthalmos vs Microphthalmia

Nanophthalmos

Usually:

• Globally small eye
• No major developmental structural defect
• Short axial length
• High hyperopia
• Thick sclera
• Shallow anterior chamber
• High angle-closure risk

Microphthalmia

May have:

• Small globe
• Coloboma
• Cataract
• Persistent fetal vasculature
• Retinal dysplasia
• Other congenital malformations

Nanophthalmos vs Posterior Microphthalmos

Posterior microphthalmos primarily affects the posterior segment.

Typical features include:

• Short axial length
• Relatively normal anterior chamber depth
• Less anterior segment crowding
• Papillomacular retinal fold
• High hyperopia

Nanophthalmos involves both anterior and posterior segments and has a much greater tendency toward:

• Angle closure
• Uveal effusion

Treatment

There is no treatment that increases the congenital axial length.

Management focuses on:

• Correcting refractive error
• Preventing amblyopia
• Detecting angle closure early
• Treating glaucoma
• Managing uveal effusion
• Minimizing surgical complications

Refractive Correction

Children should receive early correction of:

• Hyperopia
• Astigmatism
• Anisometropia

Options include:

• Spectacles
• Contact lenses

Early optical correction is essential to prevent amblyopia.

Amblyopia Treatment

If amblyopia develops, treatment may include:

• Full refractive correction
• Patching
• Penalization

depending on age and visual asymmetry.

Narrow Angles

Patients with narrow or occludable angles require close monitoring.

Management may include:

• Gonioscopy
• IOP monitoring
• Optic nerve assessment
• Consideration of laser peripheral iridotomy when pupillary block is an important component

Because nanophthalmic eyes are anatomically unusual, treatment should be individualized by an experienced glaucoma specialist.

Laser Peripheral Iridotomy

Laser peripheral iridotomy may help relieve a component of:

Pupillary-block angle closure

However, angle crowding may persist because of:

• Large lens relative to globe size
• Anterior ciliary body configuration
• Plateau-like anatomy

Therefore, iridotomy does not always fully open the angle.

Iridoplasty

If significant angle closure persists after a patent iridotomy and there is no major choroidal effusion, laser peripheral iridoplasty may occasionally be considered.

Glaucoma Medical Therapy

If IOP remains elevated, treatment may include standard pressure-lowering medications.

Miotics such as pilocarpine are generally used cautiously or avoided because they may:

• Relax zonules
• Allow further forward movement of the lens
• Worsen anterior chamber crowding

Lens Extraction

Lens extraction may deepen the anterior chamber and reduce angle crowding in selected patients.

However, surgery in nanophthalmos is technically difficult and carries increased risk of:

• Uveal effusion
• Choroidal detachment
• Suprachoroidal hemorrhage
• Malignant glaucoma
• Exudative retinal detachment

Therefore, intraocular surgery should be undertaken only when clearly indicated and with careful perioperative planning.

Cataract Surgery

Cataract surgery is particularly challenging because of:

• Very short axial length
• Shallow anterior chamber
• High-power IOL requirement
• Crowded anterior segment
• Increased postoperative complication risk

Accurate biometry is essential.

Modern IOL calculations should use formulas optimized for very short eyes when available.

Glaucoma Surgery

If glaucoma remains uncontrolled despite:

• Laser treatment
• Maximum tolerated medical therapy

surgery may be required.

Options include:

• Trabeculectomy
• Glaucoma drainage procedures
• Lens extraction in selected cases

Because postoperative hypotony can trigger major posterior segment complications, surgery should be performed cautiously.

Uveal Effusion

Uveal effusion may occur:

• Spontaneously
• After laser procedures
• After intraocular surgery

Possible manifestations include:

• Choroidal detachment
• Serous retinal detachment
• Vision loss

Treatment of Uveal Effusion

Management depends on severity.

Options may include:

• Observation in mild cases
• Systemic or local corticosteroids in selected inflammatory or postoperative settings
• Surgical scleral windows/sclerotomies
• Vortex vein decompression in selected severe cases

The goal of surgery is to improve transscleral drainage and reduce choroidal congestion.

Scleral Surgery

Surgical approaches may include:

• Partial-thickness sclerectomy
• Full-thickness sclerotomy
• Posterior scleral windows

These procedures are particularly useful in severe recurrent uveal effusion related to thickened sclera.

Surgical Risk

Nanophthalmic eyes are among the highest-risk eyes for intraocular surgery.

Potential perioperative complications include:

• Uveal effusion
• Choroidal detachment
• Suprachoroidal hemorrhage
• Exudative retinal detachment
• Malignant glaucoma
• Severe postoperative shallowing of the anterior chamber

Preoperative recognition of nanophthalmos is therefore critical.

Malignant Glaucoma

Nanophthalmos predisposes to aqueous misdirection, historically called malignant glaucoma.

Features include:

• Very shallow or flat anterior chamber
• Elevated IOP
• Forward displacement of the lens-iris diaphragm
• Patent peripheral iridotomy

This is an ophthalmic emergency requiring specialist management.

Issues for Referral

Referral may be required to:

• Glaucoma specialist for narrow angles or glaucoma
• Retina specialist for uveal effusion or retinal detachment
• Cataract/anterior segment surgeon for complex lens surgery
• Pediatric ophthalmologist for childhood hyperopia and amblyopia
• Medical genetics when familial disease is suspected

Ongoing Care

Follow-Up

All patients require regular ophthalmic monitoring.

Follow-up should assess:

• Visual acuity
• Refraction
• Anterior chamber depth
• Gonioscopy
• IOP
• Optic nerve
• Macula
• Signs of choroidal or retinal effusion

Patients with narrow angles or glaucoma risk may require review approximately every 3–6 months, depending on anatomy and clinical findings.

Childhood Monitoring

In children, priorities include:

• Early refractive correction
• Amblyopia prevention
• Strabismus monitoring
• Visual development

Adult Monitoring

With increasing age, patients require particular surveillance for:

• Progressive angle narrowing
• Peripheral anterior synechiae
• Glaucoma
• Cataract
• Uveal effusion

Risk becomes particularly important in middle and later adulthood.

Patient Education

Patients should understand that:

• Their eyes are anatomically smaller than normal
• High hyperopia is expected
• Angle-closure glaucoma can develop
• Intraocular surgery carries increased risk
• Sudden visual symptoms require urgent evaluation

Warning symptoms include:

• Severe ocular pain
• Headache
• Halos
• Sudden blurred vision
• Red eye
• Nausea or vomiting
• Sudden loss of vision

Prognosis

Visual prognosis can be good when:

• Refractive error is corrected early
• Amblyopia is prevented
• Glaucoma does not develop
• Uveal effusion does not occur

Prognosis becomes more guarded in patients with:

• Uncontrolled glaucoma
• Recurrent uveal effusion
• Exudative retinal detachment
• Major intraoperative or postoperative complications

Complications

Major complications include:

• Angle-closure glaucoma
• Chronic peripheral anterior synechiae
• Optic neuropathy
• Amblyopia
• Uveal effusion
• Choroidal detachment
• Exudative retinal detachment
• Malignant glaucoma
• Cataract
• Surgical complications

Ophthalmology Pearls

• Nanophthalmos = small but structurally formed eye + short axial length + high hyperopia + thick sclera + shallow anterior chamber.
• A major clue is the disproportionately large lens relative to globe size.
• The two major vision-threatening problems are angle-closure glaucoma and uveal effusion.
• Crowded optic discs may mimic papilledema, producing pseudopapilledema.
• Thick sclera interferes with normal transscleral fluid drainage and predisposes to choroidal and uveal effusion.
• Laser peripheral iridotomy may relieve pupillary block but may not completely resolve angle crowding.
• Miotics can worsen anterior segment crowding and should be used cautiously.
• Intraocular surgery carries unusually high risk of uveal effusion, malignant glaucoma, and exudative retinal detachment.
• Children need early hyperopic correction to prevent amblyopia.
• Always distinguish nanophthalmos from microphthalmia and posterior microphthalmos, because their anatomy and complications differ.